Section X.X Pilkington Greengate Energy ... - WhatDoTheyKnow

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Section X.X

Pilkington Greengate Energy Recovery Project

General RDF Gasification Requirements

ESB Generation & Wholesale Markets

Document No.: xxxxxxx-xxxx-xxxx

Date: June 2016

http://www.esbi.ie/


Pilkington RDF Gasifier 2 of 92

File Reference:

Client / Recipi-ent:

ESB Generation & Wholesale Markets

Project Title: Pilkington Power Station

Report Title: General RDF Gasification Requirements

Report No.:

Revision: 0

Prepared by: Philip LeGoy Date: 30th June 2016

Title: Senior Consultant

Verified by: Date: 30th June 2016

Title:

Approved by:

Eugene O’Keeffe Date: 30th June 2016

Title: Project Manager

Copyright © ESB International Limited

All rights reserved. No part of this work may be modified, reproduced or copied in

any form or by any means - graphic, electronic or mechanical, including

photocopying, recording, taping or used for any purpose other than its designated

purpose, without the written permission of ESB International Limited.

Template Used: T-020-007-ESBI Report Template

Change History of Report

Date New Revision Author Summary of Change

30/06/2016 0 PLG First Issue

General Gasification Requirements

Pilkington RDF Gasifier

iii

Contents 1 Introduction viii

2 General standards, codes and legislation 2

3 RDF Polishing system 3

3.1 Standards codes and legislation 3

3.2 Scope of supply 3

3.3 Description and general requirements 4

3.3.1 Design basis 4

3.3.2 Vehicle unloading systems 4

3.4 General requirements 4

3.4.1 Noise dampening 4

3.5 Special requirements 5

3.5.1 Mechanical pre-treatment 5

3.5.1.1 Standards, codes and legislation 5

3.5.2 Input weighing station 5

3.5.3 Overband magnetic separators & chutes for ferrous metals extraction5

3.5.4 Eddy current separator for non-ferrous metal extraction 6

3.5.5 Conveyors 6

3.5.5.1 Conveyor functionality 7

3.5.5.2 Belt Conveyors 8

3.5.5.3 Weighing system 9

3.5.5.4 Screw conveyors 9

3.5.5.5 Chain Conveyors 10

3.5.5.6 Bucket Conveyors/Elevators (by agreement only) 10

3.5.5.7 Walking floor conveyors 10

3.5.6 RDF charging system 11

3.5.7 RDF sampling 11

3.5.8 Collection bays and areas 11

3.5.9 Controls 11

3.5.10 Dust suppression and odour control system 12

3.5.11 Process air 12

3.5.12 Service and instrument air system 12

3.5.13 Cranes and hoists 12

3.5.14 Electrical 12

3.5.15 Maintenance 12

3.5.16 Dangerous or moving parts 13

3.5.17 Electrical 13

3.5.18 Maintenance 13

4 Gasification, combustion and boiler unit 14

4.1 Standards, codes and legislation 14


4.2.1 Furnace 17

4.2.2 Ash extractor 17

4.2.3 Boiler ash extraction 17

4.2.4 Combustion air ducts and dampers 17


Pilkington RDF Gasifier iv of 92

4.2.5 Combustion air pre-heaters 18

4.2.6 Fuel system and burners 18

4.2.7 Steam generating units 19

4.2.8 Flue gas recirculation 20

4.2.9 Selective non catalytic reduction of NOx 20

4.2.10 Boiler instrumentation and control 21

4.3 Operating conditions 22

4.3.1 Operating loads 22

4.3.2 Pressure regulation 23

4.3.3 Advanced combustion control system 23


4.4.1 Firing Diagram 23

4.4.2 Furnace 24

4.4.3 Hydraulic stations 24

4.4.4 Gasification and combustion systems 25

4.4.5 Ash extractor 26

4.4.6 Boiler hopper ash extraction 26

4.4.7 Primary air fan, secondary air fan and fan for the auxiliary burners 27

4.4.8 Combustion air ducts and dampers 27

4.4.9 Combustion air pre-heaters 27

4.4.10 Fuel systems and burners 27

4.4.11 Pressure parts 28

4.4.12 Arrangement of heating surfaces 29

4.4.12.1 Economiser 29

4.4.12.2 Evaporator with steam drum 30

4.4.12.3 Radiation and convection pass 30

4.4.12.4 Superheater and desuperheater 31

4.4.12.5 Headers 31

4.4.12.6 HP-water and steam pipes 32

4.4.13 Mountings and fittings 32

4.4.14 Metering 32

4.4.15 Thermal insulation and cladding 33

4.4.16 Access doors and observation ports 33

4.4.17 Cleaning devices 33

4.4.17.1 Mechanical rappers 34

4.4.17.2 Sootblowers 34

4.4.17.3 Protection during extended outages 34

4.4.18 Selective non catalytic reduction of NOx 35

4.4.19 Boiler instrumentation and control 35

4.4.20 Boiler house and office space heating and cooling 36

5 Bottom and boiler ash handling equipment 37




5.3.1 Electrical, control and monitoring equipment 38

5.3.2 Ventilation 38


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5.3.3 Ash conveyors 38

5.3.4 Ash store drainage scheme 39

6 Flue gas treatment system 40



6.2.1 Mechanical equipment 40

6.2.2 Electrical equipment 43

6.2.3 Instrumentation and control equipment 43


6.3.1 FGT system 44

6.3.2 Spray absorber or reaction tower (where used) 47

6.3.3 Atomiser 48

6.3.4 Fabric filter 48

6.3.5 Adsorbent supply 49

6.3.6 Silos and hoppers 50

6.3.7 Conveying equipment 51

6.3.8 Flue gas system 51

6.3.9 Induced draft fan 52

6.3.10 Control and monitoring equipment 53

6.3.11 Reliability 53

6.3.12 Basis for calculation of consumables 53

6.3.12.1 Hydrated lime 53

6.3.12.2 Activated carbon 54

6.3.12.3 Correction to design conditions 54

7 Continuous emission monitoring system 55




7.3.1 Sampling system 56

7.3.2 Instrument requirements 56

7.3.3 Local control 57

7.3.4 DCS interface 57

7.3.4.1 Data collection 58

7.3.4.2 Report Creation 58

7.3.5 Ancillary equipment 59

7.3.5.1 Gas bottles 59

7.3.5.2 Equipment cabin 59

7.3.5.3 Uninterruptible power supply 59

7.3.6 Design Life 59

7.3.7 Environmental Agency connection 59

8 Steam turbine and generator 60


8.2 Scope of works 60

8.2.1 Condensing steam turbine 60

8.2.2 Generator including auxiliary equipment 61

8.2.3 Cabling: 61


Pilkington RDF Gasifier vi of 92

8.2.4 Lubricating and control oil system 61

8.2.5 Turbine bypass station (if required) 62

8.2.6 Start-up system 62

8.2.7 Gland steam condenser 62

8.2.8 Turbine control system 62

8.2.9 Turbine hall instrumentation and control (I & C) 62


8.3.1 General operation 65

8.3.2 Arrangement 66

8.3.3 Steam turbine 66

8.3.3.1 Casing 66

8.3.3.2 Blading, nozzle segments 66

8.3.3.3 Bearings 66

8.3.3.4 Gland seals 66

8.3.3.5 Emergency stop valves, governor valves, reducing valves, non-return valves 67

8.3.3.6 Steam strainer 67

8.3.3.7 Turning device 67

8.3.3.8 Couplings 67

8.3.3.9 Gearing 67

8.3.3.10 Gland sealing steam system 68

8.3.3.11 Thermal insulation 68

8.3.3.12 Turbine cladding 68

8.3.3.13 Acoustic enclosure 68

8.3.3.14 Isolation of turbine 68

8.3.4 Instrumentation and control 68

8.3.4.1 General requirements 68

8.3.4.2 Remote measurement and monitoring systems 69

8.3.4.3 Instrumentation 69

8.3.4.4 Turbine control system 69

8.3.4.5 Turbine protection system 70

8.3.5 Reducing stations 70

8.3.6 Generator workshop tests 71

9 Air-cooled condenser 72



9.3 Operating conditions 73


9.4.1 Air-cooled condenser 73

9.4.2 Cooling air fans 74

9.4.3 Evacuation system 74

9.4.4 High pressure washing system 74

9.4.5 Condensate system 74

9.4.5.1 Condensate tank 75

9.4.5.2 Main condensate pumps 75

9.4.5.3 Turbine exhaust duct 75

10 Steam and water circuit 77



Pilkington RDF Gasifier vii of 92


10.3 Description and General Requirements 78

10.3.1 Feedwater Pumps 78

10.3.2 Feedwater tank 78

10.3.3 Feedwater tank and deaerator 79

10.3.3.1 Deaerator control 79

10.3.4 LP feedwater heaters and condensers for auxiliary systems 79

10.3.5 Design requirements 80

10.3.6 Steam and water quality monitoring and sampling 81

11 Chimney and clean flue gas duct 83




11.4 Safety showers 84

11.5 Traffic calming systems 84

11.6 Cycle and motorcycle parking 84

11.7 Heat export facility 84


Pilkington RDF Gasifier

viii

1 Introduction

Pilkington Energy Recovery Facility shall be a waste recovery facility.

R1 Recovery Operation

The plant shall be designed to generate energy from Refuse Derived Fuel (RDF) with high efficiency. It must qualify as a recovery operation as defined using the R1 Energy Efficiency formula in Annex II of the Waste Framework Directive 2008/98/EC as amended by EU Directive 2015/1127.

The Tender if winning the competition to become the Contractor shall design, deliver, install, integrate and commission, test and certify the following scope of supply for a complete 15MWe gasification, combustion, boiler and generation unit system, (Designed to meet a 50,000 hour overhaul period). The plant shall be designed to operate on RDF including an RDF receiving station with a Reception Hopper, RDF Conveyors, Circulating bed or Chain Grate Gasifier (Interior construction requires high temperature, corrosion and erosion resistance design), an ammonia injection system into Flue Gas Stream for SNCR NOx removal, hot syngas particle separators with separated hot particle conveyors (all syngas exposed interior construction of a high temperature and corrosion/errosion resistant design), ash extraction and removal from separated particles with energy recovery, air Injection Boiler to light off the hot syngas and recover energy, CO mitigation (Interior construction temperature, erosion and corrosion resistance design. Heat exchangers designed for 50,000 hours to coincide with turbine overhauls). Steam turbine and generator designed for 50,000 hours between overhauls. Flue Gas Lime and Carbon scrubber for acid gas and toxic chemical neutralization with Bag House Filter, ID Fan and Chimney the entire design shall meet all BS and EU Directives, ACE requirements, local Fire requirements, including but not limited to the Industrial Emissions Directive (IED).

There is a resource of live steam available from Pilkington Float Glass Production Line UK5 through a waste heat boiler. This live steam is approximately 6,000kg/hr at 37 bar and 300°C. An option price shall be provided by the Tenderer to allow for integration of this live steam into the system which could enhance the output of electricity. Based upon the 15MWe starting point for combustion performance the option shall cover an enhanced generation option whereby more power output is created but keeping the original combustion design.



PILKINGTON RDF GASIFIER AND POWER GENERATION

TECHNICAL SPECIFICATION



2 General standards, codes and legislation

The following standards, codes and legislation shall be applicable (where relevant) to all systems:

(1) The supply of Machinery (Safety) Regulations;

(2) The electrical Equipment Safety Regulations;

(3) Provision and Use of Work Equipment Regulations (PUWER);

(4) Pressure Equipment Regulations;

(5) BS EN 14122: Safety of machinery;

(6) BS 7671: Requirements for electrical installations. IEE wiring regulations;

(7) BS EN 953: Safety of machinery. Guards. General requirements for the design and construction of fixed and movable guards;

(8) BS EN ISO 13857: Safety of machinery. Safety distances to prevent hazard zones being reached by upper and lower limbs;

(9) BS EN 1088: Safety of machinery Interlocking devices associated with guards. Principles for design and selection;

(10) HSG60 Upper limb disorder in the workplace;

(11) Equality Act 2010; and

(12) Fluorinated Greenhouse Gases Regulations 2009.

(13) EU IED

(14) DSEAR



3 RDF Polishing system

3.1 Standards codes and legislation

R1 Recovery Operation

The plant shall be designed to generate energy from RDF with high efficiency. It must qualify as a recovery operation as defined using the R1 Energy Efficiency formula in Annex II of the Waste Framework Directive 2008/98/EC as amended by EU Directive 2015/1127.

All items under the scope of supply should conform in every way to all relevant British or equivalent European standards, codes of practice, regulations and laws applicable to RDF conveying and storage systems.

(1) BS EN 953: Safety of machinery. Guards. General requirements for the design and construction of fixed and movable guards;

(2) BS EN ISO 13857: Safety of machinery. Safety distances to prevent hazard zones being reached by upper and lower limbs;

(3) BS EN 1088: Safety of machinery Interlocking devices associated with guards. Principles for design and selection;

(4) HSG60 Upper limb disorder in the workplace;

(5) BS EN 982: Safety of machinery. Safety requirements for fluid power systems and their components. Hydraulics

(6) BS EN ISO 12100-1: Safety of machinery. Basic concepts, general principles for design. Basic terminology, methodology

(7) BS EN ISO 13849: Safety of machinery. Safety-related parts of control systems. General principles for design

(8) BS EN ISO 13850: Safety of machinery. Emergency stop. Principles for design

(9) BS EN 60204-1: Safety of Machinery: Electrical equipment of machines: General requirements

(10) BS EN 60947-2: Safety of Machinery: Low-voltage switchgear and control gear. Circuit-breakers

(11) BS EN 60947-3: Safety of Machinery: Low-voltage switchgear and control gear. Switches, disconnectors, switch-disconnectors and fuse-combination units

3.2 Scope of supply

The Contractor shall design, deliver, install, integrate and commission, test and certify the following scope of supply for the complete RDF and waste handling systems, including but not limited to systems for:

(1) unloading RDF delivery vehicles and transporting the RDF to the RDF store;

(2) unloading waste delivery vehicles and transferring the waste to the mechanical pre-treatment area;

(3) distributing the RDF to maximise utilisation of the available storage volume;

(4) mixing the RDF in storage to provide a uniform fuel mix to the thermal treatment streams;

(5) charging RDF to the fuel feed systems; and

(6) metering and feeding RDF into the thermal treatment system.

Appropriate safety systems (particularly fire and explosion safety) shall also be included.



3.3 Description and general requirements

3.3.1 Design basis

The RDF store shall have a minimum net useful capacity equivalent to 10 days of operation of the Plant at full design capacity. The net useful capacity is the difference between the maximum storage capacity of the Plant and the minimum storage level at which the RDF handling systems can still continue (indefinitely) to deliver RDF to the gasifiers to maintain operation at design throughput. Consideration needs to be given to areas of the RDF store (such as awkward corners/edges and low waste depths) where the handling equipment cannot readily access the RDF.

The fuel reception, handling and storage systems shall be proven and suitable for the handling all fuel types as described in Part A - Performance Specification.

The conveying system design shall take into account a number of design parameters, including but not limited to:

safety;

operating on a first in first out principle;

plant fuel requirements;

plant availability;

plant efficiency;

preventing spillage when unloading and transportation around site;

equipment maintenance; and

dust control and use in hazardous areas.

3.3.2 Vehicle unloading systems

The reception shall be arranged to minimise manoeuvring required by vehicles within the RDF reception hall to reduce the risk of collisions and optimise the storage capacity available. Deliveries shall be kept separate from the main RDF storage areas.

The RDF reception hall shall be designed to avoid the build up of RDF and dust in particular on beams and supports, and to minimise the release of fugitive dust to the local environment. Unloading bays shall each be within a local enclosure fitted with water misting or spray dust suppression systems, CCTV cameras and fire detection and protection systems.

RDF reception and conveying facilities installed below the level of the unloading floor shall be installed in concrete trenches with adequate access for the maintenance, servicing and removal of all items of plant and equipment.

Vehicle unloading systems shall have motorised covers which shall only open when RDF is being unloaded.

If RDF or waste delivery vehicles are required to reverse, all guides and kerbs required to ensure these vehicles are positioned correctly prior to unloading and to avoid damaging equipment shall be provided.

3.4 General requirements

3.4.1 Noise dampening

The Contractor shall provide all equipment for reducing noise. All equipment required for noise reduction shall be included. Acoustic insulation and cladding shall be provided.



3.5 Special requirements

3.5.1 Mechanical pre-treatment

3.5.1.1 Standards, codes and legislation

All items under the scope of supply shall conform in every way to the relevant and latest British and European standards, codes of practice, regulations and laws applicable to overhead cranes, including but not limited to:

[TBC]

3.5.2 Input weighing station

An electronic belt weighing station shall be attached to the primary screen feed conveyor. It shall be an idler mounted carriage unit or similar, which might be suspended from the main conveyor stringer channels. A weigh box transducer shall be provided to transmit a digital electrical signal of the conveyed product weight to a local display and the DCS or PLC system control, which will keep a historical record of the plant operation. A speed sensor shall be used to provide a digital electrical signal of conveyor speed. A combination of the two signals shall be used to calculate and record the conveyor throughput.

Table 1 - Belt weigher minimum specification

Average throughput (tph) [TBC] prelim estimate is 26tph

Design capacity (tph) [TBC] prelim estimate is 26tph + 25% CONTINGENCY = 32.5tph

Design density (kg/m3) [TBC] prelim estimate is 200 – 330kg/m

3

Weigh carriage type Suspended from main conveyor stringers

Conveyor speed sensor type Pulse Tachometer

Data Processor Type Micro-processor logging flow rate and totalised load

3.5.3 Overband magnetic separators & chutes for ferrous metals

extraction

Permanent magnet separators shall be designed to efficiently remove ferrous material from the Coarse Screenings and Oversize Screenings waste streams consisting of the characteristics defined by the Purchaser. A feeder shall be provided to ensure waste material is spread evenly across the belt. They shall be installed above the respective conveyors and provide suitable operating gaps with provision for adjustment of ±50mm.

The magnetic power source shall be strontium ferrite anistropic magnet material or similar, and shall be housed in a non-magnetic stainless steel housing. The magnetic power source shall be strontium ferrite anistropic magnet material or similar, and shall be housed in a non-magnetic stainless steel housing.



The mechanism shall incorporate a heavy duty frame supporting a robust belt supported on a two pulley system. The magnet system shall be appropriately designed to meet the performance requirements detailed in the performance guarantees and damages for failure schedule. The support structure shall be supplied with provision for position adjustment, and fully enclosed in a suitable non-ferrous metal enclosure with access panels. The unit shall incorporate a self-cleaning belt of nylon terrylene construction or similar, fitted with rubber slats to aid discharge, and the magnetic unit shall be fitted with a stainless steel rubbing plate.

The motor invertor drives shall be designed for heavy duty and for ease of maintenance and replacement. Each motor drive shall be equipped with circuit breakers, contactors and overload protection where necessary, installed and commissioned for control through a local control panel with provision for transmission of operation status to the controller. Guarding shall be provided to prevent injury from rotating components. The control system shall consist of a local control panel enclosing a PLC based system with remote activation from a central plant control unit. It shall be able to respond to local operator demands.

The Contractor shall provide for 2 years of spares, including a main belt, bearing set, motor and gearbox system.

Ferrous metals extracted from the waste by the cross belt overband magnetic separators shall be discharged, via a metal chutes, onto a conveyors for transfer to the ferrous storage areas. The chute shall be manufactured in stainless steel or other another suitable non-ferrous material.

3.5.4 Eddy current separator for non-ferrous metal extraction

After removal of ferrous metals from the coarse and oversized screenings the remaining materials shall be fed onto a non-ferrous separator via a vibrating pan feeder. The vibrating feed shall be used to ensure even distribution of material across the non-ferrous separator.

The non-ferrous separator shall be a rare-earth permanent magnet type around which a belt, of the flexiwall type, rotates. The eddy current separator shall be designed to efficiently remove non-ferrous material from a stream of incoming waste consisting of the characteristics defined by the Purchaser. The system shall be appropriately designed to meet the performance requirements detailed in the performance guarantees and damages for failure schedule.

Non-ferrous items fed into the eddy current separator together with other materials will be thrown off at a higher trajectory due to eddy current forces, and splitter plates shall be used in conjunction with a two-way discharge chute to segregate non-ferrous metals from the input feed material. A two-way chute with adjustable splitter plates shall be used to divert the segregated material onto a collection conveyor for transfer to the storage compound. Both the unit angle and speed of operation shall be able to be adjusted as required. The mechanism shall be easy to adjust to provide maximum separation performance.

The mechanism shall include a frame and housing incorporating a heavy duty ceramic pulley shell and belts fitted with suitable wipers and side skirts.

A feeder shall be provide to ensure waste material is spread evenly across the belt.

Appropriate emergency stop devices shall be installed to reduce the risk of injury.

Each motor invertor drive shall be equipped with circuit breakers, contactors and overload protection where necessary, installed and commissioned for control through a local control panel. Guarding shall be provided to prevent injury from rotating components. The control system shall consist of a local control panel enclosing a PLC based system with remote activation from a central plant control unit. It shall be able to respond to local operator demands.

Where required cooling fans shall be provided to prevent issues associated with high temperature environments.

3.5.5 Conveyors

The Contractor shall select a suitable conveyor system based on a proven design for transport of the specified fuel. Any conveyors provided shall be in accordance with Part C – General mechanical and electrical specification.



3.5.5.1 Conveyor functionality

Where possible, belt conveyors shall be used in preference to chain conveyors or screw conveyors. Bucket elevators shall not be used without the agreement of the Project Manager.

Conveyors, especially those with no redundancy, shall be of high availability type and laid out to enable condition checks and ease of maintenance. The main fuel transfer conveyors from the fuel store to the boiler dosing bins shall be proven to have high availability and reference facilities shall be made available to the Purchaser to demonstrate this. Variable speed drives shall be used for energy efficiency where possible.

Conveyors shall have local controls for forward and reverse movement and inching controls to assist in maintenance.

Gearboxes shall be used as appropriate and shall be compliant with the full requirements of the Specification. Motor protection shall be provided and motors shall be sized with a minimum duty of nominally 110% of the maximum anticipated load conditions. A rotational sensing unit shall be attached to the tail shaft to prove conveyor movement and provide positive feedback to the DCS.

Conveyors shall be totally enclosed for dust suppression. Access covers shall be installed as necessary around the drive unit and along accessible sides of the conveyor for easy access and inspection. Guards shall be fitted as necessary around the drive units and along accessible sides of the conveyor.

Access platforms, gangways and ladders shall be provided as necessary to enable maintenance activities to take place. Emergency stops shall be provided adjacent to all access points and at regular intervals along open conveyors, using push button and pull cord stops as appropriate.

Fire detection and protection including a spray system shall be provided along conveyors between the reception facility and boiler dosing bins.

All parts shall be designed to ensure safe, reliable and economical operation at the maximum throughput rate. Parts shall be designed so that they may be easily assembled, adjusted and accessible for inspection and maintenance. The equipment will be installed and used where dust is prevalent and will be required to operate continuously. All motor ratings shall be designed to start loaded conveyors for the cold weather conditions listed.

The conveyors shall be designed to stop and start under full load, i.e., when loaded with RDF along the entire length.

All facilities shall be designed for ease of maintenance and cleaning.

All designs shall aim toward eliminating potential material hang-ups, bridging and spillage.

Instruments and controls shall be in accordance with the control system requirements of this specification.

Parts subject to wear from abrasive contaminants, including anti-friction bearings, shall be pre-packed lubricated and effectively sealed against the ingress of moisture and contaminants.

Where belts are inclined the design shall ensure that the angle of inclination does not allow fuel material to cascade down the belt during operation or when stationary.

The material of the belt shall be designed for robustness with suitable wear and corrosion resistance for the designated lifetime. The material of the conveyor in the area of metal separation shall be of the non-magnetised type.

The designs shall incorporate suitable emergency stop (push button and grab wire designs within easy reach of potential danger points, i.e. both sides of a conveyor system) and lock-off mechanisms at accessible points for operators.

Guarding shall be provided in all areas of rotating machinery, pinch points, beneath conveyor belts or where the potential for injury is present. Interlocks shall be provided where the safety of personal removing guarding cannot be guaranteed.

Safety features such as sirens and signboards shall be provided for conveyors which can be started automatically to warn personnel of their automatic starting.

All transfer points from and to conveyors must be equipped with a suitable method of eliminating spillages and minimising the production of dust. Such methods include but are not limited to side guards, transfer chutes and fully enclosing the transfer point.



All conveyors and other rotating or moving mechanisms located above personnel walking surface (i.e. gantries or floor level) shall include suitable guards to protect workers from the moving parts and debris falling from the underside of the conveyor.

All steps and uneven surfaces for access shall be clearly marked.

Access panels to remove debris shall be easily accessible and allow enough room to clear any potential blockage. Access panels and guarding (if removable to clear blockages) shall be interlocked to the local control board. Local control boards shall provide have forward / reverse and inching controls for conveyors.

Conveyor motors should, where possible, be of a consistent type.

3.5.5.2 Belt Conveyors

A belt conveyor shall be the preferred option for fuel transportation and should be used wherever practical.

Belt conveyors shall, wherever practical, operate with variable speed drives to minimise losses.

The design of the belt conveyor shall have been proven in similarly-sized applications transporting similar fuel.

As a general principle conveyors shall be designed to minimise dust release using features including:

• minimising conveyor and material velocities; and

• extraction of dust at key locations where necessary.

The belt conveyor shall be designed with suitably robust stringers, structural support members, belts, deck plates, gravity take-up systems, bearings, couplings and motors designed to support static, dynamic, vibration, fatigue and impact loads from handling RDF for the duration of the Plant life.

Where material is transferred from one belt to another the system shall be designed to include a fully covered skirt plate system to prevent RDF falling uncontrolled from the conveyors and to minimise dust emissions. The impact from clumps of frozen RDF shall also be taken into account. Dust extraction shall be included at these transfer locations.

Where feeding chutes are mounted, the design shall include steel plate with adequate thickness to avoid impact damage during the life of the Plant. Robust inspection (minimum 300 x 300 mm) and access doors (minimum 600 x 600 mm) provided to enable access shall be designed to prevent dust emissions.

Cover plates of the inlet chute shall be extended over the receiving chute to prevent the occurrence of fuel blockages.

Conveyor belt motors shall be designed with variable frequency drive systems to enable soft start motion and variable speed control.

The design of the conveyor system shall take into account the angle of travel and be proven on similarly-angled conveyor systems already in operation which demonstrate avoidance of waste falling back down the conveyor. All conveyors shall be fitted with anti run-back devices and low speed holdbacks shall be provided on inclined conveyors, where the holdback torque rating shall exceed the stall torque or 150% of the conveyor’s reverse torque, which is the greater.

Suitable sensors shall be provided for the motor and gearbox condition monitoring (including vibration monitoring) and temperature monitoring for bearings.

The design of conveyor belt capacity shall be based on meeting full duty capacity at the defined conveyor belt velocity not exceeding 1.5 m/s and 90% of the conveyor section using the lowest density fuel combination expected to be used. The design shall be capable of starting empty or fully loaded, 4 times/hour over the life of the Plant.

The angle of inclination of belt conveyors shall not exceed 15 degrees from the horizontal, unless the Contractor is able to demonstrate the suitability of a steeper inclination, to the satisfaction of the Project Manager.



The belts shall be designed to be flame retardant and weatherproof for the life of the Plant, based on the Contractor’s previous experience of using conveyor belts transferring wood pellets with varying characteristics and potential for smouldering. A system designed to ease cleaning the belt surface shall be included.

The design of the conveyor mechanism shall be designed to facilitate repair of most failures (such as motor replacement, liner replacement or mechanical belt failure) and return to full operation within a 24-hour period.

Along the length of the conveyor system, guttering shall be provided to remove rainwater and direct it to a suitable drainage system.

Splitters and diverters shall be designed for a Plant Life of 10 years, taking into account the varying characteristics of waste fuel, including impact forces from frozen waste clumps. The design shall be designed to minimise dust emissions with air-tight casings and enclosed flap and diverter mechanisms. Suitable ATEX-rated maintenance access to maintain the splitters, diverters and associated actuation systems shall be provided.

Conveyor brakes shall not be used, unless the Contractor is able to demonstrate the benefit of a brake system over and above other methods to stop the conveyor.

3.5.5.3 Weighing system

A weighing system shall be provided to and allow the RDF NCV into the combustion chambers to be calculated to an accuracy of 2.5% using the boiler as a calorimeter. Data from the weighing device shall be transmitted to the distributed control system (DCS).

If belt weighers are provide, they shall be designed and calibrated to achieve an in service accuracy of 0.5%. The installation shall be calibrated and supplied complete with all calibrated weights and other tools required for operation. Calibration shall be in accordance with International recommendation titled ‘Continuous totalizing automatic weighing instruments (belt weighers). Part 1: Metrological and technical requirements – Tests. OIML R 50-1 Edition 1997 (E)’. It shall be possible to bypass belt weighers during periods of maintenance.

3.5.5.4 Screw conveyors

If screw conveyors are supplied, as a standalone unit or as part of a system, these shall be of a proven type used in similar applications with similar fuels. The design shall account for the maximum fuel particle size.

To ensure the continuity of the material flow, the screw speed shall be limited and the unit shall be provided with a means of speed adjustment. The screw speed will be optimised for the bulk density of the material.

Where used with a casing, the casing can be either be a U-Trough or pipe construction, provided that the design has no stagnation points or pockets where the waste material can gather and potentially block the material flow. Access doors shall be installed to aid inspections and maintenance.

The screw blade shall be a non-clog type without stagnation pockets, the design of which shall be suited to the material and throughput requirements. The shaft will be provided with suitable bearings and designed and constructed to ensure no sag.

Material thickness and selection shall make provisions for wear due to abrasion, contact with wet waste, and may include wear plates. The unit shall be designed to meet the Design Life requirements. The clearance between the screw and the casing shall be selected by the Contractor based on previous experience with similar waste fuels.

The unit shall be installed and aligned to ensure that the operation of the screw is smooth and vibration free.

The conveying unit is to be fitted with adjustable over-torque protection to protect the motor against screw jams.

The coupling between the motor and the screw will be a flexible mechanical type.



The use of water spray systems or similar shall be provided to reduce the potential for overheating and fire.

3.5.5.5 Chain Conveyors

If chain conveyors are provided, these shall be of a proven type used in similar applications with similar fuel. To ensure the continuity of the material flow, the conveyor speed shall be limited and the unit shall be provided with a means of speed adjustment.

The conveyor shall be designed with two parallel chains. The design shall be such as to avoid problems caused by long thin objects passing into the conveyor through the fuel screen jamming the chains.

Material thickness and selection shall make provisions for wear due to abrasion, and may include wear plates. The unit shall be designed to meet the design life requirements. It shall be possible to easily inspect the conveyor to detect wear on the plates or ageing of the chains.

The unit shall be installed and aligned to ensure that the operation of the conveyor is smooth and with low noise.

The conveying unit is to be fitted with adjustable over-torque protection to protect the motor against jams.


3.5.5.6 Bucket Conveyors/Elevators (by agreement only)

If bucket elevators and or conveyors are agreed to be provided, these shall be of a proven type used in similar applications with similar fuel. To ensure the continuity of the material flow, the conveyor speed shall be limited and the unit shall be provided with a means of speed adjustment.

The design shall be such as to avoid problems caused by long thin objects passing into the conveyor through the fuel screen jamming the equipment.

Material thickness and selection shall make provisions for wear due to abrasion, and may include wear plates. The unit shall be designed to meet the design life requirements. It shall be possible to easily inspect the conveyor to detect wear on the plates or ageing of the chains.

The unit shall be installed and aligned to ensure that the operation of the conveyor is smooth and with low noise.

The conveying unit is to be fitted with adjustable over-torque protection to protect the motor against jams.


3.5.5.7 Walking floor conveyors

If walking floors are used, they shall be suitable for loading from a frontloaded shovel or other handling systems. The walking floor and supporting structure shall be designed to withstand the forces acting on it during loading operations. The walking floors shall be capable of continuous and unattended operation, where the operator may load the intermediate storage area and then allow the walking floor to operate unmanned until the intermediate store requires filling.

The walking floors shall be designed to minimise spills and the release or build-up of dust.

Each walking floor part shall consist of a number of pusher frames. There shall be sufficient access to each of the hydraulic pistons for each pusher frame to allow external maintenance, removal and installation. The pistons and hydraulic system shall be arranged such that pistons can be maintained without the shutting down of the walking floor.

The hydraulic system shall be fitted with safety systems to prevent jamming or damage due to excessive force being exerted.

The pusher frames shall be of a hard wearing steel that is resistant to abrasion and corrosion.



3.5.6 RDF charging system

There shall be redundancy in the RDF screw feeder system to the furnace. In the event of a fault on a screw feeder, the remaining feeders shall provide sufficient throughput to sustain the gasification process, boiler and turbine at normal operating conditions.

RDF feeders shall have a proven shape and shall allow the fuel to flow freely without risk of build-up and bridging. The walls around screw conveyors or rotary valves shall be constructed of steel plates and reinforced with wear plates made from Hardox or similar wear resistant material. All welds shall be designed to take into account the specific material requirements.

A system shall be provided to close the charging screws against air infiltration through the dosing bin. An alarm shall be given if the level of RDF within a dosing bin drops below the prescribed minimum level for safe normal operation.

Each dosing bin shall include steel sheet casing and with fill in nozzles for the RDF and installed with an entrance door and sight hole and level monitoring by continuous radar or two microwave or other suitable binary measurements monitors for control of the RDF in the bin linked to the boiler management system.

Each dosing bin and associated conveyors shall include a sprinkler system with appropriate temperature sensors for protection against the risk of fires and over heating.

3.5.7 RDF sampling

Sampling of the RDF supplied to the Plant shall be undertaken in accordance with the requirements of OFGEM for reporting purposes and any other statutory requirements.

The sampling system shall be capable of sampling RDF with extremes of characteristics using a common primary sampler compliant with CEN 14778:2011 regarding solid biofuel sampling, and with the agreement of the Project Manager.

The sampling system shall be designed to automatically and accurately sample the RDF to the required tolerance irrespective of the impact of varying dust control and environmental humidity levels. Surplus fuel shall be diverted back to the main fuel supply.

The system shall be programmed to sense when a sample is required, fill the sample bin, detect when the bin is full and also if a sample fails to meet the correct fill criteria. Sample blockages shall also be indicated.

Sampling feedback shall be provided to the DCS with indications of system failure.

The sampling process shall be automatic with local panel provision for personnel to view the sampling operation, undertake diagnostic evaluation of the system using suitable mimic screens and switch to manual control of the sampling process.

There shall be suitable provisions for manual sampling of RDF in the event that the automatic sampling system is not available.

3.5.8 Collection bays and areas

The Purchaser shall provide within the following storage and collection compounds:

(1) ferrous metal compound to store the ferrous metal bales;

(2) non-ferrous metal compound to store the non-ferrous metal bales; and

(3) reject waste compound.

The storage bays shall be designed with a recessed loading bay to enable articulated vehicles to be loaded effectively from ground level using a shovel or front bucket loader.

3.5.9 Controls

All controls placed on an item of plant shall be placed in suitable positions where the operative in charge of staring the equipment can best control the actions of the equipment.



All controls shall be clearly and properly identifiable to ensure the person activating them know their function and how to activate them.

Emergency stops are not to be used as a sole method of controlling a process at the expense of installed automatic shut-down systems.

There shall be only one emergency stop system fitted to the item of plant. Emergency stops shall be located within easy reach of any area where an operative is operating or maintaining the plant.

All control systems on items of static plant shall have additional lock off provisions near to the item of plant and in vision of the operative operating or maintaining the plant. The lock-off provision shall allow for a multi-hasp lock to be placed in position by the operative or fitter prior to any removal of a critical guard or work that shall be carried out beyond safe guards fitted.

3.5.10 Dust suppression and odour control system

A dust suppression and air cleaning system shall be provided to keep down dust and remove other airborne particles. This system shall be supplied as part of the MRF plant and shall be a stand-alone system. This system shall be connected into the respective equipment dust hoods, conveyor covers, etc., and service the mechanical pre-treatment area. The dust suppression system shall be by means of a wet collector type unit, complete with chemical dosing. The contractor shall size the dust extraction system to suit the specific requirements for the mechanical pre-treatment plant.

The odour control system shall be an activated carbon (PAC) or sodium bicarbonate atmospheric dosing type system or similar, designed to remove ammonia, hydrogen sulphide and other odorous substances. Contractors may offer a wet scrubber type system as an alternative, if they perceive it will provide economic or performance benefits.

3.5.11 Process air

All process air requirements shall be included.

3.5.12 Service and instrument air system

All service and instrument air shall be included.

3.5.13 Cranes and hoists

Provision shall be made for all necessary maintenance area to enable equipment to be lifted out of position and lowered to a suitable vehicle access point at ground level using mobile lifting equipment.

3.5.14 Electrical

All necessary electrical power outlets, power supply connections, cabling, transformers, protection and metering equipment, and switchgear shall be provided for the mechanical pre-treatment plant as required.

3.5.15 Maintenance

All machinery shall be designed and installed in such a way that regular cleaning and maintenance can be carried out without undue risk to the person carrying out the task provided the task is performed in accordance with the operating and maintenance instructions.

For maintenance tasks that require the removal of guards that prevent contact with sharp, hot/cold or moving parts, the removal of the guard shall be possible without making contact with any of the dangerous parts.



It is preferred that where contact with moving parts that can trap or cause cuts to operatives, such guards shall be fitted with interlocks to cut the power to the drive.

Where interlocks are not fitted, guarding shall be fixed by bolts or similar fixing devices. They shall not be fixed or operate by any toggle clamp or similar fixing devices.

3.5.16 Dangerous or moving parts

Within the boundaries of reasonableness, all moving parts that can trap, cut, burn or injure in any other way persons likely to be present when it is in use, shall be guarded.

Such guards shall be designed to ensure persons cannot place any part of their body or clothing into the path of the moving part whether accidentally or misguidedly.

All equipment shall be guarded to meet UK legislation.

3.5.17 Electrical

All electrical enclosures and terminal boxes shall be IP65.

A separate switchable supply shall be supplied for the auxiliary equipment.

2 x 110 V supplies shall be supplied on the primary bridge and 1 x 110 V on the secondary bridge.

3.5.18 Maintenance

The cranes and grabs shall be designed for maintenance servicing.

Safety harness anchors shall be provided on the crane for maintenance purposes.

The Contractor shall ensure it is possible to scaffold up to the crane from floor level to carry out maintenance underneath the crane.

There shall be a safe access arrangement so that it is not possible to gain access whilst the cranes are energised.



4 Gasification, combustion and boiler unit

4.1 Standards, codes and legislation

All items under the scope of supply should conform in every way to the relevant British and European standards, codes of practice, regulations and laws applicable to combustion and boiler units, including but not limited to:

BS EN 12952: Water tube boilers and auxiliary installations. The Contractor shall state whether his/her boiler is designed “by rule” or “by analysis”

BS EN 12952-15: Water-tube boilers and auxiliary installations. Acceptance tests

BS EN 13480: Metallic industrial piping

BS EN ISO 4126-1: Safety devices for protection against excessive pressure. Safety valves

BS 2869: Fuel oils for agricultural, domestic and industrial engines and boilers - specification

NFPA 68: Explosion protection by deflagration venting, NFPA 69: Standard on Explosion Prevention Systems, NFPA 85: Boiler and Combustion Systems Hazards Code

Equipment and Protective Systems Intended for Use in Potentially Explosive Atmospheres Regulations (1996)

The Dangerous Substances and Explosive Atmospheres Regulations (2002)

The Pressure Equipment Regulations (1999)

The Pressure Systems Safety Regulations (2000)

4.2 Scope of supply

The Contractor shall design, deliver, install, integrate and commission, test and certify the following scope of supply for a complete 15MWe gasification combustion and boiler unit system, designed for 50khrs to overhaul of internal parts (see Figure 1 below):

1. RDF Reception Hopper 2. RDF Conveyors 3. Fluidized bed Gasifiers (Interior construction requires high temperature resistance design), i.e.

Bubbling bed Gasifier, Circulating Fluidized bed Gasifier, Two stage Fluidized bed Gasifier, etc. 4. An ammonia injection system into Flue Gas Stream at 850C to 950C for SNCR NOx removal 5. Hot Syngas and Particle Separators with Separated Particle conveyors (Interior construction high

temperature resistance design) 6. Pyrolosis ash removal – if supplied 7. Ash extraction and removal from Separated Particles with energy recovery 8. Air Injection (primary air and secondary air as required) to Boiler to light off the hot gases and re-

cover energy (Interior construction temperature & corrosion resistance design. Heat exchangers in the boiler designed for 50k operating hours.)

9. Steam turbine and generator (allow for 4 to 8MWth waste heat steam from glass mfg) 10. Flue Gas Lime and Carbon scrubber 11. Bag House Filter 12. ID Fan and FGR Fan 13. Chimney 14. Acid sorbant silo with 10 day volume 15. Activated Carbon silo with 10 day volume 16. Fly ash silo with 10 day volume 17. Pyrolosis residue silo with 10 day volume 18. Gas sampling ports for singas sampling 19. Gas sampling ports for flue gas sampling

20. Chimney sampling ports and sampling platform designed as per STA M2 for flue gas measurements. Chimney sampling platform shall contain equipment lifting beams and shall include 400V, 240V & 110V sockets and switchable lighting for personnel working on these platforms at night.



RDF Receiving Hopper

Bubbling Bed Gasifier

RDF Conveyor

Ammonia Injection For NOx Removal

Hot

Particle Separation

Fly Ash

Bottom Ash

Air Injection Boiler with required Draft Fans

Gasification

Device

Hot Fuel Gasses

Combustion Air

Hot Fuel Gasses

High Temperature Resistant Furnace Material

High Temperature Resistant Boiler Material

Steam Turbine and Generator

Generated Power Out

Lime and Carbon

Injection Scrubber

Bag House Filter

Fly Ash

ID Fan

Chimney

Clean Exhaust Gases

Steam From Waste Heat Boiler

on UK5 Production Line

Figure 1 Combustion Process Flow Diagram



Figure 2 Site Layout

4.2.1 Furnace

The furnace system shall include but not be limited to:

(1) 2 or 3 large access doors on the end of the grate (if proposed) which with or without a grate is required and shall allow access for maintenance (i.e. cables and flexible tubes into the furnace) and shown on relevant drawings to demonstrate access to the grate;

(2) 2 or 3 large access doors to access cleaning as required around any circulating bed (including bubbling bed) gasification system if proposed.

(3) openings for monitoring and control equipment and including personnel and equipment protected manual inspection ports;

(4) water-cooled or air-cooled (if not inserted inside the furnace) CCTV cameras, scanners/sensors and sample probes;

(5) access openings for water cooled sampling probes to aid in the detection of temperature, NOx and CO distribution problems within the combustion chamber;

(6) openings for installation of selective non-catalytic reduction (SNCR) at multiple levels to facilitate optimisation of reagent injection; and

(7) openings on opposite sides of boiler to allow manual traverse with water-cooled aspirating pyrometer and gas sampling probe on at least three horizontal planes within the first radiant pass, at least one plane in the subsequent vertical radiant passes and at least one vertical plane between convective heat transfer bundles (there need to be sufficient openings within each plane to enable the gas and temperature distribution across the plane to be plotted and to determine compliance with the Environment Agency EPR 5.01 guidance document).

(8) Refractory to compensate for furnace heat and protect exposed components from corrosive/erosive wear.

4.2.2 Ash extractor

The ash handling system shall include but not be limited to:

(1) a wet ash extraction system with wear plates;

(2) vibrating or other screen stations for separation of oversize material;

(3) vibrating conveyor or belt conveyor, if required, to transfer ash to main bottom ash conveyors or to bulk storage;

(4) scrap feeder trough;

(5) common scrap conveyors;

(6) scrap discharge conveyors;

(7) riddlings conveyor;

(8) chutes and all accessories;

(9) enclosure (protection against vapour, vibration and noise) of ash extractor and ash transport equipment including ventilation system with extraction of gases to the secondary combustion air system; and

(10) necessary equipment for water supply where the ash quench system must operate without a continuous water discharge.

4.2.3 Boiler ash extraction

The boiler ash extraction shall include but not be limited to:

(1) extraction rotary valves;

(2) conveyor mechanism to convey the boiler ash to the bottom ash discharge system; and

(3) expansion compensating devices.

4.2.4 Combustion air ducts and dampers

The combustion air system shall include but not be limited to:

(1) a primary air fan with motor, variable frequency speed regulation, coupling and base frame for fan and motor;

(2) secondary air fan with motor, variable frequency speed regulation, coupling and base frame for fan and motor;

(3) complete fan system for auxiliary firing system;

(4) complete fan system for cooling and ignition air (if necessary);

(5) complete sealing air fan system (if necessary);

(6) handling and lifting devices above the fan drives to aid maintenance;

(7) a spare fan drive for the primary fan and the secondary fan;

(8) all necessary isolation measures against noise and vibrations, including silencers;

(9) air ducts with stiffeners and substructure, dampers, pneumatic actuators for dampers, expansion joints, access doors and venturi flow nozzles, etc., to contain as a minimum:

(10) primary air intake duct from above the RDF storage area including easily cleaned guard screen and fire protection for the RDF storage wall penetration;

(11) primary air duct between primary air fan and air pre-heater with total air quantity measurement and a manual control damper in each line;

(12) primary air distribution system (separate air quantity measuring and air control dampers for each grate section and/or for furnace bubbling bed requirements);

(13) secondary air intake duct from the boiler house at high level to the air pre-heater and to the fan;

(14) secondary air duct between secondary air fan and furnace with total air quantity measurement and a manual control damper in each line;

(15) air-side by-pass of air pre-heaters;

(16) air ducts from the ash quench bath to the furnace;

(17) air ducts for auxiliary firing system;

(18) air ducts for cooling, ignition and sealing air, if necessary;

(19) nozzles for secondary air; and

(20) facilities for the measurement of flue gas temperatures for the purpose of proving the two-second residence time in accordance with OFGEM requirements.

4.2.5 Combustion air pre-heaters

The combustion air pre-heater shall include but not be limited to:

(1) a pre-heater for primary air including condensate cooling section;

(2) a pre-heater for secondary air including condensate cooling section; and

(3) if steam/water the inclusion of a drain control system and condensate return pump(s) connected to drains;

4.2.6 Fuel system and burners

An auxiliary start-up and auxiliary firing system incorporating a fuel system and burners shall be provided for combustion chamber start up and to ensure combustion temperatures meet or exceed the requirements of the Industrial Emissions Directive. The auxiliary fuel systems shall include but not be limited to:

(1) a minimum of two auxiliary burners in each furnace, to heat the furnace for start up and shut-down, to ignite the RDF and to maintain the minimum flue gas temperature in operation with a heating capacity equivalent to the minimum turn-down level;

(2) duty and standby fuel valve stations for each burner;

(3) ignition system for each burner;

(4) complete control and safety equipment including interfaces to the DCS for all principle signals (firing rate, burner status);

(5) gates for the protection of the burners which are out of operation, if retractable units are proposed;

(6) means of measurement and adjustment of fuel and air over the full firing range of the burner;

(7) means of isolating the burners from flue gases when the burners are not firing (if retractable units are proposed), or cooled by a continuous air supply (if the units are not retractable) and also after shut-down when it is not possible to use cooling air due to the isolation of the flue gas treatment system;

(8) all associated piping, valves and pressure regulating equipment or pressure control as may be necessary for this application;

(9) a piping ring main to supply each combustion chamber;

(10) individual metering of the auxiliary fuel to the boiler; and

(11) bunded area or tray beneath each burner to capture oil spillages (if applicable).

4.2.7 Steam generating units

Each steam generating unit shall include but not be limited to:

(1) evaporators screens;

(2) superheaters;

(3) evaporators;

(4) economisers;

(5) spray type attemperators including actuator and handwheel;

(6) pre-heater in the drum to maintain the feedwater inlet temperature to the economiser (if necessary);

(7) boiler mountings, valves and accessories as required for safe unsupervised operation, including, but not limited to:

a) all necessary drain, vent and blowdown pipes including valves concentrated at valve groups (double block valve);

b) feedwater shut-off valve and feedwater control valve with actuator, check valve including locally and remotely operated control valve as bypass;

c) automatic condensate traps and/or drain valves with bypass and stop valves;

d) automatic blowdown system equipped with TDS monitoring and control, flash steam recovery and sensible heat recovery to the incoming make-up water;

(8) complete drum blowdown control valve group;

(9) complete drum level gauges and instruments including “2 out of 3” level transmission. Level instrumentation shall have at least 2 independent connection to the drum;

(10) Hydrastep or equal drum level indicator mounted in the Plant control room;

(11) drum emergency drain valve with actuator;

(12) local and remote water level indicator;

(13) all necessary safety valves to protect all pressure parts and to meet safety and statutory requirements, including silencers and rain hoods, where the Contractor shall include in his design a common steam line controlled relief vent for protection against loss of vacuum at the ACC such that the turbine and turbine bypass would be unable to operate;

(14) start-up control valve, and stop valve, each with actuator;

(15) live steam stop gate valve with actuator;

(16) sampling system for boiler water and live steam with sampling coolers;

(17) connections for chemical dosing to feedwater including all chemical dosing pumps, equipment and controls;

(18) 2 instrument ports on each side for traverse of at least 70% of flue gas duct prior to first superheater section for confirmation of flue gas temperature into the superheater;

(19) necessary maintenance access doors and inspection viewing ports, including a maintenance door to access the boiler at high level in case of formation of ash deposits which would make access into the boiler beneath unsafe without first removing potential falling material;

(20) furnace inspection/supervisory equipment, including erection doors for inspection in the upper part of the radiation passes and between the convection passes;

(21) additional access ports at two levels within the furnace chamber to provide access for instrument traverses for the purposes of demonstrating IED compliance and optimisation of the combustion and SNCR performance;

(22) insulation and casings;

(23) equipment for preserving the boiler during periods of non-operation;

(24) equipment to provide recirculation of water between hot and cold boilers, in order to shorten the required start-up period of the cold boiler;

(25) drain and condensate flash tank, including a:

a) pressurised flash tank for blowdown steam recovery;

b) atmospheric flash tank including silencer and necessary equipment;

c) blowdown heat recovery system;

d) condensate tank with normal and emergency drain adjustment, complete with pumps, cooling system and control valves;

(26) heating surface cleaning system, including a:

a) pneumatic or electric/mechanical rapper equipment for the convection heating surfaces in the horizontal boiler passes;

b) water spray-type cleaning system in vertical passes;

c) soot removal systems in vertical economiser sections;

(27) boiler ash removal, including a:

a) air seal discharge system;

b) sieve equipment and crusher for the boiler ash (if necessary);

c) collection conveyors for the boiler ash from all passes to transfer to the bottom ash collection and transfer system;

d) appropriately designed and sized rodding system to unblock ash blockages, with adequate guarding; and

e) vertical and horizontal space allocation within layout for future pneumatic conveyor of boiler ash to separate collection system (to allow for possible changes in the classification of boiler ash);

(28) bottom ash water seal, ash extraction, screening, ferrous metals separation and conveying system;

(29) boiler steel structure, platforms and stairs, including the:

a) boiler steel structure;

b) steel staircases from basement level to the boiler house roof;

c) all necessary staircase, ladders, platforms from basement level to the boiler house roof including structural steel engineering, open floor grating and balustrade; and

d) supporting steel structure;

(30) boiler blowdown systems including blowdown receivers and continuous blowdown heat recovery systems; and

(31) measures (such as soot blowing, mechanical rapping) for cleaning of the boiler.

4.2.8 Flue gas recirculation

Where flue gas recirculation is included, the Contractor shall provide a complete system for each boiler, consisting of recirculation fan, nozzles and all necessary ducts, dampers and accessories. Cold spot corrosion in all phases of operation of the system shall be prevented with adequate insulation, trace heating and use of corrosion resistant materials of construction as appropriate. Consideration shall be given to the avoidance of corrosion in the system by suitable pre-heating, start-up and shut-down procedures.

The flue gas shall preferably be re-circulated from the clean side of the bag filter.

All ducts including flanged joints shall be gas-tight welded from the inside.

The flue gas recirculation system shall be furnished with an air purge system for start-up and for downtime of the recycled flue gas system.

4.2.9 Selective non catalytic reduction of NOx

The Contractor shall supply a complete SNCR installation(s) to achieve the NOx emission limit including but not limited to:

(1) Urea or ammonium hydroxide solution reception facilities from road vehicle/tanker, taking into account all relevant regulatory requirements relating to the handling, storage and supply of hazardous chemicals to the process, and ensuring that the Plant does not exceed the thresholds associated with COMAH lower tier installations;

(2) storage tanks with bunded containment for a minimum five days storage or three day plus the delivered vehicle/tanker volume, whichever is greater;

(3) duty/standby pumps each of sufficient capacity to supply 110% of the maximum urea/ammonia flow with the boilers operating at MCR;

(4) distribution system including all piping, control valves and fittings, with piping supplied with adequate facilities for priming, flushing and draining the system;

(5) a complete set of nozzles for injection into the furnace;

(6) equipment to provide atomising media including all piping and fittings;

(7) all necessary safety precautions and equipment required; and

(8) control facilities to provide NOx control and to optimise reagent consumption.

4.2.10 Boiler instrumentation and control

The boiler instrumentation and control (I&C) system shall include but not be limited to:

(1) control system, using standard DCS system;

(2) software and Documentation, including functional diagrams and narrative description of all control protection and interlock systems;

(3) all tapping points and connectors for remote measurements as well as for acceptance and test measurements, including primary isolation for instrument lines;

(4) all instrumentation, transmitters, limit switches etc.;

(5) any power supplies necessary for instruments or control devices;

(6) complete installation for all instrumentation and control devices, including wiring to the control system, piping where required including connection to the Plant compressed air system, all required attachments, electrical and mechanical isolation where required, conduits, junction boxes, brackets and other supports, including cable racks;

(7) systems for sampling and measurement of bio-energy content of the RDF for the purposes of claiming ROCs;

(8) syngas sampling and monitoring systems for demonstrating the syngas GCV in accordance with the requirements of OFGEM for the purposes of claiming ROCs;

(9) continuous monitoring of the flue gas temperature prior to the convective superheater section to ensure compliance within acceptable limits;

(10) continuous monitoring of temperature at exit from secondary combustion chamber to demonstrate compliance with IED requirements for temperature and residence time of products of combustion;

(11) flue gas monitoring system at boiler exit to measure as a minimum O2, CO, chlorine, NOx and sulphur [TBC] for control of combustion and flue gas treatment systems, including all instrumentation, conditioning, piping, cabling and associated equipment;

(12) all necessary control dampers or butterfly valves in the air and flue gas ducts with actuators;

(13) control valves with actuators;

(14) orifice plates;

(15) in-line instruments;

(16) on-line measuring equipment sufficient to calculate and record continuous mass and energy balance for the boiler and therefore to derive the NCV of the RDF including but not limited to:

a) venturi meters for all air and flue gas flow measurements, complete with primary isolation;

b) flow measurements ;

c) thermocouples to determine heat input to the air pre-heaters;

d) thermocouples to monitor water / steam in each pressure circuit;

e) RDF feed rate from RDF metering systems, with the total RDF throughput level presented to enable manual verification against weighbridge data; and

f) calculation within the DCS to determine the average heat input and NCV of the RDF;

(17) special measurements (e.g. because of special know-how or to achieve guarantees) such as:

a) monitoring combustion in the furnace for a co-ordinated RDF/air control (e.g. by means of colour TV cameras, infra-red or similar);

b) flame monitors, including electronics;

c) level measurement in the RDF metering bins (by continuous radar or two microwave or other suitable binary measurements);

d) flue gas temperatures (for minimum temperature monitoring);

e) boiler metal temperatures for tubes, headers, etc. operating in the creep range of the material;

f) pipe wall temperatures;

g) speed measurements including electronics (e.g. at conveyers etc.);

h) position/frequency of RDF feeder and feeder drives;

i) level transmitter and local control for water level in wet ash extractor;

j) weight measurements;

k) any other special measurements required for proper and optimal operation of the Contractor’s Plant;

(18) hardwired logic for critical events and sequences including all necessary provisions for events, trips and emergency shut-downs initiated in sections of the project outside of the scope of supply of the Contractor;

(19) software access to adjust the ladder logic of the PLCs;

(20) local controls including enclosures, for example, for the following systems, including but not limited to:

a) burner management system/boiler protection;

b) Combustion control;

c) rapping mechanism control including interval, sequence and duration timers adjustable from the control system;

d) slag/ash conveyor control, if applicable;

e) other controls which in the opinion of the Contractor would best be executed as local controls;

f) independent drum level monitoring system (Hydrastep or similar) with clear visual representation in the Plant control room meeting all Health and Safety Executive (HSE) requirements for unattended steam boilers;

g) all boiler water level controls and gauges to incorporate automatic blow-down sequence meeting HSE requirements for unattended steam boilers;

h) specification and integration of signals exchanged between these systems and other parts of the Plant, as well as their integration; and

i) specification and integration of drives for connection to the emergency power supply and UPS.

4.3 Operating conditions

4.3.1 Operating loads

The Contractor shall include all necessary provision for safe start-up including any requirements for venting the superheater, flash tanks, silencers, condensate collection and return and means of preventing boiling in the economiser. During the boiler start-up and until the live steam conditions required by the turbines have been achieved, the turbines shall be bypassed to the main condenser (part of turbine hall section).

The auxiliary firing shall be designed for gross heat released at minimum turn-down. The auxiliary firing system and associated controls shall be capable of achieving a combustion chamber exit temperature of 850°C prior to feeding RDF and within a normal boiler start-up period. The rate of heat-up on starting shall be determined by thermal stress considerations and not limited by burner capacity.

In the event of limited RDF delivery, the combustion chamber unit shall be capable of safe and stable operation at minimum turn-down for an unlimited period of time without auxiliary firing.

Between 75% [TBC] and 110% load, the combustion chamber shall be able to operate whilst delivering live steam at the guaranteed live steam temperature and pressure without heat input from the auxiliary firing system. Between minimum turn-down and 75% load, the steam temperature and pressure shall be sufficient for unlimited operation of the two steam turbines.

The feedwater supply temperature will be as determined by the Contractor for the flue gas treatment Plant, but shall be a minimum of 130°C at the economiser entrance at all conditions with RDF combustion.

4.3.2 Pressure regulation

The boiler shall be controlled to deliver a constant flow of steam at the required live steam conditions and at a firing rate set by the operator within the range of permissible firing rates as shown on the Firing Diagram. The steam pressure is regulated in the following stages.

(1) The turbines shall operate to take the continuous steam output from the boilers.

(2) Further increase in pressure will initiate the bypass around the turbines.

(3) If the steam pressure continues to rise, the boiler control system shall act to reduce throughput.

(4) Ultimately, the boiler safety valves will lift to protect the boilers.

The control system shall be designed to prevent the operator from setting the live steam flow at a rate higher than the design steam flow at MCR or at a rate lower than the minimum heat release rate shown on the Firing Diagram.

4.3.3 Advanced combustion control system

The Contractor shall provide an advanced combustion control system including monitoring of the gasification process, combustion process, char burn out and temperature conditions in the furnace and modification of the RDF feed rate, controlling primary and secondary air within each zone to optimise gasification of the RDF and combustion of the syngas with the objectives of maintaining even processing across the width of the furnace, consistent bed thickness, optimised energy recovery and minimising furnace component wear.

The gasifier and related systems shall be carefully designed to avoid gas escape and air in leak, which could otherwise lead to the formation of explosive mixtures and/or the release of hot and/or toxic gases.

All air inlets to the gasifier, including the fuel feeding section shall be equipped with block devices or anti-backfiring valves in series.

CO detectors, giving indication and alarm at 25 to 50 ppm CO, shall be installed in areas that syngas could potentially leak into.

The control system shall include specific monitoring and control of critical parameters, for example oxygen levels in the syngas, to minimise the risk of explosion.

The Contractor shall include for all necessary systems and provide detailed operating procedures that describe the safe purging of the gasifier, syngas system and flue gas system prior to start-up and following shut down of the Plant. Details of the emergency shutdown procedure shall also be provided.

The scope of supply shall include all controls, instrumentation, dampers, valves and associated equipment.


4.4.1 Firing Diagram

This plant shall be capable of stable operations at 100% MCR with an LCV of 10MJ/kg and a HCV of 15MJ/kg. This plant shall have a turn down ratio of 70% of MCR and turn up ratio of 110% of MCR. Emissions and steam conditions shall be guaranteed within this envelope.

4.4.2 Furnace

The furnace should be able to withstand thermal overload (refractory) for at least 30 minutes every 4 hours. It is acknowledged that this may present a risk of wear and tear for boiler and auxiliary equipment. The Contractor shall indicate the consequences if these values are exceeded. It is not intended that the Plant will be operated continuously in the thermal overload condition.

The furnace shall have provisions to ensure an even distribution of RDF under varying load conditions. Each furnace section in transversal direction shall be equipped with a feeder.

Provisions shall be made for a uniform distribution of air across the width of the furnace by dividing the air supply system into sections with individual drives.

If proposed the bubbling bed shall have an even airflow.

If proposed the grate bars shall be made of an approved material and be designed to prevent, as far as possible, riddlings falling through the grate. The grate substructure shall not have cavities within which ash and RDF particles can accumulate and cause obstructions to the uniform air distribution.

The necessary air spaces shall be made as fine as possible to be compatible with the rate of combustion air required.

If proposed over its length, the grate shall preferably be divided into sections with individual drives, so that each grate section can be operated at varying speeds for individual combustion control.

Suitable hoppers shall be provided within the combustion air compartments below each section of the furnace for the collection of riddlings.

The riddlings shall be guided to the ash extractor via riddling chutes and a pneumatic conveyor mechanism. The arrangement shall be amply sized and have a sufficient number of inspection, cleaning and maintenance doors at easily accessible locations.

The inspection and maintenance openings throughout the Plant shall have doors or covers equipped with quick closing and opening mechanism. The bolting of such doors and covers shall not be permitted. These shall be positioned so that personnel cannot accidently or inadvertently open or stumble into the open aperture.

The equipment used for operating the furnace shall be suitable for continuous operation without unscheduled outage for maintenance and repair. Special attention shall be given to prevent the ingress of dust and water to the moving parts of drives and bearings.

The furnace and support shall be sufficiently strong to withstand the impact of freely falling RDF from the top of the feed chute and pieces of slag and refractory from the furnace walls.

If proposed the grate bars shall be easy to replace without the need for dismantling other parts of the grate.

If required due to the calorific value of the RDF, furnace equipment shall be water cooled. Water-cooled systems shall be proven designs to allow for good water circulation in the equipment and to prevent any boiling of water in the equipment. Connections shall be flexible to take account of expansion and the constant movement of the grate bars. Access shall be provided to allow the grate cooling system and connections to be easily inspected and replaced if required without the need to remove parts of the structure or the grate bars. Heat absorbed shall be recovered and used in the Plant where viable. The Contractor shall provide all cooling systems required. Instrumentation shall be provided to monitor cooling water flows and temperatures and to provide an indication of any leaks.

Special tools and equipment shall be provided for the maintenance inspection and measurement of the grate and grate bars.

It shall be possible to wash down the area around and behind the hydraulic rams whist the grate is operating.

4.4.3 Hydraulic stations

Each hydraulic station shall contain at least two pumps (duty and standby) each with sufficient capacity to meet all requirements. The hydraulic station(s) shall be provided with bypass and pressure relief valves to prevent overheating of the pumps. The station(s) shall be provided with sufficient interlocks, pressure relief valves and alarms to prevent permanent damage to the equipment if operated incorrectly.

The station(s) shall be supplied with trays to contain any hydraulic fluid leaks.

If the hydraulic station(s) is provided with local control, it shall be connected to the DCS to allow start-up and shutdown together with monitoring of important indicators such as temperatures, pressures and levels.

Fire protection in areas where hydraulic oil is used shall be in accordance with NFPA 850. Where possible FM accepted fire resistant hydraulics fluids shall be used.

4.4.4 Gasification and combustion systems

The gasification and combustion systems shall ensure that:

(1) combustion is complete before the flue gases leave the system;

(2) the required temperature and residence time is achieved in the presence of sufficient oxygen and with good distribution of the gases across the combustion chamber;

(3) the combustion is performed without the adverse effect of slagging or fouling of the walls of the vessels;

(4) ignition of RDF is supported by good heat transmission from the hot flue gases to the ignition area of the RDF bed;

(5) the mixing of flue gases is sufficient to minimise corrosion and fouling of heating surfaces and fouling or destruction of refractory or brickwork; and

(6) the mixing of flue gases is optimised to minimise plant emissions in respect of particulate matter, carbon monoxide and the oxides of nitrogen and sulphur.

Multiple tapping points shall be included for the installation of syngas sampling and measuring equipment. The positioning of the sampling points shall be in accordance with the requirements of OFGEM for qualification as gasification for the purposes of claiming ROCs.

Special attention shall be given to thorough mixing of the secondary air with the gases leaving the furnace.

The furnace and combustion systems shall have sufficient and suitably arranged inspection windows to monitor the gasification in the gasifier, combustion in the burn area or boiler and the condition of all of the inside walls.

Combustion shall be monitored by means of two digital colour television cameras and scanners (if required [TBC]) per stream, to provide a view of the gasification process, the combustion process and in particular the line of fire showing where flames stop, supplied by the Contractor and mounted on the cold side of the chamber. The camera and scanners (if required [TBC]) shall not be inserted into a combustion chamber. The glass window in front of the camera and scanner shall be kept clean by means of cleaning air. Provision for cleaning of ash pile ups in front of the camera shall be provided.

All refractory materials and their means of support shall be designed to achieve a long operating life whilst protecting the walls of vessels and any heat transfer tubes installed within the walls from corrosion and minimising the build up of slag.

The Contractor shall furnish evidence by reference to manufacturer’s guarantees and existing Plants operating under similar conditions as to the life of the refractory materials to be used in each section of the Plant.

In areas where brick or tile walls are necessary, the material of the bricks or tiles shall have sufficient thermal and chemical resistance. The anchoring shall be designed to avoid the bricks or tiles becoming loose. Due consideration shall be given to thermal expansion between different sections of the walls and to the provisions for free expansion movements of the brickwork or tiles. The supporting arrangements shall be suitable for accommodating such movements without unduly stressing any section. The Contractor shall furnish evidence that the mortar intended to be used for the furnace refractory will have properties similar to those of the bricks that will be employed. The mortar shall have sufficient binding abilities which are maintained even under physical and chemical stresses.

The refractory at the walls where RDF leaves the feeder shall also be highly resistant to wear. Should such refractory not be available, special linings shall be applied.

The location of the auxiliary burners for start-up and assisting ignition shall be such that the operation of the burners does not adversely affect the walls, a grate, a circulating bed, the furnace and boiler when operating at maximum burner load and there shall be no flame impingement on any furnace or boiler component. The capacity of the gas burners shall meet the requirements to maintain the flue gases at a temperature of at least 850°C for 2 seconds when burning RDF with the lowest NCV and under all boiler loading conditions. The burners shall be capable of operation without significantly increasing CO or NOx emissions from the boiler.

The gasifier and related systems shall be carefully designed to avoid gas escape and air in leak, which could otherwise lead to the formation of explosive mixtures and/or the release of hot and/or toxic gases.

All air inlets to the gasifier, including the fuel feeding section shall be equipped with block devices or anti-backfiring valves in series.

4.4.5 Ash extractor

The ash extractor shall be of the water-bath type with ash removal by a proven design. It shall receive the bottom ash, slag as well as the riddlings from the different sections of the furnace. The water bath shall form an air-tight seal to the combustion chamber under all operating conditions.

The whole ash discharging equipment shall be able to handle the largest pieces delivered through the charging chute and also the unburnt RDF and char in case of an emergency cleaning of the furnace. A suitable number of inspection hatches shall be provided at various heights and positions on the charging chute to allow for the checking of blockages within the chute. A door shall be provided to remove bulky objects if required although this should not occur in normal operation.

The remaining water content of the ash shall not cause any faulty operation or excessive fouling of the downstream conveyor system or the ash treatment equipment.

The extractor shall be of an approved [hydraulic] type. All parts of the extractor subject to wear and tear shall be easily replaceable. Where possible, replaceable wearing plates shall be provided.

The time interval of the extractor pusher shall be readily adjustable. This shall be indicated in the Plant control room. The movement of the ram(s) shall be limited by position switches.

The cooling water feed control shall be of a proven design. The formation of excessive vapour shall be prevented by means of controlled vapour extraction. The extractor shall have a gate valve at the bottom of the trough for easy drainage into the drainage system. As cooling water, discharge water from the boiler blowdown flash tank shall be used as far as possible. There shall be no water discharge from the ash extractor. The water level shall be controlled with a level switch plus a shut-off and manual filling valve. An overflow shall be provided.

The trough shall be constructed of suitably reinforced steel plates.

Suitable and effective inspection facilities to check the operation of the extractor mechanism shall be provided. The opening at the extractor outlet shall be big enough to avoid choking at this opening by bulky scrap pieces.

To measure the temperature of the water in the ash extractor, suitably arranged local thermometers shall be installed.

Vibrating conveyors shall not induce vibrations or resonances in the building or inside the boiler house.

Vapour created at the ash extractor shall be extracted, preferably by the secondary combustion air system.

4.4.6 Boiler hopper ash extraction

Boiler ash shall be removed from the hopper through falling pipes or via rotary valves with a minimum diameter of 250 mm. The valve motors shall be sufficiently dimensioned, with a minimum power of 0.5 kW. The valve material shall be as a minimum cast steel with carbon steel blades.

The system shall convey the boiler ash to the bottom ash discharge system. The design shall be arranged so that it will be possible to modify it in the future to separately collect the boiler ash and discharge it to the FGT residue silo or a new separate silo.

Expansion compensating devices shall be installed between the chutes, transporters and extractors and shall be designed to prevent dust deposits in expansion joint corrugations.

4.4.7 Primary air fan, secondary air fan and fan for the auxiliary

burners

The primary and secondary fans shall be sized for at least 110% max air flow (based on the boiler operating at MCR) with the boiler in the most fouled condition shortly before a planned shutdown for cleaning and RDF with the maximum moisture content permitted within the fuel specification.

All fan impellers shall be statically and dynamically balanced and the fans design and tip speed shall be of a proven design at similar operating conditions.

The Contractor shall provide all equipment for reducing noise. Noise abatement fan casings shall be prefabricated and reusable.

The primary air to be supplied by the primary air fan will be drawn from below the RDF store roof area. The inlet of the suction duct shall be accessible for cleaning from the feed hopper platform.

The secondary air shall be taken from either the top of the boiler house above the boiler ceilings or from the RDF storage area and from the outlet hood of the ash extractor.

The combustion air contains solid particles which could subsequently foul and cause imbalance of the impeller. This shall be taken into consideration. Therefore, the fan and impeller shall be so installed that maintenance, in particular, cleaning and replacement, are simple and quick. A monorail with a trolley shall be provided above each fan and drive. The fan casing shall be detachable.

Fans shall be high performance design (minimum 70% efficiency) regulated by frequency converters. Fans shall be directly driven with flexible couplings. Shafts shall be protected by grills to prevent access. Expansion compensation shall be provided at the inlet and outlet. Fans shall be designed for an air intake temperature of at least 35°C. The fans shall be constructed from carbon steel as a minimum.

4.4.8 Combustion air ducts and dampers

The ducts on the discharge side of the fans shall be designed for the maximum air pressure produced by the fan.

The intake grilles of all combustion air fans shall be readily accessible for cleaning. The intake grilles shall be provided with removable sections.

Provisions shall be made to accommodate the expansion of ducts downstream of the steam air pre-heater by employing suitable expansion joints.

Expansion joints before and behind the fans shall be of the fabric bellow type.

Particular care shall be taken to ensure air tightness and, where possible, joints shall be of convenient size and shall not be seal-welded.

Access doors for cleaning, complete with frames, fittings and permanent seals shall be provided before and behind the fans, dampers and the steam air heaters.

Provision shall be made in the ducts for a sufficient number of measuring points.

Dampers shall be furnished where necessary with hydraulic drives suitable for remote actuation. All dampers shall be suitable for the maximum differential pressure which may be encountered.

4.4.9 Combustion air pre-heaters

Where flue gas heat recovery is included, the design point shall be selected to avoid condensation of acid gases and materials of construction shall be selected allowing for a potentially corrosive environment. Material selection shall be supported with operational experience from similar plants and design calculations.

4.4.10 Fuel systems and burners

In order to minimise condensation within the system and the generation of organic emissions during start-up, the start-up auxiliary firing equipment shall:

(1) increase the temperature as rapidly as possible, consistent with the avoidance of excessive thermal and material stresses; and

(2) use the minimum quantity of excess air, consistent with protecting the furnace and its components from excessive thermal stress.

The auxiliary fuel system shall be designed and installed according to the relevant legislation and regulation and codes of practice.

The auxiliary burners shall be equipped with automatic start-up devices so that they will go into operation if the flue gas in the furnace falls below 850°C and meet the requirements of the Industrial Emissions Directive and the Environmental Permit.

The maximum capacity of all the burners together shall meet the requirements of achieving a furnace temperature of 850°C during start-up before initiation of the RDF gasification process, as well as the requirement to achieve a flue gas temperature of at least 850°C for 2 seconds when processing RDF with the lowest NCV (due to high ash, high moisture or a combination of both) at all load conditions. The maximum capacity of the burners shall be chosen so that the start-up time is not limited by the capacity of the burners but by the allowable temperature gradient of the refractory material.

The burners shall be capable of stable combustion without excessive slagging or flame impingement on furnace walls with high combustion efficiency and complete combustion of fuel during all normal conditions of the combustion chamber, without increasing the CO emission levels above the specified limit, and with the lowest air/fuel ratio consistent with safe and complete combustion. The burners shall be designed so that they are capable of complete and efficient combustion when firing into a void, having regard to the wide range of temperatures and flue gas characteristics, velocities and turbulence which may prevail in the void.

Each burner shall be complete with all equipment necessary to be safely brought into and taken out of service from the control desk in the Plant control room. When the burners are not in operation, they shall be withdrawn automatically, protected by an automatic muffle gate and isolated from the combustion chamber, or cooled continuously with cooling air supplied from a compressor connected to the emergency power supply.

Each burner shall have an observation window to permit sighting and inspection of the flame. Observation windows shall also be provided at the side-walls so that burner malfunction causing flame impingement to a furnace wall can be observed and checked.

For ignition, each burner shall be furnished with a high voltage discharge igniter. All cabling required to be installed close to the burner and thus close to the boiler surface shall be suitably heat-resistant to the expected combustion conditions.

The burners shall be provided with flame monitoring and control to interface with combustion optimization systems and with a failsafe mechanism connected to the burner management system. The status of the flame shall be indicated and linked to the burner management system.

Each burner shall be equipped with fuel and combustion air flow measurement to facilitate close monitoring of fuel/air ratio over the full turn-down range. A facility to adjust the fuel air ratio shall be provided. The fuel air ratio, firing rate and burner status shall be displayed at the control desk.

4.4.11 Pressure parts

These requirements cover the boiler and pressure parts including but not limited to steam drum, economisers, superheaters, headers and main steam pipework.

The boiler shall have three radiant passes followed by a horizontal convective section containing evaporator screen, superheaters, evaporators and economiser. The convective passes shall be equipped with rapping gear for on-line cleaning. A vertical economiser may be acceptable if the Contractor is able to guarantee the continuous operating period of 8000 hours between manual cleans.

The boiler water and steam systems shall be designed for unattended operation.

The Contractor shall include provision in the boiler design for the future replacement of superheater, economiser and evaporator sections. It shall be possible to remove all tube bundles horizontally or vertically without the removal of structural steelwork, headers or steam pipes or the boiler house roof or walls. Drawings shall provided to indicate the lifting arrangements for the maintenance and replacement of heat transfer components.

Materials and process conditions shall be selected to deliver the required availability and to minimise the impact of known failure mechanisms such as creep, corrosion, fatigue, flow assisted corrosion (FAC), and erosion (including erosion from soot blowers). Material selection must be supported with operational experience from similar plants.

All tube material shall be of seamless construction. ERW (Electrical Resistance Welding) tube is not permitted.

All water and steam pressure parts shall be attached by welding, i.e. to the drum, headers, etc., the use of set-on type is preferred. The use of set-in type and / or set-through type welds is not precluded but may require additional inspections. All pressure parts welds shall be full penetration and partial penetration welds are not permitted. Designed-in, un-fused landings in the weld prep geometry shall not be permitted.

For this purpose, such items shall be provided with stub ends which shall be welded to the items concerned. Socket welds and fittings are not permitted. Even if the tubes are not shop welded during manufacture, the design of the boiler must allow for a safe site weld position at which it is possible to access the tubes. Each stub end shall have a sufficient length to ensure that the welding on of tubes will not affect the material of drum, headers, etc. All tube and stub ends shall be suitably prepared for welding. The tube materials shall comply with the applicable standards and the wall thickness shall allow for the thinning of the tube bends and any corrosion/erosion. All tube stubs shall have sufficient wall thickness at the point of connection with vessels and manifolds so as to facilitate future replacement of tubes. All welds are to be full penetration.

The boiler shall be built in such a way as to minimise the possibility that damage, wear or corrosion will occur after prolonged operation. The Contractor shall state the anticipated life of each section.

The Contractor shall ensure that the method of manufacturing the tube bundles, headers, drums, etc., particularly with regard to welding, is suitably approved and controlled.

The Contractor shall ensure that suitable protection to prevent corrosion during transportation is applied prior to leaving the factory. As a minimum, weldable red oxide primer shall be applied.

Material certification is required for all pressure part materials to BS EN 10204 (3.1 or 3.2). As-built drawings are required for all boiler plant, in particular, isometric drawings together with full weld details are required for each piping spool. A database of all pipework welds and all pressure part components (pipe, elbow, reducer etc.) shall be made available in MS Excel or MS Access format.

The Contractor shall set out his proposals for pipe bending (i.e. use of elbows, cold formed or induction bends). The use of cold formed or induction bends is not precluded. However, their use will be subject to the Project Manager’s comment. The Contractor shall set out a quality control plan for the Project Manager’s comment showing how the Contractor proposes to control the manufacturing and heat treatment processes for any such bends and accurately document their numbers, details and location.

4.4.12 Arrangement of heating surfaces

The boiler shall be equipped with facilities to ensure uniform flue gas distribution.

The convection heating surfaces shall be designed so that:

(1) all tubes shall be arranged in-line;

(2) all heating surfaces shall be made of plain tubes; and

(3) the heating surfaces shall be designed for easy replacement.

Evaporator headers shall not be located in the flue gas path but where this is unavoidable they shall be protected by e.g. Inconel cladding or refractory and in a location which is accessible for inspection without cutting away walls or tubes.

4.4.12.1 Economiser

The Contractor shall decide on the most appropriate design for the economiser tubes, between plain seamless tubes and seamless finned tubes.

If finned tubes are selected for the economiser then the design shall incorporate plate fins (as opposed to spiral fin coils) with a minimum spacing of 15 mm between fins.

The economiser shall be designed to provide the design full load flue gas exit temperature under both clean and fully fouled conditions. Facilities shall be included to control the flue gas exit temperature at the design value and to avoid back end corrosion.

Special consideration shall be given to allow easy access to the economiser for inspection and maintenance by providing sufficient space and access doors between economiser banks. All tube elements shall be arranged and fitted in such a manner that each tube element can be easily removed for repair and replacement.

In the range of flue gas temperature below 400°C, uncooled tube hangers may be used.

Tubes which are arranged horizontally shall be sufficiently supported to avoid sagging under the additional weight of fly ash and water. Access points to allow in-situ remote video inspections shall be provided.

The arrangement of the economiser shall allow for an extension of at least 10% of the heating surface, in case operation results suggest such corrections to be necessary. The amount of free space shall be shown and marked in the drawing of the boiler.

The design of the duct between the economiser exit and the FGT system shall provide a length of adequate straightness for appropriate measurement of the flue gas characteristics, in particular flow, temperature and emissions etc.

4.4.12.2 Evaporator with steam drum

The evaporator system shall be designed and arranged to ensure reliable water circulation without forced circulation during all operating conditions.

Sections of heating surfaces with different heating rates shall have separate connections to the drum and to the downcomer system.

The gas-tight welded tube walls shall be tied together and stiffened by means of buckstays which shall enclose the furnace and radiant section as well as the convection section.

The design of the buckstays shall take into consideration the expansion of the gas tight welded tube walls during start-up and shall not result in additional forces.

The drum shall be of the welded type with a manhole at each end. The wall thickness of the drum shell shall be uniform throughout. It shall be amply sized to ensure adequate volume to provide for suitable level control and to preclude the possibility of carrying over of water during any transient mode of Plant operation as well as to provide adequate space for inspection and maintenance work and for manual cleaning operations.

The drum shall be fitted with the necessary internal fittings for the uniform distribution of the feedwater and with sufficient numbers of separators for efficient separation of water from saturated steam.

The drum shall be provided with dished ends and with the required nozzles for all water and steam connecting tubes, drains, vents, blowdown, installation of safety valves, controls of pressure, temperature, analysers and water level. All drum nozzles for valves, fittings, boiler mountings and tube connections shall be welded to the drum. The drum and headers shall be provided with shop-welded tubular stubs of the set-on type.

All internal and external attachments welded to the drum shall be made before final heat treatment.

The connection between drum and downcomers shall be well distributed on each side of the drum. Connection of downcomers to the drum at the dished ends shall be avoided. The downcomers shall be designed to be ample in cross-section and shall be arranged at an unheated position to avoid any disturbance of the circulation.

The continuous blowdown shall be controlled automatically by the conductivity of the water in the drum.

The attachment of internal fittings or deflectors to the drum shall be such as to ensure against displacement while the unit is in service, but, except where specifically approved otherwise, they shall not be welded to the internal surfaces of the drums. Bolts and nuts inside the drums shall be fitted with cap nuts, tack-welded in position. The drum internal fittings shall be removable through access manholes. The manhole covers shall be hinged at the inside for easy handling.

4.4.12.3 Radiation and convection pass

If installed, the evaporator walls of radiation and convection passes shall be of fully water-cooled gas-tight welded membrane wall type.

The volume and dimensions of the furnace must be proportioned so that, under all conditions in normal operation, there will be no possibility of flame impingement upon any portion of the walls or other parts of the furnace enclosure.

The furnace size shall provide sufficient space for flame development and shall allow complete and efficient combustion of the fuels specified before the furnace outlet.

The radiation and convection pass shall be equipped with all necessary access and inspection doors, with access doors being located at both side walls. A sufficient number of observation windows shall be provided in the appropriate positions to allow for visual observation of the flames, the combustion process and the routes of the flames.

An adequate number of suitably positioned and sized pipes with a double valve arrangement shall be provided to allow draining and venting of the tubes of the radiation and convection pass.

4.4.12.4 Superheater and desuperheater

The boiler shall be provided with the necessary convective superheater which shall be capable of increasing the temperature of the steam flow as specified. The superheater shall be divided into a minimum of two sections. The superheater heating surface and the attemperator spray water control valves shall be designed in such a way that the final temperature of live steam at the boiler outlet will be automatically maintained constant under varying load conditions.

The Contractor shall use spray attemperators of proven design. Each attemperator shall be designed for the most unfavourable conditions, to cope with a steam flow from minimum turn-down to 110% of MCR. The required live steam temperature shall be maintained within the firing range 90% to 110% of MCR. Steam temperature shall be sufficient for unlimited turbine operation down to minimum turn-down.

The desuperheating water for the spray attemperators shall be taken before the feed water control valve. The desuperheating water pressure shall be high enough to ensure superheater protection at all times.

The material of the final superheater shall be chosen to provide 50,000 operating hours between replacements The contractor may choose weld-on coatings, resistant materials, or a high corrosion/erosion allowance in design to achieve this objective. The superheater material shall be 16 Mo3 as a minimum. The first superheater bundle in the flue gas direction shall be arranged in parallel flow. The arrangement of the superheater shall allow for an extension of the heating surface by at least 10%, in case operational results suggest such corrections to be necessary. The amount of free space shall be shown and marked in the drawing of the boiler. Protective evaporator tubes with the same transversal pitch in the direction of flow of the flue gas shall be arranged in front of the first superheater bundle.

All fittings, spacers and supporting lugs of the cooled supporting tubes exposed to the hot flue gases shall be made of a heat and corrosion resistant material. Access points to allow in-situ remote video inspections of desuperheater cones and liners shall be provided.

Sufficient space between superheater banks shall be provided to allow for easy access to the superheater for inspection and maintenance purposes.

Location of superheater headers within the gas path shall not be permitted.

The individual superheater’s tubes shall be arranged to ensure they can be drained.

The superheater outlet header shall be provided with nozzles, vent connections, all drains, and tapping points for measuring and control instruments. All vent lines should be brought to a common roof vent well provided by the Contractor, and which is fitted with suitable silencers.

4.4.12.5 Headers

The headers shall be of seamless forged manufacture or solid drawn construction. The tube elements shall be connected to the headers by means of welding.

All butt welds at the headers and tubes and welding of nozzles or tubes to the drum or headers, whether carried out in the Contractor's workshop or at the Site, shall be subjected to an approved welding procedure and to an agreed method of weld examination.

All distribution headers shall be adequately sized. To enable visual inspection of the internal header space during maintenance periods, inspection ports with removable caps on header panel sections shall be provided at sufficient locations to facilitate such internal inspection. The closure of these shall be of a permanent nature, using full penetration welds.

The drum and headers shall be provided with shop-welded tubular stubs of the set-on type and thicker than the minimum calculated tube thickness. These shall project a sufficient length to ensure that the welding of the tubes will not affect the material of the drum and headers.

All tubing shall be of the seamless type.

Flat end plates on headers and division plates are not permitted.

Surface finish of forgings shall conform to the following requirements.

For ultrasonic non-destructive testing the outer surfaces shall be N8 (BS1134) – 3.2µm CLA or better.

Plain tubular sections shall conform to a flatness tolerance of 0.5 mm in 50 mm.

The bore of forgings shall be N8 or better and in particular a gramophone finish such as produced by a sharp nose tool on final boring to size is not permitted.

Surfaces shall not contain sharp changes of section or imperfections acting as stress raisers.

4.4.12.6 HP-water and steam pipes

The HP water and steam pipes necessary for connecting the various parts of the boiler such as the economiser, drum, downcomers, tube walls of furnace and convection pass, individual superheater stages, headers, etc. and the main steam piping to the inlet to the steam turbine shall be provided and shall be accessible, vibration-free and properly arranged. The pipes shall be routed in such a manner as to avoid damage due to thermal expansion. All pipes and tubes shall be seamless.

The Contractor shall set out his proposals for pipe bending (i.e. use of elbows, cold formed or induction bends). The use of cold formed or induction bends is not precluded. However, their use will be subject to the Project Manager’s comment. The Contractor shall set out a quality control plan for the Project Manager’s comment showing how the Contractor proposes to control the manufacturing and heat treatment processes for any such bends and accurately document their numbers, details and location.

Provision shall be made for warming-up of large-bodied valves such as the main steam stop valve, etc., if required in the Contractor's design.

4.4.13 Mountings and fittings

The boiler shall be assembled with all necessary mountings and fittings to comply with the applicable standards and the Contractor's design. Except where the flanged connection is essential for the maintenance of the component, all valves, mountings and fittings shall be welded rather than flanged except where the flanged connection is essential for repair or replacement of the component.

A sufficient number of safety valves shall be fitted at the boiler drum, superheater outlet and pressure vessel and shall be of proven design and adequate size. If more than one safety valve is installed on the boiler drum, superheater outlet and pressure vessel, they shall be set to blow in a pre-determined sequence. All equipment necessary for maintaining, setting and gagging of the safety valves and for hydrostatic test purposes shall be supplied.

The safety valve(s) at the superheater outlet shall be set always to open before and close after the safety valve(s) on the drum opens and closes respectively. The superheater safety valve(s) shall have such a capacity that the superheater cannot be overheated when the drum safety valve(s) is (are) blowing. All safety valves shall be easily accessible for maintenance. Slinging provision shall be provided to facilitate their removal.

4.4.14 Metering

The steam boiler shall be equipped with reliable flow transmitters capable of long-term accurate and reliable service, so that the flow is monitored within the control system. Flow transmitters shall be provided at the:

(1) live steam connection from the boiler superheater to the turbines (this shall comprise flow, pressure and temperature as well as mass-flow computation);

(2) boiler feedwater supply to the economiser of the boiler (flow and temperature);

(3) make-up water supply to the boiler (flow and temperature); and

(4) spray water flows.

Pressure, temperature and flow (non orifice plate) instrumentation shall be of sufficient accuracy for Performance Test measurements.

Additional blanked flow measurement ports shall be provided to facilitate the installation of performance test flow metering devices.

4.4.15 Thermal insulation and cladding

The Contractor shall comply with the requirements for thermal insulation in Schedule 22C.

Due consideration of the design and installation of boiler cladding shall be undertaken to prevent areas for dust collection. Cladding shall be installed using self tapping screws. Rivets shall not be used unless unavoidable.

4.4.16 Access doors and observation ports

The boiler shall be provided with sufficient openings for access, observation, inspection and cleaning as may be required during operation, maintenance and repair.

The boiler and furnace shall be provided with access openings for a full-width traverse using a water-cooled gas sampling and suction pyrometer probe at various planes in the first pass, at the second and third pass, at the inlet to the superheater and between the main convective heat transfer banks.

Access doors shall be provided at the bottom of the ash hoppers and on the left and right sides of the boiler between all heating surface bundles.

There shall be an adequate number of access and inspection doors within the space between each tube bank of the boiler. Access doors shall be rectangular, arranged in pairs with overall dimensions of 750 mm x 1000 mm high. Access doors shall be installed on both sides of the boiler, and designed to enable staging to be erected using the bottom of the door as the support for the stage. The doors shall be hinged, and each shall have a handle. The hinges shall be external and designed to prevent sticking or seizure during the operational life of the boiler. The doors shall be provided with maintenance platforms for easy accessibility with stairs (not ladders), and dust catchers. A handle shall be installed above each door to assist entry and exit through the door.

Access platforms, floors and walkways shall be provided at each inspection door. The lower edge of the door shall be 1000 mm above the platform. Maintenance platforms shall have a minimum width of 1200 mm for easy accessibility, accessed by stairs (no ladders) with a width of 1200 mm. Dust catchers shall be fitted beneath each inspection door. A fixed handle shall be installed above each door to provide support when entering the boiler.

Observation openings and windows shall be provided and shall allow an unrestricted view of all burners and flames. The windows shall also allow observation of all surfaces liable to flame impingement on the walls, the line of viewing being parallel to these surfaces. Windows at each side of the boiler front, to permit viewing along the side-walls, shall be provided.

Where necessary, air purging shall be provided to keep observation openings sealed, clean and cool. The glasses shall be of high temperature resisting material and have external covers to prevent cracking. They shall be protected on the hot side by pivoting metal plates. These metal plates shall be so designed that they will not be jammed during the operating life of the boiler. It shall be possible to renew the glasses during operation of the boiler, using aspirating air or the above-mentioned pivoting metal plates.

A sufficient number of inspection openings shall be provided for the purpose of inspecting all combustion chamber walls and the heating surfaces.

The flue gas ducts shall be provided with access and clean-out openings with suitable gaskets in locations readily accessible from the steel support structure. Openings for access shall have removable covers and those for clean-out shall have hinged doors. The hinges shall be external and designed to prevent sticking or seizure during the operational life of the boiler. Material selection shall take into account the possible corrosive effect of flue gases during the lifetime of the Plant.

On headers, access points to dead spaces to allow inspection / repair of headers (around full circumference) and bends shall be provided.

4.4.17 Cleaning devices

The boiler shall be equipped with a proven system for cleaning the convective heating surfaces.

The cleaning device shall be of such scope and design that by its use the Availability Guarantees for the Plant can be met.

4.4.17.1 Mechanical rappers

Rappers shall be designed to avoid increased maintenance on the heating surface tubes and premature failure of the boiler. Consideration shall be given to noise during rapping so that imposed noise limits are satisfied.

It shall be possible to carry out rapping either in a pre-set sequence or individually both from the Plant control room or the local panel. The sequence of operation of the rappers as well as the subsequent isolation of the system shall be operated automatically by pushing one button. However, it shall be possible to actuate each rapper separately by push buttons at the panel.

4.4.17.2 Sootblowers

The material of the soot-blowers shall be heat-resistant and selected in accordance with the flue gas temperature in the respective areas.

All steam and drain valves shall be provided for automatic operation. During the warm-up period prior to the blowing period, the steam pipes to each soot-blower shall be warmed up to the saturated steam temperature and the whole piping system shall be well drained so as to prevent the accumulation of water or condensate. Temperature sensors shall be provided at the drain line to ensure that soot-blowing cannot be started until the saturated steam temperature has been achieved and there is no condensate in the piping system.

All soot-blowers shall be provided with electric drives. They shall be operated automatically from the Plant control room and from the boiler's common local control panel which contains all switches, pilot lights, contactors and fuses necessary for operation and supervision.

It shall be possible to carry out soot-blowing either in a pre-set sequence or individually both from the Plant control room or the local panel. The sequence of operation of the blowers as well as the preceding warming up and draining of the pipes and the subsequent isolation of the system shall be operated automatically by pushing one button. However, it shall be possible to actuate each blower separately by push buttons at the panel.

All retractable soot-blowers shall be provided with facilities for manual withdrawal in the event of failure of the power drive. Accommodation for test pressure gauges shall be provided in the steam supply pipes and at each of the blower lances to check the blowing steam pressure. The pressures shall be adjusted as necessary to obtain the optimum conditions. There shall be a provision for continuous steam flow through a soot-blower that is stuck until it is manually withdrawn.

It shall not be possible to operate any soot-blower unless it is supplied with steam. All retractable soot-blowers shall be adequately supported and shall be provided with lateral protection against knocking, as well as guides for insertion. All soot-blowers shall be suitably guarded to prevent personnel coming into contact with moving parts or hot surfaces.

Adequate lubrication shall be provided.

Erosion caused by blowing against the boiler tubes shall be avoided by the choice of adequate distances between the heating surface bundles, and by the provision of shields for the affected tube surfaces which are facing the direct impact of the soot blower jet. Alternatively the tube walls may be protected by local Inconel overlay, coated during manufacture.

Position indicators shall be provided to indicate both the withdrawn and the fully inserted position for each soot-blower. An alarm shall be initiated in the Plant control room in the event that any blower is in overtime or standstill condition before the soot-blowing cycle is completed.

4.4.17.3 Protection during extended outages

Should it become necessary to preserve the boiler or any associated equipment prior to Taking-Over the Contractor shall be responsible for ensuring that the Plant is kept preserved and protected against corrosion until it can be put into operation again.

In the event that the delay in commissioning exceeds four weeks the boiler shall be either dry-stored with suitable desiccants in trays, or wet-stored and nitrogen-sealed. Wet storage shall including drums and superheaters where practicable. Filling fluid shall be a solution of deionised water and ammonia to raise the pH value to a level that prevents the onset of corrosion. The water shall be circulated by use of a circulating pump.

For preservation of the boiler the design shall provide all necessary connections required for:

(1) injection of any chemicals at the economiser inlet;

(2) nitrogen supply connection for the steam drum and superheater outlet conveniently located at ground level; and

(3) any other connection required for preservation purposes, depending on the boiler design and on the experience of the Contractor.

The Contractor shall provide all necessary equipment, materials and consumables to maintain the boiler parts in a non-corrosive state, if required.

4.4.18 Selective non catalytic reduction of NOx

The SNCR system shall use dry urea, urea solution or 25% ammonia solution.

The injection distribution shall be optimised to minimise reagent consumption while achieving high NOx reduction. As such, injection nozzles shall be provided at appropriate different levels to allow injection points to be changed as necessary during operation for optimisation of the system.

The system shall be provided with all facilities to enable safe filling, start-up, operation, draining and flushing.

The system shall be provided with sufficient valves to enable safe isolation of all necessary sections and utilise duty and standby pump systems.

The Contractor shall take into account all relevant regulatory requirements relating to the handling, storage and supply of hazardous chemicals to the process, and ensuring that the Plant does not exceed the thresholds associated with COMAH lower tier installations.

4.4.19 Boiler instrumentation and control

The Contractor shall define, at an early stage of the software design, together with the suppliers of the DCS and the involvement of the Purchaser, the:

(1) format of the necessary graphics, operator interface facilities, alarms, set-points, sequence logic, trend and display facilities, agreement with the supplier of the supervisory package on the definition and optimisation of the storage of status, measurement and trend information for access and collection by the supervisory control system on a local area network; and

(2) security requirements for accessing the PLC and DCS systems at different levels, e.g. operator access, maintenance access, programmer access etc.

The documents and control system software shall be kept current by the Contractor throughout the course of the project.

The contractor shall propose an option that the boiler and combustion system be equipped with a combustion optimization and control system which learns and implements combustion and control optimization.

The boiler and combustion system shall be equipped with all measurement and control facilities necessary for accurate and responsive control and diagnosis of any period of poor performance and include but not be limited to:

(3) the RDF feed rate, grate speed or bubbling bed agitation, primary and secondary air flow and distribution shall be automatically controlled to maintain a constant steam flow and the necessary gasification and combustion conditions as determined by the Contractor’s design;

(4) activation of the auxiliary burner(s) if the combustion control system cannot maintain a minimum temperature of 850°C for 2 seconds after the last injection of secondary air;

(5) the permanent measurement, computing and logging within the DCS of:

a) the temperature and mass flow of all primary and secondary air streams;

b) combustion/flue gas temperature monitoring points at low and high levels by a method approved by NIEA for the on-line demonstration of compliance with the two-second residence time criteria, as established in the CFD modelling during the design stage;

c) flue gas temperature at the exit from each radiant pass;

d) flue gas temperature at the entry and exit of each convective tube bundle;

e) flue gas temperature at the boiler exit;

f) flue gas oxygen and carbon monoxide content at the boiler exit;

g) flue gas volume flow with calculation of mass flow;

h) boiler feedwater flow-rate and temperature;

i) steam drum pressure and level;

j) superheated steam flow, pressure and temperature;

k) water side temperature measurement for inlet and outlet of all convection passes; and

l) header temperature and on-line boiler chemistry monitoring;

(6) provision for full traverse sampling at a minimum of:

a) two planes in the first pass;

b) one plane in each radiant pass;

c) one plane between each tube bundle, where access requirements for the above shall include floor space to the same width as the boiler to allow insertion and withdrawal of combustion sampling probes; and

d) measurement of the steam flow to soot-blowers (if applicable) so that the boiler controller can compensate for soot-blowing.

All boiler control, start-up, shut-down and emergency sequences shall be fully automatic and co-ordinated with the operation of all associated parts of the Plant by the control system.

An automatic logging facility for all boiler parameters shall be provided.

All analogue and digital measured values, conditions, status and control signals shall be logged by the control system.

Boiler drum level indication to the operator shall be the HYDRASTEP system or equivalent. This facility shall cover local and remote (in the Plant control room) indications and the system proposed shall meet all relevant boiler safety requirements.

4.4.20 Boiler house and office space heating and cooling

The space heating and cooling requirements within offices and other areas of the Plant and Site buildings that require heating and cooling, is to be provided from a low grade waste heat source to minimise the use of electricity in the space heating and cooling system.

5 Bottom and boiler ash handling equipment


All items under the scope of supply should conform in every way to the relevant and latest British and European standards, codes of practice, regulations and laws applicable to bottom and boiler ash handling equipment, including but not limited to:

BS EN 982: Safety of machinery. Safety requirements for fluid power systems and their components. Hydraulics

BS EN ISO 12100-1: Safety of machinery. Basic concepts, general principles for design. Basic terminology, methodology

BS EN ISO 13849: Safety of machinery. Safety-related parts of control systems. General principles for design

BS EN ISO 13850: Safety of machinery. Emergency stop. Principles for design

EN 60204-1: Safety of Machinery: Electrical equipment of machines: General requirements

EN 60947-2: Safety of Machinery: Low-voltage switchgear and control gear. Circuit-breakers

EN 60947-3: Safety of Machinery: Low-voltage switchgear and control gear. Switches, disconnectors, switch-disconnectors and fuse-combination units

5.2 Scope of supply

This section covers the equipment required to remove bottom and boiler ash. Fly ash and flue gas treatment residues are covered in the flue gas treatment section. Bottom ash is defined as the material which falls off the end of the grate or out of a circulating bed, including riddlings. The boiler ash is the material which passes up off the grate or out of a circulating bed and is then separated out in the boiler into the boiler ash hoppers.

The Contractor shall design, deliver, install, integrate and commission, test and certify the following scope of supply for a complete ash handling system comprising of:

(1) an ash handling conveyor system to transport the bottom and boiler ash from the grate or circulating bed and hoppers to the ash bunker;

(2) facilities for the handling of oversize material using a vibrating screen or similar device;

(3) an ash store with a minimum of [10] days storage capacity with the Plant operating at MCR and without operator intervention;

(4) one ash weigh and loading hopper;

(5) a vehicle positioning guide which enables the driver of the ash vehicle to accurately position the vehicle beneath the loading hopper;

(6) a local control interface which enables the driver:

a) either to talk to the Plant control room; or

b) to initiate the loading procedure;

c) a sliding door which seals the bottom of the hopper and opens when the system is ready to discharge the hopper contents into the vehicle;

d) facilities for safely taking appropriate quantities of samples of the bottom ash for off-site testing; and

e) all equipment required to ensure the safety of the operator or driver when the system is unloading.

The contents of all ash silos and hoppers shall be measured using load cells.


The boiler ash, slag and scrap shall be discharged continuously from the ash extractors onto an appropriate conveying system discharging via the oversize screens to the ash bunker.

The Plant shall be designed to operate continuously 24 hours/day. Ash will be transported off-site ash by bulk RDF haulage vehicles.

The bottom ash and boiler ash is intended to be reprocessed into aggregate off-site. The primary method of ash transport to this reprocessing area shall be by vehicle via an automatic hopper loading system utilising an ash storage area and ash handling equipment.

Bottom ash storage arrangements shall minimise conveyor runs/spillage to avoid windblown nuisance and cleaning. Any discharge points shall be fully enclosed including any vehicle loading.

Fly ash storage must also be provided with similar measures to prevent dust nuisance from the fly ash during vehicle loading or in windy conditions.

The bottom ash handling system shall be designed for the maximum RDF capacity of the gasification chamber, taking into consideration the maximum content of non-combustible material and water adherent to the ash and slag. The system shall also be designed to handle ash from boiler overhaul activities.

The uneven delivery of RDF to the boiler, and hence the subsequent variations in ash production shall be taken into account when sizing the ash handling equipment.

Each combustion chamber shall have its own ash extracting device beneath the grate or circulating bed. All fly ash and dust from the boiler, including any from the economiser section, shall be collected and transported to the ash extracting devices including but not limited to beneath the grate, the circulating bed, the economisers or any boiler components requiring ash removal.

The ash processing system shall include magnets to separate out ferrous metals from the ash. The system shall be designed to maximise ferrous metal extraction.

All transfer parts between conveyors and feeders must be equipped with closed transfer chutes to eliminate any spillages.

The ash handling and storage area shall be provided with drains passing to the effluent treatment Plant for re-circulating the water to the process.

Closed conveyor systems shall be provided with emergency stop buttons. Open conveyor systems shall be provided with pull cord emergency stop system extending the full length of the conveying system on each accessible side. Sirens and signboards shall be provided for all conveyors to warn personnel of their automatic starting.

The ash density to assume for design purposes shall be 1,200 kg/m³.

5.3.1 Electrical, control and monitoring equipment

The ash handling system shall be complete with all necessary 400 V AC and DC power supplies from the main AC and DC switchgear located in the respective switchgear rooms.

The control, monitoring and operation of the entire ash handling system shall be from the Plant control room. Local control points shall be provided for each conveyor and separator.

Filling of a pre-weighed quantity into the vehicle loading hopper shall take place automatically.

Any luminaries should be accessible from a walkway or the ground.

5.3.2 Ventilation

The Contractor shall ensure that ash conveyors and containers are adequately ventilated to prevent the possibility of a build-up of hydrogen or phosgene, resulting from the presence of aluminium in the ash.

5.3.3 Ash conveyors

The conveyors shall have a local push button control allowing the discharge of ash into the ash store to be interrupted during abnormal operation.

The material of the conveyor in the area of scrap separation shall be of the non-magnetised type.

Conveying systems for dry ash shall be totally enclosed and designed to contain spillages and prevent the release of dust particles.

The mechanical conveyors shall be suitable for operation in horizontal and inclined planes. Parts subject to wear from abrasive contaminants, including anti-friction bearings, shall be pre-packed lubricated and effectively sealed against the ingress of moisture and contaminants.

The equipment shall be designed to make regular inspections straightforward and to be easily cleaned with a sufficient number of access panels providing access from both the top and side of the equipment.

5.3.4 Ash store drainage scheme

The ash store floor shall be laid to a fall from a high point at the centre of the ash storage area to a low-point at least 500 mm below the high point at each end.

There shall be a flat horizontal area at each end to enable water collected to be pumped out.

The Contractor shall provide three submersible pumps, two installed and one spare. The installed pumps shall be arranged so that they can be manually lowered by means of an electric hoist into the sump. The pumps shall be equipped with local controls. There shall be a suitable retractable support arrangement so that, when not in use, the support assembly cannot foul the ash crane.

The system shall be equipped with all necessary flexible and permanent piping connections with quick release connections to drain the water collected from the ash bunker to the effluent collection, settlement and recycling system.

Requirements for civil design pf the ash store and requirements for mobile plant are described in Part D - Civil engineering specification.

6 Flue gas treatment system


All items under the scope of supply should conform in every way to the relevant and latest British and European standards, codes of practice, regulations and laws applicable to flue gas treatment (FGT), including but not limited to:

Industrial Emissions Directive (IED);

the specification of hydrated lime detailed in appendix A of this Schedule; and

the specification of relevant Consumables detailed in Specification Part A.

The flue gas treatment process shall be designed to achieve the emission limits set out in the Environmental Permit.

6.2 Scope of supply

The FGT system shall be of the semi-dry, conditioned dry or dry type with reverse jet bag filters.

The Contractor shall design, deliver, install, integrate and commission, test and certify the following scope of supply for a complete FGT system, comprising:

6.2.1 Mechanical equipment

The FGT line shall be based on a proven design, complete in all mechanical respects and shall include but not be limited to:

(1) dry lime reaction system consisting of but not limited to:

a) reaction tower with inlet and outlet ducts, dust collecting hoppers including discharge outlet, guiding baffles for the flue gas distribution;

b) support structure;

c) all necessary manholes, access and inspection doors;

d) all product discharge devices including extraction aids, rotary valves, gate valves;

e) complete dry lime injection system comprising transportation and flow measurement systems and dry lime injection and distribution system;

(2) fabric filter with lime, activated carbon and adsorbent dosing, complete, comprising as a minimum:

a) one adsorbent injection device with housing, gas inlet and outlet hoods with flange connections (if necessary), insulation, cladding, all necessary internals, such as gas flow distribution systems, nozzles, piping, valves, discharge equipment (if necessary), inspection facilities with all necessary stairways and platforms, access doors and inspection ports;

b) one multi-compartment fabric filter consisting of filter housing (gas-tight welded construction, stiffened as necessary, gas inlet and outlet hoods with flange connections, and all compartments supplied with all necessary inlet and outlet dampers;

c) under normal operation at 100% MCR the filtration velocity should not exceed 1.1 m/minute, the filter system shall also be capable of handling for short periods a flue gas volume equivalent to the boiler operating at 110% MCR with two compartments isolated and without the face velocity at the fabric exceeding 1.3 m/minute, and, where multi-part cages are used, the Contractor shall employ an efficient and effective design so that removal and replacement of bags and cages is straightforward, does not significantly increase replacement time (in comparison to a single piece cage), and does not increase the likelihood of bag damage;

d) all isolation facilities necessary to provide safe access to individual compartments with the filter system on-line and operational for purposes of capping-off or replacement of individual filter bags;

e) residue collection hoppers with discharge nozzles, clean gas chambers, insulation, cladding, electrical trace heating a redundant method of detecting the level of residue in each hopper;

f) support structure with supporting bearings including insulation, all necessary access doors for inspection and all openings for maintenance (e.g. bag replacement);

g) system to detect and indicate a problem of deposition of residue within the filter housing or hoppers including early warning of the risk of exothermic reactions and fire or smouldering (e.g. temperature sensor);

h) gas flow distribution system to ensure even distribution of flue gases across the filter system and avoiding excessive turbulence and abrasion of bags on steel support elements;

i) filter bags with support corrosion resistant cages and attachment system, with the fabric filter bags capable of operating with flue gas temperatures of up to 170°C for continuous periods of up to 8 hours;

j) bag cleaning system complete with compressed air system (which shall be connected to the main plant compressed air system and shall not require its own compressors) and all necessary control equipment for automatic sequential cleaning operation based on differential pressure measurement with adjustment for pulse duration and frequency;

k) air reservoir with sufficient capacity, complete with suitable valve control, to feed the high demand of the FGT during pulsing and other operations without adversely affecting the air pressure throughout the rest of the Plant;

l) inspection facilities with all necessary stairways and platforms;

m) internal platforms and stairways;

n) enclosed discharge system for the used adsorbent with gate valves, rotary valves, screw conveyors and/or drag link conveyors, pneumatic conveyors from fabric filter to the silos for spent adsorbent, and electrically trace heated where necessary to prevent build-up of residue within the handling system;

o) all silos shall be designed for 10 days storage;

p) heating system for start-up of the filter from cold condition including necessary facilities for secure starting up and shutting down without a filter bypass;

q) pre-coat system for applying dry lime and activated carbon to the bag filter at start-up with the filter system on-line;

r) heating system for normal operation and for short-time shut-down;

s) all level control and monitoring equipment including bag rupture monitoring equipment via main emissions monitoring system;

t) all necessary conveying systems for the transportation of adsorbent agents from the silos to the adsorbent injection point;

u) all necessary safety installations for storage and transportation of adsorbent; and

v) all safety devices as required for preventing, detection of and stopping temperature excursions, including connections for inert gas supply;

(3) flue gas system complete within the FGT system comprising as a minimum:

a) all required flue gas ducts and special-shape sections including all necessary tie-in points, fittings, flaps, dampers, expansion joints, insulation and cladding;

b) inspection facilities with all necessary stairways and platforms, access doors, manholes and openings for maintenance, isolating flaps and dampers, safety grips and handles for internal inspection;

c) supporting structure;

d) sealing air systems with heating of the sealing air (where necessary);

e) silencers in order to keep the noise emission values;

f) drivers, geared motor drives, actuators for all flaps and dampers; and

g) connection to flue gas recirculation system (as required);

(4) induced draught fan comprising as a minimum:

a) fan with vibration damper system, coupling with protection cover and base frame for fan and motor;

b) bearing temperature or vibration measurement equipment;

c) all measures and systems for vibration damping and noise level reduction;

d) electric motor with frequency speed control;

e) auxiliary drive;

f) spare motor for the induced draught fan;

g) all necessary measures to prevent excessively low or high pressure in the flue gas treatment plant; and

h) be of a proven design with units of similar impeller tip speeds and duties operating successfully for a number of years;

(5) complete equipment for handling, storage and loading of residues for the FGT line, comprising as a minimum:

a) one silo for reaction product for [5] days capacity at consumables basis plus boiler ash (in case future legislation prevents combination of bottom and boiler ash);

b) suitable discharge system with fluidising equipment, discharge sealing, feeding arrangement and rapping gear (if required), with the system designed in a proven manner which reduces the potential for blockage;

c) all conveying equipment between filter or hopper outlet and the relevant silo and between the silo and the consumer as screw conveyors and/or drag link conveyors, pneumatic conveyors (with blowers if necessary), motors, piping and fittings;

d) venting device with the bag filter with pulse jet cleaning controlled on high differential pressure;

e) safety systems to protect against excess pressure and vacuum;

f) continuous filling level measurement;

g) metering equipment for product;

h) equipment for cleaning of loading equipment;

i) steel structure with operating platforms, stairways, etc.;

j) clearance around the loading bay to enable deployment of collapsible safety rails on the top of the tanker;

k) internal piping including all necessary valves etc.;

l) local operating cubicles;

m) equipment for dry loading into sealed tankers (assumed capacity is 64 m3), including displaced air return system and overflow protection; and

n) facilities for safely taking appropriate quantities of samples of the residues for off-site testing.

(6) one dry-lime reception, storage, handling and conveying system, comprising as a minimum:

a) one unloading station for lime with all systems required for unloading and conveying of lime from tanker vehicles to the silos located for ease of vehicular access;

b) typical vehicle capacity for supplying lime is up to 30 tonnes via a 6 axle articulated tanker (typical vehicle dimensions are 15.5 m length, 2.55 m width, 4.3 m height), with the design allowing for an outer turning circle of 25 m and a clearance required to tip the body of the vehicle of 10.7 m;

c) one lime silos with combined useful capacity for lime of

d) a minimum of 5 days of lime consumption plus one full tanker delivery;

e) with all necessary internals and equipment, such as for fluidising and discharge, manholes, safety systems to protect against excess pressure and vacuum, continuous filling level indicator, extraction air filter, gate valve, rotary valve, rapping gear (if necessary);

f) a metering system based on day bins with loss of weight devices;

g) a system for pre-coating bag filters for on-line start-up;

h) all conveying equipment between silo and the relevant surge hopper as screw conveyors and/or drag link conveyors, pneumatic conveyors (with blowers if necessary), motors, piping and fittings;

i) venting device with filter;

j) safety systems to protect against excess pressure and vacuum;

(7) a powdered activated carbon (PAC) supply system, designed for a minimum of one month’s supply capacity, comprising as a minimum:

a) one unloading station for PAC with all systems required for unloading and conveying of PAC in big bags from lorries to the storage area located for easy vehicular access;

b) typical vehicle capacity for supplying PAC is up to 30 tonnes via a 6 axle articulated lorry (typical vehicle dimensions are 15.5 m length, 2.55 m width, 4.3 m height) with the design allowing for an outer turning circle of 25 m with a clearance required to tip the body of the vehicle of 10.7 m;

c) one storage area, with useful size for of a minimum of 20 days PAC consumption plus one full lorry delivery; and

d) a metering system based on hopper with level transmitter.

6.2.2 Electrical equipment

The FGT system shall be complete in all electrical respects and shall include but not be limited to:

1) all necessary electrical drives and consumers;

2) for variable speed drives the drives shall include frequency converter with cabling and necessary material for motors, and, for motors in excess of 400 kW the transformers shall be supplied;

3) local control cubicles including cabling between cubicles and consumers, transmitters, limit switches and cable racks, protection pipes conduits etc.;

4) all necessary material for connection of the power supply cables, coming from the switchgear installations to the control cubicles and direct in-feed of electrical drives;

5) all electrical installation material, i.e. wiring and cabling material, all the necessary attachments, conduits, brackets and other supports, including the cable racks etc.; and

6) appropriate earthing of all steel parts.

6.2.3 Instrumentation and control equipment

The FGT system I&C system shall be integrated in the DCS, including but not limited to:

(1) control system using the common supervisory and control system;

(2) all measuring and signal conditioning equipment installed in the field as well as in the relay room and Plant control room;

(3) complete control equipment for all remote, manually or automatically controlled drives and other equipment in accordance with the operating conditions including all necessary safety interlocks and all necessary hardwired drive controls, etc., including the control functions incorporated in the digital control system and PLCs;

(4) all necessary field equipment;

(5) complete installation, cabling and wiring of all instrumentation and control equipment;

(6) supply of all necessary installation materials (cables, instrument racks, function boxes, terminal boxes, instrument piping, etc.) and auxiliary materials;

(7) local controllers including enclosures;

(8) local indicators and measuring devices;

(9) all tapping points and connectors for remote measurements as well as for acceptance and Performance Test measurements, including primary isolation for instrument lines;



(12) complete installation for all instrumentation and control devices, including wiring to the control system, piping where required including connection to the Plant compressed air system, all required attachments, electrical and mechanical isolation where required, conduits, junction boxes, brackets and other supports, including cable racks;

(13) control dampers or butterfly valves in the air and flue gas ducts with actuators;




(17) flow measurements to all media to put up a mass balance;


a) monitoring of HCl and/or SOx concentration in boiler exit gas for a co-ordinated feed forward/feedback control of lime dosing rate;

b) flue gas temperatures (for minimum/maximum temperature monitoring);

c) pipewall temperatures;

d) speed measurements including electronic (e.g. at screw conveyers, belts etc.);

e) weight measurements;

f) hardwired logic or SIL-rated PLC for critical events and sequences including all necessary provisions for events, trips and emergency shut-downs;

(19) local controls, for example, for the following systems:

a) FGT protection;

b) bag filter cleaning;

c) compressed air system;

d) utility unloading;

e) residue loading;

f) conveyor control; and

g) trace heating;

(20) other controls which in the opinion of the bidder would best be executed as local controls;

(21) specification of signals exchanged between these systems and the main supervisory system, as well as their integration;

(22) specification of drives for connection to the emergency power supply and UPS; and

(23) all necessary software including control logic, operator interfaces, mimics and trending in accordance with the DCS philosophy.


The Contractor shall complete the technical data sheets and include these as part of his tender proposal.

6.3.1 FGT system

Irrespective of the technology used for the FGT system there shall be duplicate run and standby equipment as necessary to meet the Availability Guarantees and through life performance requirements. Storage capacity for reagent and production of residue shall be provided.

The FGT system shall be designed to operate within the emission limits specified in the Industrial Emissions Directive and the Environmental Permit with the Plant operating at up to 110% MCR and over the full specified range of pollutant concentrations in the raw gas.

It is noted that the boiler may be fitted with flue gas recirculation for the purposes of reducing emissions and improving efficiency. If this is the case, the FGT system design shall take into account the additional flue gas flow rate and the requirement to re-circulate clean flue gas after the fabric filter.

The FGT stream shall be designed for the input conditions shown in the following tables:

Table 2 - Technical data sheet – FGT design input conditions

Parameter Minimum Consumables basis

Maximum

Flue gas flow, Nm3/h wet,

expressed as percentage of flue gas flow-rate at 100% MCR with Design Fuel:

70% 100% 120%

Flue gas temperature range as boiler design as boiler design as boiler design

Table 3 - Technical data sheet – flue gas analysis range at the boiler exit

Substance Minimum Consumables basis

Maximum

Gas analysis and pollutants, mg/m3 @ reference conditions, 101.3 kPa, 273 K, 11% oxygen, dry gas

in accordance with the Industrial Emissions Directive.

Flue gas moisture, % v/v wet gas 8% Design fuel and boiler oxygen at guarantee condition

25%

Flue gas oxygen, % v/v dry gas 6% According to boiler According to boiler

Mercury, mg/Nm3 0.3

Cadmium + thallium, mg/Nm3 1.5

Antimony, arsenic, chromium, cobalt, copper, lead, manganese, nickel, tin and vanadium (total as sum of elements), mg/Nm

3

100

Acid gases1

Hydrogen fluoride, mg/Nm3 0 15 50

Hydrogen chloride, mg/Nm3 400 900 1,700

Oxides of sulphur as sulphur dioxide, mg/Nm

3

40 150 600

Particulates at FGT inlet (max whilst cleaning) mg/Nm

3

3000 8,000

Dioxins, ng/Nm3 (I-TEQ) 5

The Plant shall achieve the required emissions performance at all conditions listed in the tables.

The service and instrument air requirements of the flue gas treatment plant shall be provided from the central compressed air facilities for the Plant which shall have sufficient stand-by capacity to meet the Availability Guarantees and through life performance requirements. A local air receiver shall have the capacity to store a volume of air sufficient for 3 pulse cycles of the bag filter system.

PAC shall be powdered activated carbon with the typical properties given in section 6.3.12.2. The system shall be designed so that PAC is injected into the flue gas steam upstream of the lime injection points so that the initial environment for the carbon particles is acidic.

The PAC system shall automatically accommodate any requirement for increased consumption during boiler start-up when carry-over of released organic material may occur.

Particular regard shall be given to low emissions, energy efficiency, optimal use of materials, recovery, treatment, and reuse of process effluents, and minimisation of towns water consumption.

The flue gas treatment plant, as well as the facilities for residue and reaction product treatment including all necessary auxiliaries, shall be designed, manufactured, erected and operated in accordance with:

(1) current, state of the art technology;

(2) minimised operating costs;

(3) optimised operation in connection to the items of equipment of other lots, in particular the combustion, the boiler, etc.;

(4) simplified observation, supervision, maintenance and repair; and

(5) a minimal number of operational staff.

The FGT system shall have upstream measurement of acid gases which allows on-line predictive control of reagent dosing.

1 The Consumables Basis defines the acid gas concentration in the raw gas for the purposes of guaranteeing the maximum consumption of lime at reference conditions of 101.3 kPa, 273 K, 11% Oxygen, dry gas in accordance with IED.

In order to be compatible with total Plant operation, the design of the FGT system shall guarantee a rapid availability in the course of the start-up procedure with start-up times which do not increase the overall Plant start-up time. The FGT system shall respond to load fluctuations or changes in conditions due to fluctuations in the fuel without limiting Plant operation and in a reliable manner.

In particular the following operation characteristics shall be possible.

The FGT system and the ancillary facilities shall be suited to an unlimited operation at any load point on the furnace Firing Diagram (see Specification Part A). This requirement also includes that the FGT system can be put into service by both warm and cold start-up procedures without the necessity of extensive and unusual activities or preparations. In particular the plant has to be suitable for an unlimited operation at any value of the pollutant concentrations between minimum and maximum value without exceeding the required and guaranteed emission values.

The FGT system shall be started up under fully automatic control. The pre-heating time for the FGT system prior to starting shall be within the overall Plant start-up time.

The system shall be designed such that the bag filter is not required to operate with a bypass during start-up or shut-down.

In the case of a failure of an item of equipment (e.g. pumps, etc.) the stand-by unit shall be activated and put into service automatically without delay and without interruption of the Plant operation. Stand-by units shall be provided if the unit being in service is an important one and is compulsory for the Plant operation.

In case of failure of the associated combustion chamber and boiler, the FGT system shall be brought automatically to the off-load condition.

The baghouse filter shall be adequately designed with sufficient number of compartments so that any compartment can be isolated and accessed for bag replacement and other tasks whilst the boiler is operating at 110% MCR within the guaranteed emission limits.

There shall be leak detection facilities for automatically identifying to the operator which filter compartment is the source of a dust leak.

Pumps, especially for corrosive media, shall preferably be equipped with magnetic couplings.

No item of equipment subject to pressure shall be made of grey cast iron without the agreement of the Project Manager. The materials used shall be suited and designed adequately for the operational conditions. Castings may not show flaws which affect reliability or life.

The minimum wall thickness for filter casings, absorbers, reactor vessels shall be 6 mm unless the Contractor can demonstrate to the satisfaction of the Project Manager that sufficient corrosion allowance is available when using thinner wall thickness. The minimum wall thickness for flue gas ducts, silencer casings, etc. shall be 5 mm plus the corrosion allowance unless the Contractor can demonstrate to the satisfaction of the Project Manager that sufficient corrosion allowance is available when using thinner wall thickness.

All valves, fittings and flaps necessary for an automatic mode of operation or for a change-over procedure shall be equipped with pneumatic or electrical actuators.

Manholes and inspection openings shall be provided in sufficient number for access, cleaning, maintenance and inspection of all gas passages, vessels and containers. Dimensions for manholes shall take into account the HSE ACOP for confined spaces (L101). As a minimum, all manholes shall conform to the following requirements.

All manholes shall have a minimum diameter of 800 mm.

On tanks, silos and towers which could contain lime or lime residue, an access of at least 800 x 1,000 mm shall be provided at low level to facilitate ease of cleaning out.

Other access and inspection openings must be provided with a minimum inlet area of 0.5 m², simultaneously showing a minimum lateral length of 600 mm.

If possible, the bottom edge of all manholes shall be at a minimum 500 mm above the foundation or platform level.

All manholes and inspection openings shall be hinged or shall be provided with a davit, and suitable to be opened/closed without problems throughout the Design Life of the Plant and of a design to allow future crack detection.

All inspection openings and manholes shall be provided with maintenance platforms for easy access.

Dust catchers shall be provided in order to prevent discharge of dust when opening the doors/manholes.

All items of equipment including flue gas ducts, expansion joints, etc. shall be designed taking into account thermal and mechanical strength as a function of the maximum temperature which might occur in case of a failure of the upstream equipment. Where expansion loops are not a feasible solution, bellows shall be used to absorb thermal expansion displacement. Bellows shall be specified with flange connections.

Sufficient tapping points for sampling and measurements shall be provided within the scope of supply at adequate points in sufficient number to be able to carry out all necessary measurements. As a minimum dust sampling shall be possible at the dust collection hoppers of the spray absorber and at the hoppers of the filters. As a minimum gas sampling and temperature monitoring shall be possible between all main items of equipment.

The tapping points for emission measurements shall be located in accordance with Environmental Agency requirements and shall be isolated from the ducting to avoid vibration. The housing for the emission measurement equipment shall be accommodated near the chimney at ground level or at an alternative location agreed with the Project Manager.

Operation and supervision of the FGT system and the ancillary facilities (including any required treatment of residues) shall be carried out fully automatically from the Plant control room. If necessary the Plant control room staff shall intervene and control the FGT system. Start-up and shut-down procedures shall be possible by means of automatic mechanisms which shall be released and supervised by the Plant control room.

A predictive control system shall use the HCl and SOx concentrations in the raw flue gas and in the treated flue gas to regulate the lime dosing rate in order to minimise lime consumption and residue production whilst providing rapid response to changes in the concentration of acid gases in the raw gas.

The whole area of the FGT system shall be bunded and piped to adequate storage. Where required by Environment Agency guide lines, blind bunds shall be provided with a sump suitable for use with a sump pump.

Under normal operating conditions, the bunded area shall be piped directly to the effluent tank.

All items of equipment including the flue gas ducts shall also be designed to the minimum and maximum operating pressures in case of a failure, taking into consideration a design reserve.

Where necessary to prevent the formation of condensate stemming from the high humidity of the flue gas, the plant shall be equipped with a trace heating system and an adequate thermal insulation shall be provided in order to achieve a minimum skin temperature to prevent acid dew point corrosion and clogging of the hopper. Cold spots shall be avoided.

Where necessary for plant external to the main Plant building, silos, transportation and feed systems, including piping and ducts shall be suitably lagged and clad, and trace heating shall be used where necessary.

Trace heating of equipment shall be done electrically. The trace heating shall be under thermostatic control.

6.3.2 Spray absorber or reaction tower (where used)

The spray absorber or reaction tower, where used, shall be designed such that encrustation, deposits, fouling and corrosion will be avoided. Despite this, any encrustation which might occur at the reactor casing shall not exceed an amount which requires a shut-down of the FGT system within the guaranteed continuous operation period. Otherwise adequate on-line cleaning devices have to be installed.

Overall dimensions (e.g. height and volume) as well as atomising devices and auxiliary equipment of the spray absorber have to be designed in order to evaporate the sprayed waste water completely without encrustation and/or crystallisation at the spraying device and to dry the residues contained in the water reliably within the reactor casing over the total load range. Carryover of water droplets and of wet residue/reaction product particles, i.e. particles which are not dried completely, to the downstream equipment shall be avoided.

The reaction tower (where used) shall be designed as a gas-tight welded steel construction including the required reinforcement steel sections. The spray absorber shall be designed with adequate mechanical strength to withstand the highest temperature possible caused by a failure of the water supply lasting for an extended period.

Materials being used for spray absorber and atomising devices (where used) shall be selected in order to minimise abrasion and wearing and to prevent corrosion. In order to increase the service life, items of the atomising device and sections of the gas distribution system which are in contact with reaction products shall be made of stainless steel type No. 1.4571 or equivalent.

The angle of gradient of the dust collection hopper (if applicable) shall be designed in order to avoid solid bridges during discharge. The dust collection hopper and parts of the casing (if necessary) shall be equipped with a trace heating device. The trace heating device shall be designed in order to exclude the risk of condensation and agglomeration at the minimum ambient temperature. The dust collection hopper shall be provided with staggered level control devices, which allow for staggered level switches for open-loop control and alarm.

The outlet reactor temperature shall not fall below the minimum temperature required for safe operation. For effective flue gas temperature control a quick change of the mass flow rate of injection water must be possible. If necessary a dilution bin shall be provided for this purpose.

6.3.3 Atomiser

For the purpose of atomising, either purpose-built nozzles or an atomising machine can be used. However, the atomising devices shall be suitable to atomise suspensions containing a solid portion (dissolved solids and suspended solid portion) as well as liquids free of a solid portion.

Atomising devices, dilution bins (if necessary), connecting pipes and all other equipment being in contact with lime slurry shall be equipped with a device for flushing by process water and compressed air. Flushing must be possible during operation of the FGT system.

If a rotating machine is used as the atomising device, a rotating disc, preferably made of titanium, equipped with replaceable inserts made of a suitable material e.g. tungsten carbide shall be used in order to fulfil the required continuous operation period.

The atomising device has to be designed in order to avoid rapid erosion, encrustation or plugging. The design target for the life service of nozzles shall be at least 1000 hours.

A method detection of failures of individual nozzles shall be provided. Maintenance and replacement of atomising devices shall be possible during full load operation of the FGT system.

The design target for the service life of the rotating disc (i.e. period between two maintenance procedures, e.g. for cleaning, shall amount to at least 2000 hours. All necessary monitoring instruments (vibrations, unbalanced mass) and flushing equipment shall be provided.

The atomising device shall be designed in order to guarantee an even distribution of the sprayed fluid and of the flue gas temperature over the flue gas section area within the absorber casing.

If a rotary atomiser is used, a separate electrically driven hoist or trolley shall be provided to allow rapid replacement. In addition an identical stand by unit shall be provided, together with all necessary support frames and transportation. This equipment must be suitable for transport of the stand-by atomiser to either spray absorber without the need for any further equipment.

Both the spray absorber with platforms and the necessary hoist or trolley have to be designed and arranged such that speedy replacement of the atomising device will be possible during operation of the FGT system. Adequate working areas, lay-down areas and tools for a safe replacement during operation shall be provided.

6.3.4 Fabric filter

The fabric filter shall be so designed that it will be possible to employ a choice of either pure activated carbon dust or a mixture of activated carbon and other materials (e.g. Ca(OH)2 as adsorbent agents). The adsorbent injection equipment, for example an entrained suspension reactor, shall be so designed that it will be possible to mix the above into the flue gas stream. Thorough mixing of the adsorbents and distribution to a uniform composition in the flue gas stream over the entire load range shall be possible. It shall be possible to exchange adsorbent injection nozzles during operation of the fabric filter. By installing a suitable number of nozzles, it shall be possible to generate the required adsorbent density in the flue gas ahead of the fabric filter. Rapid wear, encrustation and plugging of the nozzles shall be avoided. The possibility of caking shall be prevented by suitable design measures.

The inlet and discharge ducts shall be designed to ensure good distribution of the gases across the entire filter and to avoid excessive local turbulence and/or abrasion as well as dead spots. Particular attention shall be made to the design of the system to avoid ‘hot spots’ within the baghouse due to local concentrations of carbon or combustible material.

The baghouse structure shall be designed to avoid thermal bridges. Supports shall be by means of insulating isolation blocks. Where conductive paths are unavoidable, special attention shall be paid to the trace heating at such points to ensure that acid condensation does not occur.

The plate thickness of the baghouse filter shall be not less than 6 mm unless the Contractor can demonstrate to the satisfaction of the Project Manager that sufficient corrosion allowance is available when using thinner wall thickness.

The fabric filter and the adsorbent injection equipment housings shall be provided with adequate numbers of access doors and inspection ports. These shall be fully gas-tight and readily accessible from the platforms or from specially provided landings.

The filter unit shall be designed to operate at all specified continuous operating conditions with one compartment safely isolated for maintenance or bag replacement. In the event of outage of one compartment, it shall be possible to treat the full flue gas flow (at the maximum specified flue gas flow rate) in the remaining compartments, without exceeding the guaranteed emissions, although it is recognised that the period of such operation should be minimised.

Filter material shall be P84 Teflon coated or better.

Filter cages shall be stainless steel (or other corrosion-resistant material) approved by the Project Manager and one-piece where space for withdrawal permits.

Further, by adequate dimensioning of the filter surface area, the specific load of the filter material shall be kept to a low value to extend the bag filter service life time.

By employing trace heating, for example at the hoppers, caking and deposits shall be prevented, in particular during periods of non-operation or during start-ups and shut-downs.

It shall be possible to replace bags as necessary during operation, at acceptable working conditions for the personnel involved. A penthouse shall be provided with lifting equipment suitable to remove the single piece filter cages.

Multiple level probes shall be arranged in the discharge hoppers of the fabric filter in such a way that bridging of adsorbent can be detected.

The quantity of spent adsorbent temporarily stored in the hoppers shall be minimised by emptying the discharge hoppers of the filter continuously.

There shall be a pre-coating system for pre-coating the filter bags with hydrated lime and activated carbon prior to start-up. For start-up, the activated carbon ratio should be higher than that required for normal operation in order to ensure that organic compounds released from the boiler during the warm-up are captured.

In order to reliably prevent condensation on the filter bags or within the baghouse casing or hoppers during start-up of the FGT system and after shut-down, equipment for preheating the entire baghouse to an adequate temperature before flue gas is admitted shall be provided and also of maintaining the baghouse temperature after a shut-down. For start-up the fabric filter shall be equipped with a heating system capable of preheating the filter to operational temperature within 16 hours.

The bag filter shall be provided with reverse cleaning jets for cleaning. The cleaning jet system shall be a low pressure, high flow design. The cleaning system shall be automatically controlled by a local controller of standard design. The cleaning shall be automatic and based on differential pressure across the bags with the option to manually clean or to set a timer. The cleaning sequence shall be designed to avoid irregular pressure drop distribution across the filter house. It shall be possible to initiate a cleaning cycle on an off-line compartment.

It shall also be possible to start, stop and restart the cleaning sequence. The cleaning sequence shall be programmed so that, if interrupted, the cleaning sequence should restart where it stopped.

The reverse jet cleaning shall be controlled to provide a ‘soft landing’ for the bags on deflation in order to avoid violent collapse of the bags onto the cages and prolong the life of the bags.

6.3.5 Adsorbent supply

The supply of powdered activated carbon (PAC) adsorbent will be by road in big bags.

When handling fresh adsorbent, the relevant safety regulations for protection against fires and explosions shall be observed, as well as those for the prevention of dust releases and for protection of the personnel. A DSEAR assessment shall be carried out.

All conveying, storage and temporary storage equipment in connection with adsorbent handling shall be so designed that the possibility of condensate formation is reliably excluded, and no dust will be released.

Conveying lines shall be designed for ease of access and ease of changing. Critical lines on common services shall be provided with duplicate lines and a simple change-over facility.

Mechanical conveying of adsorbent will also be allowed.

6.3.6 Silos and hoppers

Each silo shall be designed in accordance with the requirements of its application. In particular the following constraints, which shall also apply to hoppers where appropriate, shall be fulfilled.

(1) Silos shall be provided with at least one manhole each.

(2) A “high level” alarm shall sound local to the tanker and in the Plant control room. A further “high-high level” alarm triggered by a separate sensing device shall sound in the Plant control room and local to the tanker. The high and high-high level alarms will remain on and sounding until the tanker discharge has been stopped.

(3) The silos shall be designed based on the UK codes of practice. The silo filters shall be designed as textile filters. The closure cover shall be designed as a pressure relief valve. The release shall be into a restricted controlled area (e.g. not a walkway or regularly visited area). The filters shall be designed to achieve permitted dust emission levels or the filtered air shall be ducted to upstream of the FGT system. For maintenance of air discharge filters etc. and in order to provide access to the silos, stairways and platforms in the area of the silos shall be provided as needed.

(4) The powdered lime storage silo should have the filling pipe entering tangentially near to the top.

(5) The silo filters should be weatherproof and watertight and the filter material should be capable of being automatically cleaned using controls which are located at ground level. The preferred method for filter cleaning is reverse jet pulse compressed air. Low pressure air is unsuitable for filter cleaning.

(6) Silo manholes shall have a grid fitted for safety during inspections.

(7) Silo manhole covers should be hinged and easily opened and form an air tight seal when in a closed position. The hinge position must ensure that the operative does not lean over the opening to open or close the cover.

(8) Silos should be fitted with a high level indicator which is known to operate effectively with material being stored. This indicator should be linked to an audible and visual alarm at ground level where the operator of the effecting discharging vehicle can see and hear it above background noise.

(9) Silos shall be equipped with adequate earthing connections.

(10) A system should be installed to prevent loading of the silo unless the high level indicator is working.

(11) A notice to the operator of the discharging vehicle should explain the nature of the alarm and instruct him to stop the discharge upon operation.

(12) A handrail must be fitted around the top of silos.

(13) A continuous filling level measurement should be installed on all silos. This should indicate “full” before the reactant/product can reach a level in the silo at which damage would be done to the silo or equipment fitted to the silo.

(14) The high level measuring device should be shielded to prevent it being affected by the entry of the reactant to the silo.

(15) The high level measuring device on the powdered lime silo should be located 0.6 metres horizontally away from the cone apex of the lime. This distance should be measured on the side of the cone where the natural angle of the product is not interfered with by the silo wall or any other part of the structure.

(16) The high level measuring device in the powdered lime silo should be located at least 1035 mm from the lower edge of the filter socks/elements. This represents the maximum allowable lime level within the silo.

(17) The silos shall be equipped with reliable measuring equipment which shall also be used for remote display purposes.

(18) In order to avoid bridging of the silo content in the hoppers, fluidising equipment of a proven design shall be provided. The Contractor shall make his proposal as to how to control the loading of the transportation vehicles.

(19) Hopper gate valves shall be provided at silo discharges. Where necessary to prevent blockages, caking, etc., silos for storing adsorbents, residues or reaction products which are strongly hygroscopic, or which tend to form clumps or caking deposits, shall be provided with heaters and thermal insulation. Additional suitable measures of proven design shall ensure that caking deposits will be reliably prevented.

6.3.7 Conveying equipment

When conveying APC residues or other products, short transportation routes are desirable. Mechanical conveying is preferred wherever possible. Where pneumatic conveying is used the design should ensure that significant wear or abrasion is avoided. During conveying, no fugitive dust emissions shall occur. Pneumatic conveying equipment shall, when necessary, be equipped with a pre-heater for the conveying air, for example using electrical heating or steam heating. Conveying lines and equipment for handling filter residue shall be trace heated.

Suitable measures shall be taken to ensure the maximum service life of the conveying equipment. Where using drag link conveyors, the design shall have been proven in similar applications and incorporate two chains with high quality seals. When selecting material for the conveying equipment, due account shall be taken of the need for resistance to corrosion and wear. In particular, pipe bends and specially shaped pipe sections in the pneumatic conveying lines shall be provided with appropriate lining (e.g. cast basalt), or their geometry shall be such that no wear which could adversely affect operation will occur. The use of lining shall be minimised.

The conveying equipment shall be so designed that neither deposits nor wear will occur to an extent which could adversely affect operation. Rinsing and air purging equipment for conveying lines shall be provided. Particular attention shall be paid to the use of suitable materials, e.g. rubber for specific pneumatic conveying lines.

For all products to be handled in the FGT system the conveying equipment and the receiving tanks, bins or silos shall be designed and equipped so that conveying of material and supply to the different consumers from one line (if duplication of silos etc. is used) to the other line is possible without the need of a shut-down of the FGT line in case of an outage or a failure of the conveying and handling equipment.

The floor beneath ash conveyors shall be designed to prevent ash from the conveyor falling through the floor during maintenance.

6.3.8 Flue gas system

Flue gas ducts shall be designed for the maximum and minimum pressures occurring within the system (including during upset conditions) with safety allowance of minimum 10 mbar.

Consideration of accident conditions shall also include unintentional blocking of flue gas ducts.

Flue gas ducts shall be designed with regard to gas flow rate and strength for the temperatures quoted in the relevant clauses. Duct routing, its shape and internals, e.g. flow guiding baffles at bends, etc. shall be optimised to reduce the pressure drop.

The system shall be designed so that no dust deposits which could adversely affect operation or durability will arise in the flue gas system.

Floor areas beneath duct openings shall be designed to prevent particulates from the duct falling through the floor during maintenance.

Flue gas ducts shall be of steel plating of adequate strength to withstand all load conditions, and shall be of welded construction.

Flue gas ducts shall be equipped with adequately dimensioned and appropriately located cleaning and inspection ports.

Instrument connections and sampling devices shall be provided to permit a full range of measurements.

Flue gas ducts shall be constructed of steel plates at least 5 mm thick unless the Contractor can demonstrate to the satisfaction of the Project Manager that sufficient corrosion allowance is available when using thinner wall thickness. Duct reinforcement can be of flat steel, and connections shall be made by means of gastight-welded angle iron joints. Thermal expansion shall be accommodated by means of expansion joints with an internal guide plate. The ingress of air-borne ash into the expansion joint volume shall be prevented.

Ducts shall be routed such that satisfactory condensate drainage is ensured. Corrosion during FGT system outages in the flue gas ducts shall be avoided by taking suitable measures. Where possible, ducts may also be supplied in fibre-reinforced resin.

As well as the normal operation, the flue gas ducting system shall permit:

start-up and shutdown of the combustion chamber via the FGT plant;

diversion of purging air from boiler cleaning via the FGT plant; and

ease of removing blockages by the provision of suitable maintenance and cleaning doors.

Isolating dampers shall be of the louvre type. Expansion joints shall in general be provided with telescoping plates, to prevent dust deposits in expansion joint corrugations. The installation of dampers and expansion joints in each of the duct sections shall be by means of bolted flange connections. Where isolation is for the purposes of maintenance, the dampers shall be slide dampers with 100% gas-tight seals unless otherwise agreed with the Project Manager.

Replacement of expansion joints shall be ensured by a suitable arrangement.

The space between double isolation dampers shall be connected to the sealing air system (minimum sealing air pressure 50 mm wg). They shall always exhibit the required degree of leak tightness and shall be so designed that they will reliably function even should the operating conditions become more arduous. Limit switches and pressure monitors for sealing air shall be provided. If necessary, sealing air shall be pre-heated.

For dampers, special measures are to be taken to reliably prevent unintentional blocking of the flue gas duct. This applies also for a complete power failure and all other conceivable upset conditions. The design shall ensure that auxiliary power for actuating the dampers will always be available.

Filter bypass ducts are not permitted.

6.3.9 Induced draft fan

The location of the induced draft (ID) fan shall be optimised by the Contractor taking into consideration the design pressure of the flue gas system and the related equipment, the electrical power consumption as well as operating problems and the service lifetime of the fans taking into account corrosion/erosion.

The ID fan shall be sized so that, with:

1) the boiler operating at 110% MCR in a fouled condition after 7500 hours of operation;

2) fuel of any NCV within the 100% MCR range on the Firing Diagram; and

3) with not less than 8% oxygen (dry v/v) in the flue gas,

the speed of the ID fan is less than 80% of the maximum speed for which the fan is designed for sustained operation.

The Contractor shall submit pressure drop calculations through the boiler/FGT system to demonstrate compliance by design.

The fan shall be equipped with an electric drive and flexible coupling ideally mounted on a common frame for fan and motor. Suitable vibration dampers shall be provided.

The shaft shall be made of forged steel. The first critical speed shall be well above the maximum running speed. The impellers shall be statically and dynamically balanced.

All equipment required for noise reduction shall be included. Noise abatement fan casings shall preferably be prefabricated. Acoustic insulation and cladding shall be provided. Any fan housing shall be provided with one inspection door on the suction side and one on discharge side. In the flue gas duct silencers (if required) shall be installed at suitable locations.

The bearings provided shall be roller bearings only, with special seals to prevent the ingress of dust and with remote indicator thermometers and alarms. The bearing houses shall be equipped with vibration measurement devices. The fan shall be of a proven design with units with similar impeller tip speeds in similar service operating successfully for a number of years.

A certain content of solid particles and/or droplets in the flue gas with subsequent fouling and unbalance of the impeller shall be taken into consideration. Therefore, the fan and impeller shall be so installed that maintenance, in particular cleaning and replacement, are simple and quick. A suitable system for maintenance and removal shall be provided for each fan and drive for motor and impeller removal.

The Contractor shall ensure that, in loss of power conditions, there is a proper discharge of fumes out of the combustion chamber system and building. If this requirement is fulfilled with an emergency drive on the ID fan, it shall be supplied by the emergency power system, not by the UPS system. The control shall handle failures of the main drive as well as the power failure situation (short term cuts and long term cuts with emergency supply). Due to the nature of the diesel based emergency system, the emergency power will not be available instantaneously.

The ID fan shall be equipped either with:

a normally open manual damper to allow exhaust gas to pass to the chimney; or

an auxiliary drive motor for control of furnace draft on a Plant trip.

6.3.10 Control and monitoring equipment

All necessary operational controls, regulating controls, automation measuring and monitoring required to cope with the equipment duty shall be so designed and arranged that operation of the FGT system can be fully automatic or, if required, manual. All necessary interlocking and alarm circuits shall be arranged as to eliminate any possible damage to the Plant or the FGT system due to malfunctioning of instruments or any probable operational mistakes. Technical features of the controls and instruments shall comply with the applicable requirements elsewhere in the Specification.

The control and monitoring equipment shall be provided as far as required for safe and satisfactory operation and supervision of the FGT system. Adaptation of the specified scope and design of the control and monitoring equipment shall be done where needed for matching the special versions and requirements of apparatus and plant equipment. The equipment shall communicate with the DCS.

All flue gas control, start-up, shut-down and emergency sequences shall be fully automatic.

An automatic logging facility for all FGT system parameters is to be provided.

All analogue and digital measured values, conditions, status and control signals shall be logged by the control system.

The control system shall continuously monitor, record and display:

the flue gas mass flow-rate at the reference conditions required under the IED;

flue gas conditions including moisture content after the FGT system;

HCl content of the flue gases at the exit from the economiser and before the FGT system;

the flow rate and accumulated consumption of all reagents;

the contents of all reagent and residue storage facilities including day-bins;

the water consumption of the FGT system (including any direct water injection and slurry water);

emission alarms; and

dust alarms from the venting side of bag filters on storage silos for solid materials.

6.3.11 Reliability

The FGT system shall be designed to maximise availability and avoid plant shutdowns. The FGT system shall be designed to operate within the design range at all times when the Plant is in operation.

The maximum number of planned shut downs are:

one main shut down for repair, statutory inspection and cleaning; and

not more than one short inspection shut down per year.

The planned FGT shutdowns shall occur within the planned boiler and combustor shutdowns.

The FGT system shall be designed to minimise unplanned outages.

6.3.12 Basis for calculation of consumables

The Contractor shall provide a system which is designed to be operated using consumables from credible UK-based suppliers. Consumables should be calculated based on the typical specifications indicated below:

6.3.12.1 Hydrated lime

Where the proposed system will use hydrated lime as a consumable, the system shall be designed, and all relevant guarantees, shall be based on assuming a typical lime specification as set out in Error! Reference source not found..

If the calcium hydroxide content is lower than specified in Error! Reference source not found., hen the only permitted change to the guarantees shall be that consumption of lime (calcium hydroxide plus contaminants) may increase on a pro-rata basis to make up for the shortfall in calcium hydroxide content.

If the Contractor wishes to amend or add to the lime specification contained in Error! Reference ource not found. then this must be agreed in advance with the Purchaser and included in the contract prior to contract award.

6.3.12.2 Activated carbon

For systems using powdered activated carbon (PAC) the system shall be designed using the typical specification given below.

Table 4 - Powdered activated carbon (PAC) typical properties

Internal surface area (B.E.T.) 650 m²/g

Iodine number 600 mg/g

Static CTC 30-40 %

Particle size 90 %w/w through USS 200 mesh

Apparent density 0.3-0.45 g/cm³

Moisture content <10 %w/w as packed

The use of coke will not be permitted.

6.3.12.3 Correction to design conditions

The Contractor shall submit stoichiometric correction curves relating the consumption of reagents to the input and output conditions with respect to acid gas concentrations and flue gas volume, temperature and moisture content.

7 Continuous emission monitoring system


All items under the scope of supply should conform in every way to the relevant and latest British and European standards, codes of practice, regulations and laws applicable to the continuous emissions monitoring system (CEMS), including but not limited to:

Industrial Emissions Directive (2010/75/EU) – (IED);

BS EN 14181: Stationary source emissions;

EA Technical Guidance Notes M1 Sampling Facility Requirements for the Monitoring of Particulates in Gaseous releases to Atmosphere; and

EA Technical Guidance Notes M2 Monitoring Emissions of Pollutants at Source.

The Contractor shall ensure that the emissions monitoring system is compliant with the Planning Permission, the IED and the Environmental Permit, meeting all requirements for continuous monitoring in normal and abnormal conditions.

All analysers shall be certified under the Environment Agency MCERTS scheme.

Sampling and analysis of all pollutants as well as reference methods to calibrate automated measurement systems shall be carried out to CEN standards. If CEN standards are not available, ISO standards, national, or international standards which will ensure the provision of data of an equivalent scientific quality, shall apply.

7.2 Scope of supply

The Contractor shall design, deliver, install, integrate and commission, test and certify a complete CEMS including but not limited to:

(1) a CEMS for each stream of the Plant and one extra CEMS which can be automatically switched within [10] minutes from standby to duty for any stream so that the Plant can continue to operate in the event of failure of one of the emission monitoring or extraction systems, and including the sample train (inc. conditioners and converters), analysers, data logging and reporting system, control system and other equipment required and surrogate measurement for dust, CO and TOC shall be provided if required to prevent the stream from having to shut down to comply with any permit requirements;

(2) extraction probes, gas monitoring units, gas conditioning units and sample lines suitable for outdoor use and heated as necessary (alternative cross-duct system may be accepted if track record can be proven), with the ability to continuously measure all parameters listed in the IED as well as flue gas exit moisture and HCl concentration out of the economiser;

(3) all proprietary sample probes, instruments and reference sampling equipment required for the emission monitoring equipment to comply with all legislation requirements;

(4) additional insulation provided to the flue gas duct in the region of the sampling points taking into account the requirement for frequent access;

(5) housing for the gas monitors and associated equipment with air conditioning;

(6) an air-conditioned cabin to house the emissions monitoring system;

(7) suitable flanges for sampling probes, instruments and reference sampling on the clean flue gas ducts for the emission monitoring equipment;

(8) additional sampling points to allow non-continuous flue gas sampling in compliance with the IED as required;

(9) cable trays and fixing material for cables, lines, support structures for cables, sampling lines and housing;

(10) suitable access for to all equipment and sampling points including platforms suitably dimensioned and positioned to enable monitoring to be carried out easily;

(11) bottles of standard gases for the calibration of the analysers for each of the measured pollutants located in a suitable storage rack in an easily accessible area;

(12) data logging system providing logging and trending of raw data, and corrected data;

(13) provision to allow real time corrected emissions data to be displayed on a secure website;

(14) software package meeting MCERT requirements for evaluation and reporting to Environment Agency requirements including archiving, trends, QAL3 and mass emission calculations; and

(15) display and full access to CEMS output in the control room, the Plant manager’s office, the operation manager’s office and adjacent to the CEMS housing.


The Contractor is expected to utilise their specialist knowledge gained from the provision of emissions monitoring systems to reference energy from waste plants to provide a system that will comply with these requirements.

7.3.1 Sampling system

The monitoring system shall be located in close proximity to the chimney and at ground level, providing ease of access for local monitoring and maintenance.

The continuous emission monitoring system shall meet the requirements of:

(1) Environment Agency Technical Guidance Note M1 “Sampling Requirements for stack emission monitoring” Version 6 (Jan 2010); and

(2) Environment Agency Technical Guidance Note M2 “Monitoring of stack emissions to air” Version 8.1 (December 2011).

(3) Any additional requirements identified by the Environment Agency.

The design and installation of the analysers and sampling train shall ensure the entire system meets the requirements of QAL2 of BS EN 14181 including isokinetic sampling of particulates.

The monitoring system shall be able to continuously monitor CO, TOC and dust under abnormal conditions as defined in the IED.

The design and fabrication of sample ports shall ensure the requirements of the guidance and standards listed above are met.

The location of the emission monitoring sampling points and non-continuous sampling points shall be located according to the requirements of the Industrial Emissions Directive, BS EN 14181 and the EA Technical Guidance Notes M1 and M2.

The location of sample ports shall be selected to provide the best possible access. If the sampling points are to be located in the chimney, a suitable platform and access ladder must be provided together with hoist facilities for lifting equipment onto the sampling platforms.

Sampling ports may only be located in horizontal ducts if the Contractor can demonstrate that it is not reasonably practicable to locate them in a vertical duct.

Mountings are to be carefully designed to avoid vibration, alignment problems and damage under all operating conditions. Connections to ductwork are to be effectively purged by heating air to prevent condensation or contamination of the “cross-duct” equipment.

Two independent sample lines shall be provided to the duty monitoring system. The standby monitoring system shall be switchable to either sample line. Sample lines shall be of high-alloy steel and be supported appropriately.

Trace heating of extractive sample lines and condensate drainage points shall be used to prevent condensation where required.

The installed emissions monitoring system shall meet and exceed the availability requirements of the IED on the Plant stream.

7.3.2 Instrument requirements

The emission monitoring system shall be a cross-duct non-extractive or an extractive system.

All the instruments shall be of proven type and calibrated and checked in accordance with manufacturers’ instructions and recognised standards.

The analysers shall be certified under the Environment Agency MCERTS scheme for all measured components to meet the requirements of:

(1) “MCERTS Performance Standards for Continuous Emission Monitoring Systems” Version 3.1 dated July 2008;

(2) BS EN 15267-3:2007; and

(3) QAL 1 as defined in BS EN 14181.

The emission monitoring system shall include, as a mandatory requirement, continuous monitoring for:

dust;

sulphur dioxide;

hydrogen chloride;

carbon monoxide;

ammonia;

nitrogen oxides (NO and NO2, expressed as NO2); and

VOC as Total Organic Carbon (TOC).

In addition, continuously monitoring at the reference conditions required by the IED shall be carried out for:

water vapour content;

oxygen;

temperature;

pressure; and

flue gas mass flow.

The emission monitoring system shall include as an optional requirement continuous monitoring for:

hydrogen fluoride.

The analysers shall provide an additional independent output signal for comparison during QAL2 verification.

7.3.3 Local control

The emission monitoring system for the Plant shall be independent of the DCS and be equipped with its own processor, access terminal, control system, but shall be designed to integrate seamlessly into the DCS.

Analysers provided shall have the capability for auto-calibration of zero and span to meet the QAL3 requirements of BS EN 14181. Auto-recalibration shall take place at sufficient frequency to ensure continuous reliable operation within the required measurement tolerances. Manual recalibration shall not be required at less than one month intervals.

The analysers shall perform self-diagnostic functions and also allow remote access for diagnostics.

The local control interface shall provide password protection for several different security levels for data access and maintenance diagnostics.

In the event of failure of the duty monitoring system, the backup emissions monitoring system shall be capable of providing backup measurements within a period of fifteen minutes from the initial duty system failure.

7.3.4 DCS interface

All measured parameters and status signals shall be repeated to isolated analogue and digital output ports to be taken by the DCS system.

The system shall report the instantaneous emissions values to the DCS and the values of the current ten minute, half hourly and daily averages to allow approach to limit alarms to be set on the DCS.

The emissions monitoring system shall accept signals from the DCS to allow logging of plant status. As a minimum, logged signals from the combustion chamber shall include:

combustion chamber on/off;

combustion temperature;

oxygen content after combustion;

steam flow;

fuel feeder on/off;

auxiliary burner(s) on/off; and

fault condition.

Power and system failures of analysers shall be monitored and shall raise a group alarm per system. Maintenance and off-line recalibration shall be monitored.

Sample line flow and condensate alarms shall be repeated to the DCS if provided.

The reliability and response time of the system shall be sufficient to facilitate closed loop control of the lime feed system.

7.3.4.1 Data collection

The data logging and retrieval system shall be independent of the DCS. Readings of the various parameters defined in 7.3.2 shall be available from:

1) a local operator interface located close to the emissions monitoring system; and

2) a remote operator interface located in the Plant control room.

The operator interface shall be capable of displaying the various parameters from both the duty and the back-up system when in operation.

All measured parameters shall be:

3) recorded in an uncorrected format, where each parameter is time and date stamped with the appropriate flue gas conditions including temperature, pressure, oxygen content and moisture content; and

4) corrected to the confidence levels and reference conditions to which all continuously monitored measurements are corrected for the purposes of compliance with the requirements of the Industrial Emissions Directive.

The data logging system shall store at least one minute averages of the raw data as the basis for the half hourly and daily averages. A full back-up data storage system shall be supplied capable of storing one year’s worth of data. The system shall have the ability to download defined data to disc.

The data collection, processing, reporting and archiving system shall meet the requirements of “MCERTS Performance Standards and Test Procedures for Environmental Data Management Software” Version 2 dated September 2011;

Time and date stamping shall be provided by reference to a validated external source.

7.3.4.2 Report Creation

It shall be possible to extract all historical data to accessible files in spreadsheet compatible format. The time interval of interest shall be defined by the operator. The spreadsheet data, period and measurement interval selection, import and analysis functions shall be pre-programmable.

Reports shall be printed for each day, one per month, one per quarter and a yearly summary on an automatic basis. The reports shall comply with the requirements of the IED and the standard Environment Agency reporting requirements including:

half hourly average (for all parameters in 7.3.2);

daily average (for all parameters in 7.3.2);

mass emissions per day and summarising period (for all parameters in 7.3.2);

evaluation of valid / void data;

evaluation of percentile, minima, maxima and mean average; and

evaluation of operating hours of the combustion chamber, auxiliary burners and flue gas treatment system operation.

The software shall automatically generate the control charts and produce a report as required by QAL3 of BS EN 14181.

The software shall allow the option for data collected when no fuel was being processed to be separately stamped and excluded from the analysis for reporting purposes, but the raw data shall be maintained and archived for a minimum period of twelve months.

7.3.5 Ancillary equipment

7.3.5.1 Gas bottles

The facilities for safe storage of fuel and span gas bottles shall be supplied to comply with the latest best practice such as British Compressed Gases Association Guidance Note GN2 “Guidance for the storage of gas cylinders in the workplace” Revision 3 (2005).

Bottles of standard gases, traceable to ISO 17025, shall be supplied for initial calibration of the analysers for each of the measured parameters.

7.3.5.2 Equipment cabin

The emissions monitoring system, excluding the sample train, shall be housed within a secure, weatherproof, fire resistant cabin.

An air conditioning system shall be installed to maintain a stable air temperature at a level appropriate for the operation of the analysers. The system shall be set up to provide positive pressure within the cabin and shall include dust filtration.

Lighting levels within the cabin shall be appropriate for operation and maintenance of the equipment.

7.3.5.3 Uninterruptible power supply

The duty and standby emission monitoring systems shall be supplied by means of a hard wired uninterruptible power supply (UPS) with a minimum of 30 minutes of full-load capacity served by the emergency services section of the electrical distribution system. An indication of the condition (healthy/faulty) of the UPS is to be displayed on the DCS.

7.3.6 Design Life

The emissions monitoring system Design Life shall be a minimum of 10 years at the required functional and performance levels detailed in this section.

7.3.7 Environmental Agency connection

There shall be an Environment Agency ‘black box’ which will require a power supply, an independent direct telecoms connection and a 4-20 mA input for the raw value of each continuously measured parameter.

8 Steam turbine and generator


All items under the scope of supply should conform in every way to the relevant and latest British and European standards, codes of practice, regulations and laws applicable to steam turbine and generator, including but not limited to:

ASME TDP-1: Recommended Practices for Prevention of Water Damage to Steam Turbines Used for Electric Power Generation: Fossil-Fuel Plants;

BS EN 60034: Rotating electrical machines;

BS EN 60953: Rules for steam turbine thermal acceptance tests;

BS EN 61064: Acceptance tests for steam turbine speed control systems; and

ISO 10816-2: Mechanical vibration — Evaluation of machine vibration by measurements on non-rotating parts Part 2: Land-based steam turbines and generators in excess of 50 MW with normal operating speeds of 1 500 r/min, 1 800 r/min, 3 000 r/min and 3 600 r/min; and

IEC 60045-1: Guide to steam turbine procurement.

8.2 Scope of works

The Contractor shall design, deliver, install, integrate and commission, test and certify complete steam turbine generator set, and feed water systems designed for operation at 50 Hz. The Plant shall be designed with one turbine matched in size to the steam output of the single boiler line with a nominal capacity of 15MWe. The turbine shall have a separate steam / water cycle, complete with condenser. The following sections are applicable to the turbine generator set supplied, unless otherwise stated.

8.2.1 Condensing steam turbine

The turbine shall including but not be limited to:

(1) emergency stop valve(s), complete including piping between emergency stop valve(s), control valves and turbine casing (to the extent necessary);

(2) hydraulically operated governor valves for load control;

(3) steam blow out provisions and strainer as required;

(4) manual purge line with controlled and adequate drainage to allow rapid warm-up of the live steam line;

(5) extractions for the deaerator, the LP feedwater pre-heaters, combustion air pre-heaters and process steam where the Contractor may optimise the turbine design by applying controlled or uncontrolled extractions but must indicate clearly his selection and how the extractions will operate in each load case;

(6) one hydraulically operated emergency shut-off valve and one assisted check valve for each extraction or bleed in accordance with ASME TDP-1, both fitted with indicators to show correct operation;

(7) turbine bypass valve and suitable ducting for connection to the air cooled condenser (ACC) interface;

(8) steam strainer(s) for installation in the emergency stop valve(s) or including the separate housing for installation in the live steam line;

(9) one complete automatic turning device including manual turning equipment;

(10) one complete gland steam and sealing steam system, including a gland steam condenser and condensate drain control system;

(11) one complete warm up system and draining system, up to the vacuum flash tank;

(12) acoustic hood for the turbine generator including a complete ventilation system, as required;

(13) one complete inert gas or sprinkler-based (to NFPA 850) fire extinguishing system to meet the insurer’s requirements;

(14) complete noise and heat insulation;

(15) all interconnecting piping, fittings, safety devices, control valves and other equipment, fastenings, expansion joints, flanges etc.;

(16) turbine foundation;

(17) supplies and services for the turbine foundation, including at least:

a) turbine mounting to achieve the required vibration and noise levels;

b) the civil engineering design and erection work of the concrete foundation, including the concrete formwork and reinforcement;

c) all anchoring facilities for the turbine generator;

d) acceptance of the built-in reinforcement and anchoring before and after grouting;

e) the erection of the mounting under supervision of the turbine generator supervisor (as a minimum); and

f) all embedded parts and covering plates (e.g. sleeves for foundations bolts, conducted pipes, templates, embedded materials for support of piping etc.).

8.2.2 Generator including auxiliary equipment

The Contractor shall provide one complete generator system with auxiliary equipment including but not limited to:

(1) a generator-cooling system where the air-cooled systems should be enclosed to prevent dirt and dust fouling the system;

(2) the complete excitation plant;

(3) a complete voltage regulator with cos-phi- and reactive power regulator;

(4) generator connections;

(5) two generator connection cubicles:

(6) one star point cubicle with necessary current transformers, auxiliary equipment etc.; and

(7) one generator cubicle for connection of the cable connection to the transformer with the necessary CT's, VT's, protective capacitators, the earth switch and other auxiliary equipment.

8.2.3 Cabling:

The Contractor shall provide all relevant cabling for but not limited to:

(1) generator and star point connection as a copper busbar connection between generator, starpoint cubicle and connection cubicle;

(2) external cabling of the generator auxiliaries, voltage controllers, generator protection and measurement, transformers, etc., complete with all auxiliary equipment;

(3) cubicles with generator protection, control and synchronisation equipment; and

(4) all necessary generator measuring instrumentation.

8.2.4 Lubricating and control oil system

The Contractor shall provide a lubricating oil system including but not limited to:

(1) one oil tank including oil strainers, all installations and connections;

(2) one direct driven main oil pump (100%) from the turbine shaft to ensure oil supply when the turbine is rotating;

(3) one oil vapour fan with AC motor drive with oil separation in piping;

(4) one auxiliary oil pump (100%) with AC motor drive;

(5) shaft lifting device 2 x 100% (if necessary);

(6) one emergency oil pump with DC motor drive and power supply unit;

(7) one double cooler (including all heat exchangers and other ancillary equipment) for lubricating oil with switch-over device allowing continuous operation without interruption of oil flow;

(8) one lubricating oil temperature controller (local) including piping between cooler and control valve;

(9) two (each 100%) control oil pumps with AC motor drive when applicable;

(10) one temperature control device for lubrication and control oil;

(11) connection piping, filling safety devices, fastenings, supports of the complete oil liquid system;

(12) sheet metal ducts for oil piping and other protections against oil leakages with leakage detection;

(13) first lubrication oil and first control liquid filling;

(14) facility to sample the oil on-line; and

(15) one oil purification plant complete with all auxiliaries and tank for separation.

8.2.5 Turbine bypass station (if required)

The Contractor shall supply a complete turbine bypass station, designed for the boilers operating at 110% MCR (i.e. to accommodate maximum load variations above 100% MCR) and start-up and shut-down operations, equipped with one emergency stop valve and one reducing valve, pressure reducing de-superheating system comprising water injection facilities, complete with the necessary actuating and control equipment, piping and connections to and from the station to the condenser and from the feedwater line to the water injection point.

8.2.6 Start-up system

The Contractor shall supply a complete pressure control system to allow start-up of the steam turbine, including all drains, valves, start-up headers and controls including protection to prevent damage to turbine or steam pipes caused by inadequate start-up procedures.

8.2.7 Gland steam condenser

The Contractor shall supply a complete gland steam condensing system to collect and condense steam during start-up and in operation, including all piping, tanks, valves, fan and control equipment for the system.

8.2.8 Turbine control system

The turbine/generator control system is to include but not be limited to:

(1) auto/manual governor control change over switch;

(2) manual control of governor speed control;

(3) auto/manual switch for automatic voltage regulator (AVR);

(4) manual control of excitation; and

(5) manual control of AVR set-point.

All turbine controls will be displayed on one screen (per turbine) to show power output, excitation current, frequency, voltage, power factor, steam inlet temperature, steam pressure and vacuum. Direct access to a full page screen showing the turbine generation set with all monitored data is desirable.

Where the turbine generation set has a separate proprietary control system, the system shall either:

(1) be capable of being networked onto the DCS; or

(2) provide a separate I/O subsystem within the turbine control system which will form part of the DCS and will provide all of the necessary control, monitoring and alarm interfaces between the turbine generation set and the DCS.

8.2.9 Turbine hall instrumentation and control (I & C)

The Contractor shall provide the turbine hall I & C system including, but not limited to:

(3) full integration of the turbine control system into the DCS;

(4) software and Documentation, including functional diagrams to IEC 60848 or equivalent and narrative description of all control protection and interlock systems;

(5) all necessary switch and control cubicles for the complete turbine hall, installed in the relevant switch-room, including all associated measuring units and control elements;

(6) all necessary monitoring and control systems to run the complete turbine hall unmanned;

(7) automatic run-up including warm-up, monitoring of turbine expansion end and vibration, and synchronisation equipment;

(8) turbine governing and load control system, including the ability to control the steam pressure of the boiler in all cases;

(9) automatic control/interlocking for the turbine auxiliaries, such as:

a) oil provision;

b) turning device; and

c) turbine protection system including testing equipment;

(10) local controllers including enclosures;

(11) local indicators;

(12) local measuring devices;

(13) all tapping points and connectors for remote measurements as well as for acceptance and test measurements, including primary isolation for instrument lines;



(16) complete installation for all instrumentation and control devices, including but not limited to:

a) wiring to the control system;

b) piping where required including connection to the Plant compressed air system;

c) all required attachments;

(17) all remote measurements, actuators and drives;

(18) all I&C software within the scope of supply;

a) electrical and mechanical isolation where required;

(19) conduits, junction boxes, brackets and other supports, including cable racks; and

a) appropriately segregated routing and support systems for instrument and control cabling.

(20) electrical documentation including loop diagrams and cable schedules;




(24) flow measurements to all water/steam pipes to allow a mass balance to be calculated;


a) vibration;

b) speed;

c) hardwired logic for critical events and sequences including all necessary provisions for events, trips and emergency shut-downs;

d) controls which in the opinion of the Contractor would best be executed as local controls;

e) specification of signals exchanged between these systems and other parts of the Plant, as well as their integration;

f) specification of drives for connection to the emergency power supply and UPS; and

g) definition, at an early stage of the software design, together with the suppliers of the DCS, of the format of the necessary graphics, operator interface facilities, alarms, set-points, sequence logic, trend and display facilities, and agreement with the supplier of the DCS on the definition and optimisation of the storage of status, measurement and trend information for access and collection by the DCS on a local area network.


Each turbine shall be capable of operating continuously over the full range of loads shown on the Firing Diagram, including part loads when one or more of the thermal treatment streams are off-line. The swallowing capacity of the steam turbine shall be such that the Plant operating at MCR shall be able to deliver live steam to the turbine at the guaranteed live steam temperature and pressure, without using the bypass or safety valves. The Contractor shall advise the impact, if any, of this requirement on the net generation efficiency of the Plant at 100% MCR on the boilers.

The performance of the steam turbine generator shall be optimised to deliver its maximum thermal cycle efficiency with the Plant operating at 100% MCR. The steam turbine generator shall be designed so that electrical power can be generated and exported at all loads from 110% MCR steam flow down to boiler minimum turn-down steam flow. The turbine shall be designed with bleed extraction point suitable for supplying steam at the required pressure for the defined plant steam users.

The Contractor shall also provide steam extraction for external use if required by the Purchaser.

At steam flows down to the minimum turn-down on a single boiler, the steam pressure from the turbine extractions shall be sufficient to maintain operation of steam users in the Plant without the need to let down steam directly from the HP steam header and the system shall be designed so that fluctuations in steam flow below and above a set-point corresponding to minimum turn-down shall not cause short-term operation of the HP let-down station. The extraction pressure shall be selected so as to maximise thermal cycle efficiency. The overall thermal cycle of the Plant shall be optimised by the Contractor in terms of capital costs and operating costs.

Alternative steam supplies for each of the Plant extractions shall be provided as required for start-up, shut-down and operation of the Plant stream without the turbine in operation.

Each controlled or uncontrolled extraction shall be provided with at least one pneumatically or hydraulically-assisted and one pneumatically or hydraulically actuated ‘slam-shut’ valve to prevent back-flow of steam into the turbine from an extraction point. The extraction points shall be automatically isolated in the event of a turbine over-speed as part of the turbine protection system. Each extraction line shall include a steam flowmeter of sufficient accuracy for Performance Test measurements.

The turbine design shall prevent the ingress of water and reverse flow of steam from the bled steam, feedwater and condensate systems, in accordance with the minimum requirements as SME TDP-1. In addition to the minimum ASME requirements, the bled steam non-return valve shall be located as close to the turbine as possible and shall be provided with position indication (local and remote) and facilities for on-load test.

The bled steam isolating valves shall be actuated and arranged to fail safe with a fast response time to protect the turbine, which shall be reflected in the valve specification and demonstrated during commissioning.

The steam turbine is to be equipped with a bypass to enable the boiler to operate without the turbine. It should be possible to access and work on the turbine whilst the bypass is in operation. This will require an isolation facility between the turbine exhaust and the air cooled condenser. Depending on the arrangement, it may also require a removable spool piece in the exhaust duct to provide access to the low pressure end of the turbine. The turbine bypass and air-cooled condenser and auxiliary equipment shall be arranged so that the steam from the boiler running at 110% MCR can be bypassed to the air-cooled condenser under the most extreme summer time conditions.

It shall also be possible to operate the turbine without bypass or safety valves opening with the Plant operating at 110% MCR for short periods in case of high thermal loads on the boiler. The swallowing capacity of the turbine shall therefore allow for this eventuality.

The steam turbine shall be designed with a gland steam condensing system. The gland steam condenser shall be installed in the main condensate return line.

The steam turbine shall incorporate comprehensive provisions for drainage of condensate at the low pressure end of the turbine so that it can tolerate a steam moisture content (including the condensate drained into the exhaust duct) without suffering significant degradation.

The electricity generated by the turbine generator shall be used for the auxiliary internal consumers and for delivery to the grid.

The turbine exhaust steam shall be condensed by means of an air-cooled condenser.

The increased mass steam flow and thermal load at turbine bypass operation shall also be considered in the condenser design, so the Plant can be operated with full steam flow bypassing the turbine. The condensate and feedwater systems shall include all necessary items of equipment such as extraction pumps, deaerator, vacuum flash tanks, feedwater pre-heaters, gland steam condenser, feedwater pumps and drain systems.

An evacuation system shall be provided capable of producing an initial vacuum of 500 mbar within 20 minutes, assuming the turbine gland steam system is in operation. The evacuation system shall incorporate a steam ejector for normal operation and a hogging ejector.

The turbines shall operate automatically under the supervision of the DCS.

The Contractor shall include all necessary provision for safe turbine start-up, including any requirements for pre-heating the turbine and steam lines and bypassing the turbine until the live steam conditions required by the turbine have been achieved. If required the Contractor shall install a separate start-up system to enable the steam from the boiler to bypass the turbine to atmosphere until the condenser system is available.

The Plant design shall enable start-up and synchronising from the Plant control room or locally at the turbine.

It shall be possible to isolate the steam turbine so that inspections and repairs can be carried out while the Plant is operating at MCR. This shall include a suitable arrangement for blanking off the turbine exhaust duct whilst providing access to the back of the turbine rotor for inspection purposes.

The turbine auxiliary systems shall also include redundancy of critical components so that the turbine generation set continues to operate in the event of failure of individual components.

8.3.1 General operation

Each turbine shall be designed to operate in island-mode with the turbine supplying only the house load of the Plant to maintain the stream at MCR. In this case, excess steam shall be passed through the turbine bypass. The turbine and bypass system shall be designed so that the Plant will transfer from exporting power to the grid at 100% MCR steam flow to island mode operation without the boiler safety valves lifting or the turbine tripping due to excessive pressure at the turbine exhaust.

The turbine shall be designed to allow operation at all stated conditions. In particular, the turbine design shall be co-ordinated with the condenser design to allow operation without risk of protection trips within the stated ambient air range and with the turbine bypass operating. The design shall allow for the supply of steam at the required pressure to all essential consumers in all load cases, either via the turbine extractions or via pressure reducing stations from the live steam.

It shall be possible to start-up the turbine without excessive blow-off of steam and drains to atmosphere. The turbine bypass shall be used to pass the steam to the main condenser during start-up of the turbine.

A suitable automatic turbine shutdown procedure shall be provided to prevent any possibility of critical over speed on the turbine when the generator breakers are opened. All turbine shut-off valves shall be provided with indicators to indicate their position in the Plant control room, with safety interlocks to prevent connecting the turbine to the steam system if any shut-off valve is in the incorrect position or stuck.

All parts shall be capable of accepting the loads occurring due to rapid load and temperature variation and also due to start-up, shut-down and continuous operation without limitation and without affecting the Design Life.

The live steam header pressure shall be kept constant by regulating the steam turbine governor. The turbine generator shall be capable of operating continuously without any restriction at each load between no-load and over-load.

Long running periods without any restriction shall be considered for the design of the turbine generator. Stub pipes on the casing and larger constructional parts shall have a minimum wall thickness of 5 mm with a minimum nominal bore of 20 mm. If flanges are provided, these shall be designed for a nominal pressure of at least 25 bar-a.

In principle, the turbine control valves shall be hydraulically operated. The necessary stop valves and bypasses shall be installed, so as to be able to repair important control equipment. Possible high ambient temperatures shall be considered within the turbine area when selecting the electrical cables to be used.

The special requirements given below for the individual parts of the system shall also be applied to other parts of the steam turbine system, where applicable.

The turbine generator shall be able to operate continuously with varying steam throughputs, varying extraction and varying condenser pressure. Emphasis is put on maximum possible electricity generation in combination with or without steam extraction.

The planned maintenance periods for the turbine hall shall occur during shut-downs planned for the boiler and combustion chamber. The turbine shall remain in operation for approximately 4 years prior to the first scheduled maintenance shutdown.

The normal mode of operation of the Plant is 100% MCR operation of all streams. The turbine shall be capable of handling steam fluctuations due to the variability of [RDF] without using the steam turbine bypass. The turbines shall be designed to swallow 110% MCR steam production of the boilers without the operation of the turbine bypass. The turbine shall be capable of operating continuously anywhere within the boiler Firing Diagram. The turbine bypass shall be designed to prevent operation of the boiler safety valves following a turbine trip under all operating conditions.

The Contractor shall identify any periods where steam is blown-off during start-up with length of time, noise emission and amount of steam. All vented steam should be vented so that it cannot be drawn into the building HVAC intake.

There shall be an adequately sized controllable steam drain, vent and silencer system for warm-up of the turbine up to the inlet control valve.

8.3.2 Arrangement

The turbine shall be located in the turbine hall and the layout shall be optimised for aiding maintenance and operational requirements.

8.3.3 Steam turbine

8.3.3.1 Casing

To enable the checking of the condition of the turbine blading without opening the casings, borescope openings shall be provided at suitable points on the casing.

In order that rapid assembly and dismantling of the turbine will be possible, the turbine casing shall be split horizontally and supplied with guides to permit safe lifting of the casing.

8.3.3.2 Blading, nozzle segments

Rotor and stator blades, nozzle segments and control parts shall be made of erosion and corrosion proof material. The low pressure rotor blades shall be provided with an additional edge protection, where necessary. The turbine stages operating in the wet steam region shall be provided with sufficient water drains.

Blading shall be designed and constructed to avoid the possibility of damage from vibration when the set is running continuously at any speed between 6% below and 6% above the normal running speed.

The rotor shall be statically and dynamically balanced in the factory at the rated speed. The rotor will consist of either solid forged or welded construction with integrally forged couplings and inserted blades. It shall be possible to rebalance the rotor on Site without particular difficulty (balancing holes in each side of turbine casing shall be provided to allow balancing weights to be applied if required).

Details of the rotor stiffness shall be provided. The rotor shall be tested at over-speed in line with the requirements of IEC 60045.

In the design of the rotor, all notches, sharp inner edges or excessively small radii shall be avoided so that fatigue failures are excluded. All internal radii shall be provided with a high surface finish.

Coupled critical speeds shall lie outside the range 85-125% [TBC] of the nominal speed.

8.3.3.3 Bearings

Generally, the bearings shall be designed as horizontally split plain bearings. The bearings shall be appropriately aligned to minimise vibration. The thrust bearing shall be a tilting pad type, capable of self alignment and taking thrust load from both directions. They shall be axially adjustable.

Earthing brushes shall be provided to protect the bearings. Similarly the necessary bearing and pipe insulation shall be provided to give protection against eddy currents. In order to prevent oil leaks, suitable bearing seals such as oil thrower rings shall be provided. It shall be possible to dismantle the bearing seals without removing the turbine casing or dismantling the generator.

8.3.3.4 Gland seals

Steam shall not be discharged into the turbine hall. It shall be possible to check the clearances in the outer labyrinth through a removable cover without removing the turbine casing.

8.3.3.5 Emergency stop valves, governor valves, reducing valves,

non-return valves

Spindles, fittings and control parts shall be manufactured from stainless steel. The guide surfaces shall be manufactured from hard-wearing materials or they shall be armoured and be compatible with guided components. Spindle leakage losses shall be avoided by using suitable seals.

In order to facilitate the safe and reliable shutdown of the turbine system, the emergency stop valves and governor valves shall be arranged with easy access as near as possible to the appropriate turbine casings.

The means of on-load testing of normally open control valves shall be provided.

Non-return valves fitted to turbine bleed extractions shall:

(1) promote rapid positive closure without slamming to provide a robust and reliable leakage-free seal;

(2) be proven in similar applications where operation occurs rarely, especially in regards to corrosion resistance throughout the design life of the valve;

(3) have a mechanism to allow closure from reverse flow, even though the actuator has failed;

(4) be designed to minimise the pressure drop at low flow rates; and

(5) include a facility to check operation of the valve while the turbine is in operation.

8.3.3.6 Steam strainer

A strainer shall be supplied in the live steam line to the turbine with facilities to easily allow changing and cleaning of the strainer during turbine shutdowns.

8.3.3.7 Turning device

Hydraulic or electrically driven turning devices shall be employed. The turning device shall disengage automatically as soon as the turbine speed exceeds the turning speed. The turning gear shall be automatically engaged during shutting down of the turbine.

A higher turning speed will be preferred because of the better temperature balance between the upper and lower casing parts due to the fan effect. If jacking oil pumps are necessary, two jacking oil pumps per unit shall be supplied (one pump in operation and the other one as standby) and interlocked so that turning without oil supply is prevented, in order to avoid mixed frictional effects in the bearings during starting of the turning device. Interconnection between the lubricating oil supply and turning operation shall be ensured by automatic interlocks. In addition, a manually operated emergency turning device shall be provided. Turning gear pumps and jacking oil pumps (if required), shall be connected to the UPS as well as the emergency power supply.

8.3.3.8 Couplings

All couplings shall be designed to withstand the maximum torque that is envisaged to occur during a short circuit fault of the generator. As a minimum this torque shall be modelled as 8 times the nominal torque on the drive coupling.

8.3.3.9 Gearing

If a reducing gearbox is being offered, it shall be rated for a nominal torque that is 110% of the torque that will be transmitted for the maximum continuous output of the turbine.

The gearbox shall be designed to withstand the maximum torque that is envisaged to occur during a short circuit fault of the generator. As a minimum this torque shall be estimated as 8 times the nominal torque applied through the gearbox.

Gears shall be of the double-helical teeth design.

8.3.3.10 Gland sealing steam system

Turbine gland-sealing steam shall be obtained from the live steam header. An automatically controlled sealing steam system shall be provided. The injection cooler necessary for reducing the sealing steam temperature shall be supplied with water from the main condensate system.

The gland steam system shall be provided with a gland steam and vapour condenser (as applicable) and vapour suction fans. The condenser shall be arranged in the main condensate line.

8.3.3.11 Thermal insulation

In order to avoid a possible penetration of oil, insulation with an oil-tight hard cover shall be provided for the turbine. Heat radiation which might cause damage to the foundations shall be avoided. Asbestos insulating material shall not be accepted. Housing flanges shall be provided with reusable insulating sections.

Hot sections which cannot be insulated, such as observation openings, shall be provided with a corresponding contact protection.

8.3.3.12 Turbine cladding

Should turbine cladding be used it shall be designed as a hood and provided with sufficient corrosion protection.

Heat build-up within the turbine cladding shall be avoided by suitable ventilation. Particular importance shall be attached to quality of appearance of the turbine generator set with the turbine cladding installed. Furthermore, the cladding shall be easily dismantled/re-installed.

The turbine cladding shall be provided with access doors for inspection and maintenance.

8.3.3.13 Acoustic enclosure

Should the Contractor determine that an acoustic enclosure is required around the turbine / generator in order to meet the noise guarantees, then such an enclosure shall include suitable access doors for inspection and maintenance. Illumination shall be provided within the enclosure. Consideration shall also be given to access requirements during turbine outages, ensuring straightforward dismantling of the enclosure.

8.3.3.14 Isolation of turbine

It shall be possible to isolate the turbine completely from the steam/water system to allow maintenance whilst the Plant stream is in operation. In all the extraction lines, motorised stop valves shall be provided for isolation purposes. It shall also be possible to isolate the turbine from the condenser. If this isolation is via a blanking plate to be installed with the boiler shutdown, a removable section of the turbine exhaust duct shall be provided for ease of installation. It must be possible to carry out the installation and removal of this plate in a short time (not more than 12 hours).

8.3.4 Instrumentation and control

8.3.4.1 General requirements

Normal operation and shut-down of the turbine generator shall be remotely controlled and continuously supervised from the Plant control room by means of the remote control and monitoring devices. Local start-up of the turbine from the local turbine control panel shall be possible. This control panel shall contain the minimum amount of indicators, alarms, and control switches necessary for local start-up. Preparatory work for start-up may be done locally.

Wherever required in this Contract, all control equipment to be supplied shall be suitable for remote control from the Plant control room. Displays for local instruments shall be grouped according to process systems, e.g. all instruments for control oil pressure and temperature at a common place.

The control, regulation, protection and monitoring of the turbine generator shall be complete and safe in every respect. In the event of loss of the grid this shall not lead to a turbine trip. The turbine shall continue running in isolated operation, i.e. providing power to the station auxiliaries.

8.3.4.2 Remote measurement and monitoring systems

With respect to the remote measuring and monitoring devices, the supply shall comprise but shall not be limited to those laid down in the tables of instrumentation.

8.3.4.3 Instrumentation

For the complete scope of supply, instrumentation has to be provided which gives the possibility to monitor, control and operate the turbine generator from the local panel as well from the Plant control room. The instrumentation shall make it possible to allow closed mass, energy balances and the net calorific value to be calculated, with the facility to calibrate against the weighbridge quantity measurement.

The pumps shall be designed with local pressure gauges on the suction and pressure side. The pressures behind the most important pumps shall be transferred to the local panel and the Plant control room. The inlet and outlet temperatures of the heat exchangers must be indicated locally. The use of pressure gauges in direct contact with the fluid is not allowed.

8.3.4.4 Turbine control system

The Contractor shall supply the range of equipment which would make possible the safe fulfilment of the tasks as outlined and the maintenance of the necessary regulation accuracy. In addition, the governing system shall guarantee stable operation of the turbine generator at all load points.

The turbine governing system shall carry out the following tasks as a minimum:

(1) speed-frequency control;

(2) live steam pressure regulation using the turbine governor (primary) and turbine bypass valves (secondary and for start-up and shutdown);

(3) extraction pressure regulation; and

(4) constant export load control.

An electronic turbine governor system capable of providing safe operation of the turbine shall be employed. The frequency-power characteristic, including the governor valves, shall have a response sensibility of less than 0.1% of the rated frequency. In addition, the governor equipment shall meet the following requirements.

A transient speed increase, on the sudden shedding of load from maximum continuous power to no load running, shall not exceed a level to prevent the possibility of turbine over-speed trips, based on supplier’s recommended over-speed.

It shall allow the turbine generator to respond to sudden load changes.

It shall be possible to set the proportional band speed droop within the limits 1.0-8.0% in steps of 0.5%.

The governing system shall operate over the complete speed range from 100 rpm to maximum speed without hunting.

The governing system shall allow stable island mode operation, even if this occurs suddenly, over the complete load range of the turbine generator (island mode shall mean not running in parallel with other power-producing machines). The governing system shall allow bumpless change-over of one operating mode to another. This shall include transfer to island mode on loss of the grid connection when the turbine generator is operating at its rated power.

The live steam pressure control system shall be capable of maintaining the nominal pressure within a range of 6%. At constant load, the pressure deviations shall not exceed ±1.25%.

8.3.4.5 Turbine protection system

The protection system (exclusively of an electronic type) shall protect the turbine Plant in every phase of operation from overload and damage. It shall be hardwired and completely separated from the digital control system. It shall be continuously ready for operation and capable of being checked and calibrated during operation without tripping the turbine generator set and shall not be possible to switch off even accidentally. The necessary protection interlocks shall be connected directly to the trip device.

The protection interlock chain "Turbine Protection" shall be designed to achieve a high level of safety, and combined into the control system as an interlock criteria so that the turbine is protected from overload and damage through the complete operating range. The following protection criteria shall include but not be limited to:

(1) turbine speed greater than maximum (at least two independent electronic overspeed systems and each shall be completely independent of the other, with facility to test the overspeed protection while on load and this testing of an overspeed protection device shall be arranged so that the machine is not left, at any time, without an operative overspeed protection device);

(2) bearing metal temperatures (thrust and journal) greater than maximum;

(3) bearing vibration greater than maximum;

(4) shaft vibration greater than maximum;

(5) lubricating oil pressure lower than minimum;

(6) lubrication oil tank level lower than minimum;

(7) level of pre-heaters greater than maximum;

(8) condenser pressure greater than maximum (insufficient vacuum);

(9) water level in the exhaust line higher than maximum;

(10) generator protection operated;

(11) unit trip operated (trip button in Plant control room);

(12) local turbine trip operated;

(13) turbine and generator bearing vibration monitoring;

(14) gearbox bearing vibration monitoring; and

(15) excessive rotor end movement.

As far as possible the operating personnel shall be made aware of danger by alarms prior to the protective system coming into operation.

All electrical and electro-hydraulic protective circuits (e.g. bearing temperature, shaft position, lubrication oil pressure) on the turbine shall be so constructed (using 2-channel self-monitoring or 2 from 3 selection) that faults in one protective interlock will cause no erroneous activation of the others, but at the same time shall not prevent the initiation of a trip in an actual case of danger. The protective circuits shall be supervised to a large extent by checking equipment and it shall be possible at any time to inspect the functional correctness of the protection without causing a trip of the turbine. The protective signals shall operate on all turbine emergency stop valves, on the bleed and extraction steam emergency shut-off valves and check valves. It shall be possible to check the functional correctness of these emergency stop/shut-off valves and the extraction steam control and check valves during continuous operation.

8.3.5 Reducing stations

The Contractor shall supply reducing stations as required to satisfy all the operations specified. These shall supply steam at the relevant pressure and shall incorporate attemperators to reduce the steam temperature as required by the limits of maximum temperatures allowed after the reducing stations and the heat transfer design requirements of the heat exchangers in the system.

Each reducing station shall be supplied with the relevant control including spray water control.

The turbine bypass reducing station has to operate sufficiently quickly to prevent the boiler safety valves opening in case of a turbine trip and to prevent the turbine tripping on high exhaust pressure in the transfer of the Plant from exporting power to island mode operation. The duct after the bypass shall be dimensioned for steam temperatures in case of short-term failure of the attemperating spray.

Noise emissions on reducing stations shall be considered to achieve the required levels.

8.3.6 Generator workshop tests

The following generator workshop tests shall be performed and witnessed by the Project Manager or his representative. The tests shall include but not be limited to:

(1) measurements of the insulation resistance;

(2) loss factor measurements;

(3) measurements of winding resistances, cold;

(4) dielectric tests;

(5) open-circuit characteristic test and determination of no-load losses;

(6) short-circuit characteristic test and determination of short-circuit losses;

heat test run to determine the temperature rise of windings (alternatively separate heat test runs are permitted IEEE 115) with graphic superposition of their results as follows:

(7) at 1.1 x stator rated voltage and no-load (*);

(8) at 1.05 x stator rated current and terminal point short circuit (*);

(9) at zero excitation and no-load (*);

(10) overspeed test at 1.2 x rated r.p.m;

(11) measurement of vibration; and

(12) preparation of a summarising report of the above-mentioned tests with evaluation of the results and comparison with the permitted values according to the standard or this Contract.

In addition the following tests may be added if the Contractor considers them advisable:

(13) sudden short-circuit tests at approx. 0.2; 0.4 and 0.7 Un rated voltage with determination of transient and subtransient reactances and time-constant extrapolated to 1.0 x rated voltage (IEC 60034-4);

(14) determination of voltage wave form and THF-factor; and

(15) noise measurement according to IEC 60034-9 and ISO 1680 (*).

The factory tests are to be completed according to IEC 60034.

The tests marked by (*) can also be substantiated by means of a test report (to be certified by an independent institute) for a generator of the identical type. Reduced prices for the tests not completed according to the above are to be stated in the tender.

9 Air-cooled condenser


All items under the scope of supply should conform in every way to the relevant and latest British and European standards, codes of practice, regulations and laws applicable to air-cooled condensers, including but not limited to:

VGB-R 131-Me: VGB guideline acceptance test measurements and operation monitoring of air cooled condensers under vacuum;

VGB-R 126 L e: Recommendations for the design and operation of vacuum pumps for steam turbine condensers; and

VDI 2049: Thermal acceptance and performance tests on dry cooling towers.

9.2 Scope of supply

The Contractor shall design, deliver, install, integrate and commission, test and certify the following scope of supply for two complete air-cooled condenser (ACC) systems, one for each turbine, comprising:

(1) ACC complete with finned tube bundles, cooling fans and steam distribution ducts;

(2) exhaust duct from the turbine outlet to the ACC, including transition piece, elbows, expansion joints, nozzle for bypass and duct support;

(3) steel structure including platform with supporting columns, fan bridge supporting structure, rings, protective grids, inlet nozzles, surrounding wind wall, dividing walls, 1 stairway and 1 emergency ladder;

(4) fan system, including motors, gearboxes, couplings, lubrication system;

(5) air extraction system including 1x100% hogging steam ejector and 2x100% holding steam ejector sets or one air extraction liquid ring pump complete, including condenser, control equipment, relief lines, noise damper, piping, valves, fastenings etc.;

(6) condensate system including supporting structure, tanks, drain pots, pumps, condensate header, insulation, anchoring, stiffeners, baffle plates, condensate level control, condensate return filters, overflow system to collect the condensate;

(7) all required interconnecting piping, rupture discs (including spares), valve and fittings within the condenser plot area;

(8) one off blanking plate to isolate the turbine exhaust from the ACC;

(9) semi-automatic jet-wash cleaning system, with the ability to remove pollen and other deposits;

(10) integrated control system linked to the DCS;

(11) equipment to ensure freeze-free operation at low load in wintertime;

(12) electrical systems with all necessary electric drives and consumers including but not limited to:

a) switch and control boxes as far as possible in the relevant switchrooms included cabling between the cubicles and the consumers, sensors, end switches etc. with cable trays, protecting pipes etc.

b) complete electrical installation of all material such as wiring, cabling material, all necessary connections, conduits, brackets and other supports including cable trays;

(13) instrumentation and controls including but not limited to:

a) all instrumentation shall be provided as required for a safe and reliable operation and supervision of the air cooled condenser including complete wiring, cabling, and piping material, all required mountings, attachments, protecting pipes, brackets and other supporting material including cable racks; and

b) the ability for the air-cooled condenser to be operated from the Plant control room via the DCS.

9.3 Operating conditions

Each ACC shall be designed to operate at all load combinations within the Firing Diagram, over the range of ambient air conditions without any risk of causing the steam turbine to trip. The air-cooled condenser shall be capable of operating continuously without any restriction at each load condition required.

In turbine bypass operation, the ACC may be charged with the MCR steam flow including the injection water for desuperheating. In this situation the turbine exhaust pressure is allowed to rise according to the higher heat load.

All parts shall be capable of accepting the loads occurring due to rapid load and temperature variation and also due to start-up, shut-down, emergency shut-down, sudden isolation from the public grid and continuous operation without limitation and without affecting the Design Life time.

The turbine exhaust steam is condensed by direct dry cooling by means of an ACC. The air-cooled condenser is installed in open air adjacent to the Plant. The windwall to the air-cooled condenser shall comply with the Planning Drawings. All necessary measures to avoid recirculation of cooling air around the ACC, which may be introduced by wind, surrounding buildings, structures, etc., shall be provided.

The condenser design shall be co-ordinated with the turbine to ensure an optimal design both in terms of operating cost and capital cost. The thermal cycle shall be optimised at the given design conditions. The design shall evaluate the possibility of having suitable capacity to operate the Plant at MCR with one cell isolated for maintenance. In addition, each air-cooled condenser shall be designed to:

(1) allow operation of the relevant Plant stream at MCR with the turbine fully bypassed; and

(2) allow operation of the Plant stream at MCR at high ambient temperatures without risking turbine trips due to high steam exhaust pressures.

In the above two cases, whilst it is essential that the boiler can operate continuously without tripping or steam safety valves opening, the thermal efficiency of the cycle is not critical.

The condenser design shall also be optimised by the selection of sufficient two-speed or variable speed fans to reduce the auxiliary power requirement whilst maintaining cooling, and taking into account the noise requirements for the Plant.

All necessary measures to avoid recirculation of cooling air, which may be introduced by wind, surrounding buildings, structures, etc. shall be provided.


9.4.1 Air-cooled condenser

The ACC shall be designed as a A-frame type with finned tubes. The condenser shall be of combined parallel and counter flow or pure counter flow type. Sub-cooling and freezing of the condensate shall be avoided under all circumstances.

To ensure safe winter operation, the start-up of the installation has to be possible at the lowest temperatures. The installation shall also be able to operate at 20% turbine MCR part load and lowest temperature continuously. The condenser material has to be suitable for all possible climatic conditions. The danger of icing and freezing shall avoided by a counter flow condenser configuration.

The bond between tube and fin shall be over the whole tube surface to achieve a high heat transfer performance and shall not be impaired by thermal loads, corrosion or mechanical stress. The tube and fin material shall be of hot dip galvanised steel or aluminium coated steel tubes with aluminium fins. The design should be consistent with the Design Life of the Plant. Unacceptable vibrations of the condenser tubes shall be avoided. The condenser elements shall be designed in such a way that no unallowable forces can be exerted due to thermal expansion, over-pressure, etc. The arrangement of the finned tube rows must be such that easy access for thorough cleaning is possible. All structural steel work such as frame work, platforms, stairways, piping supports, etc. shall be protected against corrosion by painting.

The upper part shall be enclosed with wall panels. If noise damping elements are provided they shall be mounted in the steel structure of the condenser and shall be designed for easy drainage of accumulated moisture from the sound absorbing elements.

Bird protection shall be provided at the cooling air inlet and outlet, such as protective grids at the inlet and bird nets at the condenser outlet, in such a manner, that birds and other flying objects cannot interrupt operation.

Recirculation of the cooling air has to be avoided under all circumstances. An air flow study shall be submitted to the Project Manager for review (see also Schedule 2).

All tubes, headers and distribution manifolds under vacuum shall have welded joints for vacuum tightness. The inlet steam shall be distributed in such a manner as to secure optimal and even admission of steam over the entire number of finned tube bundles. The finned tube bundles shall be contained in a casing consisting of side walls, support bars, spacers, etc. forming a self-supporting unit allowing thermal expansion. All tube weld seams shall be tested for leak-tightness.

All manifolds and tube bends shall be protected by baffles or other means to prevent erosion by wet steam or solid particles contained in the steam.

Safety valves will be designed to minimise rupture disk activation.

9.4.2 Cooling air fans

The fans shall be of low pressure axial flow design with aerodynamically designed blade profiles and with provisions for easy adjustment of the fan blade angle (during stops). They shall not exert any undue vibrations on the surrounding structure and the condenser itself.

If necessary, noise absorbing elements in the intake area shall be used to ensure operating noise levels are below the allowable noise level.

The drive speed shall be reduced via a reducing gear. V-belt reducers shall not be accepted. AC electric motors shall be two-speed or fitted with frequency converters for variable speed. Gears and bearings shall be oil bath lubricated. Gears and bearings shall be designed for 120% of the maximum shaft load and the gears shall be of vertical design.

The motors shall be fitted with vibration monitoring allowing feedback of the levels of vibration within the system.

The fans shall be designed for a minimum of three starts per hour.

The fan gearboxes shall be designed to last the Design Life of the Plant, as stated in Specification Part A. Oil level shall be easily monitored. The gearbox service factor shall be AGMA 2 minimum.

9.4.3 Evacuation system

A system (e.g. steam air ejectors or liquid ring pump) shall be provided for evacuating the steam space during start-up and for normal operation. The units shall be of such capacity that the condenser vacuum will still be maintained even with small leaks. The evacuation system must be sufficient to raise an initial vacuum of 500 mbar within 20 minutes.

If steam ejectors are preferred, live steam shall be used in the ejectors. A hogging ejector and two holding ejectors shall be supplied. The ejectors shall be of the two-stage type and be redundant. The nozzles shall be manufactured from stainless steel and shall be detachable. Steam admission to the steam ejectors shall be remotely actuated from the Plant control room. Steam from the ejectors shall be returned to the condensate system via condensers.

The hogging ejector shall incorporate a silencer.

If an alternative system is provided, the Contractor must ensure that sufficient capacity is installed to raise the initial vacuum. The system shall be remotely activated from the Plant control room.

The vacuum system shall be designed to draw a satisfactory vacuum and remove non-condensable gases from the condenser under the highest summer-time temperatures.

9.4.4 High pressure washing system

A semi-automatic high pressure washing system shall be provided to remove tube fouling whilst each air-cooled condenser is in operation.

9.4.5 Condensate system

The Contractor shall supply and install a complete condensate return system to recover and return steam / condensate from the steam uses within each boiler line, steam traps, and the condenser.

9.4.5.1 Condensate tank

The condensate tank shall be located near to the ACC.

The condensate tank shall be able to receive the condensate from the condenser as well as from all drains during start up or operation. The tank shall be sized for at least 10 minutes of MCR flow from the boiler.

Flash tank(s) shall be installed where appropriate on condensate return lines in order to minimise flashing in the condensate tank

Valves shall be provided for isolating the tank from its connected pipe systems.

The stub pipes for the condensate pump suction lines shall protrude approximately 100 mm into the tank and shall be fitted with flow breakers. Stub pipes shall be welded where possible. Stiffeners with inspection holes shall be welded in place where necessary.

There shall be at least one spare stub pipe on each of the steam and water sides of the condensate tank. All valves and fittings directly above the condensate tank shall be accessible from platforms.

Connections to the condensate tank shall include but not be limited to:

(1) balancing pipes between turbine exhaust line and condensate tank;

(2) pipes from the exhaust drain tank;

(3) vacuum flash tank condensate line;

(4) separate drains flash vessel draining by gravity into the condensate tank;

(5) minimum flow lines of main condensate pumps;

(6) main condensate pumps' suction lines;

(7) emptying lines; and

(8) filling lines.

9.4.5.2 Main condensate pumps

The main condensate pumps shall be centrifugal pumps with 2 x 110% capacity. The 100% rate of delivery of the main condensate pump system shall be at least according to the following maximum cases, which are:

(1) exhaust steam flow of the turbine with no steam export; and

(2) turbine by pass steam flow with injection water flow.

All parts of the pumps coming in contact with the water shall be manufactured in stainless steel. Casing and rotors shall be provided with wear rings in order to permit easy replacement of the parts subject to wear. The pumps shall be provided with suitable bearings and mechanical seals for operation of the pumps alternatively on standby or service conditions. The seals shall be provided with sealing connections using condensate from the discharge pipe as sealing water. The pump motors shall be designed for at least 25% overload. Pumps and driving motors shall be supplied on common base plates.

The pumps shall be low speed and with low net positive suction head (NPSH). They shall be designed to take into account the lowest system pressure.

Each pump shall be provided with a fine mesh strainer on the suction side, made of stainless steel, for preliminary operation and commissioning.

The pump suction and discharge piping connections shall be flanged.

9.4.5.3 Turbine exhaust duct

The maximum steam velocity in the exhaust duct shall not exceed the velocity defined in Specification Part C and the pressure drop in the exhaust duct shall not exceed 5% of the exhaust steam absolute pressure.

Condensate shall be collected from the lowest point in the turbine exhaust duct into a tank by gravity. The condensate collected will be pumped via duty/standby pumps to the condensate tank. The tank shall incorporate level measurement.

The design shall take into account the requirement to insert a blind flange into the exhaust duct, using the turbine crane, to isolate each turbine from the respective condenser in case of extended periods of operation without the turbine. It must be possible to carry out the installation and removal of this plate in a short time (not more than 12 hours).

10 Steam and water circuit


All items under the scope of supply should conform in every way to the relevant and latest British and European standards, codes of practice, regulations and laws applicable to steam and water systems, including but not limited to:

BS EN 13480: Metallic industrial piping;

BS EN ISO 9906: Rotodynamic pumps;

BS EN 13445: Unfired pressure vessels;

ASME Boiler and pressure vessel code section 8 pressure vessels; and

VGB-006-00-2012-09-EN: Sampling and Physico-Chemical Monitoring of Water Steam Cycles .

10.2 Scope of supply

The Contractor shall design, deliver, install, integrate and commission, test and certify the following scope of supply for the complete steam and water circuit for each individual boiler, including but not limited to:

(1) complete duty and standby boiler feedwater pumps per stream, each pump sized to serve each boiler stream at MCR - the pumping design shall be based on 2 x 100% pumps;

(2) all pump couplings, coupling guards, cooling systems, common base plates for pump and drive, anchorages, etc.;

(3) feedwater tank with deaerator, complete with supporting structure, anchoring, all stub pipes, stiffeners, baffle plates, steam-heated stand-pipe, strainers, vapour extraction system, safety valves etc.;

(4) LP feedwater pre-heating system, including any drain pumps and accessories required;

(5) flash and drain tanks complete with supporting structure, anchoring, stub pipes, stiffeners, baffles, level control, pumps, accessories etc. as required by the specific turbine hall layout;

(6) all necessarily complete minimum-flow systems with minimum-flow valve, flow-measuring device, start-up line, cascade throttling unit, piping, valves, etc.;

(7) all connecting piping, safety devices, control equipment, fastenings, expansion joints, flanges, gaskets, bolts etc. including but not limited to connections between;

a) the live steam header and the steam turbine inlet;

b) the waste heat boiler’s live steam pipe rack and piping from glass production;

c) all piping, connections and instrumentation/equipment in the feedwater line from the turbine terminal point, including connections to the condensate tank feedwater pre-heaters, deaerator and feedwater pumps to the boiler;

d) the boiler make-up/condensate return from the boiler;

e) the extraction points from the turbine and the feedwater pre-heaters;

f) the extraction points from the turbine and the deaerator;

g) the condensate tank and the gland steam condenser of both steam turbines;

h) the evacuation system;

i) the steam turbine bypass valve via the dump to the main condensate system;

j) reducing valves and desuperheaters including all necessary safety devices, control equipment, fastenings, expansion joints, etc. where required for all required let-downs of live steam, e.g. to turbine bypass, air pre-heaters etc.;

k) instrumentation to measure pressure and flow and any other necessary characteristics; and

l) water steam quality monitoring and sampling system as detailed in section 10.3.6.

10.3 Description and General Requirements

10.3.1 Feedwater Pumps

The pumps supply a constant pressure to the feedwater control valves.

Feedwater pumps shall be sized to deliver full feedwater flow sufficient to allow the drum level to be adequately restored whilst at full load taking into account allowance for thermal overload, spray/desuperheating flows, bypassing the turbine and attemperation water.

The pumps shall have generously dimensioned journal bearings and oil lubrication. There shall be appropriate design features for balancing the axial thrust, preferably by a thrust bearing. The bearing shall be dimensioned so that even in the event of short duration cavitation, no damage to the pump or bearings will occur.

The bearings shall be designed to accommodate displacement of the pump impeller due to thermal expansion.

Adequate provision shall be made at the end of each bearing for catching grease or oil and to prevent water from contacting the bearings.

All rotating parts shall be statically and dynamically balanced, independently and as an assembly.

All replacement parts shall also be individually balanced. The pump units shall be capable of being laser aligned and fitted with appropriate alignment aids, e.g. jacking bolts.

The minimum flow valves shall be automatically actuated. The minimum flow lines and relief lines for each pump shall be run separately to the minimum flow manifold. The minimum flow manifold shall be located at the level of the pump.

Strainers shall be included in the suction lines to protect the pumps from damage under all operating conditions and during commissioning. The strainer mesh size shall be appropriately sized by the Contractor. The strainer and strainer body shall be matched so that the full area of the strainer is utilised. The free area of the strainer shall be at least equivalent to five times the cross sectional area of the corresponding suction pipe. It shall be possible to easily remove and re-install the strainer without excessively disturbing the connected piping. Lifting aids shall be provided where required.

Feedwater pumps shall be connected to the emergency power supply to ensure that feedwater flows are maintained even when main power is lost so that the boiler and combustion chamber can be shut down safely and without damage unless it can be demonstrated to the satisfaction of the Project Manager that this is not required. As a minimum the emergency power supply should ensure that the total feedwater flow capacity at minimum turn-down is available whilst the Plant is being powered by the emergency standby generator.

Automatic switching of the feedwater pumps shall be installed in the DCS to enable changing the operational feed pump either on a pump trip or by operator selection. This switching shall be sufficiently fast to prevent feedwater supply pressure dipping.

In order to simplify the Plant arrangement, booster pumps shall not be used. The suction requirements of the pumps under all possible operating conditions shall be met by suitable dimensioning of the suction pipe system and the level of the feedwater tank in order to ensure cavitation damage does not occur.

The pumps shall be mounted on suitable foundations capable of suppressing vibration to an acceptable level.

Suitable provision for the support of thermal insulation shall be made on the outer casing of the pump.

The design of the boiler feed water pumps should include mechanical seals and not be dependent on a water cooling system.

10.3.2 Feedwater tank

For each boiler, the feedwater tank and deaerator shall be capable of serving the boilers under all normal and abnormal operating conditions. The design shall be configured to allow maintenance and statutory inspections to take place without the need to shut down the entire Plant. The supply shall come complete with supporting structure, anchoring, all stub pipes, stiffeners, baffle plates, steam-heated stand-pipe, strainers, vapour extraction system, safety valves etc.

The feedwater tank shall be suitably sized to be large enough to balance the total feedwater held in the system during load changes/stops and to ensure that all systems remain stable.

The Contractor shall ensure that the design of the steam and water systems comprising the Plant thermal cycle shall have sufficient buffering capacity and control dead zones to accommodate normal and abnormal operations without high or low level alarms occurring on any water container including the boiler steam drum, the deaerator and all condensate collection systems.

10.3.3 Feedwater tank and deaerator

The deaerator for each stream shall preferably be either of the cascade or spray type with re-evaporation. The feedwater tank shall have a warming up steam line for either design.

The deaerator shall have capacity of 110% maximum feedwater flow to the boiler and shall be capable of meeting Plant demand under all operating conditions.

The deaeration steam shall be taken from the turbine bleed to maintain a constant deaeration pressure. The turbine shall be equipped with bleeds at various points on the casing so that, under part load conditions, deaerator and air preheat requirements can be serviced by turbine extraction steam.

When the turbine is out of operation, the deaeration line shall be supplied with steam from the live steam main header through the auxiliary reducing stations. Therefore, deaeration steam at the right pressure shall always be made available in order to maintain the required minimum feed temperature to approximately 140°C.

The supply of water to be heated comes from the main condensate tank. In addition, the feedwater pump minimum flow, balancing and relief flow (where applicable) lines shall also be returned to the feedwater tank.

For the design, it shall be assumed that a maximum make up water flow saturated with O2 and CO2 will be supplied to each deaerator.

The feedwater tank shall be sized to allow at least 20 minutes of MCR feedwater flow to the boiler between the normal level and the low level. The tank shall be fitted with level control monitoring system with high and low level alarms, providing local and Plant control room level status.

A distance of at least 400 mm shall be allowed between the normal regulated water level of the feedwater tank and the maximum permissible level. Safety valves shall be provided which are able to safely discharge the maximum possible supply of water. To allow for possible movement of the contents of the feed tank, a horizontal impact force of 10% of the maximum vertical load shall be assumed.

In order to avoid the danger of corrosion, diverter plates shall be fitted in the dead corners of the feed tanks to improve circulation. The wall thicknesses for the feed tank and deaerators shall have a corrosion allowance of at least 3 mm. The tanks shall be suitably stiffened to safely withstand full vacuum.

The stub pipes for the feedwater suction lines shall protrude approximately 100 mm into the tanks and shall be fitted with flow breakers. Stub pipes shall be welded where possible. Stiffeners with inspection holes shall be welded in place where necessary.

The feed tank and deaerator shall incorporate suitable manholes.

There shall be at least one spare stub pipe on the steam as well as the water side of the feed tank. All valves and fittings directly above the feedwater tank shall be accessible from platforms.

10.3.3.1 Deaerator control

The Contractor shall control the functions of the deaerator to match the supplied system. Consideration shall be given to the steam supply to the deaerator, taking into account the use of extracted steam in normal operation but reduced live steam will be used during bypass operation.

10.3.4 LP feedwater heaters and condensers for auxiliary systems

Adequate provision shall be made to protect the turbines against the backflow of water from the LP feedwater heaters.

The emergency drain of each LP feedwater heater and the steam side safety valves shall be suitable for discharging 50% of the heater's maximum main condensate flow.

The LP feedwater heaters shall be based on a well-proven design approach.

All pipe connections and all connections on the vacuum side shall be welded.

Valves and other fittings exceeding a nominal size of 25 mm, which are continuously or intermittently under vacuum, shall be provided with sealing water connections.

Shell and tube bundles shall be equipped with effective baffle plates and protected at the steam and drains inlets. Particular care shall be taken to ensure proper air extraction, so that no air pockets can form inside the heat exchangers.

Special provisions shall be made for the withdrawal of feedwater heater tube bundles. The heat exchanger tubes shall be seamless with an inside diameter of at least 15 mm each.

An adequate number of inspection holes shall be provided at particularly susceptible areas, such as the steam inlet, above the water level regulator, etc. to allow visual inspection of the internal condition of the heat exchangers.

The stub pipes shall be welded, wherever possible, both internally and externally. Stiffeners with inspection holes for stub pipes shall be welded in place where necessary.

Tubes shall be seal welded into the tube sheet.

Vacuum and drain flash tanks for all drains and blowdown, including necessary pumps and fittings shall be supplied to suit the Contractor’s preferred layout. The condensate from any flash tanks within the boiler house for the vents, drains and air pre-heaters will be fed back into the condensate system.

For the design, the following criteria shall be considered.

(1) Only condensate at approximately the same temperature and pressure shall be combined to a common header or vessel.

(2) The collecting pipes entering the flash tank shall be dimensioned so that the flashing steam at the inlet of the flash tank does not exceed a velocity of 50 m/s (if necessary, throttle orifices shall be provided in the inlet headers).

(3) The condensate shall be fed into the tank above the highest water level.

(4) The outlet of the flash tank shall be connected to another tank (if necessary) and pumped into the main condensate tank. Level control of the tank and minimum flow of the pumps shall be provided.

(5) The flash tank shall be provided with suitably sized manholes and in accordance with the confined spaces ACOP.

(6) Flash steam energy shall be recovered to the thermal cycle as far as possible.

10.3.5 Design requirements

The Contractor shall be responsible for ensuring that the testing of the piping system is certified by a notified body agreed with the Purchaser.

The Contractor shall pay particular attention in the design to the adequacy of buffer volumes in the steam drum, the deaerator and the condensate collection tanks:

(1) to handle all normal and abnormal operating conditions including cold and hot starts, normal and emergency shut-downs; and

(2) with a control system which correctly allocates reserve capacity allowing it to be used when required without the need for dumping water or calling for make-up water to deal with operational fluctuations.

Special emphasis shall be placed on the design of the piping system to ensure high resistance to corrosion. The materials shall satisfy without restriction the requirements of erosion and corrosion resistance resulting from operation with demineralised water and water conditioned with volatile alkalising agents having a pH value equal to or greater than 7.0. Protective sleeves on the shafts shall be hard chromium plated. Cooling sections and bearing mountings shall be made of cast steel.

Only condensate at approximately the same temperature and pressure shall be combined to a common header or vessel.

Where appropriate the Contractor shall install double block and bleed systems to allow safe discharge and isolation of valve systems, in accordance with Schedule 20C and/or where agreed with the Project Manager.

The Contractor shall ensure the feedwater drive is appropriately energy efficient, and use inverter driven feedwater pumps to maintain constant feedwater supply pressure at the inlet to the feedwater control valves, as appropriate.

The Contractor shall set out his proposals for pipe bending (i.e. use of elbows, cold formed or induction bends). The use of cold formed bends is not precluded. However, their use will be subject to the Project Manager’s approval. The Contractor shall set out a quality control plan for the Project Manager’s to review, showing how the Contractor proposes to control the manufacturing and heat treatment processes for any such bends and accurately document their numbers, details and location.

10.3.6 Steam and water quality monitoring and sampling

The Contractor shall provide a system for sampling and measuring the quality of fluid in the steam and water circuit, including but not limited to:

(1) suitable instrumentation for on-line and laboratory analysis of conductivity, ph, dissolved oxygen, silica and other relevant characteristics in the water steam circuit;

(2) all sampling lines, valves (including back pressure regulation valves), filters, pumps, flanges, flow restrictors, sensors, transmitters, enclosures, water cooling equipment supply and temperature protection (including shut-off valve for excessive temperatures);

(3) final sample temperature to be 25°C +/- 1°C – secondary cooling provided as necessary;

(4) skid-mounted analysis rack incorporating mechanical connections for the mounting of monitoring and sampling equipment and for storage of Consumables;

(5) flushing for all online instruments to allow for reduction in chemistry hold and wait times;

(6) flushing, blowdown and drain collector system with appropriate connection for disposal of the used sample;

(7) suitable piping (including insulation) and flange connections to the required sampling points in the water steam circuit and water cooling system including appropriate shutoff valves (double isolation at sampling point), flow and pressure control systems;

(8) suitable electrical power and instrumentation connections to provide feedback signals to the DCS; and

(9) provision of consumable and overhaul spares for the monitoring and sampling system, as defined in Schedule 10.

The selection of monitoring and sampling at specific locations shall be based on the following table. It shall be possible to undertake both continuous on-line monitoring and laboratory grab sampling on the fluids taken at each of these locations.

Table 5 - Sampling approach

Location Type of monitoring/sampling

Boiler drum water Conductivity After cation exchange (CACE)

Sodium

Silica

Specific conductivity

pH

Phosphate (if phosphate dosing)

Table 5 - Sampling approach

Location Type of monitoring/sampling

Superheated steam Conductivity After Cation Exchange (CACE)


Degassed acid conductivity

Dissolved oxygen

Sodium (start-up)

Silica

Condenser Conductivity After Cation Exchange (CACE)

Dissolved Oxygen


pH

Acid conductivity

Degassed conductivity (air-cooled condenser only)

Make-up water Specific conductivity

Silica

Boiler feedwater Conductivity After Cation Exchange (CACE)


pH

Acid conductivity

Dissolved oxygen

The Contractor shall take into account the layout of the Plant, construction materials, and that local water quality fed to the Plant may change throughout the year, and use their experience to confirm that the specification above will capture all issues associated with variations of make-up water quality in this period with the aim of preventing excessive corrosion within the water steam circuit and damage to the turbine.

The main rack shall be designed with 20% spare capacity to mount future additional instrumentation. Materials used in the construction of the rack shall be suitably resistant to prevent corrosion throughout the Design Life of the Plant.

Instrument and electrical enclosures shall be designed with IP54 protection as a minimum, with power supplies, cables and other exposed equipment suitably designed to avoid corrosion. Instrument transmitters shall be designed with IP65 protection.

Stainless steel (316L) shall be used for all wetted parts in the sample line. Piping connections for stainless steel piping shall be via Swagelok fittings.

Stainless steel piping rather the plastic piping shall be used for the feed to the dissolved oxygen measuring equipment.

Stainless steel materials shall be used for the cooling water circuit, including all non-return and pressure relief valves, piping and flow indicators.

Sample lines shall be designed for turbulent flow during normal operation.

The cooling water valves shall be attached to a cooling water header. Between the valves and the cooler, a flexible connection shall be installed. It shall be possible to isolate the cooler from the header for maintenance.

Where a high temperature sample occurs, the system shall isolate the sample flow to protect the sampling instrumentation.

The sampling and analysis system and instrumentation shall be commissioned and operational before the boiler burners are first fired. It shall be possible to utilise the sampling system when commissioning the water treatment plant.

11 Chimney and clean flue gas duct


All items under the scope of supply should conform in every way to the relevant and latest British and European standards, codes of practice, regulations and laws applicable to chimneys, including but not limited to:

BS EN 1993-3-2: Eurocode 3 design of steel structures – chimneys

The IED

TGN M1 A2.3

TGN M2

11.2 Scope of supply

The Contractor shall design, deliver, install, integrate and commission, test and certify the following scope of supply for the complete chimney stack, including but not limited to:

(1) chimney stack, consisting of 3 individuals chimney stack installed together to appear as a single stack;

(2) liner insulation and drain;

(3) chimney top covers;

(4) flue gas inlets;

(5) flue gas duct from the output of the flue gas treatment, including the silencer;

(6) access door for cleaning;

(7) sampling points for flue gas in accordance with the Environment Agency M1 requirements, including 4 x 100NB and 4 x 50NB fitted with plug;

(8) earthing points at chimney base;

(9) aircraft warning light assemblies compliant with the appropriate CAA regulations, with cables terminating at low level junction box;

(10) access platform, with power outlets for small power and welding equipment, hoist system, safety ladder with harness and fall arrest system; and

(11) vibration damper.


A complete chimney installation shall be supplied in accordance with the Planning Application including all necessary provisions for mounting of emission monitoring equipment and for flue gas measurement and sampling by manual instrumentation.

The chimney design and height shall comply with the architect’s drawings and the requirements of the Environmental Permit.

The scope of works shall include all design, delivery, installation and commissioning of all ducting, equipment and structures necessary for the flue gas ducting network between the outlet of the flue gas treatment plant and the chimney outlet.

The chimney shall include for CEMs and Flue Gas sampling. A platform shall be included that meets the requirements of manual sample testing for personnel to manually access the chimney gases in a safe manner that accommodates all requirements of platform design as per the IED, the TGN M1 A2.3 and TGN M2.

Duty and standby aircraft warning lights on the chimney shall be supplied. The standby lamp shall automatically be lit on failure of the duty lamp. A lamp failure alarm shall be provided in the Plant control room.

The chimney flue shall have a diameter sufficient to maintain a flue gas velocity of over 15 m/s at 100% MCR.

The flue gas duct shall be adequately supported. Wind load transmitted to the flue gas duct from the chimney shall be considered in the design of the windshield and allowance for this load shall be made.

The flue gas duct shall be designed with regard to gas flow rate and strength for the given temperatures. Particular attention shall be given to thermal expansion where the flue gas ducting enters the chimney.

Corrosion resistant materials shall be used in the vicinity of the flue exit.

All parts shall be prefabricated as far as possible with flanged ends so that field erection will require only the matching and securing of connecting flanges attached to the adjacent units.

Adequately dimensioned and appropriately located cleaning and inspection ports shall be installed.

The flue gas duct shall be constructed of steel plates at least 5 mm thick or FRP/GRP depending on the flue gas conditions. Duct reinforcement can be of flat steel, and connections shall be made by means of gas-tight welded angle iron joints. Thermal expansion shall be accommodated by means of expansion joints with an internal guide plate.

All flue gas ductwork shall be thermally insulated as necessary for personnel protection. All metallic flue gas ductwork shall be insulated to prevent condensation and aluminium clad. The design of all ductwork supports shall be such as to avoid the creation of thermal bridges causing cold spots and consequent condensation within the ductwork.

(12) wind speed & direction;

(13) rain fall; and

(14) barometric pressure.

Information from the weather station should be available on a continuous real time display, either via a dedicated monitor or through the DCS. Historical data shall be available for downloading and evaluation.

11.4 Safety showers

The Contractor shall provide operational safety showers in the area of the bottom ash systems and FGT and in any other location where hazardous substances are stored and/or handled. The safety shower installations shall mitigate freeze risk in their design.

11.5 Traffic calming systems

The Contractor shall provide appropriate traffic calming measures (speed bumps or similar) in accordance with Specification Part D.

11.6 Cycle and motorcycle parking

The Contractor shall provide adequate cycle and motorcycle parking facilities with shelter in the vicinity of the staff/visitor car park area.

11.7 Heat export facility

The Contractor shall provide adequate space to fit ancillary equipment to support the installation of a district heating scheme, with a capacity of [XX] MWth at [XX] barg. The Contractor should assume that two shell and tube heat exchangers including pumps, valves and other auxiliary equipment would be installed and if possible provide space for these near to the turbine. The Contractor shall also provide adequate space to fit ancillary equipment to support the installation of a future heat export scheme.

Section X.X Pilkington Greengate Energy ... - WhatDoTheyKnow

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