Parco internship report

PAK –ARAB REFINERY LIMITED (A Pakistan-Abu Dhabi joint Venture)

Department of Utilities

MUHAMMAD ASHRAF

Internee: 22-2015

[email protected]

Institute of Chemical Engineering & Technology,

University of the Punjab Lahore.

2

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University

Internship Report on Utilities

Importance of Utility Department Utility department is the backbone of every industry. It plays an important role

in providing the uninterrupted supply of steam, instrument air, plant air, water

etc. for production purpose in every industry.

FOREWORD

Internship is a key armor in an emerging professional’s arsenal. And like in any

other aspect of life a person needs the assistance and cooperation of others

around him to achieve his objective. Despite of the fact that technological skills

are very important from industry’s point of view, engineering course outline

don’t deal with it in proper way and hence we students lag in this very

important fact.

Internship is the only way to get out of these deficiencies. My internship

at PARCO-MCR provided me the real opportunity to get practical knowledge of

my field of Engineering. PARCO-MCR is fully equipped with latest machinery

and hence it was easy for me to relate my theoretical knowledge with on-going

refinery process. In my view, my internship at PARCO-MCR is successful in all

regards and really I enjoyed my time during whole six weeks. I have tried my

level best to achieve maximum out of this opportunity and presented it in this

internship report. So, I would request you to take this as a step towards the

better and successful future.

3

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


ACKNOWLEDGEMENT

I am thankful to Almighty Allah, For His unlimited blessings and

bounties; I would first like to thank Pak Arab Refinery Company

Ltd for granting me the opportunity to pursue this Internship in an

environment that facilitated my learning.

I learnt lots of things in the period of internship and I hope

it will prove helpful in the nearby future.

I would like to acknowledge some of the persons who supported me

and some of them are

Mr. Iftikhar Ahmad

Manager Utilities and Oil Movement

Mr. Mustafa Kamal Chief Engineer Oil Movement

Mr.Rehan Siraj

Chief Engineer Utilities

Mr.Mohsin Nadeem

Group Head Utilities

Mr. Hasnain Fareed

Mentor, Engineer Utilities

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


Table of Contents 1. Introduction: ...................................................................................................................................... 10

1.1 Parco means of energy: .............................................................................................................. 10

1.2 Parco’s mid-country refinery (MCR): .......................................................................................... 10

1.3 Key features of mid-country refinery: ........................................................................................ 11

1.4 Pipeline Network:........................................................................................................................ 11

1.5 Korangi-port qasim link pipeline: ................................................................................................ 12

1.6 Products: ..................................................................................................................................... 12

Pearl quality & value: ............................................................................................................ 12

Pearl gas: ............................................................................................................................... 12

Pearl lubricants: .................................................................................................................... 12

Total parco: ........................................................................................................................... 12

2. HSE Training ...................................................................................................................................... 13

2.1 Health, Safety & Environment: ................................................................................................... 13

2.2 HSE objectives: ............................................................................................................................ 13

2.3 Why Safety is Necessary? ........................................................................................................... 13

2.4 Fire: ............................................................................................................................................. 13

2.5 Necessary Objects for fire: .......................................................................................................... 14

2.6 Classes of fire: ............................................................................................................................. 14

2.7 Products of Fire: .......................................................................................................................... 14

2.8 Fire Extensions: ........................................................................................................................... 14

2.9 Hazard: ........................................................................................................................................ 15

2.9.1 Hazards in the oil refinery: ................................................................................................... 15

2.9.2 How to minimize hazards: .................................................................................................... 15

2.9.3 Solid Waste Hazardous: ....................................................................................................... 15

2.10 Emergency Response Plane: ..................................................................................................... 15

2.10.1 Types of Emergencies: ....................................................................................................... 15

2.11 Categorization: .......................................................................................................................... 16

2.12 Incident Reporting System: ....................................................................................................... 16

2.12.1 Incident Reporting in Industries:........................................................................................ 16

2.13 Near miss: ................................................................................................................................. 16

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


2.13.1 Types of Near miss: ............................................................................................................ 16

2.14 PARCO Policy Statement: .......................................................................................................... 17

2.15 Permit to work system (ptw): ................................................................................................... 17

2.15.1 Why is permit necessary? ................................................................................................. 17

2.15.2 Jobs which require Permit: ................................................................................................ 17

2.16 Personal Protective Equipments: .............................................................................................. 17

2.16.1 Type of PPE’s:- .................................................................................................................... 18

2.17 Fire System: ............................................................................................................................... 19

3. Abbreviations: ................................................................................................................................... 21

4. Chemical Handling (Unit 900) ........................................................................................................... 22

4.1 Caustic Soda Distribution System: .............................................................................................. 22

4.2 Sulfuric Acid Distribution System: ............................................................................................... 22

4.3 Material Balance: ........................................................................................................................ 22

4.4 Sulfuric Acid Consumption: ......................................................................................................... 23

4.5 Caustic System: ........................................................................................................................... 23

4.6 Sulfuric Acid System: ................................................................................................................... 23

4.7 Different Conditions/Terms: ....................................................................................................... 24

4.7.1 Pressure Testing: .................................................................................................................. 24

4.7.2 Flushing Out: ........................................................................................................................ 24

4.7.3 Utilities Requirement for U-900:.......................................................................................... 24

4.7.4 Possible Emergency Situation in U-900: .............................................................................. 24

5. Plant and Instrument Air (Unit 910).................................................................................................. 25

5.1 Process Description: .................................................................................................................... 25

5.2 Air Dryer Train: ............................................................................................................................ 26

5.3 Utilities required at U-910: ......................................................................................................... 27

5.4 Emergencies: ............................................................................................................................... 27

5.5 Users of Plant and Instrument Air: ............................................................................................. 27

6. Flare System (Unit 915) ..................................................................................................................... 28

6.1 Design Basis:................................................................................................................................ 28

6.2 Relieving sources:........................................................................................................................ 28

6.2.1 Main flare system: ............................................................................................................... 28

6.2.2 Acid gas flare system: ........................................................................................................... 28

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


6.3 Major Equipments: ..................................................................................................................... 29

6.4 Process Description: .................................................................................................................... 29

6.4.1 Main flare: ............................................................................................................................ 29

6.4.2 Acid Flare:............................................................................................................................. 30

6.5 Jump over lines: .......................................................................................................................... 30

6.6 Utility Requirement:.................................................................................................................... 30

6.7 Emergency Conditions: ............................................................................................................... 30

7. Fuel Oil and Fuel Gas System (Unit 9200 .......................................................................................... 31

7.1 Fuel Oil System: ........................................................................................................................... 31

7.1.1 Refinery Fuel Oil Producers:................................................................................................. 31

7.1.2 Refinery Fuel Oil Consumers: ............................................................................................... 31

7.1.3 Header Condition: ................................................................................................................ 31

7.1.4 Major Equipments: .............................................................................................................. 31

7.1.5 Process Description: ............................................................................................................. 32

7.1.6 Utilities: ................................................................................................................................ 32

7.1.7 Emergencies: ........................................................................................................................ 33

7.2 Fuel Gas System: ......................................................................................................................... 33

7.2.1 Fuel Gas Sources: ................................................................................................................. 33

7.2.2 Priorities of RFG Header Sources: ........................................................................................ 33

7.2.3 Fuel Gas Consumers: ............................................................................................................ 33

7.2.4 Major Equipments: .............................................................................................................. 33

7.2.5 Process Description: ............................................................................................................. 34

7.2.6 RFG Header Pressure Control: ............................................................................................. 34

7.2.7 Utilities: ................................................................................................................................ 34

7.2.8 Emergencies: ........................................................................................................................ 34

8. Raw, Plant, Potable water system (Unit 925) ................................................................................... 35

8.1 Well Pumps System ..................................................................................................................... 35

8.1.1 Normal Operation ................................................................................................................ 35

8.1.2 Six Pump Operation ............................................................................................................. 35

8.2 Raw Water................................................................................................................................... 35

8.2.1 Raw Water Tanks (925-TK1A/B) ........................................................................................... 35

8.2.2 Raw Water Supply Pumps (925-P7A/B/C) ............................................................................ 36

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


8.3 Plant Water: ................................................................................................................................ 36

8.4 Potable Water System ................................................................................................................ 36

8.4.1 Potable water filter system (925-ME1) ................................................................................ 36

8.4.2 Potable Water Storage Tank (925-TK2) ............................................................................... 36

8.4.3 Potable Water Supply Pumps (925-P9A/B) .......................................................................... 37

8.5 Cooling Water (C.W.) System: ..................................................................................................... 37

8.5.1 Cooling Tower (925-T1) ........................................................................................................ 37

8.5.2 Principle of Operation: ......................................................................................................... 37

8.5.3 Configuration of cooling system in PARCO .......................................................................... 38

8.5.4 Cooling Water Circulation Pumps (925-P10A/B/C) .............................................................. 38

8.5.5 Side stream filters (925-ME2A/B/C)..................................................................................... 38

8.5.6 Chemical Injection ................................................................................................................ 38

8.6 Controls and Emergencies for Cooling Water System ................................................................ 39

8.6.1 control System: .................................................................................................................... 39

8.6.2 Emergencies: ........................................................................................................................ 39

8.7 Effluents of U-925 ....................................................................................................................... 39

8.8 Utilities required at U-925 .......................................................................................................... 40

9. Fire Water System (Unit 926) ............................................................................................................ 41

9.1 Fire Water Tank 926-TK1: ........................................................................................................... 41

9.2 Fire Water Distribution System:.................................................................................................. 41

9.3 Fire Water Main Pumps 926-P1A/B/C/D: ................................................................................... 41

9.4 Jockey Pumps 926-P2A/B: ........................................................................................................... 41

9.5 Fire Water Main distributing System:- ........................................................................................ 41

9.6 Fixed open head water spray system: ........................................................................................ 42

9.7 Semi Fixed Foam Extinguishing System: ..................................................................................... 42

9.8 Semi Fixed Foam Extinguish System for Outdoor Oil Storage Tanks: ......................................... 42

9.9 Hose Houses: ............................................................................................................................... 42

9.10 Potable & Wheeled Fire Extinguishers: .................................................................................... 42

9.11 FM-200 system for buildings: ................................................................................................... 42

9.11.1 Fire & Gas Detection System with Fire Alarm: ................................................................... 42

9.11.2 Outdoor Manual Alarm Call Points: ................................................................................... 42

9.11.3 Gas Detectors: .................................................................................................................... 42

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


10. Effluent Treatment Plant (Unit 930) ............................................................................................... 43

10.1 Major equipment: ..................................................................................................................... 43

10.2 Oily Waste Water Treatment System: ...................................................................................... 43

10.2.1 API oil/water separator section: ........................................................................................ 44

10.2.2 API Scraper Mechanism: .................................................................................................... 44

10.2.3 Equalization Tank: .............................................................................................................. 45

10.2.4 Dissolved Air Floatation DAF: ............................................................................................. 45

10.2.5 Biological Aeration & Clarification: .................................................................................... 47

10.2.6 Filtering Process Description: ............................................................................................ 48

10.3 Oily Sludge Treatment System: ................................................................................................. 49

10.4 Biological Sludge Handling System: .......................................................................................... 50

10.5 Sanitary Waste Water Treatment System: ............................................................................... 51

11. Demineralized water and Boiler System: ........................................................................................ 52

11.1 Equipments List: ........................................................................................................................ 52

11.2 Boiler Make Up Water Treating System: .................................................................................. 52

11.2.1 Process Descruption: ......................................................................................................... 53

11.3 Condensate Recovery Section:- ................................................................................................ 54

11.3.1 High Pressure Condensate (HP Condensate): .................................................................... 54

11.3.2 Medium Pressure Condensate: .......................................................................................... 54

11.3.3 Low Pressure Condensate: ................................................................................................. 54

11.3.4 Cold Condensate: ............................................................................................................... 54

11.4 Deaerator Section: .................................................................................................................... 55

11.5 Boiler Section: ........................................................................................................................... 55

11.5.1 Boiler Feed Water Conditions: ........................................................................................... 55

11.5.2 Boiler and Steam Headers:................................................................................................. 56

11.5.3 Chemical Dosing for Boiler Feed Water: ............................................................................ 56

11.5.4 Boiler Parts: ........................................................................................................................ 57

11.6 Steam Let Down Section: .......................................................................................................... 60

12. Assignments .................................................................................................................................... 61

12.1 Assignment # 01 ........................................................................................................................ 61

12.2 Assignment # 02 ........................................................................................................................ 68

12.3 Assignment # 03 ........................................................................................................................ 70

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


No. of Tables: ........................................................................................................................................ 72

Bibliography .......................................................................................................................................... 73

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


1. Introduction: PARCO-Incorporated in Pakistan in May 1974, as a Public Limited Company, PARCO is a 60:40

joint venture between the Governments of Pakistan & Abu Dhabi, having paid-up capital of Rs.11.6

billion and total equity of Rs.37.2 billion with annual revenues of over Rs. 46 billion and an asset

base approaching Rs. 100 billion.

It was the first AAA rated Company by PACRO in the country and continues to command that credit

worthiness for an unprecedented seventh year running. PARCO’s Board is made up of six

GOP Directors including the Chairman and the Managing Director and four Abu Dhabi

Directors representing ADPI.

1.1 Parco means of energy: PARCO as an energy company is a key player in the country’s strategic oil supply and its

logistics. With the synergy of a comprehensive and expanding oil pipeline network, integrated with a

significant and modern refining capability, PARCO has emerged as the strategic fuel supplier to the

county. PARCO’s competitive advantages through the integration of pipeline operation, strategic

storage, leading edge refining and a significant role in marketing of petroleum products, have

enabled it to achieve a position in the energy supply chain.

1.2 Parco’s mid-country refinery (MCR): PARCO’s 100,000 BPD, state-of-the-art Mid-Country Refinery at Mahmood Kot, completed at

a cost of US$ 886 million, represents more than 40% of the indigenous refining capacity of

the country.

It helps substitute imports of refined value added oil products to the tune of US$ 100

million per year. The company set another first when it recently obtained three simultaneous

international certification: ISO 9001:2000 (Quality Management System), ISO 14001:2004

(Environmental Management System) and OHSAS 18001:1999 (occupational Health and Safety

Management System) for its Mid-Country Refinery. Within a few months, all three certifications

were achieved for the Pipeline Division as well.

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


1.3 Key features of mid-country refinery:

1.4 Pipeline Network: The refined petroleum products transport logistics on road and rail and the existing pipeline

network. The surface transport mode is potentially hazards to other traffic, human lives and the

environment besides wear and tear of road surfaces. PARCO’s pipeline network is a safer and more

cost effective alternative for both crude and product transportation. With the completion of the

White Oil Pipeline in about two years, a more comprehensive, safer, cost effective, demand

responsive and eco-friendly pipeline network will be available to meet the country’s growing needs

for energy.

PARCO’s 864-km Karachi-Mahmood Kot pipeline, having the initial annual pumping capacity of 2.9

million tons, with technological up gradation of the system is now capable of pumping up to 6.0

million tons. In June 1997, PARCO completed its 360-km MFM (Mahmood kot-Faisalabad

Machhike) Pipeline Extension Project. The Project design allows for future spur line from Faisalabad

to Kharian and Sahiwal.

Location QasbaGujrat / MahmoodKot

Project Cost US $ 886 million

Main Supply & ConstructionContractors

JGC & Marubeni Corp.

Completion Period 36 months

First Crude in Pipeline August 03, 2000

First Crude at Refinery August 25, 2000

First Product out and Commissioning

September 04, 2000

Formal Commissioning February 2001

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


1.5 Korangi-port qasim link pipeline: The 22-kilometer long, 26” diameter pipeline linking PARCO’s Korangi station with

PAPCO’s Port Qasim station has been commissioned in March 2006. The strategic link has

connected both the Karachi ports (Keamari as well as Port Qasim) with PARCO and

PAPCO pipeline systems, providing flexibility in pipeline operations to receive crude as well

as product from either port.

1.6 Products:

Pearl quality & value:

PARCO is engaged in its marketing additives though “PEARL” is associated with

symbol of purity and preciousness which translates to a message of quality and value for

petroleum products.

Pearl gas:

MCR is producing almost 150,000 metric tons of LPG every year. In order to Self

Market under the brand name of “Pearl Gas” PARCO has signed Technical services and

support agreement (TSSA) with the Dutch Company SHV, who is marketing 25 % of the

product.

Pearl lubricants:

PARCO has been marketing OMV lubricants imported from Austria which are already

available in the local markets.

Total parco:

A Total-PARCO Pakistan Ltd. Joint venture company has been formed to market 25%

of MCR production, through retail outlets.

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


2. HSE Training

2.1 Health, Safety & Environment: HSE plays an important role in health and safety of the employees to keep environment

clean. Basically the nature of industrial environment is destructive. It is practically impossible to

eliminate the hazards. The new dare for us to reduce the hazards and how to deal with them

spontaneously.

The health, safety and environment department plays a vital role in most of the MCR’s

activities. The department is not only concern with the health of its employees, workers and

technicians but also provide them same conditions to work in different places of fields. In the MCR, a

separate department is responsible to take care of these activities and provide healthy environment

to its employees to accomplish their respective tasks.

2.2 HSE objectives: The object of the laws is also to regulate workers and the provisions act clearly show that

the said regulations are intended for the benefit & welfare. The basic aims of HSE department are

Eliminating of accidents.

Protecting the assets (equipment).

Avoid Business Interruption.

Complying with legislation.

2.3 Why Safety is Necessary? Safety is a matter for everyone. It is a well-recognized fact. Everyone has a role to play when

life and health are at stake.

Accident hurt people.

To provide healthy environment for staff to work in organization.

Cost of accidents.

Reputation and recognition of organization.

To save human lives.

2.4 Fire: A Chemical reaction in which fuel chemically combines with an oxidizing agent and sufficient

quantity of energy in the form of heat, flame, light etc is released.

Examples:

Rapid oxidation process.

Hydrocarbon industry.

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


2.5 Necessary Objects for fire: Fuel:

Fuel is converted to vapors to burn.

Proportion of vapors must be in proper flammable range to burn

Oxygen:

Air contains 21% oxygen.

At least 16% oxygen is required to sustain life and combustion.

Ignition Source:

It includes mechanical process, and electrical resistances.

Examples:

Reaction between two chemicals.

Heating of electrical appliances.

Radiation.

Two metals rubbed.

2.6 Classes of fire: Class A Solid Cloth, Paper, Wood Water

Class B Liquid-Gas Flammable liquid and gas, gasoline, kerosene, Diesel and Natural gas etc

Foam & DCP (Dry Chemical Powder).

Class C Electric Cables, Transformer, Sockets, Electrical panels, Overloading, Electrical Appliances.

CO2, Halotron

Class D Metals Na, K, Uranium Metal-X

2.7 Products of Fire: Thermal Products (Heat & Flame)

Non-Thermal Products (Smoke & Toxic Gases)

2.8 Fire Extensions: Cooling

Smothering

Starvation

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


2.9 Hazard: A dangerous or otherwise unwanted outcome, especially one resulting from the failure of an

engineered system.

2.9.1 Hazards in the oil refinery:

Following are the different hazards in the oil refinery.

Fire Hazard

Toxic Gas Hazard

Height Hazard

Slip Hazard

Trip Hazard

Electrical Shock Hazard

Chemical Hazard

HSE trains the employees how to deal with the hazards without having an accident.

2.9.2 How to minimize hazards:

Hazards can be reduced by having such precautions

Engineering Controls

Administrative Controls

Decision Making Sense

Personal Protection

2.9.3 Solid Waste Hazardous:

Flammability.

Corrosively.

Reactivity

Toxicity

2.10 Emergency Response Plane: An emergency response plane is a plane of action for the efficient deployment and

coordination of services, agencies and personnel to provide the earliest possible response to an

emergency.

2.10.1 Types of Emergencies:

Fire

Spills

Toxic Gas

Bomb Threats

Floods

Earthquakes

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


2.11 Categorization: Minor Accidents:

Accidents which are controllable by people on site.

Serious Accidents:

Accidents which are controllable by internal source.

Major accident:

Accidents which are controllable by mutual aid partners.

Disaster:

Those accidents which are not controllable by internal source and mutual aid partners.

2.12 Incident Reporting System: An incident report is a form that is filled out in order to record details of an unusual event

that occurs at the facility, such as an injury to a person.

e.g Soil pollution, Environmental pollution.

2.12.1 Incident Reporting in Industries:

Injury

Accident

Near miss

2.13 Near miss: Any potential which can change or disturb the person.

2.13.1 Types of Near miss:

Unsafe Act: e.g Hitting hammer on anything and suddenly hammer looses and hit the nearest

person

Unsafe Condition: e.g. Anything falling from roof and hit the person.

Fatality: 1

Major Accidents: 10

Minor Accidents: 30

Near misses: 600

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


From the above reporting system, If the near missies in any industry are less then the ratio

of major accidents or injuries will be greater. So, near misses should be greater.

2.14 PARCO Policy Statement: HSE are considered at PAR profitably, productivity and Quality.

There should be competent, trained and responsible persons in PARCO.

All activities are adequately resourced and carried out by trained and competent persons.

Modifications, Reviews, approvals of operations.

Quality assurance.

Contractor’s management.

Risk Assessment.

Legal Requirements.

Change the management.

Continual process.

2.15 Permit to work system (ptw): Formal written system to control potentially hazardous work.

2.15.1 Why is permit necessary?

Hydrocarbons and toxic materials possesses high risk for personnel’s health, and risk of fire,

also the maintenance personnel is not familiar with the process conditions, the basic purpose of

permit system is to prevent injuries to workers, property damage can also be minimized by permit

system, permit contains the specific conditions and procedure for the safe execution

2.15.2 Jobs which require Permit:

Permit is normally required for the following procedures:

Maintenance work

Construction

Alteration

Equipment cleaning

Entry into confined space

Excavation

Mobile machine/ vehicle entry into hazardous areas etc.

Road closure

2.16 Personal Protective Equipments: The use of PPE’s can protect the employees from the risk of injury by creating a barrier

against work place hazards. All the industries do not provide their employees with the PPE’s but as

health and safety of the employees is first priority of the MCR administration so all the employees

are provided with PPE’s and no employee is allowed to enter the plant area without wearing these

PPE’s. The proper usage of PPE’s reduces the risk of hazards and ultimately resulting in the less

number of the accidents in the refinery.

18

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


2.16.1 Type of PPE’s:-

In MCR following type of PPE’s are in use for protection

Hearing Protection

Sight Protection

Respiratory Protection

Foot Protection

Head Protection

Hand Protection

Hearing Protection:

Hearing loss is the common work place injury, and is too often ignored because it usually

happens gradually a period of time. The threshold value of noise to bear for a normal person is

about 85 dB. However, in the industry sometimes the noise level even goes above 100 dB, thus

causing the problem for the person is hearing. Ear plugs offer the most protection to our ears from

noise and can compensate the noise level to 26 dB. It is small in diameter and easy to use.

Sight Protection:

In order to protect the workers from flying particles, liquids, vapors, glasses, molten metal

and acid, the workers are provided with GOGGLES, FACE SHIEL and SAFETY GLASSES.

Respiratory Protection:

To protect the workers at refinery from inhalation of airborne dust chemical vapor or fumes,

and toxic gases, air purifying respiratory systems are provided. Half face and full face masks are used

for the respiratory protection.

Foot Protection:

In order to protect the foot of the workers at MCR, they are provided with a specially

designed Metal toe shoes. This show protects them from falling or rolling objects, slippery

walking surfaces and hazardous chemicals. In order to meet with the problems of high

voltages the workers are also provided with the special shoes rubber or synthetic foot wear

may be required around chemicals and static charge. If working around electrical wires

shoes must be metal free or non-conductive.

Head Protection:

Head protection is necessary to provide the workers with the safety against falling

objects, low hanging obstructions and exposed current conductors. Hard hats are tested to

withstand the impact of weight of 8LB dropped from 5ft.

Hand Protection:

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


For any employee, the hands are the only source of his income and to protect the

hands from absorption of harmful material, severe cuts, punctures and chemical burns, vinyl

or neoprene gloves are used. Leather or cotton knitted gloves is for handling abrasive or

sharp objects.

Gas Masks:

Air is the basic element for humans to survive. But contaminated atmosphere caused

by dust, vapor or fumes. Breathing in this sometimes workers have to work in the

contaminate air can cause serious illness and even the death due to suffocation.

2.17 Fire System:

Fire management system

Fire prevention

Fire detection

Fire suppression

Fire Fighting

Emergency Response

Communication

Training

Prevention:

Hot Work permits procedure.

Testing & inspection of fire equipment.

Lightening Arrestors.

House Keeping

Non Static Charge producing clothes

Hazardous Area Classification

Floating Roof Tanks

Detection:

Heat Detectors

Smoke Detectors

UV/IR Flame Detectors (Ultra Violet /Infra-red detectors)

HSSD (High Sensitive Smoke Detectors).

Hydrocarbon Detectors.

Hydrogen Sulfide Detectors

Vigilance Employees.

Suppression:

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


FM-200 (Hepta Fluoro Propane Gas) fire suppression system installed in CR-1, SS-1 & SSB

sections.

Deluge Valve System (Auto & Semi Auto System)

Automatic System ( at product pumps)

Semi Auto System (at fin fan, cooler, TLG, area’s)

FM-200 is ozone & human friendly gas. It is imported from United States in cylinders. It is

filled about a pressure of 140-145 kg/cm2 in cylinders.

Fire Fighting:

Fire Trucks.

Fire Hydrants

Fire Monitors

Fire Houses

Ground Monitors

Fire Suit

Fire Extinguisher

Emergency Panels

Ladders

Drills

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


3. Abbreviations: BPSD Barrels Per Stream Day

BFW Boiler Feed Water

DMW Demineralized Water

ETP Effluent Treatment Plant

IV Inlet Valve

UV Unloading Valve

ME Miscellaneous Equipment

CCR Continuous Catalyst Regeneration

LPG Liquefied Petroleum Gas

LP Low Pressure Steam

MP Medium Pressure Steam

HP High Pressure Steam

LC Low Pressure Condensate

MC Medium Pressure Condensate

HC High Pressure Condensate

CC Cold Condensate

TSD Technical Services Department

RFO Refinery Fuel Oil

RFG Refinery Fuel Gas

FOR Fuel Oil Return

FOS Fuel Oil Supply

22

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


4. Chemical Handling (Unit 900) Unit-900 is composed of 2 units

25 Be Caustic Soda Handling System

98 wt %Sulfuric Acid Handling system

50 wt.% caustic soda and sulfuric acid system are required by the different users in the oil refinery

which are met by unit-900 of utilities.

4.1 Caustic Soda Distribution System: 50 wt % caustic soda is unloaded from the 10 metric ton container and then introduced into

tank 900-TK1A and 900-TK1B. These tanks are filled in such a way that 5 metric ton of caustic soda

transferred to each caustic soda storage tank. There are 2 pumps 900-P1A & 900-P1B which played

an important role in transferring the caustic soda to storage tanks. Caustic soda when introduced

into the storage tanks have the capacity of about 50 Be which need to be reduced to 25 Be by adding

demineralized water into both storage tanks. Part of the 50 wt. % caustic soda with a strength of

about 25 Be is diluted to 10 Be in tank (801-TK1) and a part of 10 Be will be diluted to 3 Be in 801-

TK2 for kerosene merox unit in Area-500 for purifying different fractions.

4.2 Sulfuric Acid Distribution System: Sulfuric acid is unloaded from the 5 metric ton container via sulfuric acid unloading pumps

900-P3A and 900-P3B. These pumps not only unload it but also pumped to vessel 900-V1. It is then

distributed to various users of the refinery via distributing pumps 900-P4A and 900-P4B.

4.3 Material Balance: The theoretical balance for caustic soda and sulfuric acid system are tabulated below.

Table 1

Unit Consumption Strength Utility 2.1 m3/day 25 Be ETP 0.06 m3/hr 25 Be

K-MX 0.2 m3/hr 25 Be LPG-MX 3.14m3/week 25 Be

CCR 0.34 m3/10 years 25 Be NHTR 1.6 m3/hr/week 25 Be Amine 0.66 m3/hr/week 25 Be D-Max 984 m3/172hrs/year 25 Be

K-MX(ELEC) 8 m3/week 25 Be TOTAL 1.9 m3/day average 50 wt %

23

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


4.4 Sulfuric Acid Consumption: Table 2

Unit Consumption

Utility Boiler Makeup Water System 640L/day average

Cooling Water System 72 L/day average Spent Caustic Section 8.5 m3/hr/week

Total 1.9 m3/day average

4.5 Caustic System: The 50wt% caustic unloading pumps (900-P1A/B) shall transfer the caustic to 25oBe caustic

tanks (900-TK1A/B) which have demineralized water in advance to dilute 50wt% caustic to 25oBe

caustic. The 50wt% caustic unloading pumps shall circulate the caustic solution for mixing.

25oBe caustic is transferred to each user by 25oBe caustic pump (900-P2A/B) which is running

normally. Two of caustic tanks cover approximately 21 days of normal demand of users.

Table 3

Equipment Tag Equipment name Specifications

900TK1 A/B 250 Be Caustic Soda Storage Tanks Total Capacity: 103 m3

Working Capacity: 88.5 m3

900P1 A/B 50 wt.% NaOH Unloading Pumps Motor driven Single stage centrifugal type

900P2 A/B 250 Be NaOH Pumps Motor driven Single stage centrifugal type

900FV021 Min. Flow Control Valve Pneumatically operated control valve

4.6 Sulfuric Acid System: The sulfuric acid transfer pumps (900-P3A/B) shall transfer the sulfuric acid (98wt%) to a

sulfuric acid vessel (900-V1). The sizing of the sulfuric acid vessel is based on maximum demands

from the Boiler Makeup Water Treatment System in the Steam, Feed water and Condensate

Handling System, from Cooling Tower and from Spent Caustic Section at ETP.

Sulfuric acid injection tank at Cooling Tower System will be filled the sulfuric acid from the sulfuric

acid vessel (900-V1) directory. The sulfuric acid process pumps (900-P4A/B) shall run intermittently

to fill the sulfuric acid vessel in the Spent Caustic Neutralization Section at ETP and the Boiler

Makeup Water Treating System.

The sulfuric acid vessel covers approximately one month of normal demand of users.

24

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


Table 4

Equipment Tag Equipment Name Specification

900 V1 H2S04 Storage vessel Stainless Steel Nominal Capacity: 65 m3

900P3 A/B H2S04 unloading pumps Motor driven Single stage centrifugal type

900P4 A/B H2S04 distribution pumps Motor driven Single stage centrifugal type

900 LG001 Level Gauge Magnetic type

4.7 Different Conditions/Terms:

4.7.1 Pressure Testing:

The equipment must be tested for hydrostatic pressure before using for process which is

done by filling it with the water. The strainers are placed in the path of water so that particles

removed from it and then introduced in the equipment. Hydrostatic pressure testing is necessary in

order to check that it is suitable for holding pressure of the liquid or not.

4.7.2 Flushing Out:

Water is circulated for the purpose of removing any dirt, scale etc. Screens should be placed

between the flange of suction and pump which helpful in removing dirty particles and also it is easily

removable from the system. All possible lines, valves and pumps should be thoroughly washed with

water to use it for handling purpose. The fire water system can be used for flushing the entire plant

but need to be treated first for cleaning purpose. Before flushing open overhead vents (to avoid

vacuum), disconnect pump suction and discharge.

4.7.3 Utilities Requirement for U-900:

Plant Water – Cooling of mechanical seals of pumps; washing in case of spillage DMW – For

dilution of NaOH from 50 wt. % to 250 Be Instrument air- For 900FV021 operation; bubbler type level

indicator on 900V1; for maintaining positive pressure in vapor space of 900V1

4.7.4 Possible Emergency Situation in U-900:

Chemical spillage is dealt with immense care and the area is epoxy coated. In case of spillage

the affected area is washed with plenty of water and spilled chemical is directed to neutralization pit

of ETP by virtue of its design.

25

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


5. Plant and Instrument Air (Unit 910) This unit consists of following two sections:

1. Air Compressor Package Section:

This section consists of two centrifugal compressors for fulfilling the requirements of

plant air and instrument air in refinery. These are three stage centrifugal compressors; one is

motor driven, which is normally in operation, while other one is steam turbine driven, while

normally remains on hot standby. Both compressors take atmospheric air and compress it to

header conditions.

2. Air Dryer Package Section:

It consists of a dryer train, which is used to remove moisture from compressed air to

make it suitable for its use as instrument air. This system consists of pre-filters, dryer vessels

(containing alumina desiccant) and after filters.

The detailed process description and an account of major equipment involved is given below:

5.1 Process Description:

Atmospheric air is compressed by a 3-stage centrifugal compressor which is sent to main air

receiver at 8.7 kg/cm2G. From main air receiver, plant air is supplied to plant air header, and to air

dryer train, which removes moisture from air to make it suitable to be used as instrument air.

The dried (instrument) air is sent to instrument air receiver which supplies instrument air to

instrument air header.

910-C1A takes its suction from atmosphere through a suction filter and IV (Inlet Valve),

which controls the inlet air flow. The air entering is at a pressure of ~0.8 kg/cm2 G.

910-C1A compresses the air through three stages.

0.8 kg/cm2G (atmospheric air) → Stage 1 → 1.5 kg/cm2G → Stage 2 → 5.0 kg/cm2G → Stage

3 → 8.7 kg/cm2G

Interstage coolers remove heat of compression of the compressed air after first and second

stage and an after-cooler after third stage, using cooling water.

Moisture separators are installed after each interstage and after- coolers to remove

condensed moisture.

IV and UV (Unloading Valve) are installed on inlet and outlet lines of the compressor for

regulating system parameters and to prevent the compressor from surging and other

problems.

In normal operation, C1A is in service while C1B is on hot standby.

The compressed air at 8.7 kg/cm2G is received in the main air receiver 910-V1 which acts a

storage and distribution system for plant air header as well as air dryer section.

A bypass line for 910-V1 is also available

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


Moist air from 910-V1 is sent to air dryer section 910-ME1. This section consists of two dryer

trains, one in service and other on standby. The switch-over between the two trains occurs

fortnightly.

Each train consists of a pre-filter, dryer vessel and an after-filter.

5.2 Air Dryer Train:

Plant air from 910-V1 enters the pre-filter (910-ME1-V2) which filters out water, oil mist and

dust particles down to 0.3µm. After pre-filter, plant air enters the dryer vessel (910-ME1-V1)

from bottom and flows upwards through the desiccant bed. This bed consists of activated

alumina (Al2O3) balls (~2mm dia.). Moisture from the plant air is adsorbed on these alumina

balls. The dried air leaving from the top of the vessel is suitable for its use as instrument air.

This instrument air is routed to instrument air receiver (910-V2), while a part of it is used for

regeneration of the other dryer vessel. In each dryer train there are two drying vessels; one

in service other on regeneration. When Al2O3 balls come in equilibrium with wet air, these

are regenerated. The regeneration cycle proceeds as follows:

i. Depressurizing

ii. Regeneration

iii. Pressurizing

iv. Parallel drying

v. Switch over

Table 5

Equipment Tag Equipment Name Specifications of A & B

910-C1A/B Air Compressors

3 Stage centrifugal compressor Capacity: 6000 Nm3/hr. (each) Discharge Pressure: 8.7 kg/cm2G 2 interstage coolers and 1 after cooler C1A – motor driven (631.8 KW) C1B – steam turbine driven (12.6 t/hr. HS)

910-V1 Main Air Receiver

For storage of plant air Length: 5900 mm Internal Dia:2900 mm Design Pressure: 11.25 kg/cm2G Design Temperature: 1100C

910-V2 Instrument Air Receiver

For storage of instrument air Length: 7000 mm Internal Dia:3500 mm Design Pressure: 11.25 kg/cm2G Design Temperature: 1100C

910-ME1 Air Dryer Package

Capacity: 4168 Nm3/hr. Min. Discharge Pressure: 7.7 kg/cm2G Dew Point: -200C at 7.0 kg/cm2G Design Pressure: 11.25 kg/cm2G Design Temperature: 1200C

27

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


910-ME1-V1A/B/C/D Dryers Contain Al2O3 desiccant Weight of desiccant: 1.075 tons/vessel

910-ME1-V2A/B Pre-filter For removal of moisture, oil mist and dust particles down to 0.3µm

910-ME1-V3A/B After filter For removal of desiccant’s dust particle down to 1µm

910-C1B-ST Steam Turbine Drives 910-C1B Back pressure turbine Feed: HS at 12.6 t/hr.

A dew point analyzer is also installed for continuous monitoring of dew point of instrument air.

5.3 Utilities required at U-910: Electricity – Air compressor motor (613.8KW) and panel (1KW)

Steam – High pressure steam (12.6 t/hr.)

Cooling water – compressors (interstage, after stage and lube oil cooler at 195.1 m3/hr.)

Instrument air – panel and instrumentation (191 Nm3/hr.)

Plant Air – air dryer (470 Nm3/hr.)

5.4 Emergencies: Steams failure

Power failure

Instrument air failure

5.5 Users of Plant and Instrument Air: Plant Air – utilities, ETP, DMW Plant

Instrument air – all units

28

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


6. Flare System (Unit 915) The flare system is designed to handle normal gas release and the emergency gas & liquid

release from the refinery. This system consists of main flare system and the acid flare system,

capacity of each system is as follow:

Main flare system: 950 tons/hr. (General power failure case)

Acid gas flare system: 48.6 tons/hr. (Diesel max CV failure case open)

6.1 Design Basis: Main flare is designed

To combust relief valve discharges

Normal process vents

Acid flare is for combusting gases containing hydrogen sulfide.

6.2 Relieving sources:

6.2.1 Main flare system:

Relieving vapor and liquid from the following unit are collected to main flare system:

Crude Distillation Unit

Vacuum Distillation Unit

Gas Concentration Process Unit

Visbreaking Process Unit

Diesel Max Process Unit

Platforming Process Unit

Platforming Process Unit CCR Section

Naphtha Hydro-treating Process Unit

Kerosene Merox Process Unit

LPG Merox Process Unit

Fuel Gas System

LPG Sphere Tanks

Boiler Section in Utility Facilities

6.2.2 Acid gas flare system:

Relieving vapor and liquid from the following units are collected to acid gas flare system:

Diesel Max Process Unit

Amine Treating Process Unit

Sulfur Recovery Unit

Effluent Collection, Treatment and Disposal System

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


6.3 Major Equipments: Table 6

Equipment Tag

Equipment Name

Internal Dia.

(mm)

Total Length (mm)

Design Temperature

(oC)

Design Pressure

(Kg/cm2 G)

915-V1 Knockout Drum 5500 18000 3.5 338

915-V2 Knockout Drum 1220 3900 3.5 210

915-ME1 Main flare stack 48” 112000 3.5 338

915-ME2 Acid flare stack 14” 11200 3.5 210

915-P1A/B Centrifugal Pump

11.4 0.27 5.54 50

915-P2A/B Centrifugal Pump

5.0 0.29 5.56 50

6.4 Process Description:

6.4.1 Main flare:

It is designed to collect normal gas release and the emergency gas & liquid release from the refinery.

Normal process vents and PSV discharges from their respective sources are collected in main

flare header. This header feeds 915-V1 main flare knockout drum to separate water, liquid

hydrocarbons from vapors.

In 915-V1 water is collected in boot from which it is drained to off water sewer. The

collected oil is pumped to LSL tank 945-TK47 via 915-P1A/B which auto cut in based on level

of oily water in the boot.

Just beneath the downstream of the vapor outlet from 915-V1; is a drain pot for further

separation of any entrained moisture/HC liquid. The liquid from drain pot is pumped back to

915-V1 via N2 pumping trap. This liquid becomes part of LSL.

The outlet vapor stream from 915-V1 is routed to 915-ME1 (main flare stack) before stack

there is a water seal drum. The gases from 915-V1 are bubbled through the water seal drum

which is meant to prevent flashback. The water in water seal drum is continuously

replenished by plant water. after passing through the water seal drum the gases are

combusted at the flare tip.

For ensuring safety against flame off condition, 915-ME1 is installed with four pilot burners

which are continuously supplied with natural gas and instrument air mixture.

The gas seal is also available in main flare stack as a protective measure to prevent flashback

by maintaining a positive pressure of fuel gas in the main flare header.

For smokeless flame, MP steam is injected into the main flare. The flare tip is provided with

a steam ring for this smokeless flame operation. For 55000 kg/hr. of gases 21000 kg/hr. MP

steam is provided.

30

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


6.4.2 Acid Flare:

From relieving sources of acid gases to the acid gases to the acid flare header, these are

routed to knockout drum 915-V2 which is a liquid vapor separator. The collected sour water

at the bottom of the vessel is pumped to sour water degassing drum (810-V10) via 915-

P2A/B which are auto cut in.

The vapor stream is routed to 915-ME2 (Acid gas flare stack). This stack is also equipped with

water seal drum and dry gas seal which operate in the same way as in case of main flare

system.

The acid gas header and stack are steam traced to prevent condensation of water which

would otherwise combine with H2S to form H2SO4.

6.5 Jump over lines: i. Potable water-Plant water jump over line (used in case of power failure)

ii. Fuel gas-Natural Gas jump over line (used in case of low Natural Gas pressure)

6.6 Utility Requirement: Electricity – For Knock out drum pumps

MP and LP steam – For tracing and smokeless flame

Fuel Gas – For fuel gas purge and pilot burners

Plant Water – Water seal

Nitrogen – Pumping trap

Instrument air – Burner ignition and instruments actuation

6.7 Emergency Conditions: i. Power failure

ii. Fuel gas failure

iii. Instrument air failure

iv. Plant water failure

v. Steam failure

vi. Vacuum condition

vii. Burn back condition

31

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


7. Fuel Oil and Fuel Gas System (Unit 9200 The primary purpose of this system is to provide continuous supply of fuel oil and fuel gas at

the pressure and temperature required for good atomization and combustion in fired heaters and

furnaces.

This unit consists of two systems:

1. Fuel Oil System

2. Fuel Gas System

7.1 Fuel Oil System:

This system gathers and distributes its own produced fuel oil for fulfilling the demand of

process heaters and utility boilers in the refinery.

7.1.1 Refinery Fuel Oil Producers:

i. Vacuum Distillation Unit bottom

ii. Visbreaker Unit residue

iii. Diesel Max Product Fractionator Bottom

iv. Fuel Oil Product from Fuel Oil Product Tankage

v. Flushing Oil from Tankage

7.1.2 Refinery Fuel Oil Consumers:

i. Crude Distillation Unit (Unit100)

ii. Vacuum Distillation Unit (Unit 110)

iii. Visbreaker Unit (Unit130)

iv. Diesel Max Unit (Unit284)

v. Hydrotreating Process Unit (Normally no flow) (Unit200)

Utility boilers (Unit940)

7.1.3 Header Condition: Temperature=175 C

Pressure=12 kg/cm2G

7.1.4 Major Equipments: Table 7

Equipment tag Equipment Name Specifications

920-TK1A/B Fuel Oil Product Storage Tanks Capacity: 1600 m3

Max. Op. Temp: 1800C

Design S.G: 0.98

Cone shaped roof

32

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


Thermally insulated

MP Steam traced

Motor driven agitator

installed

920-P1A/B/C Fuel Oil Circulation Pumps Single stage Centrifugal

Two turbine driven(MP

Steam)

One motor driven

Capacity: 32 m3/hr. each

Discharge Pressure: 14

kg/cm2G

920-E2 Heat Exchanger Shell & Tube type

Shell side: Fuel Oil

Tube side: HS

To maintain RFO header

temperature

920-ME1A/B Fuel Oil Strainer Bucket type

To filter out suspended solid

particle

7.1.5 Process Description:

Fuel Oil tanks (920-TK1A/B) receive fuel oil from above mentioned sources

The RFO header pressure is maintained by three circulation pumps 920-P1A/B/C which takes

their suction from 920-TK1A/B and discharge into the header. Two turbine driven pumps are

in service and one motor driven pump is on standby.

To maintain the viscosity of fuel oil, it passes through a shell & tube heat exchanger 920-E2.

HP steam is used as heating fluid which leaves as HC. This heat exchanger works

intermittently depending on the header temperature.

An RFO filter is installed on the downstream of the heat exchanger to remove any

suspended solids from the stream.

A return line is installed between FOS and FOR header to maintain FOS header pressure. In

case FOS header pressure exceeds the set value, FO will be routed back to tanks via FOR

header.

The FO circulation is three times the refinery demand to maintain header temperature. The

unused fuel oil is routed back to tanks via FOR header.

7.1.6 Utilities:

i. Steam – MP and HP steam

ii. Electricity

iii. Instrument air

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


7.1.7 Emergencies:

i. Power Failure

ii. Steam Failure

iii. Instrument air Failure

iv. Cooling water

7.2 Fuel Gas System: The fuel gas system is designed to collect process unit off gas, natural gas, and vaporized LPG, and to

distribute them to meet the needs of fired equipment and miscellaneous users.

7.2.1 Fuel Gas Sources:

i. Purge gas from DHDS

ii. Purge gas from Diesel Max Catalytic Section

iii. Treated gas from Amine Treating Process Unit

iv. Natural gas

v. Vaporized LPG (On Spec LPG from LPG Spheres and off spec LPG from Start-up of Gas Con.

Unit, LPG Merox Unit, CCR Platforming Unit)

7.2.2 Priorities of RFG Header Sources:

i. Refinery off Gases

ii. Natural Gas

iii. On Spec. LPG

7.2.3 Fuel Gas Consumers:

Process Heaters of following Area:

a) Crude Distillation Unit (Unit100)

b) Vacuum Distillation Unit (Unit110)

c) Visbreaker Unit (Unit130)

d) Diesel Max Unit (Unit284)

e) Naphtha Hydrotreating Process Unit (Unit200)

f) Sulphur Recovery Unit (Unit820)

g) Utility boilers (Unit940)

h) DHDS (Unit 1010)

i) Flare System (Unit915)

7.2.4 Major Equipments: Table 8

Equipment Tag Equipment Name Specifications

920-V1 Fuel Gas Knockout Drum Pressure: 5.7 kg/cm2G Temperature: 600C

920-E3 LPG vaporizer Vertical Bayonet type heat exchange

34

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


7.2.5 Process Description:

The refinery off gases from D-Max and Amine treating unit are routed to RFG header via

920-V1 Fuel Gas Knockout Drum. 920-V1 knocks out any entrained hydrocarbon liquid and

mist from gas stream. The collected liquid is sent to oily water sewer.

The gases leaving from 920-V1 are RFG and sent to various users.

In case RFG are unable to maintain desired pressure, there is a provision of natural gas

supply to maintain header pressure. As a second backup LPG (on and off spec) produced

within the refinery is also available, this LPG is vaporized and made a part of RFG.

LPG vaporizer 920-E3 is a vertical bayonet type heat exchanger, LS is given as a heating fluid

on tube side which vaporizes LPG and comes out as LC.

The RFG header pressure is controlled by a controller 920PIC016 which works on split range

control mechanism.

7.2.6 RFG Header Pressure Control:

The fuel gas header pressure is controlled in two ways. During normal operations, a fuel

availability control system on the boilers varies the ratio of gas/oil firing to maintain a constant fuel

gas system header pressure, if this system can no longer maintain fuel gas system pressure,

additional actions will commence. On high fuel gas pressure, excess fuel gas will be dumped to the

flare. On low gas pressure, additional fuel gas will be obtained from the natural gas.

7.2.7 Utilities:

i. Steam – LP steam

ii. Instrument air – Instruments actuation

7.2.8 Emergencies:

i. Power Failure

ii. Steam failure

iii. External fire

35

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


8. Raw, Plant, Potable water system (Unit 925) This system is designed to meet the requirements of raw, plant, fire, potable and cooling

waters to onsite, offsite, utilities and misc. users in refinery.

8.1 Well Pumps System This system is designed to supply raw (underground) water from shallow water wells to raw

water tanks, which act as main water reservoir for refinery. These pumps also feed fire water tank.

This system consists of six well pumps (925-P1~P6). These are submersible pumps, which are

submersed in underground water wells. Each pump has a capacity of 100 m3/hr. and four out of six

pumps are sufficient to meet normal demand of refinery. These pumps feed raw water and fire

water storage tanks.

Operational Control of Well Pumps:

8.1.1 Normal Operation

Out of six pumps, three are in continuous service, supply water to raw water storage tanks.

Out of remaining three, one pump is selected as ‘primary’, one as ‘secondary’, and last one is kept

spare.

Primary and secondary pumps automatically start at low-level and low-low-level alarms,

respectively, of raw water tanks, while both pumps stop at high-level alarm in these tanks.

The spare pump can be manually taken in service if any of the pumps stop due to low-level in water

well, in which they are submersed.

8.1.2 Six Pump Operation

All pumps can simultaneously be taken in service as per need, e.g. to shorten the filling time

of raw water tanks.

8.2 Raw Water This system consists of following systems:

8.2.1 Raw Water Tanks (925-TK1A/B)

These are cone shaped, fixed roof tanks, each having a capacity of 9500 m3. These tanks are

fed by well pumps by a 12” line.

The lower 50% level of these tanks is dedicated as a backup supply for firewater. This adds to 4

hours of firefighting capability for two major fires in refinery.

There are two outlets from 925-TK1A/B. One 16” line goes to suction side of raw water supply

pumps and other (30” line) to fire water pumps.

36

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


8.2.2 Raw Water Supply Pumps (925-P7A/B/C)

These are motor driven, single stage, centrifugal pumps, which take suction from raw water

tanks and supply water to plant as plant water. It is to be noted that there is no difference in

chemistry of ‘raw’ and ‘plant’ waters. Raw water is called plant water when it passes through a back-

flow preventer, installed downstream of raw water supply pumps.

Out of three raw water supply pumps, one always remains in service, while one pump is on auto

standby mode which starts in case of high flow or low pressure condition in plant water supply

header. The third pump is on standby of second pump, which automatically starts in case first

standby pump does not cut-in automatically.

8.3 Plant Water: Plant water is supplied to following users:

(i) DMW system feed as Boiler makeup water

(ii) Cooling Water System as cooling tower makeup water

(iii) Utility hose station

(iv) Potable water makeup

(v) Sulfur Solidification Unit as for cooling purposes

(vi) Miscellaneous users

8.4 Potable Water System It is the water safe enough to be consumed by humans or used with low risk of immediate or

long term harm.

This system consists of following main components:

8.4.1 Potable water filter system (925-ME1)

This system consists of two vertical vessels which contain carbon filters for removal of

suspended solids and other particles from plant water. One vessel is in service while other remains

on standby.

After each filtration cycle, the filter already in service goes on regeneration and other vessel comes

in service. Potable water is used for backwashing of these filters, which after backwashing the filters,

is collected in waste water collection sump (925-ME50) from where it is pumped to ETP by pump

925-P50A.

These filters can filter 10,300 kg of plant water in one cycle.

8.4.2 Potable Water Storage Tank (925-TK2)

This is a cone shaped, fixed roof tank which receives potable water from 925-ME1. It can

hold 3500 m3 of potable water.

37

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


A flow control valve, FV-027, is installed between 925-ME1 and 925-TK2, for maintaining the level in

the tank.

8.4.3 Potable Water Supply Pumps (925-P9A/B)

These pumps maintain potable water header pressure. These are motor driven, single stage

centrifugal pumps. One of the pumps is in constant service, while other is on standby. A minimum

flow line for pump returns the excess flow back to 925-TK2.

8.5 Cooling Water (C.W.) System: This system is designed to meet the requirements of C.W. for process units, off-site, utilities. It

consists of following main equipment:

8.5.1 Cooling Tower (925-T1)

This is an induced draft, cross flow, concrete built cooling tower. It consists of four cells, with

separate basin compartments for each cell, in addition to a main cooling tower basin.

The cooling requirement for plant can be met by three out of four cells in operation, keeping one cell

spare. Cooling tower has following specifications:

- No. of cells 4

- Type of flow Cross-flow, induced draft

- Total cooling capacity 10,000 m3/hr. for three cell operation + 3,333 m3/hr. for

spare

- Drift loss 0.01% of circulating flow

- Evaporation loss 1.8% of circulating flow

- Design wind load 100 mile/hr.

- Range ~ 10.5oC (45oC to 34.5oC)

- Approach ~ 5oC

There are two main lines, which are

(i) Cooling water supply (CWS) – supplies C.W. to users

(ii) Cooling water return (CWR) – takes warm water back to cooling tower

The cooling tower is equipped with splash bars, which are meant to enhance the contact between

downward flowing water and upward moving air. After getting cooled, the water is collected in a

basin from where C.W. circulating pumps take their suction and supply to plant.

8.5.2 Principle of Operation:

Cooling tower works on the principle of evaporation. Evaporation causes cooling. When hot

water comes in contact with relatively dry air, evaporation takes place, water cools down and the

rising air becomes humid. This humid air leaves the tower from the top, and fresh air is introduced

from the bottom. Hence, the less humid the air, the more will be the cooling.

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


Another factor that takes place is direct heat transfer between hot water and rising air. More the

temperature difference between water and air, higher will be the rate of heat transfer.

Combining the above two points, we see that cooling tower will perform better in winter than

summer because the air is much dry and cold in winters.

8.5.3 Configuration of cooling system in PARCO

Three cells out of four are sufficient to meet the cooling requirements of all users, in peak

summer season. Hence, a hot by-pass is provided that by by-passes a portion of CWR from cooling

tower and directly injects it in suction bay of C.W. circulation pumps. Moreover, one or more cells

may be isolated as per need.

8.5.4 Cooling Water Circulation Pumps (925-P10A/B/C)

These pumps are meant to supply C.W. to users. Two of these are steam turbine driven

while one is motor driven. These have following specifications:

- Made EBARA Corp.

- Type Double suction, centrifugal

- Capacity 6870 m3/hr./pump

- Differential pressure 4.5 kg/cm2

- Discharge head 45 m

- Speed 583 rpm

In normal operation, one turbine driven pump is on hot-rolling standby, while other two are in

service. Hot rolling is to avoid bowing in shaft.

8.5.5 Side stream filters (925-ME2A/B/C)

These are water filters, containing beds of sand and gravel, which remove suspended solids

and turbidity from a portion of circulating cooling water. These filters have a capacity to filter 401

m3/hr. of water. A line from CWS is passed through these filters, and the filtered water is sent to

CWR line.

These filters are designed to automatically regenerate themselves when the filter bed gets choked.

8.5.6 Chemical Injection

Various chemicals are added in cooling water to keep its quality suitable for use. For this

purpose, following proprietary chemicals are used:

(i) High stress polymer – NALCO 3DT104

(ii) Corrosion Inhibitor – NALCO 3DT129

(iii) Bromine based biocide – NALCO 3434

(iv) Deposit control agent – NALCO 8506

(v) Non-oxidizing Biocide – NALCO 7330

(vi) 98 wt.% sulfuric acid

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


8.6 Controls and Emergencies for Cooling Water System

8.6.1 control System:

i. Hot by-pass of cooling tower

ii. Isolating a cell

iii. Covering a cell to avoid evaporation

iv. Start/stop an induced draft fan of a cell

8.6.2 Emergencies:

I. Raw water failure

It is defined as tripping of raw water supply pumps (925-P7A/B/C) due to any reason. In case

failure occurs, cooling tower blow down will be stopped, and DMW system, side stream and

potable water filters will be isolated. Move over, gravity flow from 925-TK-1A/B will be

continued, and if need persists, the shift engr. (Uty) will contact SER/HSE for supply of water

from fire water tanks.

II. Power failure

All process units will trip but C.W. circulation will be continued. Two ID fans, C and D, are on

emergency power back-up. Area operator (Uty) will ensure that steam turbine driven C.W.

circulating pump cuts-in automatically.

III. Steam failure

Motor driven pump will automatically cut-in.

Headers’ Conditions of Water System:

Temp (oC) Pressure (kg/cm2 G)

Plant water amb. > 3.9

Potable water amb. > 3.8

CWS 34.5 > 3.8

CWR < 45 > 1.8

8.7 Effluents of U-925 - Cooling tower blow down

- Side stream filter backwash water

- Potable water filter backwash water

40

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


8.8 Utilities required at U-925 - Electric Power

- HP steam for C.W. circulation pumps

- MP steam as motive fluid in ejectors

- Cold condensate as cooling medium in condensers

- Cooling water as cooling medium in condensers

- Plant water for backwashing of side-stream filters and cooling tower make-up

water

41

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


9. Fire Water System (Unit 926) This system is designed to meet firefighting requirements for the case of two simultaneous

major fires and can supply water at the rate of 2271m3/hr. for thirteen hours.

This system consists of following major equipment:

9.1 Fire Water Tank 926-TK1: - Cone shaped fixed roof type

- Nominal Capacity: 16760m3

- Height: 14630mm

- Max. Liquid Level: 13890mm

- Suction: it takes feed from raw water pumps 925-P1 to P6

This tank act as a main reservoir for firefighting water.

9.2 Fire Water Distribution System: There are six fire water distribution pumps 926-P1A/B/C/D are main pumps while 926-P2A/B

are jockey pumps. A backup firefighting line is also available from 925-Tk1 A/B which can supply

4522 m3 water from raw water tanks. A rupture disc is installed on this backup line which rupture

high differential pressure across it (due to low water level in fire water tank).

9.3 Fire Water Main Pumps 926-P1A/B/C/D: There are four main fire water pumps two of which are motor driven while two are diesel

engine driven. These pumps are double suction single stage centrifugal type. each capable of

generating discharge head of 108m these pumps are capable of operating at 150% of their rated

capacity with discharge head not less than 65m.

Performance test of main fire water pumps is carried out once a year by operating them at under

and over capacity (50-150%) for three hours each pump.

9.4 Jockey Pumps 926-P2A/B: These two pumps are meant to maintain the fire water circuit pressure at 10.5 kg/cm2G

These are Single stage single suction motor driven centrifugal pumps.

One of them is in operation, maintaining system pressure and dumping the excess flow to 926-TK1.

Their PSV has a set point of 12.3 kg/cm2G.

9.5 Fire Water Main distributing System:- Fire water piping loops lay underground in the process and utility, truck loading and building

area and above ground in tankage areas Fire water main distributing piping is provided with hydrant.

Hydrants are distributed at an 85 m.

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


9.6 Fixed open head water spray system: It is provided to the following utilities

High pressure compressors in process area.

LPG spheres.

Off-site pump station.

Light Naptha Tank.

9.7 Semi Fixed Foam Extinguishing System: Semi fixed foam systems include foam chambers installed on appropriate outdoor oil

storage tanks. Foam solution is supplied to each system with the aid of foam fire truck. The fire truck

suction for fire hydrants and deliver foam solution to the foam system

9.8 Semi Fixed Foam Extinguish System for Outdoor Oil Storage Tanks:

The following semi fixed is provided. Top pouring foam extinguishing system for open top floating roof tanks.

Top pouring foam extinguishing system for fixed roof tanks and covered floating roof tanks.

9.9 Hose Houses: Hose houses are distributed throughout the refinery so as to provide potable equipment e.g.

nozzles, fire hoses etc. for first aid fire extinguishment.

9.10 Potable & Wheeled Fire Extinguishers: Potable fire extinguishers are distributed throughout the refinery to cope with small sires.

Wheeled fire extinguishers are also installed at appropriate points in the refinery.

9.11 FM-200 system for buildings: FM-200 fire suppression system is provided in CR1and electrical substation for electric fire.

9.11.1 Fire & Gas Detection System with Fire Alarm:

Automatic fire detection & alarm system consisting of smoke and heat detectors, provided

in buildings to provide a fire alarm system. The fire alarm system for each building will be monitored

at CR1.

9.11.2 Outdoor Manual Alarm Call Points: These are installed throughout the refinery to provide fire alarm signal at CR1 & fire station.

9.11.3 Gas Detectors: Hydrocarbon gas detectors & H2S gas detectors are provided at location where H2S leaks. H2S

gas leaks in process area. Chloride gas detector is provided for chlorination building.

43

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


10. Effluent Treatment Plant (Unit 930) ETP – Effluent Treatment Plant –is designed to collect effluent waste water from all units in

refinery and subsequently treat it to bring it within the stipulated effluent limits given by NEQS and

to dispose it off.

Effluent treatment plant consists of 4 major treatment systems.

Oily Waste Water Treatment System.

Oily Sludge Handling System.

Bio Sludge Handling System

Sanitary Waste Water Treatment System

10.1 Major equipment: Gravity type API oil/water separator

Equalization Tank

Flash mixing basin

Flocculation and DAF module

Biological aeration basin

Clarifiers

Sand filters

Final lift station

Chemical dosing injection skids

The design capacity of U-930 is 340 m3 /hr.

10.2 Oily Waste Water Treatment System: It receives all the oily waste water streams from refinery drum. Recovered products are oil &

sludge. All the waste materials or effluents of the refinery are collected in 930-ME2 located near

knock out drum (915-V1). The bar screen (930-ME81) and the belt type skimmer (930-ME81) are

provided in the inlet section of 930-ME2 and continuously or intermittently operating for removal of

large floating/suspended solid materials and oil in the effluent water, then the effluent water flow to

the second section of 930-ME2 through under weir.

Process waste water lift pumps (930-P1 A/B) are installed in the second section. The effluent water is

transferred to API oil/water separator (930-ME3 A/B) in the WTP (Water Treatment Plant) area. In a

rainy or fire situation, the quantity of effluent water will exceed the capacity of 930-P1 A/B. The

excess effluent is led to the 3rdsection of 930-ME2 through an over flow weir. Three process high

flow lift pumps (930-P2 A/B/C) are provided in the 3rdsection to transfer the oily water to diversion

tank (930-TK1).

44

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


10.2.1 API oil/water separator section:

API is a simple gravity separator based on the design standards of API for the separation of

oil & solids from waste water. API separator is based on the removal of all free oil globules larger

than 0.05 cm. It consist of a rectangular channel in which the waste water flows horizontally while

free oil rises to the surface and settle able suspended solids settle in the bottom. Oil collecting on

the surface is skimmed off to an oil recovery circuit while the settled solids are scrapped off to oily

sludge circuit.

10.2.1.1 Process of API oil/water separation:

All the oily waste water streams from the refinery are pumped to API oil/water separator is

separator have a design capacity of 170m3/hr. The inlet weir is at a high elevation to the

outlet weir to provide different working levels to the inlet separation section.

The API (American Petroleum Institute) is designed to split the inlet flow between 2 bays.

Reaction jet baffle send the effluent into separating channels and distribute the oil & water

mixture over the cross sectional area of flow.

Each of the API oil/water separator is fitted with a chain driver scraper which rakes the oily

sludge to a sludge storing pump on the basin floor. Oily sludge collected in both API

oil/water separator sump into API sludge sump (930-ME21).

Water collected from oily sludge treatment process and discharged from oily sludge thickener

also enter API oil/water separator.

A slotted pipe type skimmer is installed just before the outlet section of each API oil/water

separator.

Each rotary skimmer collects floating oil from its bay and under gravity drains the skimmed

oil to API skimmed oil sump (930-ME20). Recovered oil from API skimmed oil sump is

pumped by one of 2 API skimmed oil pump (930-P13 A/B) to tank (930-TK6 A/B).

Effluent water from API oil/water separator is collected in the outlet section of the separator

basin and pumped to equalization tank (930-TK2) by 930-P12 A/B/C pump. Pumps have a

design capacity of 170 m3/hr.

10.2.2 API Scraper Mechanism:

The API scraper are chain driven devices which uses planks and continuously rotating along

the top of the water in one direction and then back along the bottom of the tank in the other

direction. The mechanism scrapes oil off the top of water surface and scrape sludge along the

bottom of tank into sludge sump.

API Roll Oil Skimmer:

The API roll oil skimmer installed in the separation section of each basin rotate and collect oil

off the water surface and discharge it out of the API oil/water separator basin (930-ME3 A/B) and

into API skimmed oil sump (930-ME20).

45

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


API sludge pumps (930-P14 A/B):

API sludge pumps 930-P14 A/B are air driven diaphragm type pump which pumps the sludge

collected in the API sludge sump (930-ME21) to the oily sludge tank (930-V9).

API skimmed oil pumps:

API skimmed oil pumps (930-P3 A/B) are air operated diaphragm valve which

transfer oil from API skimmed oil (930-ME20) to 930-TK6 A/B.

API Effluent Pumps (930-P12 A/B/C):

API effluent pumps (930-P12 A/B/C) are submersible pumps which pump effluent

from API to equalization tank (930-TK2).

10.2.3 Equalization Tank:

It has a nominal capacity of 4100 m3 and receives API effluent as well as sand filter wash

water, centrifuge filtrate and neutralized spent caustic. Tank is mixed with an air with the help of

equalized tank compressor (930-C1) which has a capacity of 400 Nm3/h. Equalization tank is named

so because it equalize all the parameter like pH, dissolved solids etc. Air also helpful in equalizing the

BOD values of different parameters and help in maintaining it by giving its own oxygen there.

10.2.4 Dissolved Air Floatation DAF:

DAF feed pumps (930-P15 A/B/C) are used for pumping effluent from equalization tank (930-

TK2) to the DAF flash mixing basin. Each pump is rated at 192 m3/hr capacity and delivers

effluent water which has been mixed in the flash mixing basin (930-ME22).

The flash mixing basin (930-ME22) has 3 compartments aligned so the effluent flows from

one to another. The first 2 compartments each contain a mixer with vertical shaft and

3rdcompartment act as stilling chambers.

First two compartments are separated by a baffle. The effluent flow into 1stcompartment

where acid or caustic dozed to give required pH 6-9. Polymer is dozed into 3rdcompartment

to seed and promote the formation of the flock. The effluent flows into DAF flocculation

basins.

The dozed effluent overflows from the flash mixed basin into both of DAF inlet flocculation

chambers (930-ME 4A/B). Each of the chambers is fitted with a vertical paddle DAF

flocculator. The clarified effluent flows under a baffle and over DAF outlet weir to DAF

effluent recycle sump (930-ME23).

A portion of water is drawn off from recycle DAF sump by DAF effluent recycle pumps (930-

P16 A/B/C).

Each DAF basin is fitted with a surface skimmer to remove floating sludge and also a bottom

scraper conveyor for periodical removal of settled sludge.

The surface skimmer in each DAF basin moves the floating sludge and also a bottom scraper

conveyor for periodical removal of settled sludge.

The surface skimmer in each DAF basin move the floating material into the sludge trough, a

trough common to both basin which conduct the sludge to DAF scum sump.

46

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


Each DAF basin scraper mechanism moves the sludge that has settled in the bottom of basin

to the sludge outlet section DAF sludge sump (930-ME24). Air driven pumps (930-P20 A/B)

deliver the sludge to (930-V9).

The oily scum floating on the surface of DAF basin flows over a baffle and then through

common collection channel into DAF scum sump (930-ME25). From here it is pumped to

oily sludge settling tank (930-V9).

DAF feed pumps (930-P15 A/B/C):

It pump the waste water from the equalization tank to flash mixing basin (930-ME22) in

which chemicals are mixed thoroughly.

DAF Flocculator:

It assists the formation of flock in the waste water before the waste water enter DAF

basin. Flocculators are slow speed stirrers.

DAF Skimmer:

It scraps the floating scum blankets from the water surface into DAF basins (930-ME4

C/D) sludge trough.

DAF Scrappers:

It scraps the sludge off the bottom of DAF basins & into sludge well. From where it is

discharged to DAF sludge sump.

DAF Basins (930-ME4 A/B):

It removes the flocculated suspended solid and floating oils by dissolved air

floatation principle. A portion of treated water resulting from DAF process is pumped into

the DAF recycle water pressure vessel (930-V11 A/B). 930-V11 A/B is equipped with air

blower and it saturated with air and then injected into DAF basin (930-ME4 C/D). On

injection into each of DAF the dissolved air is released as millions of fine air bubble. These

air bubbles take the sludge to surface and the surface adhering sludge is skimmed by DAF

skimmer mechanism and discharged to sludge trough.

DAF effluent recycles pumps:

DAF effluent recycle pumps (930-P16 A/B/C) recycle water from DAF outlet into DAF

recycle water pressure vessel (930-V11 A/B).

DAF sludge pumps (930-P20 A/B):

930-P20 A/B are air driven diaphragm type pumps which pump sludge from DAF sludge

sump (930-ME 24) to oily sludge settling tank (930-V9).

47

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


DAF Scum Pumps (930-P43 A/B):

930-P43 A/B pump sludge from DAF scum pump (930-ME25) to oily sludge settling tank

(930-V9).

10.2.5 Biological Aeration & Clarification:

The effluent from DAF basins (930-ME4 A/B) gravitates via common channel to 2 biological

aeration basins (930-ME5 A/B) where the biological oxygen demand (BOD5) of effluent is

reduced. Four biological aeration basin blowers (930-C2 A/B/C/D) are installed each with a

capacity of 1950 Nm3/hr.

Ammonium phosphate is dozed into inlet of Biological Aeration basin to supply the nutrients

necessary for the activation of biological process. Ammonium phosphate solution day tank

(930-V39) pumped with (930-P39 A/B) into biological aeration basin.

After aeration the next treatment process is clarification. Two circular suction header type

clarifiers (930-ME27 A/B) separated the biological solids formed in the biological aeration

basins. Once clarification has been achieved, the clarified effluent overflows each clarifier

vnotch weir into a common outlet channel.

Each clarifier has a sludge scraper mechanism which draws the sludge off the bottom of

clarifier. A skimmer arm skims any scum floating on the surface of clarifier into clarifier

skimming tank (930-V5) which is common to the outlet of both clarifiers.

Some of the clarified bottom sludge is recycled back by the clarifier sludge recycle pumps

(930-P21 A/B/C) to the biological aeration basin to maintain concentration of mixed liquor

suspended solids (MLSS) in the biological aeration basins.

Part of the recycle excess sludge from the clarifier sludge recycle pumps (930-P21 A/B/C) is

wasted to aerobic digester (930-TK60).

The floating scum is transferred to aerobic digester (930-TK60) by clarifier skimming pump

(930-P11).

COD:

It is the chemical oxygen demand which is showing that if greater impurities present in

water they will take the dissolved oxygen and fishes will die due to deficient of oxygen level. So that

is why is desired to COD value lowest.

Biological Aeration Basin Air Blowers:

The biological aeration basin air blower (930-C2 A/B/C/D) provides oxygen to the biomass in

the biological basins (930-ME 5 A/B).

Clarifier Scraper & Skimmer:

The clarifier scraper & skimmer of each clarifier are both driven by a common driver. The

function of the skimmer is to scrape floating scum from the surface of the clarifier and discharge into

clarifier’s skimming tank (930-V5). The scrapper & skimmer both rotate together at a slow speed of 3

rev per hour.

48

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


Clarifier Sludge Recycle Pumps:

The clarifier sludge recycle pumps (930-P21 A/B/C)pump sludge drawn from the bottom of

clarifier (930-ME27 A/B) back into the outlet to biological aeration basins (930-ME5 A/B) so that

bacteria move back to aerobic basins.

Clarifier Skimming Pump:

The clarifier skimming pump (930-P11) is an air driven diaphragm pump which pumps the

surface scum removed from the clarified water to aerobic digester (930-TK60).

10.2.6 Filtering Process Description:

The clarified water from clarifiers (930-ME27 A/B) flows to 4 rapid gravity type sand filters

(930-ME6 A/B/C/D).

The sand filter media comprises a top layer of anthracite, a middle layer of sand and a

bottom layer of graduated support gravel.

2 back wash pumps (930-P32 A/B) are installed in the back wash sump (930-ME31) and have

sufficient capacity to backwash one sand filter at a time. Back wash is done in order to

remove oil and grease collected in sand filter.

Back wash water is collected in the washed water sump (930-ME 30) and transferred to

equalization tank by the washed water transfer pumps (930-P33 A/B).

The treated water from sand filter (930-ME6 A/B/C/D) gravitates to the backwash sump

which when filled overflows into treated water sump (930-ME32). The treated water transfer

pumps (930-P27 A/B/C) transfer the treated water from 930-ME 32 to the final lift station

sump (930-ME 7).

Filter Backwashing:

Filter back washing is carried out to wash the waste solids collected in the filter media and

return the filter to a clean state so that it is ready for further service.

Sand Filters Backwash Air Blowers:

The air blower (930-C3) is designed to provide air to the backwash sequence for four

filters. The air agitates and loosens the trapped particles from the media which then assist in

their removal during the washing process.

Backwash pumps (930-P32 A/B):

These pumps are designed to provide clean water from back wash sump (930-ME 31)

for the backwash phase of filter backwash sequence.

Washed Water Transfer Pumps (930-P33 A/B):

These pumps pump the backwash water from washed water sump (930-ME30) to

the equalization tank.

49

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


Treated Water Transfer Pumps (930-P27 A/B/C):

These pumps transfer the treated water from 930-ME 32 to the final lift station

(930ME7).

Treated Water Recirculation Pumps (930-P43 A/B):-

These are submersible centrifugal type pumps which pump treated water to

equalization tank compressor after cooler (930-E10).

10.3 Oily Sludge Treatment System: Oily sludge from the API separator, DAF units and other received in oily sludge handling tank

(930-V9) which has a nominal capacity of 30 m3

. Oily Sludge from (930-V9) is transfer to (930-ME 11) by oily sludge feed pumps (930-P55

A/B).

The oily sludge thickener (930-ME 11) is a circular designed tank with an inverted conical

shaped bottom and is fitted with a rake which continuously and is fitted with a rake which

continuously slowly rotate so as to aid the sludge thickening process.

The air driven oily sludge transfer pumps (930-P56 A/B) transfer the thickened oily sludge

from the sludge thickener to oily sludge treatment process which dewaters the sludge.

The filtrate created from oily sludge centrifuge flows to a drainage sump and centrifuge

filtrate tank and is then pumped to equalization tank (930-TK2) by the centrifuge filtrate

transfer pump (930-P70).

The centrifuge discharges dried sludge cake directly into oily sludge cake conveyor (930-

ME85) which transfer the sludge cake to an open top container. Polymer Is injected into

thickened oily sludge to aid in dewatering process.

Oily Sludge Feed Pumps (930-P55 A/B):

These pumps transfer sludge from 930-V9 to oily sludge thickener 930-ME 11.Oily

Sludge Thickener (930-ME11):

It is designed to increase the amount of solids concentration in the sludge as the

sludge is being fed to oily sludge centrifuge decanter (930-ME 81). The scraper driver rotate

the rake making a slow stirring action and assisting the solids in settling to the bottom of the

tank.

Oily Sludge Transfer Pumps (930-P56 A/B):

These pumps transfer the thickened sludge from oily sludge thickener (930-ME 11) to

the oily sludge centrifuge decanter (930-ME 51).

Oily Sludge Centrifuge Decanters (930-ME51):-

It helps in dewatering the oily water sludge to produce a dried sludge cake.

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


Oily Sludge Cake Conveyor (930-ME85):

It helps in transferring the sludge cake from oily sludge decanter (930-ME51) to open

top container for removal from site.

Centrifuge Filtrate Transfer Pump (930-P70):

These pumps are used for pumping filtrate which are drained in bio sludge wash

water tank, from centrifuge back to equalize tank (930-TK2).

10.4 Biological Sludge Handling System: Biological sludge which is wasted periodically from biological aeration and clarifier treatment

process & sludge from sanitary waste treatment plant is sent to aerobic digester for further

thickening as the digester is fitted with an aeration distributing system through which an air blower

discharges air so as to adequate oxygen for aerobic digestion process to take place.Sludge from

aerobic digester is pumped to bio sludge thickener for further sludge thickening. The bio sludge

thickener is fitted with a continuously rotating rake to accelerate the thickening process.Thickened

sludge discharges from bio sludge thickener are pumped to bio sludge belt press. Prior to entering

the belt press the sludge is dozed with polymer to promote water thickening.

Functions:

Aerobic Digester Air Blower:

The aerobic digester air blower (930-C4) supplied air & oxygen to accelerate

biological digestion of sludge in the aerobic digester (930-TK60).

Biosludge Feed Pumps (930-P60 A/B):

These pumps transfer the sludge from aerobic digester (930-TK60) to bio sludge

thickener (930-ME60).

Bio Sludge Thickener (930-ME60):

It is designed to increase solids concentration in the sludge before it is fed to bio

sludge belt press (930-ME61). The rake slowly stirs the effluent, the action accelerating the

solids to settle into bottom of tank. The clear water overflows from top surface and

gravitates to washed water sump (930-ME30).

Bio Sludge Transfer Pumps (930-P61 A/B):

These pumps are air driven pump which pump biosludge to biosludge belt press

(930-ME61).

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


Bio Sludge Belt Press (930-ME61):

It is designed to dewater the biosludge to produce dried sludge cake.

Bio Sludge Cake Conveyor (930-ME 86):

It is designed to transfer the sludge cake discharged from belt press into an open top

container for final disposal.

Belt Press Filtrate Transfer Pump (930-P63):

These pumps transfer the filtrate which is collected in belt press filtrate sump (930-

TK62) to bio sludge thickener (930-ME60).

Belt Press Washed Water Pump (930-P58):

These pumps provide wash water continuously to clean the belts when belt press

running.

10.5 Sanitary Waste Water Treatment System: All sanitary waste water from site officers, building, toilets & kitchen flow through a bar

screen to sanitary waste water treatment plant (930-ME 10 A/B).

Sanitary waste water treatment plant consists of 2 sanitary waste treatment units. The sanitary

waste water flows to the primary screening & settlement tank of each sanitary waste water

treatment plant. It flows upward through parallel plates to aerobic treatment unit. In this

section the flow is mixed with oxygen so as to activate aerobic process. The aerobic treated

unit rotates and promotes a rapid aerobic reaction. Final treatment of sanitary waste occurs

in final settlement tank where, similarly to the primary settlement tank, waste water flows

upward through parallel plates to achieve settlement of solids away from outlet flow.

The separated sludge is stored in the base of the units until the periodically occurring

desludging step transfers the sludge to the biological digester (930-P72 A/B).

The treated water sanitary waste flows from the sanitary waste treatment units into

hypochlorite contact tank (930-TK72) into which hypochlorite disinfectant is dozed.

The disinfected waste water flows out of the hypochlorite contact tank into the sanitary

treated effluent tank (930-TK73). The submersible type treated sanitary transfer pumps

(930-P73 A/B) discharge the effluent from sanitary treated effluent tank to either biological

aeration basins (930-ME 5 A/B) or final lift station (930-ME7).

Injection of hypochlorite is achieved from hypochlorite storage tank (930-TK71) via

hypochlorite storage tank (930-P74 A/B). Hypochlorite is supplied from a tanker and pumps

by a portable pump into hypochlorite storage tank. The amount of hypochlorite injected is

controlled by running injection pumps while sanitary waste pump (930-P50 A/B) is

operating.

52

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


11. Demineralized water and Boiler System: Unit-940 is composed of the following systems.

Boiler make up water treating system

Condensate recovery unit

Deaerator section

Boiler section

Steam let down section

Steam, Feed Water and Condensate Handling System is designed to meet the requirements of their

various users in the refinery under the various operation modes.

11.1 Equipments List: Table 9

Tag Name

940-ME1 Boiler Makeup Water Treating System

940-TK1A/B DMW Tanks

940-P2A/B DMW Water Pumps

940-ME2 Deaerator

100-E21 Diesel Product Exchanger

940-P1A/B/C Boiler feed water pumps

940-B1A/B/C Utility boilers

940-V1 Continuous blow down drum

940-V2 Intermittent blow down drum

020-PV-004B HP-MP letdown system

020-PV-007 MP-LP letdown system

11.2 Boiler Make Up Water Treating System: Demineralized water is obtained in boiler make up water treating system (940-

ME1).Following are the different plant water impurities found in Boiler Make Up Water Treatment

System.

Cations+

- Calcium ( Ca++) as ( Ca CO3)

- Magnesium ( Mg++) as (Mg CO3)

- Sodium (Na+)

- Potassium (K+)

- Ammonium (NH4+)

Anions –

- Bicarbonate (HCO3-) as (CaHCO3)

- Carbonate (CO3--) as (CaCO3)

- Sulfide (SO4--) as (H2SO4)

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


- Chloride (Cl-) as (CaCl)

- Nitrate (NO3-)

- Nitrite (NO2-)

11.2.1 Process Descruption:

Vessel (940-V50) is specified for activated carbon filter purpose which is specified for

adsorption purpose by means of its porous structure. Dissolved chlorine and potassium

permanganate deteriorate the life of cationic and anionic resins so activated carbon adsorbs these as

well as non-ionized inorganic matter.

This unit takes plant water as feed and removes the suspended solids and dissolved salts to make it

suitable for its use as boiler makeup water. The water, after treatment, is termed as De-Mineralized

Water (DMW). This system employs a series of treatment steps, which mainly include filtration and

ion-exchange method.

Plant water first enters the vessel containing activated carbon filter, which is meant to remove

minute suspended particles and any greasy/oily material from plant water. After this, the water

enters the cation-exchange vessel which contains a cation exchange resin. Here, a double

displacement reaction takes place as follows (taking the example of CaCO3):

R-H + CaCO3 R – Ca + H2CO3

The resin contains H+ attached to its surface, which when come in contact with the salts, exchange

its place with it. In this way, the water becomes relatively free of hardness.

Water from cation exchanger is transferred to de-carbonator. H2CO3 decomposes readily into H2O

and CO2, hence in decarbonator; this CO2 is removed with the help of stripping stream of air. This

step reduces the load of carbonate removal on anion exchanger.

H2CO3 H2O + CO2

In anion exchanger, the resin contains OH- attached to its surface. The mineral acids which form in

cationic vessel are removed by this exchanger:

R-OH + HCl R2Cl2 + H2O

R-OH + H2SO4 R2SO4 + H2O

From anionic vessel, water relatively pure of mineral impurities is sent to its final treatment step, in

mixed bed polisher. It contains both cationic and ionic resins, and is meant to remove any impurities

which have slipped from previous steps. After passing through mixed bed polisher, the water is

called De-Mineralized Water (DMW), and is pumped to DMW tanks, 940-TK1A/B.

The capacity of DMW train is 85 m3/hr. per train, with two trains in facility. One usually remains on

standby, while other in service.

The water, after getting treatment from DMW system, should have following specifications:

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


- Conductivity <5μS/cm at 25 oC

- Total hardness (ppm as CaCO3) nil

- Silica (ppm as SiO2) < 0.02

The turndown rate of DMW system is 40 m3/hr.

11.2.1.1Regeneration of Resins:

Cationic resin is regenerated using H2SO4 of lean concentrations, 1.5 and 3 wt. %, while

anionic resin is regenerated using lean NaOH solution.

During the regeneration carried out with H2SO4, the cation fixed on the resin is removed

according to following.

R2Ca + 2 H ------ 2R-H + Ca++

During the regeneration carried out with NaOH, the anion fixed on the resin is

removed as follow.

R2SO4+ 2OH--------2R-OH + SO4

11.3 Condensate Recovery Section:-

The condensate recovery section consists of three steam levels of HP steam, MP

steam and LP steam, and each steam level condensate is recovered as much as possible.

11.3.1 High Pressure Condensate (HP Condensate):

High pressure condensates from the refinery are recovered in HP condensate flash

drum (940-V5) which flashes to MP steam level. Flashed vapor is directed to MP steam

header and flashed liquid is directed to MP condensate flash drum. The HP condensate

drum pressure is equal to MP steam header.

11.3.2 Medium Pressure Condensate:

Condensate from MP steam heat exchangers is directed to MP condensate flash

drum which flashes to LP steam level. Flashed vapor is directed to LP steam header and

flashed liquid is directed LP condensate flash drum. The MP steam condensate drum

pressure is equal to LP steam header.

11.3.3 Low Pressure Condensate:

Condensate from LP steam heat exchangers are directed to LP condensate flash

drum which flashes to 1.5 kg/cm2G, deaerator operation pressure level. Flashed vapor id

directed to deaerator from deaerating steam.

11.3.4 Cold Condensate:

Cold condensate from each surface condenser is pumped & mixed which

demineralized.

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


11.4 Deaerator Section: The deaerator receives all recovered condensate and demineralized water to make up of

losses for steam stripping, blow down and so on. The water is heated up with the saturated steam

flashed from the condensate recovery system. The system consists of a spray tray deaerator in which

water and steam are mixed heated and deaerated. The deaerator is designed to treat a feed water

flow of 250,000 kg/h. The function of a deaerating feed water heater is to remove non condensable

gases and to heat boiler feed water.A deaerating feed water heater consists of a pressure vessel in

which water and steam are intimately mixed under controlled conditions. When this is properly

achieved, water temperature rises, non-condensable dissolved gases are liberated and removed, and

the effluent water may be considered corrosion free from oxygen.A deaerating feed water heater is

the watch-dog of a boiler plant as it protects the feed pumps, piping, boilers and any other piece of

equipment that is in the boiler feed and return cycle from the effects of corrosive gases. It

accomplishes this by reducing the concentration of noncondensable gases: i.e. oxygen and carbon

dioxide. The deaerator feed water is connected to a storage tank located immediately below the

heater.

A deaerating heater utilizes steam by spraying the incoming water into an atmosphere of

steam in the pre-heater section. It then mixes this water with fresh incoming steam in the de-aerator

section.In the first stage, the water is heated with steam and virtually all of the oxygen and free

carbon dioxide left from boiler make up water treatment system removed. This is done by spraying

the water through self-adjusting spray valves which are designed to produce a uniform spray film

and consequently a constant temperature and uniform gas removal is obtained at this point.

11.5 Boiler Section:

11.5.1 Boiler Feed Water Conditions:

BFW conditions are as follows:

- Pressure (kg/cm2 G) 58

- Temperature (oC) 115 ~ 121

- pH 8.5 ~ 9.5

- O2 (ppm) 0.007

- Conductivity (μS/cm) < 5

Steam and Condensate Recovery Condition:

Table 10

Steam/condensate type Temperature

oC Pressure kg/cm2 G

Low pressure steam 190 3.5

Medium pressure steam 205 10.5

High pressure steam 390 42.2

Low pressure condensate 121 1.1

Medium pressure condensate 3.8 Sat.

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


High pressure condensate 10.8 Sat.

Cold condensate 3.1 52.5

11.5.2 Boiler and Steam Headers:

There are three boilers, each having a capacity of generating 65 ton/hr. of saturated steam,

having a temperature and pressure that is characteristic of High Pressure (HP) steam.

Half of the steam requirement of refinery is fulfilled by the steam generated by some process

generators (e.g. platforimg unit and incinerator at SRU) while remaining half is fulfilled by the three

boilers, working in parallel.

The water from BFW pumps is pumped into a preheater (a shell and tube heat exchanger), which

heats up the water initially using saturated HP steam. From here, the water enters the economizer

tubes, which are lying in convection section. The water is further heated by flue gases leaving the

radiation section.

The main parts of boiler are steam drum, mud drum, riser tubes and down comers. Steam drum is a

horizontal vessel which is connected to mud drum by risers and down comer tubes. Riser tubes are

present inside radiation section of boiler furnace. Liquid water, being denser from steam, flows

downwards in the mud drum, and then flows into riser tubes, taking heat from radiation box,

converting into saturated mixture of steam and water, and rising back to steam drum. In this way,

the steam drum contains saturated HP steam in contact with water.

The saturated HP steam is then routed to a primary superheater, de-superheater, and then through

a secondary super heater. This system adds the required degree of super heat, increases quantity of

steam, and acts as an important control for header control conditions.

The flue gases leave the stack at a temperature of about 200 oC, because the sulfur content in gases

has a dew point of 150 oC.

There are condensate collection vessels and let down system installed downstream of the boiler

system. These vessels are meant to route the condensate back to boiler and also to decrease the

pressure and temperature of gases from HP to MP (medium pressure) and LP (low pressure) steams.

11.5.3 Chemical Dosing for Boiler Feed Water:

Eliminox (Oxygen Scavenger):

Eliminox can economically remove small amount of dissolved oxygen. Eliminox is

dosed by 940-P53 A/B (reciprocating pump). Dosing solution is prepared in dosing tank 940

ME-3A by adding 6.0 liter Eliminox and remaining portion filled with demin water.

Cyclohexylamine:

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


It is employed to maintain the condensate pH in the range of 8.0-9.5. It neutralizes

the carbonic acid present in steam condensate and thus overcome low pH values and

corrosion.Amine is dosed by 940-P54 A/B (reciprocating pump) by adjusting its strokes.

Dosing solution is prepared in dosing tank (940-ME-3B), by adding 4litters amine and

remaining portion filled with demin water.

11.5.4 Boiler Parts:

Following are the different parts of the boiler.

Boiler Drum

Forced Draft Fan

Burners

Furnace

Boiler Bank

Down comers & Risers.

Super- Heaters

Economizer

Soot Blowers

Stack

I.B.D ( Intermittent Blow Down)

C.B.D ( Continuous Blow Down)

Chemical Dosing

Boiler Drum:

Each boiler has one upper and one lower drum. Upper drum is called steam drum and lower

drum is called mud drum.The steam drum is supported by the mud drum through the boiler bank

tubes.

Following are the different functions of steam drum.

To receive feed water.

To provide water storage for proper and safe water circulation.

To receive water & steam mixture.

To separate the steam from water through steam separators.

To dry the saturated steam through the dryers.

To send the steam to Super-Heater for super heating purpose.

Steam drum is also fitted with the following drum internal and internal pipes.

Cyclone separators.

Wire mesh (demisters) & Chevrons dryers.

Chemical Dosing pipe

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


Forced Draft Fan 940-C1 A/B/C:

Each boiler is provided with a centrifugal fan. FD Fans which are provided to boiler (940-B1

A/B) are fitted with 2 drivers (Electric Motor & Steam Turbine) and Boiler (940-B1 C) provided with

steam turbine driver. Each FD fan is equipped with rain hood and silencer.Maximum capacity of fan

is 70,000 Nm3/h and its working capacity is 55,000 Nm3/h. At full load discharge pressure is 5 KPa.

Motor and turbine driven shaft are rotated with 1497 RPM.

Boiler Furnace:

The furnace is mainly composed by the following sections.

Front Wall Furnace housing the burners

Upper & Lower front wall header.

Rear Wall forming the rear side of furnace.

Upper and lower rear wall headers.

D-tubes forming the floor, side and roof furnace walls.

Boiler Bank side wall

All the above mentioned tubes are water walls which are covered on the external side by mineral

wool insulation.

Super- Heater & Desuperheater:

The super heater is divided in 2 stages (Primary & Secondary super heater), with an

intermediate spray water desuperheater. Each boiler is equipped with 2 desuperheater. The

desuperheater no.1 placed between primary & secondary super heater stage in order to keep the

final super heater temperature steady within the specified control range.The spray water

desuperheater no.2 controls the steam temperature downstream.

Feeders:

Feeders are those which take the water from mud drum and give feed to the down headers

of the front & rear water walls of the furnace.

Risers:

Risers are those which take the steam/ water mixture from upper headers of the front &

rear water walls of the furnace and open in front of steam separators.

Economizer:

Economizers are mechanical devices which are intended to reduce energy

consumption.These are used to head water but not normally beyond the boiling point of

water.Economizers are named so because they can make use of the enthalpy of hot flue gases and

therefore play an important role in improving the efficiency of boiler. Economizers’ saves energy by

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


using the exhaust gases from the boiler to pre heat the cold water.Boiler Feed Water is supplied to

economizer via BFW pre-heater.

Boiler Stack:

Each boiler is equipped with 26 meters high self-standing type stack and the effluent gases

are removed through it.

Pre-Heater:

Each boiler is equipped with feed water pre-heater placed over the steam drum. The feed

water pre-heater placed over the steam drum. The feed water pre-heater is installed in order to

increase the feed water temperature upstream the economizer inlet. Feed water is heated using

saturated steam taken from the steam drum.

Blow down:

Blow down is water intentionally wasted from a boiler to avoid concentration of impurities

during continuing evaporation of steam. The water is blown out of the boiler with some force by

steam pressure within the boiler. A steam boiler evaporates steam from liquid water, and requires

frequent replenishment of boiler feed water for the continuous production of steam required by

most boiler applications. Water is a capable solvent and will dissolve small amounts of solids from

piping and containers including the boiler. Continuing evaporation of steam concentrates dissolved

impurities until they reach levels potentially damaging to steam production within the boiler.

Without blow down, impurities would reach saturation levels and begin to precipitate within the

boiler. High level of impurities would lead to precipitation which results in the formation of scale

deposits on heat exchange surfaces. Scale deposits thermally insulate heat exchange surfaces

decreasing the rate of steam generation so blow down are very helpful in removing these impurities.

Intermittent Blow Down vessel (940-V2):

Steam generating unit is equipped with one atmospheric intermittent blow down drum

(940-V2) to 3 boilers in order to collect all intermittent drains.

Continuous Blow Down vessel (940-V1):

Steam drum is equipped with continuous blow down drum (940-V1), common to 3 boilers, in

order to collect all continuous drains.

Chemical Dosing System:

The steam generating unit is equipped with one chemical dosing system (940-P60 D), common to 3 boilers that inject phosphate into steam drum of each boiler.

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


11.6 Steam Let Down Section: This section is used to give medium pressure and low pressure steam from high pressure steam in which boiler feed water used to decrease the temperature of HP steam.

61

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


12. Assignments

12.1 Assignment # 01 To describe cooling tower, Types of cooling tower, Components of cooling tower and

factors effecting the performance of Cooling tower.

Cooling tower:

A cooling tower is equipment used to reduce the temperature of a water stream by

extracting heat from water and emitting it to the atmosphere. Cooling towers make use of

evaporation whereby some of the water is evaporated into a moving air stream and subsequently

discharged into the atmosphere

Cooling towers are heat exchangers that are used to dissipate large heat loads to the atmosphere.

They are used as an important component in many industrial and commercial processes needing to

dissipate heat.

Types of cooling towers:

There are two main types of cooling towers:

The natural draft cooling tower

Mechanical draft cooling tower

Types of natural draft towers:

There are two types of natural draft cooling towers:

Cross flow tower : air is drawn across the falling water and the fill is located outside the

tower

Counter flow tower: air is drawn up through the falling water and the fill is therefore located

inside the tower, although design depends on specific site conditions

Types of mechanical draft towers:

There are two types of forced draft cooling towers:

Forced draft cooling tower: air is blown through the tower by a fan located in the air inlet

Induced draft cross flow cooling tower: is blown through the tower by a fan located in the

air outlet

Types of induced draft towers:

There are two types of induced draft cooling tower

Induced draft cross flow cooling tower:

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


Water enters at top and passes over fill

Air enters on one side (single-flow tower) or opposite sides (double-flow tower)

an induced draft fan draws air across fill towards exit at top of tower

Induced draft counter flow cooling tower:

Hot water enters at the top

Air enters bottom and exits at the top

Uses forced and induced draft fans

Components of a cooling tower:

The basic components of a cooling tower include the frame and casing, fill, cold-water basin, drift

eliminators, air inlet, louvers, nozzles and fans. These are described below.

Frame and casing:

Most towers have structural frames that support the exterior enclosures (casings), motors,

fans, and other components. With some smaller designs, such as some glass fiber units, the casing

may essentially be the frame.

Fill:

Most towers employ fills (made of plastic or wood) to facilitate heat transfer by maximizing

water and air contact. There are two types of fill:

Splash fill: water falls over successive layers of horizontal splash bars, continuously breaking into

smaller droplets, while also wetting the fill surface. Plastic splash fills promote better heat transfer

than wood splash fills.

Film fill: consists of thin, closely spaced plastic surfaces over which the water spreads, forming a

thin film in contact with the air. These surfaces may be flat, corrugated, honeycombed, or other

patterns. The film type of fill is the more efficient and provides same heat transfer in a smaller

volume than the splash fill.

Cold-water basin:

The cold-water basin is located at or near the bottom of the tower, and it receives the

cooled water that flows down through the tower and fill.

Drift eliminators:

These capture water droplets entrapped in the air stream that otherwise would be lost to

the atmosphere.

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


Air inlet:

This is the point of entry for the air entering a tower. The inlet may take up an entire side of

a tower (cross-flow design) or be located low on the side or the bottom of the tower (counter-flow

design).

Louvers:

Generally, cross-flow towers have inlet louvers. The purpose of louvers is to equalize air

flow into the fill and retain the water within the tower. Many counter flow tower designs do not

require louvers.

Nozzles:

These spray water to wet the fill. Uniform water distribution at the top of the fill is essential

to achieve proper wetting of the entire fill surface. Nozzles can either be fixed and spray in a round

or square patterns, or they can be part of a rotating assembly as found in some circular cross-section

towers.

Fans:

Both axial (propeller type) and centrifugal fans are used in towers. Generally, propeller fans

are used in induced draft towers and both propeller and centrifugal fans are found in forced draft

towers.

Factor effecting Cooling tower performance evaluation:

These are the following parameters used to measure the performance of cooling tower

a) Range:

This is the difference between the cooling tower water inlet and outlet temperature. A high

Cooling tower Range means that the cooling tower has been able to reduce the water temperature

effectively, and is thus performing well. The formula is:

Range (°C) = [Cooling water inlet temp (°C) – Cooling water outlet temp (°C)]

b) Approach:

This is the difference between the cooling tower outlet coldwater temperature and ambient

wet bulb temperature. The lower the approach the better the cooling tower performance. Although,

both range and approach should be monitored, the `Approach’ is a better indicator of cooling tower

performance.

Approach (°C) = [Cold water outlet temp (°C) – Wet bulb temp (°C)]

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


c) Effectiveness:

This is the ratio between the range and the ideal range (in percentage), i.e. difference

between cooling water inlet temperature and ambient wet bulb temperature, or in other words it is

= Range / (Range + Approach). The higher this ratio, the higher the cooling tower effectiveness.

Effectiveness (%) = 100 x (CW temp – CW out temp) / (CW in temp – WB temp)

d) Cooling capacity:

This is the heat rejected in kCal/hr or TR, given as product of mass flow rate of water,

specific heat and temperature difference.

e) Evaporation loss:

This is the water quantity evaporated for cooling duty. Theoretically the evaporation

quantity works out to 1.8 m3 for every 1,000,000 kCal heat rejected. The following formula can be

used

Evaporation loss (m3/hr) = 0.00085 x 1.8 x circulation rate (m3/hr) x (T1-T2)

T1 - T2 = temperature difference between inlet and outlet water

f) Cycles of concentration (C.O.C):

This is the ratio of dissolved solids in circulating water to the dissolved solids in make up

water.

g) Blow down losses:

Blow down losses depend upon cycles of concentration and the evaporation losses and is given by

formula:

Blow down = Evaporation loss / (C.O.C. – 1)

h) Liquid/Gas (L/G) ratio:

The L/G ratio of a cooling tower is the ratio between the water and the air mass flow rates.

Cooling towers have certain design values, but seasonal variations require adjustment and tuning of

water and air flow rates to get the best cooling tower effectiveness. Adjustments can be made by

water box loading changes or blade angle adjustments. Thermodynamic rules also dictate that the

heat removed from the water must be equal to the heat absorbed by the surrounding air. Therefore

the following formulae can be used:

L (T1 – T2) = G (h2 – h1)

L/G = (h2 – h1) / (T1 – T2)

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


Where:

L/G = liquid to gas mass flow ratio (kg/kg)

T1 = hot water temperature (0C)

T2 = cold-water temperature (0C)

h2 = enthalpy of air-water vapor mixture at exhaust wet-bulb temperature

h1 = enthalpy of air-water vapor mixture at inlet wet-bulb temperature

f) Water Make-up:

Water losses include evaporation, drift (water entrained in discharge vapor), and blow down (water

released to discard solids). Drift losses are estimated to be between 0.1 and 0.2% of water supply.

Evaporation Loss = 0.00085 * water flow rate (T1-T2)

Blow down Loss = Evaporation Loss/ (cycles-1)

where cycles is the ratio of solids in the circulating water to the solids in the make-up water

Total Losses = Drift Losses + Evaporation Losses + Blow down Losses

Cooling Tower Efficiency calculation:

The cooling tower efficiency can be expressed as

μ = (ti - to) 100 / (ti - twb) Where

μ = cooling tower efficiency - common range between 70 - 75%

ti = inlet temperature of water to the tower (oC, oF)

to = outlet temperature of water from the tower (oC, oF)

twb = wet bulb temperature of air (oC, oF)

The temperature difference between inlet and outlet water (ti - to) is normally in the range 10 -

15 oF.

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


Wet bulb temperature:

Wet bulb temperature is the lowest temperature that can be reached by the evaporation of

water only. It is the indication of amount of moisture in the air. Wet bulb temperature is an

important factor in performance of evaporative water cooling equipment, because it is the lowest

temperature to which water can be cooled. For this reason, the wet bulb temperature of the air

entering the cooling tower determines the minimum operating temperature level throughout the

plant, process, or system. Theoretically, a cooling tower will cool water to the entering wet bulb

temperature. In practice, however, water is cooled to a temperature higher than the wet bulb

temperature because heat needs to be rejected from the cooling tower.

Dry bulb temperature:

The temperature of air measured by a thermo meter freely exposed to air but shielded from

radiations and moisture. It doest not indicate moisture.

Methods to enhance the efficiency of cooling tower:

a) Optimize cooling water treatment:

Cooling water treatment (e.g. to control suspended solids, algae growth) is mandatory for

any cooling tower independent of what fill media is used. With increasing costs of water, efforts to

increase Cycles of Concentration (COC), by cooling water treatment would help to reduce make up

water requirements significantly. In large industries and power plants improving the COC is often

considered a key area for water conservation.

b) Install drift eliminators:

It is very difficult to ignore drift problems in cooling towers. Nowadays most of the end user

specifications assume a 0.02% drift loss. But thanks to technological developments and the

production of PVC, manufacturers have improved drift eliminator designs. As a result drift losses can

now be as low as 0.003 –0.001%.

c) Cooling tower fans:

The purpose of a cooling tower fan is to move a specified quantity of air through the

system.The fan has to overcome the system resistance, which is defined as the pressure loss, to

move the air. The fan output or work done by the fan is the product of air flow and the pressure loss.

The fan output and kW input determines the fan efficiency.The fan efficiency in turn is greatly

dependent on the profile of the blade. Blades include:

Metallic blades:

Which are manufactured by extrusion or casting processes and therefore it is difficult to

produce ideal aerodynamic profiles

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


Fiber reinforced plastic (FRP) blades:

These are normally hand molded which makes it easier to produce an optimum aerodynamic

profile tailored to specific duty conditions. Because FRP fans are light; they need a low starting

torque requiring a lower HP motor, the lives of the gear box, motor and bearing is increased, and

maintenance is easier. A 85-92% efficiency can be achieved with blades with an aerodynamic profile,

optimum twist, taper and a high coefficient of lift to coefficient of drop ratio.

Why performance of cooling tower is lowered and how it can be improved:

Cooling tower performance is lowered:

• Due to scale build up on the tower heat exchange surfaces.

• Due to loss of air flow across the heat exchange surfaces.

• Due to improper water flow

Cooling tower performance can be improved by:

• Adding tower cell capacity.

• Checking for the efficiency losses described above.

• Replacing the heat exchange surfaces with new clean fill.

• Checking for proper air flow.

• Adjusting the water flow.

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


12.2 Assignment # 02 calculation of different chemicals used in cooling tower.

(a) Find out the actual quantity of NALCO-73204 if it is 50 ppm of blow down and blow down

average is 42m³/hr?

Ppm = Wt % or vol % of solute

Wt % or vol % of solution

1 m3 is equal to 1000 liters

1 kg is approximately equal to 1 liter

So 1 m3 is equal to 1000 kg

Actual quantity of NALCO-

73204 =

= 50.4 kg/ day

(b) Find out the actual quantity of NALCO-7356 if it is 25-30 ppm (27.5 ppm avg.) of blow down

and blow down average is 42 m³/hr?


7356 =

= 27.72 kg/ day

(C} Find out the actual quantity of NALCO-3434 if it is 0.05ppm of recirculate rate and recirculation

rate is 11800 m³/hr?


3434 =

= 14.16 kg/ day

50 42 m³ 1000 kg 24 hr

106 hr 1 m³ 1 day

27.5 42 m³ 1000 kg 24 hr

106 hr 1 m³ 1 day

0.05 11800 m³ 1000 kg 24 hr

106 hr 1 m³ 1 day

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


(D) Find out the actual quantity of NALCO-7330 if it is 16.5ppm of system volume and system

volume is 2170 m³/hr?


7330 =

= 859.32kg/ day

(E) Find out the actual quantity of NALCO-8506 if it is 5ppm of system volume and system volume

is 2170 m³/hr?


8506 =

= 260.4 kg/ day

(F) Find out the actual quantity of chlorine if it is 0.1-0.15ppm (0.125ppm avg.) of recirculate rate

and recirculation rate is 11800 m³/hr?

Actual quantity of chlorine

=

= 35.4 kg/ day

16.5 2170 m³ 1000 kg 24 hr

106 hr 1 m³ 1 day

5 2170 m³ 1000 kg 24 hr

106 hr 1 m³ 1 day

0.125 11800 m³ 1000 kg 24 hr

106 hr 1 m³ 1 day

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Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


(G) Find out the actual quantity of sulfuric acid if it is 167ppm of make up water and make up

water rate is 118 m³/hr?

Actual quantity of

H2SO4 =

= 472.94 kg/ day

12.3 Assignment # 03 Find out the range, approach, percentage effectiveness, and evaporation losses, blow

down requirements; make up water requirements and efficiency of cooling tower? if inlet cooling

water temperature is 45 degree C, outlet cooling water temperature is 34.5 degree C, and wet

bulb temperature is 30.13, dry bulb temperature is 5 to 47 degree C, cooling water flow is 10,000

m3/ hr, cooling tower fan flow is 2248920 m3/ hr, density of air is 1.8 kg/ m3, cycle of

concentration is 4.5.

Solution:

1) Range = Cooling water inlet temp. – Cooling water outlet temp.

= 45 – 34.5

= 10.5 0C

2) Approach = Cooling tower outlet cold water temp. – Wet bulb temp.

= 43.5-30.13

= 4.37 0C

3) % effectiveness = Range / (Range + Approach)

= 10.5/ (10.5+4.37)

= 0.7061

4) Evaporation losses = 0.00085(1.8) (cooling water flow rate) (inlet cooling water temp.–outlet

cooling water temp.)

= 0.00085(1.8) (10000) (45 – 34.5)

= 160.65 m³ / hr

167 118 m³ 1000 kg 24 hr

106 hr 1 m³ 1 day

71

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


5) Blow down losses = evaporation losses / (cycle of concentration-1)

= 160.65 / (4.5-1)

= 45.9 m³/ hr

6) Make up water = evaporation losses+ blow down losses + drift losses

***Drift losses usually 0.1 to 0.2 %

So drift losses = 0.002 (100000)

= 20 m³/ hr

Make up water = 160.65 + 45.9 + 20

= 226.55 m³/ hr

7) Efficiency =100* (Cooling water inlet temp. - Cooling water outlet temp.)

(Cooling water inlet temp. - Wet bulb temp. )

= 100*(45-34.5)/(45-30.13)

=70.61%

72

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


No. of Tables: Table 1 ................................................................................................................................................... 22

Table 2 ................................................................................................................................................... 23

Table 3 ................................................................................................................................................... 23

Table 4 ................................................................................................................................................... 24

Table 5 ................................................................................................................................................... 26

Table 6 ................................................................................................................................................... 29

Table 7 ................................................................................................................................................... 31

Table 8 ................................................................................................................................................... 33

Table 9 ................................................................................................................................................... 52

Table 10 ................................................................................................................................................. 55

73

Muhammad Ashraf

B.Sc Chemical Engg.

Punjab University


(1) (2) (3) (4) (5) (6) (7) (8)

Bibliography 1. Kemmer F.N. The Nalco Water Handbook, Edition second. Malaysia : McGraw Hill, International

Edition, 2003.

2. G.T, Austin. Shreve's Chemical Process Industries, Edition Fifth. Malaysia : McGraw

Hill,International Edition.

3. Chattopadhyay.P. Unit Operations of Chemical Engineering, Vol 1. Delhi : Khanna Publisher, 2003.

4. N.P, Chopey. Hndbook of Chemical Engineering Calculations, Edition 2. Singapore : McGraw Hill

International Edition, 1994.

5. McCabe W.L, Smith J.C and Harriot P. Unit Operations of Chemical Engineering, Edition 7. s.l. :

McGraw Hill International Edition, 2005.

6. Karrasik I.J, Krutzsch W.C, Frazer W.H. Pump Handbook, Edition 2. Malaysia : McGraw Hill

International Edition, Industrial Engineering Series, 1986.

7. Corporation, JGC. Mid Country Refinery Project. Mehmood Kot, Pakistan : s.n.

8. Limited, Pak Arab Refinery. Refinery Training Manual, Vol 1,2,3,4,5,6. Mid Country Refinery

Project, Mehmood Kot, Pakistan : Shaizoo Islam Printers Multan,Pakistan.

Parco internship report

Engineering

Transcript of Parco internship report