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Internship Report 2013

MAKORI

Submitted to: Field in charge

Submitted by:

RAO AHSAN ATTA

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Department of Chemical Engineering MEHRAN University of Engineering and Technology

JAMSHORO Hyderabad

PR EFACE:

The report includes activities and processes that I learnt during my internship at

MAKORI EPF.

This report highlights the events that occurred during my stay at MAKORI PLANT.

It also briefly discusses the processes that are going on in this facility.

This report is provided with the illustrations and the flow charts where ever

needed so that reader can be able to fully understand the basics of any process.

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TABLE OF CONTENTS

INTRODUCTION……………………………………………………………………………………………5

Safety GUIDANCE…………………………………………………………………………………………5

WELL HEAD

(A)PURPOSE OF WELL HEAD………………………………………………………………………9

(B)TYPES OF CASING ………………………………………………………………………………….9

(C)CHRISTMAS TREE & ITS PARTS ……………………………………………………………..9

(D)CONCEPT OF SSSV & SSV……………………………………………………………………..11

(E)CHOKE MANIFOLD & ITS TYPES…………………………………………………………….11

(F)PURPOSE OF WELL HEAD CONTROL PANNEL………………………………………..12

(G) COMPOSITION OF FLUID…………………………………………………………………....12

(H)HYDRATE FORMATION &ITS CAUSE……………………………………………………..12

(I)CHEMICAL INJECTION…………………………………………………………………………...13

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SEPARATION PROCESS

Principle of Separation……………………………………………………………………….….….13

(A)PURPOSE OF SEPARATION……………………………………………………………….…...14

(B)TWO & THREE PHASE SEPARATOR……………………………………………………..….14

(C)SLUGCATCHER & ITS TYPES………………………………………………………………..….16

(D)SAFETY VALVE & ITS CONCEPT………………………………………………………….…..17

CRUDE STABILIZATION

(A) 1st stage Sep………………………………………………………………………………….….…..18

(B) 2nd stage Sep………………………………………………………………………………….……..19

(C) Heat exchanger & crude heater……………………………………………………….…….19

(D) 3rd stage degasser ………………………………………………………………………….…….20

(E)Storage tanks………………………………………………………………………………….………21

GAS PROCESSING

(a)HCDP CONCEPT……………………………………………………………………………………...22

(B) AIREL COMPRESSOR………………………………………………………………………….…..22

(C)FILTER COALESCER …………………………………………………………………………….….24

(D) G/G EXCHANGER………………………………………………………………………………..…25

(E)G/L EXCHANGER……………………………………………………………………………………..26

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(F)LTS………………………………………………………………………………………………………….28

(G)REFRIGERATION CYCLE…………………………………………………………………….……29

(H)GLYCOL CIRCUIT……………………………………………………………………………….…..32

(I)DETHANIZER……………………………………………………………………………………….….35

SALE GAS METERING SKID……………………………………………………………………………35

CLOSE DRAIN OPEN DRAIN………………………………………………………………………….36

HOT OIL SYSTEM FOR HEATING PURPOSE…………………………………………….……..37

FLARE SYSTEM……………………………………………………………………………………….…….37

PUMPS………………………………………………………………………………………………………….38

VALVES…………………………………………………………………………………………………..…….40

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INTRODUCTION

Makori is located in District karak K.P.K Pakistan. The set up in Pakistan at present comprises of three sites namely EPF, CPF and GPF processing facilities.

SAFETY GUIDANCE:

Personal protective equipments (PPE):

These include hard helmets, gloves, goggles, safety shoes, masks etc. Helmet and safety shoes are essential when in the plant area while other equipments may be used as per required. These equipments should be kept in good condition so as to avoid any unfortunate incident. Damaged equipments should be repaired or discarded. Lose clothing should be avoided as they may get stuck in machinery or may cause other problems. Proper coveralls should be worn by workers all the workers.

Fire Hazards: Fire is a major disaster in the oil and gas industry. Proper precautions should be taken to avoid any sparks/fire, which may take the shape of a major disaster especially in the oil and gas industry. Therefore it is essential to have proper knowledge of fire causes and one should always be careful, to prevent any misfortunate incident. Fire can be caused at anyplace containing oxygen, fuel and heat.

Types of Fire:

Fire is mainly of four types Hydrocarbon fire Electrical fire Chemical fire Paper/wood fire

Following instructions must be followed strictly while on plant area: Do not smoke in plant area. Do not ignite any type of object especially in plant area.

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Turn off mobile phones as they can produce spark. Use well insulated batteries in plant area. All electronic equipments must be intrinsically safe. Use tools that have a low chance of producing spark.

Fire Fighting Systems:

At MGP a complete firefighting and fire water system is present consisting of pumps, storage tanks, fire hydrants, foam trolleys and fire extinguishers. There are two main categories for firefighting system:

1) Fire Water System:

It is a large network of pipes and hydrants at various points in the facility. Fire water tank T-41-02 supplies fire water. A jockey pump P-42-02 with capacity of 125USGPM keeps the system pressurized at 100 psig with fire water from the fire water storage tanks filled by pumping water from the raw water reservoir. An electric motor driven fire water pump P-42-01A with capacity 1000 USGPM comes online when the pressure in the system drops to 30 psig. A third diesel engine driven pump P-42-01B with capacity 1000 USGPM comes online automatically when both the previous pumps fail or if the pressure still drops below 70 psi when electric driven pump is working. The fire water can be utilized by hydrants located at various locations in the facility. Hydrants have two types

Fire hydrant. Fire Hydrant Monitor.

In simple fire hydrants a hose pipe with nozzle is connected to the hydrant terminal. Fire hydrant monitor is a type of hydrant in which the nozzle is connected to hydrant terminal and upon opening of the discharge valve it can be used as a gun. It further has two types:

Oscillating FHM. Non-oscillating FHM.

2) Fire Extinguishers:

A fire extinguisher is an active fire protection device used to extinguish or control small fires, often in emergency situations. It is not intended for use on an out-of-

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control fire, such as one which has reached the ceiling, endangers the user (i.e. no escape route, smoke, explosion hazard, etc.), or otherwise requires the expertise of a fire department. Typically, a fire extinguisher consists of a hand-held cylindrical pressure vessel containing an agent which can be discharged to extinguish a fire. At MGP we have following agents for fire extinguishers:

o Dry chemical Powder o Aqueous foam forming liquids

There are following types of extinguishers in MGP: o Portable o CO2o Trolley

To operate a fire extinguisher a rule of PASS is used it is as below: o P—Pull the pin. o A—Aim the nozzle at the base of fire. o S—Squeeze the handle. o S—Sweep on the base of fire.

Makori 3, East- 1, East- 2 facility:

This facility which is located in K.P.K province has four wells, Makori 1, Makori3, Makori East -1 and Makori East-2 from these wells we are getting four things, amount of crude oil plus gas as well as water and others contaminations (salt etc), from four wells three wells are giving large amount of gas oil and gas mixture while the remaining one is closed.

Gas after further processing send to gas marketing company i-e SNGPL and crude oil after processing send to oil marketing companies i-e National Refinery Limited or Attock Limited Refinery because these companies purchase oil or gas from Mol or any other oil and exploration company if it has few things under controlled.

Process Specifications:

The current production rates of Makori EPF are as follows:

Production rate Average

Condensate Rate 8000 BPD

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Produced Water 550 BPD Sales Gas 30 MMSCFD.

The design capacity of MPF is as follows:

Production rate Total

Condensate rate 10,000BPD Sale Gas 43MMSCFD

Product Specifications (for gas)

Hydrocarbon Dew point <320F Water content <7 lb H2O/MMSCF Gross heat value >950/SCF Reid Vapor Pressure <7 psi Pressure <1100psi Temperature <120 degree F Wobb index >1220MM/SCF

Product Specifications ( for condensate)

Water content should be zero =zero Reid vapor pressure <7.2 psi at 100 degree F

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(1) Well head:

(a) Purpose of well head:

A wellhead is that part of an oil well which terminates at the surface, whether on land or offshore, where petroleum or gas hydrocarbons can be withdrawn. The primary function of wellhead is to anchor the casings and production tubing. The tubing hanger is located on top of the wellhead and serves to anchor the production tubing which runs down the well .The Christmas tree sits on top of the wellhead. Casings hanger holds the different casings which are necessary for protection of the production tubing. Pressure gauges between these hangers measure the casing/casing and casing/production tubing annulus pressures for pressure control and effluent.

(b) There are four types of casing;

Conductor casing (26-30 INCH)

Surface casing (20 INCH)

Intermediate casing (13 3/8 INCH)

Production casing (9 5/8 INCH)

Purpose of all casings is to reduce the unbalanced forces acts on the reservoir, to prevent from the corrosion, to prevent the production tube.

(c) Christmas tree & its parts;

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Christmas tree is an assembly of valves, spools and fittings for an oil well, named for its resemblance to a decorated tree.

Production and Kill wing Valves

Kill wing’s purpose is that it is used to kill the well by placing pumps which pumps the mud at high pressure even than the upcoming crude oil’s pressure which is normally from (3000psi-5000psi) the reservoir. And production valve is used to take the condensate, gas from the well.

Upper and Lower Master Valves

There are four types of valves present on a Christmas tree. The lower two valves are called the upper and lower master valves. These lie in the effluent flow path and allow/block the effluent to get to the surface. Both of these valves are gate valves and are manually operated.

Swab Valve

Swab valve is located on top of the tree and is manually operated. It lies in the path used for well interventions like wire line and coiled tubing. For such operations, a riser is rigged up on top of the tree and the wire or coil is lowered, purpose is that it is used for work over job means for acid injection to open closed pores deep inside the soil.

(e) Concept of sssv and ssv:

Sub surface safety valve (sssv)

This is a hydraulically operated piston controlled gate valve and is used to shutdown the plant during emergencies or for maintenance SSSV is placed 70meters (200 ft) below the well.

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Surface safety valve (SSV)

Surface safety valve (SSV) is a hydraulically actuated fail-safe gate valve.

The SSV is used to quickly shut down the well Stream, also due to overpressure, failure, a leak in downstream equipment, or any other well and plant emergency requiring an immediate shut-in

The SSV remotely operated by an emergency shutdown device (ESD) which can be triggered automatically by high or low pressure pilot actuators. If an emergency occur, this feature reduce the possibility of any kind of danger to the human life.

(f) Choke manifold & its types:

Choke means to stop. The purpose of choke is, to use this at oil exploration well is to regulate the flow but the main purpose is to decrease or increase the flow rate and by changing the flow rate the pressure of crude oil changes, it can be of various size for 2 inch of choke, it is divided in 64 parts on opening 16 part, pressure reduces at about 1000psi and by fully open this pressure can raise to maximum design pressure of choke 1500 psi.

Types of chokes

There are two main types of chokes;

1. Fixed choke

2. Adjustable choke

3. Remote choke

(g) Purpose of well head control panel:

Well head control panel is placed near the well the purpose of this panel is to produce hydraulic pressure for the SSV & SSSV as it carries two pumps which maintains the pressure of 3000psi for SSV and 9000psi for SSSV we supply almost 60psi of instrument air to both. It also carries ESD (emergency shutdown button) and pressure gauges of SSSV & SSV hydraulic as well as header pressure of SSV & SSSV, gauges of instrument air supplied to them.

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(h) Composition of fluid :

Fluid which we extract from the reservoir can consist of crude only, crude+ gas, gas only, condensate, condensate +gas+ water and other contaminations.

(i) Hydrate Formation & its cause:

Hydrate formation occurs when free water present in gas because the water molecules trap with gas molecules at low temperature high pressure.

Gas molecules easily enters in the crystal lattice of water molecules on lowering the temperature gas condenses and free water is produced as gas changes its phase first to liquid then to solid and formation of ice occurs which can block the lines causing explosion , reduces gas capacity or line capacity.

(j) Chemical injection:

The inlet header incorporates a chemical injection system which includes the injection of an antifoaming agent, corrosion inhibitor, demulsify, and methanol. Antifoaming Agent this chemical is injected into the pipeline just before it enters the system to prevent foam formation which gives false level indications to the level controllers. Corrosion Inhibitor this is injected to reduce corrosion rate in the pipelines and the system equipment

(2)Separation process:

Principle of separation depends on:

Momentum Gravity settling Density difference

Basic components of separator:

Deflector plate Weir plate Mist eliminator Vortex breaker Coalescing/Dixon plates

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PRINCIPLE OR THEORY OF SEPARATION:

The primary separation takes places in the gravity separators. The deflector plates break down the momentum of the high pressure effluent moving into the inlet. The fluids will then separate out on the basis of the gravity. The gas being the lighter of the phase will tend to accumulate at the top and is extracted by the Mist Extractor. The mist extractor also eliminates the any moisture in the gas stream. Coalescing plates will also gather any liquid in the gas phase and unites them in the form of small droplets which will drop down in the liquid stream. A weir plate is used to strip out the condensate layer. Also the function of the weir plate is to stop the flow of water into the next phase of separation because its presence will disturb the process. Vortex breakers are used at the outlets of the water and condensate in order make the flow laminar. Due to difference in density of water and condensate water settles at the bottom while condensate at the top then by using weir plate which separates oil from water. The oil spills to the right section of separator and the water is separated out from the bottom of separator.

(a) Purpose of separation:

Oil and Gas Reservoirs contain hydrocarbon fluids, water and associated solids such as sand, which are brought to surface through the producing wells for subsequent treatment and export.

These fluids require separation and treatment in order to meet the various export and storage specifications.

(B)TWO PHASE & THREE PHASE SEPARATORS

The segregation of well stream fluid takes place in a Separator. This vessel is manufactured in three forms: Spherical, Vertical and Horizontal. Horizontal and vertical separators are installed at different location of BPP.

Two-Phase Separators

In both horizontal and vertical two-phase separators, the well stream enters at the side or end of the vessel. The lighter fluid (usually gas) passes out at the top, and the heavier fluids allowed settling and being withdrawn from the bottom of the vessel.

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Three-Phase Separators

Flow in a three-phase separator is, that fluids entering at one end of the vessel and the liquids being allowed to settle out in the inlet and outside of the weir in the vessel.

Entering fluid may contains sand and sediments which are removed with special internal devices to collect and dispose of solid that separate.

Gas Scrubber: Separates a liquid from gas stream with high gas to liquid ratio.

Knockout Drum: Separates a higher degree of liquid entrained in gas stream. The separation of free water from gas stream is an example of this.

Factors that affect separation:

Difference in density of fluids Separation is easier when density difference is greater.

Residence time Separation is more efficient with more time. Coalescing surface area Separation is more efficient with greater area. Separator may be classified in two ways:

By the position or shape of the vessel, or by the number of fluids to be segregated.

The following two vessel shapes are commonly used: Vertical and Horizontal.

The number of phases refers to the number of streams that leave the vessel,

Separator types

Horizontal

High gas-oil ratio well stream. Oil-water separation when long residence time is necessary 3. Area limitations

Vertical

Low gas-oil ratio well stream. Where a high liquid level is present.

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Three phase separator diagrams:

(c) Slug catcher & its purpose:

Pipelines that transport both gas and liquids together, known as two-phase flow, can operate in a flow regime known as slugging flow or slug flow. Under the influence of gravity liquids will tend to settle on the bottom of the pipeline, while the gases occupy the top section of the pipeline. Under certain operating conditions gas and liquid are not evenly distributed throughout the pipeline, but travel as large plugs with mostly liquids or mostly gases through the pipeline. These large plugs are called slugs.

Slugs exiting the pipeline can overload the gas/liquid handling capacity of the plant at the pipeline outlet, as they are often produced at a much larger rate than the equipment is designed

Purpose:

A slug catcher is a vessel with sufficient buffer volume to store the largest slugs expected from the upstream system. The slug catcher is located between the outlet of the pipeline and the processing equipment. The buffered liquids can be

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drained to the processing equipment at a much slower rate to prevent overloading the system. As slugs are a periodical phenomenon, the slug catcher should be emptied before the next slug arrives.

Slug catchers can be used continuously or on-demand. A slug catcher permanently connected to the pipeline will buffer all production, including the slugs, before it is sent to the gas and liquid 17 handling facilities. This is used for difficult to predict slugging behavior found in terrain slugging, hydrodynamic slugging or riser-based slugging. Alternatively, the slug catcher can be bypassed in normal operation and be brought online when a slug is expected, usually during pigging operations. An advantage of this set-up is that inspection and maintenance on the slug catcher can be done without interrupting the normal operation.

Type of slug catcher:

Finger harp style: This type of slug catcher is economical to catch large slugs and is applicable for high volume.

Single barrel horizontal: This is a three phase separator and is applicable for high liquid to gas ratio.

Double barrel harp style: This type of slug catcher is used to catch large slugs and is applicable for high gas flow rates.

(d) Safety valve & its concept:

A safety valve is a valve mechanism for the automatic release of a substance from a boiler, pressure vessel, or other system when the pressure or temperature exceeds preset limits.

Pressure safety valve:

It is part of a bigger set named pressure safety valves (PSV) or pressure relief valves (PRV). Safety valves are installed on top of the vessel that connects it to the HP Flare system. Two, Pilot operated Pressure safety valves (PSV‟s) are installed on top of the vessel that will operate to flare the excess gas and to normalize the pressure inside the vessel within the design range which is fed to the PSV‟s. This is necessary to ensure the vessel safety incase the pressure inside the vessel increases beyond set-point given to the PSV

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Blow down valve (BDV):

These types of valves are controlled by instrument air, by which they

remain closed it opens in level 1 shut down in which PCV opens & plant depressurizes so they continuously needs instrument air .The purpose of BDV is to protect the plant in case of destruction of one unit, in case of leaking of gas.

( 3) Crude stabilization process:

First Stage Separator (HP Separator) :

Introduction: It horizontal three phase separator. It uses gravity, retention time to separate the condensate and water from raw gas.

Purpose: Its purpose is to separate the condensate and water from well fluid.

Detail Description:

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The basic function of 1st stage separator is the same as that of a typical separator. It works under high pressure and high temperature (i.e. 1000 psig and 100 0F). It can also be used for the sour gas handling as well. A level gauge LG is installed to monitor the level of the water. When water level reaches 80%, the water is drained so that no water can come in the condensate line. Two pressure safety valves (PSV’s) are installed at the top of the HP separator which are used for the safety of the vessels.PSV are set at pre-set pressure when the pressure in the vessel increases beyond that pressure it is given to the flare system. The valves are shut down valve (SDV) and Blow down valve (BDV). Both are given different set points.

Second Stage Separator (MP): It also consists of the same parts as that of the 1st stage separator. But it operates at low pressure and low temperature (i.e. 150-250 psig and 96-106 0F). After leaving the 2nd stage separator the gas enters into the gas compressor package and the condensate flows towards the crude/crude heat exchangers.

Crude/Crude Heat Exchanger and Crude Heater:

Introduction: Heat exchanger is a plate type heat exchanger (duty 1.2mmbtu/hr) while crude heater is an indirect-fired heater and consists of a U shape fire tube mounted on a flange at one end of a non-pressurized vessel.

Detail Description: Oil discharged from the second stage separator is then preheated as it passes through the plate type crude/crude exchanger. The next stage of crude oil heating is done by the crude heater that is an indirect-fired heater there are two types of heater.

Old heater (duty 2mmbtu/hr) indirect fire heater water medium is used in this.

New heater (duty 6mmbtu/hr) indirect fire heater water medium is used in this.

The crude oil is heated here and then made to flow into the degasser. The basic purpose of heating the crude is to reduce its viscosity. The cold condensate after leaving the cold outlet of the heat exchanger will enter into the crude heaterWhere it is heated to almost 125 c. ̊�

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3RD STAGE DEGASSER:

Introduction: It is a vertical type degasser and reason for its usage is that quantity of gas is very less and less turbulence is created.

Purpose: It aims at removing the lighter hydrocarbons present in it. Its main purpose is to maintain the RVP of condensate/crude by flashing i.e. removing of lighter hydrocarbons at lower pressure. Detail Description: After leaving the heat exchanger, the condensate enters into the 3rd stage degasser so as to remove any gases present in the condensate. It operates at low pressure and high temperature (i.e. 12 psig and 110 0F). Under these conditions the condensate gives off any dissolved gases. The gas will enter into the gas

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compressor for re-compression and then into the dew point control unit.

CRUDE TRANSFER PUMPS:There are three centrifugal pumps used here these are propeller type of pumps which takes suction and discharge at 180 degree transfer crude to the plate type heat exchanger where crude after exchanging heat goes towards the storage tanks.

Storage tanks After the complete processing of the condensate it is sent to storage tanks by the use of vertical type centrifugal pumps. The storage tank locality is classified into four banks A, B, C and D. Each bank is comprised of 5 storage tanks, connected in series with individual capacity of 500 barrels making one bank to store 2500 barrels.

The pressure vacuum relief valves are present on top of storage tank through which volatile products escapes out, blanket gas is provided to reduce oxygen concentration so a maximum set point given to it 0.6psi and minimum 0.03psi.

Each bank is provided with the level transmitter which sends signal to HMI apart from it level of each tank is monitored by level glass gauge. Condensate from it is supplied to NRL.

(4) GAS PROCESSING:

HCDP control system (MRU), HCDP concept, why to control HCDP.

In gas cycle we mainly concentrate on hydrocarbon (gas) dew point. The hydrocarbon dew point is the temperature (at a given pressure) at which the hydrocarbon components of any

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hydrocarbon-rich gas mixture, such as natural gas, will start to condense out of the gaseous phase.

The significance of HCDP is:

The gas has better burning capacity if HCDP is controlled. Gas will not convert to liquid in pipelines Corrosion rate is reduced To control G.H.V.

The heavier hydrocarbons must be removed to control the HCDP; this is done at Makori in Mechanical Refrigeration Unit (MRU), because if HCDP increases then G.H.V also increases. The SNGPL requirement for HCDP is 320F.

GAS PROCESSING CIRCUIT EXPLAINATION:

Gas from MAKORI East-1 & East-2 after slug catcher comes in inlet separator while from MAKORI 3 comes in 1st stage separator then both these meet at a point goes to mechanical refrigeration unit, but gas from 3rd stage degasser and 2nd stage separator plus from DETHANIZER goes in Ariel compressor.

Ariel compressor:

This is a multi stage double acting compressor has four stages in which it has 6 compressor cylinder and a Waukesha engine having 12 cylinder. The difference in engines cylinder and compressor cylinder is just of spark plugs that engine cylinder has spark plugs.

Double acting is used for maximum flow of gas as compare to single acting, the difference between double and single acting compressor is that in double acting suction and discharge occurs simultaneously

The compressor is used for compression of low pressure gas coming from 2nd stage separator, DETHANIZER and degasser. Gases from the 2nd stage separator degasser and heads towards the compressor called Ariel compressor for compression. The need for compression is because these all are low pressure gases

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with pressure of 150 psi from 2nd stage separator and 170 psi from DETHANIZER and 12psi from degasser compress to a high pressure 1000psi after the compression it is entered into the line heading towards the inlet filter coalesce for hydrocarbon dew point control.

Inlet Filter Coalesce:

The gas from the HP-separator directly enters into inlet coalescer while the gas from MP-Separator along with the gas from third stage degasser after passing through airel compressor enters into inlet filter coalescer. It is a vertical column which contains a coalescer filter and mist extractor. The filter is provided to remove any suspended droplets from the gas. It is divided into two halves; upper and lower. From both halves the condensate is drained. The condensate is drained manually, which enters into the line heading towards the heat exchanger. The pressure in the coalescer is above 6800Kpa with the inlet gas temperature of 100F.

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GAS/GAS EXCHANGER:

Purpose of G/G, G/L exchanger is to cool the raw gas & to reduce load on the chiller.

The heat exchanges in this made Shell and Tube type heat exchangers. The main purpose of heat exchanger used here is to reduce the temperature of the gas for further process. Low temperature helps to separate the condensate and gas easily from one another.

It is called gas/gas heat exchanger, because gas is flowing on both the shell and tube side of the heat exchanger. On shell side it contains cold gas coming from the LTS and on tube side it contains hot gas from inlet filter coalesce. Hot gas leaving the exchanger enters in the chiller. Temperature of cold gas from

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LTS -12C, temperature of hot gas from coalesce 37oC, temp of hot gas leaving the exchanger -6oC.

Tube and shell sides of Gas/Gas Exchanger

GAS/LIQUID EXCHANGER:

The other type of heat exchanger used is gas /liquid heat exchanger in which cold condensate from LTS is used to cool the hot gas coming from coalesce. It is employed here to distribute the load of gas/gas exchanger, it bears 15~20% of total load. The area and time of contact is less in the gas/liquid exchanger because of its small size making it less efficient than gas/gas exchanger. After passing from it gas enters into the chiller.

Temperature of hot gas from coalesce 37oC, temperature of cold condensate from LTS 15oC, temperature of hot gas leaving the exchanger -1oC.

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G/G, G/L Heat exchanger and chiller plus LTS

CHILLER:

It is a kettle type heat exchanger. The function of chiller is to reduce the temperature of gas before it enters the Low temperature separator.

The raw gas enters into the tube side and exchanges heat with liquid propane present in the shell side of the chiller. In the process, raw gas losses heat and propane liquid gains heat and vaporizes. MEG is also injected into the chiller to prevent hydrate formation. Also the gas from the gas/liquid heat exchanger will join the line leading to the chiller. The low temperature gas leaves the chiller to enter the Low Temperature Separator (LTS). The propane leaves the chiller and enters into the scrubber located just above it.

Pressure inside the chiller 125KPA Operating temperature 20Oc Temperature of outgoing gas -12oC

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So after passing through the chiller gas is directed to LTS.

LOW TEMPERATURE SEPARATOR:

Separation occurs at low temperature. Same mechanism is employed here as in the case of 1st and 2nd stage separator i.e. Separation occurs on the basis of difference in specific gravity of absorbed glycol, condensate and gas. The glycol being heavier sinks to the boot (bottom) of its. The condensate being lighter rests on the top of glycol. Gas being lightest escapes from the top. This cooled gas after escaping from the its enters into the gas/gas exchanger where it cools the incoming gas and then enters into the sales gas line. The condensate after leaving its first cools the incoming stream of gas in the gas/liquid exchanger and then enters into the de-etherizer fractionating tower from the top. The construction of it’s similar to the hp or mp-separator but it does not contain any coalescing plates.

Temperature in LTS is -12oC, Pressure in LTS 7900 KPA.

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(E) GENERAL INTRODUCTION OF REFRIGERATION CYCLE OR PROPANE CYCLE:

TCV

Coolant line

U-tube heat exchanger

Propane vapors

LCV

LCV

Propane vapors to MYCOM

Chiller

MyCom

Compressor

Econ

omiz

er

Refrigerant accumulator

Cool

a nt

pum

p Refr

iger

ant /

oil

sepa

rato

r

Condenser

Desicant filter

REFRIGERANTION EXPLAINATION:

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Propane is used as a coolant which cool the gas in chiller after cooling it evaporates in above suction scrubber so the phase change occurs from liquid to vapors for recycle the propane we brings it back again in liquid form , for that we do compression , condensation and throttling and evaporation in chiller.

REFRIGERANT COMPRESSOR:

Rotary screw compressor is installed to compress propane vapors. The compressor takes suction at 110KPa & the discharge pressure is 1050 KPA while the discharge temperature is in the range of 78-87 degree C. Lube oil is also added to the compressor to act as a coolant and as a lubricant. This mixture of lube oil and propane vapors is compressed and sent to refrigerant oil separator.

REFRIGERANT CONDENSOR:

Refrigerant vapors leave the refrigerant oil separator and enter in to the refrigerant condenser. This is a forced draft fin fan condenser and involves the refrigerant passing through a series of tubes which are cooled by air forced upwards by the fan blades. Fins will enhance the cooling effect and therefore condensation of propane.

REFRIGERANT ACCUMULATOR:

The refrigerant vapors from oil separator are cooled and condensed in the refrigerant condenser and then the refrigerant is accumulated in the refrigerant accumulator.

U-TUBE HEAT EXCHANGER:

From accumulator it comes in u-tube heat exchanger, where it exchanges heat with gas coming from de-etherizer and than passes through throttling valve which lowers its temperature and it further condenses due to which then goes to economizer.

ECONOMIZER:

The purpose of economizer is to reduce the load on the compressor and make the refrigeration process economical. A level controller on the economizer operates the level control

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valve which works as an expansion valve to reduce refrigerant pressure from approximately 1250 KPA to 360 KPA, resulting in a temperature drop. As a result the refrigerant further cools to -6 °C. The propane vapors have pressure of about 400 KPA, which is sent to accumulator through a PCV.

REFRIGERANT CHILLER: Cold propane comes to chiller, where it exchanges heat with raw gas coming from gas/gas and gas/liquid exchanger. The raw gas losses heat and propane liquid gains heat and vaporize. The propane leaves the chiller and enters into the scrubber located just above it. The level of the propane is controlled by the LCV installed on the upstream of the chiller. The removal of heavier hydrocarbons lowers the HCDP of the gas.

SCRUBBER:

Scrubber is a vessel. When the propane inside the chiller vaporizes, it enters in scrubber located above it. Compressor takes suction from scrubber. The purpose of scrubber is to supply continues suction to compressor. So the propane vapors transfer to compressor from scrubber.

(f) MONOETHYLENE GLYCOL CIRCUIT:

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Liquid/Gas exchanger

Sock & Charcoal filterHeat

Gas/Gas exchanger

chiller

Low temp separator

L.T.S

MEG Reboiler

Accumulator

Flas

h Ta

nk

Vapor out

Stack

Fin type Heat Exchanger

If MEG is not used hydrates are formed and hydrate formation causes blockage of the pipes. A solution of MEG (80% MEG, 20% Water) is used to absorb hydrate from the Raw Gas. This water content increases the freezing point of the MEG. It should be noted that pure MEG has F.P of -13 C, but when water is added its FP becomes -43 C. so this addition of water prevents condensation of MEG in the LTS as it passes through it because the temperature in LTS is -14 C. .

Best absorption of water occurs whenPressure is high, Temperature is low. That’s why, MEG is 1st

cooled by passing it through LTS and when it become rich it is heated to remove the moisture.

LOW TEMPERATURE SEPARATOR:

As MEG is added to remove moisture from the gas, then it moves to LTS. Being the heaviest one it is present at the bottom of the

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LTS from where it is directed to still column of glycol regenerator for pre heating.

GLYCOL FLASH TANK:

The pressure in the flash tank drops to 360Kpa from around 7900Kpa. Due to this sudden pressure drop, the hydrocarbons that are absorbed in the glycol are flashed out. The temperature in the glycol flash tank remains around 80-90oC.

FILTER:

MEG after exiting from flash tank enters into the sock filter which removes any solid particles present in the glycol. It also passes through charcoal filter which removes any suspended particles of hydrocarbon. Charcoal filter contains the porous charcoal filter element.

MEG REBOILER:

Glycol after exiting through filters, showered into the glycol regenerator still column, exchanges the heat with the steam from re-boiler. Water vapor and some glycol vapor are driven from re-boiler up still column. Any glycol vapor above the feed point is retained by condensing a small amount of water reflux in the top of column. The wide difference between the boiling points of water and MEG provides an easy effective separation of two components.

MEG ACCUMULATOR: The accumulator act a reservoir as well as normally containing glycol-to-glycol heat exchanger.

(G) D E-ETHANIZER

It is used to remove lighters from the condensate in order to get required value of Reid vapor pressure. It contains packers that are made up of Paul rings. The packers basically hinder the flow of the heavier hydrocarbon liquids due to which the lighter parts are removed from the liquid in the form of vaporized product. After passing through the Paul rings, the NGL maintains its level

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on the chimney tray from where it is directed to the re-boiler of the de- etherizers. In re-boiler, the NGL is heated to give out any gases. The heating in the re-boiler is done through TEG.

Re-boiler is of tube/shell type with TEG passing through tubes and NGL on shell side. The gas is removed from the top. The condensate after leaving the DETHANIZER is entered into the line that head towards the heat exchanger for pre heating and then towards condensate heater after which condensate stabilization process continues as explained earlier. The overhead vapors from the DETHANIZER first enter into the u-tube exchanger on the tube side and then directed into the line heading towards the AIREL compressor.

(5) SALE GAS METERING SKID:

The gas from LTS then comes to Gas-Gas exchanger where it exchanges the heat with the Raw Gas coming from Inlet filter coalescer from there it is send to Metering Skid. After the gas has been dehydrated and its dew point has been controlled, the gas is required to be metered. The pressure is also controlled at the metering skid. A meter run is installed just before the orifice meter so as to calculate the differential pressure at the skid. The equipments installed at the metering skid are:

Moisture analyzer: for measuring the water content. Gas chromatograph: for gas composition. Barton chart: to determine the differential pressure, static pressure and

temperature Orifice meter: to measure the flow rate Pressure control valves: to control the pressure Non return valves: to stop back flow of gas. Shut down valves: to completely shut down the production.

GAS CHROMATOGRAPHY

The purpose of gas chromatograph is to identify gas composition and to calculate the heating value (BTU/SCF) and HCDP (o F) of sales gas. The flow computer is used to analyze the data of GC and calculate the parameters. The inputs to the FC

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are the differential pressure, line pressure, GC data and the temperature. The GC gives the composition to the programmable logic control (PLC) and the moisture analyzer gives the gives the amount of moisture to the PLC. The PLC then gives the normalized composition to the FC. The FC is given some input functions which then measures different parameters. At the end of the month, billing is done on the basis of FC data.

(6) Close & open drain:

Water from 1st stage, 2nd stage, and 3rd stage degasser is drained to close header i.e. to HP flare KO drum that serves as collection vessel. The HP flare knock out drum is used for liquid storage which is then pumped to the oil water separator using the diaphragm pumps. Water from oil/water separator is plunged into the evaporation pond while condensate recovered from it is pumped to 3rd stage degasser. Open drain system collects rain water and overspill water tainted with hydrocarbons contains in the area. Fluid discharges are directed to the open drain system will flow by gravity.

(7) HOT OIL SYSTEM FOR HEATING PURPOSE:

The heat media used in the plant is tri ethylene glycol. The boiling point of TEG is 545 °F and its molecular formula is C6H14O4. Due to its high boiling point it is favorable to use it as a heat medium. The TEG heater heats glycol. The operating temperature of heater is 175°C. The heat media is circulated by two centrifugal pumps. These are electrically driven single stage centrifugal pumps with a flow of 100 GPM. The discharge pressure of the pump is 88 psi. The heated media is used at various points in the point. These are

MEG REBOILER DETHANIZER REBOILER Suction scrubber Chiller boot Refrigerant oil/separator

(8) FLARE SYSTEM:

There are two types of flare system LP & HP means low pressure and high pressure flares the excess gasses from high pressure vessels like separators, compressors etc goes to HP flare while from low pressure vessel like degasser goes to LP flare .why we do not give low pressure excess gas to HP flare because

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purpose of low pressure flare is to protect degasser from back pressure of high pressure vessels. BDV (blow down valves) & PSV (pressure safety valves) placed over vessels flares the excess gas in type of any emergency.

PUMPS:

Definition:

Pumps are the devices that take the suction at low pressure and discharge the liquid at high pressure.

Types:

They are classified into two main categories

Centrifugal pumps Positive displacement pumps.

The pumps that are installed at the facility belong to both categories. The centrifugal type pumps are installed at loading area, third stage degasser and refrigerant accumulator. The pump that is used to pump lube oil is gear pump, the pump used with glycol is plunger pump and the pump installed with the HP and LP knock out drums are diaphragm pumps that all fall into the category of PD pumps.

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CENTRIFUGAL PUMPS

Centrifugal pumps utilize the centrifugal force which is the force of spinning. This kind of pump works on the principle of centrifugal force i.e. when liquid falls on the centre of spinning plate, it is thrown outward from the centre. The part of centrifugal pump that spins the liquid is known as impeller. Liquid enters at the inlet port and flows through the eye of the impeller. As the pump shaft rotates, the impeller rotates with it. The rotating impeller throws the liquid outwards towards the rim of the impeller. Attached to impeller are the vanes that are curved and guide the liquid in the desired direction. Outer casing of the pump forms the shape of a volute. This gathers the liquid and channels it toward the discharge port. As the liquid reaches the discharge port its velocity decreases. The energy is transformed into pressure and the pressure of the liquid rises. The faster the impeller rotates, higher is the discharge pressure and flow rate of the pump. The centrifugal pump have higher flow rate as compared to PD pumps.

TYPES

Impeller and propeller

Impeller type centrifugal pumps are those which take suction at an angle of 90 degree while propeller type takes an angle of 180 degree. For high flow rate we use propeller type vertical centrifugal pumps but for high pressure we use impeller type pumps.

POSITIVE DISPLACEMENT PUMPS

A positive displacement pump is characterized by the reciprocating backward and forward motion of the pumping element with the constant volumetric capacity at constant speed and at any pressure. The main advantage of Pd pumps over the

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centrifugal pumps is that they have the ability to raise a liquid to higher pressure with less power but they give the pulsating flow. The pulsation can be minimized by the use of multiplex cylinder or using the double acting cylinders.

TYPES

Diaphragm, plunger and gear pump

There are three types of pumps used here diaphragm with HP & LP KOD,

Plunger pumps for glycol and gear pump for lube oil.

VALVES:

There are various types of valves some of them mainly used here are gate, globe, ball, butterfly valve. Pressure safety valves blow down valves so various sort of valves are in use here lets discuss with

GATE VALVE

These are fully open, fully close valve used to shut in or shut off the flow. But they take longest time to open and are costly as well.

They are bi directional and sensitive to vibration or leaks. They are used on high pressure line the pressure loss is minimal in such type

of valves.

GLOBE VALVE

We can open these valves partially to require percent and they are used to regulate the flow.

They also take long time to open or close and costly as well. They are also used for throttling because the pressure drop is highest. They have bubble tight shut off so no leaking occurs in them.

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BALL VALVE

These are fully open, fully close valve used to shut in or shut off the flow.

They minimize the time as well as the cost.

They are mainly used on gas streams because slurries settle down & disturb valve operation.

They can also be used for high capacity on excessive pressure lines.

BUTTERFLY VALVE

We can open these valves partially to require percent and they are used to regulate the flow.

They have quick opening and closing used to regulate the flow.

The pressure drop is little than globe so cannot be used for throttling.

They are economical than all but disc movement is unguided affected by turbulence flow.

Cavitations’ are big concern, contamination and leaks at the stem as well. ̊

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Needle Valve:

A needle valve is a type of valve having a small port and a threaded, needle-shaped plunger.

It allows precise regulation of flow, although it is generally only capable of relatively low flow rates.

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