Pakistan Oilfields Limted (POL) Internship Report

Internship Report
Pakistan Oilfields Limited
Submitted By: Muneeb Ur Rahman
Department: Process
Chemical Engineering SCME NUST
Duration: July 2018

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Pakistan Oilfields Limited Internship Report
About the Report
This report will be aiming to give a detailed review of the industry in which I am currently doing
my internship, Pakistan Oilfields Limited. It will discuss the basic structure of the industry and
the way of operation through which it proceeds. The report will also explain the different unit
operations and the kinds of industrial processes which are taking place in an oil and gas
industry in general. A brief overview will be given about the interconnection of various units
and streams.
In the end, I would especially like to thank all the people in the Process department who were
of great help during my one month internship period at this place.It was indeed a very healthy
learning experience and I enjoyed it whilst my stay at the plant in Khaur, Attock.

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Acknowledgements
It takes a lot of dedication and struggle to prepare a report covering all the operational units
and compiling necessary information. I have tried my best to make this report look as simple as
possible for better clarification.
After Almighty Allah, I would really like to pay my gratitude to the people of process
department as this department was of my primary concern. They paved my way for a better
understanding of the basic aspects of industry.
They were also a source of constant support and provided all the necessary guidance needed
to prepare this report. Indeed, it couldn’t have been prepared properly without their help.
Some of them are,
Engr Faisal Sabir (Process)
Engr Talal Joiya (Process)
Engr Mudassir Mahmood (Process)
M. NaveedUllah (Process)
M. Waseem (Process)
M. Ali Raza (Process)
M. Rashid (Process)
Engr M Junaid (HSE)
M. Bilal (HSE)
M. Saeed (KCDF)

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POL: An Introduction
Pakistan Oilfields Limited (POL) is a leading oil and gas exploration and production company
listed on all the three stock exchanges of Pakistan. The Company’s prime focus is to deliver
performance through excellence in the field of exploration, drilling and production of crude oil
and gas.
Pakistan Oilfields Limited (POL), a subsidiary of The Attock Oil Company Limited (AOC), was
incorporated on November 25, 1950. AOC was founded in 1913 and made its first oil discovery
in 1915 at Khaur, District Attock. AOC has, therefore, pioneered exploration and production of
oil and gas in this region nearly a century ago. In 1978, POL took over the exploration and
production business of AOC. Since then, POL has been investing independently and in joint
venture with various exploration and production companies for the search of oil and gas in the
country.
In addition to exploration and production of oil and gas,POL also manufactures LPG, Solvent Oil
and Sulphur. POL markets LPG under its own brand named POLGAS as well as through its
subsidiary CAPGAS (Private) Limited. POL also operates a network of pipelines for
transportation of its own as well as other companies’ crude oil to Attock Refinery Limited.
In 2005, the Company acquired a 25% share in National Refinery Limited, which is the only
refining complex in the country producing fuel products as well as lube base oils.

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Organizational Departments
 Process (Plant)
 Electrical (Engineering)
 Mechanical (Engineering)
 Instrumentation
 Laboratories
 Admin & HR
 IT
 Audit
 Accounts

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Products of Organization
Natural Gas
Natural mixture of gaseous hydrocarbons found issuing from the ground or obtained from
specially driven wells. The composition of natural gas varies in different localities. Its chief
component, methane, usually makes up from 80% to 95%, and the balance is composed of
varying amounts of ethane, propane, butane and other hydrocarbon compounds. Because of its
flammability and high calorific value, natural gas is used extensively as an illuminant and a fuel.
Crude Oil
An oily, flammable liquid that occurs naturally in deposits, usually beneath the surface of the
earth; it is also called crude oil. It consists principally of a mixture of hydrocarbons, with traces of
various nitrogenous and Sulphurous compounds.
Little use other than as lamp fuel was made of petroleum until the development of the gasoline
engine and its application to automobiles, trucks, tractors, and airplanes. Today the world is
heavily dependent on petroleum for motive power, lubrication, fuel, dyes, drugs, and many
synthetics.
Sulphur

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Sulphur is found in group Via of the periodic table. Solid Sulphur occurs principally in three forms,
all of which are brittle, yellow in color, odorless, tasteless, and insoluble in water. It is a chemically
active element and forms many compounds, both by itself (sulfides) and in combination with
other elements. It is part of many organic compounds. Sulphur burns in air with a blue flame
forming Sulphur dioxide.
Liquid Petroleum Gas
LPG is a mixture of gases, chiefly propane and butane, produced commercially from petroleum
and stored under pressure to keep it in a liquid state. The boiling point of liquefied petroleum
gas varies from about -44°C to 0°C (-47°F to 32°F), so that the pressure required to liquefy it is
considerable and the containers for it must be of heavy steel. When prepared as fuel, LPG is
largely propane; common uses are for cooking and heating and lighting. It is also used for
powering automotive vehicles. LPG is an attractive fuel for internal-combustion engines because
it burns with little air pollution and little solid residue.
Solvent Oil
Solvent oil is one of the 5 major oil products closely related to people’s daily life. Its application
sectors also have a constant expansion. The variety with the greatest consumption is coating
solvent oil (usually called paint solvent oil). There are also extensive uses in cooking oil, printing
ink, leather, pesticide, insecticide, rubber, cosmetic, perfume, chemical polymerization, medical
and IC-component cleaning sectors.

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Abstract
The input for the plant here at Khaur is raw sour crude which is sent to three stage separation
process to be disengaged into sour gas, sour crude and water. After separation, Crude is
processed in stabilization unit where light hydrocarbons are removed and until their Reid Vapor
Pressure is maintained for storage purpose. Gas is then sweetened by sending it to Amine
Sweetening Unit where sour gases are removed. The glycol dehydration process removes water
vapors from the sweet gas coming from amine unit. This gas then meets the sales standard and
is stored and transported via pipelines to Meyal.

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Health safety and environment
In any environment the possibility of environment cannot be ignored. Accident occur due to
human mistakes. Safety means to prevent the hazard of accident.
There are two possible hazards in Khaur plant. Both are discussed with their important
characteristics and the methods to eliminate them.
They are
 H2S Gas Hazard
 Fire Hazard
H2S gas hazard
Hydrogen sulfide is extremely dangerous gas also called silent killer gas. It is color less and toxic
gas. It is an explosive gas. It is 1.189% heavier than air. Generally, it is found in oil and gas sector
and comes out with petroleum fluid during exploration.
Sources of H2S
 Oil and gas wells
 Gas plants
 Refineries
 Petrochemical plants
 Sulphur recovery plants
 Sewerage
 Underground mines

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Physical and Chemical Properties
 It is colorless gas
 It is odor is like rotten eggs
 It is acidic in nature
 It is soluble in water
 It is flammable
 It specific gravity is 1.189
 Its boiling point is -76F
 Its melting point is -116F
 Its ignition point is 500F
 Its lower explosive limit (LEL) is 4.3%
 Its higher explosive limit (HEL) is 46%
Monitoring and Measurement
Hydrogen sulfide concentration is measured by parts per million of air (PPM). According
to Occupational Safety and Health Administration (OSHA) USA, one can work 8 hours a
day safely in the presence of H2S.
Detection of H2S
For the detection of H2S, there are many methods such as
 Lead Acetate or Coated Strip
 Electronic Detector
 Installed System

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Fire hazard
The most common of the hazards but can be tackled with much less difficulty if properly trained
individuals are available. Fire is a chemical reaction between oxygen, fuel and heat. These three
elements should be present in a certain ratio for a fire to take place.
Cause of Fire
 Human Error (Carelessness)
 Sky lightening
 Dry grass
 Smoking
 Friction
 Static Charge
 Leakage
Classification of fire
Class of Fire Type of Fire Description
A Solid Solid material like wood
B Liquid Flammable liquid fuel
C Gas Gases like LPG
D Metal Metals and Appliances
E Electric Short circuiting

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Methods of fire Extinguishing
There are three mostly adopted methods of fire elimination. These are
Cooling
Removal of heat from the fire is called cooling method. For A class fire cooling method is used.
It can be done by showering water on burning material.
Smothering
For B class fire or fire from chemicals, smothering method is used. In which we remove the
oxygen from the fire place.
Starvation
For class C or fire from electricity, we use method of starvation. In this method we cut off the
fuel supply and then use CO2 gas as fire extinguisher.

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WORK PERMITS
For any job that needs to be done in the plant work permits are issued by the senior staff
members for coordination and safe execution of the job. The following types of work permits are
being issued.
a. Hot work permit
b. Tank / Vessel Entry Permit
c. Excavation and civil works
d. Cold work permit
e. Vehicle entry permit
f. Electrical work permit

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Pariwali Production Facility: An overview
Initially, raw sour crude extracted from the wells is directed towards different headers of the
plant which are classified according to their pressure. Then the
Following are the crude headers named after the wells from which they are extracted.
Well Pressure
Jhandial (HP well) 800
Pariwali 5 (HP well) 800
Pariwali 6 (MP well) 200
Crude
The line from Jhandial is sent to the new separators. On the other hand, Pariwali 6 contains a
lot of water and is therefore first treated in a knock out vessel. In that vessel, water is removed
and then crude air mixture is sent ahead.
The Pariwali 5 line goes to HP separator and from there, oil-water mixed stream goes to MP
separator after the separation of water. The line from Pariwali 6 also joins the output of MP
separator since it has medium pressure around 200 psi.
From here, the crude is first preheated via a heat exchanger and then sent to LP separator (with
pressure around 40-50 psi).

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Gas
10% sour gas separated from MP separator goes to M unit (LP compressor) and 90% goes to S/T
unit (MP compressor). In stabilizer, the lighter hydrocarbons along with the acid gases will leave
the stabilizer tower from top. This gas will go to M unit first and then to S/T unit where its
pressure will be increased to 800 psi.
In addition, gas from new LP separator goes to M unit, gas from new MP separator goes to S/T
unit and gas from HP separator joins the output of S/T unit.
All these new gases will go together in HP separator along with sour raw crude. The separated
sour gas from this separator then goes to amine sweetening unit followed by glycol dehydration
unit.

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Pariwali Production Facility
Raw, sour gas is processed into marketable oil and gas. To achieve this the following processes
are used:
a) Inlet separation
b) Oil stabilization
c) Amine sweetening
d) Glycol dehydration
Inlet Separation
 Separator is a pressure vessel used for separating a well stream into gaseous and liquid
components.
 Based on the vessel configurations, the oil/gas separators can be divided into three
categories.
a) Horizontal Separator
b) Vertical Separator
c) Spherical Separator
 In teams of fluids to be separated, the oil/gas separators can be grouped into
a) Gas/Liquid Two-Phase Separator
b) Oil/Gas/Water Three-Phase Separator.
 To meet process requirements, the oil/gas separators are normally designed in stages,
in which the first stage separator is used for preliminary phase separation, while the
second and third stage separator are applied for further treatment of each individual
phase (gas, oil and water). Depending on a specific application, oil/gas separators are
also called deliquilizer or degasser. The deliquilizers are used to remove dispersed

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droplets from a bulk gas stream; while the degassers are designed to remove
contaimined gas bubbles from the bulk liquid stream.
Separator Components
 Deflector Plates: They absorb the incoming momentum.
 Baffles: Are used to improve flow distribution.
 Separation enhancement device located in the primary separation (gravity settling)
section for major phase separation.
 Mist extraction: Are located in gas space to further reduce liquid content in the bulk gas
stream.
 Weir: To control the liquid level or interface level.
 Vortex breaker: To prevent gas carry under at outlet of liquid phase.
 Coalescing Plate: To separate the oil and water into distinct phase.
HP Separator
It is a horizontal three phase separator. The incoming raw stream enters this separator after
passing through ESDV (Emergency Shutdown Valve) and strikes a diverter plate. This collision
causes a momentum loss as plate absorbs the momentum and due to the sudden change in
direction of flow, gas separates from oil/water liquid stream. This liquid stream falls down and
passes through a coalescer mesh. This mesh provides some retention time for the oil/water
streams to separate. Oil being heavier than water, forms a layer on top of water which is
separated as it spills over a weir and goes into the oil draw off section. The level control valves
are used to send water to V-140 flash tank and oil to V-110 MP separator. The separated gas is
sent to amine unit after passing through a mist eliminator.

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MP Separator
A horizontal two phase separator which operates on about 20 psi pressure. Like the HP
separator, this separator also uses a diverter plate to separate the oil/gas mixture. The
oil/water streams go to LP separator after being preheated in a heat exchanger. The gas from
output of this separator goes mainly to S/T unit and little amount to M unit (10%).
LP Separator
It is again a three phase separator operating at low pressure (40-50 psi) which makes additional
gases separate from oil. Before entering this separator, crude is preheated using a heat
exchanger as it helps to separate three phases into their respective streams. From here, the
crude oil-gas mixture goes to stabilizer and water is returned back to flash drum. We are also
sending a little amount of gas along with crude to the stabilization unit. Without it, pressure of
crude is so low that it couldn’t have been pumped to the top of stabilizer.
Separator Type Operating Pressure
In psi
Design Pressure
In psi
Design Temperature
In 0C
HP 3 phase 780-800 1413 80-85
MP 2 phase 400 200-210 80-85
LP 3 phase 125 40-45 80-85

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Oil Stabilization
 Oil stabilization is done for two reasons
a) To remove light/volatile hydrocarbons that stabilize crude oil (helps to reduce
evaporation losses when it is stored and transported).
b) To remove acid gases
 This is obtained by two different processes occurring simultaneously.
a) Distillation: Since oil is a mixture of hydrocarbons, there is heating and partial
vaporization of oil so that lighter hydrocarbons are evaporated and the remaining are
stabilized.
b) Stripping: It is a process in which a gas stream removes dissolved gas components from
a liquid stream. For this purpose, fuel gas is used.
 The input crude oil (coming from V-130) enters the stabilizer tower from top. It is a non-
reflux distillation tower. The process of distillation occurs due to the heat provided by
the vapors entering the base of tower coming from the re-boiler.
 Some introduction is given here of the equipment employed in this unit.
Stabilizer
There are 14 trays installed. Oil flows downwards across the trays and two gas streams flow
upward. The rising hydrocarbon vapors partially vaporize the crude and fuel gas strips of the
acid gases. In valve trays, perforations are covered by lift-able caps. Vapor flow lifts the caps,
thus creating a flow area for the passage of vapor. The lifting cap directs the vapor to flow
horizontally into the liquid, thus providing better mixing. A level of crude is kept at each tray
over which the rising vapors go. The down-flowing sweet and stabilized oil is collected from
bottom of tower. Due to hydrocarbon vapors, the stabilizer has temperature gradient and
lower trays have higher temperature.

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Re-boiler
It is kettle type shell and tube heat exchanger. Heating medium is sun oil which is taken in tube
side, heats the crude coming from stabilizer unit V-600 in shell side below the tube bundle. A
shell side weir keeps the tube dip in oil. So that hydrocarbon vapor can be generated. Oil spills
over the weir and drawn off in oil section. The generated hydrocarbon vapors leave the shell of
re-boiler to feed the stabilizer unit with heated hydrocarbon gas.
Heat Exchanger
It is a shell and tube heat exchanger. In the tube side, there is sweet crude coming out of the re-
boiler and in shell side there is sour crude going from MP separator to LP separator. This has
two benefits:
a) Sweet crude is cooled which is important for storage
b) Sour crude going to LP separator gets heated because preheating results in better
separation.
Fin fan Cooler
It is a horizontal tube fin heat exchanger. After passing through heat preheater, stabilized crude
oil flows through tubes of cooler as it is cooled by a flow stream generated by a fan that passes
across finned surface of tubes. After this, crude oil is sent to storage tanks.

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Possible problems
Following problems can arise if flow rates of gas or liquid/oil are not steady.
Jet Flooding
High vapor rate is a condition of flooding where pressure drop increases which causes efficiency
to decrease. Flooding condition can be achieved by the excessive carryover of liquid to the next
tray. This kind of flooding is called entrainment or jet flooding.
Down Flooding
If liquid rate is high in this condition, down comer flooding can be achieved because the down
comer is not able to handle the high loading of liquid.
Weeping
A low vapor rate is the weeping condition. Weeping occurs when the vapor flow is insufficient
to maintain a level of liquid on the plate.

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Amine Sweetening
 It is a process in which acid gases are removed from the sour gas coming from HP
separator V-100. It is based on a reversible chemical reaction between acid gases and
weak organic bases known as alkanolamines. This reaction is referred to as
neutralization reaction.
 The amine used in this process is MDEA (Methyldiethanolamine) as it has a high
selectivity for H2S in presence of CO2 and doesn’t react with CO2 to form by-products.
Also, due to its efficiency, it requires less pumping and heat as compared to other
chemicals. We used 50% solution of MDEA in amine unit.
 The equipment employed in this unit is discussed below.
Filter Separator
It is a horizontal double barrel separator which mainly removes solid particles and hydrocarbon
droplets coming from separation unit to avoid amine forming. The incoming sour enters into
the upper barrel which is divided into two compartments. Here, solid contaminants and
entrained hydrocarbons are removed while liquid hydrocarbons are accumulated in lower
barrel. Then sour gas enters into second compartment in upper barrel. Here, it is passed
through a mist eliminator where remaining entrained hydrocarbons are removed and drained
to lower barrel.
Amine Contactor.
In amine contactor, the aqueous solution of amine absorbs and reacts with acidic gases to form
water soluble salt compounds. Here, amine is showered from top and sour gases flow in

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counter current flow from bottom to top. Amine becomes richer as it flows downwards and gas
become sweeter as it rises upwards.
It is a vertically mounted tower with 20 valve trays installed in it. At each tray, rising gas blows
open the tray’s valve plates by pressure. Flow rate of lean amine is kept 30 GPM. A weir on
each plate maintains the level of amine liquid. High Pressure of about 800 psi and low
temperature around 50-55 0F is favorable for this absorption phenomena.
Sweet Gas Scrubber
It is a vertical separator used to remove entrained amine mist. It is valuable as it plays an
important part in reducing the amine losses.
Rich Amine Flash Tank
The flash tank is vertical two phase separator. Using gravity and retention time, this separator
operates at low pressure to remove sour hydrocarbon vapors from rich amine. It prevents the
foaming formation and amine losses. It reduces pressure from 800 to 80 psi.
Rich Amine Heat Exchanger
Rich amine from flash tank is passed through plate and frame type heat exchanger. This heat
exchanger has two tasks.
a) To warm rich amine from contactor to prepare it for regeneration.
b) To cool lean amine from re-boiler to prepare it for absorption.

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Amine Regenerator
In this unit, amine is regenerated at low pressure and high temperature. It is a stripping tower
with three internal packing beds. Rich amine falls downwards while steam strips the acid gases
from the falling amine. In this tower, random packing is used instead of valve trays to maximize
the contact time between rich amine and stream. Specially shaped metal rings are used. The
steam’s heating breaks down the water soluble salts into acid gases and amine. The streams
then strip the acid gases from amine. Above the rich amine inlet, there is a packing bed where
any amine vaporized in lower beds is condensed by reflux liquid entering from top of tower.
This helps in amine recovery.
Amine Re-boiler
It is a kettle type heat exchanger. Tube side heating medium is Texatherm 46 (highly refined
mineral oil C-15 to C-50). Lean amine is circulated on shell side which is heated from the
heating medium. Heating of aqueous lean amine vaporizes some of the water into the steam
which is fed to the amine regenerator for stripping purpose. A weir is used to control the level
of lean amine in the re-boiler and remaining is drawn off to the amine tank through plate and
frame heat exchanger.
Lean Amine Accumulator
It has aqueous solution of amine that contain 50% water and 50% MDEA. The tank is filled by
aqueous solution of amine by 44% volume of tank. It then passes to the fin fan cooler,
particulate filter and carbon filter.

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Amine Carbon Filter
The carbon filter removed the dissolved hydrocarbon from the lean amine using porous
charcoal elements. It is important because it cause foaming problem in amine tower.
Chemical Injection Pump
Pumps are pair of plunger pump. These pumps inject a MAX AMINE 70B as antifoaming agent, if
foaming starts in the amine unit.

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Glycol Dehydration Unit
 Glycol dehydration is a water removal process based on the physical absorption of
water vapor. The physical absorption take place at high pressure and low temperature
in the glycol unit. The glycol dehydration process uses triethyleneglycol (TEG). This is
because of the following reasons:
a) It has high thermal stability.
b) It is efficiently regenerated high glycol concentration because of large boiling point
difference.
c) It has low vaporization losses.
 The glycol dehydration process removes water vapors from the sweet gas coming from
amine unit. Removing of water contents from sweet gas is necessary to meet the sale
specifications. Excessive water contents lead to corrosion in pipes and hydrate
formation.
The units installed in this section are discussed below:
Glycol Contactor
An absorption column where sweet gas coming from amine unit gets dehydrated by contacting
lean glycol. It has 9 bubble cap trays. Glycol is showered from top and absorbs moisture from
uprising gas. A bubble cap tray has a riser or chimney fitted over each hole and a cap that
covers the riser. Vapor rises through the chimney and is directed downward by the cap, finally
discharging through the slots in the cap and bubbling through the liquid on the tray.
The glycol becomes richer as it flows down and gas becomes dryer as it rises through the
bubble cap trays. Glycol foaming is a problem that may occur if solids and hydrocarbons are
present in large quantity. If too much gas or too much glycol are introduced in the tower, then
glycol carryover or flooding respectively can be the result.

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Flash Tank
It is a horizontal two phase separator. The rich glycol from the contactor enters the flash tank
and strikes a diverter plate to remove hydrocarbon gas. These gases pass through mist
eliminator to remove any glycol droplets. In flash tanks, cooling is produced as a result of
pressure drop. As a result, hydrocarbon layer forms over glycol that can then be drained
through its respective valve to avoid foaming.
Glycol Particulate Filters
Two particle filters have been installed of cartridge type that remove solid contaminants from
rich glycol coming from flash tank. This helps to reduce foaming and possible wears of pumps
and other equipment. As glycol passes through filter elements, it traps solid particles while
glycol passes through.
Glycol Carbon Filters
Carbon filters remove hydrocarbons from rich glycol using porous carbon /charcoal. If filter
doesn’t produce desired quantity of hydrocarbon free glycol, then we know that filters need to
be replaced. Unlike particle filters, DP indicators can’t indicate whether filters need to be
changed or not.
Heat Exchanger
It is a plate and frame type heat exchanger. Rich glycol after preheating at reflux coils enters
the heat exchanger for further heating. It absorbs heat from lean glycol coming from the re-
boiler and hence lean glycol cools down as required for storage. There is cross flow between
the two streams.

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Re-boiler and Regenerator
The regenerator consists of a bed of metallic packing. Rich glycol is showered above the packing
by means of a sparger. Steam enters the bottom of packing from the re-boiler and moves in
upward direction. The steam vaporizes and strips the absorbed water from glycol. This rising
stream is condensed by reflux coil above the packing and thus glycol vapors drain down
towards re-boiler as a reflux. This reduces the glycol losses. The showered rich glycol goes
below the re-boiler. Now this has become partially lean glycol. The remaining water is removed
by exchanging heat with the hot oil moving in the coils. Here, after passing through a weir, the
lean glycol goes to Stahl column.
Stahl Column
The Stahl column is a mini stripper tower that removes remaining water vapors from glycol by
using fuel gas as a stripper gas. Lean glycol from the re-boiler spills over the top of packing in
the tower as rising fuel gas removes vapors from it and goes through re-boiler to vent stack.
The fuel gas first passes through a pipe in the re-boiler to get warm and then enters the column
from the bottom. After Stahl Column, concentrated glycol goes through heat exchanger to get
cooled and then is transported to glycol accumulator.
Glycol Air Cooler
There are 6 parallel tube fin coolers under the accumulator that are used to cool glycol with
atmospheric air once glycol leaves the tank. Cooling helps to reduce operating temperatures of
the two PD pumps, thus increasing their durability.

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Plant Utility
 Plant utilities are additional supporting equipment or systems which are not directly
involved in the processes but are beneficial and necessary for proper functioning of the
industry. In chemical process plants, plant utilities play an important role in supporting
the operation of the facility.
 Following is a brief overview of the main utilities in Pariwali Production Facility:
a) Heat Medium System
b) Instrument Air System
c) Fuel Gas System
Heat Medium System
In this system, the medium for heat transfer is a thermal oil which is being heated in a boiler
after which the pumps circulate it through the system. The heat from this oil is needed by the
re-boilers to produce stripping streams in the associated towers. Given below is a brief
overview of the equipment employed in the functioning of this system.
Heat Medium Boiler
This boiler, indicated by H-880, is a direct fired heater. In this heater, a forced draft of air
generated by a fan combines with fuel gas in the burner chamber and extends into the boiler
lined with refractory bricks. Here, thermal oil is present in a coil spiral which is heated by the
hot fuel gas after which the stack of combustion gases is discharged to the atmosphere.

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Heat Medium Surge Drum
This surge drum is a horizontal tank which provides a storage volume for the thermal oil given
that it expands with heat. A fuel gas may be inserted into this drum to act as a blanket thus
preventing oxygen from entering and avoiding any possibility of
a. Oil combustion
b. Formation of oil or oxygen degradation products
Heat Medium Pumps
Two centrifugal pumps in parallel are installed upstream of the heat medium boiler. These
pumps draw thermal oil from the re-boilers and direct it towards heat medium boiler, labelled
H-880.
System Applications
From the re-boiler, the hot oil branches in two lines
a. One flow enters the tube side of the glycol re-boiler.
b. The other flow enters into two feeder pipes from which hot oil goes into tube
side of the amine and stabilizer re-boiler.

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Instrument Air System
This system provides air to pneumatic transmitters, controllers, control valves and
pneumatically powered diaphragm pumps. This air must be dust free, moisture free and be
available at required pressure.Given below is a brief overview of the equipment employed in
the functioning of this system.
Air Compressors
These compressors are two stage, reciprocating and belt driven that supply air for the
instrument air system. Each of these compressors is mounted on top of wet air receivers. Air
coolers and filters are installed inside these compressors. These have a maximum discharge
capacity of 200 psi and run alternatively in a lead-lag manner.
Air Dryers
Since the compressors increase relative humidity of air, dryers are installed to remove excessive
moisture from the air so that it doesn’t condense in piping or actuators. This dryer is a dual
chamber, unheated and regenerated equipment containing a desiccant that adsorbs
contaminants from the air passing through it. Pre and after filters are installed for dryer to
prevent desiccant from contamination and to avoid plugging by dry desiccant dust respectively.
These filters operate alternatively, at any time, one is the drying desiccant chamber while other
is the reactivating desiccant chamber.
Air Receivers/Vessels
These horizontal receivers, V-810, provide 240 gallons of storage for the wet compressed air
flowing from the compressors and also serve as the base frame for supporting the compressors.

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Fuel Gas System
A slipstream of sweetened and dehydrated sales quality gas is withdrawn downstream of the
sales gas separator in the glycol dehydration process. This slipstream of gas then passes
through pressure regulators, after which it flows through scrubber for removal of entrained
liquids and then enters the piping which distributes gas where it is required. This gas is referred
to as fuel/purge/stripping gas.
Fuel Gas Scrubber
The scrubber used here is a vertical separator which uses an internal filter core to coalesce
entrained mist from the gas. Removing entrained liquid is essential for stable combustion
operation of burners and pilot flames. Details of this scrubber is provided in the glycol section
of this report.
Fuel Gas Distribution Piping
From the scrubber, the fuel gas flow branches into a distribution header on this skid and a fuel
gas supply to the headers on other skids including LP,MP and HP separator skids, heat medium
system skid and to skids of amine, glycol and stabilizer unit.
System Applications
This gas is employed in the following applications
 Firing the heat medium boilers
 Feeding the LP and HP flare stack
 Providing a gas blanket in vapor space of storage/surge vessels

33
 Acting as a purge gas to displace air from process vessels during startup procedures
 Serving as a stripping gas in the Stahl column of glycol unit and in the stabilizer unit
Flare System:
The flare system gathered wastes gases and liquids discharged by safety/relief valves and blow
down valves. Liquid and gases are separated, liquids are pumped away while gases are burned
at the flare stack.
The plant is equipped with two flare systems.
Low Pressure Flare:
Low pressure flare system handles flow from safety relief valves which open at set pressure
below 75 psig.
High Pressure Flare:
Low pressure flare system handles flow from safety relief valves which open at set pressure
above 75 psig.
Flare knock out drum:
It is a horizontal two-phase separator. Using gravity and retention time, this knock out vessel
separate the gas from the incoming liquid.

34
Khaur Crude Oil Decanting Facility
An Introduction
Crude oil received in truck lorries sent by different companies e.g. NASHPA, OGDCL, MOL
etc. from different oil fields is decanted at a decanting facility in Khaur established by POL.
The main reason for decanting these truck lorries in Khaur and not sending them directly
to the refinery in Rawalpindi is that is it’s a huge hazard. The population of Rawalpindi has
increased drastically over the years and to carry such tremendously huge amounts of
crude oil in the city can be a threat. So for this reason, POL pumps the crude oil through
pipeline to Rawalpindi.
The decanting facility receives sour and sweet kind of crude oil. These are pumped
separately throughout and stored separately as well. Following is the process which
explains the whole working of the KCDF.
Decanting Station
The truck lorries received at the gate are first weighed on a weighing bridge. They are
given a decanting point number station at which they are to be decanted according to the
quality of their crude oil i.e. sweet or sour. The operator present at the station measures
the specific gravity of the oil received, its temperature and dip of the tanker. If all the
things match the specifications he has received, he then starts to decant the lorry. On
average, it takes about 90 minutes to decant one lorry.
The crude oil received is transferred to surge tanks via pipelines. There are no motors
present to pump the oil to the surge tanks, it flows due to gravity. The oil received in the

35
surge tanks (in total 6 with a capacity of 452 US barrels each) is then pumped by
centrifugal decanting pumps to the tanks. There are in total 9 tanks with different
capacities. Different tanks store oil received from different fields due the different nature
of the oil.
Coming back to the tank lorries, when the lorry is fully decanted, it then goes to the left
over point, where the it passes over few jumps and shakes while the operator opens the
valve to collect the left over crude inside the lorry and then this crude is also added to the
pipe line. Then the lorry goes back to the weighing bridge, where it is again weighed, the
weight before and after the decanting process is compared and the net-weight of the
company which sent the lorry for decanting. If the readings match, the lorry is allowed to
leave otherwise not.
Tank Number Crude Oil Location
1,7,9 KCDF
2,3 Local well, Pariwali
4,8 Jhandial
5 Dhulian, Meyal
6 Local, POL mix
Pumping
There are 26 pumps in total at this facility. Out of these, 8 are used for decanting in which 6 are
for sweet and 2 for sour crude. 9 pumps are booster pumps that act to give pressure to crude
for metering purpose and also give some head to main pumps which reduces their load. After
booster pumps, there are metering pumps to determine number of barrels being pumped or to

36
show how much amount is being sent to ARL. Then there are 9 main pumps out of which 4 are
PD pumps (multistage plunger pumps) and 5 are multistage centrifugal pumps. These are used
to pump crude to ARL.
Main pumps include plunger pumps and centrifugal pumps which are VFD controlled and
can be operated from with inside the control room. Plunger pumps are used for increasing
the pressure in the line while centrifugal pumps are used for flowrate. All the pumps can
be controlled from the control room, but only main pumps are VFD controlled. The crude
that the booster pump sucks from the tanks, travels through smith meters which record
the flow of the crude and generate a report accordingly. By this metering, the company
obtains the number of barrels being pumped daily to Rawalpindi.
The company pumps its own crude which it receives from the PPF plant and other fields
as well. Almost 25000 barrels is decanted daily and pumped as well. Not more than three
main pumps are operational at a single time. If more pumps need to be operated, special
permission is needed from the power house as they have to start another engine to
distribute the load equally within the safe limit. All this can be observed on the controller’s
computer on a software.

37
THE END
Contact: muneebrahman27@yahoo.com

Pakistan Oilfields Limted (POL) Internship Report

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