Majid Report

8/6/2019 Majid Report

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Submitted To: Malik Yousaf

Assistant Manager (HBU)

Submitted By: MAJID SHAH


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INTRODUCTION:Attock Refinery Limited (ARL) was incorporated as a Private Limited Company in

November, 1978 to take over the business of the Attock Oil Company Limited (AOC)relating to refining of crude oil and supplying of refined petroleum products. It wassubsequently converted into a Public Limited Company in June 1979 and is listed onthe three Stock Exchanges of the country. The Company is also registered with CentralDepository Company of Pakistan Limited (CDC).

Original paid-up capital of the Company was Rs 80 million that was subscribed by theholding company i.e. AOC, Government of Pakistan, investment companies andgeneral public. The present paid-up capital of the Company is Rs 454.896 million.

ARL is the pioneer of crude oil refining in the country with its operations dating back to

1922. Backed by a rich experience of more than 80 years of successful operations,ARLs plants have been gradually upgraded/replaced with state-of-the-art hardware toremain competitive and meet new challenges and requirements.

It all began in February 1922, when two small stills of 2,500 barrel per day (bpd) cameon stream at Morgah following the first discovery of oil at Khaur where drilling startedon January 22, 1915 and at very shallow depth of 223 feet 5,000 barrels of oil flowed.After discovery of oil in Dhulian in 1937, the Refinery was expanded in late thirties andearly forties. A 5,500 bpd Lummus Two-Stage-Distillation Unit, a Dubbs ThermalCracker, Lubricating Oil Refinery and Wax Purification facility and the Edeleanu SolventExtraction unit for smoke-point correction of Kerosene were added.

SERIES OF FIRST:First refinery of the region (1922)First to start dispensing major products through pipeline using computerized meteringsystem (1987)First to produce low sulfur furnace (less than 1%) (1998)First to produce low sulfur diesel (less than 0.5%) (1998)First to achieve ISO 9002 certification for quality control laboratory (1999)First to produce low lead premium gasoline direct from refinery process (1999)First to produce polymer modified asphalt (2001)

First refinery/first petro-chemical plant / first major industry to get ISO 9001:2000certificate (2001)First refinery / first petrochemical plant/first major industry to get ISO 14001 certificate(2002)First major industry to get OHSAS 18001 certification (2006).


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There were subsequent discoveries of oil at Meyal and Toot (1968). Reservoir studiesduring the period 1970-78 further indicated high potential for crude oil production ofaround 20,000 bpd.

In 1981, the capacity of Refinery was increased by the addition of two distillation

units (HBU-1 & HBU-2) of 20,000 and 5,000 bpd capacity, respectively. Four yearsago with the erection of New Preheat Train at HBU-1 its capacity has beenincreased to 23,000 bpd.

Due to their vintage, the old units for lube/wax production, as well as Edeleanu, wereclosed down in 1986. In 1999, ARL commenced JP-1 pipeline dispatches, and in 2000,a Captive Power Plant with installed capacity of 7.5 Megawatt was commissioned.Another expansion and upgradation project was completed in 1999 with the installationof a Heavy Crude Unit of 10,000 bpd and a Catalytic Reformer of 5,000 bpd. ARLscurrent nameplate capacity stands at 45,000 bpd and it possesses the capability toprocess lightest to heaviest (10-65 API) crudes.

HBU CURRENT PROJECTS:Currently the working is in progress for the Distributive Control System (DCS) which willenable the smooth and more efficient operation of both the Plants. At first DCS will beinstalled at HBU-II in mid September 2007 and after that at HBU-II.A new Heater has already been procured and it will be installed at HBU-II after whichits capacity will be increased to 6000 bpd. The existing Heater H-101 at HBU-II canalso be remain in use at HBU-I, so that its capacity can be increased to 28,000 bpd.


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PROCESS DESCRIPTION

Composition of Crude:Crude oil is the term for "unprocessed" oil, the stuff that comes out of the ground.Crude oils vary in color, from clear to tar-black, and in viscosity, from liquid to almostsolid.

Crude oils are such a useful starting point for so many different substances becausethey contain hydrocarbons. Hydrocarbons are molecules that contain hydrogen andcarbon and come in various lengths and structures, from straight chains to branchingchains to rings.

The major classes ofhydrocarbons in crude oils include:

ParaffinsGeneral formula: CnH2n+2 (n is a whole number, usually from 1 to 20) straight- or

branched-chain molecules.Can be gasses or liquids at room temperature depending upon the molecule.Examples are methane, ethane, propane, butane, isobutane, pentane, and hexane.

Aromatics

General formula: C6H5 - Y (Y is a longer, straight molecule that connects to thebenzene ring).Ringed structures with one or more rings. Rings contain six carbon atoms, with

alternating double and single bonds between the carbons.Typically liquids.Examples are benzene, napthalene.

Napthenes or CycloalkanesGeneral formula: CnH2n (n is a whole number usually from 1 to 20).Ringed structures with one or more rings. Rings contain only single bonds between the

carbon atoms.

Typically liquids at room temperature.Examples are cyclohexane, methyl cyclopentane.

OTHER HYDROCARBONS:

AlkenesGeneral formula: CnH2n (n is a whole number, usually from 1 to 20).


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Linear or branched chain molecules containing one carbon-carbon double bond.Can be liquid or gas.

Examples are ethylene, butene, isobutene.

Dienes and Alkynes

General formula: CnH2n-2 (n is a whole number, usually from 1 to 20). Linear or branched chain molecules containing two carbon-carbon double bonds.

Can be liquid or gas.

Examples are acetylene, butadienes.

On average, crude oils are made of the following elements orcompounds:

Carbon - 84%Hydrogen - 14%

Sulfur- 1 to 3% (hydrogen sulfide, sulfides, disulfides, elemental sulfur)Nitrogen - less than 1% (basic compounds with amine groups)Oxygen - less than 1% (found in organic compounds such as carbon dioxide, phenols,ketones, carboxylic acids)Metals - less than 1% (nickel, iron, vanadium, copper, arsenic)Salts - less than 1% (sodium chloride, magnesium chloride, calcium chloride)

TYPES OF CRUDE:

Although Crude can be classified in a number of ways but its main

classification is on the basis of specific gravity.

Light crudes having Sp.Gr. in the range of 0.790 to 0.840.

Heavy crude having Sp.Gr. in the range of 0.840 to 0.910

Light crudes are further classified into two main kinds:

Light sweet crude having sulfur content less than 5ppm (0.5%).

BASIC TERMINOLOGIES:

Distillation:Distillation is the separation of the components by means of their boiling point achievedthrough the contact between the rising vapors and down flowing liquid. In general theprimary overall operating variables of a crude unit besides the feed characteristics aretemperature, pressure and flow rates.


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Specific gravity:It is the ratio of the density of substance to the density of reference material. For theliquids the reference is water and for gases it is air.

Specific gravity = density of productdensity of water

Flash point:The flash point of liquid fuel is the temperature at which oil begins to evolve vapors insufficient quantity to form an explosive or flammable mixture with air.

Fire Point:The lowest temperature at which the oil ignites and continues to burn for five seconds.

Pour point:The pour point of fuel is defined as the lowest temperature at which the oil will flow orpour. The pour point is important in design of heating jackets.

Reid vapor pressure:Reid vapor pressure is approximately the vapor pressure of the gasoline at 100 oF (38oC) in absolute units. Reid vapor pressure at laboratory is determined for non-viscousproducts such as gasoline, LPG. This test is important with respect to safety intransport, vapor lock in gasoline feed systems, types of storage tanks employed andthe starting characteristics of motor fuels.

Color:The color of distilled petroleum product indicates the degree of refining that materialhas undergone. Distilled products that are discolored are indication of thermaldecomposition. At ARL in quality control laboratory routine color tests are taken ofheavy and light gas oil, and test report indicates products properties.

Cetane number:Cetane number is actually a measure of a fuel's ignition delay; the time period betweenthe start of injection and start of combustion (ignition) of the fuel. In a particular dieselengine, higher cetane fuels will have shorter ignition delay periods than lower cetane

fuels.

Crude Flow at HBU:This plant is designed to process Light Sweet Crude having specific gravity in the range0.790-0.810 and sulfur content less than 5ppm (


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crude. It is drained once in every shift. Then crude passes through strainer having amesh, which retains the more minute particles. It is cleaned on weekly basis and duringwinter steam is applied around it to avoid choking of the strainer. Then crude passesthrough birotormeter for flow measurement and into the suction of Crude Charge pumpP-301 A/B. Crude then enters into the suction of crude charge pump P-301 A/B having

discharge pressure upto 1500-1650 Kpa. This pump provides the necessary headrequired to move the crude through the crude oil charge system. The crude oil is thenpumped through heat exchangers installed in series E-301, E302, E-303A/Bof the oldpre-heat train where it exchanges heat with kerosene, cold light gas oil, and naphthapump around respectively and similarly of the new pre-heat train exchangers E-321, E-322, E-325, and E-326. Then both streams of crude combine and enters into Desalter,V-306, which is operated at 91-100 oC .

Desalter water flows into the suction of the Desalter water pump P-310 A/B. This pumpprovides the necessary head required to move the Desalter water through heatexchangerE-314 and into crude oil stream. Water is added about 3%of crude charge

by volume and it is mixed with oil in mixing valve with a pressure drop of5-15 psi. InDesalter water droplets are electrostatically coalesced and collected water exits thevessel on level control, which is controlled by controller LCV-301. Desalter effluentwater gives the heat in heat exchangerE-314 to Desalter water feed. Desalter is designto remove salt of capacity 16-kg/159 m3 (35lb/1000bbl)of crude oil. Desalter ismaintained at hydraulic pressure of 1000 KPa to prevent possible vaporization byCascade controller PIC-401 on crude charge stream. PIC-401 is master controllerwhose slaves are FCV-134 and FCV-137.PIC-401 output is the set point for the FCV-134 and FCV-137. Water molecules along with salts combine with each other and theycoalesce bringing salts with them and settle to the bottom of the desalter due to gravity.In the normal roundup of the plant tricock levels are checked, mixing valve delta P is

noted and effluent water color is observed.

Crude charge is then further heated by heat exchange with LGO, cold residue, hotHSD, HSD pumparound, and hot residue in heat exchangers connected series E-304,E-305, E-306, E-307B, E-07A and E-308 respectively of old preheat train and similarlyin new pre heat train by E-324, E-318, E-317, E-327, E-328 and E-329. At this point arecirculating residue joins the fresh crude charge stream on flow control. This is addedto maintain a satisfactory flow of liquid at heater outlet and prevent excessivevaporization and possible tube cocking. About 10 15 % of fresh crude charge ofrecirculating residue is added. The function of this recycle stream is

To maintain satisfactory flow in the heater Prevent excessive vaporization

and prevent possible tube coking

Improve heater inlet, hence reducing heater duty.

Before entry into the convection section of the heater crude is divided into four passes.In the convection section there are 56 finned tubes. Here crude receives heat from theflue gases and finned tubes are used to increase contact time and heat transfer rate.


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Then pass # 1 and pass# 4 travels to the radiation section of the heater and leave fromthe middle of the radiation section. Pass # 2 and pass # 3 enter from the middle of theradiation section and leave from the bottom of the radiation section. Last seven tubesof each pass in the radiation section are of 5 inches while rest are of 4 inches. Total noof tubes in the radiation section are 88.

H-301 is rectangular furnace which operates on natural draft. Different fuel options areprovided on H-301 where L.P gas, Field gas and F.F.O can be burnt in the nineburners. Tube strength of the tubes is up to 865 oF. To maintain this temperaturerequires a lot of skill on the part of the operator.

Operator usually observes the following things:

Excess oxygen

Draft at different location of the heater like top and bottom draft

Stack temperatures.

Skin temperatures

Physically flame color, length and direction should be closely monitored. In the crudecircuit inbuilt safeties are also provided. All flow control valves like FCV-103, FCV-138,FCV-137, FCV-134 are (air to close) Fail open so that in the failure of instrument aircrude keeps on traveling in the heater tubes and exchangers. Also 7 PSV,S areinstalled at different locations of the crude circuit. Heater H-301 is also provided withthe 3 FSV,S whose tripping conditions are:

Low crude charge 5000 bpd.

Low gas header pressure (14 kpa).

High heated transfer temperature (369 degree centigrade).

Instrument air failure. Electricity failure.

Four passes of the heater combine into the common header where pressure is usually150 KPa .Then crude enters into the flash zone of the towerV-301.

Naphtha & Light Gases Flow:Crude tower over head vapor passes through overhead condenserE-309 by which it istotally condensed. The condensed liquid plus any non-condensable vapor flow into theoverhead accumulatorV-305. Sufficient pressure is maintained on this accumulator sothat essentially all vapors will be condensed but not so high as to impose high flashzone pressure. It is maintained between 100-110 KPa. Non condensable vapors arethen vented through a split ranged pressure control system to the off gas knock outdrum. Steam coils are provided in the knock out drum to vaporize any condensedliquid.


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A controlled stream of naphtha is withdrawn from tray no.37 as pumparound andpassed through heat exchangerE-303A/B and fed back to the tower along withreflux stream on flow control system.

Part of unstabilized naphtha separated from V-305 is pumped by P-302 A/B to the top

plate of tower as reflux. The reflux rate is reset by crude tower's overhead vaportemperature with control system. A level control system over the accumulator resetsthe stabilizer feed flow. The remaining unstabilized naphtha is then pumped by P-303A/B to stabilizerV-401 through flow control system and heat exchanger E-401 A/B. Itenters the stabilizer on plate no.22. In this tower essentially all of the ethane andpropane and sufficient butane are fractionated from naphtha. Overhead vapor flowsthrough the condenser E-402 in which vapors are condensed. A part of liquid isreturned to the stabilizer to provide adequate reflux by pump P-401 A/B through levelcontrol system. Other liquid is taken as LPG product, which is sent to the LPG treatingsection. Naphtha flows from the bottom of the stabilizer into the stabilizer reboilerE-403to maintain a constant reboiler vapor return temperature to reboiler. The stabilized

naphtha flows from reboiler to heat exchangerE-401, and to naphtha coolerE-404, andto trim coolerE-405 prior to passing through the battery limits on level control system. Ifpressure of the column increases following action can be performed:

Increase the speed of fans

Flaring optionTower top temperature increaseCrude charge reduction

Kerosene, HSD and DFO Flow:Kerosene, light gas oil and heavy gas oil are withdrawn from crude towerV-301 as side

cuts and admitted to strippers V-302, V-303 and V-304 respectively, on level controlsystem where these products are steam stripped for flash point correction. Low boilingpoint vapors along with steam are sent back to crude column to maintain temperatureof column.

The kerosene is withdrawn from the main tower as a side cut. This stream is admittedto the kerosene stripper V-302 on level control. The kerosene is steam stripped forflash point correction. Kerosene product flows through the suction of the keroseneproduct pump P-304 A/B, from which it is pumped through the kerosene-crudeexchangers E-301, E-321 and the kerosene cooler E-310 prior to exiting the unit onflow control.

Light gas oil is withdrawn from the main towerV-301 as a side cut and is admitted tothe light gas oil stripperV-303 on a level control. The purpose of stream stripping is theflash point correction. Light gas oil product flows into the suction of the light gas oilproduct pump P-305A/B from which it is pumped through the hot LGO exchangers E-306 and E-317 and the cold LGO-crude exchangerE-302 & E-322 and the light gas oiloverhead CondenserE-311 prior to exiting on flow control.


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Part of light gas oil withdrawn from the main tower is taken to the light gas oilpumparound pump P-307A/B rather than to the light gas oil stripper. This stream iscirculated as the pumparound stream supplying all the heat required by the stabilizerreboilerE-403 and allowing the high level of heat recovery in the crude preheat train bybeing circulated through light gas oil -crude exchanger E-307A/B. The combined

pumparound streams return to the main tower on tray no.18

Heavy gas oil withdrawn from the crude tower V-301 as a side cut is admitted to theheavy gas oil stripperV-304 on level control. The heavy gas oil is steam stripped forflash point correction. Heavy gas oil product flows into the suction of heavy gas oilpump P306A/B from which it is pumped through the heavy gas oil -crude exchangersE-304, E-324 and the heavy gas oil coolerE-312 prior to exiting the unit on flow control.

Residue Flow (FFO):The portion of the crude tower charge which is not vaporized plus the condensedoverflashed material flows downward from the crude tower flash zone across the four

stripping trays. Steam is admitted below the bottom tray for flash point correction of theresidue. Crude tower bottom flows into the suction of the atmospheric residue pump P-308A/B. This pimp provide the necessary head required to move the residue.

Recycle stream through its flow control station and into the convection section of thecharge heater and also to move the residue product through the hot residue -crudeexchangers E-308, E-329, the cold residue-crude exchangerE-305, E-318, the residueoverhead Condenser E-313 and into the suction of the atmospheric residue boosterpump P-308C/D. This pump provide the necessary head required to move the residueproduct stream through the level control station (controlling the crude tower bottomlevel) and onto the plant battery limit.

LPG TREATMENT SECTION

LPG from discharge of stabilizer reflux pump P-401 A/B flows into the suction of theLPG booster pump P-501 A/B. The booster pump provides the necessary headrequired to move LPG through LPG cooler E-501, The LPG flow control system FCV-113, the first stage caustic wash V-501 and its mix valve, The second stage causticwash V-502 and its mix valve, the water wash V-503 and its mix valve, the salt drierV-504, and on the battery limits at 120 psig and 100 oF.

The two stage caustic wash system enhances the hydrogen sulfide removal efficiencyand reduces caustic consumption to a minimum. Make up caustic is admitted to thesecond stage by means of a dosing (metering) pump. Since the hydrogen sulfide levelin the LPG coming to second stage is greatly reduced, the caustic in the second stageis less spent than in the first stage. Excess partially spent caustic is taken from thesecond stage on level control and routed to first stage, where caustic basicallybecomes totally spent. Spent caustic exits the first stage on level control and is routedto disposal. A caustic recycle system is provided on each stage in order to increase the


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volume of caustic in contact with LPG and enhance contact efficiency. At each causticwash stage and water wash stage mixing is accomplished by means of mix valve.

LPG exits the second stage caustic wash and flows to water wash for trace causticremoval. A small quantity of fresh water is admitted by means of a metering pump and

water is withdrawn form the water wash vessel on level control. Again a recycle systemis employed to ensure adequate contact.

LPG flows to the on-line salt drier where all free water is removed periodically. Saltbrine is drained from the bottom of the vessel. Adequate depth has been provided sothat salt needs not to be added more frequently than six months to one year. At thistime the LPG stream is transferred to the stand by drier and salt is added to thepreviously on-line drier. A backpressure control valve maintains constant pressure onthe system.

An adequate caustic dilution tank has been provided so that caustic dilution and mixing

can be achieved. Steam is supplied to this tank to increase the temperature and Air isalso used for proper mixing the solution.

Shut down of the Plant:

Following are the main points of shutting down the plant:Perform soot blowing of the convection section of the heater and inform boiler house,

OMI, HSE regarding shut down.Reduce crude charge at a specific rate, for NDU-I reduction is 2000 bbl/hr and for

NDU-II this reduction is 500 bbl/hr. Meanwhile when reduction is done we reduce

the products flow accordingly so as to maintain their draw off temperatures andkeep them on spec.

After crude is reduced to 12000 bbl NDU-I and 2000 bbl for NDU-II, reduce transfertemperature @ 150 oF/hr, meanwhile bypass stabilizer section and desalter section,cut off grade products to slop except residue and petrol to avoid any hazardoussituation, shut amine injection pumps.

At transfer temperature 300 oF shut heater, close louvers and open dampers and openpurging steam to heater for half an hour.

Then at transfer temperature 250 oF shut pumping system of the unit and close heaterinlet chain valve and open heater to tower steam for 5 hrs, also open steam throughstrippers.

Now start steaming out products circuits to slop.Steaming out should be done very efficiently so that all the crude should be pushed

and drained from the system.Drain water from the nearest point to check for any oilThen insert blinds at specific locations of east and West Side battery limit of the plant.Hand over unit to PM-I for maintenance.

Start up of the plant:


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Start up of the plant is done as follows:Steam out of the plant to remove airFloat field gas to avoid re-entry of air in the linesUse soap solution to check for any leakage

Fill crude in the crude circuit up to tower bottom ( Cold circulation) Drain water after giving it a settling time at the bottom of the tower.

Then close louvers, open dampers and start purging steam to create draft in theheater, now lit all the pilot burners and one main gas burner ( Hot circulation)

Now increase transfer temperature gradually @ 150 oF.

Increasing of temperature should be done in such a way that heater inlet shouldalso increase.

Then at transfer temperature 450 oF send residue sample to lab for sp.gr and flashpt test.

If sample is on spec start fresh crude charge, lit all the burners of the heater, cut off

grade products to slop and start amine injection pumps At desalter inlet temperature 50 oC switch on desalter.

Maintain transfer temperature at 590 oF.

Cut on grade products to storage

Now fill Re-boiler up to 90% and start increasing its temperature gradually up to 300oF.

The emergency conditions which can arise during the operation of plant are:

Loss of cooling water

Loss of air cooled exchangersPower failureInstrument air failureFuel failure

Low crude charge

Heater tube failure

Fire, explosion or rupture


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