Internship Report on Front End Compression (Qadirpur Gas Field, OGDCL)

Qadirpur Gas Plant Internship Report (CCR-2)

8/119/2016 OGDCL

Prepared By: Sohail Abbas (CSR Internee) Shahid Zafar (CSR Internee)

Submitted To: I/C Process

Front End Compression General Description: OGDCL Qadirpur Gas plant is basically gas separation plant. The raw gas, coming from wells, contains impurities like Hydrogen Sulphide, CO2 and others. So to obtain methane as sweet gas separation is needed. This plant was built at pressure conditions of 780psig, which was natural pressure obtaining from the producing wells. Now the pressure of the wells is reduced to almost 305psig. That is why compression of the raw gas is needed to meet the requirement of the plant. Central Control Room 2 (CCR-2) is responsible for the operation of compression facility and in addition to this, it also provide the utilities like Instrument air, Plant air and Instrument Nitrogen to the mother plant. Raw gas from the wells is transferred to two main headers, named Eastern header and Northern header. These both headers form a common Header, from which raw gas enters in the slug catchers, which removes the liquid hydrocarbons forming the condensate and water. Then raw gas goes to compression facility which includes reciprocating and centrifugal compressors.

1. Gas Gathering System Raw gas from the different wells in eastern side of the plant meets in a common pipe called as Eastern Header. And the raw gas from northern wells mixes in the Northern Header.

Header Pipe size (inches) Flow rate (MMSCFD) Eastern Northern

26 30

105 235

These two headers having valves to control the flow rate combines form a common header from which gas is transferred to liquid separation unit to separate liquid droplets in the gas. This liquid separation unit is called slug catchers.

2. Slug Catchers The raw gas form the wells contain too much vapors of higher hydrocarbons and water which can cause damage to compressors. So it is necessary to remove liquid drops before the gas entering to compressors section. Two slug catchers are installed at the plant operating at same principle, vessel type slug catcher and Finger type slug catcher. As the gases are of low density then liquids, they go up direction leaving liquid at bottom. Raw gas leaving the slug catchers is then routed to the compression section. The process flow diagram from gathering system to the compressors is shown here.

Fig: PFD Slug Catchers

Reciprocating Compressors (QICP) 1. Introduction: Qadirpur Interim Compression Project (QICP) includes fourteen reciprocating compressors acting on same principle. All of the compressors are engine driven. Each compressor has its own gas engine. They are installed to meet the demand of main plant. This plant was built at pressure conditions of 720-750psig, which was natural pressure obtaining from the producing wells. Now the pressure of the wells is reduced to almost 320psig. That is why compression of the raw gas is needed to meet the requirement of the plant. These all compressors are operating in parallel having same suction header and the discharge header. Raw gas from suction header goes to the inlet of each compressor and after compression; it is discharged into main discharge header, from where it is transferred to main plant for separation.

2. Compressors Process Description: Raw gas coming from well headers is introduced in slug catchers to remove liquid contained in it. After slug catchers, vessel as well as finger type slug catchers, raw gas is transferred to compression facility. Part of the gas comes in main suction header of reciprocating compressors and other goes to centrifugal compressors. The properties of suction header line of reciprocating compressors are illustrated below: Header Suction

Diameter (inches) 26

Temperature (℉) 105-110

Pressure (psig) 314-320

Flow rate (MMSCFD) 150-160

Every reciprocating compressor is getting its suction from suction line in parallel. The suction line of each compressor contains an emergency shutdown valve to control the flow rate to the compressor. The raw gas then goes to the inlet of scrubber prior entering to compressor. After slug catchers gas still contain some liquid droplets which can be dangerous for compressor that is why the scrubbers are installed at the inlet of each compressor.

i.

Scrubber:

The function of scrubber is to prevent entering of liquid droplets to the compressor cylinders. It works on the general gravity separation principal. Gas enters at middle point of the scrubber vessel. It then passes to demister pad which removes liquid by settling then down. The scrubber vessel contain liquid level controller, which controls the liquid level at desired level. The liquid level is maintained so that gas cannot escape through bottom drain of vessel. The raw gas is then discharged from the top of the vessel as shown in the diagram. After the scrubber, raw gas enters to the suction bottle of the compressor.

ii.

Suction Bottle:

Suction bottle gives smooth flow to the compressor. It removes the pulses in the gas which can cause harm to compressor. It is also known as pulsation bottle.

iii.

Compressor:

The Ariel compressors are reciprocating compressors. They are double acting balanced opposed two stage compressors, having four cylinders. In double acting compressor, gas is compressed on both side of the piston and also has two discharge strokes per revolution. Each two opposite cylinders are balanced opposed shown in diagram. The cranks are arranged so that the motion of each piston is balanced by the motion of the piston opposite to it. Raw gas after suction bottle is introduced in the piston at 315psig & 103℉, which after 1st stage compression goes to the discharged bottle. As compression causes in rise of temperature, gas is cooled in fan cooler prior entering to 2nd stage compression. After cooling it is routed to other scrubber to remove moisture and then it goes for 2nd stage compression. After 2nd stage its discharge pressure is about 740psig. The specifications of each compressor are listed below:

Specs

Designed

Operating

Alarm

RPM Discharge Pressure(psig) Capacity(MMSCFD)

1500 1270

900-1150 720-780

1275 800

40

16-20

NA

iv.

Discharged bottle:

It’s working principal and function is same as of suction bottle.

v.

Fin Fan cooler:

Gas after compression enters in cooler in the tubes having fins. Fan of the cooler is driven by same prime mover (Waukesha engine) of compressor. As raw gas passes from the tubes, fan blows ambient air on it. All the tubes have fins which increases the heat transfer rate. The condition of raw gas before and after cooler is as follows:

Condition

Temperature ℉

Entering Discharge

180 110

Raw gas leaving the fan goes for 2nd stage compression in similar manner as it was in 1st stage compression. Then raw gas goes to discharge header. The compressors log sheet is illustrated below: Compressor Suction press (psig) A-1301 A-1302 A-1303 A-1304 A-1305 A-1306 A-1307 A-1308 A-1309 A-1310 A-1311 A-1312 A-1313 A-1314

Suction temp(℉)

314 312 315 314

115 112 114 113

Inter stage press. (psig) 524 542 530 540

314

111

306 313 306 313 314

Discharged 1st stage 2nd stage press. Discharged Discharged (psig) temp(℉) temp(℉) 750 760 740 752

182 191 188 192

141 166 170 167

532

758

193

153

117 115 116

528 568 455

745 759 750

182 199 109

153 159 180

113 114

536 540

763 768

190 179

166 169

vi.

Discharge Header:

All the gas discharging from each compressor is routed to main discharge header. The properties of discharged header are as follows: Header Discharge

Diameter (inches) 24

Diagram of whole system is shown below:

Temperature (℉) 105-110

Pressure (psig) 740-750

Flow rate (MMSCFD) 150-160

3. Engine (Waukesha) There are fourteen numbers of Waukesha engines, one for each compressor, operating at same principle. Fuel for engine is natural gas which is obtained from fuel gas system. Here some description is provided. The Waukesha engine has 12 cylinders, 6 from one side and 6 opposite to it (V type). All of them are mounted on same crankshaft which rotates primary to reciprocating compressor. The pistons in the cylinder are timed so that at least three power strokes are occurring at same time. The main parts of the engine are listed below.                         

ESM Engine Control unit Cylinders pistons Crankcase Crankshaft Camshaft Intake manifold Exhaust manifold Carburetor Regulator Turbocharger Auxiliary water pump Jacket water pump Starter motor Oil pump Push rod Rocker arm Magnetic pickup Gear train IPM-D Flywheel Oil cooler Oil filter Governor actuator Waste gate

i.

Fuel gas System of engine:

Engine utilizes sale gas (Methane) coming from sale gas headers to fuel gas system. Each engine gets its fuel from common fuel header having pressure of 180psig and flow rate of 1.9MMSCFD. At the suction of each engine, fuel gas passes through fuel gas scrubber which restrict liquid particle to engine carburetor. After scrubber fuel gas goes to gas regulator, which controls the pressure of gas to 60psig for engine carburetors. Their also exist a line of fuel which goes to engine starter motor to rotate crankshaft during startup of engine and to pre-lube pumps, which then goes to vent line.

4. Lubrication System Lube oil is used as lubricant of engine as well as for compressor. It provides lubrication, cooling and cleaning to the parts of machine. It prevents wear and tear of equipments. Oil level, pressure and temperature are maintained in the system. Lubrication system consist of following things  

 



Day Tank: it is used to maintain oil level through the control valves at desired point. It is simply a vessel for storing lube oil. Pre lube Pumps: two pumps are only used (one for compressor and one for engine) to lubricate whole system before starting of the engine and compressor. These both are pneumatically driven by fuel gas. Oil pumps: these pumps are shaft driven. They are used for lubrication while the machine is running. Oil cooler: it is used to dissipate heat of lube oil which was gained by lube oil during lubrication, so that the oil can be used effectively again. Auxiliary water is used as coolant. Oil filter: it filters oil to remove contaminants carried by oil. Micro spin Filters are used for filtering engine lube oil.

The conditions of lube oil for compressor as well as for engine are as follows: Condition Operating High Alarm Trip Low Alarm Trip

Compressor Pressure (psig) Temperature (℉) 59 105 250 190 300 195 37 N/A 35 N/A

Engine Pressure (psig) Temperature (℉) 53.6 180 95 190 110 195 37 N/A 35 N/A

During the startup of engine, it is started at offload till the temperature of lube oil reaches at 110℉ and the rotations reaches at 775rpm.

5. Cooling System The cooling system provides cooling for compressor and engine. It includes: Jacket Water Circuit: Jacket water is provided as a jacket to the engine to cool the whole body of engine. The jacket water pump rotates the flow of coolant (De-mineralized water) to exchange heat from engine body. It gets its suction from surge tank. After exchanging heat, water goes to remote heat transfer devise; here it is fin fan cooler. It has following components:     

Jacket Water Header Water manifold Jacket Water pump Fin fan cooler Control valve

Auxiliary water circuit: Auxiliary water is coolant for the compressor and engine auxiliaries. It is used as coolant in lube oil cooler and intercooler. It also has separate pump to rotate the water. It includes     

Auxiliary Water pump Intercooler Oil cooler Fin fan cooler Control valve

Centrifugal Compressors Introduction The gas coming from the slug catchers enters in the common suction line of the centrifugal compressors, from where all three compressors get their suction. The suction pressure of the compressors is around 305psig. As all three compressors are of same construction, operating principle and operating conditions, we will discuss here as one compressor (Train-A). Centrifugal compressors are two stage compressors; 1st stage is called Low Pressure (LP) and other is High Pressure (HP). The prime mover for each compressor is Gas Turbine. Their tag names are Turbine Train-A, Turbine Train-B and Turbine Train-C one for each compressor. These all compressors are operating in parallel having common suction header and the discharge header. Raw gas from suction header goes to the inlet of each compressor and after compression; it is discharged into main discharge header, from where it is transferred to main plant for separation.

Compressors Process Description Raw gas coming from well headers is introduced in slug catchers to remove liquid contained in it. After slug catchers (vessel as well as finger type) raw gas is transferred to compression facility. Part of the gas comes in main suction header of reciprocating compressors and other goes to common suction header of centrifugal compressors.

i.

Suction Header

The properties of main suction header are illustrated below: Header Suction

Diameter (inches) 26

Temperature (℉) 105-110

Pressure (psig) 305-310

Flow rate (MMSCFD) 200-250

Each centrifugal compressor is getting its suction from common suction header in parallel. The inlet line of each compressor contains an emergency shutdown valve (Pneumatically controlled) and also a manual valve to control the flow rate to the compressor. The raw gas then goes to the inlet of LP scrubber prior entering to compressor because after slug catchers gas still contain some liquid droplets which can be dangerous for compressor.

ii.

LP Scrubber:

The function of scrubber is to prevent entering of liquid droplets to the compressor. It works on the general gravity separation principal. Gas enters at bottom of the scrubber vessel. It then goes upward to discharge side and liquid condensate settles down to bottom of the scrubber due to gravity. It then passes to demister pad which removes further liquid by settling then down. The scrubber vessel contain liquid level controller, which controls the liquid level at desired set point. This mechanism contains three level transmitters (LT-0104A, LT-0105A and LT-0106A) and a level control valve (LCV-0104A). LCV is mounted on bottom drained pipe and is signaled from LT. This mechanism ensures that the vessel should not got flooded and also not to become empty. If any of two above condition reaches, turbine will trip and compressor too. That’s why the desired liquid level (usually 40%) is maintained in It. Level is maintained because gas shouldn’t escape through bottom drain of vessel. Following are the conditions adjusted for the low pressure LP scrubber:

Set point Liquid level (%)

40

Alarm Low High 15 80

Trip Low 10

High 90

The raw gas is then discharged from the top of the vessel. It then goes to the suction of Low Pressure Compressor (LP Compressor).

iii.

LP Compressor

It is multi-stage centrifugal compressor. This means it has more the one impeller and diffuser. Each impeller and diffuser makes a stage. Raw gas at suction pressure of 300psig comes at the eye of first impeller. As the gas leaves the first impeller it gains some velocity and pressure. The increased velocity partially converted into pressure in the diffuser. As the gas leaves the diffuser, it enters the return passage, which guides it into the eye of next impeller. In this way each impeller adds to the total energy of the gas. When gas leaves LP compressor its pressure becomes 530-540psig. A typical diagram of multi-stage centrifugal compressor is shown.

LP Compressor’s suction and discharge gas properties are:

Compressor

Suction Alarm

Operating

Trip

Discharge Alarm

Operating

Trip

Pressure (psig)

300-305

Low 110

High Low High 496 100 584

530-570

Low 400

High Low High 950 390 1000

Temperature (℉)

110-120

N/A

140

190-240

N/A

265

N/A

N/A

N/A

As compression causes rise in temperature so after compression gas is transferred to fin fan cooler to cool down the discharged gas prior to further compression.

iv.

Gas cooler (inter stage cooling)

Gas after compression enters in cooler in the tubes having fins. Two Fans of the cooler are motor driven. As raw gas passes from the tubes, fan blows ambient air on it, which causes gas temperature to reduce. All the tubes have fins which increases the heat transfer rate. The temperature of raw gas before and after the 1st stage cooler is as follows:

Temperature ℉

Condition Entering

180-220 110-120 150 160

Operating Alarm Trip

Discharge

Cooling of gas causes the liquid vapors to condense, so we need to remove liquid droplets. To do this gas goes to High Pressure Scrubber (HP Scrubber). It passes to the anti-surge valve prior to HP scrubber. Anti-surge valve prevent the compressor from surging. It can be operated manual or auto by control system of the machine.

v.

HP Scrubber

It works on the same principle as LP scrubber. The only difference is of pressure and Height (HP is smaller to LP). It also contains three level transmitters (LT-0107A, LT-0108A and LT-0109A) and a level control valve (LCV-0109A). Its operating conditions are:

Set point Liquid level (%)

40

Alarm Low High 15 80

Trip Low 10

High 90

270

vi.

HP Compressor

It is also multi-stage centrifugal compressor. It is operating on same principle as described in LP compressor. The discharge from LP compressor is suction to HP compressor, making them two stage compressors. Its suction and discharge gas properties are: Compressor Operating

Suction Alarm

Pressure (psig)

520-550

Low 400

Temperature (℉)

110-120

N/A

Trip

High Low High 584 370 600 132

N/A

N/A

Operating

Discharge Alarm

Trip

720-800

Low 400

High Low High 950 390 1000

190-200

N/A

265

N/A

To cool gas leaving the compressor, it is transferred to after stage coolers.

vii.

After stage Cooler

After stage coolers are like inter stage coolers. Two fans are driven by electric motor. The gas is subjected to enter the cooler in tubes having fins which helps to increase heat transfer area. Process gas is cooled by ambient air. Temperatures are given below:

Condition

Temperature ℉

Entering

180-220 110-120 150 160

Discharge

viii.

Operating Alarm Trip

Discharge Header

After leaving the cooler, process gas passes to the anti-surge valve and then goes to discharge header. Anti-surge valve prevent the compressor from surging. It can be operated manual or auto by control system of the machine. Discharge header properties are Header Discharge

Diameter (inches) 18

Temperature (℉) 110-115

Pressure (psig) 750-780

Flow rate (MMSCFD) 200-250

270

ix.

Seal Gas System

Compressor bearing uses lube oil for lubrication and cooling. The impellers of compressor and bearing have nothing in between them which separate them apart. So it might be possible that lube oil got mixed with the process gas. To prevent mixing of lube oil to process gas, a seal of other gas is maintained in between them with high pressure. Seal gas should be a gas which does not affect the concentration of process gas. Usually Nitrogen and sale gas (methane) is used here.

Gas Turbine (Prime mover)

Introduction: As it stated earlier that each centrifugal compressor is driven by the gas turbine, so it is necessary to mention description of gas turbine. A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in between. Three numbers of gas turbines are installed here in front end compression facility having tag names as Train A, Train B and Train C. These all turbines are Solar Turbine by A Caterpillar Company.

Description: A gas turbine engine is a type of internal combustion engine. Essentially, the engine can be viewed as an energy conversion device that converts energy stored in the fuel to useful mechanical energy in the form of rotational power. The term “gas” refers to the ambient air that is taken into the engine and used as the working medium in the energy conversion process.

This air is first drawn into the engine where it is compressed, mixed with fuel and ignited. The resulting hot gas expands at high velocity through a series of airfoil-shaped blades transferring energy created from combustion to turn an output shaft.

1. Basic Components and their Description i.

Air Intake System

The air is drawn in the combustion chamber through filters. 80 filters are installed in the intake system, which filters the air before entering to combustion chamber. The differential pressure of air is maintained, which indicates the smooth working of filters. If DP is more than the desired value, cleaning is carried out. Cleaning is usually carried out using Instrument air from utilities. Cleaning of air filters is carried out using Huff and Puff system. If after cleaning, the DP is still higher then filters are changed.

ii.

Compressor

The axial type compressor takes in outside air and then compacts and pressurizes the air molecules through a series of rotating and stationary compressor blades. Flow of air is controlled by inlet Guide Vanes (IGV’s) at compressor. Compressor at startup is driven by using starter motor and then by turbine itself. Starter motor is electrically driven and got de-latch to the system when NGP (Nominal Gas Producer) speed reaches to 65%. Compressor discharge pressure is about 130-160 psig. NGP maximum range is set at 103.6% and is operated between 90 to 98%.

iii.

Combustor

In the combustor, fuel is added to the pressurized air molecules and ignited. The fuel to air ratio is 1:14.7. The heated molecules expand and move at high velocity into the turbine section. The

temperature in combustion chamber is also adjusted, having set point of 1360 ℉ when the turbine is in operation. This means that turbine will give alarm at that temperature at then get trip at 1440 ℉. Thirteen numbers of thermocouples are installed in the combustion chamber to sense the temperature. Normal operating temperature in chamber is about 1200 ℉ to 1300 ℉.

iv.

Turbine

The turbine converts the energy from the high velocity gas into useful rotational power though expansion of the heated compressed gas over a series of turbine rotor blades. Two turbines are placed in it. One is compressor turbine, whose shaft is coupled to compressor of turbine. 70 to 75% of energy is used by this turbine to run itself. Other is Power Turbine, whose shaft is coupled to driven load (here it is a centrifugal compressor).

Minimum speed of Power Turbine when idle should be 44% , while when loaded is 56.75%.

v.

Output Shaft & Gearbox

Rotational power from the turbine section is delivered to Centrifugal Compressor through the output shaft via a speed reduction gearbox.

vi.

Exhaust

The engine’s exhaust section directs the spent gas out of the turbine section and into the atmosphere.

2. Lube Oil System: The lubricating requirements for the gas turbine are furnished by a common forced-feed lubrication system. Lubricating fluid is circulated to the three main turbine bearings, generator bearings, reducing gear, accessory gear, as hydraulic oil in torque converter and also as control, trip oil, high pressure hydraulic oil & generator seal oil. This lube is also goes to centrifugal compressor bearings. Such a system must supply cool, clean and pressurized oil to bearing. This lube oil system includes the following: i. ii. iii. iv. v.

Lube oil reservoir in the accessory base Main lube oil pump Auxiliary lube oil pump Emergency lube oil pump Lube oil heat exchangers (Cooler and Heater)

In this system of turbine cooler (fin fan) and heater are operated as follows: Cooler 115℉ 105℉

ON OFF

Heater 95℉ 100℉

Cooler contain an electric motor driven fan and tubes having fins. Oil comes inside the tube and exchanges its heat with air. vi. vii.

Lube oil filters: ensure the circulation of clean oil. Mist Eliminator: recovers the oil vapors leaving the reservoir.

Pressure and temperature in the turbine is maintained as follows:

Operating Alarm Trip

Temperature ℉ 130-140 175 180

Pressure (psig) 33-38 10 8

3. Cooling Air system The cooling air system provides the necessary air flow from the blower to prevent excessive temperature buildup in the parts during normal. Atmospheric air from external centrifugal blowers is used cool the turbine exhaust frame. Air enters by passing from enclosure filters into the enclosure and then goes to exhaust. Inside frame temperature limits are set as Enclosure Alarm Trip

Temperature℉ 150 160

4. Fire Protection System Temperature sensor and smoke detectors are installed in the enclosure of turbine. Carbon dioxide system is installed in enclosure which will become activated while smoke detectors give signal to it. The carbon dioxide fire protection system extinguished fires by reducing the oxygen content of the air in the compartment. While the turbine is running the enclosure doors should be closed and fire system should be at auto position.

Plant Utilities Plant utilities at CCR-2 include:    

Ingersol Rand Instrument Air Compressor Atlas Capco Air Compressor Nitrogen Generation System Power House 2

1. Ingersol Rand Instrument Air Compressor (A-4701A/B) The air compression system is design for a supply of plant air and instrument air to the plant at a pressure of 105psig. Instrument air is critical to the plant operations. Therefore 2 compressors 4701A/B (one operational and other standby) are installed with two instrument air drier to provide instrument air and plant air to QICP. The Ingersoll is an electric motor driven, single stage screw compressor, the motor power requirements is 132kw. The package is complete with accessories piped, wired and base plate mounted in a close casing. Compression in screw type air compressor is created by the meshing of two (male and female screw) helical rotors. Coolant oil is added at the suction of compressor with air. We add coolant to remove compression heat and for lubrication purpose. The air/coolant mixture then discharges from the compressor into the element separator. The separator removes almost all the coolant from the mixture and coolant returns after cooling and air is discharged and is pushed through after cooler by passing through separator and cooling system. The coolant system consist of a sump, cooler, thermostatic valve and a filter and again the coolant is pressurized and forced to the bearings again. The compressor load control system is automatic ‘on-off line’. The compressor will operate to maintain a set discharge line pressure and is provided with restart system. The Off-load set point is 105psig and On-load is 94psig. The compressor is design to provide a supply of 620scfm of air at pressure of 110psig. The compressed air then goes to plant air receiver which removes the entertained liquids from the air. It provides one minute surge time capacity at 620 scfm, which is the maximum plant air requirement. 

Air Dryer:

The air to be dried is taken from outlet of the plant air receiver goes to two air dryers (one operational and other standby). Air dryer contain silica gel which removes the liquid droplets. Their exits to tower for one air dryer. While one is drying the air other will be on regeneration process. Regeneration is done by part of the dried air. These air dryers reduces the dew point of

air to −50℃. This means first moisture vapor in air will condense only when air temperature reduces to −50℃. After driers instrument air goes to four air receivers as shown in figure. These vessels provide surge capacity of 5 minute at flow of 320 scfm. The important things to check during operations are coolant level; package pre filters checked for blockage, the coolant temperature discharge pressure and discharge temperature.

2. Atlas Capco Air Compressor (0501A/B) This system also contains two screw compressors 0501A/B (one operational and other standby) with an air drier. The compressors load control system is automatic ‘on-off line’. The compressor will operate to maintain a set discharge line pressure and is provided with restart system. The Off-load set point of these compressor is 115psig and On-load is 94psig. Its operating procedure is identical to 4701 compressors.

3. Nitrogen gas generation process PSA NITROGEN GAS GENERTOR(X-0509) installed in QICP has a capacity of 230 Nm3/hr of 99% pure nitrogen at 90psig. Plant air or instrument air is its feed stalk. The air supply system should be capable of delivering an average of 372Nm3/hr. Carbon Molecular sieves are used adsorbent. I is very porous materials chosen because of the large specific surface area. Carbon molecular sieves (CMS) may utilize their molecular sieve characteristics to exclude some gas molecules from their structure based on the size of the molecules, thereby restricting the ability of the larger molecules to be adsorbed. The PSA system consist of 2 vessels (adsorption beds) loaded with carbon molecular sieves. The CMS adsorbs oxygen from the stream air, leaving a nitrogen stream which is collected in nitrogen buffer tank. The CMS bed has an adsorption (production cycle of 80 seconds duration. during this cycle the process valve allow the compressed air to enter the CMS bed and prevent the loss of compressed air through the silencer and once the production cycle complete the process valve allow to flow of nitrogen into buffer tank . During the adsorption cycle the CMS bed becomes loaded with oxygen after each production cycle the system has desorption cycle (blow down cycle) to regenerate the CMS bed. Desorption cycle is a few seconds in duration. After desorption cycle the process repeats adsorption (production). The nitrogen buffer tank is sized in such a way that it can store enough nitrogen to maintain the two bed specific desorption cycle during which no nitrogen is being produced. The product control valve which is located after the nitrogen buffer tank is used to establish and maintain flow rate and purity of two bed

system the system will produce higher purity nitrogen a lower flow rate and high purity nitrogen at higher floe rates. Excessive oil and moisture contamination in the inlet air is very detrimental to the adsorption vessel carbon molecular sieve (CMS) material. If there is any indication of excessive oil level in the feed air unit should be shut down and correct problem before restarting. High moisture content also effect the performance of the CMS bed.

4. Power house 2 The power house 2 is responsible to provide power to QICP it has a capacity of almost 2950 KW. Three rental (smart power) engine driven generator of Caterpillar with capacity as follow are installed: Tag Name G-3216 G-3212-1 G-3212-2

Capacity (KW) 1000 630 630

OGDCL owned Waukesha Engine (model-P486L) is also installed and attached with Marathon electric Magna synchronous AC generator. It normally remains standby as the other generator produce enough power to run the plant. All these generators can be synchronized. Synchronization is the process of matching the speed and frequency of a Generator or other source to a running network. After 3000 running hours the engine maintenance is necessary. Engine lube oil, oil filter and air filter should be replaced. Mostly shell mysella s5 n 40 is used for lubrication but other brands can also be used. The oil temperature and pressure and Engine performance tells us when we should have to replace filters and engine oil. The plant uses almost 600kW power in routine hours but when we start the turbine it required 170 kW more power to run the starter motor. The plant house provides power to run main lube oil pump of turbine, oil cooler (HX-901), inter and after cooler fans, the instrument air compressor 0501/4701 and the air conditioner of CCR 2 and QICP lighting. The power house also provides power to run pump 4101A/B and the sump pump 4102A/B of liquid knock out vessel side of CCR 2. The power house 2 is also equipped with battery system for emergency use. It has almost 285 batteries connected in parallel.