The following sections present the process line-up for one train of the LNG plant from the Feed Gas Metering to the LNG product loading
and describes the functionality of each units and main equipment items.

1-  Feed Gas Metering Unit-11
To provide feed gas to the project, a slug catcher is installed as part of the scope of work of POGC.
The feed gas supply pressure is controlled in the Feed Gas Metering where also the quality and quantity of the gas are measured for custody transfer purposes.

2-  Acid Gas Removal Unit-12
Natural gas from the Feed Gas Metering Unit is divided between the two LNG trains and fed to the Acid Gas Removal which uses the aMDEA process licensed by BASF.
In the AGR absorber, virtually all the CO2 and H2S are removed by lean amine solvent.
This removal is required to prevent solidification of these components during the liquefaction process and to meet the LNG product specification.

The rich solvent leaving the bottom of the absorber is first preflashed to recover light hydrocarbons, and subsequently stripped in a low pressure amine regenerator column,
using steam as heating medium. Acid gas from the amine regenerator which mainly consists of CO2 and H2S is routed to the Sulfur Recovery Unit.
Treated gas from the AGR absorber is sent to Dehydration and Mercaptan Removal Unit.

3-  Dehydration and Mercaptan Removal Unit-13
Feed gas to this unit is treated gas from the Acid Gas Removal Unit.
The treated gas is dehydrated and mercaptans contained in the treated gas are removed in this unit to prevent plugging of the downstream cryogenic equipment and to meet the LNG product specification.
The feed gas is cooled to 25 ˚C by chilling to condense the bulk of the water.
The water is removed in a separator vessel.
Gas from the separator is then passed over molecular sieve beds, removing the water to below 1 ppmv, mercaptan concentration
to less than 7.1 mg/Nm3 and total sulfur concentration to less than 25 mg/Nm3.

Regeneration of the molecular sieve beds is achieved by means of the fuel gas from the end flash section in the Nitrogen Rejection Unit,
which is heated using waste heat from the gas turbine driving the mixed refrigerant (MR) compressor.
After cooling and water removal, the regeneration gas is fed into the Purisol absorber where mercaptans are removed to less than 100 ppmv to meet the requirement of the fuel gas.
The rich solvent from the absorber is fed into the Purisol regenerator where the stripped mercaptan gas is sent to the Sulfur Recovery Unit.
The lean solvent from the bottom of the regenerator is fed to the absorber after cooled.

4-  Mercury Removal Unit-14
Elemental mercury from the feed gas can cause rapid corrosion of aluminium in the Refrigeration/Cryogenic Heat Exchanger.
Since the currently expected mercury concentration in the feed gas exceed the maximum allowable levels for the cryogenic systems,
a Mercury Removal Unit is included downstream of the Dehydration and Mercaptan Removal Unit.
The unit will comprise a single guard bed utilizing sulfur impregnated activated carbon in which mercury is removed to a level of less than 10 ng/Sm3.

5-  Liquefaction Unit-15
MFC® Process by Linde
In the Liquefaction Unit the pre-treated and dry natural gas stream is, in a first step, cooled and partly liquefied in order to
remove heavy hydrocarbons from the natural gas and to recover propane and butane to a significant extent.
After separation of the C3+ fraction from the natural gas stream in the Fractionation Unit the light end (C2-) is further cooled,
liquefied and sub-cooled before it is routed to the Nitrogen Rejection Unit.
The cooling duty for the process steps mentioned above is provided by three mixed refrigerant cycles in the MFC® Process (Mixed Fluid Cascade Process).

6-  Refrigeration Unit-16
The necessary refrigeration duty for the precooling, liquefaction and subcooling of the natural gas is provided by three closed mixed refrigerant cycles.
The purpose of Refrigeration Unit is to provide refrigeration to:
• Precool, liquefy the natural gas and subcool
• Provide reflux to deethanizer and chilling of recontactor column
• Cool the reinjected LPG

The refrigerant compressors are driven by electric motors. The power to motors will be supplied from a central power station for two trains.

7-  Fractionation Unit-17
The pre-cooled feed gas is expanded in the feed gas expander and fed into the recontactor column where heavy hydrocarbon is separated.
The lighter components from the recontactor column are sent to the cryogenic heat exchanger after recompression by the feed gas booster.
The recovery of individual refrigerant components for refrigerant storage unit, i.e., ethane and propane, requires fractionation.
The commercial grade LPG (propane and butanes) is separated in this unit.
The Fractionation Unit includes a deethanizer, an ethane make up column, a depropaniser and debutanizer for the purpose.
The condensate stream from the debutanizer bottoms is routed to the Condensate Stabilization Unit, constructed by others, via condensate rundown Unit.
Ethane and propane suitable for refrigerant makeup are stored in the Refrigerant Storage Unit. Propane and butanes products are fed into LPG Sweetening Unit.

2.5.8 Nitrogen Rejection Unit–18
The objective of the Nitrogen Rejection Unit is to flash off the nitrogen from the LNG product, to pump the LNG product
to storage and to deliver the nitrogen rich fuel gas at a pressure of 27.5 bar to the fuel gas system.
The pressure of the liquefied natural gas from the cryogenic heat exchanger is reduced and the gas flashed in the nitrogen removal column.
The overhead flash gas is routed via a flash vapor exchanger, where cold is recovered via a slipstream of mixed refrigerant vapor, to a fuel gas compressor.
A Nitrogen Purification Unit (NPU) will be installed to reduce N2 in fuel gas burning in gas turbines of Power Station

9-  Sulphur Recovery Unit-19
The Sulfur Recovery Unit consists of Acid Gas Enrichment (AGE), Claus and Tail Gas Treatment (TGT) sections to recover
a minimum 99% of the sulfur compounds contained in the acid gas from the Acid Gas Removal Unit.
The acid gas from the Acid Gas Removal Unit is treated by MDEA solvent to selectively absorb H2S against CO2
and then MDEA solvent is regenerated by steam stripping together with MDEA solvent from Tail Gas Treatment section.
The enriched H2S from the MDEA regenerator column and the mercaptan gas from Dehydration and Mercaptan Removal Unit are processed
to convert the hydrogen sulfide and other sulfur compounds into high purity sulfur in the Claus section.
For this purpose the Claus section have been designed so that the enriched H2S and the mercaptan gases are converted to elemental sulfur
in a thermal stage using the Lurgi’s KombiBurner process and subsequent two catalytic stages.
The liquid sulfur is sent for degassing to the Aquisulf process developed by ELF Aquitaine.
The Claus tail gas is sent for further treatment to Lurgi Tail Gas Treating section in which all sulfur compounds are hydrogenated or hydrolyzed to H2S and absorbed by MDEA solvent.
The off gas from Lurgi Tail Gas Treating section and the vent air from the Aquisulf process are burnt completely in the thermal incinerator to oxidize sulfur compounds to SO2.
The resulting flue gas is released via the stack to atmosphere.

10-  LPG Sweetening Unit-20
The objective of the LPG Sweetening Unit is to remove the sulfur compounds from propane and butane products from the Fractionation Unit.
Molecular sieve adsorbs the sulfur compounds in liquid phase and is regenerated by the fuel gas from the end flash section in the Nitrogen Rejection Unit.