Licensed Units

Acid Gas Removal

Natural gas from the Feed Gas Metering 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.

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.

The process licensor of this unit is Lurgi and the main sub-licensor is BASF.

Dehydration and Mercaptan Removal

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 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.

Regeneration of the molecular sieve beds is achieved by means of the fuel gas coming from Nitrogen Removal Unit, which is heated using regeneration gas heater. 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. In order to have a continuous operation three beds are in adsorption mode while two beds are operating in regeneration mode.

The process licensor of this unit is Lurgi and the main sub-licensor is Zeochem.

Sulfur Recovery Unit

The enriched H2S from the Acid Gas Removal Unit 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 multi purpose burner 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 have all sulfur compounds hydrogenated or hydrolyzed to H2S and absorbed by MDEA solvent. The off gas 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.

The process licensor of this unit is Lurgi.

Fractionation Unit

The main purpose of the Fractionation Unit is to separate heavier components from the light ends of the natural dry and sweet gas and to recover propane (C3), butane (C4) and NGL condensates (C5+) separately. In the downstream Liquefaction Unit the light ends will be liquefied and subcooled to yield the LNG. Fractionation Unit delivers sufficient methane, ethane and propane make up for the refrigerant cycles. Nitrogen make up is assumed to be supplied from the utility units.

The process licensor of this unit is Linde AG.

Liquefaction Unit

In the Liquefaction Unit the compressed lean feed gas from the Fractionation is precooled, liquefied and subcooled before it is routed to the Nitrogen Removal and Purification. In addition the liquefaction and the subcooling refrigerant are also precooled, condensed and subcooled in the Liquefaction. The cooling duty for the three process steps precooling, liquefaction and subcooling is provided by a propane and two mixed refrigerant cycles in the MFC3 Process (Mixed Fluid Cascade with C3 Precooling Process).

The process licensor of this unit is Linde AG.

Refrigeration Unit

The necessary refrigeration duty for the precooling, liquefaction and subcooling of the natural gas is provided by three refrigerant cycles:

  • Precooling cycle refrigerant consisting of propane
  • Liquefaction cycle refrigerant consisting of propane, ethane and methane
  • Subcooling cycle refrigerant consisting of ethane, methane and nitrogen

A small fraction of the refrigeration duty provided by the precooling cycle is utilised in the Chiller at the inlet of the Dehydration & Mercaptan Removal to partly condense water from the natural gas stream in order to reduce the necessary capacity of the adsorbers. Refrigeration duty of the precooling cycle is also utilised in the C2 Make Up Column Condenser for the condensation of ethane from the C2H6 Make Up Column.

The process licensor of this unit is Linde AG.

Nitrogen Removal and Purification Unit

In this unit the nitrogen content of the LNG is adjusted to meet the required product specification by removing nitrogen from the LNG. The nitrogen-rich gas is purified and pure nitrogen is sent to atmosphere. The remaining methane-rich product is compressed and routed back via the Fractionation to the Liquefaction.

The process licensor of this unit is Linde AG.