Patent ID: 9003828
Filing Date: 2015-04-14
Classification: F25J

Abstract:
1. A process for liquefying a hydrocarbon gas comprising the steps of: a) providing: b) coupling said mixed refrigerant system, said ammonia refrigeration system and said steam system in a manner whereby the mixed refrigerant gas turbine produces waste heat, the steam generator utilizes the waste heat from the gas turbine to produce steam for the steam turbine to drive the ammonia compressor, and the ammonia compressor provides ammonia refigerant to cool the inlet air of the mixed refrigerant gas turbine; c) passing the single mixed refrigerant through a first of the three main heat exchange pathways from the warm end to the cold end of the heat exchanger, expanding the single mixed refrigerant and passing the expanded single mixed refrigerant through the second of the three main heat exchange pathways from the cold end to the warm end of the heat exchanger in a counter-current flow direction to the flow of single mixed refrigerant in the first main heat exchange pathway to provide refrigeration to the heat exchanger; passing the ammonia refrigerant through the first minor heat exchange pathway in co-current flow direction to the flow of single mixed refrigerant to the single mixed refrigerant in the second main heat exchange pathway to provide additional refrigeration to the heat exchanger; d) passing the hydrocarbon gas through the third of the three main heat exchange pathways of the heat exchanger from the warm end to the cold end in heat exchange proximity and counter-current flow direction to the single mixed refrigerant in the second main heat exchange pathway and the ammonia refrigerant in the first minor heat exchange pathway to produce a hydrocarbon liquid; and e) providing a vapour recovery system in fluid communication with a hydrocarbon liquid storage zone and said heat exchanger, the vapour recovery system having a compressor to receive and compress boil-off gas from said storage zone, and passing the compressed boil-off gas through the second of the two minor heat exchange pathways in heat exchange proximity and counter-current flow direction to the single mixed refrigerant in the second main heat exchange pathway to produce hydrocarbon liquid and a low pressure gas concentrated in nitrogen, the hydrocarbon liquid being subsequently returned to the storage zone.