Patent ID: 6446465
Filing Date: 2002-09-10
Classification: F25J

Abstract:
Apparatus for liquefying natural gas, comprising a series of heat exchangers for cooling the natural gas in countercurrent heat exchange relationship with a refrigerant, compression means for compressing the refrigerant, expansion means for isentropically expanding at least two separate streams of the compressed refrigerant, said expanded streams of refrigerant communicating with a cool end of a respective one of the heat exchangers, and a precooling refrigeration system for precooling the natural gas to a temperature below 0Â° C. before it is fed to the series of heat exchangers, and for precooling the compressed refrigerant discharged from a warm end of the series of heat exchangers to a temperature below 0Â° C. before it is fed back into the series of heat exchangers or to the expansion means, wherein a first of said separate refrigerant streams is cooled in at least one of the series of heat exchangers, and the precooling refrigeration system is arranged to pre-cool the refrigerant prior to cooling the first refrigerant stream in the series of heat exchangers, wherein precooled refrigerant in the or each refrigerant stream other than the first is fed directly to the expansion means without any further cooling, wherein the compression means comprises multiple compressors, and further comprising a stripper column containing a heat exchanger at or near the bottom thereof, the arrangement being such that the cooled natural gas discharged from the series of heat exchangers is fed to the stripper heat exchanger to provide reboil heat for the stripper, and is subsequently fed to the stripper.