Patent ID: 7637121
Filing Date: 2009-12-29
Classification: F25J

Abstract:
1. A process for liquefying a pressurized natural gas stream comprising the steps of: (a) providing a pressurized natural gas feed stream at a first pressure and a first temperature; (b) pre-cooling the pressurized natural gas feed stream by indirect heat exchange with a cold refrigerant stream to produce a cooled pressurized natural gas feed stream at a second temperature colder than the first temperature; (c) expanding the cooled pressurized natural gas feed stream in an expansion device, wherein expansion work from the expansion device is used to drive a compressor which compresses a refrigerant stream to produce a pressurized refrigerant stream for use in (b), the expansion resulting in a chilled feed stream that is directed to a natural gas liquefaction zone, wherein the chilled feed stream exiting the expansion device has a vapor fraction of at least 0.9; (d) cooling the pressurized refrigerant stream to produce a cooled, at least partially condensed pressurized refrigerant stream; (e) expanding the cooled, at least partially condensed pressurized refrigerant stream to produce the cold refrigerant stream employed in (b); and (f) liquefying the chilled feed stream in the natural gas liquefaction zone.