Patent ID: 9140490
Filing Date: 2015-09-22
Classification: F25J

Abstract:
1. A process for liquefying a gas stream, said process comprising: (a) providing said gas stream at a pressure of from 600 to 1,000 psia (4,137-6,895 kPa) as a feed gas stream; (b) providing a refrigerant at a pressure of less than 1,000 psia (6,895 kPa) by withdrawing a portion of said gas stream for use as said refrigerant; (c) compressing said refrigerant in a closed loop to a pressure greater than or equal to 1,600 to less than or equal to 5,000 psia (11,032 to 34,474 kPa) to produce a compressed refrigerant; (d) cooling said compressed refrigerant by indirect heat exchange with a cooling fluid; (e) expanding the compressed refrigerant of (d) to cool said compressed refrigerant, to produce an expanded, cooled refrigerant at a pressure of from greater than or equal to 100 psia (689 kPa) to less than or equal to 1,000 psia (6895 kPa); (f) passing said expanded, cooled refrigerant to a first heat exchange area; (g) compressing the feed gas stream of (a) to a pressure of from greater than or equal to 2,500 psia (17,237 kPa) to less than or equal to 3,500 psia (24,132 kPa) to produce a compressed feed gas stream; (h) cooling said compressed feed gas stream by indirect heat exchange with an air or water refrigerant cooler; (i) passing said compressed feed gas stream through the first heat exchange area to cool at least a part thereof by indirect heat exchange, to produce a compressed, further cooled feed gas stream, wherein the feed gas is used as the only refrigerant such that no external refrigerants are used, except for water or air; (j) passing the compressed, further cooled feed gas stream of (i) through a second heat exchange area for extra cooling; and (k) expanding said compressed, further cooled feed gas stream of (j) to reduce the pressure of said compressed, further cooled feed gas stream to a pressure of from greater than or equal to 50 psia (345 kPa) to less than or equal to 450 psia (3103 kPa) to produce an expanded, cooled gas stream; and (l) withdrawing a portion not to exceed 50% of said expanded, cooled gas stream of (k) and reducing its pressure in a reduction valve to a range of about 30-200 psia (207-1379 kPa) to produce a reduced pressure gas stream and passing the reduced pressure gas stream through the second heat exchange area of (j) as a cooling gas stream.