Patent ID: 7308805
Filing Date: 2007-12-18
Classification: C09K,F25J

Abstract:
1. A method for liquefying a gas ( 1 ) which comprises cooling a feed gas stream successively through at least two heat exchange zones ( 310 , 311 , 312 ; 353 ) at respective temperature ranges to provide a liquefied product ( 13 ), wherein refrigeration for cooling the feed gas stream in the temperature ranges is provided by respective vaporizing refrigerants ( 117 , 213 , 315 ), wherein the refrigerant ( 315 ) in the coldest temperature range is only partially vaporized in the coldest heat exchange zone ( 312 ) to form a partially vaporized refrigerant ( 316 ), and wherein the refrigerant is recirculated in a recirculating refrigeration process that comprises further vaporizing the partially vaporized refrigerant ( 316 ) in a further heat exchange zone ( 317 , 355 ) at temperatures above the highest temperature of the coldest heat exchange zone ( 312 ) to form a totally vaporized refrigerant ( 318 , 348 ), compressing ( 319 , 324 ; 349 ) the totally vaporized refrigerant ( 318 , 348 ) to yield a compressed refrigerant stream, and cooling the compressed refrigerant stream to provide a coldest refrigerant ( 315 ), characterized in that the entire compressed refrigerant stream is cooled by either (i) cooling the entire compressed refrigerant stream ( (ii) cooling the entire compressed refrigerant stream (