Patent ID: 6742358
Filing Date: 2004-06-01
Classification: F25J

Abstract:
In a process for liquefying a natural gas stream containing methane and heavier hydrocarbon components wherein:(a) said natural gas stream is cooled under pressure to condense at least a portion of it and form a condensed stream; and (b) said condensed stream is expanded to lower pressure to form said liquefied natural gas stream; the improvement wherein (1) said natural gas stream is treated in one or more cooling steps; (2) said cooled natural gas stream is expanded to an intermediate pressure and thereafter directed into a mid-column feed position on a distillation column wherein said stream is separated into a more volatile vapor distillation stream and a relatively less volatile fraction containing a major portion of said heavier hydrocarbon components; (3) a vapor distillation stream is withdrawn from a region of said distillation column below said expanded cooled natural gas stream and cooled sufficiently to condense at least a part of it, thereby forming a vapor stream and a liquid stream; (4) at least a portion of said expanded cooled natural gas stream is intimately contacted with at least part of said liquid stream in said distillation column; (5) said vapor stream is combined with said more volatile vapor distillation stream to form a volatile residue gas fraction containing a major portion of said methane and lighter components; and (6) said volatile residue gas fraction is cooled under pressure to condense at least a portion of it and form thereby said condensed stream.