Patent ID: 7204100

Claim:
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 divided into at least a first stream and a second stream; (3) said first stream is cooled to condense substantially all of it and thereafter expanded to an intermediate pressure; (4) said second stream is expanded to said intermediate pressure; (5) said expanded first stream and said expanded second stream are directed into a distillation column wherein said streams are separated into a more volatile vapor distillation stream and a relatively less volatile fraction containing a major portion of said heavier hydrocarbon components; (6) a vapor distillation stream is withdrawn from a region of said distillation column below said expanded second stream and is cooled sufficiently to condense at least a part of it, thereby forming a residual vapor stream and a reflux stream; (7) said reflux stream is directed into said distillation column as a top feed thereto; (8) said residual 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 (9) said volatile residue gas fraction is cooled under pressure to condense at least a portion of it and form thereby said condensed stream.