Patent ID: 7210311

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 by a closed loop refrigeration cycle; (2) said cooled natural gas stream is divided into at least a first gaseous stream and a second gaseous stream; (3) said first gaseous stream is cooled by a closed loop refrigeration cycle to condense substantially all of it and thereafter expanded to an intermediate pressure; (4) said second gaseous stream is expanded to said intermediate pressure; (5) said expanded substantially condensed gaseous first stream and said expanded gaseous second stream are directed into a distillation column wherein said streams are separated into a volatile residue gas fraction containing a major portion of said methane and lighter components and a relatively less volatile fraction containing a major portion of said heavier hydrocarbon 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.