Patent ID: 8584488

Claim:
A process for liquefying a portion of a natural gas stream containing methane and heavier hydrocarbon components to produce a liquefied natural gas stream wherein (a) said natural gas stream is cooled sufficiently to partially condense it and is thereafter divided into at least a first gaseous stream and a second gaseous stream; (b) said first gaseous stream is further cooled and is thereafter expanded to an intermediate pressure, whereupon said expanded cooled first gaseous stream is supplied at a lower feed position to a distillation column that produces an overhead vapor stream and a bottom liquid stream; (c) said second gaseous stream is separated into a vapor stream and a liquid stream; (d) said vapor stream is expanded to said intermediate pressure and is thereafter divided into at least a first portion and a second portion; (e) said first portion is cooled and is thereafter supplied to said distillation column at a mid-column feed position; (f) said second portion is heated, with said heating supplying at least a portion of said cooling of one or more of said natural gas stream and said first gaseous stream; (g) said overhead vapor stream is cooled sufficiently to at least partially condense it and form thereby a condensed stream; (h) said condensed stream is divided into at least a feed stream and a reflux stream, whereupon said reflux stream is supplied to said distillation column at a top column feed position; (i) said feed stream is further cooled and is thereafter expanded to lower pressure; (j) said expanded further cooled feed stream is separated into a first flash vapor stream and a flash liquid stream; (k) said flash liquid stream is expanded to still lower pressure; (l) said expanded flash liquid stream is separated into a second flash vapor stream and said liquefied natural gas stream; (m) said second flash vapor stream is heated, with said heating supplying at least a portion of said cooling of one or more of said natural gas stream, said first portion, said overhead vapor stream, and said feed stream; (n) said first flash vapor stream is heated, with said heating supplying at least a portion of said cooling of said feed stream; (o) said bottom liquid stream is expanded to said lower pressure, whereupon said expanded bottom liquid stream is combined with said heated first flash vapor stream to form a first combined stream; (p) said first combined stream is heated, with said heating supplying at least a portion of said cooling of one or more of said first portion and said overhead vapor stream; (q) said liquid stream is expanded to said lower pressure, whereupon said expanded liquid stream is combined with said heated first combined stream to form a second combined stream; and (r) said second combined stream is heated, with said heating supplying at least a portion of said cooling of said natural gas stream.