Patent ID: 8434325

Claim:
A process for the separation of liquefied natural gas containing methane, C 2 components, and heavier hydrocarbon components and a gas stream containing methane, C 2 components, and heavier hydrocarbon components into a volatile residue gas fraction containing a major portion of said methane and said C 2 components and a relatively less volatile liquid fraction containing a major portion of said heavier hydrocarbon components wherein (a) said liquefied natural gas is heated sufficiently to vaporize it, thereby forming a vapor stream; (b) said vapor stream is expanded to lower pressure and is thereafter supplied to a distillation column at a first mid-column feed position; (c) said gas stream is expanded to said lower pressure, is cooled, and is thereafter supplied to said distillation column at a second mid-column feed position; (d) a distillation vapor stream is withdrawn from a region of said distillation column below said expanded vapor stream and said expanded cooled gas stream, whereupon said distillation vapor stream is cooled sufficiently to at least partially condense it, forming thereby a condensed stream and a stream containing any remaining vapor, with said cooling supplying at least a portion of said heating of said liquefied natural gas; (e) at least a portion of said condensed stream is supplied to said distillation column as a reflux stream at a top column feed position; (f) an overhead vapor stream is withdrawn from an upper region of said distillation column and divided into at least a first portion and a second portion, whereupon said second portion is compressed to higher pressure; (g) said compressed second portion is cooled sufficiently to at least partially condense it and form thereby a volatile liquid stream, with said cooling supplying at least a portion of said heating of said liquefied natural gas; (h) said volatile liquid stream is heated sufficiently to vaporize it, with said heating supplying at least a portion of said cooling of said expanded gas stream; (i) said first portion is heated, with said heating supplying at least a portion of said cooling of said distillation vapor stream; (j) said any remaining vapor stream and said heated first portion are combined to form a residue vapor stream, and said residue vapor stream is heated, with said heating supplying at least a portion of said cooling of said expanded gas stream; (k) said heated residue vapor stream is thereafter combined with said vaporized volatile liquid stream to form said volatile residue gas fraction containing a major portion of said methane and said C 2 components; and (l) the quantity and temperature of said reflux stream and the temperatures of said feeds to said distillation column are effective to maintain the overhead temperature of said distillation column at a temperature whereby the major portion of said heavier hydrocarbon components is recovered in said relatively less volatile liquid fraction by fractionation in said distillation column.