Patent ID: 8794030

Claim:
A process for the separation of liquefied natural gas containing methane and heavier hydrocarbon components and a gas stream containing methane and heavier hydrocarbon components into a volatile residue gas fraction containing a major portion of said methane 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supplied to said distillation column at a second mid-column feed position; (d) a distillation vapor stream is withdrawn from a region of said distillation column below said expanded vapor stream and said expanded cooled gas stream, whereupon said distillation vapor stream is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 and form thereby a first condensed stream, with said cooling supplying at least a portion of said heating of said liquefied natural gas; (e) at least a portion of said first condensed stream is supplied to said distillation column at an upper mid-column feed position; (f) an overhead distillation stream is withdrawn from an upper region of said distillation column and divided into at least a first portion and a second portion, whereupon said first portion is compressed to higher pressure; (g) said compressed first portion is cooled sufficiently to at least partially condense it and form thereby a second condensed stream, with said cooling supplying at least a portion of said heating of said liquefied natural gas; (h) said second condensed stream is divided into at least a volatile liquid stream and a reflux stream; (i) said reflux stream is further cooled, with said cooling supplying at least a portion of said heating of said liquefied natural gas; (j) said further cooled reflux stream is supplied to said distillation column at a top column feed position; (k) 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; (l) said second portion is heated, with said heating supplying at least a portion of said cooling of said expanded gas stream; (m) said vaporized volatile liquid stream and said heated second portion are combined to form said volatile residue gas fraction containing a major portion of said methane; and (n) 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.