Patent ID: 8850849
Filing Date: 2014-10-07
Classification: F25J

Abstract:
1. 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 divided into at least a first liquid stream and a second liquid stream; (b) said first liquid stream is expanded to lower pressure and is thereafter supplied to a distillation column at an upper mid-column feed position; (c) said second liquid stream is heated sufficiently to vaporize it, thereby forming a vapor stream; (d) said vapor stream is expanded to said lower pressure and is supplied to said distillation column at a lower mid-column feed position; (e) said gas stream is divided into at least a first gaseous stream and a second gaseous stream; (f) said first gaseous stream is cooled to condense substantially all of it and is thereafter expanded to said lower pressure whereby it is further cooled; (g) said expanded substantially condensed first gaseous stream is thereafter supplied to said distillation column at an additional upper mid-column feed position; (h) said second gaseous stream is expanded to said lower pressure, is cooled, and is thereafter supplied to said distillation column at an additional lower mid-column feed position; (i) an overhead distillation stream is withdrawn from an upper region of said distillation column and divided into at least a first portion and a second portion, whereupon said first portion is compressed to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; (j) said compressed first portion is cooled sufficiently to at least partially condense it and form thereby a condensed stream, with said cooling supplying at least a portion of said heating of said second liquid stream; (k) said condensed stream is divided into at least a volatile liquid stream and a reflux stream; (l) said reflux stream is further cooled, with said cooling supplying at least a portion of said heating of said second liquid stream; (m) said further cooled reflux stream is supplied to said distillation column at a top column feed position; (n) said volatile liquid stream is heated sufficiently to vaporize it, with said heating supplying at least a portion of said cooling of one or more of said first gaseous stream and said expanded second gaseous stream; (o) said second portion is heated, with said heating supplying at least a portion of said cooling of one or more of said first gaseous stream and said expanded second gaseous stream; (p) 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 (q) 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.