LNG PRODUCTION IN CRYOGENIC NATURAL GAS PROCESSING PLANTS

摘要

1. A process for liquefying a natural gas stream containing; methane and heavier hydrocarbon components wherein (a) said natural gas stream is withdrawn from a cryogenic natural gas processing plant recovering natural gas liquids; (b) said natural gas stream is cooled under pressure sufficiently to partially condense it; (c) a distillation stream is withdrawn from said plant to supply at least a portion of said cooling of said natural gas stream; (d) said partially condensed natural gas stream is separated into a liquid stream and a vapor stream, whereupon said liquid stream is directed to said plant; (e) said vapor stream is expanded to an intermediate pressure and further cooled at said intermediate pressure to condense it; (f) said condensed expanded stream is directed to a distillation column at a mid-column feed point; (g) a liquid distillation stream is withdrawn from a lower region of said distillation column and directed to said plant; (h) a vapor distillation stream is withdrawn from an upper region of said distillation column and cooled under pressure to condense at least a portion of it and form a condensed stream; (i) said condensed stream is divided into at least two portions, with a first portion directed to said distillation column at a top feed position; (j) a second portion of said condensed stream is expanded to lower pressure to form said liquefied natural gas stream; and (k) me temperature of said partially condensed natural gas stream and the quantities and temperatures of said feed streams 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 liquid stream and said liquid distillation stream.