Patent ID: 6182469
Filing Date: 2001-02-06
Classification: F25J,Y02C

Abstract:
In a process for the separation of a gas stream containing methane, C.sub.2 components, C.sub.3 components and heavier hydrocarbon components into a volatile residue gas fraction containing a major portion of said methane and a relatively less volatile fraction containing a major portion of said C.sub.2 components, C.sub.3 components and heavier hydrocarbon components, in which process(a) said gas stream is treated in one or more heat exchange steps and at least one division step to produce at least a first feed stream that has been cooled under pressure to condense substantially all of it, and at least a second feed stream that has been cooled under pressure;(b) said substantially condensed first feed stream is expanded to a lower pressure whereby it is further cooled, and thereafter supplied to a fractionation tower at a top feed point;(c) said cooled second feed stream is expanded to said lower pressure, and thereafter supplied to said fractionation tower at a mid-column feed point; and(d) said cooled expanded first feed stream and said expanded second feed stream are fractionated at said lower pressure whereby the components of said relatively less volatile fraction are recovered;the improvement wherein(1) a liquid distillation stream is withdrawn from said fractionation tower and heated;(2) said heated distillation stream is returned to a lower point on said fractionation tower that is separated from said withdrawal point by at least one theoretical stage; and(3) the quantities and temperatures of said feed streams to said fractionation tower are effective to maintain the overhead temperature of said fractionation tower at a temperature whereby the major portions of the components in said relatively less volatile fraction are recovered.