Patent ID: 8590340
Filing Date: 2013-11-26
Classification: F25J

Abstract:
1. In a process for the separation of a gas stream containing methane, C 2 components, C 3 components, and heavier hydrocarbon components into a volatile residue gas fraction and a relatively less volatile fraction containing a major portion of said C 2 components, C 3 components, and heavier hydrocarbon components or said C 3 components and heavier hydrocarbon components, in which process (a) said gas stream is cooled under pressure to provide a cooled stream; (b) said cooled stream is expanded to a lower pressure whereby it is further cooled; and (c) said further cooled stream is directed into a distillation column and fractionated at said lower pressure whereby the components of said relatively less volatile fraction are recovered; the improvement wherein following cooling, said cooled stream is divided into first and second streams; and (1) said first stream is cooled to condense substantially all of it and is thereafter expanded to said lower pressure whereby it is further cooled; (2) said expanded cooled first stream is thereafter supplied to said distillation column at a first mid-column feed position; (3) said second stream is expanded to said lower pressure and is supplied to said distillation column at a second mid-column feed position; (4) a distillation vapor stream is withdrawn from a region of said distillation column below said expanded cooled first stream and is compressed to an intermediate pressure; (5) said compressed distillation vapor stream is cooled sufficiently to condense at least a part of it, thereby forming a condensed stream; (6) at least a portion of said condensed stream is expanded to said lower pressure and is thereafter supplied to said distillation column at a third mid-column feed position located above said expanded cooled first stream; (7) an overhead vapor stream is withdrawn from an upper region of said distillation column and at least a portion of said overhead vapor stream is directed into heat exchange relation with said compressed distillation vapor stream and heated, thereby to supply at least a portion of the cooling of step (5); (8) said heated overhead vapor stream is compressed to higher pressure and thereafter divided into said volatile residue gas fraction and a compressed recycle stream; (9) said compressed recycle stream is cooled sufficiently to substantially condense it; (10) said substantially condensed compressed recycle stream is expanded to said lower pressure and supplied to said distillation column at a top feed position; and (11) 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 portions of the components in said relatively less volatile fraction are recovered.