Patent ID: 9080810
Filing Date: 2015-07-14
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 said cooled stream is further cooled thereby forming a further cooled expanded stream; and (c) said further cooled expanded 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 said further cooled expanded stream is directed to a first mid-column feed position on said distillation column; and (1) a vapor distillation stream is withdrawn from a region of said distillation column below said first mid-column feed position and is cooled sufficiently to condense at least a part of said vapor distillation stream, thereby forming a condensed stream and a residual vapor stream containing any uncondensed vapor remaining after said vapor distillation stream is cooled; (2) at least a portion of said condensed stream is supplied to said distillation column at a second mid-column feed position above said first mid-column feed position; (3) an overhead vapor stream is withdrawn from an upper region of said distillation column and is directed into heat exchange relation with at least said vapor distillation stream and heated, thereby to supply at least a portion of the cooling of step (1) and forming a heated overhead vapor stream; (4) said heated overhead vapor stream is combined with any said residual vapor stream to form a heated combined vapor stream; (5) said heated combined vapor stream is compressed to higher pressure and thereafter divided into said volatile residue gas fraction and a compressed recycle stream; (6) said compressed recycle stream is cooled sufficiently to substantially condense-said compressed recycle stream, thereby forming a condensed compressed recycle stream; (7) said substantially condensed compressed recycle stream is expanded to said lower pressure and supplied to said distillation column at a top feed position above said second mid-column feed position; and (8) quantities and temperatures of said feed streams to said distillation column are effective to maintain an overhead temperature of said distillation column at a temperature whereby the major portions of the components in said relatively less volatile fraction are recovered.