Hydrocarbon gas processing featuring a compressed reflux stream formed by combining a portion of column residue gas with a distillation vapor stream withdrawn from the side of the column

摘要

A process and an apparatus are disclosed for the recovery of ethane, ethylene, propane, propylene, and heavier hydrocarbon components from a hydrocarbon gas stream. The stream is cooled and divided into first and second streams. The first stream is further cooled to condense substantially all of it and divided into first and second portions. The first and second portions are expanded to the fractionation tower pressure and supplied to the fractionation tower at upper mid-column feed positions, with the expanded second portion being heated before it enters the tower. The second stream is expanded to the tower pressure and supplied to the column at a mid-column feed position. A distillation vapor stream is withdrawn from the column above the feed point of the second stream, combined with a portion of the tower overhead vapor stream, compressed to higher pressure, and directed into heat exchange relation with the remaining tower overhead vapor stream and the expanded second portion to cool the compressed combined vapor stream and condense at least a part of it, forming a condensed stream. At least a portion of the condensed stream is expanded to the tower pressure and directed to the fractionation tower as its top feed. The quantities and temperatures of the feeds to the fractionation tower are effective to maintain the overhead temperature of the fractionation tower at a temperature whereby the major portion of the desired components is recovered.

主权项

1. In a process for the separation of a gas stream containing methane, C2 components, C3 components, and heavier hydrocarbon components into a volatile residue gas fraction and a relatively less volatile fraction containing a major portion of said C2 components, C3 components, and heavier hydrocarbon components or said C3 components and heavier hydrocarbon components, in which process
said gas stream is cooled under pressure to provide a cooled stream; said cooled stream is expanded to a lower pressure whereby it is further cooled; and 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; (2) said substantially condensed first stream is divided into at least a first condensed portion and a second condensed portion; (3) said first condensed portion is expanded to said lower pressure whereby it is further cooled, and is thereafter supplied to said distillation column at an upper mid-column feed position; (4) said second condensed portion is expanded to said lower pressure whereby it is further cooled, is heated, and is thereafter supplied to said distillation column at said upper mid-column feed position or at an additional mid-column feed position; (5) said second stream is expanded to said lower pressure and is supplied to said distillation column at a mid-column feed position below said upper mid-column feed position; (6) an overhead vapor stream is withdrawn from an upper region of said distillation column and divided into at least a first vapor portion and a second vapor portion; (7) said second vapor portion is heated, thereafter discharging at least a portion of said heated second vapor portion as said volatile residue gas fraction; (8) a distillation vapor stream is withdrawn from a region of said distillation column (a) above said upper mid-column feed position; or (b) below a top feed position and above said upper mid-column feed position; or (c) below said upper mid-column feed position and above said mid-column feed position; or (d) below said mid-column feed position;and is combined with said first vapor portion to form a combined vapor stream;
(9) said combined vapor stream is compressed to higher pressure; (10) said compressed combined vapor stream is cooled sufficiently to condense at least a part of it, thereby forming a condensed stream while supplying at least a portion of the heating of steps (4) and (7); (11) at least a portion of said condensed stream is expanded to said lower pressure and is thereafter supplied to said distillation column at said top feed position; and (12) 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.