Hydrocarbon Gas Processing

Abstract

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 divided into first and second streams. The first stream is cooled to condense substantially all of it, expanded to lower pressure, and supplied to a fractionation tower at an upper mid-column feed position. The second stream is cooled sufficiently to partially condense it and separated into vapor and liquid streams. The vapor stream is divided into first and second portions. The first portion is cooled to condense substantially all of it, expanded to the tower pressure, and supplied to the tower at the top feed position. The second portion is expanded to the tower pressure and supplied to the fractionation tower at an intermediate mid-column feed position. The liquid stream is expanded to the tower pressure and supplied to the column at a lower mid-column feed position. 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.

We claim: 
     
         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 prior to cooling, said gas 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 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;   (3) said second stream is cooled under pressure sufficiently to partially condense it;   (4) said partially condensed second stream is separated thereby to provide a vapor stream and at least one liquid stream;   (5) said vapor stream is divided into first and second portions;   (6) said first portion is cooled to condense substantially all of it;   (7) said substantially condensed first portion is expanded to said lower pressure whereby it is further cooled, and is thereafter supplied to said distillation column at a top feed position;   (8) said second portion 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;   (9) at least a portion of said at least one liquid stream is expanded to said lower pressure and is supplied to said distillation column at a lower mid-column feed position below said mid-column feed position; and   (10) 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.   
     
     
         2 . The improvement according to  claim 1  wherein
 (1) said gas stream is cooled under pressure sufficiently to partially condense it; 
 (2) said partially condensed gas stream divided into said first stream and said second stream; and 
 (3) said second stream is separated thereby to provide said vapor stream and said at least one liquid stream. 
 
     
     
         3 . The improvement according to  claim 1  wherein
 (1) said first stream is combined with at least a portion of said at least one liquid stream to form a combined stream; 
 (2) said combined stream is cooled to condense substantially all of it; 
 (3) said substantially condensed combined stream is expanded to said lower pressure whereby it is further cooled, and is thereafter supplied to said distillation column at said upper mid-column feed position; and 
 (4) any remaining portion of said at least one liquid stream is expanded to said lower pressure and is supplied to said distillation column at said lower mid-column feed position below said mid-column feed position. 
 
     
     
         4 . The improvement according to  claim 2  wherein
 (1) said first stream is combined with at least a portion of said at least one liquid stream to form a combined stream; 
 (2) said combined stream is cooled to condense substantially all of it; 
 (3) said substantially condensed combined stream is expanded to said lower pressure whereby it is further cooled, and is thereafter supplied to said distillation column at said upper mid-column feed position; and 
 (4) any remaining portion of said at least one liquid stream is expanded to said lower pressure and is supplied to said distillation column at said lower mid-column feed position below said mid-column feed position. 
 
     
     
         5 . The improvement according to  claim 1  wherein
 (1) said expanded substantially condensed first portion is supplied at a top feed position to a contacting and separating device that produces said volatile residue gas fraction and a bottom liquid stream, whereupon said bottom liquid stream is supplied to said distillation column; 
 (2) an overhead vapor stream is withdrawn from an upper region of said distillation column and is supplied to said contacting and separating device at a lower column feed position; and 
 (3) the quantities and temperatures of said feed streams to said contacting and separating device are effective to maintain the overhead temperature of said contacting and separating device at a temperature whereby the major portions of the components in said relatively less volatile fraction are recovered. 
 
     
     
         6 . The improvement according to  claim 5  wherein
 (1) said gas stream is cooled under pressure sufficiently to partially condense it; 
 (2) said partially condensed gas stream divided into said first stream and said second stream; and 
 (3) said second stream is separated thereby to provide said vapor stream and said at least one liquid stream. 
 
     
     
         7 . The improvement according to  claim 5  wherein
 (1) said first stream is combined with at least a portion of said at least one liquid stream to form a combined stream; 
 (2) said combined stream is cooled to condense substantially all of it; 
 (3) said substantially condensed combined stream is expanded to said lower pressure whereby it is further cooled, and is thereafter supplied to said distillation column at said upper mid-column feed position; and 
 (4) any remaining portion of said at least one liquid stream is expanded to said lower pressure and is supplied to said distillation column at said lower mid-column feed position. 
 
     
     
         8 . The improvement according to  claim 6  wherein
 (1) said first stream is combined with at least a portion of said at least one liquid stream to form a combined stream; 
 (2) said combined stream is cooled to condense substantially all of it; 
 (3) said substantially condensed combined stream is expanded to said lower pressure whereby it is further cooled, and is thereafter supplied to said distillation column at said upper mid-column feed position; and 
 (4) any remaining portion of said at least one liquid stream is expanded to said lower pressure and is supplied to said distillation column at said lower mid-column feed position. 
 
     
     
         9 . The improvement according to  claim 1  or  2  wherein said expanded said at least one liquid stream is heated and thereafter supplied to said distillation column at said lower mid-column feed position below said mid-column feed position. 
     
     
         10 . The improvement according to  claim 3  or  4  wherein said expanded said any remaining portion of said at least one liquid stream is heated and thereafter supplied to said distillation column at said lower mid-column feed position below said mid-column feed position. 
     
     
         11 . The improvement according to  claim 5  or  6  wherein said expanded said at least one liquid stream is heated and thereafter supplied to said distillation column at said lower mid-column feed position. 
     
     
         12 . The improvement according to  claim 7  or  8  wherein said expanded said any remaining portion of said at least one liquid stream is heated and thereafter supplied to said distillation column at said lower mid-column feed position. 
     
     
         13 . In an apparatus 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 said apparatus there being
 (a) a first cooling means to cool said gas stream under pressure connected to provide a cooled stream under pressure;   (b) a first expansion means connected to receive at least a portion of said cooled stream under pressure and expand it to a lower pressure, whereby said stream is further cooled; and   (c) a distillation column connected to receive said further cooled stream, said distillation column being adapted to separate said further cooled stream into said volatile residue gas fraction and said relatively less volatile fraction;   the improvement wherein said apparatus includes   (1) first dividing means prior to said first cooling means to divide said gas stream into first and second streams;   (2) second cooling means connected to said first dividing means to receive said first stream and cool it sufficiently to substantially condense it;   (3) said first expansion means connected to said second cooling means, said first expansion means being adapted to receive said substantially condensed first stream and expand it to said lower pressure, said first expansion means being further connected to said distillation column to supply said expanded substantially condensed first stream to said distillation column at an upper mid-column feed position;   (4) said first cooling means connected to said first dividing means to receive said second stream and cool it under pressure sufficiently to partially condense it;   (5) separating means connected to said first cooling means to receive said partially condensed second stream and separate it into a vapor stream and at least one liquid stream;   (6) second dividing means connected to said separating means to receive said vapor stream and divide it into first and second portions;   (7) third cooling means connected to said second dividing means to receive said first portion and cool it sufficiently to substantially condense it;   (8) second expansion means connected to said third cooling means to receive said substantially condensed first portion and expand it to said lower pressure, said second expansion means being further connected to said distillation column to supply said expanded substantially condensed first portion to said distillation column at a top feed position;   (9) third expansion means being connected to said second dividing means to receive said second portion and expand it to said lower pressure, said third expansion means being further connected to said distillation column to supply said expanded second portion to said distillation column at a mid-column feed position below said upper mid-column feed position;   (10) fourth expansion means connected to said separating means to receive at least a portion of said at least one liquid stream and expand it to said lower pressure, said fourth expansion means being further connected to said distillation column to supply said expanded liquid stream to said distillation column at a lower mid-column feed position below said mid-column feed position; and   (11) control means adapted to regulate the quantities and temperatures of said feed streams to said distillation column 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.   
     
     
         14 . The improvement according to  claim 13  wherein
 (1) said first cooling means is connected to receive said gas stream and cool it under pressure sufficiently to partially condense it; 
 (2) said first dividing means is connected to said first cooling means to receive said partially condensed gas stream and divide it into said first stream and said second stream; and 
 (3) said separating means is connected to said first dividing means to receive said second stream and separate it into said vapor stream and said at least one liquid stream. 
 
     
     
         15 . The improvement according to  claim 13  wherein
 (1) a combining means is connected to said first dividing means and said separating means to receive said first stream and at least a portion of said at least one liquid stream and form a combined stream; 
 (2) said second cooling means is connected to said combining means to receive said combined stream and cool it sufficiently to substantially condense it; 
 (3) said first expansion means is connected to said second cooling means to receive said substantially condensed combined stream and expand it to said lower pressure, said first expansion means being further connected to said distillation column to supply said expanded substantially condensed combined stream to said distillation column at said upper mid-column feed position; and 
 (4) said fourth expansion means is connected to said separating means to receive any remaining portion of said at least one liquid stream and expand it to said lower pressure, said fourth expansion means being further connected to said distillation column to supply said expanded liquid stream to said distillation column at said lower mid-column feed position below said mid-column feed position. 
 
     
     
         16 . The improvement according to  claim 14  wherein
 (1) a combining means is connected to said first dividing means and said separating means to receive said first stream and at least a portion of said at least one liquid stream and form a combined stream; 
 (2) said second cooling means is connected to said combining means to receive said combined stream and cool it sufficiently to substantially condense it; 
 (3) said first expansion means is connected to said second cooling means to receive said substantially condensed combined stream and expand it to said lower pressure, said first expansion means being further connected to said distillation column to supply said expanded substantially condensed combined stream to said distillation column at said upper mid-column feed position; and 
 (4) said fourth expansion means is connected to said separating means to receive any remaining portion of said at least one liquid stream and expand it to said lower pressure, said fourth expansion means being further connected to said distillation column to supply said expanded liquid stream to said distillation column at said lower mid-column feed position below said mid-column feed position. 
 
     
     
         17 . The improvement according to  claim 13  wherein
 (1) said second expansion means is connected to a contacting and separating means to supply said expanded substantially condensed first portion to said contacting and separating means at a top feed position, said contacting and separating means being adapted to produce said relatively less volatile fraction and a bottom liquid stream; 
 (2) said distillation column is connected to receive said bottom liquid stream, said distillation column being adapted to separate said bottom liquid stream into an overhead vapor stream and said relatively less volatile fraction; 
 (3) said distillation column is further connected to said contacting and separating means to supply said overhead vapor stream to said contacting and separating means at a lower column feed position; and 
 (4) said control means is adapted to regulate the quantities and temperatures of said feed streams to said contacting and separating means to maintain the overhead temperature of said contacting and separating means at a temperature whereby the major portions of the components in said relatively less volatile fraction are recovered. 
 
     
     
         18 . The improvement according to  claim 17  wherein
 (1) said first cooling means is connected to receive said gas stream and cool it under pressure sufficiently to partially condense it; 
 (2) said first dividing means is connected to said first cooling means to receive said partially condensed gas stream and divide it into said first stream and said second stream; and 
 (3) said separating means is connected to said first dividing means to receive said second stream and separate it into said vapor stream and said at least one liquid stream. 
 
     
     
         19 . The improvement according to  claim 17  wherein
 (1) a combining means is connected to said first dividing means and said separating means to receive said first stream and at least a portion of said at least one liquid stream and form a combined stream; 
 (2) said second cooling means is connected to said combining means to receive said combined stream and cool it sufficiently to substantially condense it; 
 (3) said first expansion means is connected to said second cooling means to receive said substantially condensed combined stream and expand it to said lower pressure, said first expansion means being further connected to said distillation column to supply said expanded substantially condensed combined stream to said distillation column at said upper mid-column feed position; and 
 (4) said fourth expansion means is connected to said separating means to receive any remaining portion of said at least one liquid stream and expand it to said lower pressure, said fourth expansion means being further connected to said distillation column to supply said expanded liquid stream to said distillation column at said lower mid-column feed position. 
 
     
     
         20 . The improvement according to  claim 18  wherein
 (1) a combining means is connected to said first dividing means and said separating means to receive said first stream and at least a portion of said at least one liquid stream and form a combined stream; 
 (2) said second cooling means is connected to said combining means to receive said combined stream and cool it sufficiently to substantially condense it; 
 (3) said first expansion means is connected to said second cooling means to receive said substantially condensed combined stream and expand it to said lower pressure, said first expansion means being further connected to said distillation column to supply said expanded substantially condensed combined stream to said distillation column at said upper mid-column feed position; and 
 (4) said fourth expansion means is connected to said separating means to receive any remaining portion of said at least one liquid stream and expand it to said lower pressure, said fourth expansion means being further connected to said distillation column to supply said expanded liquid stream to said distillation column at said lower mid-column feed position. 
 
     
     
         21 . The improvement according to  claim 13  or  14  wherein a heating means is connected to said fourth expansion means to receive said expanded said at least one liquid stream and heat it, said heating means being further connected to said distillation column to supply said heated expanded said at least one liquid stream to said distillation column at said lower mid-column feed point. 
     
     
         22 . The improvement according to  claim 15  or  16  wherein a heating means is connected to said fourth expansion means to receive said expanded said at least a portion of said at least one liquid stream and heat it, said heating means being further connected to said distillation column to supply said heated expanded said at least a portion of said at least one liquid stream to said distillation column at said lower mid-column feed point. 
     
     
         23 . The improvement according to  claim 17  or  18  wherein a heating means is connected to said fourth expansion means to receive said expanded said at least one liquid stream and heat it, said heating means being further connected to said distillation column to supply said heated expanded said at least one liquid stream to said distillation column at said lower mid-column feed point. 
     
     
         24 . The improvement according to  claim 19  or  20  wherein a heating means is connected to said fourth expansion means to receive said expanded said at least a portion of said at least one liquid stream and heat it, said heating means being further connected to said distillation column to supply said heated expanded said at least a portion of said at least one liquid stream to said distillation column at said lower mid-column feed point.