Hydrocarbon gas processing

Abstract

A process and an apparatus are disclosed for the recovery of components from a hydrocarbon gas stream containing significant quantities of components more volatile than methane (hydrogen, nitrogen, etc.). The gas stream is partially condensed, then the remaining vapor is expanded to lower pressure and supplied to a fractionation tower at a mid-column feed position. The condensed liquid is cooled and divided into two portions. The first portion is expanded to tower pressure, heated by cooling the liquid, and supplied to the tower at a lower column feed position. The second portion is expanded to tower pressure and supplied to the tower at an upper mid-column feed position. A distillation vapor stream is withdrawn from the fractionation tower below the mid-column feed position and is heated, compressed to higher pressure, and cooled to substantial condensation before it is expanded and supplied to the tower as its top feed.

We claim: 
     
         1 . A process for the separation of a gas stream, containing methane and components more volatile than methane, C 2  components, C 3  components, and heavier hydrocarbon components, into (i) a volatile residue gas fraction containing a major portion of said methane and components more volatile than methane and (ii) a relatively less volatile fraction containing a major portion of said C 2  components, C 3  components, and heavier hydrocarbon components, wherein
 (1) said gas stream is cooled under pressure sufficiently to form a partially condensed gas stream;   (2) said partially condensed gas stream is separated thereby to provide a vapor stream and at least one liquid stream;   (3) said vapor stream is expanded to lower pressure to form an expanded vapor stream, whereupon said expanded vapor stream is supplied to a distillation column at a mid-column feed position;   (4) said at least one liquid stream is further cooled to form a cooled liquid stream;   (5) said cooled liquid stream is divided into first and second portions;   (6) said first portion is expanded to said lower pressure to form an expanded first portion;   (7) said expanded first portion is heated to form a heated expanded first portion, thereby to supply at least a portion of the cooling of step (4), whereupon said heated expanded first portion is supplied to said distillation column at a lower mid-column feed position below said mid-column feed position;   (8) said second portion is expanded to said lower pressure to form an expanded second portion, whereupon said expanded second portion is supplied to said distillation column at an upper mid-column feed position above said mid-column feed position;   (9) a distillation vapor stream is withdrawn from a region of said distillation column below said mid-column feed position and above said lower mid-column feed position, and is heated to form a heated distillation vapor stream;   (10) said heated distillation vapor stream is compressed to a higher pressure to form a compressed stream;   (11) said compressed stream is cooled and substantially condensed to form a substantially condensed stream, thereby to supply at least a portion of the heating of step (9);   (12) said substantially condensed stream is expanded to said lower pressure to form an expanded substantially condensed stream, whereupon said expanded substantially condensed stream is supplied to said distillation column at a top feed position;   (13) said expanded vapor stream, said heated expanded first portion, said expanded second portion, and said expanded substantially condensed stream are fractionated in said distillation column at said lower pressure to form an overhead vapor stream and said relatively less volatile fraction;   (14) said overhead vapor stream is heated to form said volatile residue gas fraction, thereby to supply at least a portion of the cooling of step (11); and   (15) 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 portion of said C 2  components, C 3  components, and heavier hydrocarbon components is recovered in said relatively less volatile fraction.   
     
     
         2 . The process according to  claim 1  wherein
 (a) said expanded vapor stream is supplied at a first lower column feed position to a contacting and separating device that produces said overhead vapor stream and a bottom liquid stream, whereupon said bottom liquid stream is supplied to said distillation column at said top feed position; 
 (b) a first distillation vapor stream is withdrawn from an upper region of said distillation column and is divided into a second distillation vapor stream and a third distillation vapor stream; 
 (c) said second distillation vapor stream is supplied to said contacting and separating device at a second lower column feed position; 
 (d) said third distillation vapor stream is heated to form a heated third distillation vapor stream; 
 (e) said heated third distillation vapor stream is compressed to said higher pressure to form said compressed stream; 
 (f) said expanded substantially condensed stream is supplied to said contacting and separating device at a top feed position; 
 (g) said expanded second portion is supplied to said contacting and separating device at a mid-column feed position; and 
 (h) 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 portion of said C 2  components, C 3  components, and heavier hydrocarbon components is recovered in said relatively less volatile fraction. 
 
     
     
         3 . An apparatus for the separation of a gas stream, containing methane and components more volatile than methane, C 2  components, C 3  components, and heavier hydrocarbon components, into (i) a volatile residue gas fraction containing a major portion of said methane and components more volatile than methane and (ii) a relatively less volatile fraction containing a major portion of said C 2  components, C 3  components, and heavier hydrocarbon components comprising
 (1) first cooling means connected to receive said gas stream and cool said gas stream under pressure sufficiently to form a partially condensed gas stream;   (2) separating means connected to said first cooling means to receive said partially condensed gas stream and separate said partially condensed gas stream into a vapor stream and at least one liquid stream;   (3) first expansion means connected to said separating means to receive said vapor stream and expand said vapor stream to lower pressure to form an expanded vapor stream;   (4) a distillation column connected to said first expansion means to receive said expanded vapor stream at a mid-column feed position;   (5) second cooling means connected to said separating means to receive said at least one liquid stream and further cool said at least one liquid stream to form a cooled liquid stream;   (6) dividing means connected to said second cooling means to receive said cooled liquid stream and divide said cooled liquid stream into first and second portions;   (7) second expansion means connected to said dividing means to receive said first portion and expand said first portion to said lower pressure to form an expanded first portion;   (8) first heating means connected to said second expansion means to receive said expanded first portion and heat said expanded first portion to form a heated expanded first portion, thereby to supply at least a portion of the cooling of step (5), said first heating means being further connected to said distillation column to supply said heated expanded first portion to said distillation column at a lower mid-column feed position below said mid-column feed position;   (9) third expansion means connected to said dividing means to receive said second portion and expand said second portion to said lower pressure to form an expanded second portion, said third expansion means being further connected to said distillation column to supply said expanded second portion to said distillation column at an upper mid-column feed position above said mid-column feed position;   (10) vapor withdrawing means connected to said distillation column to receive a distillation vapor stream from a region of said distillation column below said mid-column feed position and above said lower mid-column feed position;   (11) second heating means connected to said vapor withdrawing means to receive said distillation vapor stream and heat said distillation vapor stream to produce a heated distillation vapor stream;   (12) compressing means connected to said second heating means to receive said heated distillation vapor stream and compress said heated distillation stream to a higher pressure to form a compressed stream;   (13) third cooling means connected to said compressing means to receive said compressed stream and cool and substantially condense said compressed stream to form a substantially condensed stream, thereby to supply at least a portion of the heating of step (11);   (14) fourth expansion means connected to said third cooling means to receive said substantially condensed stream and expand said substantially condensed stream to said lower pressure to form an expanded substantially condensed stream, said fourth expansion means being further connected to said distillation column to supply said expanded substantially condensed stream to said distillation column at a top feed position;   (15) said distillation column adapted to fractionate said expanded vapor stream, said heated expanded first portion, said expanded second portion, and said expanded substantially condensed stream at said lower pressure to form an overhead stream and said relatively less volatile fraction;   (16) third heating means connected to said distillation column to receive said overhead vapor stream and heat said overhead vapor stream to form said volatile residue gas fraction, thereby to supply at least a portion of the cooling of step (13); and   (17) 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 portion of said C 2  components, C 3  components, and heavier hydrocarbon components is recovered in said relatively less volatile fraction.   
     
     
         4 . The apparatus according to  claim 3  wherein
 (a) said first expansion means is connected to a contacting and separating means to supply said expanded vapor stream to said contacting and separating means at a first lower column feed position, said contacting and separating means being adapted to produce said overhead vapor stream and a bottom liquid stream; 
 (b) said third heating means is adapted to connect to said contacting and separating means to receive said overhead stream; 
 (c) said distillation column is connected to said contacting and separating means to receive said bottom liquid stream at said top feed position, said distillation column being adapted to fractionate said bottom liquid stream into a first distillation vapor stream and said relatively less volatile fraction; 
 (d) a dividing means is connected to said distillation column to receive said first distillation vapor stream and divide said distillation vapor stream into a second distillation vapor stream and a third distillation vapor stream; 
 (e) said contacting and separating means is further connected to said dividing means to receive said second distillation vapor stream at a second lower column feed position; 
 (f) said second heating means is adapted to connect to said dividing means to receive said third distillation vapor stream and heat said third distillation vapor stream to form a heated third distillation vapor stream; 
 (g) said compressing means is adapted to receive said heated third distillation vapor stream and compress said heated third distillation vapor stream to said higher pressure to form said compressed stream; 
 (h) said contacting and separating means is further connected to said third expansion means to receive said expanded second portion and supply said expanded second portion to said contacting and separating means at a mid-column feed position; 
 (i) said contacting and separating means is further connected to said fourth expansion means to receive said expanded substantially condensed stream and supply said expanded substantially condensed stream to said contacting and separating means at a top feed position; 
 
       and
 (j) 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 portion of said C 2  components, C 3  components, and heavier hydrocarbon components is recovered in said relatively less volatile fraction.