Hydrocarbon gas processing

• US 5,555,748 A
• Filed: 06/07/1995
• Issued: 09/17/1996
• Est. Priority Date: 06/07/1995
• Status: Expired due to Term

• Current Assignee: UOP Llc (Honeywell International Inc.)
• Original Assignee: Elcor Corporation
• Inventors: Hudson, Hank M., Wilkinson, John D., Pierce, Michael C., Campbell, Roy E.
• Primary Examiner(s): KILNER, CHRISTOPHER B
• Application Number:
  US08/477,444
• Time in Patent Office: 468 Days
• Field of Search: 62/621, 62/620, 62/630
• US Class Current: 62/621
• CPC Class Codes: F25J 2200/02 in a single pressure main column system
• CPC Class Codes: F25J 2200/70 Refluxing the column with a condensed part of the feed stream, i.e. fractionator top is stripped or self-rectified
• CPC Class Codes: F25J 2205/04 in the feed line, i.e. upstream of the fractionation step
• CPC Class Codes: F25J 2210/06 Splitting of the feed stream, e.g. for treating or cooling in different ways
• CPC Class Codes: F25J 2210/12 Refinery or petrochemical off-gas
• CPC Class Codes: F25J 2235/60 the fluid being (a mixture of) hydrocarbons
• CPC Class Codes: F25J 2240/02 Expansion of a process fluid in a work-extracting turbine (i.e. isentropic expansion), e.g. of the feed stream
• CPC Class Codes: F25J 2270/90 External refrigeration, e.g. conventional closed-loop mechanical refrigeration unit using Freon or NH3, unspecified external refrigeration
• CPC Class Codes: F25J 3/0209 Natural gas or substitute natural gas
• CPC Class Codes: F25J 3/0219 Refinery gas, cracking gas, coke oven gas, gaseous mixtures containing aliphatic unsaturated CnHm or gaseous mixtures of undefined nature
• CPC Class Codes: F25J 3/0233 separation of CnHm with 1 carbon atom or more
• CPC Class Codes: F25J 3/0238 separation of CnHm with 2 carbon atoms or more
• CPC Class Codes: F25J 3/0242 separation of CnHm with 3 carbon atoms or more

Abstract

A process for the recovery of ethane, ethylene, propane, propylene and heavier hydrocarbon components from a hydrocarbon gas stream is disclosed. The stream is cooled to partially condense it, then separated to provide a first vapor stream and a first condensed stream. The first vapor stream is divided into first and second streams, then the first stream is combined with the first condensed stream. The combined stream is cooled and expanded to an intermediate pressure to partially condense it, then separated to provide a second vapor stream and a second condensed stream. The second vapor stream is cooled at the intermediate pressure to condense substantially all of it and is thereafter expanded to the fractionation tower pressure and supplied to the fractionation tower at a top feed position. The second condensed stream is subcooled at the intermediate pressure, expanded to the tower pressure, and is supplied to the column at a first mid-column feed position. The second stream is expanded to the tower pressure and is then supplied to the column at a second mid-column feed position. The quantities and temperatures of the feeds to the column are effective to maintain the column overhead temperature at a temperature whereby the major portion of the desired components is recovered. In an alternative embodiment, the combined stream is cooled at essentially inlet pressure to partially condense it, then separated at pressure to provide the second vapor stream and the second condensed stream.

Claims

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 containing a major portion of said methane and a relatively less volatile fraction containing at least a major portion of said C₃ 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 fractionated at said lower pressure whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction;

the improvement wherein said gas stream is cooled sufficiently to partially condense it; and

(1) said partially condensed gas stream is separated thereby to provide a first vapor stream and a first condensed stream;

(2) said first vapor stream is thereafter divided into gaseous first and second streams;

(3) said gaseous first stream is combined with at least a portion of said first condensed stream to form a combined stream;

(4) said combined stream is cooled and expanded to an intermediate pressure whereby it is partially condensed;

(5) said expanded partially condensed combined stream is separated at said intermediate pressure thereby to provide a second vapor stream and a second condensed stream;

(6) said second vapor stream is further cooled at said intermediate pressure to condense substantially all of it, expanded to said lower pressure, and thereafter supplied at a top feed position to a distillation column in a lower region of a fractionation tower;

(7) said second condensed stream is further cooled at said intermediate pressure, expanded to said lower pressure, and thereafter supplied to said distillation column at a first mid-column feed position;

(8) said gaseous second stream is expanded to said lower pressure and thereafter supplied to said distillation column at a second mid-column feed position; and

(9) the quantities and temperatures of said feed streams to the column are effective to maintain the tower overhead temperature at a temperature whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction.

17. The improvement according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or 16 wherein the quantities and temperatures of said feed streams to the column are effective to maintain the tower overhead temperature at a temperature whereby at least a major portion of said C₂ components, C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction.

2. 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 containing a major portion of said methane and a relatively less volatile fraction containing at least a major portion of said C₃ 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 fractionated at said lower pressure whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction;

the improvement wherein prior to cooling, said gas stream is divided into gaseous first and second streams; and

(1) said gaseous second stream is cooled sufficiently to partially condense it;

(2) said partially condensed second stream is separated thereby to provide a first vapor stream and a first condensed stream;

(3) said gaseous first stream is cooled and then combined with at least a portion of said first condensed stream to form a combined stream;

(4) said combined stream is cooled and expanded to an intermediate pressure whereby it is partially condensed;

(5) said expanded partially condensed combined stream is separated at said intermediate pressure thereby to provide a second vapor stream and a second condensed stream;

(6) said second vapor stream is further cooled at said intermediate pressure to condense substantially all of it, expanded to said lower pressure, and thereafter supplied at a top feed position to a distillation column in a lower region of a fractionation tower;

(7) said second condensed stream is further cooled at said intermediate pressure, expanded to said lower pressure, and thereafter supplied to said distillation column at a first mid-column feed position;

(8) said first vapor stream is expanded to said lower pressure and thereafter supplied to said distillation column at a second mid-column feed position; and

(9) the quantities and temperatures of said feed streams to the column are effective to maintain the tower overhead temperature at a temperature whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction.

3. 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 containing a major portion of said methane and a relatively less volatile fraction containing at least a major portion of said C₃ 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 fractionated at said lower pressure whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction;

the improvement wherein following cooling, said cooled stream is divided into first and second streams; and

(1) said second stream is cooled sufficiently to partially condense it;

(2) said partially condensed second stream is separated thereby to provide a first vapor stream and a first condensed stream;

(3) said first stream is combined with at least a portion of said first condensed stream to form a combined stream;

(4) said combined stream is cooled and expanded to an intermediate pressure whereby it is partially condensed;

(5) said expanded partially condensed combined stream is separated at said intermediate pressure thereby to provide a second vapor stream and a second condensed stream;

(6) said second vapor stream is further cooled at said intermediate pressure to condense substantially all of it, expanded to said lower pressure, and thereafter supplied at a top feed position to a distillation column in a lower region of a fractionation tower;

(7) said second condensed stream is further cooled at said intermediate pressure, expanded to said lower pressure, and thereafter supplied to said distillation column at a first mid-column feed position;

(8) said first vapor stream is expanded to said lower pressure and thereafter supplied to said distillation column at a second mid-column feed position; and

(9) the quantities and temperatures of said feed streams to the column are effective to maintain the tower overhead temperature at a temperature whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction.

4. 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 containing a major portion of said methane and a relatively less volatile fraction containing at least a major portion of said C₃ 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 fractionated at said lower pressure whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction;

the improvement wherein said gas stream is cooled sufficiently to partially condense it; and

(1) said partially condensed gas stream is separated thereby to provide a first vapor stream and a first condensed stream;

(2) said first vapor stream is thereafter divided into gaseous first and second streams;

(3) said gaseous first stream is cooled and expanded to an intermediate pressure whereby it is partially condensed;

(4) said expanded partially condensed first stream is separated at said intermediate pressure thereby to provide a second vapor stream and a second condensed stream;

(5) said second vapor stream is further cooled at said intermediate pressure to condense substantially all of it, expanded to said lower pressure, and thereafter supplied at a top feed position to a distillation column in a lower region of a fractionation tower;

(6) said second condensed stream is further cooled at said intermediate pressure, expanded to said lower pressure, and thereafter supplied to said distillation column at a first mid-column feed position;

(7) said gaseous second stream is expanded to said lower pressure and thereafter supplied to said distillation column at a second mid-column feed position;

(8) at least a portion of said first condensed stream is expanded to said lower pressure and thereafter supplied to said distillation column at a third mid-column feed position; and

(9) the quantities and temperatures of said feed streams to the column are effective to maintain the tower overhead temperature at a temperature whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction.

5. 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 containing a major portion of said methane and a relatively less volatile fraction containing at least a major portion of said C₃ 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 fractionated at said lower pressure whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction;

the improvement wherein prior to cooling, said gas stream is divided into gaseous first and second streams; and

(1) said gaseous first stream is cooled and expanded to an intermediate pressure whereby it is partially condensed;

(2) said expanded partially condensed first stream is separated at said intermediate pressure thereby to provide a first vapor stream and a first condensed stream;

(3) said first vapor stream is further cooled at said intermediate pressure to condense substantially all of it, expanded to said lower pressure, and thereafter supplied at a top feed position to a distillation column in a lower region of a fractionation tower;

(4) said first condensed stream is further cooled at said intermediate pressure, expanded to said lower pressure, and thereafter supplied to said distillation column at a first mid-column feed position;

(5) said gaseous second stream is cooled sufficiently to partially condense it;

(6) said partially condensed second stream is separated thereby to provide a second vapor stream and a second condensed stream;

(7) said second vapor stream is expanded to said lower pressure and thereafter supplied to said distillation column at a second mid-column feed position;

(8) at least a portion of said second condensed stream is expanded to said lower pressure and thereafter supplied to said distillation column at a third mid-column feed position; and

(9) the quantities and temperatures of said feed streams to the column are effective to maintain the tower overhead temperature at a temperature whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction.

6. 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 containing a major portion of said methane and a relatively less volatile fraction containing at least a major portion of said C₃ 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 fractionated at said lower pressure whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction;

the improvement wherein following cooling, said cooled stream is divided into first and second streams; and

(1) said first stream is cooled and expanded to an intermediate pressure whereby it is partially condensed;

(2) said expanded partially condensed first stream is separated at said intermediate pressure thereby to provide a first vapor stream and a first condensed stream;

(3) said first vapor stream is further cooled at said intermediate pressure to condense substantially all of it, expanded to said lower pressure, and thereafter supplied at a top feed position to a distillation column in a lower region of a fractionation tower;

(4) said first condensed stream is further cooled at said intermediate pressure, expanded to said lower pressure, and thereafter supplied to said distillation column at a first mid-column feed position;

(5) said second stream is cooled sufficiently to partially condense it;

(6) said partially condensed second stream is separated thereby to provide a second vapor stream and a second condensed stream;

(7) said second vapor stream is expanded to said lower pressure and thereafter supplied to said distillation column at a second mid-column feed position;

(8) at least a portion of said second condensed stream is expanded to said lower pressure and thereafter supplied to said distillation column at a third mid-column feed position; and

(9) the quantities and temperatures of said feed streams to the column are effective to maintain the tower overhead temperature at a temperature whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction.

7. 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 containing a major portion of said methane and a relatively less volatile fraction containing at least a major portion of said C₃ 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 fractionated at said lower pressure whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction;

the improvement wherein following cooling, said cooled stream is divided into first and second streams; and

(1) said first stream is cooled and expanded to an intermediate pressure whereby it is partially condensed;

(2) said expanded partially condensed first stream is separated at said intermediate pressure thereby to provide a vapor stream and a condensed stream;

(3) said vapor stream is further cooled at said intermediate pressure to condense substantially all of it, expanded to said lower pressure, and thereafter supplied at a top feed position to a distillation column in a lower region of a fractionation tower;

(4) said condensed stream is further cooled at said intermediate pressure, expanded to said lower pressure, and thereafter supplied to said distillation column at a first mid-column feed position;

(5) said second stream is expanded to said lower pressure and there after supplied to said distillation column at a second mid-column feed position; and

(6) the quantities and temperatures of said feed streams to the column are effective to maintain the tower overhead temperature at a temperature whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction.

8. 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 containing a major portion of said methane and a relatively less volatile fraction containing at least a major portion of said C₃ 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 fractionated at said lower pressure whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction;

the improvement wherein prior to cooling, said gas stream is divided into gaseous first and second streams; and

(1) said gaseous first stream is cooled and expanded to an intermediate pressure whereby it is partially condensed;

(2) said expanded partially condensed first stream is separated at said intermediate pressure thereby to provide a vapor stream and a condensed stream;

(3) said vapor stream is further cooled at said intermediate pressure to condense substantially all of it, expanded to said lower pressure, and thereafter supplied at a top feed position to a distillation column in a lower region of a fractionation tower;

(4) said condensed stream is further cooled at said intermediate pressure, expanded to said lower pressure, and thereafter supplied to said distillation column at a first mid-column feed position;

(5) said gaseous second stream is cooled, then expanded to said lower pressure and thereafter supplied to said distillation column at a second mid-column feed position; and

(6) the quantities and temperatures of said feed streams to the column are effective to maintain the tower overhead temperature at a temperature whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction.

9. 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 containing a major portion of said methane and a relatively less volatile fraction containing at least a major portion of said C₃ 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 fractionated at said lower pressure whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction;

the improvement wherein said gas stream is cooled sufficiently to partially condense it; and

(1) said partially condensed gas stream is separated thereby to provide a first vapor stream and a first condensed stream;

(2) said first vapor stream is thereafter divided into gaseous first and second streams;

(3) said gaseous first stream is combined with at least a portion of said first condensed stream to form a combined stream;

(4) said combined stream is cooled whereby it is partially condensed;

(5) said cooled partially condensed combined stream is separated under pressure thereby to provide a second vapor stream and a second condensed stream;

(6) said second vapor stream is further cooled under pressure to condense substantially all of it, expanded to said lower pressure, and thereafter supplied at a top feed position to a distillation column in a lower region of a fractionation tower;

(7) said second condensed stream is further cooled under pressure, expanded to said lower pressure, and thereafter supplied to said distillation column at a first mid-column feed position;

(8) said gaseous second stream is expanded to said lower pressure and thereafter supplied to said distillation column at a second mid-column feed position; and

(9) the quantities and temperatures of said feed streams to the column are effective to maintain the tower overhead temperature at a temperature whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction.

10. 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 containing a major portion of said methane and a relatively less volatile fraction containing at least a major portion of said C₃ 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 fractionated at said lower pressure whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction;

the improvement wherein prior to cooling, said gas stream is divided into gaseous first and second streams; and

(1) said gaseous second stream is cooled sufficiently to partially condense it;

(2) said partially condensed second stream is separated thereby to provide a first vapor stream and a first condensed stream;

(3) said gaseous first stream is cooled and then combined with at least a portion of said first condensed stream to form a combined stream;

(4) said combined stream is cooled whereby it is partially condensed;

(5) said cooled partially condensed combined stream is separated under pressure thereby to provide a second vapor stream and a second condensed stream;

(6) said second vapor stream is further cooled under pressure to condense substantially all of it, expanded to said lower pressure, and thereafter supplied at a top feed position to a distillation column in a lower region of a fractionation tower;

(7) said second condensed stream is further cooled under pressure, expanded to said lower pressure, and thereafter supplied to said distillation column at a first mid-column feed position;

(8) said first vapor stream is expanded to said lower pressure and thereafter supplied to said distillation column at a second mid-column feed position; and

(9) the quantities and temperatures of said feed streams to the column are effective to maintain the tower overhead temperature at a temperature whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction.

11. 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 containing a major portion of said methane and a relatively less volatile fraction containing at least a major portion of said C₃ 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 fractionated at said lower pressure whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction;

the improvement wherein following cooling, said cooled stream is divided into first and second streams; and

(1) said second stream is cooled sufficiently to partially condense it;

(2) said partially condensed second stream is separated thereby to provide a first vapor stream and a first condensed stream;

(3) said first stream is combined with at least a portion of said first condensed stream to form a combined stream;

(4) said combined stream is cooled whereby it is partially condensed;

(5) said cooled partially condensed combined stream is separated under pressure thereby to provide a second vapor stream and a second condensed stream;

(6) said second vapor stream is further cooled under pressure to condense substantially all of it, expanded to said lower pressure, and thereafter supplied at a top feed position to a distillation column in a lower region of a fractionation tower;

(7) said second condensed stream is further cooled under pressure, expanded to said lower pressure, and thereafter supplied to said distillation column at a first mid-column feed position;

(8) said first vapor stream is expanded to said lower pressure and thereafter supplied to said distillation column at a second mid-column feed position; and

(9) the quantities and temperatures of said feed streams to the column are effective to maintain the tower overhead temperature at a temperature whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction.

12. 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 containing a major portion of said methane and a relatively less volatile fraction containing at least a major portion of said C₃ 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 fractionated at said lower pressure whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction;

the improvement wherein said gas stream is cooled sufficiently to partially condense it; and

(1) said partially condensed gas stream is separated thereby to provide a first vapor stream and a first condensed stream;

(2) said first vapor stream is thereafter divided into gaseous first and second streams;

(3) said gaseous first stream is cooled whereby it is partially condensed;

(4) said cooled partially condensed first stream is separated under pressure thereby to provide a second vapor stream and a second condensed stream;

(5) said second vapor stream is further cooled under pressure to condense substantially all of it, expanded to said lower pressure, and thereafter supplied at a top feed position to a distillation column in a lower region of a fractionation tower;

(6) said second condensed stream is further cooled under pressure, expanded to said lower pressure, and thereafter supplied to said distillation column at a first mid-column feed position;

(7) said gaseous second stream is expanded to said lower pressure and thereafter supplied to said distillation column at a second mid-column feed position;

(8) at least a portion of said first condensed stream is expanded to said lower pressure and thereafter supplied to said distillation column at a third mid-column feed position; and

(9) the quantities and temperatures of said feed streams to the column are effective to maintain the tower overhead temperature at a temperature whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction.

13. 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 containing a major portion of said methane and a relatively less volatile fraction containing at least a major portion of said C₃ 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 fractionated at said lower pressure whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction;

the improvement wherein prior to cooling, said gas stream is divided into gaseous first and second streams; and

(1) said gaseous first stream is cooled whereby it is partially condensed;

(2) said cooled partially condensed first stream is separated under pressure thereby to provide a first vapor stream and a first condensed stream;

(3) said first vapor stream is further cooled under pressure to condense substantially all of it, expanded to said lower pressure, and thereafter supplied at a top feed position to a distillation column in a lower region of a fractionation tower;

(4) said first condensed stream is further cooled under pressure, expanded to said lower pressure, and thereafter supplied to said distillation column at a first mid-column feed position;

(5) said gaseous second stream is cooled sufficiently to partially condense it;

(6) said partially condensed second stream is separated thereby to provide a second vapor stream and a second condensed stream;

(7) said second vapor stream is expanded to said lower pressure and thereafter supplied to said distillation column at a second mid-column feed position;

(8) at least a portion of said second condensed stream is expanded to said lower pressure and thereafter supplied to said distillation column at a third mid-column feed position; and

(9) the quantities and temperatures of said feed streams to the column are effective to maintain the tower overhead temperature at a temperature whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction.

14. 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 containing a major portion of said methane and a relatively less volatile fraction containing at least a major portion of said C₃ 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 fractionated at said lower pressure whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction;

the improvement wherein following cooling, said cooled stream is divided into first and second streams; and

(1) said first stream is cooled whereby it is partially condensed;

(2) said cooled partially condensed first stream is separated under pressure thereby to provide a first vapor stream and a first condensed stream;

(3) said first vapor stream is further cooled under pressure to condense substantially all of it, expanded to said lower pressure, and thereafter supplied at a top feed position to a distillation column in a lower region of a fractionation tower;

(4) said first condensed stream is further cooled under pressure, expanded to said lower pressure, and thereafter supplied to said distillation column at a first mid-column feed position;

(5) said second stream is cooled sufficiently to partially condense it;

(6) said partially condensed second stream is separated thereby to provide a second vapor stream and a second condensed stream;

(7) said second vapor stream is expanded to said lower pressure and thereafter supplied to said distillation column at a second mid-column feed position;

(8) at least a portion of said second condensed stream is expanded to said lower pressure and thereafter supplied to said distillation column at a third mid-column feed position; and

(9) the quantities and temperatures of said feed streams to the column are effective to maintain the tower overhead temperature at a temperature whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction.

15. 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 containing a major portion of said methane and a relatively less volatile fraction containing at least a major portion of said C₃ 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 fractionated at said lower pressure whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction;

the improvement wherein following cooling, said cooled stream is divided into first and second streams; and

(1) said first stream is cooled whereby it is partially condensed;

(2) said cooled partially condensed first stream is separated under pressure thereby to provide a vapor stream and a condensed stream;

(3) said vapor stream is further cooled under pressure to condense substantially all of it, expanded to said lower pressure, and thereafter supplied at a top feed position to a distillation column in a lower region of a fractionation tower;

(4) said condensed stream is further cooled under pressure, expanded to said lower pressure, and thereafter supplied to said distillation column at a first mid-column feed position;

(5) said second stream is expanded to said lower pressure and thereafter supplied to said distillation column at a second mid-column feed position; and

(6) the quantities and temperatures of said feed streams to the column are effective to maintain the tower overhead temperature at a temperature whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction.

16. 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 containing a major portion of said methane and a relatively less volatile fraction containing at least a major portion of said C₃ 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 fractionated at said lower pressure whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction;

the improvement wherein prior to cooling, said gas stream is divided into gaseous first and second streams; and

(1) said gaseous first stream is cooled whereby it is partially condensed;

(2) said cooled partially condensed first stream is separated under pressure thereby to provide a vapor stream and a condensed stream;

(3) said vapor stream is further cooled under pressure to condense substantially all of it, expanded to said lower pressure, and thereafter supplied at a top feed position to a distillation column in a lower region of a fractionation tower;

(4) said condensed stream is further cooled under pressure, expanded to said lower pressure, and thereafter supplied to said distillation column at a first mid-column feed position;

(5) said gaseous second stream is cooled, then expanded to said lower pressure and thereafter supplied to said distillation column at a second mid-column feed position; and

(6) the quantities and temperatures of said feed streams to the column are effective to maintain the tower overhead temperature at a temperature whereby at least a major portion of said C₃ components and heavier hydrocarbon components is recovered in said relatively less volatile fraction.