Hydrocarbon gas processing

• US 5,881,569 A
• Filed: 08/20/1997
• Issued: 03/16/1999
• Est. Priority Date: 05/07/1997
• Status: Expired due to Term

• Current Assignee: Ortloff Enigneers, Ltd.
• Original Assignee: Elcor Corporation
• Inventors: Cueller, Kyle T., Campbell, deceased, Roy E., Hudson, Hank M., Wilkinson, John D.
• Primary Examiner(s): Capossela, Ronald C.
• Application Number:
  US08/915,065
• Time in Patent Office: 573 Days
• Field of Search: 62/621, 62/630, 62/935
• 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 2200/76 Refluxing the column with condensed overhead gas being cycled in a quasi-closed loop refrigeration cycle
• 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 2230/30 Compression of the feed stream
• 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 2245/02 Recycle of a stream in general, e.g. a by-pass stream
• CPC Class Codes: F25J 2270/02 Internal refrigeration with liquid vaporising loop
• CPC Class Codes: F25J 2270/12 External refrigeration with liquid vaporising loop
• CPC Class Codes: F25J 2270/60 Closed external refrigeration cycle with single component refrigerant [SCR], e.g. C1-, C2- or C3-hydrocarbons
• 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 divided into first and second streams, and the second stream is expanded to the fractionation tower pressure and supplied to the column at a mid-column feed position. A recycle stream is withdrawn from the tower overhead after it has been warmed and compressed, and is combined with the first stream. The combined stream is cooled to condense substantially all of it, and is thereafter expanded to the fractionation tower pressure and supplied to the fractionation tower at a top column feed position. The pressure of the compressed recycle stream and 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.

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 and a relatively less volatile fraction containing said C₂ components, C₃ components and heavier hydrocarbon components or 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 the components of said relatively less volatile fraction are recovered;

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

(1) a distillation stream is withdrawn from an upper region of a fractionation tower and is warmed;

(2) said warmed distillation stream is compressed to higher pressure and thereafter divided into said volatile residue gas fraction and a compressed recycle stream;

(3) said compressed recycle stream is combined with said gaseous first stream to form a combined stream;

(4) said combined stream is cooled to condense substantially all of it;

(5) said substantially condensed combined stream is expanded to said lower pressure and supplied to said fractionation tower at a top feed position;

(6) said gaseous second stream is cooled under pressure sufficiently to partially condense it;

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

(8) said vapor stream is expanded to said lower pressure and supplied at a first mid-column feed position to a distillation column in a lower region of said fractionation tower;

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

(10) the quantity and pressure of said combined stream and the quantities and temperatures of said feed streams to the column are effective to maintain tower overhead temperature at a temperature whereby the major portions of the components in said relatively less volatile fraction are recovered.

8. The improvement according to claims 1, 2, 3, 4, 5, 6 or 7 wherein

(a) said warmed distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to compression;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

9. The improvement according to claims 1, 2, 3, 4, 5, 6 or 7 wherein

(a) said distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to heating;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

13. The improvement according to claims 1, 4 or 7 wherein

(a) said condensed stream is cooled and then divided into first and second liquid portions prior to said expansion;

(b) said first liquid portion is expanded to said lower pressure and supplied to said column at a mid-column feed position; and

(c) said second liquid portion is expanded to said lower pressure and supplied to said column at a higher mid-column feed position.

14. The improvement according to claim 13 wherein

(a) said warmed distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to compression;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

15. The improvement according to claim 13 wherein

(a) said distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to heating;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

16. The improvement according to claim 13 wherein said expanded first liquid portion is heated prior to being supplied to said distillation column.

17. The improvement according to claim 16 wherein

(a) said warmed distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to compression;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

18. The improvement according to claim 16 wherein

(a) said distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to heating;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

19. The improvement according to claim 13 wherein said first liquid portion is expanded, directed in heat exchange relation with said condensed stream and is then supplied to said column at a mid-column feed position.

20. The improvement according to claim 19 wherein

(a) said warmed distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to compression;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

21. The improvement according to claim 19 wherein

(a) said distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to heating;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

22. The improvement according to claims 1, 2 or 7 wherein at least a portion of said vapor stream is heated after expansion to said lower pressure.

23. The improvement according to claim 22 wherein

(a) said warmed distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to compression;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

24. The improvement according to claim 22 wherein

(a) said distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to heating;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

28. The improvement according to claims 1, 4 or 7 wherein at least a portion of said expanded condensed stream is heated prior to being supplied to said distillation column.

29. The improvement according to claim 28 wherein

(a) said warmed distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to compression;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

30. The improvement according to claim 28 wherein

(a) said distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to heating;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

34. The improvement according to claims 1 or 7 wherein at least portions of said expanded vapor stream and said expanded condensed stream are combined to form a second combined stream, whereupon said second combined stream is supplied to said column at a mid-column feed position.

35. The improvement according to claim 34 wherein

(a) said warmed distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to compression;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

36. The improvement according to claim 34 wherein

(a) said distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to heating;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

46. The improvement according to claims 1 or 7 wherein

(a) said condensed stream is cooled and then divided into first and second liquid portions prior to said expansion;

(b) said first liquid portion is expanded to said lower pressure and supplied to said column at a mid-column feed position;

(c) said second liquid portion is expanded to said lower pressure and combined with at least a portion of said expanded vapor stream to form a second combined stream; and

(d) said second combined stream is supplied to said column at a higher mid-column feed position.

47. The improvement according to claim 46 wherein

(a) said warmed distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to compression;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

48. The improvement according to claim 46 wherein

(a) said distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to heating;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

49. The improvement according to claim 46 wherein said expanded first liquid portion is heated prior to being supplied to said distillation column.

50. The improvement according to claim 49 wherein

(a) said warmed distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to compression;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

51. The improvement according to claim 49 wherein

(a) said distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to heating;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

52. The improvement according to claim 46 wherein said first liquid portion is expanded, directed in heat exchange relation with said condensed stream and is then supplied to said column at a mid-column feed position.

53. The improvement according to claim 52 wherein

(a) said warmed distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to compression;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

54. The improvement according to claim 52 wherein

(a) said distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to heating;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

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 and a relatively less volatile fraction containing said C₂ components, C₃ components and heavier hydrocarbon components or 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 the components of said relatively less volatile fraction are recovered;

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 vapor stream and a condensed stream;

(2) a distillation stream is withdrawn from an upper region of a fractionation tower and is warmed;

(3) said warmed distillation stream is compressed to higher pressure and thereafter divided into said volatile residue gas fraction and a compressed recycle stream;

(4) said compressed recycle stream is combined with at least a portion of said condensed stream to form a combined stream;

(5) said combined stream is cooled to condense substantially all of it;

(6) said substantially condensed combined stream is expanded to said lower pressure and supplied to said fractionation tower at a top feed position;

(7) said vapor stream is expanded to said lower pressure and supplied at a mid-column feed position to a distillation column in a lower region of said fractionation tower;

(8) the quantity and pressure of said combined stream and the quantities and temperatures of said feed streams to the column are effective to maintain tower overhead temperature at a temperature whereby the major portions of the components in said relatively less volatile fraction are recovered.

10. The improvement according to claims 2 or 5 wherein at least a portion of said condensed stream is expanded to said lower pressure and then supplied to said distillation column at a second mid-column feed position.

11. The improvement according to claim 10 wherein

(a) said warmed distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to compression;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

12. The improvement according to claim 10 wherein

(a) said distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to heating;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

31. The improvement according to claims 2 or 5 wherein at least a portion of said condensed stream is expanded to said lower pressure, heated and then supplied to said distillation column at a second mid-column feed position.

32. The improvement according to claim 31 wherein

(a) said warmed distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to compression;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

33. The improvement according to claim 31 wherein

(a) said distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to heating;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

37. The improvement according to claim 2 wherein at least a portion of said condensed stream is expanded to said lower pressure and combined with at least a portion of said expanded vapor stream to form a second combined stream, whereupon said second combined stream is supplied to said column at a mid-column feed position.

38. The improvement according to claim 37 wherein

(a) said warmed distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to compression;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

39. The improvement according to claim 37 wherein

(a) said distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to heating;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

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 and a relatively less volatile fraction containing said C₂ components, C₃ components and heavier hydrocarbon components or 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 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) a distillation stream is withdrawn from an upper region of a fractionation tower and is warmed;

(2) said warmed distillation stream is compressed to higher pressure and thereafter divided into said volatile residue gas fraction and a compressed recycle stream;

(3) said compressed recycle stream is combined with said first stream to form a combined stream;

(4) said combined stream is cooled to condense substantially all of it;

(5) said substantially condensed combined stream is expanded to said lower pressure and supplied to said fractionation tower at a top feed position;

(6) said second stream is expanded to said lower pressure and supplied at a mid-column feed position to a distillation column in a lower region of said fractionation tower; and

(7) the quantity and pressure of said combined stream and the quantities and temperatures of said feed streams to the column are effective to maintain tower overhead temperature at a temperature whereby the major portions of the components in said relatively less volatile fraction are recovered.

25. The improvement according to claims 3, 4, 5 or 6 wherein at least a portion of said second stream is heated after expansion to said lower pressure.

26. The improvement according to claim 25 wherein

(a) said warmed distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to compression;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

27. The improvement according to claim 25 wherein

(a) said distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to heating;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

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 and a relatively less volatile fraction containing said C₂ components, C₃ components and heavier hydrocarbon components or 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 the components of said relatively less volatile fraction are recovered;

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 vapor stream and a condensed stream;

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

(3) a distillation stream is withdrawn from an upper region of a fractionation tower and is warmed;

(4) said warmed distillation stream is compressed to higher pressure and thereafter divided into said volatile residue gas fraction and a compressed recycle stream;

(5) said compressed recycle stream is combined with said gaseous first stream to form a combined stream;

(6) said combined stream is cooled to condense substantially all of it;

(7) said substantially condensed combined stream is expanded to said lower pressure and supplied to said fractionation tower at a top feed position;

(8) said gaseous second stream is expanded to said lower pressure and supplied at a first mid-column feed position to a distillation column in a lower region of said fractionation tower;

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

(10) the quantity and pressure of said combined stream and the quantities and temperatures of said feed streams to the column are effective to maintain tower overhead temperature at a temperature whereby the major portions of the components in said relatively less volatile fraction are recovered.

40. The improvement according to claim 4 wherein at least portions of said expanded second stream and said expanded condensed stream are combined to form a second combined stream, whereupon said second combined stream is supplied to said column at a mid-column feed position.

41. The improvement according to claim 40 wherein

(a) said warmed distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to compression;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

42. The improvement according to claim 40 wherein

(a) said distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to heating;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

55. The improvement according to claim 4 wherein

(a) said condensed stream is cooled and then divided into first and second liquid portions prior to said expansion;

(b) said first liquid portion is expanded to said lower pressure and supplied to said column at a mid-column feed position;

(c) said second liquid portion is expanded to said lower pressure and combined with at least a portion of said expanded second stream to form a second combined stream; and

(d) said second combined stream is supplied to said column at a higher mid-column feed position.

56. The improvement according to claim 55 wherein

(a) said warmed distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to compression;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

57. The improvement according to claim 55 wherein

(a) said distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to heating;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

58. The improvement according to claim 55 wherein said expanded first liquid portion is heated prior to being supplied to said distillation column.

59. The improvement according to claim 58 wherein

(a) said warmed distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to compression;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

60. The improvement according to claim 58 wherein

(a) said distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to heating;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

61. The improvement according to claim 55 wherein said first liquid portion is expanded, directed in heat exchange relation with said condensed stream and is then supplied to said column at a mid-column feed position.

62. The improvement according to claim 61 wherein

(a) said warmed distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to compression;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

63. The improvement according to claim 61 wherein

(a) said distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to heating;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

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 and a relatively less volatile fraction containing said C₂ components, C₃ components and heavier hydrocarbon components or 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 the components of said relatively less volatile fraction are recovered;

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 vapor stream and a condensed stream;

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

(3) a distillation stream is withdrawn from an upper region of a fractionation tower and is warmed;

(4) said warmed distillation stream is compressed to higher pressure and thereafter divided into said volatile residue gas fraction and a compressed recycle stream;

(5) said compressed recycle stream is combined with said gaseous first stream and at least a portion of said condensed stream to form a combined stream;

(6) said combined stream is cooled to condense substantially all of it;

(7) said substantially condensed combined stream is expanded to said lower pressure and supplied to said fractionation tower at a top feed position;

(8) said gaseous second stream is expanded to said lower pressure and supplied at a mid-column feed position to a distillation column in a lower region of said fractionation tower;

(9) the quantity and pressure of said combined stream and the quantities and temperatures of said feed streams to the column are effective to maintain tower overhead temperature at a temperature whereby the major portions of the components in said relatively less volatile fraction are recovered.

43. The improvement according to claim 5 wherein at least a portion of said condensed stream is expanded to said lower pressure and combined with at least a portion of said expanded second stream to form a second combined stream, whereupon said second combined stream is supplied to said column at a mid-column feed position.

44. The improvement according to claim 43 wherein

(a) said warmed distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to compression;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

45. The improvement according to claim 43 wherein

(a) said distillation stream is divided into said volatile residue gas fraction and a recycle stream prior to heating;

and

(b) said recycle stream is thereafter compressed to form said compressed recycle stream.

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 and a relatively less volatile fraction containing said C₂ components, C₃ components and heavier hydrocarbon components or 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 the components of said relatively less volatile fraction are recovered;

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

(1) a distillation stream is withdrawn from an upper region of a fractionation tower and is warmed;

(2) said warmed distillation stream is compressed to higher pressure and thereafter divided into said volatile residue gas fraction and a compressed recycle stream;

(3) said compressed recycle stream is combined with said gaseous first stream to form a combined stream;

(4) said combined stream is cooled to condense substantially all of it;

(5) said substantially condensed combined stream is expanded to said lower pressure and supplied to said fractionation tower at a top feed position;

(6) said gaseous second stream is cooled under pressure and then expanded to said lower pressure and supplied at a mid-column feed position to a distillation column in a lower region of said fractionation tower; and

(7) the quantity and pressure of said combined stream and the quantities and temperatures of said feed streams to the column are effective to maintain tower overhead temperature at a temperature whereby the major portions of the components in said relatively less volatile fraction are recovered.

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 and a relatively less volatile fraction containing said C₂ components, C₃ components and heavier hydrocarbon components or 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 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) a distillation stream is withdrawn from an upper region of a fractionation tower and is warmed;

(2) said warmed distillation stream is compressed to higher pressure and thereafter divided into said volatile residue gas fraction and a compressed recycle stream;

(3) said compressed recycle stream is combined with said first stream to form a combined stream;

(4) said combined stream is cooled to condense substantially all of it;

(5) said substantially condensed combined stream is expanded to said lower pressure and supplied to said fractionation tower at a top feed position;

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

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

(8) said vapor stream is expanded to said lower pressure and supplied at a first mid-column feed position to a distillation column in a lower region of said fractionation tower;

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

(10) the quantity and pressure of said combined stream and the quantities and temperatures of said feed streams to the column are effective to maintain tower overhead temperature at a temperature whereby the major portions of the components in said relatively less volatile fraction are recovered.

64. In an apparatus for the separation of a gas containing methane, C₂ components, C₃ components and heavier hydrocarbon components into a volatile residue gas fraction and a relatively less volatile fraction containing said C₂ components, C₃ components and heavier hydrocarbon components or said C₃ components and heavier hydrocarbon components, in said apparatus there being

(a) a first cooling means to cool said gas 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 to expand it to a lower pressure, whereby said stream is further cooled; and

(c) a fractionation tower connected to said first expansion means to receive said further cooled stream therefrom;

the improvement wherein said apparatus includes

(1) first dividing means prior to said first cooling means to divide said feed gas into a first gaseous stream and a second gaseous stream;

(2) heating means connected to said fractionation tower to receive a distillation stream which rises in the fractionation tower and to heat it;

(3) compressing means connected to said heating means to receive said heated distillation stream and to compress it;

(4) second dividing means connected to said compressing means to receive said heated compressed distillation stream and to divide it into said volatile residue gas fraction and a compressed recycle stream;

(5) combining means connected to combine said compressed recycle stream and said first gaseous stream into a combined stream;

(6) second cooling means connected to said combining means to receive said combined stream and to cool it sufficiently to substantially condense it;

(7) second expansion means connected to said second cooling means to receive said substantially condensed combined stream and to expand it to said lower pressure;

said second expansion means being further connected to said fractionation tower to supply said expanded condensed combined stream to the tower at a top feed position;

(8) said first cooling means being connected to said first dividing means to receive said second gaseous stream and to cool it under pressure sufficiently to partially condense it;

(9) separation means connected to said first cooling means to receive said partially condensed second stream and to separate it into a vapor and a condensed stream;

(10) said first expansion means being connected to said separation means to receive said vapor stream and to expand it to said lower pressure;

said first expansion means being further connected to a distillation column in a lower region of said fractionation tower to supply said expanded vapor stream to said distillation column at a first mid-column feed position;

(11) third expansion means being connected to said separation means to receive said condensed stream and to expand it to said lower pressure;

said third expansion means being further connected to said distillation column to supply said expanded condensed stream to said distillation column at a second mid-column feed position; and

(12) control means adapted to regulate the pressure of said combined stream and the quantities and temperatures of said combined stream, said second stream and said condensed stream to maintain column overhead temperature at a temperature whereby the major portions of the components in said relatively less volatile fraction are recovered.

65. In an apparatus for the separation of a gas containing methane, C₂ components, C₃ components and heavier hydrocarbon components into a volatile residue gas fraction and a relatively less volatile fraction containing said C₂ components, C₃ components and heavier hydrocarbon components or said C₃ components and heavier hydrocarbon components, in said apparatus there being

(a) a first cooling means to cool said gas 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 to expand it to a lower pressure, whereby said stream is further cooled; and

(c) a fractionation tower connected to said first expansion means to receive said further cooled stream therefrom;

the improvement wherein said apparatus includes

(1) first cooling means adapted to cool said feed gas under pressure sufficiently to partially condense it;

(2) separation means connected to said first cooling means to receive said partially condensed feed stream and to separate it into a vapor and a condensed stream;

(3) heating means connected to said fractionation tower to receive a distillation stream which rises in the fractionation tower and to heat it;

(4) compressing means connected to said heating means to receive said heated distillation stream and to compress it;

(5) dividing means connected to said compressing means to receive said heated compressed distillation stream and to divide it into said volatile residue gas fraction and a compressed recycle stream;

(6) combining means connected to combine said compressed recycle stream and at least a portion of said condensed stream into a combined stream;

(7) second cooling means connected to said combining means to receive said combined stream and to cool it sufficiently to substantially condense it;

(8) second expansion means connected to said second cooling means to receive said substantially condensed combined stream and to expand it to said lower pressure;

said second expansion means being further connected to said fractionation tower to supply said expanded condensed combined stream to the tower at a top feed position;

(9) said first expansion means being connected to said separation means to receive said vapor stream and to expand it to said lower pressure;

said first expansion means being further connected to a distillation column in a lower region of said fractionation tower to supply said expanded vapor stream to said distillation column at a mid-column feed position; and

(10) control means adapted to regulate the pressure of said combined stream and the quantities and temperatures of said combined stream and said vapor stream to maintain column overhead temperature at a temperature whereby the major portions of the components in said relatively less volatile fraction are recovered.

66. In an apparatus for the separation of a gas containing methane, C₂ components, C₃ components and heavier hydrocarbon components into a volatile residue gas fraction and a relatively less volatile fraction containing said C₂ components, C₃ components and heavier hydrocarbon components or said C₃ components and heavier hydrocarbon components, in said apparatus there being

(a) a first cooling means to cool said gas 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 to expand it to a lower pressure, whereby said stream is further cooled; and

(c) a fractionation tower connected to said first expansion means to receive said further cooled stream therefrom;

the improvement wherein said apparatus includes

(1) first dividing means prior to said first cooling means to divide said feed gas into a first gaseous stream and a second gaseous stream;

(2) heating means connected to said fractionation tower to receive a distillation stream which rises in the fractionation tower and to heat it;

(3) compressing means connected to said heating means to receive said heated distillation stream and to compress it;

(4) second dividing means connected to said compressing means to receive said heated compressed distillation stream and to divide it into said volatile residue gas fraction and a compressed recycle stream;

(5) combining means connected to combine said compressed recycle stream and said first gaseous stream into a combined stream;

(6) second cooling means connected to said combining means to receive said combined stream and to cool it sufficiently to substantially condense it;

(7) second expansion means connected to said second cooling means to receive said substantially condensed combined stream and to expand it to said lower pressure;

said second expansion means being further connected to said fractionation tower to supply said expanded condensed combined stream to the tower at a top feed position;

(8) said first cooling means being connected to said first dividing means to receive said second gaseous stream and to cool it under pressure;

(9) said first expansion means being connected to said first cooling means to receive said cooled second stream and to expand it to said lower pressure;

said first expansion means being further connected to a distillation column in a lower region of said fractionation tower to supply said expanded second stream to said distillation column at a mid-column feed position; and

(10) control means adapted to regulate the pressure of said combined stream and the quantities and temperatures of said combined stream and said second stream to maintain column overhead temperature at a temperature whereby the major portions of the components in said relatively less volatile fraction are recovered.

67. In an apparatus for the separation of a gas containing methane, C₂ components, C₃ components and heavier hydrocarbon components into a volatile residue gas fraction and a relatively less volatile fraction containing said C₂ components, C₃ components and heavier hydrocarbon components or said C₃ components and heavier hydrocarbon components, in said apparatus there being

(a) a first cooling means to cool said gas 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 to expand it to a lower pressure, whereby said stream is further cooled; and

(c) a fractionation tower connected to said first expansion means to receive said further cooled stream therefrom;

the improvement wherein said apparatus includes

(1) first dividing means prior to said first cooling means to divide said feed gas into a first gaseous stream and a second gaseous stream;

(2) heating means connected to said fractionation tower to receive a distillation stream which rises in the fractionation tower and to heat it;

(3) compressing means connected to said heating means to receive said heated distillation stream and to compress it;

(4) second dividing means connected to said compressing means to receive said heated compressed distillation stream and to divide it into said volatile residue gas fraction and a compressed recycle stream;

(5) combining means connected to combine said compressed recycle stream and said first gaseous stream into a combined stream;

(6) second cooling means connected to said combining means to receive said combined stream and to cool it sufficiently to substantially condense it;

(7) second expansion means connected to said second cooling means to receive said substantially condensed combined stream and to expand it to said lower pressure;

said second expansion means being further connected to said fractionation tower to supply said expanded condensed combined stream to the tower at a top feed position;

(8) said first cooling means being connected to said first dividing means to receive said second gaseous stream and to cool it under pressure sufficiently to partially condense it;

(9) separation means connected to said first cooling means to receive said partially condensed second stream and to separate it into a vapor and a condensed stream;

(10) said first expansion means being connected to said separation means to receive said vapor stream and to expand it to said lower pressure;

said first expansion means being further connected to a distillation column in a lower region of said fractionation tower to supply said expanded vapor stream to said distillation column at a first mid-column feed position;

(11) heat exchange means being connected to said separation means to receive said condensed stream and cool it;

(12) third dividing means connected to said heat exchange means to receive said cooled condensed stream and divide it into a first liquid stream and a second liquid stream;

(13) third expansion means being connected to said third dividing means to receive said first liquid stream and to expand it to said lower pressure;

said third expansion means being further connected to said heat exchange means to heat said expanded first liquid stream and thereby supply said cooling to said condensed stream;

said heat exchange means being further connected to said distillation column to supply said heated expanded first liquid stream to said distillation column at a second mid-column feed position;

(14) fourth expansion means being connected to said third dividing means to receive said second liquid stream and to expand it to said lower pressure;

said fourth expansion means being further connected to said distillation column at an upper mid-column feed position; and

(15) control means adapted to regulate the pressure of said combined stream and the quantities and temperatures of said combined stream, said second stream, said first liquid stream and said second liquid stream to maintain column overhead temperature at a temperature whereby the major portions of the components in said relatively less volatile fraction are recovered.