Natural gas liquefaction

• US 7,204,100 B2
• Filed: 05/04/2004
• Issued: 04/17/2007
• Est. Priority Date: 05/04/2004
• Status: Active Grant

• Current Assignee: UOP Llc (Honeywell International Inc.)
• Original Assignee: Ortloff Enigneers, Ltd.
• Inventors: Hudson, Hank M., Lynch, Joe T., Cuellar, Kyle T., Wilkinson, John D.
• Primary Examiner(s): DOERRLER, WILLIAM CHARLES
• Application Number:
  US10/840,072
• Publication Number:
  US 20050247078A1
• Time in Patent Office: 1,078 Days
• Field of Search: 626/12, 626/13, 626/20
• US Class Current: 62/612
• CPC Class Codes: F25J 1/0022 Hydrocarbons, e.g. natural gas
• CPC Class Codes: F25J 1/0035 by gas expansion with extraction of work
• CPC Class Codes: F25J 1/0045 by vaporising a liquid return stream
• CPC Class Codes: F25J 1/0052 by vaporising a liquid refrigerant stream
• CPC Class Codes: F25J 1/0057 after expansion of the liquid refrigerant stream with extraction of work
• CPC Class Codes: F25J 1/0205 as a dual level SCR refrigeration cascade
• CPC Class Codes: F25J 1/0214 as a dual level refrigeration cascade with at least one MCR cycle
• CPC Class Codes: F25J 1/0216 using a C3 pre-cooling cycle
• CPC Class Codes: F25J 1/0239 Purification or treatment step being integrated between two refrigeration cycles of a refrigeration cascade, i.e. first cycle providing feed gas cooling and second cycle providing overhead gas cooling
• CPC Class Codes: F25J 2200/02 in a single pressure main column system
• CPC Class Codes: F25J 2200/04 in a dual pressure main column system
• CPC Class Codes: F25J 2200/30 using a side column in a single pressure 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 2200/74 Refluxing the column with at least a part of the partially condensed overhead gas
• CPC Class Codes: F25J 2200/78 Refluxing the column with a liquid stream originating from an upstream or downstream fractionator column
• CPC Class Codes: F25J 2205/04 in the feed line, i.e. upstream of the fractionation step
• CPC Class Codes: F25J 2230/08 Cold compressor, i.e. suction of the gas at cryogenic temperature and generally without afterstage-cooler
• CPC Class Codes: F25J 2230/20 Integrated compressor and process expander; Gear box arrangement; Multiple compressors on a common shaft
• CPC Class Codes: F25J 2230/60 the fluid being hydrocarbons or 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 2240/30 : Dynamic liquid or hydraulic expansion with extraction of work, e.g. single phase or two-phase turbine
• 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 2270/66 : Closed external refrigeration cycle with multi component refrigerant [MCR], e.g. mixture of hydrocarbons
• CPC Class Codes: F25J 2290/40 : Vertical layout or arrangement of cold equipments within in the cold box, e.g. columns, condensers, heat exchangers etc.
• CPC Class Codes: F25J 3/0209 : Natural gas or substitute natural gas
• 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
• CPC Class Codes: F25J 3/0247 : separation of CnHm with 4 carbon atoms or more

Abstract

A process for liquefying natural gas in conjunction with producing a liquid stream containing predominantly hydrocarbons heavier than methane is disclosed. In the process, the natural gas stream to be liquefied is partially cooled and divided into first and second streams. The first stream is further cooled to condense substantially all of it, expanded to an intermediate pressure, and then supplied to a distillation column at a first mid-column feed position. The second stream is also expanded to intermediate pressure and is then supplied to the column at a second lower mid-column feed position. A distillation stream is withdrawn from the column below the feed point of the second stream and is cooled to condense at least a part of it, forming a reflux stream. At least a portion of the reflux stream is directed to the distillation column as its top feed. The bottom product from this distillation column preferentially contains the majority of any hydrocarbons heavier than methane that would otherwise reduce the purity of the liquefied natural gas. The residual gas stream from the distillation column is compressed to a higher intermediate pressure, cooled under pressure to condense it, and then expanded to low pressure to form the liquefied natural gas stream.

Claims

1. In a process for liquefying a natural gas stream containing methane and heavier hydrocarbon components wherein

(a) said natural gas stream is cooled under pressure to condense at least a portion of it and form a condensed stream;

and

(b) said condensed stream is expanded to lower pressure to form said liquefied natural gas stream;

the improvement wherein

(1) said natural gas stream is treated in one or more cooling steps;

(2) said cooled natural gas stream is divided into at least a first stream and a second stream;

(3) said first stream is cooled to condense substantially all of it and thereafter expanded to an intermediate pressure;

(4) said second stream is expanded to said intermediate pressure;

(5) said expanded first stream and said expanded second stream are directed into a distillation column wherein said streams are separated into a more volatile vapor distillation stream and a relatively less volatile fraction containing a major portion of said heavier hydrocarbon components;

(6) a vapor distillation stream is withdrawn from a region of said distillation column below said expanded second stream and is cooled sufficiently to condense at least a part of it, thereby forming a residual vapor stream and a reflux stream;

(7) said reflux stream is directed into said distillation column as a top feed thereto;

(8) said residual vapor stream is combined with said more volatile vapor distillation stream to form a volatile residue gas fraction containing a major portion of said methane and lighter components; and

(9) said volatile residue gas fraction is cooled under pressure to condense at least a portion of it and form thereby said condensed stream.

6. The improvement according to claim 1, 2, 3, 4, or 5 wherein a liquid distillation stream is withdrawn from said distillation column at a location above the region wherein said vapor distillation stream is withdrawn, whereupon said liquid distillation stream is heated and thereafter redirected into said distillation column as another feed thereto at a location below the region wherein said vapor distillation stream is withdrawn.

7. The improvement according to claim 1, 2, 3, 4, or 5 wherein said reflux stream is divided into at least a first portion and a second portion, whereupon said first portion is directed into said distillation column as a top feed thereto, and said second portion is supplied to said distillation column as another feed thereto, at a feed location in substantially the same region wherein said vapor distillation stream is withdrawn.

8. The improvement according to claim 6 wherein said reflux stream is divided into at least a first portion and a second portion, whereupon said first portion is directed into said distillation column as a top feed thereto, and said second portion is supplied to said distillation column as another feed thereto, at a feed location in substantially the same region wherein said vapor distillation stream is withdrawn.

9. The improvement according to claim 1, 2, 3, 4, or 5 wherein said volatile residue gas fraction is compressed and thereafter cooled under pressure to condense at least a portion of it and form thereby said condensed stream.

10. The improvement according to claim 6 wherein said volatile residue gas fraction is compressed and thereafter cooled under pressure to condense at least a portion of it and form thereby said condensed stream.

11. The improvement according to claim 7 wherein said volatile residue gas fraction is compressed and thereafter cooled under pressure to condense at least a portion of it and form thereby said condensed stream.

12. The improvement according to claim 8 wherein said volatile residue gas fraction is compressed and thereafter cooled under pressure to condense at least a portion of it and form thereby said condensed stream.

13. The improvement according to claim 1, 2, 3, 4, or 5 wherein said volatile residue gas fraction is heated, compressed, and thereafter cooled under pressure to condense at least a portion of it and form thereby said condensed stream.

14. The improvement according to claim 6 wherein said volatile residue gas fraction is heated, compressed, and thereafter cooled under pressure to condense at least a portion of it and form thereby said condensed stream.

15. The improvement according to claim 7 wherein said volatile residue gas fraction is heated, compressed, and thereafter cooled under pressure to condense at least a portion of it and form thereby said condensed stream.

16. The improvement according to claim 8 wherein said volatile residue gas fraction is heated, compressed, and thereafter cooled under pressure to condense at least a portion of it and form thereby said condensed stream.

17. The improvement according to claim 1, 2, 3, 4, or 5 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and heavier hydrocarbon components selected from the group consisting of C₂ components and C₂ components+C₃ components.

18. The improvement according to claim 6 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and heavier hydrocarbon components selected from the group consisting of C₂ components and C₂ components+C₃ components.

19. The improvement according to claim 7 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and heavier hydrocarbon components selected from the group consisting of C₂ components and C₂ components+C₃ components.

20. The improvement according to claim 8 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and heavier hydrocarbon components selected from the group consisting of C₂ components and C₂ components+C₃ components.

21. The improvement according to claim 9 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and heavier hydrocarbon components selected from the group consisting of C₂ components and C₂ components+C₃ components.

22. The improvement according to claim 10 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and heavier hydrocarbon components selected from the group consisting of C₂ components and C₂ components+C₃ components.

23. The improvement according to claim 11 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and heavier hydrocarbon components selected from the group consisting of C₂ components and C₂ components+C₃ components.

24. The improvement according to claim 12 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and heavier hydrocarbon components selected from the group consisting of C₂ components and C₂ components+C₃ components.

25. The improvement according to claim 13 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and heavier hydrocarbon components selected from the group consisting of C₂ components and C₂ components+C₃ components.

26. The improvement according to claim 14 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and heavier hydrocarbon components selected from the group consisting of C₂ components and C₂ components+C₃ components.

27. The improvement according to claim 15 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and heavier hydrocarbon components selected from the group consisting of C₂ components and C₂ components+C₃ components.

28. The improvement according to claim 16 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and heavier hydrocarbon components selected from the group consisting of C₂ components and C₂ components+C₃ components.

2. In a process for liquefying a natural gas stream containing methane and heavier hydrocarbon components wherein

(a) said natural gas stream is cooled under pressure to condense at least a portion of it and form a condensed stream;

and

(b) said condensed stream is expanded to lower pressure to form said liquefied natural gas stream;

the improvement wherein

(1) said natural gas stream is treated in one or more cooling steps to partially condense it;

(2) said partially condensed natural gas stream is separated to provide thereby a vapor stream and a liquid stream;

(3) said vapor stream is divided into at least a first stream and a second stream;

(4) said first stream is cooled to condense substantially all of it and thereafter expanded to an intermediate pressure;

(5) said second stream is expanded to said intermediate pressure;

(6) said liquid stream is expanded to said intermediate pressure;

(7) said expanded first stream, said expanded second stream, and said expanded liquid stream are directed into a distillation column wherein said streams are separated into a more volatile vapor distillation stream and a relatively less volatile fraction containing a major portion of said heavier hydrocarbon components;

(8) a vapor distillation stream is withdrawn from a region of said distillation column below said expanded second stream and is cooled sufficiently to condense at least a part of it, thereby forming a residual vapor stream and a reflux stream;

(9) said reflux stream is directed into said distillation column as a top feed thereto;

(10) said residual vapor stream is combined with said more volatile vapor distillation stream to form a volatile residue gas fraction containing a major portion of said methane and lighter components; and

(11) said volatile residue gas fraction is cooled under pressure to condense at least a portion of it and form thereby said condensed stream.

3. In a process for liquefying a natural gas stream containing methane and heavier hydrocarbon components wherein

(a) said natural gas stream is cooled under pressure to condense at least a portion of it and form a condensed stream;

and

(b) said condensed stream is expanded to lower pressure to form said liquefied natural gas stream;

the improvement wherein

(1) said natural gas stream is treated in one or more cooling steps to partially condense it;

(2) said partially condensed natural gas stream is separated to provide thereby a vapor stream and a liquid stream;

(3) said vapor stream is divided into at least a first stream and a second stream;

(4) said first stream is cooled to condense substantially all of it and thereafter expanded to an intermediate pressure;

(5) said second stream is expanded to said intermediate pressure;

(6) said liquid stream is expanded to said intermediate pressure and heated;

(7) said expanded first stream, said expanded second stream, and said heated expanded liquid stream are directed into a distillation column wherein said streams are separated into a more volatile vapor distillation stream and a relatively less volatile fraction containing a major portion of said heavier hydrocarbon components;

(8) a vapor distillation stream is withdrawn from a region of said distillation column below said expanded second stream and is cooled sufficiently to condense at least a part of it, thereby forming a residual vapor stream and a reflux stream;

(9) said reflux stream is directed into said distillation column as a top feed thereto;

(10) said residual vapor stream is combined with said more volatile vapor distillation stream to form a volatile residue gas fraction containing a major portion of said methane and lighter components; and

(11) said volatile residue gas fraction is cooled under pressure to condense at least a portion of it and form thereby said condensed stream.

4. In a process for liquefying a natural gas stream containing methane and heavier hydrocarbon components wherein

(a) said natural gas stream is cooled under pressure to condense at least a portion of it and form a condensed stream;

and

(b) said condensed stream is expanded to lower pressure to form said liquefied natural gas stream;

the improvement wherein

(1) said natural gas stream is treated in one or more cooling steps to partially condense it;

(2) said partially condensed natural gas stream is separated to provide thereby a vapor stream and a liquid stream;

(3) said vapor stream is divided into at least a first stream and a second stream;

(4) said first stream is combined with at least a portion of said liquid stream, forming thereby a combined stream;

(5) said combined stream is cooled to condense substantially all of it and thereafter expanded to an intermediate pressure;

(6) said second stream is expanded to said intermediate pressure;

(7) any remaining portion of said liquid stream is expanded to said intermediate pressure;

(8) said expanded combined stream, said expanded second stream, and said expanded remaining portion of said liquid stream are directed into a distillation column wherein said streams are separated into a more volatile vapor distillation stream and a relatively less volatile fraction containing a major portion of said heavier hydrocarbon components;

(9) a vapor distillation stream is withdrawn from a region of said distillation column below said expanded second stream and is cooled sufficiently to condense at least a part of it, thereby forming a residual vapor stream and a reflux stream;

(10) said reflux stream is directed into said distillation column as a top feed thereto;

(11) said residual vapor stream is combined with said more volatile vapor distillation stream to form a volatile residue gas fraction containing a major portion of said methane and lighter components; and

(12) said volatile residue gas fraction is cooled under pressure to condense at least a portion of it and form thereby said condensed stream.

5. In a process for liquefying a natural gas stream containing methane and heavier hydrocarbon components wherein

(a) said natural gas stream is cooled under pressure to condense at least a portion of it and form a condensed stream;

and

(b) said condensed stream is expanded to lower pressure to form said liquefied natural gas stream;

the improvement wherein

(1) said natural gas stream is treated in one or more cooling steps to partially condense it;

(2) said partially condensed natural gas stream is separated to provide thereby a vapor stream and a liquid stream;

(3) said vapor stream is divided into at least a first stream and a second stream;

(4) said first stream is combined with at least a portion of said liquid stream, forming thereby a combined stream;

(5) said combined stream is cooled to condense substantially all of it and thereafter expanded to an intermediate pressure;

(6) said second stream is expanded to said intermediate pressure;

(7) any remaining portion of said liquid stream is expanded to said intermediate pressure and heated;

(8) said expanded combined stream, said expanded second stream, and said heated expanded remaining portion of said liquid stream are directed into a distillation column wherein said streams are separated into a more volatile vapor distillation stream and a relatively less volatile fraction containing a major portion of said heavier hydrocarbon components;

(9) a vapor distillation stream is withdrawn from a region of said distillation column below said expanded second stream and is cooled sufficiently to condense at least a part of it, thereby forming a residual vapor stream and a reflux stream;

(10) said reflux stream is directed into said distillation column as a top feed thereto;

(11) said residual vapor stream is combined with said more volatile vapor distillation stream to form a volatile residue gas fraction containing a major portion of said methane and lighter components; and

(12) said volatile residue gas fraction is cooled under pressure to condense at least a portion of it and form thereby said condensed stream.

29. An apparatus for the liquefaction of a natural gas stream containing methane and heavier hydrocarbon components, which includes

(1) one or more first heat exchange means to receive said natural gas stream and cool it under pressure;

(2) dividing means connected to said first heat exchange means to receive said cooled natural gas stream and divide it into at least a first stream and a second stream;

(3) second heat exchange means connected to said dividing means to receive said first stream and to cool it sufficiently to substantially condense it;

(4) first expansion means connected to said second heat exchange means to receive said substantially condensed first stream and expand it to an intermediate pressure;

(5) second expansion means connected to said dividing means to receive said second stream and expand it to said intermediate pressure;

(6) a distillation column connected to said first expansion means and said second expansion means to receive said expanded first stream and said expanded second stream, with said distillation column adapted to separate said streams into a more volatile vapor distillation stream and a relatively less volatile fraction containing a major portion of said heavier hydrocarbon components;

(7) vapor withdrawing means connected to said distillation column to receive a vapor distillation stream from a region of said distillation column below said expanded second stream;

(8) third heat exchange means connected to said vapor withdrawing means to receive said vapor distillation stream and cool it sufficiently to condense at least a part of it;

(9) separation means connected to said third heat exchange means to receive said cooled partially condensed distillation stream and separate it into a residual vapor stream and a reflux stream, said separation means being further connected to said distillation column to direct said reflux stream into said distillation column as a top feed thereto;

(10) combining means connected to said distillation column and said separation means to receive said more volatile vapor distillation stream and said residual vapor stream and form a volatile residue gas fraction containing a major portion of said methane and lighter components;

(11) fourth heat exchange means connected to said combining means to receive said volatile residue gas fraction, with said fourth heat exchange means adapted to cool said volatile residue gas fraction under pressure to condense at least a portion of it and form thereby a condensed stream;

(12) third expansion means connected to said fourth heat exchange means to receive said condensed stream and expand it to lower pressure to form said liquefied natural gas stream; and

(13) 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 heavier hydrocarbon components is recovered in said relatively less volatile fraction.

34. The apparatus according to claim 29 wherein said apparatus includes

(1) liquid withdrawing means connected to said distillation column to receive a liquid distillation stream at a location above the region wherein said vapor distillation stream is withdrawn;

and

(2) heating means connected to said liquid withdrawing means to receive said liquid distillation stream and heat it, said heating means being further connected to said distillation column to direct said heated liquid distillation stream into said distillation column as another feed thereto at a location below the region wherein said vapor distillation stream is withdrawn.

39. The improvement according to claim 29 wherein said apparatus includes

(1) second dividing means connected to said separating means to divide said reflux stream into at least a first portion and a second portion;

(2) said second dividing means being further connected to said distillation column to direct said first portion into said distillation column as a top feed thereto; and

(3) said second dividing means being further connected to said distillation column to supply said second portion to said distillation column at a feed position in substantially the same region wherein said vapor distillation stream is withdrawn.

44. The improvement according to claim 34 wherein said apparatus includes

(1) second dividing means connected to said separating means to divide said reflux stream into at least a first portion and a second portion;

(2) said second dividing means being further connected to said distillation column to direct said first portion into said distillation column as a top feed thereto; and

(3) said second dividing means being further connected to said distillation column to supply said second portion to said distillation column at a feed position in substantially the same region wherein said vapor distillation stream is withdrawn.

49. The apparatus according to claim 29, 30, 31, 34, 35, 36, 39, 40, 41, 44, 45, or 46 wherein said apparatus includes

(1) compressing means connected to said combining means to receive said volatile residue gas fraction and compress it;

and

(2) said fourth heat exchange means connected to said compressing means to receive said compressed volatile residue gas fraction, with said fourth heat exchange means adapted to cool said compressed volatile residue gas fraction under pressure to condense at least a portion of it and form thereby said condensed stream.

51. The apparatus according to claim 29, 30, 39, or 40 wherein said apparatus includes

(1) heating means connected to said combining means to receive said volatile residue gas fraction and heat it;

(2) compressing means connected to said heating means to receive said heated volatile residue gas fraction and compress it; and

(3) said fourth heat exchange means connected to said compressing means to receive said compressed heated volatile residue gas fraction, with said fourth heat exchange means adapted to cool said compressed heated volatile residue gas fraction under pressure to condense at least a portion of it and form thereby said condensed stream.

57. The apparatus according to claim 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, or 48 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and heavier hydrocarbon components selected from the group consisting of C₂ components and C₂ components+C₃ components.

58. The apparatus according to claim 49 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and heavier hydrocarbon components selected from the group consisting of C₂ components and C₂ components+C₃ components.

60. The apparatus according to claim 51 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and heavier hydrocarbon components selected from the group consisting of C₂ components and C₂ components+C₃ components.

30. An apparatus for the liquefaction of a natural gas stream containing methane and heavier hydrocarbon components, which includes

(1) one or more first heat exchange means to receive said natural gas stream and cool it under pressure sufficiently to partially condense it;

(2) first separation means connected to said first heat exchange means to receive said partially condensed natural gas stream and separate it into a vapor stream and a liquid stream;

(3) dividing means connected to said first separation means to receive said vapor stream and divide it into at least a first stream and a second stream;

(4) second heat exchange means connected to said dividing means to receive said first stream and to cool it sufficiently to substantially condense it;

(5) first expansion means connected to said second heat exchange means to receive said substantially condensed first stream and expand it to an intermediate pressure;

(6) second expansion means connected to said dividing means to receive said second stream and expand it to said intermediate pressure;

(7) third expansion means connected to said first separation means to receive said liquid stream and expand it to said intermediate pressure;

(8) a distillation column connected to said first expansion means, said second expansion means, and said third expansion means to receive said expanded first stream, said expanded second stream, and said expanded liquid stream, with said distillation column adapted to separate said streams into a more volatile vapor distillation stream and a relatively less volatile fraction containing a major portion of said heavier hydrocarbon components;

(9) vapor withdrawing means connected to said distillation column to receive a vapor distillation stream from a region of said distillation column below said expanded second stream;

(10) third heat exchange means connected to said vapor withdrawing means to receive said vapor distillation stream and cool it sufficiently to condense at least a part of it;

(11) second separation means connected to said third heat exchange means to receive said cooled partially condensed distillation stream and separate it into a residual vapor stream and a reflux stream, said second separation means being further connected to said distillation column to direct said reflux stream into said distillation column as a top feed thereto;

(12) combining means connected to said distillation column and said second separation means to receive said more volatile vapor distillation stream and said residual vapor stream and form a volatile residue gas fraction containing a major portion of said methane and lighter components;

(13) fourth heat exchange means connected to said combining means to receive said volatile residue gas fraction, with said fourth heat exchange means adapted to cool said volatile residue gas fraction under pressure to condense at least a portion of it and form thereby a condensed stream;

(14) fourth expansion means connected to said fourth heat exchange means to receive said condensed stream and expand it to lower pressure to form said liquefied natural gas stream; and

(15) 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 heavier hydrocarbon components is recovered in said relatively less volatile fraction.

35. The apparatus according to claim 30 wherein said apparatus includes

(1) liquid withdrawing means connected to said distillation column to receive a liquid distillation stream at a location above the region wherein said vapor distillation stream is withdrawn;

and

(2) heating means connected to said liquid withdrawing means to receive said liquid distillation stream and heat it, said heating means being further connected to said distillation column to direct said heated liquid distillation stream into said distillation column as another feed thereto at a location below the region wherein said vapor distillation stream is withdrawn.

40. The improvement according to claim 30 wherein said apparatus includes

(1) second dividing means connected to said second separating means to divide said reflux stream into at least a first portion and a second portion;

(2) said second dividing means being further connected to said distillation column to direct said first portion into said distillation column as a top feed thereto; and

(3) said second dividing means being further connected to said distillation column to supply said second portion to said distillation column at a feed position in substantially the same region wherein said vapor distillation stream is withdrawn.

45. The improvement according to claim 35 wherein said apparatus includes

(1) second dividing means connected to said second separating means to divide said reflux stream into at least a first portion and a second portion;

(2) said second dividing means being further connected to said distillation column to direct said first portion into said distillation column as a top feed thereto; and

(3) said second dividing means being further connected to said distillation column to supply said second portion to said distillation column at a feed position in substantially the same region wherein said vapor distillation stream is withdrawn.

31. An apparatus for the liquefaction of a natural gas stream containing methane and heavier hydrocarbon components, which includes

(1) one or more first heat exchange means to receive said natural gas stream and cool it under pressure sufficiently to partially condense it;

(2) first separation means connected to said first heat exchange means to receive said partially condensed natural gas stream and separate it into a vapor stream and a liquid stream;

(3) dividing means connected to said first separation means to receive said vapor stream and divide it into at least a first stream and a second stream;

(4) second heat exchange means connected to said dividing means to receive said first stream and to cool it sufficiently to substantially condense it;

(5) first expansion means connected to said second heat exchange means to receive said substantially condensed first stream and expand it to an intermediate pressure;

(6) second expansion means connected to said dividing means to receive said second stream and expand it to said intermediate pressure;

(7) third expansion means connected to said first separation means to receive said liquid stream and expand it to said intermediate pressure;

(8) heating means connected to said third expansion means to receive said expanded liquid stream and heat it;

(9) a distillation column connected to said first expansion means, said second expansion means, and said heating means to receive said expanded first stream, said expanded second stream, and said heated expanded liquid stream, with said distillation column adapted to separate said streams into a more volatile vapor distillation stream and a relatively less volatile fraction containing a major portion of said heavier hydrocarbon components;

(10) vapor withdrawing means connected to said distillation column to receive a vapor distillation stream from a region of said distillation column below said expanded second stream;

(11) third heat exchange means connected to said vapor withdrawing means to receive said vapor distillation stream and cool it sufficiently to condense at least a part of it;

(12) second separation means connected to said third heat exchange means to receive said cooled partially condensed distillation stream and separate it into a residual vapor stream and a reflux stream, said second separation means being further connected to said distillation column to direct said reflux stream into said distillation column as a top feed thereto;

(13) combining means connected to said distillation column and said second separation means to receive said more volatile vapor distillation stream and said residual vapor stream and form a volatile residue gas fraction containing a major portion of said methane and lighter components;

(14) fourth heat exchange means connected to said combining means to receive said volatile residue gas fraction, with said fourth heat exchange means adapted to cool said volatile residue gas fraction under pressure to condense at least a portion of it and form thereby a condensed stream;

(15) fourth expansion means connected to said fourth heat exchange means to receive said condensed stream and expand it to lower pressure to form said liquefied natural gas stream; and

(16) 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 heavier hydrocarbon components is recovered in said relatively less volatile fraction.

36. The apparatus according to claim 31 wherein said apparatus includes

(1) liquid withdrawing means connected to said distillation column to receive a liquid distillation stream at a location above the region wherein said vapor distillation stream is withdrawn;

and

(2) second heating means connected to said liquid withdrawing means to receive said liquid distillation stream and heat it, said second heating means being further connected to said distillation column to direct said heated liquid distillation stream into said distillation column as another feed thereto at a location below the region wherein said vapor distillation stream is withdrawn.

41. The improvement according to claim 31 wherein said apparatus includes

(1) second dividing means connected to said second separating means to divide said reflux stream into at least a first portion and a second portion;

(2) said second dividing means being further connected to said distillation column to direct said first portion into said distillation column as a top feed thereto; and

(3) said second dividing means being further connected to said distillation column to supply said second portion to said distillation column at a feed position in substantially the same region wherein said vapor distillation stream is withdrawn.

46. The improvement according to claim 36 wherein said apparatus includes

(1) second dividing means connected to said second separating means to divide said reflux stream into at least a first portion and a second portion;

(2) said second dividing means being further connected to said distillation column to direct said first portion into said distillation column as a top feed thereto; and

(3) said second dividing means being further connected to said distillation column to supply said second portion to said distillation column at a feed position in substantially the same region wherein said vapor distillation stream is withdrawn.

52. The apparatus according to claim 31, 34, 35, 41, 44, or 45 wherein said apparatus includes

(1) second heating means connected to said combining means to receive said volatile residue gas fraction and heat it;

(2) compressing means connected to said second heating means to receive said heated volatile residue gas fraction and compress it; and

(3) said fourth heat exchange means connected to said compressing means to receive said compressed heated volatile residue gas fraction, with said fourth heat exchange means adapted to cool said compressed heated volatile residue gas fraction under pressure to condense at least a portion of it and form thereby said condensed stream.

53. The apparatus according to claim 36 or 46 wherein said apparatus includes

(1) third heating means connected to said combining means to receive said volatile residue gas fraction and heat it;

(2) compressing means connected to said third heating means to receive said heated volatile residue gas fraction and compress it; and

(3) said fourth heat exchange means connected to said compressing means to receive said compressed heated volatile residue gas fraction, with said fourth heat exchange means adapted to cool said compressed heated volatile residue gas fraction under pressure to condense at least a portion of it and form thereby said condensed stream.

61. The apparatus according to claim 52 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and heavier hydrocarbon components selected from the group consisting of C₂ components and C₂ components+C₃ components.

62. The apparatus according to claim 53 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and heavier hydrocarbon components selected from the group consisting of C₂ components and C₂ components+C₃ components.

32. An apparatus for the liquefaction of a natural gas stream containing methane and heavier hydrocarbon components, which includes

(1) one or more first heat exchange means to receive said natural gas stream and cool it under pressure sufficiently to partially condense it;

(2) first separation means connected to said first heat exchange means to receive said partially condensed natural gas stream and separate it into a vapor stream and a liquid stream;

(3) dividing means connected to said first separation means to receive said vapor stream and divide it into at least a first stream and a second stream;

(4) first combining means connected to said dividing means and to said first separation means to receive said first stream and at least a portion of said liquid stream and form thereby a combined stream;

(5) second heat exchange means connected to said first combining means to receive said combined stream and to cool it sufficiently to substantially condense it;

(6) first expansion means connected to said second heat exchange means to receive said substantially condensed combined stream and expand it to an intermediate pressure;

(7) second expansion means connected to said dividing means to receive said second stream and expand it to said intermediate pressure;

(8) third expansion means connected to said first separation means to receive any remaining portion of said liquid stream and expand it to said intermediate pressure;

(9) a distillation column connected to said first expansion means, said second expansion means, and said third expansion means to receive said expanded combined stream, said expanded second stream, and said expanded remaining portion of said liquid stream, with said distillation column adapted to separate said streams into said more volatile vapor distillation stream and a relatively less volatile fraction containing a major portion of said heavier hydrocarbon components;

(10) vapor withdrawing means connected to said distillation column to receive a vapor distillation stream from a region of said distillation column below said expanded second stream;

(11) third heat exchange means connected to said vapor withdrawing means to receive said vapor distillation stream and cool it sufficiently to condense at least a part of it;

(12) second separation means connected to said third heat exchange means to receive said cooled partially condensed distillation stream and separate it into a residual vapor stream and a reflux stream, said second separation means being further connected to said distillation column to direct said reflux stream into said distillation column as a top feed thereto;

(13) second combining means connected to said distillation column and said second separation means to receive said more volatile vapor distillation stream and said residual vapor stream and form a volatile residue gas fraction containing a major portion of said methane and lighter components;

(14) fourth heat exchange means connected to said second combining means to receive said volatile residue gas fraction, with said fourth heat exchange means adapted to cool said volatile residue gas fraction under pressure to condense at least a portion of it and form thereby a condensed stream;

(15) fourth expansion means connected to said fourth heat exchange means to receive said condensed stream and expand it to lower pressure to form said liquefied natural gas stream; and

(16) 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 heavier hydrocarbon components is recovered in said relatively less volatile fraction.

37. The apparatus according to claim 32 wherein said apparatus includes

(1) liquid withdrawing means connected to said distillation column to receive a liquid distillation stream at a location above the region wherein said vapor distillation stream is withdrawn;

and

(2) heating means connected to said liquid withdrawing means to receive said liquid distillation stream and heat it, said heating means being further connected to said distillation column to direct said heated liquid distillation stream into said distillation column as another feed thereto at a location below the region wherein said vapor distillation stream is withdrawn.

42. The improvement according to claim 32 wherein said apparatus includes

(1) second dividing means connected to said second separating means to divide said reflux stream into at least a first portion and a second portion;

(2) said second dividing means being further connected to said distillation column to direct said first portion into said distillation column as a top feed thereto; and

(3) said second dividing means being further connected to said distillation column to supply said second portion to said distillation column at a feed position in substantially the same region wherein said vapor distillation stream is withdrawn.

47. The improvement according to claim 37 wherein said apparatus includes

(1) second dividing means connected to said second separating means to divide said reflux stream into at least a first portion and a second portion;

(2) said second dividing means being further connected to said distillation column to direct said first portion into said distillation column as a top feed thereto; and

(3) said second dividing means being further connected to said distillation column to supply said second portion to said distillation column at a feed position in substantially the same region wherein said vapor distillation stream is withdrawn.

50. The apparatus according to claim 32, 33, 37, 38, 42, 43, 47, or 48 wherein said apparatus includes

(1) compressing means connected to said second combining means to receive said volatile residue gas fraction and compress it;

and

(2) said fourth heat exchange means connected to said compressing means to receive said compressed volatile residue gas fraction, with said fourth heat exchange means adapted to cool said compressed volatile residue gas fraction under pressure to condense at least a portion of it and form thereby said condensed stream.

54. The apparatus according to claim 32 or 42 wherein said apparatus includes

(1) heating means connected to said second combining means to receive said volatile residue gas fraction and heat it;

(2) compressing means connected to said heating means to receive said heated volatile residue gas fraction and compress it; and

(3) said fourth heat exchange means connected to said compressing means to receive said compressed heated volatile residue gas fraction, with said fourth heat exchange means adapted to cool said compressed heated volatile residue gas fraction under pressure to condense at least a portion of it and form thereby said condensed stream.

59. The apparatus according to claim 50 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and heavier hydrocarbon components selected from the group consisting of C₂ components and C₂ components+C₃ components.

63. The apparatus according to claim 54 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and heavier hydrocarbon components selected from the group consisting of C₂ components and C₂ components+C₃ components.

33. An apparatus for the liquefaction of a natural gas stream containing methane and heavier hydrocarbon components, which includes

(1) one or more first heat exchange means to receive said natural gas stream and cool it under pressure sufficiently to partially condense it;

(2) first separation means connected to said first heat exchange means to receive said partially condensed natural gas stream and separate it into a vapor stream and a liquid stream;

(3) dividing means connected to said first separation means to receive said vapor stream and divide it into at least a first stream and a second stream;

(4) first combining means connected to said dividing means and to said first separation means to receive said first stream and at least a portion of said liquid stream and form thereby a combined stream;

(5) second heat exchange means connected to said first combining means to receive said combined stream and to cool it sufficiently to substantially condense it;

(6) first expansion means connected to said second heat exchange means to receive said substantially condensed combined stream and expand it to an intermediate pressure;

(7) second expansion means connected to said dividing means to receive said second stream and expand it to said intermediate pressure;

(8) third expansion means connected to said first separation means to receive any remaining portion of said liquid stream and expand it to said intermediate pressure;

(9) heating means connected to said third expansion means to receive said expanded liquid stream and heat it;

(10) a distillation column connected to said first expansion means, said second expansion means, and said heating means to receive said expanded combined stream, said expanded second stream, and said heated expanded remaining portion of said liquid stream, with said distillation column adapted to separate said streams into said more volatile vapor distillation stream and a relatively less volatile fraction containing a major portion of said heavier hydrocarbon components;

(11) vapor withdrawing means connected to said distillation column to receive a vapor distillation stream from a region of said distillation column below said expanded second stream;

(12) third heat exchange means connected to said vapor withdrawing means to receive said vapor distillation stream and cool it sufficiently to condense at least a part of it;

(13) second separation means connected to said third heat exchange means to receive said cooled partially condensed distillation stream and separate it into a residual vapor stream and a reflux stream, said second separation means being further connected to said distillation column to direct said reflux stream into said distillation column as a top feed thereto;

(14) second combining means connected to said distillation column and said second separation means to receive said more volatile vapor distillation stream and said residual vapor stream and form a volatile residue gas fraction containing a major portion of said methane and lighter components;

(15) fourth heat exchange means connected to said second combining means to receive said volatile residue gas fraction, with said fourth heat exchange means adapted to cool said volatile residue gas fraction under pressure to condense at least a portion of it and form thereby a condensed stream;

(16) fourth expansion means connected to said fourth heat exchange means to receive said condensed stream and expand it to lower pressure to form said liquefied natural gas stream; 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 heavier hydrocarbon components is recovered in said relatively less volatile fraction.

38. The apparatus according to claim 33 wherein said apparatus includes

(1) liquid withdrawing means connected to said distillation column to receive a liquid distillation stream at a location above the region wherein said vapor distillation stream is withdrawn;

and

(2) second heating means connected to said liquid withdrawing means to receive said liquid distillation stream and heat it, said second heating means being further connected to said distillation column to direct said heated liquid distillation stream into said distillation column as another feed thereto at a location below the region wherein said vapor distillation stream is withdrawn.

43. The improvement according to claim 33 wherein said apparatus includes

(1) second dividing means connected to said second separating means to divide said reflux stream into at least a first portion and a second portion;

(2) said second dividing means being further connected to said distillation column to direct said first portion into said distillation column as a top feed thereto; and

(3) said second dividing means being further connected to said distillation column to supply said second portion to said distillation column at a feed position in substantially the same region wherein said vapor distillation stream is withdrawn.

48. The improvement according to claim 38 wherein said apparatus includes

(1) second dividing means connected to said second separating means to divide said reflux stream into at least a first portion and a second portion;

(2) said second dividing means being further connected to said distillation column to direct said first portion into said distillation column as a top feed thereto; and

(3) said second dividing means being further connected to said distillation column to supply said second portion to said distillation column at a feed position in substantially the same region wherein said vapor distillation stream is withdrawn.

55. The apparatus according to claim 33, 37, 43, or 47 wherein said apparatus includes

(1) second heating means connected to said second combining means to receive said volatile residue gas fraction and heat it;

(2) compressing means connected to said second heating means to receive said heated volatile residue gas fraction and compress it; and

(3) said fourth heat exchange means connected to said compressing means to receive said compressed heated volatile residue gas fraction, with said fourth heat exchange means adapted to cool said compressed heated volatile residue gas fraction under pressure to condense at least a portion of it and form thereby said condensed stream.

56. The apparatus according to claim 38 or 48 wherein said apparatus includes

(1) third heating means connected to said second combining means to receive said volatile residue gas fraction and heat it;

(2) compressing means connected to said third heating means to receive said heated volatile residue gas fraction and compress it; and

(3) said fourth heat exchange means connected to said compressing means to receive said compressed heated volatile residue gas fraction, with said fourth heat exchange means adapted to cool said compressed heated volatile residue gas fraction under pressure to condense at least a portion of it and form thereby said condensed stream.

64. The apparatus according to claim 55 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and heavier hydrocarbon components selected from the group consisting of C₂ components and C₂ components+C₃ components.

65. The apparatus according to claim 56 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and heavier hydrocarbon components selected from the group consisting of C₂ components and C₂ components+C₃ components.