Natural gas liquefaction

• US 6,945,075 B2
• Filed: 10/23/2002
• Issued: 09/20/2005
• Est. Priority Date: 10/23/2002
• Status: Expired due to Term

• Current Assignee: UOP Llc (Honeywell International Inc.)
• Original Assignee: Elkcorp (Standard Industries Holdings, Inc.)
• Inventors: Ceullar, Kyle T., Hudson, Hank M., Wilkinson, John D.
• Primary Examiner(s): DOERRLER, WILLIAM CHARLES
• Application Number:
  US10/278,610
• Publication Number:
  US 20040079107A1
• Time in Patent Office: 1,063 Days
• Field of Search: 626/20, 626/21, 626/27, 626/13, 626/11
• US Class Current: 62/620
• 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 1/0042 by liquid 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 1/0216 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 2200/74 Refluxing the column with at least a part of the partially condensed overhead gas
• CPC Class Codes: F25J 2200/80 using integrated mass and heat exchange, i.e. non-adiabatic rectification in a reflux exchanger or dephlegmator
• CPC Class Codes: F25J 2205/04 in the feed line, i.e. upstream of the fractionation step
• 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 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

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, expanded to an intermediate pressure, and supplied to a distillation column. 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 gaseous stream and a second gaseous stream;

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

(4) said expanded substantially condensed first gaseous stream is directed in heat exchange relation with a more volatile vapor distillation stream which rises from fractionation stages of a distillation column and is thereby warmed;

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

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

(7) said more volatile vapor distillation stream is cooled by said expanded substantially condensed first gaseous stream sufficiently to partially condense it and is thereafter separated to form a volatile residue gas fraction containing a major portion of said methane and lighter components and a reflux stream;

(8) said reflux stream is directed into said distillation column as a top feed thereto; 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 wherein said distillation column is a lower section of a fractionation tower and wherein said more volatile vapor distillation stream is cooled sufficiently to partially condense it in a portion of said tower above said distillation column and concurrently separated to form said volatile residue gas fraction and said reflux stream, whereupon said reflux stream flows to the top fractionation stage of said distillation column.

11. The improvement according to claim 1 wherein said more volatile vapor distillation stream is cooled sufficiently to partially condense it in a dephlegmator and concurrently separated to form said volatile residue gas fraction and said reflux stream, whereupon said reflux stream flows from the dephlegmator to the top fractionation stage of said distillation column.

16. The improvement according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 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.

17. The improvement according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 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.

18. The improvement according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and C₂ components.

19. The improvement according to claim 16 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and C₂ components.

20. The improvement according to claim 17 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and C₂ components.

21. The improvement according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, C₂ components, and C₃ components.

22. The improvement according to claim 16 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, C₂ components, and C₃ components.

23. The improvement according to claim 17 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, C₂ components, and 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 gaseous stream and a second gaseous stream;

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

(5) said expanded substantially condensed first gaseous stream is directed in heat exchange relation with a more volatile vapor distillation stream which rises from fractionation stages of a distillation column and is thereby warmed;

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

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

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

(9) said more volatile vapor distillation stream is cooled by said expanded substantially condensed first gaseous stream sufficiently to partially condense it and is thereafter separated to form a volatile residue gas fraction containing a major portion of said methane and lighter components and a reflux stream;

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

7. The improvement according to claim 2 wherein said distillation column is a lower section of a fractionation tower and wherein said more volatile vapor distillation stream is cooled sufficiently to partially condense it in a portion of said tower above said distillation column and concurrently separated to form said volatile residue gas fraction and said reflux stream, whereupon said reflux stream flows to the top fractionation stage of said distillation column.

12. The improvement according to claim 2 wherein said more volatile vapor distillation stream is cooled sufficiently to partially condense it in a dephlegmator and concurrently separated to form said volatile residue gas fraction and said reflux stream, whereupon said reflux stream flows from the dephlegmator to the top fractionation stage of said distillation column.

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 gaseous stream and a second gaseous stream;

(4) said first gaseous 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 expanded substantially condensed combined stream is directed in heat exchange relation with a more volatile vapor distillation stream which rises from fractionation stages of a distillation column and is thereby warmed;

(7) said second gaseous stream is expanded to said intermediate pressure;

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

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

(10) said more volatile vapor distillation stream is cooled by said expanded substantially condensed combined stream sufficiently to partially condense it and is thereafter separated to form a volatile residue gas fraction containing a major portion of said methane and lighter components and a reflux stream;

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

8. The improvement according to claim 3 wherein said distillation column is a lower section of a fractionation tower and wherein said more volatile vapor distillation stream is cooled sufficiently to partially condense it in a portion of said tower above said distillation column and concurrently separated to form said volatile residue gas fraction and said reflux stream, whereupon said reflux stream flows to the top fractionation stage of said distillation column.

13. The improvement according to claim 3 wherein said more volatile vapor distillation stream is cooled sufficiently to partially condense it in a dephlegmator and concurrently separated to form said volatile residue gas fraction and said reflux stream, whereupon said reflux stream flows from the dephlegmator to the top fractionation stage of said distillation column.

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 gaseous stream and a second gaseous stream;

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

(5) said expanded substantially condensed first gaseous stream is directed in heat exchange relation with a more volatile vapor distillation stream which rises from fractionation stages of a distillation column and is thereby warmed;

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

(7) said liquid stream is cooled and thereafter divided into at least a first portion and a second portion;

(8) said first portion is expanded to said intermediate pressure and thereafter warmed;

(9) said second portion is expanded to said intermediate pressure;

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

(11) said more volatile vapor distillation stream is cooled by said expanded substantially condensed first gaseous stream sufficiently to partially condense it and is thereafter separated to form a volatile residue gas fraction containing a major portion of said methane and lighter components and a reflux stream;

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

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

9. The improvement according to claim 4 wherein said distillation column is a lower section of a fractionation tower and wherein said more volatile vapor distillation stream is cooled sufficiently to partially condense it in a portion of said tower above said distillation column and concurrently separated to form said volatile residue gas fraction and said reflux stream, whereupon said reflux stream flows to the top fractionation stage of said distillation column.

14. The improvement according to claim 4 wherein said more volatile vapor distillation stream is cooled sufficiently to partially condense it in a dephlegmator and concurrently separated to form said volatile residue gas fraction and said reflux stream, whereupon said reflux stream flows from the dephlegmator to the top fractionation stage of said distillation column.

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 gaseous stream and a second gaseous stream;

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

(5) said liquid stream is cooled and thereafter divided into at least a first portion and a second portion;

(6) said first portion is expanded to an intermediate pressure and thereafter warmed;

(7) said second portion is combined with said substantially condensed first gaseous stream, forming thereby a combined stream, whereupon said combined stream is expanded to said intermediate pressure;

(8) said expanded combined stream is directed in heat exchange relation with a more volatile vapor distillation stream which rises from fractionation stages of a distillation column and is thereby warmed;

(9) said second gaseous stream is expanded to said intermediate pressure;

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

(11) said more volatile vapor distillation stream is cooled by said expanded combined stream sufficiently to partially condense it and is thereafter separated to form a volatile residue gas fraction containing a major portion of said methane and lighter components and a reflux stream;

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

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

10. The improvement according to claim 5 wherein said distillation column is a lower section of a fractionation tower and wherein said more volatile vapor distillation stream is cooled sufficiently to partially condense it in a portion of said tower above said distillation column and concurrently separated to form said volatile residue gas fraction and said reflux stream, whereupon said reflux stream flows to the top fractionation stage of said distillation column.

15. The improvement according to claim 5 wherein said more volatile vapor distillation stream is cooled sufficiently to partially condense it in a dephlegmator and concurrently separated to form said volatile residue gas fraction and said reflux stream, whereupon said reflux stream flows from the dephlegmator to the top fractionation stage of said distillation column.

24. 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 gaseous stream and a second gaseous stream;

(3) second heat exchange means connected to said dividing means to receive said first gaseous 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 gaseous stream and expand it to an intermediate pressure;

(5) third heat exchange means connected to said first expansion means to receive said expanded substantially condensed first gaseous stream and heat it, said third heat exchange means being further connected to a distillation column to receive a more volatile vapor distillation stream rising from fractionation stages of said distillation column and cool it sufficiently to partially condense it;

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

(7) said distillation column being further connected to said third heat exchange means and said second expansion means to receive said heated expanded first gaseous stream and said expanded second gaseous 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;

(8) separation means connected to said third heat exchange means to receive said cooled partially condensed distillation stream and separate it into a volatile residue gas fraction containing a major portion of said methane and lighter components 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;

(9) fourth heat exchange means connected to said separation 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;

(10) 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

(11) control means adapted to regulate the quantities and temperatures of said feed streams to said distillation column to maintain the overhead temperature of said distillation column at a temperature whereby the major portion of said heavier hydrocarbon components is recovered in said relatively less volatile fraction.

29. The apparatus according to claim 24 wherein

(1) said distillation column is a lower section of a fractionation tower and wherein said more volatile vapor distillation stream is cooled sufficiently to partially condense it in a section of said fractionation tower above said distillation column and concurrently separated to form said volatile residue gas fraction and said reflux stream, whereupon said reflux stream flows to the top fractionation stage of said distillation column;

and

(2) said fourth heat exchange means is connected to said fractionation tower 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 said condensed stream.

34. The apparatus according to claim 24 wherein said apparatus includes

(1) a dephlegmator connected to said first expansion means to receive said expanded substantially condensed first gaseous stream and heat it, said dephlegmator being further connected to said distillation column to receive said more volatile vapor distillation stream and cool it sufficiently to partially condense it and concurrently separate it to form said volatile residue gas fraction and said reflux stream, said dephlegmator being further connected to said distillation column to supply said heated expanded first gaseous stream as a feed thereto and said reflux stream as a top feed thereto;

and

(2) said fourth heat exchange means connected to said dephlegmator 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 said condensed stream.

39. The apparatus according to claim 24 wherein said apparatus includes

(1) compressing means connected to said separating 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.

42. The apparatus according to claim 29, 30, or 31 wherein said apparatus includes

(1) compressing means connected to said fractionation tower 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.

44. The apparatus according to claim 34, 35, or 36 wherein said apparatus includes

(1) compressing means connected to said dephlegmator 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.

46. The apparatus according to claim 24 wherein said apparatus includes

(1) heating means connected to said separation 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.

49. The apparatus according to claim 29, 30, or 31 wherein said apparatus includes

(1) heating means connected to said fractionation tower 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.

51. The apparatus according to claim 34, 35, or 36 wherein said apparatus includes

(1) heating means connected to said dephlegmator 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.

53. The apparatus according to claim 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, or 46 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and C₂ components.

56. The apparatus according to claim 42 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and C₂ components.

58. The apparatus according to claim 44 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and C₂ components.

62. The apparatus according to claim 49 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and C₂ components.

64. The apparatus according to claim 51 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and C₂ components.

66. The apparatus according to claim 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, or 46 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, C₂ components, and C₃ components.

69. The apparatus according to claim 42 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, C₂ components, and C₃ components.

71. The apparatus according to claim 44 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, C₂ components, and C₃ components.

75. The apparatus according to claim 49 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, C₂ components, and C₃ components.

77. The apparatus according to claim 51 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, C₂ components, and C₃ components.

25. 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 gaseous stream and a second gaseous stream;

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

(6) third heat exchange means connected to said first expansion means to receive said expanded substantially condensed first gaseous stream and heat it, said third heat exchange means being further connected to a distillation column to receive a more volatile vapor distillation stream rising from fractionation stages of said distillation column and cool it sufficiently to partially condense it;

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

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

(9) said distillation column being further connected to said third heat exchange means, said second expansion means, and said third expansion means to receive said heated expanded first gaseous stream, said expanded second gaseous stream, and said expanded 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) second separation means connected to said third heat exchange means to receive said cooled partially condensed distillation stream and separate it into a volatile residue gas fraction containing a major portion of said methane and lighter components 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;

(11) fourth heat exchange means connected to said second separation 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) 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

(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.

30. The apparatus according to claim 25 wherein

(1) said distillation column is a lower section of a fractionation tower and wherein said more volatile vapor distillation stream is cooled sufficiently to partially condense it in a section of said fractionation tower above said distillation column and concurrently separated to form said volatile residue gas fraction and said reflux stream, whereupon said reflux stream flows to the top fractionation stage of said distillation column;

and

(2) said fourth heat exchange means is connected to said fractionation tower 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 said condensed stream.

35. The apparatus according to claim 25 wherein said apparatus includes

(1) a dephlegmator connected to said first expansion means to receive said expanded substantially condensed first gaseous stream and heat it, said dephlegmator being further connected to said distillation column to receive said more volatile vapor distillation stream and cool it sufficiently to partially condense it and concurrently separate it to form said volatile residue gas fraction and said reflux stream, said dephlegmator being further connected to said distillation column to supply said heated expanded first gaseous stream as a feed thereto and said reflux stream as a top feed thereto;

and

(2) said fourth heat exchange means connected to said dephlegmator 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 said condensed stream.

40. The apparatus according to claim 25 or 26 wherein said apparatus includes

(1) compressing means connected to said second separating 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.

47. The apparatus according to claim 25 or 26 wherein said apparatus includes

(1) heating means connected to said second separation 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.

54. The apparatus according to claim 40 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and C₂ components.

60. The apparatus according to claim 47 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and C₂ components.

67. The apparatus according to claim 40 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, C₂ components, and C₃ components.

73. The apparatus according to claim 47 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, C₂ components, and C₃ components.

26. 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 gaseous stream and a second gaseous stream;

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

(5) second heat exchange means connected to said 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) third heat exchange means connected to said first expansion means to receive said expanded substantially condensed combined stream and heat it, said third heat exchange means being further connected to a distillation column to receive a more volatile vapor distillation stream rising from fractionation stages of said distillation column and cool it sufficiently to partially condense it;

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

(9) 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;

(10) said distillation column being further connected to said third heat exchange means, said second expansion means, and said third expansion means to receive said heated expanded combined stream, said expanded second gaseous 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;

(11) second separation means connected to said third heat exchange means to receive said cooled partially condensed distillation stream and separate it into a volatile residue gas fraction containing a major portion of said methane and lighter components 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) fourth heat exchange means connected to said second separation 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;

(13) 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

(14) 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.

31. The apparatus according to claim 26 wherein

(1) said distillation column is a lower section of a fractionation tower and wherein said more volatile vapor distillation stream is cooled sufficiently to partially condense it in a section of said fractionation tower above said distillation column and concurrently separated to form said volatile residue gas fraction and said reflux stream, whereupon said reflux stream flows to the top fractionation stage of said distillation column;

and

(2) said fourth heat exchange means is connected to said fractionation tower 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 said condensed stream.

36. The apparatus according to claim 26 wherein said apparatus includes

(1) a dephlegmator connected to said first expansion means to receive said expanded substantially condensed combined stream and heat it, said dephlegmator being further connected to said distillation column to receive said more volatile vapor distillation stream and cool it sufficiently to partially condense it and concurrently separate it to form said volatile residue gas fraction and said reflux stream, said dephlegmator being further connected to said distillation column to supply said heated expanded combined stream as a feed thereto and said reflux stream as a top feed thereto;

and

(2) said fourth heat exchange means connected to said dephlegmator 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 said condensed stream.

27. 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) second heat exchange means connected to said first separation means to receive said liquid stream and cool it;

(4) first dividing means connected to said second heat exchange means to receive said cooled liquid stream and divide it into at least a first portion and a second portion;

(5) first expansion means connected to said first dividing means to receive said first portion and expand it to an intermediate pressure, said first expansion means being further connected to supply said expanded first portion to said second heat exchange means, thereby heating said expanded first portion while cooling said liquid stream;

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

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

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

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

(10) fourth expansion means connected to said first dividing means to receive said second portion and expand it to said intermediate pressure;

(11) fourth heat exchange means connected to said second expansion means to receive said expanded substantially condensed first gaseous stream and heat it, said fourth heat exchange means being further connected to a distillation column to receive a more volatile vapor distillation stream rising from fractionation stages of said distillation column and cool it sufficiently to partially condense it;

(12) said distillation column being further connected to said fourth heat exchange means, said third expansion means, said fourth expansion means, and said second heat exchange means to receive said heated expanded first gaseous stream, said expanded second gaseous stream, said expanded second portion, and said heated expanded first portion, 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;

(13) second separation means connected to said fourth heat exchange means to receive said cooled partially condensed distillation stream and separate it into a volatile residue gas fraction containing a major portion of said methane and lighter components 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) fifth heat exchange means connected to said second separation means to receive said volatile residue gas fraction, with said fifth 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) fifth expansion means connected to said fifth 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.

32. The apparatus according to claim 27 wherein

(1) said distillation column is a lower section of a fractionation tower and wherein said more volatile vapor distillation stream is cooled sufficiently to partially condense it in a section of said fractionation tower above said distillation column and concurrently separated to form said volatile residue gas fraction and said reflux stream, whereupon said reflux stream flows to the top fractionation stage of said distillation column;

and

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

37. The apparatus according to claim 27 wherein said apparatus includes

(1) a dephlegmator connected to said second expansion means to receive said expanded substantially condensed first gaseous stream and heat it, said dephlegmator being further connected to said distillation column to receive said more volatile vapor distillation stream and cool it sufficiently to partially condense it and concurrently separate it to form said volatile residue gas fraction and said reflux stream, said dephlegmator being further connected to said distillation column to supply said heated expanded first gaseous stream as a feed thereto and said reflux stream as a top feed thereto;

and

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

41. The apparatus according to claim 27 or 28 wherein said apparatus includes

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

and

(2) said fifth heat exchange means connected to said compressing means to receive said compressed volatile residue gas fraction, with said fifth 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.

43. The apparatus according to claim 32 or 33 wherein said apparatus includes

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

and

(2) said fifth heat exchange means connected to said compressing means to receive said compressed volatile residue gas fraction, with said fifth 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.

45. The apparatus according to claim 37 or 38 wherein said apparatus includes

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

and

(2) said fifth heat exchange means connected to said compressing means to receive said compressed volatile residue gas fraction, with said fifth 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.

48. The apparatus according to claim 27 or 28 wherein said apparatus includes

(1) heating means connected to said second separation 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 fifth heat exchange means connected to said compressing means to receive said compressed heated volatile residue gas fraction,with said fifth 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.

50. The apparatus according to claim 32 or 33 wherein said apparatus includes

(1) heating means connected to said fractionation tower 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 fifth heat exchange means connected to said compressing means to receive said compressed heated volatile residue gas fraction, with said fifth 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.

52. The apparatus according to claim 37 or 38 wherein said apparatus includes

(1) heating means connected to said dephlegmator 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 fifth heat exchange means connected to said compressing means to receive said compressed heated volatile residue gas fraction, with said fifth 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.

55. The apparatus according to claim 41 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and C₂ components.

57. The apparatus according to claim 43 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and C₂ components.

59. The apparatus according to claim 45 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and C₂ components.

61. The apparatus according to claim 48 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and C₂ components.

63. The apparatus according to claim 50 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and C₂ components.

65. The apparatus according to claim 52 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, and C₂ components.

68. The apparatus according to claim 41 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, C₂ components, and C₃ components.

70. The apparatus according to claim 43 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, C₂ components, and C₃ components.

72. The apparatus according to claim 45 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, C₂ components, and C₃ components.

74. The apparatus according to claim 48 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, C₂ components, and C₃ components.

76. The apparatus according to claim 50 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, C₂ components, and C₃ components.

78. The apparatus according to claim 52 wherein said volatile residue gas fraction contains a major portion of said methane, lighter components, C₂ components, and C₃ components.

28. 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) second heat exchange means connected to said first separation means to receive said liquid stream and cool it;

(4) first dividing means connected to said second heat exchange means to receive said cooled liquid stream and divide it into at least a first portion and a second portion;

(5) first expansion means connected to said first dividing means to receive said first portion and expand it to an intermediate pressure, said first expansion means being further connected to supply said expanded first portion to said second heat exchange means, thereby heating said expanded first portion while cooling said liquid stream;

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

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

(8) combining means connected to said third heat exchange means and to said first dividing means to receive said substantially condensed first gaseous stream and said second portion and form thereby a combined stream;

(9) second expansion means connected to said combining means to receive said combined stream and expand it to said intermediate pressure;

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

(11) fourth heat exchange means connected to said second expansion means to receive said expanded combined stream and heat it, said fourth heat exchange means being further connected to a distillation column to receive a more volatile vapor distillation stream rising from fractionation stages of said distillation column and cool it sufficiently to partially condense it;

(12) said distillation column being further connected to said fourth heat exchange means, said third expansion means, and said second heat exchange means to receive said heated expanded combined stream, said expanded second gaseous stream, and said heated expanded first portion, 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;

(13) second separation means connected to said fourth heat exchange means to receive said cooled partially condensed distillation stream and separate it into a volatile residue gas fraction containing a major portion of said methane and lighter components 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) fifth heat exchange means connected to said second separation means to receive said volatile residue gas fraction, with said fifth 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 first fifth 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.

33. The apparatus according to claim 28 wherein

(1) said distillation column is a lower section of a fractionation tower and wherein said more volatile vapor distillation stream is cooled sufficiently to partially condense it in a section of said fractionation tower above said distillation column and concurrently separated to form said volatile residue gas fraction and said reflux stream, whereupon said reflux stream flows to the top fractionation stage of said distillation column;

and

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

38. The apparatus according to claim 28 wherein said apparatus includes

(1) a dephlegmator connected to said second expansion means to receive said expanded combined stream and heat it, said dephlegmator being further connected to said distillation column to receive said more volatile vapor distillation stream and cool it sufficiently to partially condense it and concurrently separate it to form said volatile residue gas fraction and said reflux stream, said dephlegmator being further connected to said distillation column to supply said heated expanded combined stream as a feed thereto and said reflux stream as a top feed thereto;

and

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