Purification of Carbon Dioxide

• US 20150114034A1
• Filed: 10/25/2013
• Published: 04/30/2015
• Est. Priority Date: 10/25/2013
• Status: Abandoned Application

• Current Assignee: Air Products and Chemicals Incorporated (Linde Plc)
• Original Assignee: Air Products and Chemicals Incorporated (Linde Plc)
• Inventors: Higginbotham, Paul, Guvelioglu, Galip Hakan, Palamara, John Eugene, White, Vincent
• Application Number:
  US14/063,067
• Publication Number:
  US 20150114034A1
• Time in Patent Office: Days
• US Class Current: 62/617
• CPC Class Codes: B01D 2257/302 Sulfur oxides
• CPC Class Codes: B01D 2257/304 Hydrogen sulfide
• CPC Class Codes: B01D 2257/306 Organic sulfur compounds, e.g. mercaptans
• CPC Class Codes: B01D 2257/308 Carbonoxysulfide COS
• CPC Class Codes: B01D 2257/404 Nitrogen oxides other than dinitrogen oxide
• CPC Class Codes: B01D 2257/406 Ammonia
• CPC Class Codes: B01D 2257/7022 Aliphatic hydrocarbons
• CPC Class Codes: B01D 53/002 by condensation
• CPC Class Codes: B01D 53/75 Multi-step processes
• CPC Class Codes: C01B 17/167 Separation
• CPC Class Codes: C01B 32/50 Carbon dioxide
• 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 2200/40 Features relating to the provision of boil-up in the bottom of a column
• CPC Class Codes: F25J 2200/50 using multiple (re-)boiler-condensers at different heights of the column
• CPC Class Codes: F25J 2200/74 Refluxing the column with at least a part of the partially condensed overhead gas
• CPC Class Codes: F25J 2200/76 Refluxing the column with condensed overhead gas being cycled in a quasi-closed loop refrigeration cycle
• 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 2205/02 using simple phase separation in a vessel or drum
• CPC Class Codes: F25J 2215/80 Carbon dioxide
• CPC Class Codes: F25J 2220/82 : Separating low boiling, i.e. more volatile components, e.g. He, H2, CO, Air gases, CH4
• CPC Class Codes: F25J 2220/84 : Separating high boiling, i.e. less volatile components, e.g. NOx, SOx, H2S
• CPC Class Codes: F25J 2230/80 : the fluid being carbon dioxide
• CPC Class Codes: F25J 2235/02 : using a pump in general or hydrostatic pressure increase
• CPC Class Codes: F25J 2235/80 : the fluid being carbon dioxide
• CPC Class Codes: F25J 2240/40 : Expansion without extracting work, i.e. isenthalpic throttling, e.g. JT valve, regulating valve or venturi, or isentropic nozzle, e.g. Laval
• CPC Class Codes: F25J 2245/02 : Recycle of a stream in general, e.g. a by-pass stream
• CPC Class Codes: F25J 2260/20 : Integration in an installation for liquefying or solidifying a fluid stream
• CPC Class Codes: F25J 2260/80 : Integration in an installation using carbon dioxide, e.g. for EOR, sequestration, refrigeration etc.
• CPC Class Codes: F25J 2270/02 : Internal refrigeration with liquid vaporising loop
• CPC Class Codes: F25J 2270/80 : Quasi-closed internal or closed external carbon dioxide refrigeration cycle
• CPC Class Codes: F25J 2270/88 : Quasi-closed internal refrigeration or heat pump cycle, if not otherwise provided
• 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 3/08 : Separating gaseous impurities from gases or gaseous mixtures or from liquefied gases or liquefied gaseous mixturescold traps B01D8/00
• CPC Class Codes: Y02P 20/129 : Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines
• CPC Class Codes: Y02P 20/151 : Reduction of greenhouse gas [GHG] emissions, e.g. CO2

Abstract

In a process for separating “heavy” impurities such as hydrogen sulfide from crude carbon dioxide comprising significant quantities of “light” impurities such as non-condensable gases, involving at least one heat pump cycle using as working fluid a fluid from the “heavy” impurity separation, the “light” impurities are removed from carbon dioxide-enriched gas generated in the “heavy” impurity separation. The carbon dioxide-enriched gas, or a compressed carbon dioxide-enriched gas produced therefrom, is at least partially condensed by indirect heat exchange against intermediate liquid also generated in the “heavy” impurity separation. Total and specific energy consumption is reduced compared to conventional processes in which “light” impurities are removed from carbon dioxide product gas.

Claims

1. A process for purifying crude carbon dioxide fluid comprising at least one “

light”

impurity and at least one “

heavy”

impurity, said process comprising;

cooling said crude carbon dioxide fluid above the triple point pressure of carbon dioxide by indirect heat exchange to produce cooled crude carbon dioxide fluid;

feeding said cooled crude carbon dioxide fluid to a first column system for mass transfer separation to produce carbon dioxide-enriched overhead vapor comprising said “

light”

impurity, and “

heavy”

impurity-enriched bottoms liquid depleted in said “

light”

impurity;

re-boiling said first column system by at least partially vaporizing at least one “

heavy”

impurity-enriched liquid in or taken from said first column system by indirect heat exchange to provide vapor for said first column system;

cooling and at least partially condensing carbon dioxide-enriched overhead vapor, or a compressed carbon dioxide-enriched gas produced therefrom, by indirect heat exchange to produce at least partially condensed carbon dioxide-enriched gas comprising said “

light”

impurity;

separating said at least partially condensed carbon dioxide-enriched gas to produce “

light”

impurity-enriched gas, and carbon dioxide-enriched liquid; and

providing at least a portion of said carbon dioxide-enriched liquid as reflux for said first column system,

wherein said first column system operates above the triple point pressure and below the critical pressure of carbon dioxide; and

wherein said process comprises at least one heat pump cycle using as working fluid a fluid from said first column system.

2. The process of claim 1, wherein said at least partially condensed carbon dioxide-enriched gas is expanded prior to said separation to produce said “

light”

impurity-enriched gas and said carbon dioxide-enriched liquid.

3. The process of claim 1, wherein said carbon dioxide-enriched overhead vapor, or said compressed carbon dioxide-enriched gas produced therefrom, is partially condensed by said indirect heat exchange to produce partially condensed carbon dioxide-enriched gas.

4. The process of claim 1, wherein said carbon dioxide-enriched liquid is separated from said “

light”

impurity-enriched gas by phase separation.

5. The process of claim 1, wherein said carbon dioxide-enriched liquid is separated from said “

light”

impurity-enriched gas by mass transfer separation in a second column system.

6. The process of claim 1, wherein at least part of the vaporization duty required for re-boiling said first column system is provided by at least one stream selected from the group consisting of at least one recycle stream in said heat pump cycle(s);

and said crude carbon dioxide fluid.

7. The process of claim 1, wherein said “

heavy”

impurity-enriched liquid(s) providing vapor for said first column system comprises an intermediate liquid in or taken from an intermediate location in said first column system.

8. The process of claim 7, wherein at least part of the vaporization duty required for vaporizing said intermediate liquid is provided by at least one recycle stream in said heat pump cycle(s).

9. The process of claim 7, wherein at least part of the vaporization duty required for vaporizing said intermediate liquid is provided by said carbon dioxide-enriched overhead vapor.

10. The process of claim 1, wherein said “

heavy”

impurity-enriched liquid(s) providing vapor for said first column system comprises said “

heavy”

impurity-enriched bottoms liquid.

11. The process of claim 10, wherein at least part of the vaporization duty required for vaporizing said bottoms liquid is provided by said crude carbon dioxide fluid.

12. The process of claim 1, wherein said “

light”

impurity-enriched gas is removed from the process as product gas.

13. The process of claim 1, wherein carbon dioxide is recovered from said “

light”

impurity-enriched gas producing a “

light”

impurity-rich residual gas which is optionally purged from the process.

14. The process of claim 1, wherein said “

light”

impurity-enriched gas, or a “

light”

impurity-rich residual gas produced therefrom, is not recycled with said working fluid of said heat pump cycle.

15. The process of claim 1, wherein said working fluid is carbon dioxide-enriched overhead vapor, said heat pump cycle comprising:

warming said carbon dioxide-enriched overhead vapor by indirect heat exchange to produce warmed carbon dioxide-enriched gas; and

compressing said warmed carbon dioxide-enriched gas to produce said compressed carbon dioxide-enriched gas,

wherein said compressed carbon dioxide-enriched gas is used to provide at least part of the vaporization duty required for at least partially vaporizing said “

heavy”

impurity-enriched liquid(s), thereby cooling and partially condensing said carbon dioxide-enriched gas to produce partially condensed carbon dioxide-enriched gas comprising said “

light”

impurity.

16. The process of claim 15, wherein said compressed carbon dioxide-enriched gas is cooled by indirect heat exchange prior to providing said vaporization duty.

17. The process of claim 15, wherein said carbon dioxide-enriched liquid is cooled by indirect heat exchange prior to providing said reflux to said first column system.

18. The process of claim 15, wherein said carbon dioxide-enriched liquid is expanded prior to providing said reflux to said first column system.

19. The process of claim 15, said process comprising:

expanding a portion of said carbon dioxide-enriched liquid to produce expanded carbon dioxide-enriched liquid;

vaporizing said expanded carbon dioxide-enriched liquid by indirect heat exchange to produce carbon dioxide-enriched product gas; and

compressing said carbon dioxide-enriched product gas to produce compressed carbon dioxide-enriched product gas.

20. The process of claim 15, said process comprising:

pumping a portion of said carbon dioxide-enriched liquid to produce pumped carbon dioxide-enriched liquid; and

vaporizing said pumped carbon dioxide-enriched liquid by indirect heat exchange to produce carbon dioxide-enriched product gas.

21. The process of claim 20, wherein said carbon dioxide-enriched product gas is compressed to produce compressed carbon dioxide-enriched product gas.

22. The process of claim 15, said process comprising:

warming said “

light”

impurity-enriched gas by indirect heat exchange to produce warmed “

light”

impurity-enriched gas;

compressing said “

light”

impurity-enriched gas to produce compressed “

light”

impurity-enriched gas; and

using said compressed “

light”

impurity-enriched gas to provide vaporization duty by indirect heat exchange, thereby at least partially condensing said gas to produce at least partially condensed “

light”

impurity-enriched gas.

23. The process of claim 15, wherein carbon dioxide is recovered from said “

light”

impurity-enriched gas to produce “

light”

impurity-rich residual gas and recovered carbon dioxide.

24. The process of claim 23, said process comprising:

cooling and partially condensing said “

light”

impurity-enriched gas to produce partially condensed “

light”

impurity-enriched gas; and

phase separating said partially condensed “

light”

impurity-enriched gas to produce said “

light”

impurity-rich residual gas and recovered carbon dioxide liquid.

25. The process of claim 24, wherein at least a portion of said recovered carbon dioxide liquid is fed as reflux to said second column system.

26. The process of claim 25, wherein said recovered carbon dioxide liquid is warmed by indirect heat exchange prior to being fed as said reflux to said second column system.

27. The process of claim 23, wherein said “

light”

impurity-enriched gas, or compressed “

light”

impurity-enriched gas produced therefrom, is cooled by indirect heat exchange prior to carbon dioxide recovery, said carbon dioxide being recovered as a liquid.

28. The process of claim 27, the process comprising:

expanding said recovered carbon dioxide liquid to produce expanded recovered carbon dioxide liquid; and

vaporizing said expanded recovered carbon dioxide liquid by indirect heat exchange to produce recovered carbon dioxide gas,

wherein said recovered carbon dioxide gas is combined with said carbon dioxide-enriched overhead vapor prior to said warming to produce said warmed carbon dioxide-enriched gas.

29. The process of claim 27, the process comprising:

expanding said recovered carbon dioxide liquid to produce expanded recovered carbon dioxide liquid;

vaporizing and optionally warming said expanded recovered carbon dioxide liquid by indirect heat exchange to produce recovered carbon dioxide gas; and

compressing said recovered carbon dioxide gas to produce compressed recovered carbon dioxide gas,

wherein said compressed recovered carbon dioxide gas is combined with said warmed carbon dioxide-enriched gas prior to said compression to produce said compressed carbon dioxide-enriched gas.

30. The process of claim 28 or claim 29, wherein said recovered carbon dioxide liquid is warmed by indirect heat exchange prior to said expansion.

31. The process of claim 23, wherein said “

light”

impurity-rich residual gas is warmed by indirect heat exchange and purged from the process.

32. The process of claim 23, wherein said “

light”

impurity-enriched gas, or compressed “

light”

impurity-enriched gas produced therefrom, is warmed by indirect heat exchange prior to carbon dioxide recovery, said carbon dioxide being recovered as a gas.

33. The process of claim 32, wherein carbon dioxide is recovered from said “

light”

impurity-enriched gas using a process selected from the group consisting of adsorption;

absorption;

membrane separation; and

solidification.

34. The process of claim 1, wherein said working fluid is an intermediate liquid taken from said first column system, said heat pump cycle comprising:

expanding said intermediate liquid to produce expanded intermediate liquid;

vaporizing said expanded intermediate liquid by indirect heat exchange against said carbon dioxide-enriched overhead vapor to produce intermediate gas and said carbon dioxide-enriched liquid for use as said reflux to said first column system;

compressing said intermediate gas to produce compressed intermediate gas; and

cooling said compressed intermediate gas by indirect heat exchange to produce cooled intermediate gas,

wherein said cooled intermediate gas is fed to an intermediate location in said first column system to provide at least a portion of said vapor for said first column system.

35. The process of claim 34, wherein said intermediate gas is warmed by indirect heat exchange prior to said compression.

36. The process of claim 1, wherein said crude carbon dioxide fluid is at a pressure greater than the operating pressure of said first column system, said process comprising expanding said cooled crude carbon dioxide fluid prior to feeding to said first column system.

37. The process of claim 1, wherein said crude carbon dioxide fluid is at about the same pressure as the operating pressure of said first column system.

38. The process of claim 1, said process comprising:

pumping said “

heavy”

impurity-enriched bottoms liquid to produce pumped bottoms liquid;

warming said pumped bottoms liquid by indirect heat exchange to produce warmed bottoms liquid; and

pumping said warmed bottoms liquid to produce pumped waste liquid.

39. The process of claim 1, wherein the majority of the total refrigeration duty required by the process is provided by at least one fluid selected from the group consisting of carbon dioxide-enriched liquid;

a “

heavy”

impurity-enriched intermediate liquid; and

“

heavy”

impurity-enriched bottoms liquid.

40. The process of claim 1, wherein the majority of the total vaporization duty required by the process is provided by at least one fluid selected from the group consisting of said crude carbon dioxide fluid;

and at least one recycle stream from said heat pump cycle(s).

41. The process of claim 1, wherein said process is auto-refrigerated.

42. The process of claim 1, wherein at least one “

light”

impurity is selected from the group consisting of hydrogen;

methane;

C₂ hydrocarbons; and

mixtures thereof, said “

light”

impurity-rich residual vapor being used as a fuel for combustion to produce combustion product gas.

43. The process of claim 42, wherein heat is recovered from said combustion product gas by indirect heat exchange.

44. The process of claim 1, wherein said crude carbon dioxide fluid comprises carbon dioxide in an amount of at least about 50 mol %.

45. The process of claim 1, wherein said crude carbon dioxide fluid comprises said at least one “

light”

impurity in an amount of no more than about 50 mol % in total.

46. The process of claim 1, wherein said crude carbon dioxide fluid comprises said at least one “

heavy”

impurity in an amount of no more than about 50 mol % in total.

47. The process of claim 1 wherein at least one “

light”

impurity is selected from the group consisting of nitrogen;

oxygen;

argon;

neon;

xenon;

krypton;

carbon monoxide;

nitric oxide;

nitrous oxide;

hydrogen;

helium;

methane; and

C₂ hydrocarbons.

48. The process of claim 1, wherein at least one “

heavy”

impurity is selected from the group consisting of hydrogen sulfide;

methanol;

C₃ to C₈ hydrocarbons;

carbon disulfide;

carbon oxysulfide;

dimethyl sulfide and other organic sulfur compounds;

nitrogen dioxide, sulfur dioxide;

sulfur trioxide; and

ammonia.

49. The process of claim 1, wherein at least one “

heavy”

impurity is hydrogen sulfide.

50. The process of claim 49, wherein at least one “

light”

impurity is selected from the group consisting of nitrogen;

argon;

helium;

methane; and

ethane.

51. The process of claim 13, wherein said “

light”

impurity-rich residual gas comprises methane, nitrogen and helium, said process comprising rejecting nitrogen and helium from methane and recovering helium from the rejection process.

52. The process of claim 1, wherein the operating pressure(s) of said first column system is from about 5.2 bar to about 40 bar, and preferably from 15 bar to about 25 bar.

53. The process of claim 1, wherein the at least partially condensed carbon dioxide-enriched gas is separated to produce “

light”

impurity-enriched gas and carbon dioxide-enriched liquid at a pressure from about 5.2 bar to about 60 bar, and preferably from about 15 bar to about 50 bar.

54. The process of claim 1, wherein said cooled crude carbon dioxide fluid is in at least partially condensed form, said fluid being expanded to the operating pressure of said first column system and at least partially vaporized by indirect heat exchange prior to being fed to said first column system.

55. Apparatus for purifying crude carbon dioxide fluid comprising at least one “

light”

impurity and at least one “

heavy”

impurity, said apparatus comprising;

a first heat exchanger for cooling said crude carbon dioxide fluid by indirect heat exchange to produce cooled crude carbon dioxide fluid;

a first column system in fluid flow communication with said first heat exchanger for separating said cooled crude carbon dioxide fluid by mass transfer separation to produce carbon dioxide-enriched overhead vapor comprising said “

light”

impurity, and “

heavy”

impurity-enriched bottoms liquid depleted in said “

light”

impurity;

at least one second heat exchanger for re-boiling by indirect heat exchange a “

heavy”

impurity-enriched liquid in or taken from said first column system to provide vapor for said first column system;

a third heat exchanger for cooling and at least partially condensing carbon dioxide-enriched overhead vapor, or a compressed carbon dioxide-enriched gas produced therefrom, by indirect heat exchange to produce at least partially condensed carbon dioxide-enriched gas comprising said “

light”

impurity;

a separation unit in fluid flow communication with said third heat exchanger for separating at least partially condensed carbon dioxide-enriched gas to produce “

light”

impurity-enriched gas and carbon dioxide-enriched liquid; and

a conduit arrangement for providing carbon dioxide-enriched liquid as reflux for said first column system,

wherein said apparatus comprises at least one heat pump cycle using as working fluid a fluid from said first column system.

56. The apparatus of claim 55, comprising a first pressure reduction arrangement between said third heat exchanger and said separation unit for expanding said at least partially condensed carbon dioxide-enriched gas prior to said separation unit.

57. The apparatus of claim 55, wherein said separation unit is a phase separator.

58. The apparatus of claim 55, wherein said separation unit is a second column system for mass transfer separation.

59. The apparatus of claim 55, wherein said second heat exchanger is arranged to re-boil an intermediate liquid in or taken from an intermediate location from said first column system.

60. The apparatus of claim 59, wherein said second heat exchanger is arranged to re-boil said intermediate liquid by indirect heat exchange against at least one recycle stream in said heat pump cycle(s).

61. The apparatus of claim 59, wherein said second heat exchanger is arranged to re-boil said intermediate liquid by indirect heat exchange against carbon dioxide-enriched overhead vapor.

62. The apparatus of claim 55, wherein said second heat exchanger is arranged to re-boil said “

heavy”

impurity-enriched bottoms liquid.

63. The apparatus of claim 62, wherein said second heat exchanger is arranged to re-boil said bottoms liquid by indirect heat exchange against said crude carbon dioxide fluid.

64. The apparatus of claim 55, wherein said working fluid is carbon dioxide-enriched overhead vapor, said heat pump cycle comprising:

a fourth heat exchanger in fluid flow communication with said first column system for warming carbon dioxide-enriched overhead vapor by indirect heat exchange to produce warmed carbon dioxide-enriched gas;

a first compressor in fluid flow communication with said fourth heat exchanger for compressing said warmed carbon dioxide-enriched gas to produce said compressed carbon dioxide-enriched gas;

wherein said second heat exchanger is arranged to vaporize said “

heavy”

impurity-enriched liquid by indirect heat exchange against said compressed carbon dioxide-enriched gas.

65. The apparatus of claim 64, said apparatus comprising a fifth heat exchanger in said fluid flow communication between said first compressor and said second heat exchanger to cool said compressed carbon dioxide-enriched gas prior to said second heat exchanger.

66. The apparatus of claim 64, wherein said conduit arrangement for feeding said carbon dioxide-enriched liquid as reflux to said first column system comprises a sixth heat exchanger for cooling said liquid prior to said first column system.

67. The apparatus of claim 64, wherein said conduit arrangement for feeding said carbon dioxide-enriched liquid as reflux to said first column system comprises a second pressure reduction arrangement for expanding the liquid prior to said first column system.

68. The apparatus of claim 64, said apparatus comprising:

a third pressure reduction arrangement in fluid flow communication with said separation unit for expanding carbon dioxide-enriched liquid to produce expanded carbon dioxide-enriched liquid;

a seventh heat exchanger in fluid flow communication with said third pressure reduction arrangement for vaporizing said expanded carbon dioxide-enriched liquid by indirect heat exchange to produce carbon dioxide-enriched gas; and

a second compressor in fluid flow communication with said seventh heat exchanger for compressing carbon dioxide-enriched gas to produce compressed carbon dioxide-enriched product gas.

69. The apparatus of claim 68, said apparatus comprising a eighth heat exchanger in said fluid flow communication between said separation unit and said third pressure reduction arrangement to warm said carbon dioxide-enriched liquid by indirect heat exchange prior to said expansion.

70. The apparatus of claim 64, said apparatus comprising:

a fourth pressure reduction arrangement in fluid flow communication with said separation unit for expanding carbon dioxide-enriched liquid to produce expanded carbon dioxide-enriched liquid;

a ninth heat exchanger in fluid flow communication with said pressure reduction arrangement for vaporizing said expanded carbon dioxide-enriched liquid by indirect heat exchange to produce carbon-dioxide-enriched gas; and

a third compressor in fluid flow communication with said ninth heat exchanger for compression said carbon dioxide-enriched gas to produce compressed carbon dioxide-enriched product gas.

71. The apparatus of claim 64, said apparatus comprising:

a first pump in fluid flow communication with said separation unit for pumping carbon dioxide-enriched liquid to produce pumped carbon dioxide-enriched liquid;

a tenth heat exchanger in fluid flow communication with said first pump for vaporizing said pumped carbon dioxide-enriched liquid by indirect heat exchange to produce carbon dioxide-enriched product gas.

72. The apparatus of claim 71, comprising a fourth compressor in fluid flow communication with said tenth heat exchanger for compressing carbon dioxide-enriched product gas to produce compressed carbon dioxide-enriched product gas.

73. The apparatus of claim 64, said apparatus comprising:

an eleventh heat exchanger in fluid flow communication with said separation unit for warming “

light”

impurity-enriched gas by indirect heat exchange to produce warmed “

light”

impurity-enriched gas;

a fifth compressor in fluid flow communication with said eleventh heat exchanger for compressing said warmed “

light”

impurity-enriched gas to produce compressed “

light”

impurity-enriched gas; and

a twelfth heat exchanger in fluid flow communication with said fifth compressor arranged such that said compressed “

light”

impurity-enriched gas is at least partially condensed by indirect heat exchange.

74. The apparatus of claim 64, said apparatus comprising:

a thirteenth heat exchanger in fluid flow communication with said separation unit for cooling and partially condensing “

light”

impurity-enriched gas by indirect heat exchange to produce partially condensed “

light”

impurity-enriched gas; and

a first phase separator in fluid flow communication with said thirteenth heat exchanger for separating partially condensed “

light”

impurity-enriched gas to produce “

light”

impurity-rich residual gas and recovered carbon dioxide liquid.

75. The apparatus of claim 74, wherein said separation unit is a second column system for mass transfer separation, said apparatus comprising a conduit arrangement for feeding recovered carbon dioxide liquid from said first phase separator as reflux to said second column system.

76. The apparatus of claim 75, said conduit arrangement comprising a fourteenth heat exchanger for warming recovered carbon dioxide liquid by indirect heat exchange to produce warmed recovered carbon dioxide liquid prior to being fed as reflux to said second column system.

77. The apparatus of claim 74, said apparatus comprising:

a fifth pressure reduction arrangement in fluid flow communication with said first phase separator for expanding said recovered carbon dioxide liquid to produce expanded recovered carbon dioxide liquid;

a fifteenth heat exchanger in fluid flow communication with said fifth pressure reduction arrangement for vaporizing said expanded recovered carbon dioxide liquid by indirect heat exchange to produce recovered carbon dioxide gas; and

a conduit arrangement for combining recovered carbon dioxide gas with carbon dioxide-enriched overhead vapor prior to said fourth heat exchanger.

78. The apparatus of claim 77, said apparatus comprising a sixteenth heat exchanger in said fluid flow communication between said first phase separator and said fifth pressure reduction arrangement for warming said recovered carbon dioxide liquid by indirect heat exchange prior to said expansion.

79. The apparatus of claim 74, said apparatus comprising:

a sixth pressure reduction arrangement in fluid flow communication with said first phase separator for expanding recovered carbon dioxide liquid to produce expanded recovered carbon dioxide liquid;

a seventeenth heat exchanger in fluid flow communication with said sixth pressure reduction arrangement for vaporizing and optionally warming expanded recovered carbon dioxide liquid by indirect heat exchange to produce warmed recovered carbon dioxide gas;

a sixth compressor in fluid flow communication with said seventeenth heat exchanger for compressing warmed recovered carbon dioxide gas to produce compressed recovered carbon dioxide gas; and

a conduit arrangement for combining compressed recovered carbon dioxide gas with warmed carbon dioxide-enriched gas prior to said first compressor.

80. The apparatus of claim 74, said apparatus comprising:

a eighteenth heat exchanger in fluid flow communication with said first phase separator for warming “

light”

impurity-rich residual gas by indirect heat exchange to produce warmed “

light”

impurity-rich residual gas; and

a vent in fluid flow communication with said eighteenth heat exchanger for purging said warmed “

light”

impurity-rich residual gas from said apparatus.

81. The apparatus of claim 55 wherein said working fluid is an intermediate liquid taken from said first column system, said heat pump cycle comprising:

a seventh pressure reduction arrangement in fluid flow communication with said first column system for expanding said intermediate liquid to produce expanded intermediate liquid;

a nineteenth heat exchanger in fluid flow communication with said seventh pressure reduction arrangement for vaporizing said expanded intermediate liquid by indirect heat exchange against said carbon dioxide-enriched overhead vapor to produce intermediate gas and said carbon dioxide-enriched liquid for use as said reflux to said first column system;

a seventh compressor in fluid flow communication with said nineteenth heat exchanger for compressing intermediate gas to produce compressed intermediate gas;

a twentieth heat exchanger in fluid flow communication with said seventh compressor for cooling compressed intermediate gas by indirect heat exchange to produce cooled intermediate gas; and

a conduit arrangement for feeding cooled intermediate gas from said twentieth heat exchanger to an intermediate location in said first column system to provide at least a portion of said vapor for said first column system.

82. The apparatus of claim 81, said apparatus comprising a twenty-first heat exchanger in said fluid flow communication between said nineteenth heat exchanger and said seventh compressor for warming said intermediate gas prior to said compression.

83. The apparatus of claim 55, said apparatus comprising an eighth pressure reduction arrangement for expanding said cooled crude carbon dioxide fluid prior to feeding to said first column system.

84. The apparatus of claim 55, said apparatus comprising:

a second pump in fluid flow communication with said first column system for pumping “

heavy”

impurity-enriched bottoms liquid to produce pumped bottoms liquid;

a twenty-second heat exchanger in fluid flow communication with said second pump for warming pumped bottoms liquid by indirect heat exchange to produce warmed bottoms liquid; and

a third pump in fluid flow communication with said twenty-second heat exchanger for pumping warmed bottoms liquid to produce pumped waste liquid.

85. The apparatus of claim 55, said apparatus comprising:

an eighth pressure reduction arrangement in said fluid flow communication between said first heat exchanger and said first column system for expanding at least partially condensed cooled crude carbon dioxide fluid; and

a twenty-third heat exchanger in said fluid flow communication between said first heat exchanger and said first column system for at least partially vaporizing expanded crude carbon dioxide fluid prior to said first column system.

86. The apparatus of claim 55, wherein said heat exchangers are zones within a single main heat exchanger.