EP0580345A1 - Elevated pressure liquefier - Google Patents

Elevated pressure liquefier Download PDF

Info

Publication number
EP0580345A1
EP0580345A1 EP93305480A EP93305480A EP0580345A1 EP 0580345 A1 EP0580345 A1 EP 0580345A1 EP 93305480 A EP93305480 A EP 93305480A EP 93305480 A EP93305480 A EP 93305480A EP 0580345 A1 EP0580345 A1 EP 0580345A1
Authority
EP
European Patent Office
Prior art keywords
stream
low pressure
column
air feed
argon
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP93305480A
Other languages
German (de)
French (fr)
Other versions
EP0580345B1 (en
Inventor
Lawrence Walter Pruneski
Rakesh Agrawal
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Air Products and Chemicals Inc
Original Assignee
Air Products and Chemicals Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Air Products and Chemicals Inc filed Critical Air Products and Chemicals Inc
Publication of EP0580345A1 publication Critical patent/EP0580345A1/en
Application granted granted Critical
Publication of EP0580345B1 publication Critical patent/EP0580345B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04284—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams
    • F25J3/04309—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams of nitrogen
    • F25J3/04315—Lowest pressure or impure nitrogen, so-called waste nitrogen expansion
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04333—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using quasi-closed loop internal vapor compression refrigeration cycles, e.g. of intermediate or oxygen enriched (waste-)streams
    • F25J3/04351—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using quasi-closed loop internal vapor compression refrigeration cycles, e.g. of intermediate or oxygen enriched (waste-)streams of nitrogen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04284—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams
    • F25J3/0429—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams of feed air, e.g. used as waste or product air or expanded into an auxiliary column
    • F25J3/04296—Claude expansion, i.e. expanded into the main or high pressure column
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04333—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using quasi-closed loop internal vapor compression refrigeration cycles, e.g. of intermediate or oxygen enriched (waste-)streams
    • F25J3/04339—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using quasi-closed loop internal vapor compression refrigeration cycles, e.g. of intermediate or oxygen enriched (waste-)streams of air
    • F25J3/04345—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using quasi-closed loop internal vapor compression refrigeration cycles, e.g. of intermediate or oxygen enriched (waste-)streams of air and comprising a gas work expansion loop
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04375—Details relating to the work expansion, e.g. process parameter etc.
    • F25J3/04393—Details relating to the work expansion, e.g. process parameter etc. using multiple or multistage gas work expansion
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04406—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using a dual pressure main column system
    • F25J3/04412—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using a dual pressure main column system in a classical double column flowsheet, i.e. with thermal coupling by a main reboiler-condenser in the bottom of low pressure respectively top of high pressure column
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04642—Recovering noble gases from air
    • F25J3/04648—Recovering noble gases from air argon
    • F25J3/04654—Producing crude argon in a crude argon column
    • F25J3/04666—Producing crude argon in a crude argon column as a parallel working rectification column of the low pressure column in a dual pressure main column system
    • F25J3/04672—Producing crude argon in a crude argon column as a parallel working rectification column of the low pressure column in a dual pressure main column system having a top condenser
    • F25J3/04678—Producing crude argon in a crude argon column as a parallel working rectification column of the low pressure column in a dual pressure main column system having a top condenser cooled by oxygen enriched liquid from high pressure column bottoms
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/20—Processes or apparatus using separation by rectification in an elevated pressure multiple column system wherein the lowest pressure column is at a pressure well above the minimum pressure needed to overcome pressure drop to reject the products to atmosphere
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/50—Processes or apparatus using separation by rectification using multiple (re-)boiler-condensers at different heights of the column
    • F25J2200/52—Processes or apparatus using separation by rectification using multiple (re-)boiler-condensers at different heights of the column in the high pressure column of a double pressure main column system
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/02—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2245/00—Processes or apparatus involving steps for recycling of process streams
    • F25J2245/42—Processes or apparatus involving steps for recycling of process streams the recycled stream being nitrogen

Definitions

  • the present invention is directed to a process producing large quantities of liquid product via the cryogenic distillation of air.
  • Liquefied atmospheric gases including nitrogen, oxygen and argon
  • Such liquefied atmospheric gases provide cryogenic capabilities for various industrial processes, are more economical to transport in merchant supply and provide ready and economical sources of gaseous product from liquid storage facilities.
  • liquid nitrogen is increasingly used to freeze food products, to cryogenically embrittle used materials for cleaning or recycle, and as a supply of gaseous nitrogen inerting medium for various industrial processes.
  • the conventional process for making large quantities of liquid nitrogen and/or liquid oxygen from an air feed is to include an expander scheme with the conventional multiple column distillation system.
  • the expander scheme provides at least a portion of the large amount of refrigeration that is required to remove a large percentage of the air feed as liquid product vis-a-vis a small percentage of the air feed or no percentage of the air feed as liquid product. (As used herein, a "large percentage" of the air feed is defined as at least 15% of the air feed).
  • This inclusion of an expander scheme with the conventional multiple column distillation system is generally referred to in the industry as a liquefier and that is how the term liquefier is used herein.
  • the expander scheme can be integrated with the front end processing of the air feed or with the recycling of low pressure column nitrogen overhead.
  • Front end processing comprises compressing the air feed to an elevated pressure, removing impurities from the air feed which will freeze out at cryogenic temperatures and cooling the air feed by heat exchange against process streams.
  • the energy efficiency of conventional liquefiers is limited by the low operating pressure of the low pressure column (typically 17-24 psia; 115-165 kPa) in the multiple column distillation system.
  • Air separation processes that do operate at an elevated pressure in the low pressure column ie pressures greater than 25 psia; 170 kPa
  • GB-A-1,450,164 is an example which teaches this latter type of process.
  • the present invention is an improvement to a process producing large quantities of liquid product via the cryogenic distillation of air.
  • the process to which the improvement pertains uses the conventional multiple column distillation system comprising a high pressure column and a low pressure column wherein, subsequent to a front end processing of the air feed, at least a portion of the air feed is fed to the high pressure column.
  • the air feed is rectified into a high pressure nitrogen overhead and a high pressure crude liquid oxygen bottoms.
  • At least a portion of the high pressure crude liquid oxygen bottoms is fed to the low pressure column in which the high pressure crude liquid oxygen bottoms is distilled into a low pressure nitrogen overhead and a low pressure liquid oxygen bottoms.
  • the high pressure column and the low pressure column are thermally linked such that at least a portion of the high pressure nitrogen overhead is condensed in a reboiler/condenser against a vaporizing low pressure column oxygen-rich liquid. At least a portion of the condensed high pressure nitrogen overhead is used to provide reflux for the distillation column system.
  • the operating pressure of the low pressure column in the conventional multiple distillation column system is typically 17-24 psia (115-165 kPa).
  • the process to which the improvement pertains generates an amount of refrigeration sufficient to remove at least 15% of the air feed as a liquid nitrogen product stream and/or a liquid oxygen product stream. At least a portion of this amount of refrigeration is generated by an expander scheme.
  • the improvement of the present invention is to increase the efficiency of the above described process and comprises operating the low pressure column at a pressure between 25 and 50 psia (170 and 350 kPa).
  • the improvement can further comprise expanding a nitrogen enriched gaseous product stream which is withdrawn from the low pressure column.
  • a process for the cryogenic distillation of an air feed using a multiple column distillation system comprising a high pressure column and a low pressure column and generating an amount of refrigeration sufficient to remove at least 15% of the air feed as a liquid nitrogen product stream and/or a liquid oxygen product stream; wherein at least a portion of said amount of refrigeration is generated by an expander scheme; subsequent to a front end processing of the air feed, at least a portion of the air feed is fed to the high pressure column in which the air feed is rectified into a high pressure nitrogen overhead and a high pressure crude liquid oxygen bottoms; at least a portion of the high pressure crude liquid oxygen bottoms is fed to the low pressure column in which the high pressure crude liquid oxygen bottoms is distilled into a low pressure nitrogen overhead and a low pressure liquid oxygen bottoms; the high pressure column and the low pressure column are thermally linked such that at least a portion of the high pressure nitrogen overhead is condensed in a reboiler/condenser against a vaporizing low
  • a second portion of said refrigeration can be generated by withdrawing a nitrogen enriched gaseous product stream from the low pressure column and expanding said stream in an expander.
  • the expander scheme is integrated with the further processing of the portion of the low pressure nitrogen overhead.
  • said further processing comprises compressing said low pressure nitrogen overhead portion to an elevated pressure; cooling the compressed overhead portion nitrogen by heat exchange against one or more process streams to a temperature at or near its dew point; condensing said cooled nitrogen overhead portion in a reboiler/condenser against vaporizing high pressure crude liquid oxygen bottoms; using the condensed low pressure nitrogen overhead as additional reflux for the distillation column system and/or as at least a portion of the liquid nitrogen product stream.
  • a second portion of the low pressure nitrogen overhead is warmed by heat exchange against one or more process streams and subsequently removed as a gaseous nitrogen product stream. Refrigeration can be generated by expanding said second portion of the low pressure nitrogen overhead in an expander prior to said warming thereof.
  • the expander scheme can be integrated with the front end processing of the air feed.
  • the front end processing of the air feed comprises compressing the air feed to an elevated pressure and removing impurities from the air feed which will freeze out at cryogenic temperatures; cooling the air feed by heat exchange against one or more process streams; splitting the air feed into a first split feed stream and a second split feed stream; expanding the first split feed stream in an expander and recycling the expanded first split feed stream to the air feed while providing refrigeration to the air feed by heat exchange; further cooling the second split feed stream by heat exchange against process streams; further splitting the second split feed stream into a third split feed stream and a fourth split feed stream; expanding the third split feed stream in an expander and recycling a portion of the expanded third split feed stream to the air feed while providing refrigeration to the air feed by heat exchange; further cooling the fourth split feed stream by heat exchange against process streams; introducing a portion of the fourth split feed stream into the low pressure column for rectification; and introducing the remaining portion of the fourth split feed stream and the remaining portion of the expanded third split feed stream
  • At least a portion of the low pressure nitrogen overhead can be warmed by heat exchange against one or more process streams and recycled to the process for further processing.
  • a waste stream can be withdrawn from a upper intermediate location of the low pressure column, warmed by heat exchange against one or more process streams and subsequently removed as a gaseous waste product. Refrigeration can be generated by expanding said waste stream in an expander prior to said warming thereof.
  • a portion of the low pressure liquid oxygen bottoms can be removed as the liquid oxygen product stream and/or a portion of said bottoms warmed by heat exchange against one or more process streams and subsequently removed as a gaseous oxygen product.
  • the multiple distillation column system may further comprises an argon column in which an argon containing gaseous side stream removed from a lower intermediate location of the low pressure column is rectified into an argon-rich vapor overhead and an argon-lean bottoms liquid.
  • the argon-lean bottoms liquid is returned to the low pressure column and at least a portion of the argon-rich vapor overhead is condensed in a reboiler/condenser against vaporizing high pressure crude liquid oxygen bottoms.
  • a portion of the condensed argon-rich vapor overhead is removed as a liquid argon product and the remaining portion of thereof is used to provide reflux for the argon column.
  • Figure 1 is representative of a conventional liquefier to which the present invention pertains.
  • Figure 1 is based on the teachings of US-A-4,705,548.
  • an ambient air feed in stream 100 is compressed in compressor 110 and cleaned of impurities which will freeze out at cryogenic temperatures in cleaning bed 310.
  • the resultant stream 201 is combined with an air recycle stream 234 to form stream 103 which is further compressed in compressors 140 and 150 prior to being cooled by heat exchange against warming process streams in heat exchanger 540.
  • a portion of stream 103 is removed as stream 506 and expanded in expander 152.
  • the remaining portion of stream 103 is further cooled by heat exchange against warming process streams in heat exchanger 541 after which a second portion of stream 103 is removed as stream 508 and expanded in expander 153.
  • a portion of expander 153's discharge is removed as stream 124 and warmed by heat exchange against cooling process streams in heat exchanger 542 after which stream 124 is combined with expander 152's discharge and further warmed by heat exchange against cooling process streams in heat exchangers 541 and 540 to form the air recycle stream 234.
  • the remaining portion of expander 153's discharge is fed to the bottom of high pressure column 711 as stream 510.
  • the portion of stream 103 remaining after stream 508 is removed is further cooled by heat exchange against warming process streams in heat exchanger 542 to form stream 105.
  • a portion of stream 105 is fed to an intermediate location of high pressure column 711 as stream 106 while the remaining portion is further cooled by heat exchange against warming process streams in heat exchangers 552 and 551 before being fed to an intermediate location of low pressure column 721 as stream 84.
  • the high pressure column feed streams 106 and 510 are rectified into a high pressure nitrogen overhead in stream 10 and a high pressure crude liquid oxygen bottoms in stream 5.
  • Stream 5 is subcooled by heat exchange against warming process streams in heat exchanger 552, reduced in pressure and subsequently warmed by heat exchange against a liquid oxygen product in heat exchanger 550.
  • a portion of stream 5 is then fed to an intermediate location of low pressure column 721 as stream 910 while the remaining portion is fed to reboiler/condenser 732 at the top of crude argon column 731 as stream 52.
  • An argon containing gaseous side stream 89 is removed from a lower intermediate location of the low pressure column and also fed to crude argon column 731 in which stream 89 is rectified into an argon-rich vapor overhead and an argon-lean bottoms liquid in stream 90 which is returned to the low pressure column.
  • the argon-rich vapor overhead is condensed in reboiler/condenser 732 against the high pressure crude liquid oxygen bottoms in stream 52.
  • a portion of the condensed argon-rich vapor overhead is removed as a liquid argon product in stream 160 while the remaining portion of the condensed argon-rich vapor overhead is used to provide reflux for the crude argon column.
  • the portion of the high pressure crude liquid oxygen bottoms in stream 52 that is vaporized against the argon-rich vapor overhead is fed to the low pressure column in stream 15 while the portion which is not vaporized is fed to the low pressure column in stream 16.
  • the low pressure column feed streams 910, 84, 15 and 16 are distilled into a low pressure nitrogen overhead in stream 130 and a low pressure liquid oxygen bottoms.
  • the high pressure column and the low pressure column are thermally linked such that at least a portion of the high pressure nitrogen overhead in stream 10 is condensed in reboiler/condenser 722 against vaporizing low pressure liquid oxygen bottoms. At least a portion of the condensed high pressure nitrogen overhead is used to provide reflux for the distillation column system.
  • the low pressure nitrogen overhead in stream 130 is combined with a vapor flash stream 85 from flash drum 782 to form stream 131.
  • Stream 131 is warmed by heat exchange against process streams in heat exchangers 551, 552, 542, 541 and 540 to form stream 491.
  • a portion of stream 491 is removed as a gaseous nitrogen product in stream 488 while the remaining portion is compressed in compressor 135 to approximately 120 psia (825 kPa) to form stream 482.
  • Stream 482 is cooled to near its dew point by heat exchange against warming process streams in heat exchangers 540, 541 and 542.
  • the resultant stream 163 is subsequently condensed in reboiler/condenser 723 against vaporizing high pressure crude liquid oxygen bottoms.
  • the resultant stream 7 is expanded across valve 252 and subsequently fed as reflux to the high pressure column.
  • a portion of the low pressure column reflux is removed from the high pressure column in stream 6.
  • Stream 6 is subcooled by heat exchange against warming process streams in heat exchanger 551 and flashed in flash drum 782.
  • a portion of the saturated liquid resulting from this flash is removed as a liquid nitrogen product in stream 250 while the remaining portion is used as reflux for the low pressure column in stream 80.
  • the saturated vapor resulting from this flash in stream 85 is combined with the low pressure nitrogen overhead in stream 130 to form stream 131.
  • a nitrogen enriched waste stream 440 is withdrawn from a upper intermediate location of the low pressure column, warmed by heat exchange against process streams in heat exchangers 551, 552, 542, 541 and 540 and subsequently removed as a gaseous waste product in stream 479.
  • a portion of the low pressure liquid oxygen bottoms is removed in stream 117 and subcooled in heat exchanger 550 before being removed as a liquid oxygen product in stream 70.
  • a portion of the vaporizing low pressure liquid oxygen bottoms is removed in stream 195 and warmed by heat exchange against cooling process streams in heat exchangers 542, 541 and 540 before being removed as a gaseous oxygen product in stream 198.
  • the present invention improves the energy efficiency of the conventional liquefies by elevating the operating pressure of the low pressure column to a pressure between 25 and 50 psia (170-350 kPa).
  • This elevated pressure range increases the energy efficiency of the process by reducing the irreversibility of the conventional liquefier. Irreversibility is commonly called lost work or lost exergy.
  • exergy loss can be reduced by reducing the driving force for mass transfer.
  • the driving force for mass transfer is shown by the distance between the equilibrium curve and the operating lines.
  • the driving force can be reduced by elevating the column operating pressure to move the equilibrium curve closer to the operating lines. This effect is more noticeable in the low pressure column.
  • Exergy loss can be further reduced in the conventional liquefier by reducing the driving force for heat transfer in the front end heat exchanger(s).
  • the driving force for heat transfer is shown by the distance between the line for the cooling stream and the line for the warming stream. Elevating the pressure of the low pressure column in turn allows elevation of the expander scheme discharge pressure. For a typical inlet pressure of 600 psia (4.1 MPa), elevating the expander scheme discharge pressure can adjust the shape of the cooling curves to allow a smaller average heat transfer driving force.
  • An elevated pressure in the low pressure column also increases the density of the process gas streams, particularly the low pressure streams.
  • Equipment sizes can be reduced for capital savings due to the lower volumetric gas flows.
  • the upper limit of the present invention's pressure range accounts for the fact that, as the pressure is continually elevated, the benefits of reduced irreversibility are eventually offset by the prohibitive number of additional trays that are required in the distillation system.
  • the present invention's elevated pressure range represents an optimum trade off between reducing the irreversibility of the process at the expense of increasing the capital requirements of the process.
  • Figure 2 is an embodiment of the present invention as applied to the flowsheet depicted in Figure 1.
  • Figure 2 is identical to Figure 1 (similar features of Figure 2 utilize common numbering with Figure 1) except that Figure 2 incorporates a pressure reduction scheme for the gaseous and liquid nitrogen product streams.
  • This pressure reduction scheme equates the nitrogen product stream pressures obtained in the elevated pressure liquefier of Figure 2 with the nitrogen product streams obtained in the conventional liquefier of Figure 1. (This equating is necessary before performing an efficiency comparison between Figures 1 and 2 as is done in the Example infra).
  • the pressure reduction scheme comprises combining a portion of the low pressure nitrogen overhead 432 with waste stream 440 to form a combined gaseous nitrogen product stream 940 which is subsequently reduced in pressure across valve 254 to form stream 941.
  • the pressure reduction scheme further comprises re-flashing the initial liquid nitrogen product stream 351 obtained from flash drum 782 in a second flash drum 783 to obtain the final liquid nitrogen product stream 250.
  • the vapor stream 86 from this second flash step is combined with stream 941. This combined stream is then warmed by heat exchange against process streams and removed as combined gaseous nitrogen product stream 479.
  • a preferred embodiment of the present invention which further increases the efficiency of the conventional liquefier comprises expanding a nitrogen enriched gaseous product stream which is withdrawn from the low pressure column.
  • This preferred embodiment exploits the fact that such a product stream will be at an elevated pressure visa-vis the conventional liquefier and thus can be expanded to generate refrigeration.
  • Figure 3 illustrates this preferred embodiment of the present invention as applied to the flowsheet depicted in Figure 2.
  • Figure 3 is identical to Figure 2 (similar features of Figure 3 utilize common numbering with Figure 2) except that expander 154 is substituted for pressure reduction valve 254.
  • stream 940 may first be partially warmed in one or more of the process heat exchangers prior to being expanded in expander 154.
  • the present invention is not only applicable to the air recycle liquefiers as described in US-A-4,152,130; US-A-4,705,548; and US-A-4,715,873 but also to any air recycle liquefier derived from these patents. It is also applicable to any nitrogen recycle liquefier such as those described in US-A-3,605,422 and US-A-4,894,076.
  • the purpose of this example is to demonstrate the improved energy efficiency of present invention. This was accomplished by performing computer simulations for the liquefiers depicted in the flowsheets of Figures 1, 2 and 3.
  • the pressure at the top of the low pressure column is set at a conventional pressure of 18.1 psia (125 kPa).
  • this pressure is elevated to a pressure within the range of the present invention, namely 27.8 psia (191.5 kPa) for the Figure 2 simulation and 25.9 psia (178.5 kPa) for Figure 3's preferred embodiment simulation.
  • Table 4 compares the power consumption in the simulations of Figures 1, 2 and 3. This comparison shows that the present invention achieved a 1.0% efficiency improvement when applied to Figure 1's conventional liquefier while a preferred embodiment of the present invention achieved a 2.1% efficiency improvement when applied to Figure 1's conventional liquefier.
  • Figure 1 would incur an additional compression requirement for compressing stream 488 from 15.2 psia (105 kPa) to 25.2 psia (174 kPa) while Figure 2 would incur an additional compression requirement only for compressing stream 86 (a mere 1.1% of the air feed) from 18.6 psia (128 kPa) to 27.8 psia (191.5 kPa).
  • streams 432 and 86 totalling 39.1% of the air feed would not be combined with waste stream 440 as is currently shown in Figure 2.
  • stream 432 would remain a part of stream 130 and, after compressing stream 86 from 18.6 psia (128 kPa) to 27.8 psia (191.5 kPa), streams 86 would be combined with stream 130.
  • the total amount of flow previously contained in streams 432 and 86 [ie 39.1% of the air feed] would then be removed as the high purity gaseous nitrogen product in stream 488 at a pressure of 25.2 psia (174 kPa). This much larger additional compression requirement for Figure 1 would increase Figure 2's efficiency improvement over Figure 1 from the above 1.0% to approximately 2.9%.
  • the present invention is an effective method for increasing the energy efficiency of a conventional liquefier.

Abstract

The energy efficiency of dual cryogenic distillation of air to produce liquid product in which refrigeration is generated by an expander scheme is improved by operating the low pressure distillation column (721) at an elevated pressure (170 to 350 kPa) vis-a-vis the prior art.

Description

  • The present invention is directed to a process producing large quantities of liquid product via the cryogenic distillation of air.
  • Liquefied atmospheric gases, including nitrogen, oxygen and argon, are finding increasing uses in industry. Such liquefied atmospheric gases provide cryogenic capabilities for various industrial processes, are more economical to transport in merchant supply and provide ready and economical sources of gaseous product from liquid storage facilities. For instance, liquid nitrogen is increasingly used to freeze food products, to cryogenically embrittle used materials for cleaning or recycle, and as a supply of gaseous nitrogen inerting medium for various industrial processes.
  • The conventional process for making large quantities of liquid nitrogen and/or liquid oxygen from an air feed is to include an expander scheme with the conventional multiple column distillation system. The expander scheme provides at least a portion of the large amount of refrigeration that is required to remove a large percentage of the air feed as liquid product vis-a-vis a small percentage of the air feed or no percentage of the air feed as liquid product. (As used herein, a "large percentage" of the air feed is defined as at least 15% of the air feed). This inclusion of an expander scheme with the conventional multiple column distillation system is generally referred to in the industry as a liquefier and that is how the term liquefier is used herein.
  • The expander scheme can be integrated with the front end processing of the air feed or with the recycling of low pressure column nitrogen overhead. Front end processing comprises compressing the air feed to an elevated pressure, removing impurities from the air feed which will freeze out at cryogenic temperatures and cooling the air feed by heat exchange against process streams. US-A-4,152,130; US-A-4,705,548; and US-A-4,715,873 for example, teach liquefiers wherein the expander scheme is integrated with the front end processing of the feed air while US-A-3,605,422 and US-A-4,894,076 teach liquefiers wherein the expander scheme is integrated with the recycling of the low pressure column nitrogen overhead.
  • The energy efficiency of conventional liquefiers is limited by the low operating pressure of the low pressure column (typically 17-24 psia; 115-165 kPa) in the multiple column distillation system. Air separation processes that do operate at an elevated pressure in the low pressure column (ie pressures greater than 25 psia; 170 kPa) have traditionally been restricted to gaseous product processes or small liquid making processes. GB-A-1,450,164 is an example which teaches this latter type of process.
  • It is an object of the present invention to improve the energy efficiency of the conventional liquefier.
  • The present invention is an improvement to a process producing large quantities of liquid product via the cryogenic distillation of air. The process to which the improvement pertains uses the conventional multiple column distillation system comprising a high pressure column and a low pressure column wherein, subsequent to a front end processing of the air feed, at least a portion of the air feed is fed to the high pressure column. In the high pressure column, the air feed is rectified into a high pressure nitrogen overhead and a high pressure crude liquid oxygen bottoms. At least a portion of the high pressure crude liquid oxygen bottoms is fed to the low pressure column in which the high pressure crude liquid oxygen bottoms is distilled into a low pressure nitrogen overhead and a low pressure liquid oxygen bottoms. The high pressure column and the low pressure column are thermally linked such that at least a portion of the high pressure nitrogen overhead is condensed in a reboiler/condenser against a vaporizing low pressure column oxygen-rich liquid. At least a portion of the condensed high pressure nitrogen overhead is used to provide reflux for the distillation column system. The operating pressure of the low pressure column in the conventional multiple distillation column system is typically 17-24 psia (115-165 kPa).
  • Along with the above described conventional multiple column distillation system, the process to which the improvement pertains generates an amount of refrigeration sufficient to remove at least 15% of the air feed as a liquid nitrogen product stream and/or a liquid oxygen product stream. At least a portion of this amount of refrigeration is generated by an expander scheme.
  • The improvement of the present invention is to increase the efficiency of the above described process and comprises operating the low pressure column at a pressure between 25 and 50 psia (170 and 350 kPa). In order to further increase the efficiency of the process, the improvement can further comprise expanding a nitrogen enriched gaseous product stream which is withdrawn from the low pressure column.
  • According to a the present invention, there is provided a process for the cryogenic distillation of an air feed using a multiple column distillation system comprising a high pressure column and a low pressure column and generating an amount of refrigeration sufficient to remove at least 15% of the air feed as a liquid nitrogen product stream and/or a liquid oxygen product stream; wherein at least a portion of said amount of refrigeration is generated by an expander scheme; subsequent to a front end processing of the air feed, at least a portion of the air feed is fed to the high pressure column in which the air feed is rectified into a high pressure nitrogen overhead and a high pressure crude liquid oxygen bottoms; at least a portion of the high pressure crude liquid oxygen bottoms is fed to the low pressure column in which the high pressure crude liquid oxygen bottoms is distilled into a low pressure nitrogen overhead and a low pressure liquid oxygen bottoms; the high pressure column and the low pressure column are thermally linked such that at least a portion of the high pressure nitrogen overhead is condensed in a reboiler/condenser against a vaporizing low pressure column oxygen-rich liquid; and at least a portion of the condensed high pressure nitrogen overhead is used to provide reflux for the distillation column system; characterized in that the low pressure column is operated at a pressure between 170 and 350 kPa (25 and 50 psia).
  • Desirably, a second portion of said refrigeration can be generated by withdrawing a nitrogen enriched gaseous product stream from the low pressure column and expanding said stream in an expander.
  • Suitably, the expander scheme is integrated with the further processing of the portion of the low pressure nitrogen overhead. In one preferred embodiment, said further processing comprises compressing said low pressure nitrogen overhead portion to an elevated pressure; cooling the compressed overhead portion nitrogen by heat exchange against one or more process streams to a temperature at or near its dew point; condensing said cooled nitrogen overhead portion in a reboiler/condenser against vaporizing high pressure crude liquid oxygen bottoms; using the condensed low pressure nitrogen overhead as additional reflux for the distillation column system and/or as at least a portion of the liquid nitrogen product stream. Advantageously, a second portion of the low pressure nitrogen overhead is warmed by heat exchange against one or more process streams and subsequently removed as a gaseous nitrogen product stream. Refrigeration can be generated by expanding said second portion of the low pressure nitrogen overhead in an expander prior to said warming thereof.
  • The expander scheme can be integrated with the front end processing of the air feed. Preferably, the front end processing of the air feed comprises compressing the air feed to an elevated pressure and removing impurities from the air feed which will freeze out at cryogenic temperatures; cooling the air feed by heat exchange against one or more process streams; splitting the air feed into a first split feed stream and a second split feed stream; expanding the first split feed stream in an expander and recycling the expanded first split feed stream to the air feed while providing refrigeration to the air feed by heat exchange; further cooling the second split feed stream by heat exchange against process streams; further splitting the second split feed stream into a third split feed stream and a fourth split feed stream; expanding the third split feed stream in an expander and recycling a portion of the expanded third split feed stream to the air feed while providing refrigeration to the air feed by heat exchange; further cooling the fourth split feed stream by heat exchange against process streams; introducing a portion of the fourth split feed stream into the low pressure column for rectification; and introducing the remaining portion of the fourth split feed stream and the remaining portion of the expanded third split feed stream into the high pressure column for rectification.
  • At least a portion of the low pressure nitrogen overhead can be warmed by heat exchange against one or more process streams and recycled to the process for further processing.
  • A waste stream can be withdrawn from a upper intermediate location of the low pressure column, warmed by heat exchange against one or more process streams and subsequently removed as a gaseous waste product. Refrigeration can be generated by expanding said waste stream in an expander prior to said warming thereof.
  • A portion of the low pressure liquid oxygen bottoms can be removed as the liquid oxygen product stream and/or a portion of said bottoms warmed by heat exchange against one or more process streams and subsequently removed as a gaseous oxygen product.
  • The multiple distillation column system may further comprises an argon column in which an argon containing gaseous side stream removed from a lower intermediate location of the low pressure column is rectified into an argon-rich vapor overhead and an argon-lean bottoms liquid. The argon-lean bottoms liquid is returned to the low pressure column and at least a portion of the argon-rich vapor overhead is condensed in a reboiler/condenser against vaporizing high pressure crude liquid oxygen bottoms. A portion of the condensed argon-rich vapor overhead is removed as a liquid argon product and the remaining portion of thereof is used to provide reflux for the argon column.
    In the drawings:-
    • Figure 1 is a schematic diagram of a conventional process producing large quantities of liquid product via the cryogenic distillation of air;
    • Figure 2 is a schematic diagram of one embodiment of the process of the present invention; and
    • Figure 3 is a schematic diagram of a preferred embodiment of the process of the present invention.
  • Figure 1 is representative of a conventional liquefier to which the present invention pertains. Figure 1 is based on the teachings of US-A-4,705,548. Referring now to Figure 1, an ambient air feed in stream 100 is compressed in compressor 110 and cleaned of impurities which will freeze out at cryogenic temperatures in cleaning bed 310. The resultant stream 201 is combined with an air recycle stream 234 to form stream 103 which is further compressed in compressors 140 and 150 prior to being cooled by heat exchange against warming process streams in heat exchanger 540. A portion of stream 103 is removed as stream 506 and expanded in expander 152. The remaining portion of stream 103 is further cooled by heat exchange against warming process streams in heat exchanger 541 after which a second portion of stream 103 is removed as stream 508 and expanded in expander 153. A portion of expander 153's discharge is removed as stream 124 and warmed by heat exchange against cooling process streams in heat exchanger 542 after which stream 124 is combined with expander 152's discharge and further warmed by heat exchange against cooling process streams in heat exchangers 541 and 540 to form the air recycle stream 234. The remaining portion of expander 153's discharge is fed to the bottom of high pressure column 711 as stream 510. The portion of stream 103 remaining after stream 508 is removed is further cooled by heat exchange against warming process streams in heat exchanger 542 to form stream 105. A portion of stream 105 is fed to an intermediate location of high pressure column 711 as stream 106 while the remaining portion is further cooled by heat exchange against warming process streams in heat exchangers 552 and 551 before being fed to an intermediate location of low pressure column 721 as stream 84.
  • The high pressure column feed streams 106 and 510 are rectified into a high pressure nitrogen overhead in stream 10 and a high pressure crude liquid oxygen bottoms in stream 5. Stream 5 is subcooled by heat exchange against warming process streams in heat exchanger 552, reduced in pressure and subsequently warmed by heat exchange against a liquid oxygen product in heat exchanger 550. A portion of stream 5 is then fed to an intermediate location of low pressure column 721 as stream 910 while the remaining portion is fed to reboiler/condenser 732 at the top of crude argon column 731 as stream 52.
  • An argon containing gaseous side stream 89 is removed from a lower intermediate location of the low pressure column and also fed to crude argon column 731 in which stream 89 is rectified into an argon-rich vapor overhead and an argon-lean bottoms liquid in stream 90 which is returned to the low pressure column. The argon-rich vapor overhead is condensed in reboiler/condenser 732 against the high pressure crude liquid oxygen bottoms in stream 52. A portion of the condensed argon-rich vapor overhead is removed as a liquid argon product in stream 160 while the remaining portion of the condensed argon-rich vapor overhead is used to provide reflux for the crude argon column. The portion of the high pressure crude liquid oxygen bottoms in stream 52 that is vaporized against the argon-rich vapor overhead is fed to the low pressure column in stream 15 while the portion which is not vaporized is fed to the low pressure column in stream 16.
  • The low pressure column feed streams 910, 84, 15 and 16 are distilled into a low pressure nitrogen overhead in stream 130 and a low pressure liquid oxygen bottoms. The high pressure column and the low pressure column are thermally linked such that at least a portion of the high pressure nitrogen overhead in stream 10 is condensed in reboiler/condenser 722 against vaporizing low pressure liquid oxygen bottoms. At least a portion of the condensed high pressure nitrogen overhead is used to provide reflux for the distillation column system.
  • The low pressure nitrogen overhead in stream 130 is combined with a vapor flash stream 85 from flash drum 782 to form stream 131. Stream 131 is warmed by heat exchange against process streams in heat exchangers 551, 552, 542, 541 and 540 to form stream 491. A portion of stream 491 is removed as a gaseous nitrogen product in stream 488 while the remaining portion is compressed in compressor 135 to approximately 120 psia (825 kPa) to form stream 482. Stream 482 is cooled to near its dew point by heat exchange against warming process streams in heat exchangers 540, 541 and 542. The resultant stream 163 is subsequently condensed in reboiler/condenser 723 against vaporizing high pressure crude liquid oxygen bottoms. The resultant stream 7 is expanded across valve 252 and subsequently fed as reflux to the high pressure column. A portion of the low pressure column reflux is removed from the high pressure column in stream 6. Stream 6 is subcooled by heat exchange against warming process streams in heat exchanger 551 and flashed in flash drum 782. A portion of the saturated liquid resulting from this flash is removed as a liquid nitrogen product in stream 250 while the remaining portion is used as reflux for the low pressure column in stream 80. The saturated vapor resulting from this flash in stream 85 is combined with the low pressure nitrogen overhead in stream 130 to form stream 131.
  • A nitrogen enriched waste stream 440 is withdrawn from a upper intermediate location of the low pressure column, warmed by heat exchange against process streams in heat exchangers 551, 552, 542, 541 and 540 and subsequently removed as a gaseous waste product in stream 479. A portion of the low pressure liquid oxygen bottoms is removed in stream 117 and subcooled in heat exchanger 550 before being removed as a liquid oxygen product in stream 70. A portion of the vaporizing low pressure liquid oxygen bottoms is removed in stream 195 and warmed by heat exchange against cooling process streams in heat exchangers 542, 541 and 540 before being removed as a gaseous oxygen product in stream 198.
  • The present invention improves the energy efficiency of the conventional liquefies by elevating the operating pressure of the low pressure column to a pressure between 25 and 50 psia (170-350 kPa). This elevated pressure range increases the energy efficiency of the process by reducing the irreversibility of the conventional liquefier. Irreversibility is commonly called lost work or lost exergy. In the distillation system, exergy loss can be reduced by reducing the driving force for mass transfer. On an x-y equilibrium diagram, the driving force for mass transfer is shown by the distance between the equilibrium curve and the operating lines. At the same liquid to vapor flow ratios in the distillation column, the driving force can be reduced by elevating the column operating pressure to move the equilibrium curve closer to the operating lines. This effect is more noticeable in the low pressure column.
  • Exergy loss can be further reduced in the conventional liquefier by reducing the driving force for heat transfer in the front end heat exchanger(s). On a plot of temperature versus enthalpy change, the driving force for heat transfer is shown by the distance between the line for the cooling stream and the line for the warming stream. Elevating the pressure of the low pressure column in turn allows elevation of the expander scheme discharge pressure. For a typical inlet pressure of 600 psia (4.1 MPa), elevating the expander scheme discharge pressure can adjust the shape of the cooling curves to allow a smaller average heat transfer driving force.
  • An elevated pressure in the low pressure column also increases the density of the process gas streams, particularly the low pressure streams. Equipment sizes can be reduced for capital savings due to the lower volumetric gas flows.
  • The upper limit of the present invention's pressure range accounts for the fact that, as the pressure is continually elevated, the benefits of reduced irreversibility are eventually offset by the prohibitive number of additional trays that are required in the distillation system. In effect, the present invention's elevated pressure range represents an optimum trade off between reducing the irreversibility of the process at the expense of increasing the capital requirements of the process.
  • Figure 2 is an embodiment of the present invention as applied to the flowsheet depicted in Figure 1. Figure 2 is identical to Figure 1 (similar features of Figure 2 utilize common numbering with Figure 1) except that Figure 2 incorporates a pressure reduction scheme for the gaseous and liquid nitrogen product streams. This pressure reduction scheme equates the nitrogen product stream pressures obtained in the elevated pressure liquefier of Figure 2 with the nitrogen product streams obtained in the conventional liquefier of Figure 1. (This equating is necessary before performing an efficiency comparison between Figures 1 and 2 as is done in the Example infra). Referring to Figure 2, the pressure reduction scheme comprises combining a portion of the low pressure nitrogen overhead 432 with waste stream 440 to form a combined gaseous nitrogen product stream 940 which is subsequently reduced in pressure across valve 254 to form stream 941. The pressure reduction scheme further comprises re-flashing the initial liquid nitrogen product stream 351 obtained from flash drum 782 in a second flash drum 783 to obtain the final liquid nitrogen product stream 250. The vapor stream 86 from this second flash step is combined with stream 941. This combined stream is then warmed by heat exchange against process streams and removed as combined gaseous nitrogen product stream 479.
  • A preferred embodiment of the present invention which further increases the efficiency of the conventional liquefier comprises expanding a nitrogen enriched gaseous product stream which is withdrawn from the low pressure column. This preferred embodiment exploits the fact that such a product stream will be at an elevated pressure visa-vis the conventional liquefier and thus can be expanded to generate refrigeration. Figure 3 illustrates this preferred embodiment of the present invention as applied to the flowsheet depicted in Figure 2. Figure 3 is identical to Figure 2 (similar features of Figure 3 utilize common numbering with Figure 2) except that expander 154 is substituted for pressure reduction valve 254. Although not shown in Figure 3, stream 940 may first be partially warmed in one or more of the process heat exchangers prior to being expanded in expander 154.
  • The present invention is not only applicable to the air recycle liquefiers as described in US-A-4,152,130; US-A-4,705,548; and US-A-4,715,873 but also to any air recycle liquefier derived from these patents. It is also applicable to any nitrogen recycle liquefier such as those described in US-A-3,605,422 and US-A-4,894,076.
  • In order to demonstrate the efficacy of the present invention, the following example is offered.
    • EXAMPLE
  • The purpose of this example is to demonstrate the improved energy efficiency of present invention. This was accomplished by performing computer simulations for the liquefiers depicted in the flowsheets of Figures 1, 2 and 3. In the simulation of Figure 1, the pressure at the top of the low pressure column is set at a conventional pressure of 18.1 psia (125 kPa). In the simulations of Figures 2 and 3, this pressure is elevated to a pressure within the range of the present invention, namely 27.8 psia (191.5 kPa) for the Figure 2 simulation and 25.9 psia (178.5 kPa) for Figure 3's preferred embodiment simulation. In each simulation, the percentage of the air feed that is recovered as liquid nitrogen (27.1%), liquid oxygen (20.5%), liquid argon (0.9%), and gaseous nitrogen (51.0%) is kept constant. Operating conditions for these and other key streams in the simulations of Figures 1, 2 and 3 are included in the following Tables 1, 2 and 3 respectively. Table 1
    Steam Number Pressure psia (kPa) Temp. °F (°C) Flow (% of air feed) Composition (mole%)
    N₂ Ar O₂
    70 21.9 (151) -300 (-184.5) 20.5 0.00 0.19 99.81
    100 14.7 (101.5) 80 (26.5) 100.0 78.12 0.93 20.95
    103 80.5 (555) 78 (25.5) 306.0 78.12 0.93 20.95
    105 760.0 (5240) -278 (-172) 58.5 78.12 0.93 20.95
    124 85.0 (586) -279 (-173) 139.0 78.12 0.93 20.95
    130 18.1 (125) -317 (-194) 69.8 100.00 0.00 0.00
    160 15.9 (109.5) -301 (-185) 0.9 0.11 99.39 0.50
    163 120.0 (827.5) -278 (-172) 37.5 100.00 0.00 0.00
    195 21.9 (151) -290 (-179) 0.0 0.00 0.09 99.91
    198 19.9 (137) 78 (25.5) 0.0 0.00 0.09 99.91
    201 81.0 (559) 78 (25.5) 100.0 78.12 0.93 20.95
    234 81.0 (559) 78 (25.5) 206.0 78.12 0.93 20.95
    250 18.1 (125) -317 (-194) 27.1 100.00 0.00 0.00
    440 18.9 (130.5) -316 (-193.5) 11.9 99.86 0.12 0.02
    479 17.0 (117) 78 (25.5) 11.9 99.86 0.12 0.02
    488 15.2 (105) 78 (25.5) 39.1 100.00 0.00 0.00
    506 764.0 (5268) 50 (10) 67.0 78.12 0.93 20.95
    508 762.0 (5254) -137 (-94) 180.5 78.12 0.93 20.95
    510 85.0 (586) -279 (-173) 41.5 78.12 0.93 20.95
    Table 2
    Steam Number Pressure psia (kPa) Temp. °F (°C) Flow (% of air feed) Composition (mole %)
    N₂ Ar O₂
    70 31.9 (220) -298 (-183.5) 20.5 0.00 0.19 99.81
    86 18.6 (128) - 317 (-194) 1.1 100.00 0.00 0.00
    100 14.7 (101.5) 80 (26.5) 100.0 78.12 0.93 20.95
    103 109.3 (753.5) 78 (25.5) 319.1 78.12 0.93 20.95
    105 760.0 (5240) -270 (-168) 58.9 78.12 0.93 20.95
    124 113.8 (784.5) -271 (-168.5) 142.4 78.12 0.93 20.95
    130 27.8 (191.5) -310 (-190) 74.7 100.00 0.00 0.00
    160 25.9 (178.5) -292 (-180) 0.9 0.11 99.39 0.5
    163 162.6 (1121) -270 (-168) 45.0 100.00 0.00 0.00
    195 31.9 (220) -283 (-175) 0.0 0.00 0.09 99.91
    198 29.9 (206) 78 (25.5) 0.0 0.00 0.09 99.91
    201 109.8 (757) 78 (25.5) 100.00 78.12 0.93 20.95
    234 109.8 (757) 78 (25.5) 219.1 78.12 0.93 20.95
    250 18.6 (128) -317 (-194) 27.1 100.00 0.00 0.00
    432 27.8 (191.5) -310 (-190) 38.0 100.00 0.00 0.00
    440 28.9 (199.5) -309 (-189.5) 11.9 99.76 0.19 0.05
    479 17.0 (117) 78 (25.5) 51.0 99.94 0.05 0.01
    488 25.2 (176) 78 (25.5) 0.0 100.00 0.00 0.00
    506 764.0 (5268) 50 (10) 76.7 78.12 0.93 20.95
    508 762.0 (5254) -140 (-95.5) 183.5 78.12 0.93 20.95
    510 113.8 (784.5) -271 (-168.5) 41.1 78.12 0.93 20.95
    940 27.8 (191.5) -310 (-190) 49.9 99.94 0.05 0.01
    941 18.7 (129) -313 (-191.5) 49.9 99.94 0.05 0.01
    Table 3
    Steam Number Pressure psia (kPa) Temp. °F (°C) Flow (% of air feed) Composition (mole %)
    N₂ Ar O₂
    70 31.8 (219.5) -298.5 (-183.5) 20.5 0.00 0.19 99.81
    100 14.7 (101.5) 80 (26.5) 100.0 78.12 0.93 20.95
    103 109.1 (752) 78 (25.5) 312.9 78.12 0.93 20.95
    105 760.0 (5240) -270 (-128) 57.0 78.12 0.93 20.95
    124 113.6 (783.5) -272 (-169) 136.9 78.12 0.93 20.95
    130 25.9 (178.5) -311 (-190.5) 74.9 100.00 0.00 0.00
    160 23.7 (163.5) -294 (-181) 0.9 0.11 99.39 0.5
    163 164.0 (1131) -269 (-167) 45.0 100.00 0.00 0.00
    195 31.8 (219.5) -283 (-175) 0.0 0.00 0.09 99.91
    198 29.8 (205.5) 78 (25.5) 0.0 0.00 0.09 99.91
    201 109.6 (755.5) 78 (25.5) 100.0 78.12 0.93 20.95
    234 109.6 (755.5) 78 (25.5) 212.9 78.12 0.93 20.95
    250 18.6 (128) -317 (-194) 27.1 100.00 0.00 0.00
    432 25.9 (178.5) -311 (190.5) 38.2 100.00 0.00 0.00
    440 26.7 (184) -311 (-190.5) 11.9 99.86 0.11 0.03
    479 17.0 (117) 78 (25.5) 51.0 99.96 0.03 0.01
    488 23.0 (158.5) 78 (25.5) 0.0 100.00 0.00 0.00
    506 764.0 (5268) 50 (10) 76.1 78.12 0.93 20.95
    508 762.0 (5254) -140 (-95.5) 179.9 78.12 0.93 20.95
    510 113.6 (783.5) -272 (-169) 43.0 78.12 0.93 20.95
    940 25.9 (178.5) -311 (-190.5) 50.1 99.96 0.03 0.01
    941 18.7 (129) -317 (-194) 50.1 99.96 0.03 0.01
  • The following Table 4 compares the power consumption in the simulations of Figures 1, 2 and 3. This comparison shows that the present invention achieved a 1.0% efficiency improvement when applied to Figure 1's conventional liquefier while a preferred embodiment of the present invention achieved a 2.1% efficiency improvement when applied to Figure 1's conventional liquefier. Table 4
    Simulation Power
    Figure 1 1.000
    Figure 2 0.990
    Figure 3 0.979
  • It is important to note that the efficiency improvement of the present invention will be significantly more pronounced where the product streams are required at an elevated pressure. Assume, for example, that the 39.1 % of the air feed which is removed as the high purity gaseous nitrogen product in stream 488 in Figure 1 is required at Figure 2's elevated low pressure column pressure of 27.8 psia (191.5 kPa) less 2.6 psia (18 kPa) to account for the pressure drop across the heat exchangers. In this scenario, Figure 1 would incur an additional compression requirement for compressing stream 488 from 15.2 psia (105 kPa) to 25.2 psia (174 kPa) while Figure 2 would incur an additional compression requirement only for compressing stream 86 (a mere 1.1% of the air feed) from 18.6 psia (128 kPa) to 27.8 psia (191.5 kPa). (Also in this scenario for Figure 2, streams 432 and 86 totalling 39.1% of the air feed would not be combined with waste stream 440 as is currently shown in Figure 2. Instead, stream 432 would remain a part of stream 130 and, after compressing stream 86 from 18.6 psia (128 kPa) to 27.8 psia (191.5 kPa), streams 86 would be combined with stream 130. After being warmed in the heat exchangers and undergoing a 2.6 psia (18 kPa) pressure drop, the total amount of flow previously contained in streams 432 and 86 [ie 39.1% of the air feed] would then be removed as the high purity gaseous nitrogen product in stream 488 at a pressure of 25.2 psia (174 kPa). This much larger additional compression requirement for Figure 1 would increase Figure 2's efficiency improvement over Figure 1 from the above 1.0% to approximately 2.9%.
  • In summary, the present invention is an effective method for increasing the energy efficiency of a conventional liquefier.

Claims (13)

  1. A process for the cryogenic distillation of an air feed using a multiple column distillation system comprising a high pressure column and a low pressure column and generating an amount of refrigeration sufficient to remove at least 15% of the air feed as a liquid nitrogen product stream and/or a liquid oxygen product stream; wherein at least a portion of said amount of refrigeration is generated by an expander scheme; subsequent to a front end processing of the air feed, at least a portion of the air feed is fed to the high pressure column in which the air feed is rectified into a high pressure nitrogen overhead and a high pressure crude liquid oxygen bottoms; at least a portion of the high pressure crude liquid oxygen bottoms is fed to the low pressure column in which the high pressure crude liquid oxygen bottoms is distilled into a low pressure nitrogen overhead and a low pressure liquid oxygen bottoms; the high pressure column and the low pressure column are thermally linked such that at least a portion of the high pressure nitrogen overhead is condensed in a reboiler/condenser against a vaporizing low pressure column oxygen-rich liquid; and at least a portion of the condensed high pressure nitrogen overhead is used to provide reflux for the distillation column system; characterized in that the low pressure column is operated at a pressure between 170 and 350 kPa (25 and 50 psia).
  2. A process as claimed in Claim 1, wherein a nitrogen enriched gaseous product stream is withdrawn from the low . pressure column and refrigeration is generated by expanding the nitrogen enriched gaseous product stream in an expander.
  3. A process as claimed in Claim 1 or Claim 2, wherein at least a portion of the low pressure nitrogen overhead is warmed by heat exchange against one or more process streams and recycled to the process for further processing.
  4. A process as claimed in Claim 3, wherein the expander scheme is integrated with the further processing of the portion of the low pressure nitrogen overhead.
  5. A process as claimed in Claim 4, wherein said further processing comprises:
    (a) compressing said low pressure nitrogen overhead portion to an elevated pressure;
    (b) cooling the compressed overhead portion nitrogen by heat exchange against one or more process streams to a temperature at or near its dew point;
    (c) condensing said cooled nitrogen overhead portion in a reboiler/condenser against vaporizing high pressure crude liquid oxygen bottoms;
    (d) using the condensed low pressure nitrogen overhead as additional reflux for the distillation column system and/or as at least a portion of the liquid nitrogen product stream.
  6. A process as claimed in Claim 5, wherein a second portion of the low pressure nitrogen overhead is warmed by heat exchange against one or more process streams and subsequently removed as a gaseous nitrogen product stream.
  7. A process as claimed in any one of the preceding claims, wherein a waste stream is withdrawn from a upper intermediate location of the low pressure column, warmed by heat exchange against one or more process streams and subsequently removed as a gaseous waste product.
  8. A process as claimed in Claim 6 or Claim 7, wherein refrigeration is generated by expanding said waste stream in an expander prior to said warming thereof and/or by expanding said second portion of the low pressure nitrogen overhead in an expander prior to said warming thereof.
  9. A process as claimed in any one of the preceding claims, wherein the expander scheme is integrated with the front end processing of the air feed.
  10. A process as claimed in Claim 9, wherein the front end processing of the air feed comprises:
    (a) compressing the air feed to an elevated pressure and removing impurities from the air feed which will freeze out at cryogenic temperatures;
    (b) cooling the air feed by heat exchange against one or more process streams;
    (c) splitting the air feed into a first split feed stream and a second split feed stream;
    (d) expanding the first split feed stream in an expander and recycling the expanded first split feed stream to the air feed while providing refrigeration to the air feed by heat exchange;
    (e) further cooling the second split feed stream by heat exchange against process streams;
    (f) further splitting the second split feed stream into a third split feed stream and a fourth split feed stream;
    (g) expanding the third split feed stream in an expander and recycling a portion of the expanded third split feed stream to the air feed while providing refrigeration to the air feed by heat exchange;
    (h) further cooling the fourth split feed stream by heat exchange against process streams;
    (i) introducing a portion of the fourth split feed stream into the low pressure column for rectification; and
    (j) introducing the remaining portion of the fourth split feed stream and the remaining portion of the expanded third split feed stream into the high pressure column for rectification.
  11. A process as claimed in any one of the preceding claims, wherein a portion of the low pressure liquid oxygen bottoms is removed as the liquid oxygen product stream.
  12. A process as claimed in any one of the preceding claims, wherein a portion of the low pressure liquid oxygen bottoms is warmed by heat exchange against one or more process streams and subsequently removed as a gaseous oxygen product.
  13. A process as claimed in any one of the preceding claims, wherein:
    (a) the multiple distillation column system further comprises an argon column;
    (b) an argon containing gaseous side stream is removed from a lower intermediate location of the low pressure column and fed to the argon column in which the argon containing gaseous side stream is rectified into an argon-rich vapor overhead and an argon-lean bottoms liquid;
    (c) the argon-lean bottoms liquid is returned to the low pressure column;
    (d) at least a portion of the argon-rich vapor overhead is condensed in a reboiler/condenser against vaporizing high pressure crude liquid oxygen bottoms;
    (e) a portion of the condensed argon-rich vapor overhead is removed as a liquid argon product; and
    (f) the remaining portion of the condensed argon-rich vapor overhead is used to provide reflux for the argon column.
EP93305480A 1992-07-20 1993-07-13 Elevated pressure liquefier Expired - Lifetime EP0580345B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US91656592A 1992-07-20 1992-07-20
US916565 1992-07-20

Publications (2)

Publication Number Publication Date
EP0580345A1 true EP0580345A1 (en) 1994-01-26
EP0580345B1 EP0580345B1 (en) 1996-02-14

Family

ID=25437475

Family Applications (1)

Application Number Title Priority Date Filing Date
EP93305480A Expired - Lifetime EP0580345B1 (en) 1992-07-20 1993-07-13 Elevated pressure liquefier

Country Status (6)

Country Link
EP (1) EP0580345B1 (en)
JP (1) JPH06159929A (en)
KR (1) KR940002589A (en)
CA (1) CA2100402A1 (en)
DE (1) DE69301555T2 (en)
ES (1) ES2085116T3 (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0684437A1 (en) * 1994-05-27 1995-11-29 The BOC Group plc Air separation
FR2830928A1 (en) * 2001-10-17 2003-04-18 Air Liquide Separation of air by cryogenic distillation with heat exchange cooling the compressed and purified inlet air before it is introduced into the medium pressure column at between 6 and 9 bars
EP1750074A1 (en) * 2005-08-02 2007-02-07 Linde Aktiengesellschaft Process and device for the cryogenic separation of air
WO2021204424A3 (en) * 2020-04-09 2021-12-02 Linde Gmbh Process for cryogenic fractionation of air, air fractionation plant and integrated system composed of at least two air fractionation plants

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105890283B (en) * 2015-01-26 2018-08-10 宝山钢铁股份有限公司 The nitrogen plug prevention and control method and system of interior boosting space division
WO2021005744A1 (en) * 2019-07-10 2021-01-14 太陽日酸株式会社 Air separation device and air separation method

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4705548A (en) * 1986-04-25 1987-11-10 Air Products And Chemicals, Inc. Liquid products using an air and a nitrogen recycle liquefier
EP0384688A2 (en) * 1989-02-24 1990-08-29 The BOC Group plc Air separation
DE4030749A1 (en) * 1990-09-28 1992-04-02 Linde Ag Low temp. sepn. of argon, oxygen and nitrogen from air - using intermediate liq. oxygen fraction as cooling medium for the argon finishing column
EP0527501A1 (en) * 1991-08-14 1993-02-17 Linde Aktiengesellschaft Air rectification process and apparatus

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0792326B2 (en) * 1987-03-06 1995-10-09 日本酸素株式会社 Air liquefaction separation method
CN1025067C (en) * 1989-02-23 1994-06-15 琳德股份公司 Process and method of seperating air by rectification

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4705548A (en) * 1986-04-25 1987-11-10 Air Products And Chemicals, Inc. Liquid products using an air and a nitrogen recycle liquefier
EP0384688A2 (en) * 1989-02-24 1990-08-29 The BOC Group plc Air separation
DE4030749A1 (en) * 1990-09-28 1992-04-02 Linde Ag Low temp. sepn. of argon, oxygen and nitrogen from air - using intermediate liq. oxygen fraction as cooling medium for the argon finishing column
EP0527501A1 (en) * 1991-08-14 1993-02-17 Linde Aktiengesellschaft Air rectification process and apparatus

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0684437A1 (en) * 1994-05-27 1995-11-29 The BOC Group plc Air separation
US5533339A (en) * 1994-05-27 1996-07-09 The Boc Group Plc Air separation
FR2830928A1 (en) * 2001-10-17 2003-04-18 Air Liquide Separation of air by cryogenic distillation with heat exchange cooling the compressed and purified inlet air before it is introduced into the medium pressure column at between 6 and 9 bars
WO2003033978A3 (en) * 2001-10-17 2003-10-02 Air Liquide Method for separating air by cryogenic distillation and installation therefor
US7219514B2 (en) 2001-10-17 2007-05-22 L'Air Liquide, Société Anonyme á Directoire et Conseil de Surveillance our l'Etude et l'Exploitation des Procédés Georges Claude Method for separating air by cryogenic distillation and installation therefor
EP1750074A1 (en) * 2005-08-02 2007-02-07 Linde Aktiengesellschaft Process and device for the cryogenic separation of air
WO2021204424A3 (en) * 2020-04-09 2021-12-02 Linde Gmbh Process for cryogenic fractionation of air, air fractionation plant and integrated system composed of at least two air fractionation plants

Also Published As

Publication number Publication date
EP0580345B1 (en) 1996-02-14
ES2085116T3 (en) 1996-05-16
JPH06159929A (en) 1994-06-07
KR940002589A (en) 1994-02-17
DE69301555D1 (en) 1996-03-28
DE69301555T2 (en) 1996-08-01
CA2100402A1 (en) 1994-01-21

Similar Documents

Publication Publication Date Title
EP0496355B1 (en) Method and apparatus for producing elevated pressure nitrogen
EP0645595B1 (en) Air separation schemes for oxygen and nitrogen co-production as gas and/or liquid products
EP0697576B1 (en) Air separation method and apparatus
US4715873A (en) Liquefied gases using an air recycle liquefier
US4702757A (en) Dual air pressure cycle to produce low purity oxygen
EP0580348B1 (en) Hybrid air and nitrogen recycle liquefier
EP0706020A2 (en) Side column cryogenic rectification system for producing lower purity oxygen
CA2228799C (en) Air separation with intermediate pressure vaporization and expansion
EP0644388A1 (en) Cryogenic air separation
EP0635690B1 (en) Cryogenic rectification system for producing lower purity oxygen
CA1283846C (en) Air separation process with modified single distillation columnnitrogen generator
EP0646755B1 (en) Cryogenic air separation process and apparatus producing elevated pressure nitrogen by pumped liquid nitrogen
US5682764A (en) Three column cryogenic cycle for the production of impure oxygen and pure nitrogen
EP0811816A2 (en) Method and apparatus for producing liquid products from air in various proportions
EP0584420A1 (en) Efficient single column air separation cycle and its integration with gas turbines
JP3190016B2 (en) Low-temperature distillation method for feed air producing high-pressure nitrogen
EP0580345B1 (en) Elevated pressure liquefier
JPH07305954A (en) Raw-material air low-temperature distillation method manufacturing extra-high purity oxygen product
JP2865281B2 (en) Low temperature distillation method of air raw material
CA2259079A1 (en) An air separation process using warm and cold expanders
EP0931999B1 (en) A multiple expander process to produce oxygen
US4869742A (en) Air separation process with waste recycle for nitrogen and oxygen production

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): BE DE ES FR GB IT NL

17P Request for examination filed

Effective date: 19940127

17Q First examination report despatched

Effective date: 19950131

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): BE DE ES FR GB IT NL

ITF It: translation for a ep patent filed

Owner name: DR. ING. A. RACHELI & C.

REF Corresponds to:

Ref document number: 69301555

Country of ref document: DE

Date of ref document: 19960328

ET Fr: translation filed
REG Reference to a national code

Ref country code: ES

Ref legal event code: FG2A

Ref document number: 2085116

Country of ref document: ES

Kind code of ref document: T3

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: BE

Payment date: 19970808

Year of fee payment: 5

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: BE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19980731

BERE Be: lapsed

Owner name: AIR PRODUCTS AND CHEMICALS INC.

Effective date: 19980731

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 20010614

Year of fee payment: 9

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: NL

Payment date: 20010618

Year of fee payment: 9

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 20010702

Year of fee payment: 9

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: ES

Payment date: 20010716

Year of fee payment: 9

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 20010731

Year of fee payment: 9

REG Reference to a national code

Ref country code: GB

Ref legal event code: IF02

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20020713

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: ES

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20020714

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20030201

Ref country code: DE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20030201

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 20020713

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20030331

NLV4 Nl: lapsed or anulled due to non-payment of the annual fee

Effective date: 20030201

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

REG Reference to a national code

Ref country code: ES

Ref legal event code: FD2A

Effective date: 20030811

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: IT

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES;WARNING: LAPSES OF ITALIAN PATENTS WITH EFFECTIVE DATE BEFORE 2007 MAY HAVE OCCURRED AT ANY TIME BEFORE 2007. THE CORRECT EFFECTIVE DATE MAY BE DIFFERENT FROM THE ONE RECORDED.

Effective date: 20050713