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US20070137248A1 - Method and apparatus for separating air by cryogenic distillation - Google Patents

Method and apparatus for separating air by cryogenic distillation Download PDF

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Publication number
US20070137248A1
US20070137248A1 US10/576,826 US57682604A US2007137248A1 US 20070137248 A1 US20070137248 A1 US 20070137248A1 US 57682604 A US57682604 A US 57682604A US 2007137248 A1 US2007137248 A1 US 2007137248A1
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Prior art keywords
air
pressure column
column
medium
low
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US10/576,826
Inventor
Herve Le Bihan
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LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
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LAir Liquide SA a Directoire et Conseil de Surveillance pour lEtude et lExploitation des Procedes Georges Claude
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Assigned to L'AIR LIQUIDE, SOCIETE ANONYME A DIRECTOIRE ET CONSEIL DE SURVEILLANCE POUR L'ETUDE ET L'EXPLOITATION DES PROCEDES GEORGES CLAUDE reassignment L'AIR LIQUIDE, SOCIETE ANONYME A DIRECTOIRE ET CONSEIL DE SURVEILLANCE POUR L'ETUDE ET L'EXPLOITATION DES PROCEDES GEORGES CLAUDE ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: LE BIHAN, HERVE
Publication of US20070137248A1 publication Critical patent/US20070137248A1/en
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    • 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
    • F25J3/04151—Purification and (pre-)cooling of the feed air; recuperative heat-exchange with product streams
    • F25J3/04163—Hot end purification of the feed air
    • F25J3/04169—Hot end purification of the feed air by adsorption of the impurities
    • F25J3/04175—Hot end purification of the feed air by adsorption of the impurities at a pressure of substantially more than the highest 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
    • F25J3/04006—Providing pressurised feed air or process streams within or from the air fractionation unit
    • F25J3/04048—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of cold gaseous streams, e.g. intermediate or oxygen enriched (waste) streams
    • F25J3/04054—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of cold gaseous streams, e.g. intermediate or oxygen enriched (waste) streams of air
    • 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
    • F25J3/0446—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 the heat generated by mixing two different phases
    • F25J3/04466—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 the heat generated by mixing two different phases for producing oxygen as a mixing column overhead gas by mixing gaseous air feed and liquid oxygen
    • 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
    • F25J3/04763—Start-up or control of the process; Details of the apparatus used
    • F25J3/04866—Construction and layout of air fractionation equipments, e.g. valves, machines
    • F25J3/04872—Vertical layout of cold equipments within in the cold box, e.g. columns, heat exchangers etc.
    • 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
    • F25J2200/04—Processes or apparatus using separation by rectification in a dual pressure main column system
    • F25J2200/06—Processes or apparatus using separation by rectification in a dual pressure main column system in a classical double column flow-sheet, 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
    • 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
    • F25J2235/00—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams
    • F25J2235/50—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams the fluid being oxygen
    • 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
    • F25J2245/50—Processes or apparatus involving steps for recycling of process streams the recycled stream being oxygen
    • 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
    • F25J2290/00—Other details not covered by groups F25J2200/00 - F25J2280/00
    • F25J2290/12—Particular process parameters like pressure, temperature, ratios

Definitions

  • the present invention relates to a method and an apparatus for separating air by cryogenic distillation.
  • it relates to an air separation method using a mixing column to produce impure oxygen gas.
  • EP A 0538118 teaches the use of a double column and a mixing column to produce impure oxygen, with a dedicated air booster to compress the air to the pressure of the mixing column.
  • the object of the present invention is to reduce the investment costs of such an apparatus.
  • the invention provides a method for separating air by cryogenic distillation in an installation comprising a medium-pressure column, a low-pressure column and a mixing column in which:
  • the invention provides an installation for separating air by cryogenic distillation in an apparatus comprising a medium-pressure column, a low-pressure column and a mixing column, a Claude turbine, a booster, means for compressing air, means for sending a portion of the compressed air of the air to the mixing column, means for sending another portion of the compressed air to the booster, means for sending -a fraction of the boosted air to the Claude turbine and for sending the expanded air to the medium-pressure column, means for sending the rest of the boosted air to the medium pressure and/or low-pressure column after liquefaction and expansion, and means for drawing off at least one liquid from the medium-pressure column and/or the low-pressure column as end product.
  • the booster may be coupled to the Claude turbine.
  • FIG. 1 schematically shows an embodiment of the air distillation installation according to the invention.
  • the air distillation installation shown in FIG. 1 is designed to produce impure oxygen OI, for example having a purity of 80 to 97% and preferably of 85 to 95% under a defined pressure P that is substantially different from 6 ⁇ 10 5 Pa abs., for example under 8 to 20 ⁇ 10 5 Pa.
  • the installation essentially comprises a heat exchange line 1 , a double distillation column itself comprising a medium-pressure column 3 , a low-pressure column 4 and a main condenser-reboiler 5 , and a mixing column 6 .
  • the mixing column 6 and the low-pressure column 4 are incorporated in a single structure.
  • the medium-pressure column 3 forms a separate structure and is surmounted by the condenser-reboiler 5 , as described in EP A 1978212.
  • the columns 3 and 4 typically operate under about 6 ⁇ 10 5 Pa and at about 1 ⁇ 10 5 Pa respectively.
  • a mixing column is a column that has the same structure as a distillation column but is used for mixing a relatively volatile gas, introduced at its base, and a less volatile liquid, introduced at its top, under conditions approaching reversibility.
  • Such a mixture produces cooling energy and therefore serves to reduce the energy consumption associated with distillation.
  • this mixture is further exploited to directly produce impure oxygen under the pressure P, as described below.
  • the air to be separated by distillation is compressed to 15 ⁇ 10 5 Pa (generally between 8 and 20 ⁇ 10 5 Pa) in a compressor C 01 and suitably cleansed, and divided into two.
  • One portion of this air accounting for between 40 and 90% of the air, is boosted in a booster 8 to a pressure of between 12 and 30 ⁇ 10 5 Pa, cooled in the heat exchange line 1 and divided into two fractions.
  • One fraction continues to be cooled in the heat exchange line 1 where it liquefies at least partially before being introduced into the medium-pressure column 3 via a line 7 .
  • a portion or all of this liquefied air may be sent to the low-pressure column 4 .
  • Liquid oxygen is drawn off at the bottom of the column 4 , and sent via the line 24 to the condenser-reboiler 5 , where it is partially vaporized to form a gas 25 that is sent to the low-pressure column 4 .
  • Liquid 26 is drawn off from the condenser 5 , compressed by a pump 13 to a pressure P 1 , slightly higher than the abovementioned pressure P to compensate for pressure drops (P 1 ⁇ P less than 1 ⁇ 10 5 Pa), and partly introduced at the top of the column 6 .
  • a portion 27 of the liquid oxygen can be sent to a storage unit.
  • Auxiliary air from the compressor C 01 compressed to a pressure substantially above the medium pressure and partially cooled in the heat exchange line 1 , is introduced at the base of the mixing column 6 .
  • Three liquid streams are drawn off from this column: at its base, liquid similar to the rich liquid and combined with it via a line 15 provided with a relief valve 15 A; at an intermediate point, a mixture essentially consisting of oxygen and nitrogen, which is sent to an intermediate point of the low-pressure column 4 , via a line 16 provided with a relief valve 17 ; and at its top, impure oxygen which, after heating in the heat exchange line, is removed, substantially at the pressure P, from the installation via a line 18 as producer gas OI.
  • a liquid nitrogen flow is drawn off at the top of the medium-pressure column 3 as end product.
  • FIG. 1 also shows auxiliary heat exchangers 19 , 20 for recovering the cold available in the fluids flowing in the installation.
  • the double column comprising the columns 3 and 4 can conventionally form a single structure, while the mixing column 6 forms a separate structure.
  • a flow of pressurized liquid oxygen and/or a flow of pressurized liquid nitrogen may be vaporized in the heat exchange line 1 or in a dedicated reboiler.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Separation By Low-Temperature Treatments (AREA)

Abstract

The invention concerns a method for separating air by cryogenic distillation in an installation comprising a medium pressure column (3), a low pressure column (4) and a mixing column (6). According to the method: air is compressed in a compressor (C01); is cooled in an exchange line (1); a first portion (2) of the air is fed to the vessel of the mixing column; a second portion of the air is fed to the medium pressure column where it separates; an oxygen-enriched liquid (19) and a nitrogen-enriched liquid (11) are fed from the medium pressure column to the low pressure column; an oxygen-rich liquid (26) is fed from the low pressure column to the top of the mixing column; at least one flow of liquid (27, 29) is drawn off from the medium or low pressure column; the second portion of air is boosted in a booster (8); this air is cooled in the exchange line; it is divided into a first fraction and second fraction; the first fraction of air is cooled in the exchange line; it is at least partially liquefied and then sent to the medium pressure column and/or the low pressure column; the second fraction of air is expanded in a Claude turbine (9) and is fed to the medium pressure column, and; an oxygen-rich flow (18) is drawn off from the mixing column and is heated in the exchange line.

Description

  • The present invention relates to a method and an apparatus for separating air by cryogenic distillation. In particular, it relates to an air separation method using a mixing column to produce impure oxygen gas.
  • EP A 0538118 teaches the use of a double column and a mixing column to produce impure oxygen, with a dedicated air booster to compress the air to the pressure of the mixing column.
  • The object of the present invention is to reduce the investment costs of such an apparatus.
  • According to one object, the invention provides a method for separating air by cryogenic distillation in an installation comprising a medium-pressure column, a low-pressure column and a mixing column in which:
      • (i) air is compressed in a compressor, cooled in a heat exchange line and a first portion of the air is sent to the vessel of the mixing column;
      • (ii) a second portion of the air is sent to the medium-pressure column where it is separated;
      • (iii) an oxygen-enriched liquid and a nitrogen-enriched liquid are sent from the medium-pressure column to the low-pressure column;
      • (iv) an oxygen-enriched liquid is sent from the low-pressure column to the top of the mixing column;
      • (v) at least one flow of liquid is drawn off from the medium or low-pressure column;
      • (vi) the second portion of the air is boosted in a booster, cooled in the heat exchange line, and divided into a first fraction and a second fraction;
      • (vii) the first fraction of the air is cooled in the heat exchange line, at least partially liquefied, and sent to the medium-pressure column and/or the low-pressure column;
      • (viii) the second fraction of the air is expanded in a Claude turbine and sent to the medium-pressure column; and
      • (ix) an oxygen-rich flow is drawn off from the mixing column and heated in the heat exchange line.
  • According to other optional aspects:
      • the liquid drawn off from the medium or low-pressure column is an end product;
      • the booster is coupled to the Claude turbine;
      • the booster is a cold booster;
      • the mixing column operates at between 8 and 20 bar abs.;
      • all the air sent for distillation is compressed to between 8 and 20 bar abs.;
      • between 40 and 90% of the air sent for distillation is boosted;
      • the boosted air is boosted to between 12 and 30 bar abs.
  • According to another aspect, the invention provides an installation for separating air by cryogenic distillation in an apparatus comprising a medium-pressure column, a low-pressure column and a mixing column, a Claude turbine, a booster, means for compressing air, means for sending a portion of the compressed air of the air to the mixing column, means for sending another portion of the compressed air to the booster, means for sending -a fraction of the boosted air to the Claude turbine and for sending the expanded air to the medium-pressure column, means for sending the rest of the boosted air to the medium pressure and/or low-pressure column after liquefaction and expansion, and means for drawing off at least one liquid from the medium-pressure column and/or the low-pressure column as end product.
  • The booster may be coupled to the Claude turbine.
  • One embodiment of the invention will now be described with reference to the drawing appended hereto, in which FIG. 1 schematically shows an embodiment of the air distillation installation according to the invention.
  • The air distillation installation shown in FIG. 1 is designed to produce impure oxygen OI, for example having a purity of 80 to 97% and preferably of 85 to 95% under a defined pressure P that is substantially different from 6×105 Pa abs., for example under 8 to 20×105 Pa. The installation essentially comprises a heat exchange line 1, a double distillation column itself comprising a medium-pressure column 3, a low-pressure column 4 and a main condenser-reboiler 5, and a mixing column 6. The mixing column 6 and the low-pressure column 4 are incorporated in a single structure. The medium-pressure column 3 forms a separate structure and is surmounted by the condenser-reboiler 5, as described in EP A 1978212. The columns 3 and 4 typically operate under about 6×105 Pa and at about 1×105 Pa respectively.
  • As explained in detail in document U.S. Pat. No. 4,022,030, a mixing column is a column that has the same structure as a distillation column but is used for mixing a relatively volatile gas, introduced at its base, and a less volatile liquid, introduced at its top, under conditions approaching reversibility.
  • Such a mixture produces cooling energy and therefore serves to reduce the energy consumption associated with distillation. In the present case, this mixture is further exploited to directly produce impure oxygen under the pressure P, as described below.
  • The air to be separated by distillation is compressed to 15×105 Pa (generally between 8 and 20×105 Pa) in a compressor C01 and suitably cleansed, and divided into two. One portion of this air, accounting for between 40 and 90% of the air, is boosted in a booster 8 to a pressure of between 12 and 30×105 Pa, cooled in the heat exchange line 1 and divided into two fractions. One fraction continues to be cooled in the heat exchange line 1 where it liquefies at least partially before being introduced into the medium-pressure column 3 via a line 7. A portion or all of this liquefied air may be sent to the low-pressure column 4. Another fraction of the air boosted in 8 and then cooled, is expanded to the medium pressure in a Claude turbine 9 coupled to the booster 8, and then sent to the bottom of the medium-pressure column 3 in gaseous form, a few trays below the inlet point of the line 7. “Rich liquid” (oxygen-enriched air), drawn off from the bottom of the column 3, is expanded in a relief valve 10 and introduced into the column 4. “Poor liquid” (impure nitrogen) 11 drawn off at the top of the column 3 is expanded in a relief valve 12 and introduced at the top of the column 4, and the gas produced at the top of the column 4 constituting the waste gas N1 of the installation is heated in the heat exchange line 1 and discharged from the installation.
  • Liquid oxygen, more or less pure according to the settings of the double column, is drawn off at the bottom of the column 4, and sent via the line 24 to the condenser-reboiler 5, where it is partially vaporized to form a gas 25 that is sent to the low-pressure column 4. Liquid 26 is drawn off from the condenser 5, compressed by a pump 13 to a pressure P1, slightly higher than the abovementioned pressure P to compensate for pressure drops (P1−P less than 1×105 Pa), and partly introduced at the top of the column 6. A portion 27 of the liquid oxygen can be sent to a storage unit. Auxiliary air from the compressor C01, compressed to a pressure substantially above the medium pressure and partially cooled in the heat exchange line 1, is introduced at the base of the mixing column 6. Three liquid streams are drawn off from this column: at its base, liquid similar to the rich liquid and combined with it via a line 15 provided with a relief valve 15A; at an intermediate point, a mixture essentially consisting of oxygen and nitrogen, which is sent to an intermediate point of the low-pressure column 4, via a line 16 provided with a relief valve 17; and at its top, impure oxygen which, after heating in the heat exchange line, is removed, substantially at the pressure P, from the installation via a line 18 as producer gas OI.
  • A liquid nitrogen flow is drawn off at the top of the medium-pressure column 3 as end product.
  • FIG. 1 also shows auxiliary heat exchangers 19, 20 for recovering the cold available in the fluids flowing in the installation.
  • It can be readily understood that the double column comprising the columns 3 and 4 can conventionally form a single structure, while the mixing column 6 forms a separate structure.
  • Optionally, a flow of pressurized liquid oxygen and/or a flow of pressurized liquid nitrogen may be vaporized in the heat exchange line 1 or in a dedicated reboiler.

Claims (11)

1-10. (canceled)
11: A method for separating air by cryogenic distillation in an installation comprising a medium-pressure column, a low-pressure column and a mixing column in which:
a) air is compressed in a compressor, cooled in a heat exchange line and a first portion of the air is sent to the vessel of the mixing column;
b) a second portion of the air is sent to the medium-pressure column where it is separated;
c) an oxygen-enriched liquid and a nitrogen-enriched liquid are sent from the medium-pressure column to the low-pressure column;
d) an oxygen-enriched liquid is sent from the low-pressure column to the top of the mixing column;
e) at least one flow of liquid is drawn off from the medium or low-pressure column;
f) the second portion of the air is boosted in a booster, cooled in the heat exchange line, and divided into a first fraction and a second fraction;
g) the first fraction of the air is cooled in the heat exchange line, at least partially liquefied, and sent to the medium-pressure column and/or the low-pressure column;
h) the second fraction of the air is expanded in a Claude turbine and sent to the medium-pressure column; and
i) an oxygen-rich flow is drawn off from the mixing column and heated in the heat exchange line.
12: The method of claim 11, in which the liquid drawn off from the medium or low-pressure column is an end product.
13: The method of claim 11, in which the booster is coupled to the Claude turbine.
14: The method of claim 11, in which the booster is a cold booster.
15: The method of claim 11, in which the mixing column operates at between 8 and 20 bar abs.
16: The method of claim 11, in which all the air sent for distillation is compressed to between 8 and 20 bar abs.
17: The method of claim 11, in which between 40 and 90% of the air sent for distillation is boosted.
18: The method of claim 11, in which the boosted air is boosted to between 12 and 30 bar abs.
19: An installation for separating air by cryogenic distillation in an apparatus comprising a medium-pressure column, a low-pressure column and a mixing column, a Claude turbine, a booster, means for compressing air, means for sending a portion of the compressed air of the air to the mixing column, means for sending another portion of the compressed air to the booster, means for sending a fraction of the boosted air to the Claude turbine and for sending the expanded air to the medium-pressure column, means for sending the rest of the boosted air to the medium pressure and/or low-pressure column after liquefaction and expansion, and means for drawing off at least one liquid from the medium-pressure column and/or the low-pressure column as end product.
20: The installation of claim 19, in which the booster is coupled to the Claude turbine.
US10/576,826 2003-11-04 2004-10-26 Method and apparatus for separating air by cryogenic distillation Abandoned US20070137248A1 (en)

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FR0350779A FR2861841B1 (en) 2003-11-04 2003-11-04 METHOD AND APPARATUS FOR AIR SEPARATION BY CRYOGENIC DISTILLATION
FR0350779 2003-11-04
PCT/FR2004/050537 WO2005045339A1 (en) 2003-11-04 2004-10-26 Method and device for separating air by cryogenic distillation

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CN100538233C (en) 2009-09-09
JP2007510879A (en) 2007-04-26
FR2861841B1 (en) 2006-06-30
EP1690053A1 (en) 2006-08-16
WO2005045339A1 (en) 2005-05-19
CN1871485A (en) 2006-11-29

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