EP0713069A1 - Process and plant for air separation - Google Patents

Process and plant for air separation Download PDF

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Publication number
EP0713069A1
EP0713069A1 EP96200235A EP96200235A EP0713069A1 EP 0713069 A1 EP0713069 A1 EP 0713069A1 EP 96200235 A EP96200235 A EP 96200235A EP 96200235 A EP96200235 A EP 96200235A EP 0713069 A1 EP0713069 A1 EP 0713069A1
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EP
European Patent Office
Prior art keywords
pressure column
nitrogen
column
low pressure
enriched
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.)
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EP96200235A
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German (de)
French (fr)
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EP0713069B1 (en
Inventor
Jean-Louis Girault
Phillippe Mazières
Jean-Pierre Tranier
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Air Liquide SA
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Original Assignee
Air Liquide SA
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
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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
    • F25J3/04187—Cooling of the purified feed air by recuperative heat-exchange; Heat-exchange with product streams
    • F25J3/04193—Division of the main heat exchange line in consecutive sections having different functions
    • F25J3/04206—Division of the main heat exchange line in consecutive sections having different functions including a so-called "auxiliary vaporiser" for vaporising and producing a gaseous product
    • 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
    • F25J3/04078—Providing pressurised feed air or process streams within or from the air fractionation unit providing pressurized products by liquid compression and vaporisation with cold recovery, i.e. so-called internal compression
    • F25J3/0409—Providing pressurised feed air or process streams within or from the air fractionation unit providing pressurized products by liquid compression and vaporisation with cold recovery, i.e. so-called internal compression of 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
    • F25J3/04248—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
    • F25J3/04303—Lachmann expansion, i.e. expanded into oxygen producing or low 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
    • F25J3/04351—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
    • F25J3/04406—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
    • F25J3/04418—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 with thermally overlapping high and low pressure columns
    • 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
    • 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
    • F25J2200/54—Processes or apparatus using separation by rectification using multiple (re-)boiler-condensers at different heights of the column in the low 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
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/90—Details relating to column internals, e.g. structured packing, gas or liquid distribution
    • 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
    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/42—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
    • F25J2215/00—Processes characterised by the type or other details of the product stream
    • F25J2215/50—Oxygen or special cases, e.g. isotope-mixtures or low purity O2
    • 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
    • F25J2250/00—Details related to the use of reboiler-condensers
    • F25J2250/10—Boiler-condenser with superposed stages
    • 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
    • F25J2250/00—Details related to the use of reboiler-condensers
    • F25J2250/20—Boiler-condenser with multiple exchanger cores in parallel or with multiple re-boiling or condensing streams
    • 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
    • F25J2250/00—Details related to the use of reboiler-condensers
    • F25J2250/30—External or auxiliary boiler-condenser in general, e.g. without a specified fluid or one fluid is not a primary air component or an intermediate fluid
    • F25J2250/40—One fluid being 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
    • F25J2250/00—Details related to the use of reboiler-condensers
    • F25J2250/30—External or auxiliary boiler-condenser in general, e.g. without a specified fluid or one fluid is not a primary air component or an intermediate fluid
    • F25J2250/50—One fluid being oxygen
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S62/00—Refrigeration
    • Y10S62/939—Partial feed stream expansion, air

Definitions

  • the present invention relates to a process for the separation of air by distillation in a double column air distillation installation, the double column comprising a medium pressure column and a low pressure column.
  • the invention also relates to an apparatus for producing gaseous product comprising an air compressor, a heat exchanger, a medium pressure column, a low pressure column, means for sending air to the medium pressure column via the heat exchanger, means for withdrawing a liquid from the tank of the low pressure column and for sending the liquid to the heat exchanger, characterized in that it comprises a first nitrogen compressor, means for sending a nitrogen-enriched fluid from the low pressure column to the first nitrogen compressor, from the first nitrogen compressor by means of cooling of the cooling means directly or indirectly at the medium pressure column.
  • the installation shown in Figure 1 is intended to produce oxygen at a purity of around 85% under a pressure of around 7.4 x 105 Pa abs. It essentially comprises a double column 1 for air distillation consisting of a medium pressure column (or "MP column") 2 operating at 15.7 x 105 Pa abs. and a low pressure column (or "BP column”) 3 operating at 6.3 x 105 Pa abs, a main heat exchange line 4, a sub-cooler 5, an auxiliary evaporator-condenser 6 and a turbine 7 blowing air into the low pressure column.
  • Column 3 is superimposed on column 2 and contains in the tank a vaporizer-condenser 8 and, above this, a second vaporizer-condenser 9.
  • the air to be distilled arrives at medium pressure via a line 10 and enters the exchange line 4. Most of this air is cooled to the vicinity of its dew point and leaves the cold end of the line d exchange at an intermediate temperature, expanded at low pressure in the turbine 7 to keep the installation cold, and blown at an intermediate level in the LP column 3.
  • a fraction of the fully cooled air is introduced, via a pipe 11, at the base of the column MP 2, and the rest is condensed in the vaporizer-condenser 6; part of the liquid obtained is introduced via a line 12 at an intermediate point in column 2, and the rest is, after sub-cooling in 5 and expansion in an expansion valve 13, introduced at an intermediate point in column BP 3 .
  • the "rich liquid” (oxygen-enriched air) collected in the bottom of the MP column is, after sub-cooling in 5 and expansion in an expansion valve 14, introduced at an intermediate point of the LP column.
  • “lean liquid” (impure nitrogen) withdrawn at an intermediate point of the column MP is, after sub-cooling in 5 and expansion in an expansion valve 15, introduced at the top of the column BP.
  • the almost pure nitrogen produced at the head of the MP column is partly removed from the installation as a product, after heating in the exchange line, via a line 16 and, for the rest, sent in gaseous form. via a line 17, at medium pressure, in the upper evaporator-condenser 9. After condensation, this nitrogen is returned to reflux at the head of the column MP via a line 18.
  • impure nitrogen gas drawn off at an intermediate point in column 2 and, in this example, at the same level as the lean liquid, is sent via a line 19, under medium pressure, to the vaporizer-condenser lower 8.
  • the liquid thus obtained is returned under reflux to the column MP, at approximately the same level, via a line 20.
  • the pump 23 could be omitted, the impure oxygen then being vaporized at 6 under the low pressure.
  • the temperature of the bottom liquid of the LP column is determined by that of the gas condensed in this vaporizer-condenser.
  • the temperature of the tank liquid, which is impure oxygen is relatively high.
  • the pressure of the LP column that is to say the low pressure, can be increased.
  • impure oxygen and impure nitrogen are obtained under increased pressure, which makes it possible to make savings on their recovery, for example on the energy required to compress the impure nitrogen to the desired pressure in a gas turbine (not shown) cut at installation, for example as described in the aforementioned US-A-4,224,045.
  • the upper vaporizer-condenser 9 serves to provide the necessary reflux at the top of the column MP.
  • the impure oxygen is withdrawn in gaseous form from the LP column 3, and is simply reheated in the exchange line 4 before its evacuation goes to the pipe 24. This is particularly advantageous when the impure oxygen is desired under the low pressure. Consequently, the vaporizer-condenser 6 is eliminated.
  • a fraction of the medium pressure air, cooled in the vicinity of its dew point, is sent, via a pipe 26, to the lower vaporizer-condenser 8 in place of the intermediate gas of FIG. 1.
  • This intermediate gas feeds an intermediate vaporizer-condenser 27 located between the lower vaporizer-condensers 8 and upper 9.
  • the liquefied air from the vaporizer-condenser 8 is sent partly, via a line 28, to the column MP and partly, after sub-cooling in 5 and expansion in the expansion valve 13, in the column BP.
  • the impure oxygen is withdrawn in liquid form from the tank of the LP column, then is brought by a pump 23 to the desired production pressure, then vaporized and heated under this pressure in the exchange line 4 before being evacuated from the installation via line 24.
  • a nitrogen cycle is provided, known as the rectification support cycle, which is used at the same time to ensure the vaporization of impure oxygen: part of the nitrogen produced at the head of column 3 (which, in this case, has at the head a "minaret" 30 which is supplied at its top with pure liquid nitrogen coming from the upper evaporator-condenser 9 and which, consequently, produces pure nitrogen under low pressure) is, after heating in the exchange line, compressed by a compressor 31 at medium pressure.
  • the rectification support cycle which is used at the same time to ensure the vaporization of impure oxygen: part of the nitrogen produced at the head of column 3 (which, in this case, has at the head a "minaret" 30 which is supplied at its top with pure liquid nitrogen coming from the upper evaporator-condenser 9 and which, consequently, produces pure nitrogen under low pressure) is, after heating in the exchange line, compressed by a compressor 31 at medium pressure.
  • This medium pressure nitrogen combined with a current of medium pressure nitrogen taken from the line 16, is compressed again by a compressor 33 to a vaporization pressure of the impure oxygen compressed by the pump 23, liquefied in the line of exchange then, after expansion in an expansion valve 34, introduced under reflux at the head of the column MP.
  • FIG. 4 also includes a BP 3 column with a minaret 30.
  • a BP 3 column with a minaret 30 is high pressure air, boosted to a vaporization pressure of impure oxygen by a booster 35, which ensures the vaporization of the impure oxygen in the exchange line 4.
  • this air is, after liquefaction and expansion in an expansion valve 36 and in the expansion valve 13, distributed between the two columns 2 and 3. Consequently, the compressor 33 and the expansion valve 34 of FIG. 3 are eliminated.
  • This nitrogen pressure can be chosen between medium pressure and the pressure for which the nitrogen condenses at the cold end of the line exchange.

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

Abstract

O2 of ca. 85% purity is produced by distilling air in a double column comprising a medium pressure column (2) and a low pressure column (3) associated with a main heat exchanger (4). The incoming air (10) is cooled by vaporising outgoing O2-rich liq. from the low pressure column (3). Some of the cooled air is sepd. into O-rich and N-rich streams in the medium pressure column (2), and both streams are cooled in sec. heat exchanger (5) and transferred to the low pressure column (3) at different levels. A N-rich gas fraction obtd. from the low pressure column (3) is compressed, cooled in the heat exchanger (4), where it assists in vaporising the outgoing O2-rich liq., and recycled directly or indirectly to the medium pressure column (2).

Description

La présente invention est relative à un procédé de séparation d'air par distillation dans une installation de distillation d'air à double colonne, la double colonne comprenant une colonne moyenne pression et une colonne basse pression.The present invention relates to a process for the separation of air by distillation in a double column air distillation installation, the double column comprising a medium pressure column and a low pressure column.

EP-A-0.042.676 divulgue un procédé dans lequel :

  • on refroidit un débit d'air et on l'envoie à la colonne moyenne pression ;
  • on sépare l'air par distillation dans la colonne moyenne pression pour produire un fluide enrichi en oxygène et un fluide enrichi en azote ;
  • on envoie lesdits fluides à la colonne basse pression ;
  • on soutire un liquide riche en oxygène de la colonne basse pression et on le vaporise; et
  • on soutire un gaz enrichi en azote de la colonne basse pression.
EP-A-0.042.676 discloses a process in which:
  • an air flow is cooled and sent to the medium pressure column;
  • air is separated by distillation in the medium pressure column to produce a fluid enriched in oxygen and a fluid enriched in nitrogen;
  • said fluids are sent to the low pressure column;
  • a liquid rich in oxygen is drawn from the low pressure column and vaporized; and
  • a nitrogen-enriched gas is drawn off from the low pressure column.

Dans le procédé de EP-A-0.042.676, de l'azote est soutiré de la colonne moyenne pression, réchauffé à la température ambiante, comprimé à une pression élevée, liquéfié et renvoyé à la colonne moyenne pression.In the process of EP-A-0.042.676, nitrogen is withdrawn from the medium pressure column, warmed to room temperature, compressed at high pressure, liquefied and returned to the medium pressure column.

A cet effet, l'invention a pour objet un procédé caractérisé en ce que :

  • on comprime le gaz enrichi en azote soutiré de la colonne basse pression, on le refroidit et on envoie le fluide refroidi à la colonne moyenne pression ;
  • on vaporise le liquide riche en oxygène par échange de chaleur avec le débit d'air.
To this end, the subject of the invention is a method characterized in that:
  • the nitrogen-enriched gas withdrawn from the low pressure column is compressed, it is cooled and the cooled fluid is sent to the medium pressure column;
  • the oxygen-rich liquid is vaporized by heat exchange with the air flow.

L'invention a également pour objet un appareil de production de produit gazeux comprenant un compresseur d'air, un échangeur de chaleur, une colonne moyenne pression, une colonne basse pression, des moyens pour envoyer de l'air à la colonne moyenne pression via l'échangeur de chaleur, des moyens pour soutirer un liquide de la cuve de la colonne basse pression et pour envoyer le liquide à l'échangeur de chaleur, caractérisé en ce qu'il comprend un premier compresseur d'azote, des moyens pour envoyer un fluide enrichi en azote de la colonne basse pression au premier compresseur d'azote, du premier compresseur d'azote au moyen de refroidissement du moyen de refroidissement directement ou indirectement à la colonne moyenne pression.The invention also relates to an apparatus for producing gaseous product comprising an air compressor, a heat exchanger, a medium pressure column, a low pressure column, means for sending air to the medium pressure column via the heat exchanger, means for withdrawing a liquid from the tank of the low pressure column and for sending the liquid to the heat exchanger, characterized in that it comprises a first nitrogen compressor, means for sending a nitrogen-enriched fluid from the low pressure column to the first nitrogen compressor, from the first nitrogen compressor by means of cooling of the cooling means directly or indirectly at the medium pressure column.

Suivant d'autres caractéristiques, l'appareil comprend des moyens pour :

  • pressuriser le liquide avant de l'envoyer à l'échangeur de chaleur ;
  • comprimer un gaz de tête de la colonne moyenne pression et des moyens pour envoyer le gaz de tête comprimé à l'échangeur de chaleur ;
  • envoyer le fluide comprimé enrichi en azote à un condenseur de cuve de la colonne basse pression.
According to other characteristics, the apparatus comprises means for:
  • pressurize the liquid before sending it to the heat exchanger;
  • compressing an overhead gas from the medium pressure column and means for sending the compressed overhead gas to the heat exchanger;
  • send the compressed nitrogen-enriched fluid to a tank condenser in the low-pressure column.

Des exemples de mise en oeuvre de l'invention vont maintenant être décrits en regard des dessins annexés sur lesquels les figures 3 et 4 représentent schématiquement deux modes de réalisation de l'installation de distillation d'air conforme à l'invention et les figures 1 et 2 représentent d'autres modes de réalisation d'une installation de distillation d'air.Examples of implementation of the invention will now be described with reference to the accompanying drawings in which Figures 3 and 4 schematically represent two embodiments of the air distillation installation according to the invention and Figures 1 and 2 represent other embodiments of an air distillation installation.

L'installation représentée à la figure 1 est destinée à produire de l'oxygène à une pureté de l'ordre de 85 % sous une pression de l'ordre de 7,4 x 10⁵ Pa abs. Elle comprend essentiellement une double colonne 1 de distillation d'air constituée d'une colonne moyenne pression (ou "colonne MP") 2 fonctionnant sous 15,7 x 10⁵ Pa abs. et d'une colonne basse pression (ou "colonne BP") 3 fonctionnant sous 6,3 x 10⁵ Pa abs, une ligne d'échange thermique principale 4, un sous-refroidisseur 5, un vaporiseur-condenseur auxiliaire 6 et une turbine 7 d'insufflation d'air dans la colonne basse pression. La colonne 3 est superposée à la colonne 2 et contient en cuve un vaporiseur-condenseur 8 et, au-dessus de celui-ci, un second vaporiseur-condenseur 9.The installation shown in Figure 1 is intended to produce oxygen at a purity of around 85% under a pressure of around 7.4 x 10⁵ Pa abs. It essentially comprises a double column 1 for air distillation consisting of a medium pressure column (or "MP column") 2 operating at 15.7 x 10⁵ Pa abs. and a low pressure column (or "BP column") 3 operating at 6.3 x 10⁵ Pa abs, a main heat exchange line 4, a sub-cooler 5, an auxiliary evaporator-condenser 6 and a turbine 7 blowing air into the low pressure column. Column 3 is superimposed on column 2 and contains in the tank a vaporizer-condenser 8 and, above this, a second vaporizer-condenser 9.

L'air à distiller arrive sous la moyenne pression via une conduite 10 et pénètre dans la ligne d'échange 4. La majeure partie de cet air est refroidie jusqu'au voisinage de son point de rosée et sort au bout froid de la ligne d'échange à une température intermédiaire, détendu à la basse pression dans la turbine 7 pour assurer le maintien en froid de l'installation, et insufflé à un niveau intermédiaire dans la colonne BP 3.The air to be distilled arrives at medium pressure via a line 10 and enters the exchange line 4. Most of this air is cooled to the vicinity of its dew point and leaves the cold end of the line d exchange at an intermediate temperature, expanded at low pressure in the turbine 7 to keep the installation cold, and blown at an intermediate level in the LP column 3.

Une fraction de l'air entièrement refroidi est introduit, via une conduite 11, à la base de la colonne MP 2, et le reste est condensé dans le vaporiseur-condenseur 6 ; une partie du liquide obtenu est introduite via une conduite 12 en un point intermédiaire de la colonne 2, et le reste est, après sous-refroidissement en 5 et détente dans une vanne de détente 13, introduit en un point intermédiaire de la colonne BP 3.A fraction of the fully cooled air is introduced, via a pipe 11, at the base of the column MP 2, and the rest is condensed in the vaporizer-condenser 6; part of the liquid obtained is introduced via a line 12 at an intermediate point in column 2, and the rest is, after sub-cooling in 5 and expansion in an expansion valve 13, introduced at an intermediate point in column BP 3 .

Le "liquide riche" (air enrichi en oxygène) recueilli en cuve de la colonne MP est, après sous-refroidissement en 5 et détente dans une vanne de détente 14, introduit en un point intermédiaire de la colonne BP. De même, du "liquide pauvre" (azote impur) soutiré en un point intermédiaire de la colonne MP est, après sous-refroidissement en 5 et détente dans une vanne de détente 15, introduit au sommet de la colonne BP.The "rich liquid" (oxygen-enriched air) collected in the bottom of the MP column is, after sub-cooling in 5 and expansion in an expansion valve 14, introduced at an intermediate point of the LP column. Likewise, "lean liquid" (impure nitrogen) withdrawn at an intermediate point of the column MP is, after sub-cooling in 5 and expansion in an expansion valve 15, introduced at the top of the column BP.

L'azote à peu près pur produit en tête de la colonne MP est pour partie évacué de l'installation en tant que produit, après réchauffement dans la ligne d'échange, via une conduite 16 et, pour le reste, envoyé sous forme gazeuse via une conduite 17, sous la moyenne pression, dans le vaporiseur-condenseur supérieur 9. Après condensation, cet azote est renvoyé en reflux en tête de la colonne MP via une conduite 18.The almost pure nitrogen produced at the head of the MP column is partly removed from the installation as a product, after heating in the exchange line, via a line 16 and, for the rest, sent in gaseous form. via a line 17, at medium pressure, in the upper evaporator-condenser 9. After condensation, this nitrogen is returned to reflux at the head of the column MP via a line 18.

De plus, de l'azote impur gazeux, soutiré en un point intermédiaire de la colonne 2 et, dans cet exemple, au même niveau que le liquide pauvre, est envoyé via une conduite 19, sous la moyenne pression, dans le vaporiseur-condenseur inférieur 8. Le liquide ainsi obtenu est renvoyé en reflux dans la colonne MP, à peu près au même niveau, via une conduite 20.In addition, impure nitrogen gas, drawn off at an intermediate point in column 2 and, in this example, at the same level as the lean liquid, is sent via a line 19, under medium pressure, to the vaporizer-condenser lower 8. The liquid thus obtained is returned under reflux to the column MP, at approximately the same level, via a line 20.

Les courants de fluides sortant de la double colonne sont :

  • au sommet de la colonne MP, de l'azote moyenne pression, dont il a été question plus haut ;
  • au sommet de la colonne BP, de l'azote impur, constituant le gaz résiduaire de l'installation. Cet azote impur, après réchauffement dans le sous-refroidisseur 5 et dans la ligne d'échange 4, est évacué va une conduite 21 ; et
  • en cuve de la colonne BP, de l'oxygène impur liquide. Ce liquide est soutiré via une conduite 22, comprimé par une pompe 23 à la pression de production (7,4 x 10⁵ Pa abs dans cet exemple), puis vaporisé dans le vaporiseur-condenseur 6 en condensant la fraction d'air moyenne pression qui traverse ce dernier, puis réchauffé sous forme gazeuse dans la ligne d'échange et évacué de l'installation via une conduite de production 24.
The streams of fluids leaving the double column are:
  • at the top of the MP column, medium pressure nitrogen, which was discussed above;
  • at the top of the LP column, impure nitrogen, constituting the waste gas from the installation. This impure nitrogen, after heating in the sub-cooler 5 and in the exchange line 4, is evacuated goes a line 21; and
  • in the bottom of the BP column, liquid impure oxygen. This liquid is drawn off via a line 22, compressed by a pump 23 at the production pressure (7.4 x 10⁵ Pa abs in this example), then vaporized in the evaporator-condenser 6 by condensing the fraction of medium pressure air which crosses the latter, then heated in gaseous form in the exchange line and discharged from the installation via a production line 24.

En variante, la pompe 23 pourrait être supprimée, l'oxygène impur étant alors vaporisé en 6 sous la basse pression.As a variant, the pump 23 could be omitted, the impure oxygen then being vaporized at 6 under the low pressure.

La description ci-dessus montre que, pour un écart de température donné dans le vaporiseur-condenseur 8, la température du liquide de cuve de la colonne BP est déterminée par celle du gaz condensé dans ce vaporiseur-condenseur. Comme il s'agit d'un gaz intermédiaire de la colonne MP, plus chaud que l'azote de tête de cette colonne, la température du liquide de cuve, qui est l'oxygène impur, est relativement élevée. Par suite, pour une pureté désirée de cet oxygène impur, la pression de la colonne BP, c'est-à-dire la basse pression, peut être augmentée. Finalement, on obtient de l'oxygène impur et de l'azote impur sous une pression accrue, ce qui permet de réaliser des économies sur leur valorisation, par exemple sur l'énergie nécessaire pour comprimer l'azote impur à la pression voulue dans une turbine à gaz (non représentée) coupée à l'installation, par exemple de la manière décrite dans le brevet US-A-4.224.045 précité.The above description shows that, for a given temperature difference in the vaporizer-condenser 8, the temperature of the bottom liquid of the LP column is determined by that of the gas condensed in this vaporizer-condenser. As it is an intermediate gas in column MP, hotter than the nitrogen at the top of this column, the temperature of the tank liquid, which is impure oxygen, is relatively high. As a result, for a desired purity of this impure oxygen, the pressure of the LP column, that is to say the low pressure, can be increased. Finally, impure oxygen and impure nitrogen are obtained under increased pressure, which makes it possible to make savings on their recovery, for example on the energy required to compress the impure nitrogen to the desired pressure in a gas turbine (not shown) cut at installation, for example as described in the aforementioned US-A-4,224,045.

Dans ce contexte, le vaporiseur-condenseur supérieur 9 sert à fournir le reflux nécessaire en tête de la colonne MP.In this context, the upper vaporizer-condenser 9 serves to provide the necessary reflux at the top of the column MP.

Si les températures des deux gaz alimentant les deux vaporiseurs-condenseurs sont nettement différentes l'une de l'autre, il est nécessaire de prévoir un certain nombre de plateaux de distillation 25 entre ces vaporiseurs-condenseurs. Dans le cas contraire, ces plateaux peuvent être supprimés, ce qui simplifie la construction de la colonne BP, les deux vaporiseurs-condenseurs pouvant même être intégrés en un seul échangeur de chaleur. C'est pourquoi les plateaux 25 ont été représentés en trait interrompu.If the temperatures of the two gases supplying the two vaporizer-condensers are clearly different from each other, it is necessary to provide a number of distillation plates 25 between these vaporizer-condensers. Otherwise, these plates can be removed, which simplifies the construction of the LP column, the two vaporizers-condensers can even be integrated into a single heat exchanger. This is why the plates 25 have been shown in broken lines.

L'installation représentée à la figure 2 ne diffère de la figure 1 que par les points suivants :The installation shown in Figure 2 differs from Figure 1 only in the following points:

L'oxygène impur est soutiré sous forme gazeuse de la colonne BP 3, et est simplement réchauffé dans la ligne d'échange 4 avant son évacuation va la conduite 24. Ceci est particulièrement intéressant lorsque l'oxygène impur est désiré sous la basse pression. En conséquence, le vaporiseur-condenseur 6 est supprimé.The impure oxygen is withdrawn in gaseous form from the LP column 3, and is simply reheated in the exchange line 4 before its evacuation goes to the pipe 24. This is particularly advantageous when the impure oxygen is desired under the low pressure. Consequently, the vaporizer-condenser 6 is eliminated.

De plus, une fraction de l'air moyenne pression, refroidi au voisinage de son point de rosée est envoyée, via une conduite 26, dans le vaporiseur-condenseur inférieur 8 à la place du gaz intermédiaire de la figure 1. Ce gaz intermédiaire, quant à lui, alimente un vaporiseur-condenseur intermédiaire 27 situé entre les vaporiseurs-condenseurs inférieur 8 et supérieur 9. Comme précédemment, il peut y avoir ou non des plateaux entre les paires de vaporiseurs-condenseurs. L'air liquéfié issu du vaporiseur-condenseur 8 est envoyé pour partie, via une conduite 28, dans la colonne MP et pour partie, après sous-refroidissement en 5 et détente dans la vanne de détente 13, dans la colonne BP.In addition, a fraction of the medium pressure air, cooled in the vicinity of its dew point, is sent, via a pipe 26, to the lower vaporizer-condenser 8 in place of the intermediate gas of FIG. 1. This intermediate gas, meanwhile, feeds an intermediate vaporizer-condenser 27 located between the lower vaporizer-condensers 8 and upper 9. As before, there may be or not trays between the pairs of vaporizers-condensers. The liquefied air from the vaporizer-condenser 8 is sent partly, via a line 28, to the column MP and partly, after sub-cooling in 5 and expansion in the expansion valve 13, in the column BP.

Par rapport à la solution de la figure 1, on obtient une température plus élevée en cuve de la colonne BP, ce qui est favorable à l'augmentation de la basse pression. En revanche, on doit vaporiser un liquide plus riche en oxygène que l'oxygène impur à produire, ce qui tend à réduire la basse pression.Compared to the solution of FIG. 1, a higher temperature is obtained in the bottom of the LP column, which is favorable to the increase in the low pressure. On the other hand, a liquid richer in oxygen than the impure oxygen to be produced must be vaporized, which tends to reduce the low pressure.

Ce dernier inconvénient est supprimé dans l'installation de la figure 3 qui permet de produire l'oxygène impur sous une pression élevée, et qui diffère de la précédente par les points suivants :This last drawback is eliminated in the installation of FIG. 3 which makes it possible to produce impure oxygen under high pressure, and which differs from the previous one in the following points:

D'une part, l'oxygène impur est soutiré sous forme liquide de la cuve de la colonne BP, puis est amené par une pompe 23 à la pression de production désirée, puis vaporisé et réchauffé sous cette pression dans la ligne d'échange 4 avant d'être évacué de l'installation via la conduite 24.On the one hand, the impure oxygen is withdrawn in liquid form from the tank of the LP column, then is brought by a pump 23 to the desired production pressure, then vaporized and heated under this pressure in the exchange line 4 before being evacuated from the installation via line 24.

D'autre part, pour compenser la perte de reflux dans la colonne MP résultant du soutirage d'oxygène liquide en cuve de la colonne BP, il est prévu un cycle azote, dit cycle de soutien de rectification, qui est utilisé en même temps pour assurer la vaporisation de l'oxygène impur : une partie de l'azote produit en tête de la colonne 3 (laquelle, dans ce cas, possède en tête un "minaret" 30 qui est alimenté à son sommet par de l'azote liquide pur provenant du vaporiseur-condenseur supérieur 9 et qui, par suite, produit de l'azote pur sous la basse pression) est, après réchauffement dans la ligne d'échange, comprimée par un compresseur 31 à la moyenne pression. Cet azote moyenne pression, réuni à un courant d'azote moyenne pression prélevé sur la conduite 16, est comprimé de nouveau par un compresseur 33 à une pression de vaporisation de l'oxygène impur comprimé par la pompe 23, liquéfié dans la ligne d'échange puis, après détente dans une vanne de détente 34, introduit en reflux en tête de la colonne MP.On the other hand, to compensate for the loss of reflux in the MP column resulting from the withdrawal of liquid oxygen from the bottom of the LP column, a nitrogen cycle is provided, known as the rectification support cycle, which is used at the same time to ensure the vaporization of impure oxygen: part of the nitrogen produced at the head of column 3 (which, in this case, has at the head a "minaret" 30 which is supplied at its top with pure liquid nitrogen coming from the upper evaporator-condenser 9 and which, consequently, produces pure nitrogen under low pressure) is, after heating in the exchange line, compressed by a compressor 31 at medium pressure. This medium pressure nitrogen, combined with a current of medium pressure nitrogen taken from the line 16, is compressed again by a compressor 33 to a vaporization pressure of the impure oxygen compressed by the pump 23, liquefied in the line of exchange then, after expansion in an expansion valve 34, introduced under reflux at the head of the column MP.

L'installation de la figure 4 comporte également une colonne BP 3 à minaret 30. Toutefois, contrairement au cas précédent, c'est de l'air haute pression, surpressé à une pression de vaporisation de l'oxygène impur par un surpresseur 35, qui assure la vaporisation de l'oxygène impur dans la ligne d'échange 4. Dans cet exemple, cet air est, après liquéfaction et détente dans une vanne de détente 36 et dans la vanne de détente 13, réparti entre les deux colonnes 2 et 3. Par conséquent, le compresseur 33 et la vanne de détente 34 de la figure 3 sont supprimés.The installation of FIG. 4 also includes a BP 3 column with a minaret 30. However, unlike the previous case, it is high pressure air, boosted to a vaporization pressure of impure oxygen by a booster 35, which ensures the vaporization of the impure oxygen in the exchange line 4. In this example, this air is, after liquefaction and expansion in an expansion valve 36 and in the expansion valve 13, distributed between the two columns 2 and 3. Consequently, the compressor 33 and the expansion valve 34 of FIG. 3 are eliminated.

De plus, l'azote issu du compresseur 31, comprimé à une pression supérieure à la moyenne pression, alimente sous forme gazeuse, après refroidissement dans la ligne d'échange, le vaporiseur-condenseur inférieur 8, et l'azote liquide résultant est, après détente dans une vanne de détente 37, réuni à l'azote liquide moyenne pression issu du vaporiseur-condenseur supérieur 9. Ceci présente l'avantage de permettre un réglage de la température de la cuve de la colonne BP, et donc de la pression de cette colonne, par réglage de la pression de l'azote alimentant le vaporiseur-condenseur 8. Cette pression d'azote peut être choisie entre la moyenne pression et la pression pour laquelle l'azote se condense au bout froid de la ligne d'échange.In addition, the nitrogen from the compressor 31, compressed to a pressure higher than the medium pressure, feeds in gaseous form, after cooling in the exchange line, the lower vaporizer-condenser 8, and the resulting liquid nitrogen is, after expansion in an expansion valve 37, combined with medium pressure liquid nitrogen from the upper evaporator-condenser 9. This has the advantage of allowing the temperature of the tank of the LP column to be adjusted, and therefore the pressure of this column, by adjusting the pressure of the nitrogen supplying the vaporizer-condenser 8. This nitrogen pressure can be chosen between medium pressure and the pressure for which the nitrogen condenses at the cold end of the line exchange.

Claims (11)

Procédé de production d'oxygène par distillation d'air dans une installation de distillation d'air à double colonne (1), la double colonne comprenant une colonne moyenne pression (2) et une colonne basse pression (3), dans lequel : - on refroidit un débit d'air et on l'envoie à la colonne moyenne pression (2) ; - on sépare l'air par distillation dans la colonne moyenne pression en un fluide enrichi en oxygène et un fluide enrichi en azote ; - on envoie lesdits fluides à la colonne basse pression ; - on soutire un liquide riche en oxygène de la colonne basse pression et on le vaporise ; - on soutire un gaz enrichi en azote de la colonne basse pression, caractérisé en ce que : - on comprime le gaz enrichi en azote soutiré de la colonne basse pression, on le refroidit et on envoie le fluide refroidi à la colonne moyenne pression ; - on vaporise le liquide riche en oxygène par échange de chaleur avec le débit d'air. Method for producing oxygen by air distillation in a double column air distillation installation (1), the double column comprising a medium pressure column (2) and a low pressure column (3), in which: - an air flow is cooled and sent to the medium pressure column (2); - The air is separated by distillation in the medium pressure column into a fluid enriched in oxygen and a fluid enriched in nitrogen; - said fluids are sent to the low pressure column; - a liquid rich in oxygen is drawn off from the low pressure column and it is vaporized; - a gas enriched in nitrogen is drawn off from the low pressure column, characterized in that: - Compresses the nitrogen-enriched gas withdrawn from the low pressure column, it is cooled and the cooled fluid is sent to the medium pressure column; - the oxygen-rich liquid is vaporized by heat exchange with the air flow. Procédé selon la revendication 1 dans lequel on vaporise le liquide en oxygène par échange de chaleur avec le gaz comprimé enrichi en azote.The method of claim 1 wherein the liquid is vaporized with oxygen by heat exchange with the compressed gas enriched in nitrogen. Procédé selon la revendication 1 ou 2, dans lequel le gaz enrichi en azote est réchauffé avant d'être comprimé.The method of claim 1 or 2, wherein the nitrogen-enriched gas is heated before being compressed. Procédé selon la revendication 1, 2 ou 3, dans lequel on vaporise le liquide riche en oxygène contre une partie de la vapeur enrichie en azote qui a été comprimée.A method according to claim 1, 2 or 3, in which the oxygen-rich liquid is vaporized against part of the nitrogen-enriched vapor which has been compressed. Procédé selon l'une des revendications précédentes dans lequel le gaz enrichi en azote se liquéfie par échange de chaleur avec le liquide riche en oxygène.Method according to one of the preceding claims, in which the nitrogen-enriched gas liquefies by heat exchange with the oxygen-rich liquid. Procédé selon l'une des revendications 1 à 4 dans lequel le gaz enrichi en azote comprimé et refroidi est envoyé à un condenseur-vaporiseur (8) de la colonne basse pression où il se condense pour former du reflux.Method according to one of claims 1 to 4 wherein the gas enriched in compressed and cooled nitrogen is sent to a condenser-vaporizer (8) of the low pressure column where it condenses to form reflux. Appareil de production de produit gazeux comprenant : - un compresseur d'air ; - un échangeur de chaleur (4) ; - une colonne moyenne pression (2) ; - une colonne basse pression (3) ; - des moyens pour envoyer de l'air à la colonne moyenne pression via l'échangeur de chaleur ; - des moyens pour soutirer un liquide de la cuve de la colonne basse pression et pour envoyer le liquide à l'échangeur de chaleur,    caractérisé en ce qu'il comprend un premier compresseur d'azote (31), des moyens pour envoyer un fluide enrichi en azote de la colonne basse pression au premier compresseur d'azote, du premier compresseur d'azote au moyen de refroidissement (4) du moyen de refroidissement (4) directement ou indirectement à la colonne moyenne pression.Apparatus for producing gaseous product comprising: - an air compressor; - a heat exchanger (4); - a medium pressure column (2); - a low pressure column (3); - Means for sending air to the medium pressure column via the heat exchanger; means for withdrawing a liquid from the tank of the low pressure column and for sending the liquid to the heat exchanger, characterized in that it comprises a first nitrogen compressor (31), means for sending a nitrogen-enriched fluid from the low pressure column to the first nitrogen compressor, from the first nitrogen compressor to the cooling means (4 ) cooling means (4) directly or indirectly to the medium pressure column. Appareil selon la revendication 7 comprenant des moyens pour pressuriser le liquide avant de l'envoyer à l'échangeur de chaleur (4).Apparatus according to claim 7 comprising means for pressurizing the liquid before sending it to the heat exchanger (4). Appareil selon l'une des revendications 7 et 8 dans lequel on envoie le fluide enrichi en azote du premier compresseur d'azote à un moyen de refroidissement (4) constitué par l'échangeur de chaleur.Apparatus according to one of claims 7 and 8 wherein the nitrogen-enriched fluid is sent from the first nitrogen compressor to a cooling means (4) constituted by the heat exchanger. Appareil selon l'une des revendications 7, 8 ou 9 comprenant des moyens pour comprimer un gaz de tête de la colonne moyenne pression (2) et des moyens pour envoyer le gaz de tête comprimé à l'échangeur de chaleur (4).Apparatus according to one of claims 7, 8 or 9 comprising means for compressing an overhead gas from the medium pressure column (2) and means for sending the compressed overhead gas to the heat exchanger (4). Appareil selon l'une des revendications 7, 8 ou 9 comprenant des moyens pour envoyer le fluide comprimé enrichi en azote de l'échangeur de chaleur à un condenseur de cuve (8) de la colonne basse pression et ensuite à la colonne moyenne pression (2).Apparatus according to one of claims 7, 8 or 9 comprising means for sending the compressed nitrogen-enriched fluid from the heat exchanger to a tank condenser (8) of the low pressure column and then to the medium pressure column ( 2).
EP96200235A 1991-12-18 1992-12-09 Process and plant for air separation Expired - Lifetime EP0713069B1 (en)

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FR9115705A FR2685459B1 (en) 1991-12-18 1991-12-18 PROCESS AND PLANT FOR PRODUCING IMPURATED OXYGEN.
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EP92403330A EP0547946B2 (en) 1991-12-18 1992-12-09 Process for the production of impure oxygen

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EP0834712A2 (en) * 1996-10-01 1998-04-08 Air Products And Chemicals, Inc. Process to produce high pressure nitrogen using a higher pressure column and one or more lower pressure columns
EP1099922A2 (en) * 1999-11-09 2001-05-16 Air Products And Chemicals, Inc. Process for the production of intermediate pressure oxygen

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ES2092661T3 (en) 1996-12-01
US5392609A (en) 1995-02-28
EP0547946B1 (en) 1996-10-09
EP0547946B2 (en) 2000-03-22
ES2145967T3 (en) 2000-07-16
CN1088301A (en) 1994-06-22
FR2685459B1 (en) 1994-02-11
DE69214409D1 (en) 1996-11-14
BR9205050A (en) 1993-08-10
AU3022192A (en) 1993-06-24
CN1068428C (en) 2001-07-11
DE69230975T2 (en) 2000-10-05
DE69214409T3 (en) 2000-07-13
EP0713069B1 (en) 2000-04-26
EP0547946A1 (en) 1993-06-23
FR2685459A1 (en) 1993-06-25
CA2085561A1 (en) 1993-06-19
DE69214409T2 (en) 1997-05-22
AU654601B2 (en) 1994-11-10

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