EP1690053A1 - Method and device for separating air by cryogenic distillation - Google Patents

Method and device for separating air by cryogenic distillation

Info

Publication number
EP1690053A1
EP1690053A1 EP04805780A EP04805780A EP1690053A1 EP 1690053 A1 EP1690053 A1 EP 1690053A1 EP 04805780 A EP04805780 A EP 04805780A EP 04805780 A EP04805780 A EP 04805780A EP 1690053 A1 EP1690053 A1 EP 1690053A1
Authority
EP
European Patent Office
Prior art keywords
air
pressure column
column
low pressure
medium pressure
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.)
Withdrawn
Application number
EP04805780A
Other languages
German (de)
French (fr)
Inventor
Hervé Le Bihan
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.)
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Original Assignee
Air Liquide SA
LAir Liquide SA a Directoire et Conseil de Surveillance pour lEtude et lExploitation des Procedes Georges Claude
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 Liquide SA, LAir Liquide SA a Directoire et Conseil de Surveillance pour lEtude et lExploitation des Procedes Georges Claude filed Critical Air Liquide SA
Publication of EP1690053A1 publication Critical patent/EP1690053A1/en
Withdrawn legal-status Critical Current

Links

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
    • F25J3/04151—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 process using a mixing column for the production of impure gaseous oxygen.
  • It is known from EP-A-0538118 to use a double column and a mixing column to produce impure oxygen with a dedicated air su ⁇ ressor to compress the air to the pressure of the mixing column.
  • the present invention aims to reduce the investment costs of such an apparatus.
  • an air separation process is provided 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, it is cooled in an exchange line and a first part of the air is sent to the tank of the mixing column ii) a second part of the air is sent to the medium pressure column where it separates 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-rich liquid is sent from the low pressure column to the head of the mixing column v) on draw at least one liquid flow from the medium or low pressure column vi) press the second part of the air in a su ⁇ ressor, cool it in the exchange line, divide it into a first fraction and a second fr action vii) the first fraction of the air in the exchange line is cooled, at least partially liquefied and sent to the medium pressure column and / or the low pressure column viii) the second fraction is expanded the
  • the liquid withdrawn from the medium or low pressure column is a final 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 intended for distillation is compressed to between 8 and 20 bar abs.
  • - between 40 and 90% of the air intended for distillation is overpressed.
  • the su l'airressed air is su ⁇ ressed at between 12 and 30 bar abs.
  • an air separation installation is provided 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 part of the compressed air from the air to the mixing column, means for sending another part of the compressed air to the su ⁇ ressor, means for sending a fraction of the compressed air at the Claude turbine and to send the expanded air to the medium pressure column, means for sending the rest of the compressed air to the medium pressure and / or low pressure column after liquefaction and expansion and means for withdrawing from the minus a liquid from the medium pressure column and / or from the low pressure column as final product.
  • the booster can 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 intended to produce impure oxygen Ol, for example having a purity of 80 to 97% and preferably 85 to 95% under a determined pressure P clearly different from 6 x 10 5 Pa abs., For example under 8 to 20 x 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 column pressure 4 and a main condenser-vaporizer 5, and a column of mixing 6.
  • the mixing column 6 and the low pressure column 4 are integrated into a single structure.
  • the medium pressure column 3 forms a separate structure and is surmounted by the condenser-vaporizer 5, as described in EP-A-1978212.
  • Columns 3 and 4 typically operate at approximately 6 x 10 5 Pa and approximately 1 x 10 5 Pa respectively.
  • a mixing column is a column which has the same structure as a distillation column but which is used to mix in a manner close to reversibility a relatively volatile gas, introduced at its base, and a less volatile liquid, introduced at its top.
  • Such a mixture produces refrigerating energy and therefore makes it possible to reduce the energy consumption linked to distillation.
  • this mixture is used, moreover, to directly produce impure oxygen under the pressure P, as will be described below.
  • the air to be separated by distillation is compressed to 15 x 10 5 Pa (generally between
  • Liquid 26 is withdrawn from the condenser 5, carried by a pump 13 at a pressure P1, slightly higher than the above-mentioned pressure P for take into account pressure losses (P1-P less than 1 x 10 5 Pa), and partly introduced at the top of column 6. Part 27 of the liquid oxygen can be sent to storage. Auxiliary air from compressor C01, compressed to a pressure well above medium pressure and partially cooled in the exchange line 1, is introduced at the base of the mixing column 6.
  • FIG. 1 also shows auxiliary heat exchangers 19, 20 ensuring the recovery of the cold available in the fluids circulating in the installation.
  • the double column composed of columns 3 and 4 can form a single structure in a conventional manner, the mixing column 6 forming a separate structure.
  • a flow of pressurized liquid oxygen and / or a flow of pressurized liquid nitrogen can vaporize in the exchange line 1 or in a dedicated vaporizer.

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

Procédé et appareil de séparation d'air par distillation cryogénique Method and apparatus for air separation by cryogenic distillation
La présente invention est relative à un procédé et à un appareil de séparation d'air par distillation cryogénique. En particulier il concerne un procédé de séparation d'air utilisant une colonne de mélange pour la production d'oxygène gazeux impur. Il est connu de EP-A-0538118 d'utiliser une double colonne et une colonne de mélange pour produire de l'oxygène impur avec un suφresseur dédié d'air pour comprimer l'air à la pression de la colonne de mélange. La présente invention vise à réduire les coûts d'investissement d'un tel appareil. Selon un objet de l'invention, il est prévu un procédé de séparation d'air par distillation cryogénique dans une installation comprenant une colonne moyenne pression, une colonne basse pression et une colonne de mélange dans lequel i) on comprime de l'air dans un compresseur, on le refroidit dans une ligne d'échange et on envoie une première partie de l'air à la cuve de la colonne de mélange ii) on envoie une deuxième partie de l'air à la colonne moyenne pression où il se sépare iii) on envoie un liquide enrichi en oxygène et un liquide enrichi en azote de la colonne moyenne pression vers la colonne basse pression iv) on envoie un liquide riche en oxygène de la colonne basse pression vers la tête de la colonne de mélange v) on soutire au moins un débit de liquide de la colonne moyenne ou basse pression vi) on surpresse la deuxième partie de l'air dans un suφresseur, on le refroidit dans la ligne d'échange, on la divise en une première fraction et une deuxième fraction vii) on refroidit la première fraction de l'air dans la ligne d'échange, on le liquéfie au moins partiellement et on l'envoie à la colonne moyenne pression et/ou la colonne basse pression viii) on détend la deuxième fraction de l'air dans une turbine Claude et on l'envoie à la colonne moyenne pression et ix) on soutire un débit riche en oxygène de la colonne de mélange et on le réchauffe dans la ligne d'échange. Selon d'autres aspects facultatifs : - le liquide soutiré de la colonne moyenne ou basse pression est un produit final - le surpresseur est couplé à la turbine Claude. - le surpresseur est un surpresseur froid. - la colonne de mélange opère à entre 8 et 20 bars abs. - tout l'air destiné à la distillation est comprimé à entre 8 et 20 bars abs. - entre 40 et 90 % de l'air destiné à la distillation est surpressé. - l'air suφressé est suφressé à entre 12 et 30 bars abs. Selon un autre aspect de l'invention, il est prévu une installation de séparation d'air par distillation cryogénique dans un appareil comprenant une colonne moyenne pression, une colonne basse pression et une colonne de mélange, une turbine Claude, un surpresseur, des moyens pour comprimer de l'air, des moyens pour envoyer une partie de l'air comprimé de l'air à la colonne de mélange, des moyens pour envoyer une autre partie de l'air comprimé au suφresseur, des moyens pour envoyer une fraction de l'air surpressé à la turbine Claude et pour envoyer l'air détendu à la colonne moyenne pression, des moyens pour envoyer le reste de Pair suφressé à la colonne moyenne pression et/ou basse pression après liquéfaction et détente et des moyens pour soutirer au moins un liquide de la colonne moyenne pression et/ou de la colonne basse pression comme produit final. Le surpresseur peut être couplé à la turbine Claude. Un exemple de mise en œuvre de l'invention vont maintenant être décrits en regard du dessin annexé, sur lequel la figure 1 représente schématiquement un mode de réalisation de l'installation de distillation d'air conforme à l'invention. L'installation de distillation d'air représentée à la figure 1 est destinée à produire de l'oxygène impur Ol, par exemple ayant une pureté de 80 à 97 % et de préférence de 85 à 95 % sous une pression déterminée P nettement différente de 6 x 105 Pa abs., par exemple sous 8 à 20 x 105 Pa. L'installation comprend essentiellement une ligne d'échange thermique 1, une double colonne de distillation comprenant elle-même une colonne moyenne pression 3, une colonne basse pression 4 et un condenseur-vaporiseur principal 5, et une colonne de mélange 6. La colonne de mélange 6 et la colonne basse pression 4 sont intégrées dans une seule structure. La colonne moyenne pression 3 forme une structure à part et est surmontée du condenseur-vaporiseur 5, comme décrit dans EP-A-1978212. Les colonnes 3 et 4 fonctionnent typiquement sous environ 6 x 105 Pa et environ 1 x 105 Pa respectivement. Comme expliqué en détail dans le document US-A-4,022,030, une colonne de mélange est une colonne qui a la même structure qu'une colonne de distillation mais qui est utilisée pour mélanger de façon proche de la réversibilité un gaz relativement volatil, introduit à sa base, et un liquide moins volatil, introduit à son sommet. Un tel mélange produit de l'énergie frigorifique et permet donc de réduire la consommation d'énergie liée à la distillation. Dans le cas présent, ce mélange est mis à profit, en outre, pour produire directement de l'oxygène impur sous la pression P, comme cela sera décrit ci-dessous. L'air à séparer par distillation est comprimé à 15 x 105 Pa (en général entreThe present invention relates to a method and an apparatus for separating air by cryogenic distillation. In particular it relates to an air separation process using a mixing column for the production of impure gaseous oxygen. It is known from EP-A-0538118 to use a double column and a mixing column to produce impure oxygen with a dedicated air suφressor to compress the air to the pressure of the mixing column. The present invention aims to reduce the investment costs of such an apparatus. According to an object of the invention, an air separation process is provided 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, it is cooled in an exchange line and a first part of the air is sent to the tank of the mixing column ii) a second part of the air is sent to the medium pressure column where it separates 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-rich liquid is sent from the low pressure column to the head of the mixing column v) on draw at least one liquid flow from the medium or low pressure column vi) press the second part of the air in a suφressor, cool it in the exchange line, divide it into a first fraction and a second fr action vii) the first fraction of the air in the exchange line is cooled, at least partially liquefied and sent to the medium pressure column and / or the low pressure column viii) the second fraction is expanded the air in a Claude turbine and we send it to the medium pressure column and ix) an oxygen-rich flow rate is drawn off from the mixing column and it is heated in the exchange line. According to other optional aspects: - the liquid withdrawn from the medium or low pressure column is a final 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 intended for distillation is compressed to between 8 and 20 bar abs. - between 40 and 90% of the air intended for distillation is overpressed. - the su l'airressed air is suφressed at between 12 and 30 bar abs. According to another aspect of the invention, an air separation installation is provided 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 part of the compressed air from the air to the mixing column, means for sending another part of the compressed air to the suφressor, means for sending a fraction of the compressed air at the Claude turbine and to send the expanded air to the medium pressure column, means for sending the rest of the compressed air to the medium pressure and / or low pressure column after liquefaction and expansion and means for withdrawing from the minus a liquid from the medium pressure column and / or from the low pressure column as final product. The booster can be coupled to the Claude turbine. An example of implementation of the invention will now be described with reference to the accompanying drawing, 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 intended to produce impure oxygen Ol, for example having a purity of 80 to 97% and preferably 85 to 95% under a determined pressure P clearly different from 6 x 10 5 Pa abs., For example under 8 to 20 x 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 column pressure 4 and a main condenser-vaporizer 5, and a column of mixing 6. The mixing column 6 and the low pressure column 4 are integrated into a single structure. The medium pressure column 3 forms a separate structure and is surmounted by the condenser-vaporizer 5, as described in EP-A-1978212. Columns 3 and 4 typically operate at approximately 6 x 10 5 Pa and approximately 1 x 10 5 Pa respectively. As explained in detail in document US-A-4,022,030, a mixing column is a column which has the same structure as a distillation column but which is used to mix in a manner close to reversibility a relatively volatile gas, introduced at its base, and a less volatile liquid, introduced at its top. Such a mixture produces refrigerating energy and therefore makes it possible to reduce the energy consumption linked to distillation. In the present case, this mixture is used, moreover, to directly produce impure oxygen under the pressure P, as will be described below. The air to be separated by distillation is compressed to 15 x 10 5 Pa (generally between
8 et 20 x 105 Pa) dans un compresseur C01 et convenablement épuré, est divisé en deux. Une partie de cet air constituant entre 40 et 90% de l'air est suφressée dans un suφresseur 8 jusqu'à une pression d'entre 12 et 30 x 105 Pa, refroidie dans la ligne d'échange 1 et divisé en deux fractions. Une fraction poursuit son refroidissement dans la ligne d'échange 1 où elle se liquéfie au moins partiellement avant d'être introduite à la colonne moyenne pression 3 par une conduite 7. Une partie ou tout cet air liquéfié peut être envoyé à la colonne basse pression 4. Une autre fraction de l'air surpressé en 8 puis refroidie, est détendue à la moyenne pression dans une turbine Claude 9 couplée au suφresseur 8, puis envoyé en cuve de la colonne moyenne pression 3 sous forme gazeuse, quelques plateaux en dessous du point d'arrivée de la conduite 7. Du « liquide riche » (air enrichi en oxygène), prélevé en cuve de la colonne 3 est, après détente dans une vanne de détente 10, introduit dans la colonne 4. Du « liquide pauvre » (azote impur) 11 prélevé en haut de la colonne 3 est, après détente dans une vanne de détente 12, introduit au sommet de la colonne 4, et le gaz produit en tête de la colonne 4 constituant le gaz résiduaire NI de l'installation est réchauffé dans la ligne d'échange 1 et évacué de l'installation. De l'oxygène liquide, plus ou moins pur suivant le réglage de la double colonne, est soutiré en cuve de la colonne 4. envoyé par la conduite 24 au condenseur-vaporiseur 5 où il se vaporise partiellement formant un gaz 25 qui est renvoyé à la colonne basse pression 4. Du liquide 26 est soutiré du condenseur 5, porté par une pompe 13 à une pression P1, légèrement supérieure à la pression P précitée pour tenir compte des pertes de charge (P1-P inférieur à 1 x 105 Pa), et en partie introduit au sommet de la colonne 6. Une partie 27 de l'oxygène liquide peut être envoyé à un stockage. De l'air auxiliaire provenant du compresseur C01, comprimé à une pression largement au-dessus de la moyenne pression et refroidi partiellement dans la ligne d'échange 1 , est introduit à la base de la colonne de mélange 6. De cette dernière sont soutirés trois courants de fluide : à sa base, du liquide voisin du liquide riche et réuni à ce dernier via une conduite 15 munie d'une vanne de détente 15A ; en un point intermédiaire, un mélange essentiellement constitué d'oxygène et d'azote, qui est renvoyé en un point intermédiaire de la colonne basse pression 4 via une conduite 16 munie d'une vanne de détente 17 ; et à son sommet de l'oxygène impur, qui, après réchauffement dans la ligne d'échange thermique, est évacué, sensiblement à la pression P, de l'installation via une conduite 18 en tant que gaz de production Ol. Un débit d'azote liquide est soutiré en tête de la colonne moyenne pression 3 comme produit final. On a également représenté sur la figure 1 des échangeurs de chaleur auxiliaires 19, 20 assurant la récupération du froid disponible dans les fluides en circulation dans l'installation. Il sera aisément compris que la double colonne composée des colonnes 3 et 4 peut former une seule structure de façon classique, la colonne de mélange 6 formant une structure à part. Eventuellement un débit d'oxygène liquide pressurisé et/ou un débit d'azote liquide pressurisé peut se vaporiser dans la ligne d'échange 1 ou dans un vaporiseur dédié. 8 and 20 x 10 5 Pa) in a compressor C01 and suitably purified, is divided into two. A part of this air constituting between 40 and 90% of the air is suφressé in a suφresseur 8 until a pressure of between 12 and 30 x 10 5 Pa, cooled in the exchange line 1 and divided into two fractions . A fraction continues to cool in the exchange line 1 where it at least partially liquefies before being introduced into the medium pressure column 3 via a pipe 7. A portion or all of this liquefied air can be sent to the low pressure column 4. Another fraction of the air boosted at 8 then cooled, is expanded to medium pressure in a Claude 9 turbine coupled to the suφressor 8, then sent to the bottom of the medium pressure column 3 in gaseous form, a few trays below the end point of the pipe 7. “Rich liquid” (oxygen-enriched air), taken from the tank of column 3 is, after expansion in an expansion valve 10, introduced into column 4. “Lean liquid” (impure nitrogen) 11 taken from the top of column 3 is, after expansion in an expansion valve 12, introduced at the top of column 4, and the gas produced at the top of column 4 constituting the residual gas NI of the installation East heated in exchange line 1 and evacuated from the installation. Liquid oxygen, more or less pure depending on the setting of the double column, is drawn off in the tank of column 4. sent via line 24 to condenser-vaporizer 5 where it partially vaporizes forming a gas 25 which is returned to the low pressure column 4. Liquid 26 is withdrawn from the condenser 5, carried by a pump 13 at a pressure P1, slightly higher than the above-mentioned pressure P for take into account pressure losses (P1-P less than 1 x 10 5 Pa), and partly introduced at the top of column 6. Part 27 of the liquid oxygen can be sent to storage. Auxiliary air from compressor C01, compressed to a pressure well above medium pressure and partially cooled in the exchange line 1, is introduced at the base of the mixing column 6. From this latter are drawn off three fluid streams: at its base, liquid close to the rich liquid and joined to the latter via a pipe 15 provided with an expansion valve 15A; at an intermediate point, a mixture essentially consisting of oxygen and nitrogen, which is returned to an intermediate point of the low pressure column 4 via a pipe 16 provided with an expansion valve 17; and at its apex impure oxygen, which, after heating in the heat exchange line, is evacuated, substantially at pressure P, from the installation via a pipe 18 as production gas Ol. A flow of liquid nitrogen is drawn off at the head of the medium pressure column 3 as final product. FIG. 1 also shows auxiliary heat exchangers 19, 20 ensuring the recovery of the cold available in the fluids circulating in the installation. It will be readily understood that the double column composed of columns 3 and 4 can form a single structure in a conventional manner, the mixing column 6 forming a separate structure. Optionally, a flow of pressurized liquid oxygen and / or a flow of pressurized liquid nitrogen can vaporize in the exchange line 1 or in a dedicated vaporizer.

Claims

REVENDICATIONS
1. Procédé de séparation d'air par distillation cryogénique dans une installation comprenant une colonne moyenne pression (3), une colonne basse pression (4) et une colonne de mélange (6) dans lequel i) on comprime de l'air dans un compresseur (C01), on le refroidit dans une ligne d'échange (1) et on envoie une première partie (2) de l'air à la cuve de la colonne de mélange ii) on envoie une deuxième partie de l'air à la colonne moyenne pression où il se sépare iii) on envoie un liquide enrichi en oxygène (19) et un liquide enrichi en azote (11) de la colonne moyenne pression vers la colonne basse pression iv) on envoie un liquide riche en oxygène (26) de la colonne basse pression vers la tête de la colonne de mélange v) on soutire au moins un débit de liquide (29) de la colonne moyenne ou basse pression vi) on surpresse la deuxième partie de l'air dans un surpresseur (8), on le refroidit dans la ligne d'échange, on la divise en une première fraction et une deuxième fraction vii) on refroidit la première fraction de l'air dans la ligne d'échange, on le liquéfie au moins partiellement et on l'envoie à la colonne moyenne pression et/ou la colonne basse pression viii) on détend la deuxième fraction de l'air dans une turbine Claude (9) et on l'envoie à la colonne moyenne pression et ix) on soutire un débit riche en oxygène (18) de la colonne de mélange et on le réchauffe dans la ligne d'échange.1. Process for the separation of air by cryogenic distillation in an installation comprising a medium pressure column (3), a low pressure column (4) and a mixing column (6) in which i) air is compressed in a compressor (C01), it is cooled in an exchange line (1) and a first part (2) of air is sent to the tank of the mixing column ii) a second part of the air is sent to the medium pressure column where it separates iii) an oxygen-enriched liquid (19) and a nitrogen-enriched liquid (11) are sent from the medium pressure column to the low pressure column iv) an oxygen-rich liquid is sent (26 ) from the low pressure column to the head of the mixing column v) at least one liquid flow (29) is withdrawn from the medium or low pressure column vi) the second part of the air is boosted in a booster (8 ), it is cooled in the exchange line, it is divided into a first fraction and a second fraction vii) the first fraction of the air in the exchange line is cooled, at least partially liquefied and sent to the medium pressure column and / or the low pressure column viii) the second fraction is expanded air in a Claude turbine (9) and it is sent to the medium pressure column and ix) an oxygen-rich flow (18) is drawn off from the mixing column and it is heated in the exchange line.
2. Procédé selon la revendication 1 dans lequel le liquide (27, 29) soutiré de la colonne moyenne ou basse pression est un produit final.2. Method according to claim 1 wherein the liquid (27, 29) withdrawn from the medium or low pressure column is a final product.
3. Procédé selon la revendication 1 ou 2 dans lequel le surpresseur (8) est couplé à la turbine Claude (9). 3. Method according to claim 1 or 2 wherein the booster (8) is coupled to the Claude turbine (9).
4. Procédé selon la revendication 1 , 2 ou 3 dans lequel le surpresseur est un suφresseur froid.4. Method according to claim 1, 2 or 3 wherein the booster is a cold suφresseur.
5. Procédé selon l'une des revendications précédentes dans lequel la colonne de mélange (6) opère à entre 8 et 20 bars abs.5. Method according to one of the preceding claims wherein the mixing column (6) operates at between 8 and 20 bar abs.
6. Procédé selon l'une des revendications précédentes dans lequel tout l'air destiné à la distillation est comprimé à entre 8 et 20 bars abs.6. Method according to one of the preceding claims in which all the air intended for distillation is compressed to between 8 and 20 bar abs.
7. Procédé selon l'une des revendications précédentes dans lequel entre 40 et 90 % de l'air destiné à la distillation est surpressé.7. Method according to one of the preceding claims wherein between 40 and 90% of the air intended for distillation is overpressed.
8. Procédé selon l'une des revendications précédentes dans lequel l'air suφressé est suφressé à entre 12 et 30 bars abs.8. Method according to one of the preceding claims wherein the suφressé air is suφressé at between 12 and 30 bar abs.
9. Installation de séparation d'air par distillation cryogénique dans un appareil comprenant une colonne moyenne pression (3), une colonne basse pression (4) et une colonne de mélange (6), une turbine Claude (9), un suφresseur (8), des moyens pour comprimer de l'air (C01 ), des moyens (2) pour envoyer une partie de l'air comprimé de l'air à la colonne de mélange, des moyens pour envoyer une autre partie de l'air comprimé au surpresseur, des moyens pour envoyer une fraction de l'air surpressé à la turbine Claude et pour envoyer l'air détendu à la colonne moyenne pression, des moyens pour envoyer le reste de l'air surpressé à la colonne moyenne pression et/ou basse pression après liquéfaction et détente et des moyens pour soutirer au moins un liquide (27, 29) de la colonne moyenne pression et/ou de la colonne basse pression comme produit final.9. Installation for air separation by cryogenic distillation in an apparatus comprising a medium pressure column (3), a low pressure column (4) and a mixing column (6), a Claude turbine (9), a suφressor (8 ), means for compressing air (C01), means (2) for sending part of the compressed air from the air to the mixing column, means for sending another part for 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 column and / or low pressure after liquefaction and expansion and means for withdrawing at least one liquid (27, 29) from the medium pressure column and / or from the low pressure column as final product.
10. Installation selon la revendication 9 dans lequel le surpresseur (8) est couplé à la turbine Claude (9). 10. Installation according to claim 9 wherein the booster (8) is coupled to the Claude turbine (9).
EP04805780A 2003-11-04 2004-10-26 Method and device for separating air by cryogenic distillation Withdrawn EP1690053A1 (en)

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

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US20070137248A1 (en) 2007-06-21
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FR2861841A1 (en) 2005-05-06
CN1871485A (en) 2006-11-29
FR2861841B1 (en) 2006-06-30

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