FR2825454A3 - Separation of air, especially to produce small quantities of pure nitrogen, uses cryogenic distillation in a double column unit with an auxiliary column producing purer nitrogen from the other columns' nitrogen-rich discharges - Google Patents

Separation of air, especially to produce small quantities of pure nitrogen, uses cryogenic distillation in a double column unit with an auxiliary column producing purer nitrogen from the other columns' nitrogen-rich discharges Download PDF

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Publication number
FR2825454A3
FR2825454A3 FR0202347A FR0202347A FR2825454A3 FR 2825454 A3 FR2825454 A3 FR 2825454A3 FR 0202347 A FR0202347 A FR 0202347A FR 0202347 A FR0202347 A FR 0202347A FR 2825454 A3 FR2825454 A3 FR 2825454A3
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France
Prior art keywords
column
nitrogen
enriched
pressure column
auxiliary
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FR0202347A
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French (fr)
Inventor
Frederic Judas
Frederic Staine
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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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Priority to FR0202347A priority Critical patent/FR2825454A3/en
Publication of FR2825454A3 publication Critical patent/FR2825454A3/en
Pending legal-status Critical Current

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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
    • F25J3/04187—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
    • F25J3/042—Division of the main heat exchange line in consecutive sections having different functions having an intermediate feed connection
    • 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
    • F25J3/04084—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 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
    • F25J3/04006—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
    • F25J3/04406—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using a dual pressure main column system
    • F25J3/04412—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using a dual pressure main column system in a classical double column flowsheet, i.e. with thermal coupling by a main reboiler-condenser in the bottom of low pressure respectively top of high pressure column
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04763—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.
    • F25J3/04878—Side by side arrangement of multiple vessels in a main column system, wherein the vessels are normally mounted one upon the other or forming different sections of the same 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
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/32—Processes or apparatus using separation by rectification using a side column fed by a stream from the 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
    • 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

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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

Separation of air uses cryogenic distillation in a double column unit with an auxiliary column producing purer nitrogen from the other columns' nitrogen-rich discharges. Only the fluid enriched in nitrogen (15) is supplied to the auxiliary column (N2). There are no means of exchanging mass or heat below the point of entry of a fluid enriched in nitrogen into the auxiliary column. Compressed and purified air is sent to the medium pressure column (MP) to produce a fluid enriched in oxygen (9) and fluids enriched in nitrogen (15, 27). The fluid enriched in nitrogen (15) is sent to the auxiliary column (N2) where it is separated to form a flow rich in nitrogen (21) at the top of the column. At least one of the fluids enriched in nitrogen is at least partially condensed in a reboiler (19) in the low pressure column (BP) and part of the nitrogen-enriched condensate (27) is sent to the top of the low pressure column. A flow rich in oxygen (33) is extracted from the base of the low pressure column and a flow rich in nitrogen (25) is extracted from the top of the low pressure column. The auxiliary column has a head condenser (22) and a liquid enriched in oxygen (11) is sent from the condenser to the base of the medium pressure column after expansion. The liquid rich in oxygen is partially vaporized in the heat condenser and at least some of the vaporized liquid is sent to the low pressure column. The liquid (17) from the base of the auxiliary column is sent to the medium pressure column. A product rich in nitrogen can be extracted from the auxiliary column in liquid or gas form. The apparatus for carrying out this process comprises a double column with a medium and a low pressure column, an auxiliary column, an exchange line (LE) and means of carrying out all the transfers of fluids described above. The apparatus can include an argon column and a pump (P2) to pump and vaporize the nitrogen-enriched liquid extracted from the auxiliary column.

Description

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La présente invention est relative à un procédé et appareil de séparation d'air par distillation cryogénique. En particulier, il concerne la production d'azote pur en utilisant une colonne auxiliaire associée à un système de colonnes classique.  The present invention relates to a method and apparatus for air separation by cryogenic distillation. In particular, it relates to the production of pure nitrogen using an auxiliary column associated with a conventional column system.

Il est connu de produire de l'azote pur en prenant de l'azote gazeux en tête de la colonne moyenne pression d'une double colonne et en l'envoyant dans une colonne auxiliaire ayant un condenseur de tête. J-A-03158693 décrit un système dans lequel le liquide riche de la colonne moyenne pression est également envoyé à la colonne auxiliaire.  It is known to produce pure nitrogen by taking nitrogen gas at the head of the medium pressure column of a double column and by sending it to an auxiliary column having an overhead condenser. J-A-03158693 describes a system in which the rich liquid from the medium pressure column is also sent to the auxiliary column.

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 auxiliaire dans lequel : a) on envoie de l'air comprimé et épuré dans la colonne moyenne pression pour produire un fluide enrichi en oxygène et des fluides enrichis en azote b) on envoie un fluide enrichi en azote de la colonne moyenne pression à la colonne auxiliaire où il se sépare pour former un débit riche en azote en tête de colonne c) on condense au moins partiellement un des fluides enrichis en azote dans un rebouilleur de la colonne basse pression d) on envoie une partie du fluide enrichi en azote condensé du rebouilleur à la tête de la colonne basse pression e) on soutire un débit riche en oxygène en cuve de la colonne basse pression et un débit riche en azote en tête de la colonne basse pression caractérisé en ce que l'on envoie le fluide enrichi en azote à la cuve de la colonne auxiliaire comme seul débit d'alimentation.  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 an auxiliary column in which: a) compressed air is sent and purified in the medium pressure column to produce an oxygen-enriched fluid and nitrogen-enriched fluids b) a nitrogen-enriched fluid is sent from the medium pressure column to the auxiliary column where it separates to form a flow rich in nitrogen column head c) at least partially condensing one of the nitrogen-enriched fluids in a reboiler of the low pressure column d) sending part of the condensed nitrogen enriched fluid from the reboiler to the head of the low pressure column e) withdrawing a flow rich in oxygen at the bottom of the low pressure column and a flow rich in nitrogen at the head of the low pressure column, characterized in that the enriched fluid is sent n nitrogen at the bottom of the auxiliary column as the only feed rate.

Selon d'autres aspects facultatifs de l'invention, il est prévu que : - la colonne auxiliaire a un condenseur de tête et on envoie un liquide enrichi en oxygène de la cuve de la colonne moyenne pression au condenseur de tête, après une étape de détente.  According to other optional aspects of the invention, it is provided that: the auxiliary column has a head condenser and an oxygen-enriched liquid is sent from the tank of the medium pressure column to the head condenser, after a step of relaxation.

- le liquide enrichi en oxygène se vaporise partiellement dans le condenseur de tête de la colonne auxiliaire et au moins une partie du liquide vaporisé est envoyé à la colonne basse pression.  - the liquid enriched in oxygen partially vaporizes in the condenser at the head of the auxiliary column and at least part of the vaporized liquid is sent to the low pressure column.

- le liquide de cuve de la colonne auxiliaire est envoyé à la colonne moyenne pression.  - the tank liquid from the auxiliary column is sent to the medium pressure column.

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- un produit riche en azote de la colonne auxiliaire est soutiré sous forme liquide ou gazeuse.  - a product rich in nitrogen from the auxiliary column is withdrawn in liquid or gaseous form.

Selon un autre aspect de l'invention, il est prévu un appareil de séparation d'air comprenant une double colonne constituée par une colonne moyenne pression et une colonne basse pression, une colonne auxiliaire, une ligne d'échange, des moyens pour envoyer de l'air à séparer au moins à la colonne moyenne pression, des moyens pour envoyer, directement ou indirectement, des débits enrichis en oxygène et en azote de la colonne moyenne pression à la colonne basse pression, des moyens pour soutirer des débits enrichis en oxygène et azote de la colonne basse pression, des moyens pour envoyer un débit enrichi en azote de la colonne moyenne pression à la colonne auxiliaire et des moyens pour soutirer un produit riche en azote de la tête de la colonne auxiliaire caractérisé en ce qu'il n'y a aucun moyen d'effectuer un échange de masse et de chaleur en dessous du point d'entrée du débit enrichi en azote dans la colonne auxiliaire.  According to another aspect of the invention, there is provided an air separation device comprising a double column constituted by a medium pressure column and a low pressure column, an auxiliary column, an exchange line, means for sending the air to be separated at least at the medium pressure column, means for sending, directly or indirectly, flows enriched in oxygen and nitrogen from the medium pressure column to the low pressure column, means for withdrawing flows enriched in oxygen and nitrogen from the low pressure column, means for sending a nitrogen-enriched flow from the medium pressure column to the auxiliary column and means for withdrawing a product rich in nitrogen from the head of the auxiliary column characterized in that it does not There is no way to carry out a mass and heat exchange below the entry point of the nitrogen-enriched flow in the auxiliary column.

Selon d'autres aspects facultatifs, l'appareil comprend : - un condenseur de tête de la colonne auxiliaire ; - des moyens pour renvoyer le liquide de cuve de la colonne auxiliaire à la colonne moyenne pression ; - une colonne argon ; - des moyens pour pomper et vaporiser le liquide soutiré en tant que produit riche en azote de la colonne auxiliaire.  According to other optional aspects, the apparatus comprises: - a condenser at the head of the auxiliary column; - Means for returning the tank liquid from the auxiliary column to the medium pressure column; - an argon column; - Means for pumping and vaporizing the liquid withdrawn as a product rich in nitrogen from the auxiliary column.

L'adjonction de cette colonne auxiliaire de petites dimensions permet d'éviter d'installer un tronçon de distillation de tête de colonne moyenne pression pour assurer la purification de l'azote.  The addition of this small auxiliary column makes it possible to avoid installing a distillation section at the top of the medium pressure column to ensure the purification of the nitrogen.

La colonne d'azote pur permet de produire de petites quantités d'azote pur en tête de colonne et les plateaux assurent prioritairement la séparation d'azote et d'oxygène et non spécifiquement la separation d'autres gaz incondensables (hydrogène, monoxyde de carbone, néon, hélium..).  The pure nitrogen column makes it possible to produce small quantities of pure nitrogen at the top of the column and the trays give priority to the separation of nitrogen and oxygen and not specifically to the separation of other non-condensable gases (hydrogen, carbon monoxide , neon, helium ..).

L'invention sera décrite en plus en détail en se référant à la Figure qui montre un appareil de séparation d'air selon l'invention.  The invention will be described in more detail with reference to the Figure which shows an air separation device according to the invention.

L'appareil comprend une double colonne comprenant une colonne moyenne pression MP et une colonne basse pression BP reliées entre elles thermiquement, une colonne auxiliaire d'azote pur N2 et une ligne d'échange LE.  The apparatus comprises a double column comprising a medium pressure column MP and a low pressure column BP thermally connected, an auxiliary column of pure nitrogen N2 and an exchange line LE.

Trois débits d'air épuré à des pressions différentes se refroidissent dans la ligne d'échange. Le débit 3 AIR HP est surpressé dans le surpresseur S à la pression requise pour vaporiser les débits pompés dans la ligne d'échange, généralement entre 10 et 60 bar abs. A la sortie de la ligne d'échange LE, le débit liquéfié est divisé en deux.  Three purified air flows at different pressures cool in the exchange line. The 3 AIR HP flow rate is boosted in the blower S to the pressure required to vaporize the flow rates pumped in the exchange line, generally between 10 and 60 bar abs. At the exit of the LE exchange line, the liquefied debit is divided into two.

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Une fraction 29 de l'air liquéfié est envoyé dans la colonne moyenne pression MP quelques plateaux théoriques au-dessus de la cuve et le reste de l'air liquéfié 31 est envoyé à la colonne basse pression BP. A fraction 29 of the liquefied air is sent to the medium pressure column MP a few theoretical plates above the tank and the rest of the liquefied air 31 is sent to the low pressure column BP.

Le débit 5 AIR MP est sensiblement à la pression de la colonne moyenne pression MP, refroidi dans la ligne d'échange LE, d'où il sort à une température intermédiaire avant d'être envoyé en cuve de la colonne moyenne pression sous forme gazeuse.  The flow rate 5 AIR MP is substantially at the pressure of the medium pressure column MP, cooled in the exchange line LE, from which it leaves at an intermediate temperature before being sent to the tank of the medium pressure column in gaseous form. .

Le débit 7 AIR INS est comprimé dans le booster B à une pression de 10 bar abs., refroidi dans la ligne d'échange jusqu'à une température intermédiaire de celle-ci et ensuite détendu dans une turbine d'insufflation T avant d'être refroidi de nouveau dans la ligne d'échange jusqu'au bout froid et envoyé à un niveau intermédiaire de la colonne basse pression BP.  The flow 7 AIR INS is compressed in the booster B to a pressure of 10 bar abs., Cooled in the exchange line to an intermediate temperature thereof and then expanded in a blowing turbine T before be cooled again in the exchange line to the cold end and sent to an intermediate level of the low pressure BP column.

L'air envoyé à la colonne moyenne pression se sépare pour former un débit 9 enrichi en oxygène (liquide riche LR) et un débit enrichi en azote qui sert à chauffer le condenseur de tête 19 de la colonne MP qui constitue le rebouilleur de la colonne BP.  The air sent to the medium pressure column separates to form a flow 9 enriched in oxygen (rich liquid LR) and a flow enriched in nitrogen which is used to heat the head condenser 19 of the column MP which constitutes the reboiler of the column BP.

Une conduite (non illustrée) sort les incondensables du condenseur 19. A line (not shown) takes the non-condensables out of the condenser 19.

De l'azote liquide 27 (liquide pauvre LP) est soutiré en tête de la colonne MP et envoyé en tête de la colonne BP. De l'azote gazeux 15 est soutiré en tête de la colonne MP et envoyé en cuve de la colonne d'azote pur N2. Une conduite (non illustrée) sort les incondensables du condenseur de tête 22 de la colonne d'azote pur N2.  Liquid nitrogen 27 (lean liquid LP) is withdrawn at the top of the column MP and sent to the top of the column BP. Nitrogen gas 15 is drawn off at the head of the column MP and sent to the bottom of the column of pure nitrogen N2. A pipe (not shown) takes the non-condensables from the head condenser 22 from the column of pure nitrogen N2.

Une partie 13 du liquide riche 9 est envoyée après détente dans la colonne basse pression BP, le reste 11 étant envoyé au condenseur de tête 22 de la colonne N2 où il se vaporise pour former le liquide riche vaporisé LRV 23, qui est ensuite envoyé à la colonne BP.  A portion 13 of the rich liquid 9 is sent after expansion in the low pressure column BP, the rest 11 being sent to the head condenser 22 of the column N2 where it vaporizes to form the vaporized rich liquid LRV 23, which is then sent to the BP column.

Un débit liquide 17 est soutiré de la cuve de la colonne N2 et renvoyé en tête de la colonne MP. Le produit liquide 21 qui constitue de l'azote pur est pompé dans la pompe P2 et ensuite se vaporise dans la ligne d'échange LE pour former l'azote gazeux haute pression NG HP.  A liquid flow 17 is withdrawn from the tank of the column N2 and returned to the head of the column MP. The liquid product 21 which constitutes pure nitrogen is pumped into the pump P2 and then vaporizes in the exchange line LE to form the high pressure nitrogen gas NG HP.

Le liquide vaporisé dans le condenseur 19 est envoyé comme débit gazeux 32 en cuve de la colonne BP et un liquide 33 est pompé dans P3 pour surmonter la pression hydrostatique pour le monter au condenseur 19.  The liquid vaporized in the condenser 19 is sent as a gas flow 32 to the bottom of the column BP and a liquid 33 is pumped into P3 to overcome the hydrostatic pressure to mount it to the condenser 19.

Le liquide 35 qui sort du condenseur 19 est le produit riche en oxygène de l'appareil. Ce liquide est pompé à une pression élevée dans la pompe P1 et se vaporise dans la ligne d'échange LE.  The liquid 35 which leaves the condenser 19 is the product rich in oxygen of the apparatus. This liquid is pumped at a high pressure in the pump P1 and vaporizes in the LE exchange line.

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L'azote résiduaire gazeux NR 25 de la colonne BP sort de la tête de cette colonne et se réchauffe dans la ligne d'échange LE. Ce débit peut servir en partie à régénérer les lits d'adsorbants de l'appareil.  The residual nitrogen gas NR 25 from the column BP leaves the head of this column and heats up in the exchange line LE. This flow can be used in part to regenerate the adsorbent beds of the device.

Il sera compris que l'invention s'applique à d'autres systèmes (par exemples système avec colonne de séparation d'argon, avec trois colonnes dont une alimentée exclusivement de liquide riche provenant de la colonne moyenne pression, de type colonne Etienne (tel que décrit par exemple dans EP-A-538118), production d'oxygène pur ou impur..).  It will be understood that the invention applies to other systems (for example system with argon separation column, with three columns, one of which is supplied exclusively with rich liquid coming from the medium pressure column, of Etienne column type (such as described for example in EP-A-538118), production of pure or impure oxygen ..).

L'invention permet la production d'azote liquide ou gazeux, sous pression élevée ou atmosphérique en particulier sur les sites de production du type GTL pour lesquels les besoins en azote sont très faibles comparés aux besoins en oxygène. On pourrait par exemple envisager un système avec quatre trains de séparation d'air dont trois à double colonne et un avec une double colonne et colonne d'azote pur selon l'invention.  The invention allows the production of liquid or gaseous nitrogen, under high or atmospheric pressure, in particular on GTL type production sites for which the nitrogen requirements are very low compared to the oxygen requirements. One could for example envisage a system with four air separation trains, three of which with double column and one with a double column and column of pure nitrogen according to the invention.

Une seule colonne d'azote pur appartenant à un appareil de séparation d'air peut être alimentée en azote impur provenant de plusieurs appareils de séparation d'air, par exemple par du liquide transporté par réseau ou par camion. A single column of pure nitrogen belonging to an air separation device can be supplied with impure nitrogen coming from several air separation devices, for example by liquid transported by network or by truck.

Claims (10)

REVENDICATIONS 1. Procédé de séparation d'air par distillation cryogénique dans une installation comprenant une colonne moyenne pression (MP), une colonne basse pression (BP) et une colonne auxiliaire (N2) dans lequel : a) on envoie de l'air comprimé et épuré (5) dans la colonne moyenne pression pour produire un fluide enrichi en oxygène (9) et des fluides enrichis en azote (15, 27) b) on envoie un fluide enrichi en azote (15) de la colonne moyenne pression à la colonne auxiliaire où il se sépare pour former un débit riche en azote (21) en tête de colonne c) on condense au moins partiellement un des fluides enrichis en azote dans un rebouilleur (19) de la colonne basse pression d) on envoie une partie du fluide enrichi en azote condensé (27) du rebouilleur à la tête de la colonne basse pression e) on soutire un débit riche en oxygène (33) en cuve de la colonne basse pression et un débit riche en azote (25) en tête de la colonne basse pression caractérisé en ce que l'on envoie le fluide enrichi en azote (15) à la cuve de la colonne auxiliaire comme seul débit d'alimentation. 1. Process for the separation of air by cryogenic distillation in an installation comprising a medium pressure column (MP), a low pressure column (BP) and an auxiliary column (N2) in which: a) compressed air is sent and purified (5) in the medium pressure column to produce an oxygen-enriched fluid (9) and nitrogen-enriched fluids (15, 27) b) a nitrogen-enriched fluid (15) is sent from the medium pressure column to the column auxiliary where it separates to form a nitrogen-rich flow (21) at the top of the column c) at least partially condensing one of the nitrogen-enriched fluids in a reboiler (19) of the low-pressure column d) sending part of the fluid enriched in condensed nitrogen (27) from the reboiler to the head of the low pressure column e) a flow rich in oxygen (33) is withdrawn from the bottom of the low pressure column and a flow rich in nitrogen (25) at the head of the low pressure column characterized in that the nitrogen-enriched fluid (15) at the bottom of the auxiliary column as the only feed rate. 2. Procédé selon la revendication 1 dans lequel la colonne auxiliaire (N2) a un condenseur de tête (22) et on envoie un liquide (11) enrichi en oxygène de la cuve de la colonne moyenne pression au condenseur de tête, après une étape de détente.  2. Method according to claim 1 in which the auxiliary column (N2) has a head condenser (22) and a liquid (11) enriched in oxygen is sent from the tank of the medium pressure column to the head condenser, after a step of relaxation. 3. Procédé selon la revendication 2 dans lequel le liquide enrichi en oxygène (11) se vaporise partiellement dans le condenseur de tête (22) de la colonne auxiliaire et au moins une partie du liquide vaporisé (23) est envoyé à la colonne basse pression (BP).  3. Method according to claim 2 wherein the oxygen-enriched liquid (11) partially vaporizes in the overhead condenser (22) of the auxiliary column and at least part of the vaporized liquid (23) is sent to the low pressure column (BP). 4. Procédé selon l'une des revendications précédentes dans lequel le liquide de cuve (17) de la colonne auxiliaire (N2) est envoyé à la colonne moyenne pression (MP).  4. Method according to one of the preceding claims wherein the tank liquid (17) of the auxiliary column (N2) is sent to the medium pressure column (MP). 5. Procédé selon l'une des revendications précédentes comprenant des moyens pour soutirer un produit riche en azote (21) de la colonne auxiliaire sous forme liquide ou gazeuse.  5. Method according to one of the preceding claims comprising means for withdrawing a product rich in nitrogen (21) from the auxiliary column in liquid or gaseous form. 6. Appareil de séparation d'air comprenant une double colonne constituée par une colonne moyenne pression (MP) et une colonne basse pression (BP), une colonne auxiliaire (N2), une ligne d'échange (LE), des moyens (1,5) pour envoyer de l'air à séparer au moins à la colonne moyenne pression, des moyens pour  6. Air separation apparatus comprising a double column consisting of a medium pressure column (MP) and a low pressure column (BP), an auxiliary column (N2), an exchange line (LE), means (1 , 5) to send air to be separated at least to the medium pressure column, means for <Desc/Clms Page number 6><Desc / Clms Page number 6> envoyer, directement ou indirectement, des débits enrichis en oxygène (9) et en azote (27) de la colonne moyenne pression à la colonne basse pression, des moyens pour soutirer des débits enrichis en oxygène (33) et azote (25) de la colonne basse pression, des moyens (15) pour envoyer un débit enrichi en azote de la colonne moyenne pression à la colonne auxiliaire et des moyens pour soutirer un produit (21) riche en azote de la tête de la colonne auxiliaire caractérisé en ce qu'il n'y a aucun moyen d'effectuer un échange de masse et de chaleur en dessous du point d'entrée du débit enrichi en azote dans la colonne auxiliaire.  send, directly or indirectly, flows enriched in oxygen (9) and nitrogen (27) from the medium pressure column to the low pressure column, means for withdrawing flows enriched in oxygen (33) and nitrogen (25) from the low pressure column, means (15) for sending a nitrogen-enriched flow from the medium pressure column to the auxiliary column and means for withdrawing a product (21) rich in nitrogen from the head of the auxiliary column characterized in that there is no way to exchange mass and heat below the entry point of the nitrogen-enriched flow in the auxiliary column. 7. Appareil de séparation d'air selon la revendication 6 comprenant un condenseur de tête (22) de la colonne auxiliaire.  7. An air separation apparatus according to claim 6 comprising a head condenser (22) of the auxiliary column. 8. Appareil de séparation d'air selon la revendication 6 ou 7 comprenant des moyens pour renvoyer le liquide de cuve (17) de la colonne auxiliaire (N2) à la colonne moyenne pression (MP).  8. An air separation device according to claim 6 or 7 comprising means for returning the tank liquid (17) from the auxiliary column (N2) to the medium pressure column (MP). 9. Appareil de séparation d'air selon la revendication 6,7 ou 8 comprenant une colonne argon.  9. An air separation apparatus according to claim 6,7 or 8 comprising an argon column. 10. Appareil de séparation d'air selon la revendication 6,7, 8 ou 9 comprenant des moyens (P2, LE) pour pomper et vaporiser le liquide soutiré (21) en tant que produit riche en azote de la colonne auxiliaire. 10. An air separation apparatus according to claim 6,7, 8 or 9 comprising means (P2, LE) for pumping and vaporizing the withdrawn liquid (21) as a product rich in nitrogen from the auxiliary column.
FR0202347A 2002-02-25 2002-02-25 Separation of air, especially to produce small quantities of pure nitrogen, uses cryogenic distillation in a double column unit with an auxiliary column producing purer nitrogen from the other columns' nitrogen-rich discharges Pending FR2825454A3 (en)

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FR0202347A FR2825454A3 (en) 2002-02-25 2002-02-25 Separation of air, especially to produce small quantities of pure nitrogen, uses cryogenic distillation in a double column unit with an auxiliary column producing purer nitrogen from the other columns' nitrogen-rich discharges

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FR0202347A FR2825454A3 (en) 2002-02-25 2002-02-25 Separation of air, especially to produce small quantities of pure nitrogen, uses cryogenic distillation in a double column unit with an auxiliary column producing purer nitrogen from the other columns' nitrogen-rich discharges

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