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EP0694746B1 - Process for the production of a gas under pressure in variable quantities - Google Patents

Process for the production of a gas under pressure in variable quantities Download PDF

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Publication number
EP0694746B1
EP0694746B1 EP95401774A EP95401774A EP0694746B1 EP 0694746 B1 EP0694746 B1 EP 0694746B1 EP 95401774 A EP95401774 A EP 95401774A EP 95401774 A EP95401774 A EP 95401774A EP 0694746 B1 EP0694746 B1 EP 0694746B1
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EP
European Patent Office
Prior art keywords
air
pressure
liquid
heat
exchange line
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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.)
Expired - Lifetime
Application number
EP95401774A
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German (de)
French (fr)
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EP0694746A1 (en
Inventor
Maurice Grenier
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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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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
    • 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
    • F25J3/04151—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
    • F25J3/04151—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
    • F25J3/04236—Integration of different exchangers in a single core, so-called integrated cores
    • 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
    • F25J3/04406—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
    • F25J3/04472—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 cold from cryogenic liquids produced within the air fractionation unit and stored in internal or intermediate storages
    • F25J3/04496—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 cold from cryogenic liquids produced within the air fractionation unit and stored in internal or intermediate storages for compensating variable air feed or variable product demand by alternating between periods of liquid storage and liquid assist
    • F25J3/04503—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 cold from cryogenic liquids produced within the air fractionation unit and stored in internal or intermediate storages for compensating variable air feed or variable product demand by alternating between periods of liquid storage and liquid assist by exchanging "cold" between at least two different cryogenic liquids, e.g. independently from the main heat exchange line of the air fractionation and/or by using external alternating storage systems
    • F25J3/04509—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 cold from cryogenic liquids produced within the air fractionation unit and stored in internal or intermediate storages for compensating variable air feed or variable product demand by alternating between periods of liquid storage and liquid assist by exchanging "cold" between at least two different cryogenic liquids, e.g. independently from the main heat exchange line of the air fractionation and/or by using external alternating storage systems within the cold part of the air fractionation, i.e. exchanging "cold" within the fractionation and/or main heat exchange line
    • 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
    • Y10S62/912—External refrigeration system
    • Y10S62/913—Liquified gas

Definitions

  • the pressures indicated are absolute pressures.
  • condensation and “vaporization” is meant either condensation or vaporization proper, or pseudo-condensation or a pseudo-vaporization, depending on whether the pressures are sub-critical or super-critics.
  • Processes of this type are sometimes called “pump and air-oxygen rocker processes or air-nitrogen ".
  • the invention applies particularly to processes called “staggered bearings", the examples of which are described in the applications French patent FR-A-2,674,011; FR-A-2.688.052 and FR-A-2.692.664 and FR-A-2.721.383.
  • These processes, in which the liquefaction of air takes place at a temperature below the vaporization temperature of oxygen under its vaporization pressure have advantages interesting both from the point of view of specific energy consumption, that is, the energy required to produce a given quantity gaseous oxygen under pressure.
  • the invention aims to provide means for meet a variable demand for oxygen under pressure so particularly simple and without appreciable degradation of performance, nor thermally, that is to say the equilibrium of the exchange line nor on that of air distillation.
  • FR-A-1,158,639 describes a process for producing oxygen under pressure in which liquid oxygen stored at low pressure is pumped then vaporized in a heat exchanger against an air flow, one of which variable quantity is condensed. The condensed air is stored and sent to the low pressure column at constant flow. Air for the column medium pressure cools in another heat exchanger against cold gases from the appliance.
  • J-A-02293575 discloses a process for producing oxygen under pressure in which liquid oxygen stored at low pressure is pumped then vaporized in a heat exchanger against an air flow therein condenses. A constant flow of condensed air is sent to the column medium pressure. The rest of the air intended for this is cooled in a other heat exchanger.
  • the invention relates to a method according to the claim 1.
  • the invention also relates to a production installation a pressurized gas with variable flow rate according to claim 11.
  • the air distillation installation shown in FIG. 1 essentially comprises: an air compressor 1, an apparatus 2 for purifying the compressed air into water and CO 2 by adsorption, this apparatus comprising two bottles of adsorption 2A, 2B, one of which operates in adsorption while the other is in the process of regeneration, a blower turbine assembly 3 comprising an expansion turbine 4 and a blower or blower 5 whose shafts are coupled, the blower being optionally equipped a refrigerant (not shown), a heat exchanger 6 constituting the heat exchange line of the installation, a double distillation column 7 comprising a medium pressure column 8 surmounted by a low pressure column 9, with a vaporizer -condenser 10 putting the overhead vapor (nitrogen) from the column 8 in heat exchange relation with the tank liquid (oxygen) from the column 9, and a liquid oxygen tank 11, the bottom of which e st connected to a liquid oxygen pump 12 and a liquid air tank 13.
  • This installation is mainly intended to supply, via a pipe 15, gaseous oxygen under a predetermined high pressure, which can be between approximately 13 ⁇ 10 5 Pa and a few megaPascals.
  • All of the air to be distilled is compressed by compressor 1 to a pressure higher than the average pressure of column 8 but lower than high pressure. Then the air, precooled in the vicinity of the room temperature in 19 and cooled to a temperature between + 5 ° C and + 25 ° C in 20, is purified in one, 2A for example, bottles adsorption, and fully pressurized at high pressure by the booster 5, which is driven by the turbine 4.
  • the air is then introduced at the hot end of the exchanger 6 and cooled completely up to an intermediate temperature. At this temperature, a fraction of the air continues to cool and is liquefied in passages 21 of the exchanger, then left the exchange line and sent to the reservoir 13 via a line 22.
  • Liquid air drawn from this reservoir 13 via a line 24 is sub-cooled in the cold part of the exchange line 6, then is expanded to the low pressure in an expansion valve 25 with adjustable opening and introduced at an intermediate level in column 9.
  • part liquid air can be expanded at medium pressure and introduced into column 8.
  • Low pressure nitrogen is heated in passages 32 of the exchanger 6 and then evacuated via a line 33, while the waste gas W, after heating in passages 34 of the exchanger, is used to regenerate a bottle of adsorption, the bottle 2B in the example considered, before being evacuated via a pipe 35.
  • a pipe 36 has also been shown in FIG. 1 evacuation of liquid oxygen from the installation stitched on the pump discharge 12.
  • the high air pressure, at the discharge of the blower, is between approximately 25 ⁇ 10 5 Pa and the condensation pressure of the air by vaporization of the oxygen under the high oxygen pressure.
  • the refrigeration balance of the installation is balanced, with a temperature difference at the hot end of the heat exchange line of the order of 3 ° C. , by withdrawing from the installation at least one product, here oxygen, in liquid form, via line 36.
  • the liquid air contained in the reservoir 13 being at the high pressure, its latent heat of liquefaction is low, so that the flow additional liquid air sent to column 9 is significantly more greater than the additional oxygen flow that is drawn from it. he the higher the pressure of the liquid air is.
  • the quantity of cold gases produced by the double column and sent in the heat exchange line increases, thereby compensating for the reduction in the amount of cold sent to the latter due to the decrease in demand for gaseous oxygen and, consequently, in flow of oxygen vaporized in the passages 18, this drop being obtained in reducing the speed of the pump 12.
  • valve 17 closes, and the pump speed 12.
  • the liquid level drops in the reservoir11 and increases in reservoir 13.
  • this air is taken at the outlet of the apparatus 2 via a line 38, cooled and liquefied in passages additional 21A from the exchange line, and sent as previously to container 13 via line 22.
  • the liquefaction passages 21 of the air under high pressure are equipped, at the cold end of the exchange line, with a trigger 25A, and the sub-cooling passages of the withdrawn liquid air of the container 13 are equipped, at the same cold end, with the valve trigger 25.
  • valves 25 and 25A which ensures the functioning of the air / oxygen switch, similar to which has been described above with regard to FIG. 1.
  • the optimum pressure range from the point of view of the thermal equilibrium of the exchange line 6 and that of the distillation conditions, is between 30 ⁇ 10 5 Pa and approximately 35 ⁇ 10 5 Pa.
  • the invention also applies to the case where the liquid withdrawn is nitrogen, argon, or another liquid.

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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)
  • Filling Or Discharging Of Gas Storage Vessels (AREA)

Description

La présente invention est relative à un procédé de production d'un gaz sous pression à débit variable, du type dans lequel on distille de l'air dans une installation de distillation d'air comprenant un appareil de distillation comprenant une colonne moyenne pression et une colonne basse pression opérant à une basse pression et une ligne d'échange thermique pour refroidir l'air par échange de chaleur avec des produits provenant de l'appareil de distillation ; on soutire du liquide de cet appareil, on le stocke dans un récipient sous une pression voisine de la pression atmosphérique et égale à la basse pression, on amène le liquide stocké à une pression de vaporisation, on le vaporise et on le réchauffe sous cette pression dans la ligne d'échange thermique pour former le gaz sous pression, cette vaporisation et ce réchauffement s'accompagnant d'une liquéfaction d'air dans ses passages de liquéfaction d'air de la ligne d'échange thermique ; et dans lequel :

  • lors d'une augmentation de la demande du gaz sous pression par rapport au débit nominal, on soutire l'excès demandé, sous forme liquide, du récipient de stockage du liquide soutiré, on l'amène à la pression de vaporisation, et on le vaporise sous cette pression dans la ligne d'échange thermique, et on stocke une quantité correspondante d'air liquéfié par ladite vaporisation dans un récipient de stockage d'air liquide, sous une pression de stockage au moins égale à la pression de fonctionnement de la colonne moyenne pression.
The present invention relates to a process for producing a pressurized gas with variable flow rate, of the type in which air is distilled in an air distillation installation comprising a distillation apparatus comprising a medium pressure column and a low pressure column operating at low pressure and a heat exchange line for cooling the air by heat exchange with products from the distillation apparatus; liquid is drawn from this device, it is stored in a container under a pressure close to atmospheric pressure and equal to low pressure, the stored liquid is brought to a vaporization pressure, it is vaporized and it is heated under this pressure in the heat exchange line to form the gas under pressure, this vaporization and this heating being accompanied by air liquefaction in its air liquefaction passages of the heat exchange line; and in which:
  • during an increase in the demand for gas under pressure compared to the nominal flow rate, the required excess is withdrawn, in liquid form, from the container for storing the withdrawn liquid, it is brought to the vaporization pressure, and it is vaporizes under this pressure in the heat exchange line, and stores a corresponding amount of air liquefied by said vaporization in a liquid air storage container, under a storage pressure at least equal to the operating pressure of the medium pressure column.

Dans le présent mémoire, les pressions indiquées sont des pressions absolues. De plus, on entend par "condensation" et "vaporisation" soit une condensation ou une vaporisation proprement dite, soit une pseudo-condensation ou une pseudo-vaporisation, selon que les pressions sont sub-critiques ou super-critiques.In this specification, the pressures indicated are absolute pressures. In addition, by "condensation" and "vaporization" is meant either condensation or vaporization proper, or pseudo-condensation or a pseudo-vaporization, depending on whether the pressures are sub-critical or super-critics.

Les procédés de ce type (voir par exemple le brevet français FR-A-1.158.639) sont parfois appelés "procédés à pompe et à bascule air-oxygène ou air-azote". L'invention s'applique particulièrement aux procédés dits "à paliers décalés", dont les exemples sont décrits dans les demandes de brevet français FR-A-2.674.011 ; FR-A-2.688.052 et FR-A-2.692.664 et FR-A-2.721.383. Ces procédés, dans lesquels la liquéfaction de l'air s'effectue à une température inférieure à la température de vaporisation de l'oxygène sous sa pression de vaporisation, présentent des avantages intéressants tant du point de vue de la consommation en énergie spécifique, c'est-à-dire de l'énergie nécessaire pour produire une quantité donnée d'oxygène gazeux sous pression.Processes of this type (see for example the French patent FR-A-1.158.639) are sometimes called "pump and air-oxygen rocker processes or air-nitrogen ". The invention applies particularly to processes called "staggered bearings", the examples of which are described in the applications French patent FR-A-2,674,011; FR-A-2.688.052 and FR-A-2.692.664 and FR-A-2.721.383. These processes, in which the liquefaction of air takes place at a temperature below the vaporization temperature of oxygen under its vaporization pressure have advantages interesting both from the point of view of specific energy consumption, that is, the energy required to produce a given quantity gaseous oxygen under pressure.

L'invention a pour but de fournir des moyens permettant de satisfaire à une demande variable en oxygène sous pression de façon particulièrement simple et sans dégradation sensible des performances, ni sur le plan thermique, c'est-à-dire de l'équilibre de la ligne d'échange thermique, ni sur celui de la distillation de l'air.The invention aims to provide means for meet a variable demand for oxygen under pressure so particularly simple and without appreciable degradation of performance, nor thermally, that is to say the equilibrium of the exchange line nor on that of air distillation.

FR-A-1.158.639 décrit un procédé de production d'oxygène sous pression dans lequel de l'oxygène liquide stocké à basse pression est pompé puis vaporisé dans un échangeur de chaleur contre un débit d'air dont une quantité variable est condensée. L'air condensé est stocké et envoyé à la colonne basse pression en débit constant. L'air destiné à la colonne moyenne pression se refroidit dans un autre échangeur de chaleur contre les gaz froids de l'appareil.FR-A-1,158,639 describes a process for producing oxygen under pressure in which liquid oxygen stored at low pressure is pumped then vaporized in a heat exchanger against an air flow, one of which variable quantity is condensed. The condensed air is stored and sent to the low pressure column at constant flow. Air for the column medium pressure cools in another heat exchanger against cold gases from the appliance.

J-A-02293575 divulgue un procédé de production d'oxygène sous pression dans lequel de l'oxygène liquide stocké à basse pression est pompé puis vaporisé dans un échangeur de chaleur contre un débit d'air qui s'y condense. Un débit constant d'air condensé est envoyé à la colonne moyenne pression. Le reste de l'air destiné à celle-ci est refroidi dans un autre échangeur de chaleur.J-A-02293575 discloses a process for producing oxygen under pressure in which liquid oxygen stored at low pressure is pumped then vaporized in a heat exchanger against an air flow therein condenses. A constant flow of condensed air is sent to the column medium pressure. The rest of the air intended for this is cooled in a other heat exchanger.

A cet effet, l'invention a pour objet un procédé selon la revendication 1.To this end, the invention relates to a method according to the claim 1.

Ce procédé peut comporter une ou plusieurs des caractéristiques suivantes :

  • le palier de stockage d'air liquide est à une pression voisine de la pression à laquelle s'effectue ladite liquéfaction d'air ;
  • le récipient de stockage d'air liquide est à une pression comprise entre 30 x 105 Pa et 35 x 105 Pa environ ;
  • la totalité du liquide vaporisé est soutirée du récipient de stockage de liquide ;
  • on effectue ladite liquéfaction d'air à une température inférieure à la température de vaporisation du liquide sous ladite pression de vaporisation, et on évacue au moins un produit liquide de l'installation ; et
  • on comprime l'air destiné au récipient de stockage d'air liquide à ladite pression de stockage et le reste de l'air à une haute pression supérieure à cette pression de stockage.
This process can include one or more of the following characteristics:
  • the liquid air storage level is at a pressure close to the pressure at which said air liquefaction takes place;
  • the liquid air storage container is at a pressure of between 30 × 10 5 Pa and approximately 35 × 10 5 Pa;
  • all of the vaporized liquid is withdrawn from the liquid storage container;
  • said air liquefaction is carried out at a temperature below the vaporization temperature of the liquid under said vaporization pressure, and at least one liquid product is removed from the installation; and
  • the air intended for the liquid air storage container is compressed to said storage pressure and the rest of the air to a high pressure greater than this storage pressure.

L'invention a également pour objet une installation de production d'un gaz sous pression à débit variable selon la revendication 11.The invention also relates to a production installation a pressurized gas with variable flow rate according to claim 11.

Suivant d'autres caractéristiques de l'installation :

  • le récipient de stockage d'air liquide est relié auxdits passages de liquéfaction d'air par l'intermédiaire d'une vanne de détente ;
  • les moyens de compression comprennent un compresseur d'air principal suivi d'une soufflante adaptée pour surpresser une fraction de l'air non destinée au récipient de stockage d'air liquide.
According to other characteristics of the installation:
  • the liquid air storage container is connected to said air liquefaction passages by means of an expansion valve;
  • the compression means comprise a main air compressor followed by a blower adapted to overpress a fraction of the air not intended for the liquid air storage container.

Des exemples de mise en oeuvre de l'invention vont maintenant être décrits en regard des dessins annexés sur lesquels :

  • la figure 1 représente schématiquement une installation de production d'oxygène gazeux sous pression à débit variable conforme à l'invention ; et
  • la figure 2 est une vue analogue d'une variante.
Examples of implementation of the invention will now be described with reference to the accompanying drawings in which:
  • FIG. 1 schematically represents an installation for producing gaseous oxygen under pressure with variable flow rate according to the invention; and
  • Figure 2 is a similar view of a variant.

L'installation de distillation d'air représentée à la figure 1 comprend essentiellement : un compresseur d'air 1, un appareil 2 d'épuration de l'air comprimé en eau et en CO2 par adsorption, cet appareil comprenant deux bouteilles d'adsorption 2A, 2B dont l'une fonctionne en adsorption pendant que l'autre est en cours de régénération, un ensemble turbine soufflante 3 comprenant une turbine de détente 4 et une soufflante ou surpresseur 5 dont les arbres sont couplés, la soufflante étant éventuellement équipée d'un réfrigérant (non représenté), un échangeur de chaleur 6 constituant la ligne d'échange thermique de l'installation, une double colonne de distillation 7 comprenant une colonne moyenne pression 8 surmontée d'une colonne basse pression 9, avec un vaporiseur-condenseur 10 mettant la vapeur de tête (azote) de la colonne 8 en relation d'échange thermique avec le liquide de cuve (oxygène) de la colonne 9, et un réservoir d'oxygène liquide 11 dont le fond est relié à une pompe d'oxygène liquide 12 et un réservoir d'air liquide 13.The air distillation installation shown in FIG. 1 essentially comprises: an air compressor 1, an apparatus 2 for purifying the compressed air into water and CO 2 by adsorption, this apparatus comprising two bottles of adsorption 2A, 2B, one of which operates in adsorption while the other is in the process of regeneration, a blower turbine assembly 3 comprising an expansion turbine 4 and a blower or blower 5 whose shafts are coupled, the blower being optionally equipped a refrigerant (not shown), a heat exchanger 6 constituting the heat exchange line of the installation, a double distillation column 7 comprising a medium pressure column 8 surmounted by a low pressure column 9, with a vaporizer -condenser 10 putting the overhead vapor (nitrogen) from the column 8 in heat exchange relation with the tank liquid (oxygen) from the column 9, and a liquid oxygen tank 11, the bottom of which e st connected to a liquid oxygen pump 12 and a liquid air tank 13.

Cette installation est principalement destinée à fournir, via une conduite 15, de l'oxygène gazeux sous une haute pression prédéterminée, qui peut être comprise entre environ 13 x 105 Pa et quelques mégaPascal.This installation is mainly intended to supply, via a pipe 15, gaseous oxygen under a predetermined high pressure, which can be between approximately 13 × 10 5 Pa and a few megaPascals.

Pour cela, de l'oxygène liquide, soutiré de la cuve de la colonne 9 via une conduite 16 équipée d'une vanne 17 de régulation du niveau de liquide dans la cuve de la colonne 9, est stocké dans le réservoir 11. De l'oxygène liquide soutiré de ce réservoir est amené à la haute pression de vaporisation par la pompe 12 à l'état liquide, puis vaporisé et réchauffé sous cette haute pression dans des passages 18 de la ligne d'échange 6.For this, liquid oxygen, withdrawn from the tank of column 9 via a line 16 fitted with a valve 17 for regulating the level of liquid in the tank of column 9, is stored in tank 11. From the liquid oxygen withdrawn from this tank is brought to the high pressure of vaporization by the pump 12 in the liquid state, then vaporized and heated under this high pressure in passages 18 of the exchange line 6.

La chaleur nécessaire à cette vaporisation et à ce réchauffage, ainsi qu'au réchauffage et éventuellement à la vaporisation d'autres fluides soutirés de la double colonne, est fournie par l'air à distiller, dans les conditions suivantes :The heat necessary for this vaporization and this reheating, as well as heating and possibly vaporizing other fluids withdrawn from the double column, is supplied by the air to be distilled, in the following conditions:

La totalité de l'air à distiller est comprimée par le compresseur 1 à une pression supérieure à la moyenne pression de la colonne 8 mais inférieure à la haute pression. Puis l'air, prérefroidi au voisinage de la température ambiante en 19 et refroidi à une température comprise entre +5°C et +25°C en 20, est épuré dans l'une, 2A par exemple, des bouteilles d'adsorption, et surpressé en totalité à la haute pression par le surpresseur 5, lequel est entraíné par la turbine 4.All of the air to be distilled is compressed by compressor 1 to a pressure higher than the average pressure of column 8 but lower than high pressure. Then the air, precooled in the vicinity of the room temperature in 19 and cooled to a temperature between + 5 ° C and + 25 ° C in 20, is purified in one, 2A for example, bottles adsorption, and fully pressurized at high pressure by the booster 5, which is driven by the turbine 4.

L'air est alors introduit au bout chaud de l'échangeur 6 et refroidi en totalité jusqu'à une température intermédiaire. A cette température, une fraction de l'air poursuit son refroidissement et est liquéfiée dans des passages 21 de l'échangeur, puis est sortie de la ligne d'échange et envoyée dans le réservoir 13 via une conduite 22.The air is then introduced at the hot end of the exchanger 6 and cooled completely up to an intermediate temperature. At this temperature, a fraction of the air continues to cool and is liquefied in passages 21 of the exchanger, then left the exchange line and sent to the reservoir 13 via a line 22.

De l'air liquide soutiré de ce réservoir 13 via une conduite 24 est sous-refroidi dans la partie froide de la ligne d'échange 6, puis est détendu à la basse pression dans une vanne de détente 25 à ouverture réglable et introduit à un niveau intermédiaire dans la colonne 9. En variante, une partie de l'air liquide peut être détendue à la moyenne pression et introduite dans la colonne 8.Liquid air drawn from this reservoir 13 via a line 24 is sub-cooled in the cold part of the exchange line 6, then is expanded to the low pressure in an expansion valve 25 with adjustable opening and introduced at an intermediate level in column 9. As a variant, part liquid air can be expanded at medium pressure and introduced into column 8.

Le reste de l'air surpressé en 5 est détendu à la moyenne pression dans la turbine 4 puis envoyé directement, via une conduite 26, à la base de la colonne 8.The rest of the air boosted in 5 is relaxed to the average pressure in the turbine 4 then sent directly, via a line 26, to the base of column 8.

On reconnaít par ailleurs sur la figure 1 les conduites habituelles des installations à double colonne, celle représentée étant du type dit "à minaret", c'est-à-dire avec production d'azote sous la basse pression : les conduites 27 à 29 d'injection dans la colonne 9, à des niveaux croissants de "liquide riche" (air enrichi en oxygène) détendu, de "liquide pauvre inférieur" (azote impur) détendu et de "liquide pauvre supérieur" (azote pratiquement pur) détendu, respectivement, ces trois fluides étant respectivement soutirés à la base, en un point intermédiaire et au sommet de la colonne 8, et les conduites 30 de soutirage d'azote gazeux partant du sommet de la colonne 9 et 31 d'évacuation du gaz résiduaire (azote impur) partant du niveau d'injection du liquide pauvre inférieur. L'azote basse pression est réchauffé dans des passages 32 de l'échangeur 6 puis évacué via une conduite 33, tandis que le gaz résiduaire W, après réchauffement dans des passages 34 de l'échangeur, est utilisé pour régénérer une bouteille d'adsorption, la bouteille 2B dans l'exemple considéré, avant d'être évacué via une conduite 35.We also recognize in Figure 1 the usual pipes double column installations, the one shown being of the so-called "to minaret ", that is to say with nitrogen production under low pressure: injection lines 27 to 29 in column 9, at increasing levels of "rich liquid" (oxygen-enriched air) relaxed, "lower poor liquid" (impure nitrogen) relaxed and "higher lean liquid" (nitrogen practically pure) relaxed, respectively, these three fluids being respectively withdrawn at the base, at an intermediate point and at the top of column 8, and the pipes 30 for withdrawing nitrogen gas from the top of the column 9 and 31 for discharging the residual gas (impure nitrogen) from the lower lean liquid injection level. Low pressure nitrogen is heated in passages 32 of the exchanger 6 and then evacuated via a line 33, while the waste gas W, after heating in passages 34 of the exchanger, is used to regenerate a bottle of adsorption, the bottle 2B in the example considered, before being evacuated via a pipe 35.

On a encore représenté sur la figure 1 une conduite 36 d'évacuation d'oxygène liquide de l'installation piquée sur la conduite de refoulement de la pompe 12.A pipe 36 has also been shown in FIG. 1 evacuation of liquid oxygen from the installation stitched on the pump discharge 12.

La haute pression d'air, au refoulement de la soufflante, est comprise entre 25 x 105 Pa environ et la pression de condensation de l'air par vaporisation de l'oxygène sous la haute pression d'oxygène. Comme expliqué dans d'autres demandes de brevet qui décrivent des procédés "à pompe" et "à paliers décalés", c'est-à-dire dans lesquels, comme dans la présente invention, l'air qui apporte la chaleur de vaporisation de l'oxygène se condense au-dessous de la température de vaporisation de cet oxygène, le bilan frigorifique de l'installation est équilibré, avec un écart de température au bout chaud de la ligne d'échange thermique de l'ordre de 3°C, en soutirant de l'installation au moins un produit, ici de l'oxygène, sous forme liquide, via la conduite 36. The high air pressure, at the discharge of the blower, is between approximately 25 × 10 5 Pa and the condensation pressure of the air by vaporization of the oxygen under the high oxygen pressure. As explained in other patent applications which describe "pump" and "offset bearing" processes, that is to say in which, as in the present invention, the air which provides the heat of vaporization of the oxygen condenses below the vaporization temperature of this oxygen, the refrigeration balance of the installation is balanced, with a temperature difference at the hot end of the heat exchange line of the order of 3 ° C. , by withdrawing from the installation at least one product, here oxygen, in liquid form, via line 36.

En fonctionnement nominal, le niveau de liquide dans le réservoir 13 est constant, ainsi que celui du réservoir 11.In nominal operation, the liquid level in the reservoir 13 is constant, as is that of reservoir 11.

Lorsque la demande en oxygène gazeux sous pression, sur la conduite de production 15, varie, on maintient constant le débit d'air comprimé par le compresseur 1, ainsi que la pression de refoulement de ce compresseur, et on procède de la manière suivante.When the demand for gaseous oxygen under pressure, on the production line 15, varies, the air flow is kept constant compressed by compressor 1, as well as the discharge pressure of this compressor, and we proceed as follows.

Lorsque la demande en oxygène diminue, on augmente l'ouverture de la vanne 25 afin d'accroítre la quantité de liquide dans la colonne 9. Pour maintenir le niveau de liquide en cuve de cette colonne, la vanne 17 s'ouvre, de sorte qu'un débit accru d'oxygène liquide est envoyé dans le réservoir 11.When the oxygen demand decreases, we increase the opening of the valve 25 in order to increase the amount of liquid in the column 9. To maintain the level of liquid in the tank of this column, the valve 17 opens, so that an increased flow of liquid oxygen is sent in tank 11.

L'air liquide contenu dans le réservoir 13 étant à la haute pression, sa chaleur latente de liquéfaction est faible, de sorte que le débit supplémentaire d'air liquide envoyé dans la colonne 9 est sensiblement plus grand que le débit supplémentaire d'oxygène que l'on soutire de celle-ci. Il est d'autant plus grand que la pression de l'air liquide est plus élevée. Par suite, la quantité de gaz froids produite par la double colonne et envoyée dans la ligne d'échange thermique augmente, compensant d'autant la réduction de la quantité de froid envoyée dans cette dernière du fait de la baisse de la demande en oxygène gazeux et, par conséquent, du débit d'oxygène vaporisé dans les passages 18, cette baisse étant obtenue en réduisant la vitesse de la pompe 12.The liquid air contained in the reservoir 13 being at the high pressure, its latent heat of liquefaction is low, so that the flow additional liquid air sent to column 9 is significantly more greater than the additional oxygen flow that is drawn from it. he the higher the pressure of the liquid air is. Through next, the quantity of cold gases produced by the double column and sent in the heat exchange line increases, thereby compensating for the reduction in the amount of cold sent to the latter due to the decrease in demand for gaseous oxygen and, consequently, in flow of oxygen vaporized in the passages 18, this drop being obtained in reducing the speed of the pump 12.

Par conséquent, le niveau de liquide monte dans le réservoir 11 et il baisse dans ce réservoir 13.Consequently, the liquid level rises in the reservoir 11 and it drops in this tank 13.

Il est à noter que l'ajout d'air liquide supplémentaire nécessite une augmentation de la puissance de distillation dans la double colonne 7, ce qui est obtenu grâce au fait que la diminution du débit d'oxygène liquide vaporisé en 6 provoque une augmentation du débit gazeux introduit dans la colonne 8.It should be noted that the addition of additional liquid air requires a increase in the distillation power in the double column 7, this which is achieved by the fact that the decrease in the flow of liquid oxygen vaporized in 6 causes an increase in the gas flow introduced into the column 8.

Inversement, lors d'une augmentation de la demande en oxygène gazeux, on réduit l'ouverture de la vanne 25, ce qui réduit le débit d'air liquide envoyé dans la colonne 9, la vanne 17 se ferme, et on augmente la vitesse de la pompe 12. Ainsi, le niveau de liquide baisse dans le réservoir11 et augmente dans le réservoir 13. Conversely, during an increase in oxygen demand gaseous, reducing the opening of the valve 25, which reduces the air flow liquid sent to column 9, valve 17 closes, and the pump speed 12. Thus, the liquid level drops in the reservoir11 and increases in reservoir 13.

Pour des raisons analogues à ce qui a été expliqué plus haut, ceci a pour conséquence une baisse de la quantité de gaz froids envoyée dans la ligne d'échange thermique, cette baisse compensant dans une large mesure l'augmentation de la quantité de froid introduite dans cette dernière du fait du débit supplémentaire d'oxygène liquide à vaporiser.For reasons similar to what has been explained above, this results in a decrease in the quantity of cold gases sent in the heat exchange line, this drop offsetting to a large extent measures the increase in the amount of cold introduced into the latter due to the additional flow of liquid oxygen to be vaporized.

On comprend qu'il est avantageux de stocker l'air liquide en 13 à la pression la plus élevée possible, pour amplifier les phénomènes expliqués ci-dessus. Toutefois, pour des raisons technologiques ou parce que la haute pression d'air est super-critique, on peut, en variante, détendre l'air liquide dans une vanne de détente 37 prévue dans la conduite 22, avant de l'introduire dans le réservoir 13, jusqu'à une pression intermédiaire entre la haute pression d'air et la moyenne pression de la colonne 8.We understand that it is advantageous to store the liquid air in 13 to the highest possible pressure, to amplify the phenomena explained above. However, for technological reasons or because the high air pressure is super-critical, we can, alternatively, relax the liquid air in an expansion valve 37 provided in line 22, before introduce it into the reservoir 13, until an intermediate pressure between the high air pressure and medium pressure in column 8.

Dans le cas où l'air liquide est stocké à une pression intermédiaire, il est intéressant, du point de vue énergétique, de ne pas comprimer à la haute pression l'air destiné au récipient de stockage 13. Ainsi, dans la variante de la figure 2, cet air est prélevé à la sortie de l'appareil 2 via une conduite 38, refroidi et liquéfié dans des passages supplémentaires 21A de la ligne d'échange, et envoyé comme précédemment au récipient 13 via la conduite 22.In the case where the liquid air is stored at a pressure intermediate, it is interesting, from an energy point of view, not to compress at high pressure the air intended for the storage container 13. Thus, in the variant of FIG. 2, this air is taken at the outlet of the apparatus 2 via a line 38, cooled and liquefied in passages additional 21A from the exchange line, and sent as previously to container 13 via line 22.

Les passages de liquéfaction 21 de l'air sous la haute pression sont équipés, au bout froid de la ligne d'échange, d'une vanne de détente 25A, et les passages de sous-refroidissement de l'air liquide soutiré du récipient 13 sont équipés, au même bout froid, de la vanne de détente 25.The liquefaction passages 21 of the air under high pressure are equipped, at the cold end of the exchange line, with a trigger 25A, and the sub-cooling passages of the withdrawn liquid air of the container 13 are equipped, at the same cold end, with the valve trigger 25.

Dans cette variante, c'est la commande des vannes 25 et 25A qui assure le fonctionnement de la bascule air/oxygène, analogue par ailleurs à ce qui a été décrit plus haut en regard de la figure 1.In this variant, it is the control of valves 25 and 25A which ensures the functioning of the air / oxygen switch, similar to which has been described above with regard to FIG. 1.

La gamme de pressions optimales, du point de vue de l'équilibre thermique de la ligne d'échange 6 et de celui des conditions de distillation, est comprise entre 30 x 105 Pa et 35 x 105 Pa environ.The optimum pressure range, from the point of view of the thermal equilibrium of the exchange line 6 and that of the distillation conditions, is between 30 × 10 5 Pa and approximately 35 × 10 5 Pa.

L'invention s'applique également au cas où le liquide soutiré est de l'azote, de l'argon ou un autre liquide.The invention also applies to the case where the liquid withdrawn is nitrogen, argon, or another liquid.

Claims (15)

  1. Method for producing a gas under pressure at variable flow rate, of the type in which air is distilled in an air distillation installation comprising a distillation apparatus (7) comprising an intermediate-pressure column (8) and a low-pressure column (9) operating at low pressure, and a heat-exchange line (6) for cooling air by heat exchange with products originating from the distillation apparatus; liquid is withdrawn from this apparatus, it is stored in a container (11) at a pressure close to atmospheric pressure and equal to the low pressure, the stored liquid is brought to a vaporization pressure, it is vaporized and it is heated at this pressure in the heat-exchange line in order to form the pressurized gas, this vaporization and this heating being accompanied by liquefaction of air in its air-liquefaction passages of the heat-exchange line; and in which:
    in the event of an increase in the demand for the pressurized gas compared to the nominal flow rate, the required excess is withdrawn in liquid form from the withdrawn-liquid storage container (11), it is brought (at 12) to the vaporization pressure and it is vaporized at this pressure (at 18) in the heat-exchange line (6), and a corresponding quantity of air liquified by the said vaporization is stored in a liquid-air storage container (13), at a storage pressure at least equal to the operating pressure of the intermediate-pressure column,
       characterized in that the liquid air is stored at a storage pressure of preferably greater than the pressure of the intermediate-pressure column and in that nitrogen-rich gases (30, 31) are sent from the low-pressure column (9) to the heat-exchange line and in the event of a reduction in demand for pressurized gas compared to the nominal output, the excess produced by the distillation apparatus is withdrawn in liquid form from this apparatus, this liquid is sent into the liquid storage container (11) and a corresponding additional quantity of previously stored liquid air (13) is introduced into the distillation apparatus (7).
  2. Method according to Claim 1, characterized in that the liquid-air storage container (13) is at a pressure close to the pressure at which the said air liquefaction takes place.
  3. Method according to Claim 1 or 2, characterized in that the liquid-air storage container (13) is at a pressure between approximately 30 H 105 Pa and 35 H 105 Pa.
  4. Method according to any one of Claims 1 to 3 characterized in that all the vaporized liquid is withdrawn from the liquid-storage container (11).
  5. Method according to any one of Claims 1 to 4, characterized in that the said liquefaction of air is carried out at a temperature below the vaporization temperature of the liquid withdrawn at the said vaporization pressure, and at least one liquid product is removed from the installation.
  6. Method according to any one of Claims 1 to 5, characterized in that the air (38) intended for the liquid-air storage container (13) is compressed (at 1) to the said storage pressure and the rest of the air is compressed to a high pressure higher than this storage pressure.
  7. Method according to one of Claims 1 to 6, in which all the air intended for the distillation apparatus (7) is sent to the heat-exchange line (6) where it cools.
  8. Method according to one of Claims 1 to 7, in which the amount of liquid sent to the heat-exchange line is varied by varying the speed of a pump (12) which serves to bring the liquid to the vaporization pressure.
  9. Method according to one of Claims 1 to 8, in which a compressor (1) serves to compress the air intended for the apparatus and, when the demand for pressurized gas varies, the flow rate of air compressed by the compressor is kept constant.
  10. Method according to one of Claims 1 to 9, in which the corresponding additional amount of liquid air is sent to the low-pressure column.
  11. Plant for production of a gas under pressure at variable flow rate, of the type comprising an air distillation apparatus (7) comprising an intermediate-pressure column (8) and a low-pressure column (9), a heat-exchange line (6) for cooling the air by heat exchange with products originating from the distillation apparatus, means (16, 17) for withdrawing liquid from the apparatus; means (5) for bringing at least a fraction of the air to be distilled to a high pressure, and sending it into air-liquefaction packages (21; 21, 21A) of the heat-exchange line, a liquid-storage container (11) at a pressure close to atmospheric pressure, connected to the distillation apparatus (7) and provided with means (12) for withdrawing liquid at adjustable flow rate, bringing it to the vaporization pressure and sending it into vaporization passages (18) of the heat-exchange line, and a liquid-air storage container (13) connected upstream to the air-liquefaction passages (21; 21A) of the heat-exchange line and, downstream, via pressure-reduction means (25), to the distillation apparatus, characterized in that the liquid-air storage container (13) is at a markedly higher pressure than the highest operating pressure of the distillation apparatus (7), the expansion means are expansion means with adjustable flow rate and in that the plant includes means (30, 31) for sending nitrogen-rich gases from the low-pressure column (9) to the heat-exchange line.
  12. Plant according to Claim 11, characterized in that the container (11) for storing the liquid is interposed between the air-distillation apparatus (7) and means (12) for bringing all the liquid to be vaporized to the vaporization pressure.
  13. Plant according to either of Claims 11 and 12, characterized in that the liquid-air storage container (13) is connected to the said air-liquefaction passages (21; 21A) via a pressure-reducer valve (37).
  14. Plant according to any one of Claims 11 to 13, characterized in that the compression means (1, 5) comprises a main air compressor (1) followed by a blower (5) designed to supercharge a fraction of the air not intended for the liquid-air storage container (13).
  15. Plant according to one of Claims 11 to 14, comprising means (1, 5) for sending all the air intended for the heat-exchange line (6).
EP95401774A 1994-07-29 1995-07-26 Process for the production of a gas under pressure in variable quantities Expired - Lifetime EP0694746B1 (en)

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FR9409481A FR2723184B1 (en) 1994-07-29 1994-07-29 PROCESS AND PLANT FOR THE PRODUCTION OF GAS OXYGEN UNDER PRESSURE WITH VARIABLE FLOW RATE
FR9409481 1994-07-29

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CN1119607C (en) 2003-08-27
CA2154984A1 (en) 1996-01-30
DE69516339D1 (en) 2000-05-25
KR960003774A (en) 1996-02-23
FR2723184A1 (en) 1996-02-02
CN1154463A (en) 1997-07-16
FR2723184B1 (en) 1996-09-06
EP0694746A1 (en) 1996-01-31
JPH08170875A (en) 1996-07-02
ES2145885T3 (en) 2000-07-16
KR100394311B1 (en) 2003-10-22
US5526647A (en) 1996-06-18
ZA956332B (en) 1996-03-11
DE69516339T2 (en) 2000-09-21

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