WO2022175194A1 - Method for separating air by cryogenic distillation - Google Patents

Method for separating air by cryogenic distillation Download PDF

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Publication number
WO2022175194A1
WO2022175194A1 PCT/EP2022/053473 EP2022053473W WO2022175194A1 WO 2022175194 A1 WO2022175194 A1 WO 2022175194A1 EP 2022053473 W EP2022053473 W EP 2022053473W WO 2022175194 A1 WO2022175194 A1 WO 2022175194A1
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Prior art keywords
column
temperature
air
heat exchanger
sent
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PCT/EP2022/053473
Other languages
French (fr)
Inventor
Benoit Davidian
Original Assignee
L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude filed Critical L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude
Priority to JP2023547532A priority Critical patent/JP2024508391A/en
Priority to US18/277,794 priority patent/US20240230222A9/en
Priority to KR1020237027186A priority patent/KR20230147063A/en
Priority to CA3206388A priority patent/CA3206388A1/en
Priority to CN202280013695.XA priority patent/CN116848365A/en
Priority to EP22709278.0A priority patent/EP4295096A1/en
Publication of WO2022175194A1 publication Critical patent/WO2022175194A1/en

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04248—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
    • F25J3/04006—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
    • 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
    • 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
    • F25J3/04151—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
    • F25J3/0423—Subcooling of liquid process streams
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • 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
    • F25J3/04375—Details relating to the work expansion, e.g. process parameter etc.
    • F25J3/04393—Details relating to the work expansion, e.g. process parameter etc. using multiple or multistage gas work expansion
    • 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
    • F25J3/04769—Operation, control and regulation of the process; Instrumentation within the process
    • F25J3/04781—Pressure changing devices, e.g. for compression, expansion, liquid pumping
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04763—Start-up or control of the process; Details of the apparatus used
    • F25J3/04866—Construction and layout of air fractionation equipments, e.g. valves, machines
    • F25J3/04872—Vertical layout of cold equipments within in the cold box, e.g. columns, heat exchangers etc.
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2290/00—Other details not covered by groups F25J2200/00 - F25J2280/00
    • F25J2290/12—Particular process parameters like pressure, temperature, ratios

Definitions

  • the present invention relates to a process for separating air by cryogenic distillation.
  • a separation apparatus generally comprises an exchange line where the air to be distilled is cooled against at least two distillation products and a column system, including a first column operating at a first pressure and a second column operating at a second pressure lower than the first column.
  • the head of the first column is thermally connected to the bottom of the second column.
  • WO19126927 describes an air separation device by cryogenic distillation in which the main exchange line is located under the system of distillation columns, and with the hot end of the exchanger positioned downwards.
  • the air intended for the first column is cooled in the exchange line before being sent to the first column.
  • bottom liquid (LR) from the first column is expanded and sent to an intermediate point in the second column.
  • the top liquid (LP) of the first column is expanded and sent to the top of the second column.
  • the two liquids are subcooled in a heat exchanger against an overhead gas from the second column.
  • the exhaust from the blower turbine is sent directly to the second column, for reasons of simplicity.
  • a relatively hot gas is sent to the second column.
  • the invention consists in supplying the column with at least one air flow at a temperature greater than 1°C, or even 2°C with respect to its dew temperature, including in the reduced steps of the device.
  • This implementation makes it possible to avoid condensing the air intended for the first column in the main exchange line.
  • the air leaves the main exchange line at a temperature higher than 1°C, or even 2°C compared to its dew point temperature.
  • One way to ensure that the air destined for the first column is sufficiently above the dew point is to push the cooling of certain fluids entering the distillation system, as well as fluids internal to the distillation system. In this case, it is possible to size an exchange line with very low pressure drops, without having to take into account a liquid entrainment criterion with respect to safety.
  • a variant to ensure that the air destined for the first column is sufficiently above the dew point is to modify the subcooling in order to reduce the temperature of a liquid entering the second column.
  • the cooling of the oxygen-enriched liquid is pushed so that it exits at a lower temperature than the inlet of the enriched liquid. There is therefore a common zone in the sub-cooler where the two liquids are cooled at the same time against at least a flow of nitrogen coming from the second column.
  • the exhaust from the turbine is sent back to the exchange line to cool against the waste nitrogen (and possibly the purer nitrogen coming from the second column) and against oxygen.
  • a process for separating air by cryogenic distillation in a system of columns comprising a first column operating at a first pressure and a second column operating at a second pressure lower than the first pressure , the top of the first column being thermally connected to the bottom of the second column wherein:
  • the method uses a system of columns comprising a first column K1 operating at a first pressure and a second column K2 operating at a second pressure lower than the first pressure.
  • the first column K1 is thermally connected to the second column K2 by a bottom vaporizer of the second column.
  • the first column is arranged below the second column K2 and the head of the first column being thermally connected to the bottom of the second column.
  • a heat exchanger E with brazed aluminum plates is arranged below the first column K1.
  • a flow of air 1 is compressed by the compressor 3 to the first pressure, cooled by the cooler 5 and purified of water and carbon dioxide in the purification unit 7. To cool, the air is sent to the hot end of exchanger E at the bottom of the exchanger and rises upwards, since the cold end of the exchanger is at the top.
  • the purified air 9 cools in the heat exchanger E and is divided into two at a temperature T2 which is an intermediate temperature of the exchanger E. Part 11 of the air continues to cool in the exchanger until at a temperature T1 higher by at least 1°C, preferably by at least 2°C, than the dew point temperature of the air fraction 9.
  • the pressure drop of the air 9, 11 crossing the exchanger E does not exceed 120, or even 100 mbar.
  • the liquid 10 and the liquid 12 are sent to a subcooler S where at least a flow of gaseous nitrogen 15 coming from the second column K2 is heated.
  • Liquid 10 enters the subcooler at the hot end of it and is cooled to a temperature below that at which liquid 12 enters subcooler S.
  • Liquid 12 exits the cold end of the subcooler.
  • the subcooled liquid 10 and the subcooled liquid 12 are each expanded in a valve and the liquid 10 is sent to a level of the second column K2 and the liquid 12 is sent to a level of the second column K2 higher than that at which the liquid 10.
  • the subcooler comprises a section where the liquids 10 and 12 are both cooled against the nitrogen 15.
  • the subcooler S can be placed next to the column K1 and have its hot end disposed downwards.
  • Part 13 of the air at temperature T2 is expanded in a turbine T without having been compressed downstream of the exchanger, is sent back to the heat exchanger E at a temperature T3 and is cooled in the exchanger E at a temperature T4 before being sent to the second column in gaseous form, the temperature T2 being higher than T1.
  • T4 can be greater than, equal to, or less than T1.
  • T4 is higher by at least 1°C, preferably by at least 2°C, than the dew temperature of the expanded flow 13.
  • Part 13 leaves the cold end of the exchanger E and is sent directly to the second column K2 in gaseous form at a level below the arrival of the expanded liquid 10. As for the air 11, the part 13 cools in the exchanger going upwards.
  • Column K2 separates streams 10 and 12 by distillation to form a nitrogen-enriched gas 15 at the top of the column and an oxygen-enriched gas 17 at the bottom of the column. Gas 17 heats up as it descends through exchanger E and then serves as the product of the process.
  • the gas 15 reheated in the subcooler and then descending in the exchanger E is divided into two, a part serving to regenerate the purification 7 and the rest serving as product or residual.
  • first column K1 is supplied with air only by gaseous air flows.
  • the second column K2 could also be supplied with air, in this case it would be a supply of gaseous air exclusively.
  • the process only produces gas streams 15, 17 as end products.
  • the purging of the K2 column bottom condenser is not considered an end product.
  • the sub-cooler S can be integrated into the main exchange line E. This makes it possible to further optimize the exhaustion of the cold fluids 15, 17 resulting from the distillation (possibly also pure nitrogen from the second column K2) to cool as much as possible the rich and lean liquids 10, 12 and the air at the second pressure coming from an insufflation turbine.
  • a flow of liquefied air withdrawn from column K1 can be subcooled in subcooler S before being sent to column K2.
  • three airflows are used.
  • the air is compressed to the pressure of the second column and then purified.
  • the air is divided in two, a part being cooled to the pressure of the second column and sent to the second column by rising in the exchanger.
  • the final temperature leaving the exchanger will be higher by at least 1°C, preferably by at least 2°C, than its dew temperature at the second pressure.
  • the other part is boosted to the pressure of the first column.
  • a fraction of this part is cooled in the exchanger by rising and leaving it at a temperature T1 higher by at least 1°C, preferably by at least 2°C above the dew point temperature of the air fraction.
  • T4 is at least 1°C, preferably at least 2°C above the dew temperature.

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

Abstract

In a method for separating air by cryogenic distillation in a system of columns comprising a first column (K1) operating at a first pressure and a second column (K2) operating at a second pressure which is lower than the first column, the temperature T1 at which an airflow (11) leaves, after cooling, the heat exchanger by rising towards the cold end of said heat exchanger and enters the first column is at least 1°C, preferably at least 2°C, higher than the dew point of the airflow.

Description

Procédé de séparation d’air par distillation cryogéniqueAir separation process by cryogenic distillation
La présente invention est relative à un procédé de séparation d’air par distillation cryogénique.The present invention relates to a process for separating air by cryogenic distillation.
Un appareil de séparation comprend généralement une ligne d’échange où l’air à distiller se refroidit contre au moins deux produits de la distillation et un système de colonne, dont une première colonne opérant à une première pression et une deuxième colonne opérant à une deuxième pression plus basse que la première colonne.A separation apparatus generally comprises an exchange line where the air to be distilled is cooled against at least two distillation products and a column system, including a first column operating at a first pressure and a second column operating at a second pressure lower than the first column.
La tête de la première colonne est thermiquement reliée à la cuve de la deuxième colonne.The head of the first column is thermally connected to the bottom of the second column.
WO19126927 décrit un appareil de séparation d’air par distillation cryogénique dans lequel la ligne d’échange principale est située sous le système de colonnes à distiller, et avec le bout chaud de l’échangeur disposé vers le bas.WO19126927 describes an air separation device by cryogenic distillation in which the main exchange line is located under the system of distillation columns, and with the hot end of the exchanger positioned downwards.
L’air destiné à la première colonne se refroidit dans la ligne d’échange avant d’être envoyé dans la première colonne. The air intended for the first column is cooled in the exchange line before being sent to the first column.
Au cours de son refroidissement, de bas en haut de la ligne d’échange principale, cet air se condense en partie. Il faut s’assurer que le liquide obtenu est bien entrainé par le gaz, pour éviter que le liquide stagne dans la ligne d’échange, et donc toute possibilité d’enrichissement local en oxygène et impuretés secondaires de l’air (typiquement CnHm) qui présente un risque de sécurité.During its cooling, from bottom to top of the main exchange line, this air partially condenses. It must be ensured that the liquid obtained is well entrained by the gas, to prevent the liquid from stagnating in the exchange line, and therefore any possibility of local enrichment in oxygen and secondary impurities in the air (typically C n H m ) which presents a security risk.
Obtenir une vitesse suffisante de gaz, et ce y compris en marche réduite implique d’avoir des pertes de charges importantes sur l’air destiné à la première colonne, ce qui est couteux en énergie.Obtaining sufficient gas velocity, including in reduced operation, implies having significant pressure drops on the air intended for the first column, which is expensive in terms of energy.
Dans un appareil de séparation d’air, le liquide de cuve (LR) de la première colonne est détendu et envoyé à un point intermédiaire de la deuxième colonne. Le liquide de tête (LP) de la première colonne est détendu et envoyé à la tête de la deuxième colonne. Les deux liquides sont sousrefroidis dans un échangeur de chaleur contre un gaz de tête de la deuxième colonne.In an air separation apparatus, bottom liquid (LR) from the first column is expanded and sent to an intermediate point in the second column. The top liquid (LP) of the first column is expanded and sent to the top of the second column. The two liquids are subcooled in a heat exchanger against an overhead gas from the second column.
Dans cet échangeur appelé sous-refroidisseur, notamment dans une configuration courants-croisés, le refroidissement du liquide de tête enrichi en azote appelé liquide pauvre LP et le liquide de cuve enrichi en oxygène appelé liquide riche LR se fait en deux sections distinctes, comme si on avait deux échangeurs en série. Cela signifie que le liquide enrichi en oxygène est refroidi à une température supérieure à celle d’entrée du liquide de tête de la première colonne. Dans cette configuration, on n’épuise pas complètement le froid disponible dans le résiduaire.In this exchanger called sub-cooler, in particular in a cross-current configuration, the cooling of the nitrogen-enriched overhead liquid called lean liquid LP and the bottom liquid enriched in oxygen called rich liquid LR is done in two separate sections, as if we had two exchangers in series. This means that the oxygen-enriched liquid is cooled to a higher temperature than the inlet temperature of the first column overhead liquid. In this configuration, the cold available in the residual is not completely exhausted.
Le sous-refroidisseur classique est illustré à la page 96 de « Industrial Gas Handbook » de Kerry, CRC Press 2007. La disposition exacte des fluides n’est pas toujours illustrée dans des brevets ou d’autres documents pour des raisons de simplification des figures.The classic subcooler is shown on page 96 of Kerry's "Industrial Gas Handbook", CRC Press 2007. The exact arrangement of fluids is not always shown in patents or other documents for simplicity of figures .
Par ailleurs, l’échappement de la turbine d’insufflation est envoyé directement dans la deuxième colonne, pour des raisons de simplicité. On envoie un gaz relativement chaud dans la deuxième colonne.In addition, the exhaust from the blower turbine is sent directly to the second column, for reasons of simplicity. A relatively hot gas is sent to the second column.
Cela a pour conséquence de réduire la récupération frigorifique des fluides froids et nécessite de condenser en partie (typiquement autour de 1 à 2%) l’air qui sort de la ligne d’échange principale et qui va vers la cuve de la première colonne.This has the consequence of reducing the refrigeration recovery of cold fluids and requires partly condensing (typically around 1 to 2%) the air that leaves the main exchange line and goes to the tank of the first column.
L’invention consiste à alimenter la colonne par au moins un débit d’air à une température supérieure à 1°C, voire 2°C par rapport à sa température de rosée, y compris dans les marches réduites de l’appareil. Cette mise en œuvre permet d’éviter de condenser l’air destiné à la première colonne dans la ligne d’échange principale. Ainsi l’air sort de la ligne d’échange principale à une température supérieure à 1°C, voire 2°C par rapport à sa température de rosée. The invention consists in supplying the column with at least one air flow at a temperature greater than 1°C, or even 2°C with respect to its dew temperature, including in the reduced steps of the device. This implementation makes it possible to avoid condensing the air intended for the first column in the main exchange line. Thus the air leaves the main exchange line at a temperature higher than 1°C, or even 2°C compared to its dew point temperature.
Un moyen de s’assurer que l’air destiné à la première colonne soit suffisamment au-dessus du point de rosée est de pousser le refroidissement de certains fluides entrants dans le système de distillation, ainsi que des fluides internes au système de distillation. On peut dans ce cas dimensionner une ligne d’échange avec de très faibles pertes de charge, sans avoir à prendre en compte un critère d’entrainement de liquide vis-à-vis de la sécurité.One way to ensure that the air destined for the first column is sufficiently above the dew point is to push the cooling of certain fluids entering the distillation system, as well as fluids internal to the distillation system. In this case, it is possible to size an exchange line with very low pressure drops, without having to take into account a liquid entrainment criterion with respect to safety.
Il s’agit de récupérer le plus possible de froid des fluides issus de la distillation (azote résiduaire, oxygène, azote à la deuxième pression plus pur que l’azote résiduaire).This involves recovering as much cold as possible from the fluids resulting from the distillation (residual nitrogen, oxygen, nitrogen at the second pressure purer than the residual nitrogen).
Une variante pour assurer que l’air destiné à la première colonne soit suffisamment au-dessus du point de rosée consiste à modifier le sousrefroidissement afin de réduire la température d’un liquide rentrant dans la deuxième colonne.A variant to ensure that the air destined for the first column is sufficiently above the dew point is to modify the subcooling in order to reduce the temperature of a liquid entering the second column.
Dans le sous-refroidisseur, le refroidissement du liquide enrichi en oxygène est poussé de façon à sortir à une température inférieure à celle d’entrée du liquide enrichi. On a donc une zone commune dans le sous-refroidisseur où les deux liquides sont refroidis à la fois contre au moins un débit d’azote provenant de la deuxième colonne. In the subcooler, the cooling of the oxygen-enriched liquid is pushed so that it exits at a lower temperature than the inlet of the enriched liquid. There is therefore a common zone in the sub-cooler where the two liquids are cooled at the same time against at least a flow of nitrogen coming from the second column.
Selon une autre variante, dans la ligne d’échange, l’échappement de la turbine est renvoyé vers la ligne d’échange pour se refroidir contre l’azote résiduaire (et éventuellement l’azote plus pur provenant de la deuxième colonne) et contre l’oxygène.According to another variant, in the exchange line, the exhaust from the turbine is sent back to the exchange line to cool against the waste nitrogen (and possibly the purer nitrogen coming from the second column) and against oxygen.
Selon un objet de l’invention, il est prévu un procédé de séparation d’air par distillation cryogénique dans un système de colonnes comprenant une première colonne opérant à une première pression et une deuxième colonne opérant à une deuxième pression plus basse que la première pression, la tête de la première colonne étant thermiquement reliée à la cuve de la deuxième colonne dans lequel :According to one object of the invention, there is provided a process for separating air by cryogenic distillation in a system of columns comprising a first column operating at a first pressure and a second column operating at a second pressure lower than the first pressure , the top of the first column being thermally connected to the bottom of the second column wherein:
  1. un débit d’air épuré en eau et en dioxyde de carbone est refroidi dans un échangeur de chaleur et est envoyé à la première colonne sous forme gazeusea flow of air purified of water and carbon dioxide is cooled in a heat exchanger and is sent to the first column in gaseous form
  2. un liquide enrichi en oxygène est soutiré de la cuve de la première colonne et envoyé à la deuxième colonne après avoir été sousrefroidi dans un sousrefroidisseuran oxygen-enriched liquid is withdrawn from the bottom of the first column and sent to the second column after being subcooled in a subcooler
  3. un liquide enrichi en azote est soutiré de la partie supérieure de la première colonne et envoyé à la deuxième colonne après avoir été sousrefroidi dans le sousrefroidisseurnitrogen-enriched liquid is withdrawn from the top of the first column and sent to the second column after being subcooled in the subcooler
  4. un gaz riche en azote et un fluide riche en oxygène sont soutirés de la deuxième colonne et se réchauffent dans l’échangeur de chaleura nitrogen-rich gas and an oxygen-rich fluid are withdrawn from the second column and warmed up in the heat exchanger
  5. l’échangeur de chaleur est disposé en dessous de la première colonne qui est elle-même disposée en dessous de la deuxième colonne, le débit d’air se refroidissant dans l’échangeur en circulant vers le haut caractérisé en ce quethe heat exchanger is arranged below the first column which is itself arranged below the second column, the flow of air cooling in the exchanger by circulating upwards characterized in that
  6. la température T1 à laquelle le débit d’air sort de l’échangeur de chaleur et rentre dans la première colonne est supérieure d’au moins 1°C, de préférence d’au moins 2°C à la température de rosée du débit d’air.the temperature T1 at which the air flow leaves the heat exchanger and enters the first column is higher by at least 1°C, preferably by at least 2°C, than the dew temperature of the flow d 'air.
Selon d’autres aspects facultatifs :According to other optional aspects:
  • un autre débit d’air épuré en eau et en dioxyde de carbone est refroidi dans l’échangeur de chaleur, sort de l’échangeur de chaleur à une température T2, est détendu dans une turbine, est renvoyé à l’échangeur de chaleur à une température T3 et est refroidi dans l’échangeur jusqu’à une température T4 avant d’être envoyé à la deuxième colonne sous forme gazeuse, la température T2 étant supérieure à T1.another flow of air purified of water and carbon dioxide is cooled in the heat exchanger, leaves the heat exchanger at a temperature T2, is expanded in a turbine, is returned to the heat exchanger at a temperature T3 and is cooled in the exchanger to a temperature T4 before being sent to the second column in gaseous form, the temperature T2 being higher than T1.
  • T4 est supérieure d’au moins 1°C, de préférence d’au moins 2°C à la température de rosée du débit détenduT4 is at least 1°C, preferably at least 2°C higher than the dew temperature of the expanded flow
  • T4 est supérieure, inférieure ou égale à T1T4 is greater than, less than, or equal to T1
  • un autre débit d’air épuré en eau et en dioxyde de carbone substantiellement à la deuxième pression est refroidi dans l’échangeur de chaleur jusqu’à une température supérieure d’au moins 1°C, de préférence d’au moins 2°C à sa température de rosée et envoyé à la deuxième colonne sans avoir été détendu.another flow of air purified of water and carbon dioxide substantially at the second pressure is cooled in the heat exchanger to a temperature higher by at least 1°C, preferably by at least 2°C at its dew temperature and sent to the second column without having been relaxed.
  • le liquide enrichi en oxygène est refroidi dans le sousrefroidisseur jusqu’à une température inférieure à celle à laquelle le liquide enrichi en azote rentre dans le sousrefroidisseur, les deux liquides sousrefroidis étant détendus chacun dans une vanne respective avant d’être envoyés à la deuxième colonne.the oxygen-enriched liquid is cooled in the subcooler to a temperature below that at which the nitrogen-enriched liquid enters the subcooler, the two subcooled liquids each being expanded in a respective valve before being sent to the second column .
  • la première colonne et éventuellement la deuxième colonne sont alimentées en air uniquement par des débits d’air gazeuxthe first column and possibly the second column are supplied with air only by gaseous air flows
  • la première colonne et la deuxième colonne ne produisent que des débits gazeux comme produits finaux.the first column and the second column only produce gas streams as final products.
  • l’échangeur de chaleur et le sous-refroidisseur sont constitués par un seul corps de plaques d’aluminium brasées ensemble.the heat exchanger and the sub-cooler are made of a single body of aluminum plates brazed together.
  • la perte de charge du débit d’air épuré en eau et en dioxyde de carbone destiné à la première colonne en se refroidissant dans l’échangeur de chaleur ne dépasse pas 120 mbar, voire 100 mbar.the pressure drop of the air flow purified of water and carbon dioxide intended for the first column by cooling in the heat exchanger does not exceed 120 mbar, or even 100 mbar.
  • un débit de liquide est soutiré à un niveau intermédiaire de la première colonne, est sousrefroidi dans le sousrefroidisseur jusqu’à une température intermédiaire entre celle de sortie de sousrefroidisseur du liquide enrichi en oxygène et celle de sortie de sousrefroidisseur du liquide enrichi en azote et envoyé à la deuxième colonne.a flow of liquid is withdrawn from an intermediate level of the first column, is subcooled in the subcooler to an intermediate temperature between that of the subcooler outlet of the oxygen-enriched liquid and that of the subcooler outlet of the nitrogen-enriched liquid and sent in the second column.
L’invention sera décrite de manière plus détaillée en se référant à la figure.The invention will be described in more detail with reference to the figure.
représente un procédé selon l’invention. represents a process according to the invention.
Le procédé utilise un système de colonnes comprenant une première colonne K1 opérant à une première pression et une deuxième colonne K2 opérant à une deuxième pression plus basse que la première pression. La première colonne K1 est thermiquement reliée à la deuxième colonne K2 par un vaporiseur de cuve de la deuxième colonne. The method uses a system of columns comprising a first column K1 operating at a first pressure and a second column K2 operating at a second pressure lower than the first pressure. The first column K1 is thermally connected to the second column K2 by a bottom vaporizer of the second column.
La première colonne est disposée en dessous de la deuxième colonne K2 et la tête de la première colonne étant thermiquement reliée à la cuve de la deuxième colonne. Un échangeur de chaleur E à plaques aluminium brasées est disposé en dessous de la première colonne K1.The first column is arranged below the second column K2 and the head of the first column being thermally connected to the bottom of the second column. A heat exchanger E with brazed aluminum plates is arranged below the first column K1.
Un débit d’air 1 est comprimé par le compresseur 3 à la première pression, refroidi par le refroidisseur 5 et épuré en eau et en dioxyde de carbone dans l’unité d’épuration 7. Pour se refroidir, l’air est envoyé au bout chaud de l’échangeur E en bas de l’échangeur et monte vers le haut, puisque le bout froid de l’échangeur se trouve en haut.A flow of air 1 is compressed by the compressor 3 to the first pressure, cooled by the cooler 5 and purified of water and carbon dioxide in the purification unit 7. To cool, the air is sent to the hot end of exchanger E at the bottom of the exchanger and rises upwards, since the cold end of the exchanger is at the top.
L’air épuré 9 se refroidit dans l’échangeur de chaleur E et est divisé en deux à une température T2 qui est une température intermédiaire de l’échangeur E. Une partie 11 de l’air poursuit son refroidissement dans l’échangeur jusqu’à une température T1 supérieure d’au moins 1°C, de préférence d’au moins 2°C à la température de rosée de la fraction d’air 9.The purified air 9 cools in the heat exchanger E and is divided into two at a temperature T2 which is an intermediate temperature of the exchanger E. Part 11 of the air continues to cool in the exchanger until at a temperature T1 higher by at least 1°C, preferably by at least 2°C, than the dew point temperature of the air fraction 9.
A cette température T1, elle sort de l’échangeur E et est envoyée en cuve de la colonne K1 comme débit gazeux d’alimentation.At this temperature T1, it leaves exchanger E and is sent to the bottom of column K1 as a gas feed flow.
La perte de charge de l’air 9, 11 traversant l’échangeur E ne dépasse pas 120, voire 100 mbar.The pressure drop of the air 9, 11 crossing the exchanger E does not exceed 120, or even 100 mbar.
L’air se sépare dans la première colonne pour former un liquide 10 enrichi en oxygène en cuve et un liquide enrichi en azote 12 en tête. Le liquide 10 et le liquide 12 sont envoyés à un sousrefroidisseur S où se réchauffe au moins un débit d’azote gazeux 15 provenant de la deuxième colonne K2. Le liquide 10 rentre dans le sous-refroidisseur au bout chaud de celui-ci et est refroidi jusqu’à une température inférieure à celle à laquelle le liquide 12 rentre dans le sousrefroidisseur S. Le liquide 12 sort du bout froid du sous-refroidisseur. Le liquide sousrefroidi 10 et le liquide sous refroidi 12 sont chacun détendu dans une vanne et le liquide 10 est envoyé à un niveau de la deuxième colonne K2 et le liquide 12 est envoyé à un niveau de la deuxième colonne K2 supérieur à celui auquel rentre le liquide 10. Ainsi le sousrefroidisseur comprend une section où les liquides 10 et 12 se refroidissent tous deux contre l’azote 15. Le sous-refroidisseur S peut être placé à côté de la colonne K1 et avoir son bout chaud disposé vers le bas.The air separates in the first column to form an oxygen-enriched liquid 10 at the bottom and a nitrogen-enriched liquid 12 at the top. The liquid 10 and the liquid 12 are sent to a subcooler S where at least a flow of gaseous nitrogen 15 coming from the second column K2 is heated. Liquid 10 enters the subcooler at the hot end of it and is cooled to a temperature below that at which liquid 12 enters subcooler S. Liquid 12 exits the cold end of the subcooler. The subcooled liquid 10 and the subcooled liquid 12 are each expanded in a valve and the liquid 10 is sent to a level of the second column K2 and the liquid 12 is sent to a level of the second column K2 higher than that at which the liquid 10. Thus the subcooler comprises a section where the liquids 10 and 12 are both cooled against the nitrogen 15. The subcooler S can be placed next to the column K1 and have its hot end disposed downwards.
Une partie 13 de l’air à la température T2 est détendue dans une turbine T sans avoir été comprimée en aval de l’échangeur, est renvoyée à l’échangeur de chaleur E à une température T3 et est refroidie dans l’échangeur E à une température T4 avant d’être envoyé à la deuxième colonne sous forme gazeuse, la température T2 étant supérieure à T1. T4 peut être supérieure, égale ou inférieure à T1. T4 est supérieure d’au moins 1°C, de préférence d’au moins 2°C à la température de rosée du débit détendu 13. La partie 13 sort au bout froid de l’échangeur E et est envoyée directement à la deuxième colonne K2 sous forme gazeuse à un niveau en dessous de l’arrivée du liquide détendu 10. Comme pour l’air 11, la partie 13 se refroidit dans l’échangeur en allant vers le haut. Part 13 of the air at temperature T2 is expanded in a turbine T without having been compressed downstream of the exchanger, is sent back to the heat exchanger E at a temperature T3 and is cooled in the exchanger E at a temperature T4 before being sent to the second column in gaseous form, the temperature T2 being higher than T1. T4 can be greater than, equal to, or less than T1. T4 is higher by at least 1°C, preferably by at least 2°C, than the dew temperature of the expanded flow 13. Part 13 leaves the cold end of the exchanger E and is sent directly to the second column K2 in gaseous form at a level below the arrival of the expanded liquid 10. As for the air 11, the part 13 cools in the exchanger going upwards.
La colonne K2 sépare les débits 10 et 12 par distillation pour former un gaz 15 enrichi en azote en tête de colonne et un gaz enrichi en oxygène 17 en bas de la colonne. Le gaz 17 se réchauffe en descendant dans l’échangeur E et ensuite sert de produit du procédé.Column K2 separates streams 10 and 12 by distillation to form a nitrogen-enriched gas 15 at the top of the column and an oxygen-enriched gas 17 at the bottom of the column. Gas 17 heats up as it descends through exchanger E and then serves as the product of the process.
Le gaz 15 réchauffé dans le sousrefroidisseur et ensuite en descendant dans l’échangeur E est divisé en deux, une partie servant à régénérer l’épuration 7 et le reste servant de produit ou de résiduaire.The gas 15 reheated in the subcooler and then descending in the exchanger E is divided into two, a part serving to regenerate the purification 7 and the rest serving as product or residual.
Ici la première colonne K1 est alimentée en air uniquement par des débits d’air gazeux.Here the first column K1 is supplied with air only by gaseous air flows.
La deuxième colonne K2 pourrait aussi est alimentée en air, dans ce cas ce serait une alimentation en air gazeux exclusivement.The second column K2 could also be supplied with air, in this case it would be a supply of gaseous air exclusively.
Le procédé ne produit que des débits gazeux 15, 17 comme produits finaux. La purge du condenseur de cuve de la colonne K2 n’est pas considérée comme un produit final.The process only produces gas streams 15, 17 as end products. The purging of the K2 column bottom condenser is not considered an end product.
Le sous-refroidisseur S peut être intégré à la ligne d’échange principale E. Cela permet d’encore mieux optimiser l’épuisement des fluides froids 15, 17 issus de la distillation (éventuellement aussi de l’azote pur provenant de la deuxième colonne K2) pour refroidir le plus possible les liquides riche et pauvre 10, 12 et l’air à la deuxième pression issu d’une turbine d’insufflation. The sub-cooler S can be integrated into the main exchange line E. This makes it possible to further optimize the exhaustion of the cold fluids 15, 17 resulting from the distillation (possibly also pure nitrogen from the second column K2) to cool as much as possible the rich and lean liquids 10, 12 and the air at the second pressure coming from an insufflation turbine.
En plus des fluides 15, 17, un débit d’air liquéfié soutiré de la colonne K1 peut être sousrefroidi dans le sousrefroidisseur S avant d’être envoyé à la colonne K2.In addition to fluids 15, 17, a flow of liquefied air withdrawn from column K1 can be subcooled in subcooler S before being sent to column K2.
montre une possibilité pour l’alimentation du procédé en air. D’autres variantes sont également possibles, par exemple celle de FR3090831, utilisant un système de colonnes comprenant une première colonne opérant à une première pression et une deuxième colonne opérant à une deuxième pression plus basse que la première colonne, la tête de la première colonne étant thermiquement reliée à la cuve de la deuxième colonne. shows a possibility for supplying the process with air. Other variants are also possible, for example that of FR3090831, using a column system comprising a first column operating at a first pressure and a second column operating at a second pressure lower than the first column, the head of the first column being thermally connected to the bottom of the second column.
Dans ce cas, trois débits d’air sont utilisés. L’air est comprimé jusqu’à la pression de la deuxième colonne et puis épuré. Ensuite l’air est divisé en deux, une partie étant refroidi à la pression de la deuxième colonne et envoyée à la deuxième colonne en montant dans l’échangeur. La température finale en sortant de l’échangeur sera est supérieure d’au moins 1°C, de préférence d’au moins 2°C à sa température de rosée à la deuxième pression.In this case, three airflows are used. The air is compressed to the pressure of the second column and then purified. Then the air is divided in two, a part being cooled to the pressure of the second column and sent to the second column by rising in the exchanger. The final temperature leaving the exchanger will be higher by at least 1°C, preferably by at least 2°C, than its dew temperature at the second pressure.
L’autre partie est surpressée à la pression de la première colonne. Une fraction de cette partie se refroidit dans l’échangeur en montant et en sort à une température T1 supérieure d’au moins 1°C, de préférence d’au moins 2°C à la température de rosée de la fraction d’air.The other part is boosted to the pressure of the first column. A fraction of this part is cooled in the exchanger by rising and leaving it at a temperature T1 higher by at least 1°C, preferably by at least 2°C above the dew point temperature of the air fraction.
Le reste de la partie est refroidi dans l’échangeur jusqu’à une température T2, détendu dans une turbine d’insufflation, renvoyé dans l’échangeur à une température T3, refroidi jusqu’au bout froid de l’échangeur de chaleur à une température T4 et envoyé à la deuxième colonne. T4 est supérieure d’au moins 1°C, de préférence d’au moins 2°C à la température de rosée.The rest of the part is cooled in the exchanger to a temperature T2, expanded in a blowing turbine, returned to the exchanger to a temperature T3, cooled down to the cold end of the heat exchanger to a temperature T4 and sent to the second column. T4 is at least 1°C, preferably at least 2°C above the dew temperature.

Claims (14)

  1. Procédé de séparation d’air par distillation cryogénique dans un système de colonnes comprenant une première colonne (K1) opérant à une première pression et une deuxième colonne (K2) opérant à une deuxième pression plus basse que la première pression, la tête de la première colonne étant thermiquement reliée à la cuve de la deuxième colonne dans lequel :
    1. un débit d’air (11) épuré en eau et en dioxyde de carbone est refroidi dans un échangeur de chaleur (E) et est envoyé à la première colonne sous forme gazeuse
    2. un liquide enrichi en oxygène (10) est soutiré de la cuve de la première colonne et envoyé à la deuxième colonne après avoir été sousrefroidi dans un sousrefroidisseur (S)
    3. un liquide enrichi en azote (12) est soutiré de la partie supérieure de la première colonne et envoyé à la deuxième colonne après avoir été sousrefroidi dans le sousrefroidisseur
    4. un gaz riche en azote (15) et un fluide riche en oxygène (17) sont soutirés de la deuxième colonne et se réchauffent dans l’échangeur de chaleur
    5. l’échangeur de chaleur est disposé en dessous de la première colonne qui est elle-même disposée en dessous de la deuxième colonne, le débit d’air se refroidissant dans l’échangeur en circulant vers le haut caractérisé en ce que
    6. la température T1 à laquelle le débit d’air (11) sort de l’échangeur de chaleur et rentre dans la première colonne est supérieure d’au moins 1°C à la température de rosée du débit d’air.
    Process for the separation of air by cryogenic distillation in a column system comprising a first column (K1) operating at a first pressure and a second column (K2) operating at a second pressure lower than the first pressure, the head of the first column being thermally connected to the tank of the second column in which:
    1. an air flow (11) purified of water and carbon dioxide is cooled in a heat exchanger (E) and is sent to the first column in gaseous form
    2. an oxygen-enriched liquid (10) is withdrawn from the bottom of the first column and sent to the second column after being subcooled in a subcooler (S)
    3. nitrogen-enriched liquid (12) is withdrawn from the top of the first column and sent to the second column after being subcooled in the subcooler
    4. a nitrogen-rich gas (15) and an oxygen-rich fluid (17) are withdrawn from the second column and are heated in the heat exchanger
    5. the heat exchanger is arranged below the first column which is itself arranged below the second column, the flow of air cooling in the exchanger by circulating upwards characterized in that
    6. the temperature T1 at which the airflow (11) exits the heat exchanger and enters the first column is at least 1°C higher than the dew temperature of the airflow.
  2. Procédé selon la revendication 1 dans lequel la température T1 à laquelle le débit d’air (11) sort de l’échangeur de chaleur et rentre dans la première colonne est supérieure d’au moins 2°C à la température de rosée du débit d’airProcess according to Claim 1, in which the temperature T1 at which the air flow (11) leaves the heat exchanger and enters the first column is higher by at least 2°C than the dew point temperature of the air flow. 'air
  3. Procédé selon la revendication 1 ou 2 dans lequel un autre débit d’air (13) épuré en eau et en dioxyde de carbone est refroidi dans l’échangeur de chaleur (E), sort de l’échangeur de chaleur à une température T2, est détendu dans une turbine (T), est renvoyé à l’échangeur de chaleur à une température T3 et est refroidi dans l’échangeur jusqu’à une température T4 avant d’être envoyé à la deuxième colonne (K2) sous forme gazeuse, la température T2 étant supérieure à T1.Process according to Claim 1 or 2, in which another flow of air (13) purified of water and carbon dioxide is cooled in the heat exchanger (E), leaves the heat exchanger at a temperature T2, is expanded in a turbine (T), is returned to the heat exchanger at a temperature T3 and is cooled in the exchanger to a temperature T4 before being sent to the second column (K2) in gaseous form, the temperature T2 being higher than T1.
  4. Procédé selon la revendication 3 dans lequel T4 est supérieure d’au moins 1°C à la température de rosée du débit détendu (13).Process according to Claim 3, in which T4 is higher by at least 1°C than the dew point temperature of the expanded flow (13).
  5. Procédé selon la revendication 4 dans lequel T4 est supérieure d’au moins 2°C à la température de rosée du débit détendu (13).Process according to Claim 4, in which T4 is at least 2°C higher than the dew temperature of the expanded flow (13).
  6. Procédé selon la revendication 1 dans lequel un autre débit d’air épuré en eau et en dioxyde de carbone substantiellement à la deuxième pression est refroidi dans l’échangeur de chaleur jusqu’à une température supérieure d’au moins 1°C à sa température de rosée et envoyé à la deuxième colonne sans avoir été détendu.Process according to Claim 1, in which a further flow of air purified of water and carbon dioxide at substantially the second pressure is cooled in the heat exchanger to a temperature at least 1°C higher than its temperature. of dew and sent to the second column without having been relaxed.
  7. Procédé selon la revendication 6 dans lequel un autre débit d’air épuré en eau et en dioxyde de carbone substantiellement à la deuxième pression est refroidi dans l’échangeur de chaleur jusqu’à une température supérieure d’au moins 2°C à sa température de rosée et envoyé à la deuxième colonne sans avoir été détendu.Process according to Claim 6, in which a further flow of air purified of water and carbon dioxide at substantially the second pressure is cooled in the heat exchanger to a temperature at least 2°C higher than its temperature. of dew and sent to the second column without having been relaxed.
  8. Procédé selon l’une des revendications précédentes dans lequel le liquide enrichi en oxygène (10) est refroidi dans le sousrefroidisseur jusqu’à une température inférieure à celle à laquelle le liquide enrichi en azote rentre dans le sousrefroidisseur, les deux liquides sousrefroidis étant détendus chacun dans une vanne respective avant d’être envoyés à la deuxième colonne (K2).Process according to one of the preceding claims, in which the oxygen-enriched liquid (10) is cooled in the subcooler to a temperature below that at which the nitrogen-enriched liquid enters the subcooler, the two subcooled liquids each being expanded in a respective valve before being sent to the second column (K2).
  9. Procédé selon l’une des revendications précédentes dans lequel la première colonne (K1) et éventuellement la deuxième colonne (K2) sont alimentées en air uniquement par des débits d’air gazeux.Process according to one of the preceding claims, in which the first column (K1) and optionally the second column (K2) are supplied with air solely by gaseous air flows.
  10. Procédé selon l’une des revendications précédentes dans lequel la première colonne (K1) et la deuxième colonne (K2) ne produisent que des débits gazeux comme produits finaux. Process according to one of the preceding claims, in which the first column (K1) and the second column (K2) only produce gas streams as end products.
  11. Procédé selon l’une des revendications précédentes dans lequel l’échangeur de chaleur (E) et le sous-refroidisseur (S) sont constitués par un seul corps de plaques d’aluminium brasées ensemble.Process according to one of the preceding claims, in which the heat exchanger (E) and the sub-cooler (S) consist of a single body of aluminum plates brazed together.
  12. Procédé selon l’une des revendications précédentes dans lequel la perte de charge du débit d’air (11) épuré en eau et en dioxyde de carbone destiné à la première colonne en se refroidissant dans l’échangeur de chaleur ne dépasse pas 120 mbar.Method according to one of the preceding claims, in which the pressure drop of the air flow (11) purified of water and carbon dioxide intended for the first column while cooling in the heat exchanger does not exceed 120 mbar.
  13. Procédé selon la revendication 12 dans lequel la perte de charge du débit d’air (11) épuré en eau et en dioxyde de carbone destiné à la première colonne en se refroidissant dans l’échangeur de chaleur ne dépasse pas 100 mbar.Process according to Claim 12, in which the pressure drop of the flow of air (11) purified of water and carbon dioxide intended for the first column while cooling in the heat exchanger does not exceed 100 mbar.
  14. Procédé selon l’une des revendications précédentes un débit de liquide est soutiré à un niveau intermédiaire de la première colonne (K1), est sousrefroidi dans le sousrefroidisseur (S) jusqu’à une température intermédiaire entre celle de sortie de sousrefroidisseur du liquide enrichi en oxygène et celle de sortie de sousrefroidisseur du liquide enrichi en azote et envoyé à la deuxième colonne (K2).Method according to one of the preceding claims, a flow of liquid is withdrawn from an intermediate level of the first column (K1), is subcooled in the subcooler (S) to an intermediate temperature between that of the outlet from the subcooler of the liquid enriched in oxygen and that of the subcooler outlet of the liquid enriched in nitrogen and sent to the second column (K2).
PCT/EP2022/053473 2021-02-18 2022-02-14 Method for separating air by cryogenic distillation WO2022175194A1 (en)

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JP2023547532A JP2024508391A (en) 2021-02-18 2022-02-14 How to separate air by cryogenic distillation
US18/277,794 US20240230222A9 (en) 2021-02-18 2022-02-14 Method for separating air by cryogenic distillation
KR1020237027186A KR20230147063A (en) 2021-02-18 2022-02-14 Method for separating air by cryogenic distillation
CA3206388A CA3206388A1 (en) 2021-02-18 2022-02-14 Method for separating air by cryogenic distillation
CN202280013695.XA CN116848365A (en) 2021-02-18 2022-02-14 Method for separating air by cryogenic distillation
EP22709278.0A EP4295096A1 (en) 2021-02-18 2022-02-14 Method for separating air by cryogenic distillation

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FR2101594A FR3119884B1 (en) 2021-02-18 2021-02-18 Air separation process by cryogenic distillation
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EP0342436A2 (en) * 1988-05-20 1989-11-23 Linde Aktiengesellschaft Low-temperature air separation process
EP1319912A1 (en) * 2001-12-14 2003-06-18 Linde Aktiengesellschaft Device and process for obtaining gaseous oxygen under high pressure
WO2011116981A2 (en) * 2010-03-26 2011-09-29 Linde Aktiengesellschaft Device for the cryogenic separation of air
WO2019126927A1 (en) 2017-12-25 2019-07-04 L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude Single packaged air separation apparatus with reverse main heat exchanger
WO2020128205A1 (en) * 2018-12-21 2020-06-25 L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude Apparatus and method for separating air by cryogenic distillation

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EP0342436A2 (en) * 1988-05-20 1989-11-23 Linde Aktiengesellschaft Low-temperature air separation process
EP1319912A1 (en) * 2001-12-14 2003-06-18 Linde Aktiengesellschaft Device and process for obtaining gaseous oxygen under high pressure
WO2011116981A2 (en) * 2010-03-26 2011-09-29 Linde Aktiengesellschaft Device for the cryogenic separation of air
WO2019126927A1 (en) 2017-12-25 2019-07-04 L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude Single packaged air separation apparatus with reverse main heat exchanger
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KR20230147063A (en) 2023-10-20
JP2024508391A (en) 2024-02-27
US20240133624A1 (en) 2024-04-25
CA3206388A1 (en) 2022-08-25
CN116848365A (en) 2023-10-03
FR3119884B1 (en) 2022-12-30
FR3119884A1 (en) 2022-08-19

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