WO2020128205A1 - Apparatus and method for separating air by cryogenic distillation - Google Patents

Apparatus and method for separating air by cryogenic distillation Download PDF

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Publication number
WO2020128205A1
WO2020128205A1 PCT/FR2019/052934 FR2019052934W WO2020128205A1 WO 2020128205 A1 WO2020128205 A1 WO 2020128205A1 FR 2019052934 W FR2019052934 W FR 2019052934W WO 2020128205 A1 WO2020128205 A1 WO 2020128205A1
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WIPO (PCT)
Prior art keywords
column
flow
pressure
air
heat exchanger
Prior art date
Application number
PCT/FR2019/052934
Other languages
French (fr)
Inventor
Benoît 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.)
Filing date
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 JP2021535172A priority Critical patent/JP7451532B2/en
Priority to CA3122855A priority patent/CA3122855A1/en
Priority to US17/416,782 priority patent/US20220074656A1/en
Priority to BR112021011589-7A priority patent/BR112021011589A2/en
Priority to CN201980084384.0A priority patent/CN113242952B/en
Priority to EP19868211.4A priority patent/EP3899389A1/en
Priority to AU2019408677A priority patent/AU2019408677A1/en
Publication of WO2020128205A1 publication Critical patent/WO2020128205A1/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04006—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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04151—Purification and (pre-)cooling of the feed air; recuperative heat-exchange with product streams
    • F25J3/04187—Cooling of the purified feed air by recuperative heat-exchange; Heat-exchange with product streams
    • F25J3/04193—Division of the main heat exchange line in consecutive sections having different functions
    • F25J3/04206—Division of the main heat exchange line in consecutive sections having different functions including a so-called "auxiliary vaporiser" for vaporising and producing a gaseous product
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04151—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
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04254—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using the cold stored in external cryogenic fluids
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04284—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams
    • F25J3/0429—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams of feed air, e.g. used as waste or product air or expanded into an auxiliary column
    • F25J3/04303—Lachmann expansion, i.e. expanded into oxygen producing or low pressure column
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04284—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
    • F25J3/04309—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 nitrogen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04406—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using a dual pressure main column system
    • F25J3/04412—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
    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/42—Nitrogen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/50—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
    • F25J2215/00—Processes characterised by the type or other details of the product stream
    • F25J2215/50—Oxygen or special cases, e.g. isotope-mixtures or low purity O2
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2245/00—Processes or apparatus involving steps for recycling of process streams
    • F25J2245/40—Processes or apparatus involving steps for recycling of process streams the recycled stream being air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2250/00—Details related to the use of reboiler-condensers
    • F25J2250/30—External or auxiliary boiler-condenser in general, e.g. without a specified fluid or one fluid is not a primary air component or an intermediate fluid
    • F25J2250/40—One fluid being air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2250/00—Details related to the use of reboiler-condensers
    • F25J2250/30—External or auxiliary boiler-condenser in general, e.g. without a specified fluid or one fluid is not a primary air component or an intermediate fluid
    • F25J2250/50—One fluid being oxygen
    • 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 an apparatus and a method for separating air by cryogenic distillation.
  • an air separation device comprising a double column with a first column operating at a first pressure and a second column operating at a second pressure, lower than the first pressure.
  • the head of the first column produces a gas which condenses in a reboiler of the second column.
  • Air cleaning is generally carried out at a pressure equal to or greater than that of the first pressure. This makes it possible to reduce the volume of the purification unit.
  • JPH1 1063810 and EP1050730 are similar to US5934105.
  • the air flow going to the first column is approximately 66% of the total purified flow, for example to produce 96% oxygen. This means that 34% of the air flow must be passed at a relatively low pressure in the turbine. According to the present invention, between 6 and 8% of the air is expanded in an air turbine, therefore the turbine according to the prior art is at least 4 to 5 times larger due to the volume flow.
  • the invention provides a process which consumes 1% less energy (2% less if we consider a turbine efficiency reduced by 5% pt) compared to the prior art (for example, according to EP1050730); according to the method of EP1050730, the purification is carried out at a pressure between the first and the second pressure.
  • the expansion rate of the EP1050730 process is low, between 1: 2: 1 and 3.8: 1, preferably between 1: 4: 1 and 2.5: 1, while conventional cryogenic turbines are within a range of relaxation ratio between 4: 1 and 10: 1.
  • the invention uses an expansion rate which remains at the lower limit of this range, thus avoiding having a substantially degraded turbine efficiency.
  • the inlet pressure of the purification unit is typically 2.5 bara (instead of approximately 1.3 bara according to the invention).
  • This process uses a first compressor with several, typically two, stages with cooling between two stages.
  • the compressor which compresses all the air has a single stage, therefore no cooling between two stages.
  • US5666824 describes a method according to the preamble of claim 1 but in which the first flow is at least partially condensed in an intermediate condenser of the second column. If a gas is formed, it is itself condensed in another intermediate condenser of the second column and the liquid thus formed is sent to the head of the second column. Thus the first flow is not sent directly to the distillation.
  • WO2013 / 014252 describes in FIG. 6 a process in which a first part of the air is cooled to its dew point in a heat exchanger where an expanded air flow in a turbine is also cooled to its dew point. This is impossible since the residual nitrogen which cools the air flows has already been heated in a sub-cooler. In this case, the nitrogen is too hot to cool the air flows to their dew point and the air flows will be cooled at most to a temperature around 10 ° C above the dew point.
  • an air separation device comprising a double column with a first column operating at a first pressure and a second column operating at a second pressure, lower than the first pressure, the second column having a tank reboiler, means for sending a nitrogen-enriched gas from the head of the first column to the tank reboiler and means for sending at least part of the condensed nitrogen enriched gas from the tank reboiler to the head of the first column, a heat exchanger, a purification unit, means for sending air to the purification unit at a third pressure higher than atmospheric pressure by at most 1 bar, a pipe for sending a first flow of purified air in the purification unit at the heat exchanger at a fourth pressure greater than the second pressure by at most 1 bar, a line for introducing the first flow of cooled purified air into the heat exchanger heat in the second column to separate therefrom, a booster, a pipe for sending a second flow of purified air in the purification unit to the booster, a
  • the means for producing frigories include at least one expansion turbine for part of the second flow and / or one expansion turbine for a gas rich in nitrogen coming from the first column and / or means for sending a cryogenic liquid from a source external to the double column.
  • the means for sending air to the purification unit at the third pressure do not include any compression means apart from a single-stage compressor.
  • the device does not include any means of compressing the first flow.
  • a first flow of purified air is sent into the purification unit to a heat exchanger at a fourth pressure greater than the second pressure by at most 1 bar, iv) the first flow of cooled purified air is sent into the heat exchanger to the second column, without having relaxed it,
  • a second purified air flow is boosted at a fifth pressure between the first pressure and 1 bar above the first pressure, at least part of the second flow is sent at the fifth pressure to the heat exchanger and at least part of the second flow is sent to the first column in gaseous form,
  • an oxygen-enriched gas or a nitrogen-enriched gas is drawn off from the double column and it is heated in the heat exchanger to form a product of the process characterized in that the first air flow is sent directly to the second column to separate there without having been condensed in a condenser.
  • the part of the air expanded in the turbine represents between 6 and 15% vol, preferably between 6 and 8% of the purified air.
  • the oxygen-enriched gas contains at least 80 mol% oxygen.
  • the oxygen-enriched gas contains at least 90 mol% of oxygen.
  • the oxygen-enriched gas contains less than 98% mol of oxygen.
  • the first flow represents between 20 and 30% vol of the purified air flow.
  • the second flow represents between 70 and 80% vol of the purified air flow.
  • a gas enriched in oxygen and / or a gas enriched in nitrogen is withdrawn from the double column and it (s) is heated in the heat exchanger to form a product of the process by introducing it or introducing them at the cold end of the heat exchanger.
  • the oxygen-enriched liquid is pressurized before vaporizing it either in a dedicated vaporizer or in the heat exchanger.
  • the oxygen-enriched liquid is vaporized by heat exchange with part of the second flow or with a third flow of pressurized air at a pressure greater than the fifth pressure.
  • FIG. 1 represents a method of air separation by cryogenic distillation according to the invention.
  • An air separation apparatus by cryogenic distillation comprises a double column with a first column K3 operating at a first pressure and a second column K4 operating at a second pressure, lower than the first pressure, the second column having a tank reboiler M.
  • the second column K4 does not contain an intermediate condenser.
  • the first pressure is 4.5 bara and the second pressure is 1.13 bara.
  • a gas enriched in nitrogen is sent from the head of the first column to the tank reboiler M and at least part of the gas enriched in condensed nitrogen from the tank reboiler is sent to the head of the first column.
  • Air at atmospheric pressure is filtered in a filter A, compressed by a blower B having a single stage at a pressure at most 1 bar, preferably at most 0.5 bar, above atmospheric pressure, cooled by a cooling means C and purified with water and carbon dioxide in a single purification unit D in which the air 4 returns to a third pressure higher than atmospheric pressure by at most 1 bar, preferably of at most 0.5 bar.
  • the purification unit includes two adsorbent beds used alternately to purify the air, one bed purifying the air while the other is regenerated.
  • Air 8 is neither compressed nor expanded and is at a pressure which differs from the second pressure by a pressure equal to the pressure losses in the pipes and the heat exchanger G.
  • the first flow 8 represents between 20 and 30% vol of the flow 4 and the second flow 6 represents between 70 and 80% vol of the flow 4.
  • the air 8 is sent directly from the purification unit to the second column K2 to be separated there, returning to the column in entirely gaseous form.
  • the air 8 cools in the heat exchanger G to a temperature at least 5 ° C above its dew point.
  • the flow 6 is boosted in a booster E, cooled in a cooler F and sent to the heat exchanger G.
  • the booster E boosts the air 6 to a fifth pressure between the first pressure and 1 bar above the first press.
  • the air 6 is divided into two parts 30, 32 at an intermediate level of the exchanger.
  • the air 30 leaves the exchanger at an intermediate temperature thereof, for example -125 ° C, is expanded in a turbine 28 until the second pressure and returns in gaseous form, mixed with the flow 8, to be separated in the second column K4.
  • the flow 30 can represent between 6 and 15% vol, preferably between 6 and 8% of the air 4.
  • the air 32 cools down to the cold end of the exchanger G and is sent to the tank of the first column K3 in essentially gaseous form in order to be separated there.
  • the air 8 cools in the heat exchanger G to a temperature at least 5 ° C above its dew point.
  • a liquid flow enriched with oxygen 34 is withdrawn from the tank of the first column and sent to a level of the second column which is above the air inlet.
  • the air can enter the second column at the same level as that of the arrival of the liquid 34.
  • the expanded liquid 34 can be separated in a phase separator: the liquid from the phase separator is sent to column K4 and the vapor phase can be mixed with the air inlet 8.30 in column K4.
  • a flow of liquid nitrogen 35 is withdrawn from the head of the first column and sent to the head of the second column.
  • Nitrogen gas 36 is drawn off at the head of the second column K4 and is heated in the sub-cooler S and then in the exchanger G. Part 14 of this gas is used to regenerate the purification unit D.
  • Gaseous oxygen 29 is withdrawn from the tank of the second column K4.
  • the flow 29 preferably contains at least 80 mol% oxygen, or even at least 90 mol% oxygen, but preferably less than 98 mol% oxygen.
  • the process produces no liquid flow as the final product.
  • the process produces no liquid flow to vaporize to form a final gaseous product, possibly under pressure. It is however possible to produce a small amount of final gaseous product in this way, which can optionally be mixed with the main gaseous product.
  • the air 8 and / or the air 30 may be sub-cooled is in the sub-cooler S and then be introduced into the second column K4. Otherwise, the mixture of flows 8 and 30 can be sub-cooled in the sub-cooler S and then be introduced into the second column K4.
  • the flow 29 is a flow of gaseous oxygen which heats up in the heat exchanger G from the cold end of the exchanger G.
  • the flow 29 can be a flow of rich liquid in pressurized oxygen at a pressure above that of the second column K4.
  • the liquid 29 is vaporized either in a dedicated vaporizer (not shown) or in the heat exchanger G.
  • the liquid 29 can be vaporized by heat exchange with all the air 32 to partially condense the air 32 which will then be sent to the tank of the first column K3. Otherwise the liquid 29 can be vaporized by heat exchange with part of the air 32 to completely condense this part of the air 32.
  • the condensed air will then be sent to the first column tank K3 or to an intermediate point of the first and / or second column.
  • part of the purified air can be boosted in a booster at a pressure higher than that of the first column K3 to vaporize the liquid 29.

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Abstract

An apparatus for separating air, comprising a double column (K3, K4), means (B) for sending air to the purification unit at a pressure that is no more than 1 bar higher than atmospheric pressure, a pipe for sending a first air flow (8), which has been purified in the purification unit, to the heat exchanger at a fourth pressure that is no more than 1 bar higher than the second pressure, a pipe for sending the first purified air flow, which has been cooled in the heat exchanger, to the second column for separation, and a booster compressor (E), the apparatus not comprising any means for depressurising the first flow.

Description

Appareil et procédé de séparation d’air par distillation cryogénique Apparatus and method for air separation by cryogenic distillation
La présente invention est relative à un appareil et à un procédé de séparation d’air par distillation cryogénique. The present invention relates to an apparatus and a method for separating air by cryogenic distillation.
En particulier elle concerne un appareil de séparation d’air comprenant une double colonne avec une première colonne opérant à une première pression et une deuxième colonne opérant à une deuxième pression, inférieure à la première pression. La tête de la première colonne produit un gaz qui se condense dans un rebouilleur de la deuxième colonne. In particular, it relates to an air separation device comprising a double column with a first column operating at a first pressure and a second column operating at a second pressure, lower than the first pressure. The head of the first column produces a gas which condenses in a reboiler of the second column.
Il est généralement un objectif des appareils de séparation d’air de rechercher une consommation d’énergie la plus basse possible. It is generally an objective of air separation devices to seek the lowest possible energy consumption.
L’épuration de l’air est en général effectuée à une pression égale ou supérieure à celle de la première pression. Ceci permet de réduire le volume de l’unité d’épuration. Air cleaning is generally carried out at a pressure equal to or greater than that of the first pressure. This makes it possible to reduce the volume of the purification unit.
Il est néanmoins connu de US4964901 d’épurer une partie de l’air à la première pression et le reste de l’air à la deuxième pression, utilisant deux unités d’épuration en parallèle. L’air épuré à la deuxième pression est envoyé directement à la deuxième colonne, tandis que l’air épuré à la première pression est séparé en deux, une partie étant envoyée directement à la première colonne et le reste étant surpressé, refroidi dans un échangeur de chaleur, détendu dans une turbine couplée au surpresseur et envoyé à la deuxième colonne. Ainsi la turbine utilisée est une turbine d’insufflation et la colonne basse pression reçoit de l’air ayant été épuré à deux pressions différentes. However, it is known from US4964901 to purify part of the air at the first pressure and the rest of the air at the second pressure, using two purification units in parallel. The air purified at the second pressure is sent directly to the second column, while the air purified at the first pressure is separated in two, a part being sent directly to the first column and the rest being overpressed, cooled in an exchanger of heat, expanded in a turbine coupled to the booster and sent to the second column. Thus the turbine used is an insufflation turbine and the low pressure column receives air having been purified at two different pressures.
Le procédé de US5934105 épure l'air à une pression au-dessus de la deuxième pression mais en dessous de la première pression, ensuite l'air destiné à la première colonne est comprimé et l'air destiné à la deuxième colonne est détendu. The process of US5934105 purifies the air at a pressure above the second pressure but below the first pressure, then the air intended for the first column is compressed and the air intended for the second column is expanded.
JPH1 1063810 et EP1050730 sont similaires à US5934105. JPH1 1063810 and EP1050730 are similar to US5934105.
Si tout le débit qui va la deuxième colonne est détendu dans la turbine, comme dans l’art antérieur, pour maximiser le gain en énergie, le débit d'air allant à la première colonne est d'environ 66% du débit total épuré, par exemple pour produire de l’oxygène à 96%. Cela signifie que l’on doit passer 34% du débit d'air à une relative basse pression dans la turbine. Selon la présente invention, entre 6 et 8% de l’air est détendu dans une turbine d’air, donc la turbine selon l’art antérieur est au moins 4 à 5 fois plus grosse du fait du débit volume. If all the flow going to the second column is expanded in the turbine, as in the prior art, to maximize the energy gain, the air flow going to the first column is approximately 66% of the total purified flow, for example to produce 96% oxygen. This means that 34% of the air flow must be passed at a relatively low pressure in the turbine. According to the present invention, between 6 and 8% of the air is expanded in an air turbine, therefore the turbine according to the prior art is at least 4 to 5 times larger due to the volume flow.
Comme la puissance frigorifique du procédé selon l’art antérieur est fixée et reste basse puisque le procédé ne produit pas de produit final liquide, cela signifie que le taux de détente de la turbine est très faible ce qui donne une turbine inefficace et en tout cas pas du tout standardisée, voire inexistante chez les fournisseurs de turbines cryogéniques. As the cooling capacity of the process according to the prior art is fixed and remains low since the process does not produce a final liquid product, this means that the expansion rate of the turbine is very low which gives an ineffective turbine and in any case not at all standardized, or even non-existent at the suppliers of cryogenic turbines.
Dans le cas où on souhaite imposer le débit d'air envoyé à la première colonne pour maximiser le gain d'énergie, selon l’art antérieur, en exploitation, la régulation de la puissance frigorifique ne pourra se faire par une réduction de débit turbiné et donc va se faire en jouant sur la pression en amont de la turbine, c’est à dire la pression d'épuration et in fine de la soufflante. Cela complexifie énormément la régulation et oblige à dimensionner l'épuration sur la pression la plus basse que l'on pourrait avoir avec une puissance frigorifique plus faible que prévue au nominal ou dans une phase transitoire. Selon l’invention, il est prévu que la pression d’épuration soit très proche de la deuxième pression. In the case where it is desired to impose the air flow rate sent to the first column in order to maximize the energy gain, according to the prior art, in operation, the regulation of the cooling capacity cannot be done by a reduction in turbine flow rate. and therefore will be done by playing on the pressure upstream of the turbine, that is to say the purifying pressure and ultimately the blower. This enormously complicates the regulation and obliges to size the purification on the lowest pressure that one could have with a lower refrigerating power than expected at nominal or in a transient phase. According to the invention, it is expected that the cleaning pressure is very close to the second pressure.
L’invention prévoit un procédé qui consomme 1 % en moins d’énergie (2% en moins si on considère un rendement turbine réduit de 5%pt) par rapport à l’art antérieur (par exemple, selon EP1050730) ; selon le procédé de EP1050730, l’épuration est effectuée à une pression entre la première et la deuxième pression. The invention provides a process which consumes 1% less energy (2% less if we consider a turbine efficiency reduced by 5% pt) compared to the prior art (for example, according to EP1050730); according to the method of EP1050730, the purification is carried out at a pressure between the first and the second pressure.
Le taux de détente du procédé de EP1050730 est faible, entre 1 ,2 :1 et 3,8 :1 , de préférence entre 1 ,4 :1 et 2,5 :1 , alors que les turbines classiques cryogéniques sont dans une fourchette de taux de détente d’entre 4 :1 et 10 : 1 . L’invention utilise un taux de détente qui reste en limite basse de cette fourchette, évitant ainsi d’avoir un rendement de turbine sensiblement dégradé. The expansion rate of the EP1050730 process is low, between 1: 2: 1 and 3.8: 1, preferably between 1: 4: 1 and 2.5: 1, while conventional cryogenic turbines are within a range of relaxation ratio between 4: 1 and 10: 1. The invention uses an expansion rate which remains at the lower limit of this range, thus avoiding having a substantially degraded turbine efficiency.
Dans EP1050730, la pression d’entrée de l’unité d’épuration est typiquement de 2,5 bara (au lieu d’environ 1 .3 bara selon l’invention). Ce procédé utilise un premier compresseur à plusieurs, typiquement deux, étages avec refroidissement entre deux étages. Selon l’invention le compresseur qui comprime tout l’air a un seul étage donc aucun refroidissement entre deux étages. In EP1050730, the inlet pressure of the purification unit is typically 2.5 bara (instead of approximately 1.3 bara according to the invention). This process uses a first compressor with several, typically two, stages with cooling between two stages. According to the invention, the compressor which compresses all the air has a single stage, therefore no cooling between two stages.
L’appareil produit un débit gazeux enrichi en oxygène avec une énergie particulièrement basse. US5666824 décrit un procédé selon le préambule de la revendication 1 mais dans lequel le premier débit est au moins partiellement condensé dans un condenseur intermédiaire de la deuxième colonne. Si un gaz est formé, il est lui-même condensé dans un autre condenseur intermédiaire de la deuxième colonne et le liquide ainsi formé est envoyé en tête de la deuxième colonne. Ainsi le premier débit n’est pas envoyé directement à la distillation. The device produces a gas flow enriched in oxygen with a particularly low energy. US5666824 describes a method according to the preamble of claim 1 but in which the first flow is at least partially condensed in an intermediate condenser of the second column. If a gas is formed, it is itself condensed in another intermediate condenser of the second column and the liquid thus formed is sent to the head of the second column. Thus the first flow is not sent directly to the distillation.
WO2013/014252 décrit à la Figure 6 un procédé dans lequel une première partie de l’air est refroidie à son point de rosée dans un échangeur de chaleur où un débit d’air détendu dans une turbine est également refroidi à son point de rosée. Ceci est impossible puisque l’azote résiduaire qui refroidit les débits d’air a été déjà réchauffé dans un sous-refroidisseur. Dans ce cas, l’azote est trop chaud pour refroidir les débits d’air à leur point de rosée et les débits d’air seront refroidis tout au plus à une température environ 10°C au-dessus du point de rosée. WO2013 / 014252 describes in FIG. 6 a process in which a first part of the air is cooled to its dew point in a heat exchanger where an expanded air flow in a turbine is also cooled to its dew point. This is impossible since the residual nitrogen which cools the air flows has already been heated in a sub-cooler. In this case, the nitrogen is too hot to cool the air flows to their dew point and the air flows will be cooled at most to a temperature around 10 ° C above the dew point.
De plus, en calculant le bilan frigorifique de la Figure 6, on constate qu’en utilisant un compresseur en amont de la turbine et en refroidissant à la température ambiante avant détente, il faut une pression de compression supérieure à 80 bar. Dans ce cas, le taux de détente de la turbine est très supérieur aux valeurs utilisées dans l’industrie. Ainsi il n’est pas possible pour l’homme de l’art de mettre en œuvre le procédé de la Figure 6 telle que décrite. In addition, by calculating the refrigeration budget in Figure 6, we see that using a compressor upstream of the turbine and cooling to room temperature before expansion, a compression pressure greater than 80 bar is required. In this case, the expansion rate of the turbine is much higher than the values used in industry. Thus it is not possible for a person skilled in the art to implement the method of FIG. 6 as described.
Selon un objet de l’invention, il est prévu un appareil de séparation d’air comprenant une double colonne avec une première colonne opérant à une première pression et une deuxième colonne opérant à une deuxième pression, inférieure à la première pression, la deuxième colonne ayant un rebouilleur de cuve, des moyens pour envoyer un gaz enrichi en azote de la tête de la première colonne au rebouilleur de cuve et des moyens pour envoyer au moins une partie du gaz enrichi en azote condensé du rebouilleur de cuve à la tête de la première colonne, un échangeur de chaleur, une unité d’épuration, des moyens pour envoyer de l’air à l’unité d’épuration à une troisième pression supérieure à la pression atmosphérique d’au plus 1 bar, une conduite pour envoyer un premier débit d’air épuré dans l’unité d’épuration à l’échangeur de chaleur à une quatrième pression supérieure à la deuxième pression d’au plus 1 bar, une conduite pour introduire le premier débit d’air épuré refroidi dans l’échangeur de chaleur dans la deuxième colonne pour s’y séparer, un surpresseur, une conduite pour envoyer un deuxième débit d’air épuré dans l’unité d’épuration au surpresseur, une conduite pour envoyer au moins une partie du deuxième débit comprimé par le surpresseur jusqu’à une cinquième pression entre la première pression et 1 bar au-dessus de la première pression à l’échangeur de chaleur, des moyens de production de frigories, une conduite pour soutirer au moins un fluide enrichi en oxygène ou en azote d’une colonne de la double colonne reliée à l’échangeur de chaleur et une conduite pour sortir d’au moins un fluide enrichi en oxygène ou en azote de l’échangeur de chaleur comme produit, l’appareil ne comprenant aucun moyen de détente du premier débit et ne comprenant qu’une seule unité d’épuration caractérisé en ce que la deuxième colonne ne comprend pas de condenseur intermédiaire, la conduite pour introduire le premier débit d’air épuré étant reliée à l’intérieur de la deuxième colonne pour permettre au premier débit de participer à la distillation. According to an object of the invention, there is provided an air separation device comprising a double column with a first column operating at a first pressure and a second column operating at a second pressure, lower than the first pressure, the second column having a tank reboiler, means for sending a nitrogen-enriched gas from the head of the first column to the tank reboiler and means for sending at least part of the condensed nitrogen enriched gas from the tank reboiler to the head of the first column, a heat exchanger, a purification unit, means for sending air to the purification unit at a third pressure higher than atmospheric pressure by at most 1 bar, a pipe for sending a first flow of purified air in the purification unit at the heat exchanger at a fourth pressure greater than the second pressure by at most 1 bar, a line for introducing the first flow of cooled purified air into the heat exchanger heat in the second column to separate therefrom, a booster, a pipe for sending a second flow of purified air in the purification unit to the booster, a pipe for sending at least part of the second flow compressed by the booster to a fifth pressure between the first pressure and 1 bar above the first pressure at the heat exchanger, means for producing refrigerants, a pipe for withdrawing at least one fluid enriched in oxygen or in nitrogen from a column of the double column connected to the heat exchanger and a pipe for leaving at least one fluid enriched in oxygen or in nitrogen from the heat exchanger as product, the apparatus comprising no means expansion of the first flow and comprising only one purification unit characterized in that the second column does not include an intermediate condenser, the pipe for introducing the first flow of purified air being connected to the interior of the second column to allow the first flow to participate in the distillation.
Selon d’autres aspects facultatifs : According to other optional aspects:
• les moyens de production de frigories comprennent au moins une turbine de détente d’une partie du deuxième débit et/ou une turbine de détente d’un gaz riche en azote provenant de la première colonne et/ou des moyens d’envoi d’un liquide cryogénique d’une source externe à la double colonne. • the means for producing frigories include at least one expansion turbine for part of the second flow and / or one expansion turbine for a gas rich in nitrogen coming from the first column and / or means for sending a cryogenic liquid from a source external to the double column.
• la turbine de détente de la partie du deuxième débit est reliée à la deuxième colonne pour y envoyer l’air détendu. • the expansion turbine of the part of the second flow is connected to the second column to send the expanded air.
• les moyens pour envoyer de l’air à l’unité d’épuration à la troisième pression ne comprennent aucun moyen de compression à part un compresseur à un seul étage. • the means for sending air to the purification unit at the third pressure do not include any compression means apart from a single-stage compressor.
• l’appareil ne comprend aucun moyen de compression du premier débit.• the device does not include any means of compressing the first flow.
Selon un autre aspect de l’invention, il est prévu un procédé de séparation d’air par distillation cryogénique utilisant une double colonne avec une première colonne opérant à une première pression et une deuxième colonne opérant à une deuxième pression, inférieure à la première pression, la deuxième colonne ayant un rebouilleur de cuve, dans lequel : According to another aspect of the invention, there is provided a method of air separation by cryogenic distillation using a double column with a first column operating at a first pressure and a second column operating at a second pressure, lower than the first pressure , the second column having a tank reboiler, in which:
i) on envoie de l’air contenant de l’eau et du dioxyde de carbone à une seule unité d’épuration à une troisième pression supérieure à la pression atmosphérique d’au plus 1 bar, i) air containing water and carbon dioxide is sent to a single purification unit at a third pressure greater than atmospheric pressure by at most 1 bar,
ii) on sépare l’air épuré en deux, ii) the purified air is separated in two,
ii) on envoie un premier débit d’air épuré dans l’unité d’épuration à un échangeur de chaleur à une quatrième pression supérieure à la deuxième pression d’au plus 1 bar, iv) on envoie le premier débit d’air épuré refroidi dans l’échangeur de chaleur à la deuxième colonne, sans l’avoir détendu, ii) a first flow of purified air is sent into the purification unit to a heat exchanger at a fourth pressure greater than the second pressure by at most 1 bar, iv) the first flow of cooled purified air is sent into the heat exchanger to the second column, without having relaxed it,
v) on surpresse un deuxième débit d’air épuré à une cinquième pression entre la première pression et 1 bar au-dessus de la première pression, on envoie au moins une partie du deuxième débit à la cinquième pression à l’échangeur de chaleur et on envoie l’au moins une partie du deuxième débit à la première colonne sous forme gazeuse, v) a second purified air flow is boosted at a fifth pressure between the first pressure and 1 bar above the first pressure, at least part of the second flow is sent at the fifth pressure to the heat exchanger and at least part of the second flow is sent to the first column in gaseous form,
vi) on fournit des frigories pour le maintien en froid du procédé vi) we provide frigories to keep the process cold
vii) on condense au moins partiellement un gaz riche en azote de la première colonne dans le rebouilleur et on renvoie au moins une partie de l’azote condensé à la première colonne vii) at least partially condensing a nitrogen-rich gas from the first column in the reboiler and returning at least some of the condensed nitrogen to the first column
viii) on envoie un liquide enrichi en azote et un liquide enrichi en oxygène de la première colonne à la deuxième colonne viii) a liquid enriched in nitrogen and a liquid enriched in oxygen are sent from the first column to the second column
ix) on soutire un gaz enrichi en oxygène ou un gaz enrichi en azote de la double colonne et on le réchauffe dans l’échangeur de chaleur pour former un produit du procédé caractérisé en ce que le premier débit d’air est envoyé directement dans la deuxième colonne pour s’y séparer sans avoir été condensé dans un condenseur. ix) an oxygen-enriched gas or a nitrogen-enriched gas is drawn off from the double column and it is heated in the heat exchanger to form a product of the process characterized in that the first air flow is sent directly to the second column to separate there without having been condensed in a condenser.
Selon d’autres aspects facultatifs : According to other optional aspects:
• on envoie tout le premier débit à la deuxième colonne. • the entire first flow is sent to the second column.
• on envoie le premier débit à la deuxième colonne à un niveau inférieur ou égale au niveau d’arrivée du liquide enrichi en oxygène. • the first flow is sent to the second column at a level less than or equal to the arrival level of the oxygen-enriched liquid.
• le procédé ne produit aucun produit liquide comme produit final et /ou aucun débit liquide n’est soutiré de la double colonne pour servir de produit final. • the process produces no liquid product as final product and / or no liquid flow is drawn from the double column to serve as final product.
• le procédé est tenu en froid par détente d’une partie du deuxième débit dans une turbine de la cinquième pression à la deuxième pression. • the process is kept cold by expansion of part of the second flow in a turbine from the fifth pressure to the second pressure.
• la partie de l’air détendue dans la turbine représente entre 6 et 15% vol, préférentiellement entre 6 et 8% de l’air épuré. • the part of the air expanded in the turbine represents between 6 and 15% vol, preferably between 6 and 8% of the purified air.
• tout l’air est épuré à une pression qui n’excède pas 1 ,5 bara, voire n’excède pas 1 ,3 bara. • all the air is purified at a pressure which does not exceed 1, 5 bara, or even does not exceed 1, 3 bara.
• tout le deuxième débit se refroidit dans l’échangeur de chaleur jusqu’à une température intermédiaire de l’échangeur de chaleur, l’entrée de la turbine est à la température intermédiaire de l’échangeur de chaleur et la partie du deuxième débit envoyé à la première colonne se refroidit dans l’échangeur de chaleur jusqu’au bout froid de celui-ci. • all the second flow cools in the heat exchanger to an intermediate temperature of the heat exchanger, the turbine inlet is at the intermediate temperature of the heat exchanger and the part of the second flow sent to the first column cools in the heat exchanger until the cold end of it.
• la première pression n’excède pas 6 bara. • the first pressure does not exceed 6 bara.
• la deuxième pression n’excède pas 1 ,5 bara. • the second pressure does not exceed 1.5 bara.
• le gaz enrichi en oxygène contient au moins 80% mol oxygène. • the oxygen-enriched gas contains at least 80 mol% oxygen.
• le gaz enrichi en oxygène contient au moins 90% mol d’oxygène. • the oxygen-enriched gas contains at least 90 mol% of oxygen.
• le gaz enrichi en oxygène contient moins que 98% mol d’oxygène. • the oxygen-enriched gas contains less than 98% mol of oxygen.
• le premier débit représente entre 20 et 30% vol du débit d’air épuré. • the first flow represents between 20 and 30% vol of the purified air flow.
• le deuxième débit représente entre 70 et 80% vol du débit d’air épuré. • the second flow represents between 70 and 80% vol of the purified air flow.
• on soutire un gaz enrichi en oxygène et/ou un gaz enrichi en azote de la double colonne et on le(s) réchauffe dans l’échangeur de chaleur pour former un produit du procédé en l’introduisant ou en les introduisant au bout froid de l’échangeur de chaleur. • a gas enriched in oxygen and / or a gas enriched in nitrogen is withdrawn from the double column and it (s) is heated in the heat exchanger to form a product of the process by introducing it or introducing them at the cold end of the heat exchanger.
• le premier débit d’air et/ou la partie du deuxième débit destiné à la première colonne est refroidi dans l’échangeur de chaleur jusqu’à une température au moins 5°C au-dessus de son point de rosée. • the first air flow and / or the part of the second flow intended for the first column is cooled in the heat exchanger to a temperature at least 5 ° C above its dew point.
• on soutire un liquide enrichi en oxygène on le réchauffe dans l’échangeur de chaleur pour former un produit du procédé. • a liquid enriched in oxygen is drawn off and heated in the heat exchanger to form a product of the process.
• on pressurise le liquide enrichi en oxygène avant de le vaporiser soit dans un vaporiseur dédié soit dans l’échangeur de chaleur. • the oxygen-enriched liquid is pressurized before vaporizing it either in a dedicated vaporizer or in the heat exchanger.
• on vaporise le liquide enrichi en oxygène par échange de chaleur avec une partie du deuxième débit ou avec un troisième débit d’air pressurisé à une pression supérieure à la cinquième pression. • the oxygen-enriched liquid is vaporized by heat exchange with part of the second flow or with a third flow of pressurized air at a pressure greater than the fifth pressure.
• on sousrefroidit le premier débit d’air entre l’échangeur de chaleur et la deuxième colonne. • the first air flow between the heat exchanger and the second column is sub-cooled.
• on sousrefroidit entre la sortie de la turbine et la deuxième colonne la partie de l’air détendu dans la turbine. • the part of the expanded air in the turbine is sub-cooled between the turbine outlet and 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.
La figure 1 représente un procédé de séparation d’air par distillation cryogénique selon l’invention. FIG. 1 represents a method of air separation by cryogenic distillation according to the invention.
Un appareil de séparation d’air par distillation cryogénique comprend une double colonne avec une première colonne K3 opérant à une première pression et une deuxième colonne K4 opérant à une deuxième pression, inférieure à la première pression, la deuxième colonne ayant un rebouilleur de cuve M. La deuxième colonne K4 ne contient pas de condenseur intermédiaire. An air separation apparatus by cryogenic distillation comprises a double column with a first column K3 operating at a first pressure and a second column K4 operating at a second pressure, lower than the first pressure, the second column having a tank reboiler M. The second column K4 does not contain an intermediate condenser.
Dans cet exemple la première pression est de 4,5 bara et la deuxième pression est 1 ,13 bara. In this example the first pressure is 4.5 bara and the second pressure is 1.13 bara.
Un gaz enrichi en azote est envoyé de la tête de la première colonne au rebouilleur de cuve M et au moins une partie du gaz enrichi en azote condensé du rebouilleur de cuve est envoyée à la tête de la première colonne. A gas enriched in nitrogen is sent from the head of the first column to the tank reboiler M and at least part of the gas enriched in condensed nitrogen from the tank reboiler is sent to the head of the first column.
De l’air à la pression atmosphérique est filtré dans une filtre A, comprimé par une soufflante B ayant un seul étage à une pression au plus 1 bar, de préférence au plus 0,5 bar, au-dessus de la pression atmosphérique, refroidi par un moyen de refroidissement C et épuré en eau et en dioxyde de carbone dans une seule unité d’épuration D dans lequel l’air 4 rentre à une troisième pression supérieure à la pression atmosphérique d’au plus 1 bar, de préférence d’au plus 0,5 bar. L’unité d’épuration comprend deux lits d’adsorbant utilisés en alternance pour épurer l’air, un lit épurant l’air pendant que l’autre est régénéré. Air at atmospheric pressure is filtered in a filter A, compressed by a blower B having a single stage at a pressure at most 1 bar, preferably at most 0.5 bar, above atmospheric pressure, cooled by a cooling means C and purified with water and carbon dioxide in a single purification unit D in which the air 4 returns to a third pressure higher than atmospheric pressure by at most 1 bar, preferably of at most 0.5 bar. The purification unit includes two adsorbent beds used alternately to purify the air, one bed purifying the air while the other is regenerated.
L’air épuré dans l’unité D est divisé en deux pour former deux débits 6,8. L’air 8 n’est ni comprimé ni détendu et se trouve à une pression qui diffère de la deuxième pression d’une pression égale aux pertes de charge dans les conduites et l’échangeur de chaleur G. The purified air in unit D is divided in two to form two flows 6.8. Air 8 is neither compressed nor expanded and is at a pressure which differs from the second pressure by a pressure equal to the pressure losses in the pipes and the heat exchanger G.
De préférence le premier débit 8 représente entre 20 et 30% vol du débit 4 et le deuxième débit 6 représente entre 70 et 80% vol du débit 4. Preferably, the first flow 8 represents between 20 and 30% vol of the flow 4 and the second flow 6 represents between 70 and 80% vol of the flow 4.
Ainsi, l’air 8 est envoyé directement de l’unité d’épuration à la deuxième colonne K2 pour y être séparé, rentrant dans la colonne sous forme entièrement gazeuse. L’air 8 se refroidit dans l’échangeur de chaleur G jusqu’à une température au moins 5°C au-dessus de son point de rosée. Thus, the air 8 is sent directly from the purification unit to the second column K2 to be separated there, returning to the column in entirely gaseous form. The air 8 cools in the heat exchanger G to a temperature at least 5 ° C above its dew point.
Le débit 6 est surpressé dans un surpresseur E, refroidi dans un refroidisseur F et envoyé à l’échangeur de chaleur G. Le surpresseur E surpresse l’air 6 jusqu’à une cinquième pression entre la première pression et 1 bar au-dessus de la première pression. L’air 6 est divisé en deux parties 30,32 à un niveau intermédiaire de l’échangeur. L’air 30 sort de l’échangeur à une température intermédiaire de celui-ci, par exemple -125°C, est détendu dans une turbine 28 jusqu’à la deuxième pression et rentre sous forme gazeuse, mélangé avec le débit 8, pour être séparé dans la deuxième colonne K4. Le débit 30 peut représenter entre 6 et 15 % vol, préférentiellement entre 6 et 8% de l’air 4. The flow 6 is boosted in a booster E, cooled in a cooler F and sent to the heat exchanger G. The booster E boosts the air 6 to a fifth pressure between the first pressure and 1 bar above the first press. The air 6 is divided into two parts 30, 32 at an intermediate level of the exchanger. The air 30 leaves the exchanger at an intermediate temperature thereof, for example -125 ° C, is expanded in a turbine 28 until the second pressure and returns in gaseous form, mixed with the flow 8, to be separated in the second column K4. The flow 30 can represent between 6 and 15% vol, preferably between 6 and 8% of the air 4.
L’air 32 se refroidit jusqu’au bout froid de l’échangeur G et est envoyé en cuve de la première colonne K3 sous forme essentiellement gazeuse pour y être séparé. L’air 8 se refroidit dans l’échangeur de chaleur G jusqu’à une température au moins 5°C au-dessus de son point de rosée. The air 32 cools down to the cold end of the exchanger G and is sent to the tank of the first column K3 in essentially gaseous form in order to be separated there. The air 8 cools in the heat exchanger G to a temperature at least 5 ° C above its dew point.
Un débit liquide enrichi en oxygène 34 est soutiré en cuve de la première colonne et envoyé à un niveau de la deuxième colonne qui est au-dessus de l’entrée d’air. Alternativement l’air peut rentrer dans la deuxième colonne au même niveau que celui de l’arrivée du liquide 34. A liquid flow enriched with oxygen 34 is withdrawn from the tank of the first column and sent to a level of the second column which is above the air inlet. Alternatively the air can enter the second column at the same level as that of the arrival of the liquid 34.
Le liquide 34 détendu peut être séparé dans un séparateur de phase : le liquide issu du séparateur de phase est envoyé dans la colonne K4 et la phase vapeur peut être mélangée à l’entrée d’air 8,30 dans la colonne K4. The expanded liquid 34 can be separated in a phase separator: the liquid from the phase separator is sent to column K4 and the vapor phase can be mixed with the air inlet 8.30 in column K4.
Un débit d’azote liquide 35 est soutiré de la tête de la première colonne et envoyé en tête de la deuxième colonne. A flow of liquid nitrogen 35 is withdrawn from the head of the first column and sent to the head of the second column.
De l’azote gazeux 36 est soutiré en tête de la deuxième colonne K4 et se réchauffé dans le sous-refroidisseur S et ensuite dans l’échangeur G. Une partie 14 de ce gaz sert à régénérer l’unité d’épuration D. Nitrogen gas 36 is drawn off at the head of the second column K4 and is heated in the sub-cooler S and then in the exchanger G. Part 14 of this gas is used to regenerate the purification unit D.
De l’oxygène gazeux 29 est soutiré en cuve de la deuxième colonne K4. Le débit 29 contient de préférence au moins 80% mol oxygène, voire au moins 90% mol d’oxygène, mais de préférence, moins que 98% mol d’oxygène. Gaseous oxygen 29 is withdrawn from the tank of the second column K4. The flow 29 preferably contains at least 80 mol% oxygen, or even at least 90 mol% oxygen, but preferably less than 98 mol% oxygen.
Il sera remarqué que le procédé ne produit aucun débit liquide comme produit final. Le procédé ne produit aucun débit liquide à vaporiser pour former un produit gazeux final, éventuellement sous pression. Il est toutefois possible de produire une petite quantité de produit gazeux final de cette façon, qui peut être éventuellement mélangé avec le produit gazeux principal. It will be noted that the process produces no liquid flow as the final product. The process produces no liquid flow to vaporize to form a final gaseous product, possibly under pressure. It is however possible to produce a small amount of final gaseous product in this way, which can optionally be mixed with the main gaseous product.
Par ailleurs, un petit débit de liquide pourrait être produit. In addition, a small flow of liquid could be produced.
En variante, l’air 8 et/ou l’air 30 peuvent être sous-refroid is dans le sous- refroidisseur S puis être introduit(s) dans la deuxième colonne K4. Sinon le mélange des débits 8 et 30 peut être sous-refroidi dans le sous-refroidisseur S puis être introduit dans la deuxième colonne K4. As a variant, the air 8 and / or the air 30 may be sub-cooled is in the sub-cooler S and then be introduced into the second column K4. Otherwise, the mixture of flows 8 and 30 can be sub-cooled in the sub-cooler S and then be introduced into the second column K4.
Dans l’exemple décrit, le débit 29 est un débit d’oxygène gazeux qui se réchauffe dans l’échangeur de chaleur G à partir du bout froid de l’échangeur G. En alternatif, le débit 29 peut être un débit de liquide riche en oxygène pressurisé à une pression au- dessus de celle de la deuxième colonne K4. Le liquide 29 se vaporise soit dans un vaporiseur dédié (non illustré) soit dans l’échangeur de chaleur G. Le liquide 29 peut être vaporisé par échange de chaleur avec tout l’air 32 pour condenser partiellement l’air 32 qui sera ensuite envoyé à la cuve de la première colonne K3. Sinon le liquide 29 peut être vaporisé par échange de chaleur avec une partie de l’air 32 pour condenser totalement cette partie de l’air 32. L’air condensé sera ensuite envoyé à la cuve de première colonne K3 ou à un point intermédiaire de la première et/ou de la deuxième colonne. In the example described, the flow 29 is a flow of gaseous oxygen which heats up in the heat exchanger G from the cold end of the exchanger G. Alternatively, the flow 29 can be a flow of rich liquid in pressurized oxygen at a pressure above that of the second column K4. The liquid 29 is vaporized either in a dedicated vaporizer (not shown) or in the heat exchanger G. The liquid 29 can be vaporized by heat exchange with all the air 32 to partially condense the air 32 which will then be sent to the tank of the first column K3. Otherwise the liquid 29 can be vaporized by heat exchange with part of the air 32 to completely condense this part of the air 32. The condensed air will then be sent to the first column tank K3 or to an intermediate point of the first and / or second column.
Sinon une partie de l’air épuré peut être surpressée dans un surpresseur à une pression supérieure à la celle de la première colonne K3 pour vaporiser le liquide 29. Otherwise, part of the purified air can be boosted in a booster at a pressure higher than that of the first column K3 to vaporize the liquid 29.

Claims

Revendications Claims
1 . Appareil de séparation d’air comprenant une double colonne avec une première colonne (K3) opérant à une première pression et une deuxième colonne (K4) opérant à une deuxième pression, inférieure à la première pression, la deuxième colonne ayant un rebouilleur de cuve (M), des moyens pour envoyer un gaz enrichi en azote de la tête de la première colonne au rebouilleur de cuve et des moyens pour envoyer au moins une partie du gaz enrichi en azote condensé du rebouilleur de cuve à la tête de la première colonne, un échangeur de chaleur (G), une unité d’épuration (D), des moyens (B) pour envoyer de l’air à l’unité d’épuration à une troisième pression supérieure à la pression atmosphérique d’au plus 1 bar, une conduite pour envoyer un premier débit d’air (8), épuré dans l’unité d’épuration, à l’échangeur de chaleur à une quatrième pression supérieure à la deuxième pression d’au plus 1 bar, une conduite pour introduire le premier débit d’air épuré refroidi dans l’échangeur de chaleur dans la deuxième colonne pour s’y séparer, un surpresseur (E), une conduite pour envoyer un deuxième débit d’air (6) épuré dans l’unité d’épuration au surpresseur, une conduite pour envoyer au moins une partie du deuxième débit comprimé par le surpresseur jusqu’à une cinquième pression entre la première pression et 1 bar au-dessus de la première pression à l’échangeur de chaleur, des moyens de production de frigories (28), une conduite pour soutirer au moins un fluide (29) enrichi en oxygène ou en azote d’une colonne de la double colonne reliée à l’échangeur de chaleur et une conduite pour sortir d’au moins un fluide enrichi en oxygène ou en azote de l’échangeur de chaleur comme produit, l’appareil ne comprenant aucun moyen de détente du premier débit et ne comprenant qu’une seule unité d’épuration caractérisé en ce que la deuxième colonne ne comprend pas de condenseur intermédiaire, la conduite pour introduire le premier débit d’air épuré étant reliée à l’intérieur de la deuxième colonne pour permettre au premier débit de participer à la distillation. 1. Air separation apparatus comprising a double column with a first column (K3) operating at a first pressure and a second column (K4) operating at a second pressure, lower than the first pressure, the second column having a tank reboiler ( M), means for sending a nitrogen-enriched gas from the head of the first column to the tank reboiler and means for sending at least a portion of the gas enriched in condensed nitrogen from the tank reboiler to the head of the first column, a heat exchanger (G), a purification unit (D), means (B) for sending air to the purification unit at a third pressure higher than atmospheric pressure by at most 1 bar , a line for sending a first air flow (8), purified in the purification unit, to the heat exchanger at a fourth pressure greater than the second pressure by at most 1 bar, a line for introducing the first flow of purified air cooled in the heat exchanger in the second column for separating therefrom, a booster (E), a pipe for sending a second flow of purified air (6) in the purification unit to the booster, a pipe for sending at least part of the second compressed flow by the booster up to a fifth pressure between the first pressure and 1 bar above the first pressure at the heat exchanger, means for producing refrigerants (28), a pipe for withdrawing at least one fluid (29 ) enriched in oxygen or nitrogen from a column of the double column connected to the heat exchanger and a pipe for leaving at least one fluid enriched in oxygen or nitrogen from the heat exchanger as product, the apparatus comprising no means for expansion of the first flow and comprising only one purification unit characterized in that the second column does not comprise an intermediate condenser, the pipe for introducing the first flow of purified air being connected to the inside the second column for r allow the first flow to participate in the distillation.
2. Appareil selon la revendication 1 dans lequel les moyens de production de frigories comprennent au moins une turbine de détente (28) d’une partie (30) du deuxième débit (6) et/ou une turbine de détente d’un gaz riche en azote provenant de la première colonne (K3) et/ou des moyens d’envoi d’un liquide cryogénique d’une source externe à la double colonne (K3, K4). 2. Apparatus according to claim 1 wherein the means for producing frigories comprise at least one expansion turbine (28) of a part (30) of the second flow (6) and / or a turbine for expansion of a rich gas nitrogen from the first column (K3) and / or means for sending a cryogenic liquid from a source external to the double column (K3, K4).
3. Appareil selon la revendication 2 dans lequel la turbine de détente (28) de la partie (30) du deuxième débit (6) est reliée à la deuxième colonne (K4) pour y envoyer l’air détendu. 3. Apparatus according to claim 2 wherein the expansion turbine (28) of the part (30) of the second flow (6) is connected to the second column (K4) to send the expanded air.
4. Appareil selon la revendication 1 ou 2 dans lequel les moyens pour envoyer de l’air à l’unité d’épuration à la troisième pression ne comprennent aucun moyen de compression à part un compresseur (B) à un seul étage. 4. Apparatus according to claim 1 or 2 wherein the means for sending air to the purification unit at the third pressure does not include any compression means apart from a single stage compressor (B).
5. Appareil selon la revendication 1 ,2 ou 3 ne comprenant aucun moyen de compression du premier débit (8). 5. Apparatus according to claim 1, 2 or 3 comprising no means for compressing the first flow (8).
6. Procédé de séparation d’air par distillation cryogénique utilisant une double colonne avec une première colonne (K3) opérant à une première pression et une deuxième colonne (K4) opérant à une deuxième pression, inférieure à la première pression, la deuxième colonne ayant un rebouilleur de cuve (M), dans lequel : 6. Method of air separation by cryogenic distillation using a double column with a first column (K3) operating at a first pressure and a second column (K4) operating at a second pressure, lower than the first pressure, the second column having a tank reboiler (M), in which:
i) on envoie de l’air contenant de l’eau et du dioxyde de carbone à une seule unité d’épuration (D) à une troisième pression supérieure à la pression atmosphérique d’au plus 1 bar, i) air containing water and carbon dioxide is sent to a single purification unit (D) at a third pressure greater than atmospheric pressure by at most 1 bar,
ii) on sépare l’air épuré en deux, ii) the purified air is separated in two,
iii) on envoie un premier débit d’air (8) épuré dans l’unité d’épuration à un échangeur de chaleur (G) à une quatrième pression supérieure à la deuxième pression d’au plus 1 bar, iii) a first flow of purified air (8) is sent in the purification unit to a heat exchanger (G) at a fourth pressure greater than the second pressure by at most 1 bar,
iv) on envoie le premier débit d’air épuré refroidi dans l’échangeur de chaleur à la deuxième colonne (K4), sans l’avoir détendu, iv) the first flow of cooled purified air in the heat exchanger is sent to the second column (K4), without having relaxed it,
v) on surpresse un deuxième débit d’air (6) épuré à une cinquième pression entre la première pression et 1 bar au-dessus de la première pression, on envoie au moins une partie du deuxième débit à la cinquième pression à l’échangeur de chaleur et on envoie l’au moins une partie du deuxième débit à la première colonne sous forme gazeuse, v) a second flow of purified air (6) is boosted at a fifth pressure between the first pressure and 1 bar above the first pressure, at least part of the second flow is sent to the exchanger at the fifth pressure of heat and at least part of the second flow is sent to the first column in gaseous form,
vi) on fournit des frigories pour le maintien en froid du procédé, vii) on condense au moins partiellement un gaz riche en azote de la première colonne dans le rebouilleur et on renvoie au moins une partie de l’azote condensé à la première colonne, vi) supplying frigories for keeping the process cold, vii) at least partially condensing a nitrogen-rich gas from the first column in the reboiler and returning at least some of the condensed nitrogen to the first column,
viii) on envoie un liquide enrichi en azote (35) et un liquide enrichi en oxygène (34) de la première colonne à la deuxième colonne, viii) a liquid enriched in nitrogen (35) and a liquid enriched in oxygen (34) are sent from the first column to the second column,
ix) on soutire un gaz enrichi en oxygène (29) ou un gaz enrichi en azote de la double colonne et on le réchauffe dans l’échangeur de chaleur pour former un produit du procédé caractérisé en ce que le premier débit d’air est envoyé directement dans la deuxième colonne pour s’y séparer sans avoir été condensé dans un condenseur. ix) an oxygen-enriched gas (29) or a nitrogen-enriched gas is drawn from the double column and it is heated in the heat exchanger to form a product of the process characterized in that the first air flow is sent directly in the second column to separate there without having been condensed in a condenser.
7. Procédé selon la revendication 6 dans lequel on envoie le premier débit (8) à la deuxième colonne (K4) à un niveau inférieur ou égal au niveau d’arrivée du liquide enrichi en oxygène (34). 7. The method of claim 6 wherein the first flow (8) is sent to the second column (K4) at a level less than or equal to the arrival level of the oxygen-enriched liquid (34).
8. Procédé selon l’une des revendications 6 ou 7 tenu en froid par détente d’une partie (30) du deuxième débit (6) dans une turbine (28) de la cinquième pression à la deuxième pression, la partie de l’air détendue dans la turbine représentant de préférence entre 6 et 15% vol, préférentiellement entre 6 et 8% de l’air épuré. 8. Method according to one of claims 6 or 7 kept cold by expansion of a part (30) of the second flow (6) in a turbine (28) from the fifth pressure to the second pressure, the part of the expanded air in the turbine preferably representing between 6 and 15% vol, preferably between 6 and 8% of the purified air.
9. Procédé selon la revendication 8 dans lequel tout le deuxième débit (6) se refroidit dans l’échangeur de chaleur (G) jusqu’à une température intermédiaire de l’échangeur de chaleur, l’entrée de la turbine (28) est à la température intermédiaire de l’échangeur de chaleur et la partie (32) du deuxième débit envoyée à la première colonne se refroidit dans l’échangeur de chaleur jusqu’au bout froid de celui-ci. 9. The method of claim 8 wherein all the second flow (6) cools in the heat exchanger (G) to an intermediate temperature of the heat exchanger, the turbine inlet (28) is at the intermediate temperature of the heat exchanger and the part (32) of the second flow sent to the first column cools in the heat exchanger until the cold end thereof.
10. Procédé selon l’une des revendications 6 à 9 dans lequel tout l’air (4) est épuré à une pression qui n’excède pas 1 ,5 bara, voire n’excède pas 1 ,3 bara. 10. Method according to one of claims 6 to 9 wherein all the air (4) is purified at a pressure which does not exceed 1.5 bara, or even does not exceed 1.3 bara.
1 1 . Procédé selon l’une des revendications 6 à 10 dans lequel le gaz enrichi en oxygène (29) contient au moins 80% mol oxygène, voire au moins 90% mol d’oxygène, mais de préférence, moins que 98% mol d’oxygène. 1 1. Method according to one of Claims 6 to 10, in which the oxygen-enriched gas (29) contains at least 80 mol% of oxygen, or even at least 90 mol% of oxygen, but preferably less than 98 mol% of oxygen. .
12. Procédé selon l’une des revendications 6 à 1 1 dans lequel le premier débit (8) représente entre 20 et 30% vol du débit d’air épuré. 12. Method according to one of claims 6 to 1 1 wherein the first flow (8) represents between 20 and 30% vol of the flow of purified air.
13. Procédé selon l’une des revendications 6 à 12 dans lequel le deuxième débit (6) représente entre 70 et 80% vol du débit d’air épuré. 13. Method according to one of claims 6 to 12 wherein the second flow (6) represents between 70 and 80% vol of the flow of purified air.
14. Procédé selon l’une des revendications 6 à 13 dans lequel on soutire un gaz enrichi en oxygène (29) et/ou un gaz enrichi en azote de la double colonne et on le(s) réchauffe dans l’échangeur de chaleur (G) pour former un produit du procédé en l’introduisant ou en les introduisant au bout froid de l’échangeur de chaleur. 14. Method according to one of claims 6 to 13 wherein one withdraws an oxygen-enriched gas (29) and / or a nitrogen-enriched gas from the double column and it (s) is heated in the heat exchanger ( G) to form a product of the process by introducing it or by introducing it to the cold end of the heat exchanger.
15. Procédé selon l’une des revendications 6 à 14 dans lequel le premier débit d’air (8) et/ou la partie (32) du deuxième débit (6) destiné à la première colonne est refroidi dans l’échangeur de chaleur (G) jusqu’à une température au moins 5°C au- dessus de son point de rosée. 15. Method according to one of claims 6 to 14 wherein the first air flow (8) and / or the part (32) of the second flow (6) intended for the first column is cooled in the heat exchanger (G) up to a temperature at least 5 ° C above its dew point.
PCT/FR2019/052934 2018-12-21 2019-12-05 Apparatus and method for separating air by cryogenic distillation WO2020128205A1 (en)

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