EP2694898B1 - Method and device for separating air by cryogenic distillation - Google Patents

Method and device for separating air by cryogenic distillation Download PDF

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Publication number
EP2694898B1
EP2694898B1 EP12720248.9A EP12720248A EP2694898B1 EP 2694898 B1 EP2694898 B1 EP 2694898B1 EP 12720248 A EP12720248 A EP 12720248A EP 2694898 B1 EP2694898 B1 EP 2694898B1
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EP
European Patent Office
Prior art keywords
column
oxygen
pressure
air
liquid
Prior art date
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EP12720248.9A
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German (de)
French (fr)
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EP2694898A2 (en
Inventor
Benoit Davidian
Richard Dubettier-Grenier
Loïc JOLY
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Air Liquide SA
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Original Assignee
Air Liquide SA
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
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Publication of EP2694898A2 publication Critical patent/EP2694898A2/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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04006—Providing pressurised feed air or process streams within or from the air fractionation unit
    • F25J3/04048—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of cold gaseous streams, e.g. intermediate or oxygen enriched (waste) streams
    • F25J3/0406—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of cold gaseous streams, e.g. intermediate or oxygen enriched (waste) streams of nitrogen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04006—Providing pressurised feed air or process streams within or from the air fractionation unit
    • F25J3/04078—Providing pressurised feed air or process streams within or from the air fractionation unit providing pressurized products by liquid compression and vaporisation with cold recovery, i.e. so-called internal compression
    • F25J3/0409—Providing pressurised feed air or process streams within or from the air fractionation unit providing pressurized products by liquid compression and vaporisation with cold recovery, i.e. so-called internal compression of oxygen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04151—Purification and (pre-)cooling of the feed air; recuperative heat-exchange with product streams
    • F25J3/04163—Hot end purification of the feed air
    • F25J3/04169—Hot end purification of the feed air by adsorption of the impurities
    • F25J3/04181—Regenerating the adsorbents
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    • 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
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    • 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
    • F25J3/04218—Parallel arrangement of the main heat exchange line in cores having different functions, e.g. in low pressure and high pressure cores
    • F25J3/04224—Cores associated with a liquefaction or refrigeration cycle
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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    • 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
    • F25J3/04309—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
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04333—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using quasi-closed loop internal vapor compression refrigeration cycles, e.g. of intermediate or oxygen enriched (waste-)streams
    • F25J3/04351—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using quasi-closed loop internal vapor compression refrigeration cycles, 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
    • F25J3/04418—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 with thermally overlapping high and low pressure columns
    • 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
    • F25J3/04436—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 at least a triple pressure main column system
    • F25J3/04454—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 at least a triple pressure main column system a main column system not otherwise provided, e.g. serially coupling of columns or more than three pressure levels
    • 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
    • F25J3/04854—Safety aspects of operation
    • F25J3/0486—Safety aspects of operation of vaporisers for oxygen enriched liquids, e.g. purging of liquids
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/34—Processes or apparatus using separation by rectification using a side column fed by a stream from the low pressure column
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/50—Processes or apparatus using separation by rectification using multiple (re-)boiler-condensers at different heights of the column
    • F25J2200/54—Processes or apparatus using separation by rectification using multiple (re-)boiler-condensers at different heights of the column in the low pressure column of a double pressure main column system
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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    • 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
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    • 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
    • F25J2215/52—Oxygen production with multiple purity O2
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    • 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
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    • 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

Definitions

  • the present invention relates to a method and an apparatus for separating air by cryogenic distillation.
  • the invention provides in particular a method for producing pure oxygen using a double vaporizer air separation unit.
  • the method according to the invention allows the production of pure liquid oxygen (containing at least 99% mol., Or even at least 99.6% mol. Of oxygen) on an apparatus producing impure gaseous oxygen (less than 97 % mol., or even 96% mol.) at low pressure, for example in the context of a device for oxy-fuel combustion.
  • the air separation unit (ASU) diagrams producing oxygen intended for an oxycombustion coal-fired power plant generally include two vaporizers (or even three) located between the medium pressure column (MP column) and the low pressure column (BP column).
  • MP column medium pressure column
  • BP column low pressure column
  • the installation of these two vaporizers makes it possible to reduce the pressure of the MP column up to a value of the order of 3 bar absolute, which makes it possible to minimize the energy consumption of the ASU.
  • the purity of the oxygen produced by this type of plant is typically between 95 and 97 mol%. O 2 .
  • the vaporization of oxygen is ensured in a dedicated vaporizer. Liquid oxygen vaporization frigories are used to condense gaseous air. A process of this kind is known from US-A-4936099 and of EP-A-0547946 .
  • the production of pure oxygen (> 99.6%) has a greater impact on the process; in fact, the purity of the liquid produced is much higher than that of the gaseous oxygen delivered to the oxycombustion plant. It is therefore necessary to install an additional small column, recovering a fraction of the liquid flow collected in the LP column (in tank or at an intermediate plate), distilling it, which makes it possible to recover at the bottom of this additional small column the pure oxygen intended for the trade by trucks.
  • the gas return from the pure LOX column is then carried out at the same level as the liquid tapping into the LP column.
  • the pressure of the MP column is so low that it is not possible to use one of the gas flow rates entering or leaving the MP column or the LP column to condense in the tank vaporizer of the column. Additional pure LOX (their condensation temperature is too low).
  • the invention described here proposes to use as condensing fluid, a fraction of the gaseous air leaving the exchange line and which will subsequently enter the dedicated exchanger ensuring the vaporization of the production of pure oxygen. (which is designated by the term HP air).
  • HP air which is designated by the term HP air.
  • This air flow is compressed upstream of the main exchange line by the unit's booster (BAC).
  • the pressure of this flow rate is of the order of 4.5 bar abs, greater than that of the column MP, and such that its bubble temperature is greater than the equilibrium temperature of pure liquid oxygen.
  • the temperature difference between the air flow considered and pure oxygen is of the order of 2 to 3 ° C, a fairly high value, which makes it possible to install a small vaporizer.
  • the production of pure liquid oxygen is free in terms of separation energy and does not affect the separation energy from the production of impure oxygen gas. You just have to pay for the liquefaction energy.
  • the refrigeration top-up can be carried out by a liquefaction system independent of the ASU.
  • the invention provides a method for producing pure oxygen (Purity> 99.6%) on an air separation unit with double vaporizer, typically used for oxy-fuel combustion, in which the majority of the oxygen is produced. at a purity of the order of 95 to 97%.
  • Air separation units (ASU) with a single vaporizer are frequently found, where a small column producing ultra-pure oxygen is added to the bottom of the LP column.
  • the pressure of the MP column is of the order of 5 to 6 bars and the reboiling of the ultra pure LOX column is ensured by a fraction of the flow of gaseous air supplying the MP column.
  • EP-A-0793069 describes a process according to the preamble of claim 1. According to this process, air at a first pressure is used to vaporize oxygen in a vaporizer and air at a second pressure, higher than the first, is used for reboiling a column of pure oxygen.
  • US-A-5916262 describes a process for the production of oxygen with two purities, using an oxygen purification column heated in the tank by air. Liquid oxygen pressurized by a pump is also vaporized in the main exchange line by heat exchange with compressed air.
  • the present invention proposes to produce pure oxygen on a double vaporizer scheme by installing an additional pure oxygen column, the pressure of which is equal to the pressure of the LP column.
  • medium pressure and low pressure simply mean that the medium pressure column operates at a higher pressure than the low pressure column. These terms are common in the art and clear to those skilled in the art.
  • the vaporizer is not part of a distillation or exhaustion column.
  • the apparatus may include means for sending cryogenic liquid to the low pressure column from an outside source.
  • the apparatus may include a line for sending the compressed air flow from the bottom reboiler of the pure oxygen column to the vaporizer and a line for sending air from the vaporizer to the medium pressure column and / or to the low column pressure.
  • the apparatus comprises a pipe for sending the flow of compressed air from the tank reboiler of the pure oxygen column directly to the medium pressure column and / or to the low pressure column.
  • the main innovative characteristic of the invention presented here is that the reboiling of the column of pure oxygen is carried out by a fraction of the flow of gaseous air leaving the main exchange line, compressed by a booster at the pressure required for the vaporization of oxygen in the vaporizer (HP air). This fraction of HP air partially or totally condenses in the condenser of the pure oxygen column.
  • the flow of partially condensed compressed air is then sent to the product vaporizer where it finishes condensing completely.
  • the partial condensation of the pressurized air allows, with a quasi-nominal production flow of GOX and the same pressure, to operate the vaporizer in a pure column tank, then that of the vaporizer produced. Reboiling the pure liquid oxygen column is therefore free compared to the energy required to vaporize the production.
  • the pressure of this air flow is greater than the pressure of the MP column (typically of the order of 4.5 bar abs. Versus 3.2 bar abs.).
  • the impure gas reflux from the pure oxygen column is mixed with the gas flow from the produced vaporizer, the two flows constituting the nominal production flow rate of the impure GOX.
  • the pure liquid is taken from the bottom of the column of pure oxygen. It also serves as a deconcentration purge of the entire device.
  • Addition of frigories can be provided by an independent liquefier, for example by production of liquid nitrogen, from pure nitrogen (from a minaret), which would then be added in liquid form in the device. If there is no production of pure liquid nitrogen, it is possible to envisage liquefying residual nitrogen in an independent liquefier.
  • the air is separated in an ASU comprising a double air separation column, comprising a medium pressure column 23 and a low pressure column 25.
  • Refrigerants for the separation are supplied by expansion of medium pressure nitrogen in a turbine 47
  • the device includes a column of pure liquid oxygen 49, a pump 57, a vaporizer 51 and an exchange line 63.
  • the air 1 is pressurized by a compressor 3 at a pressure between 2.5 and 4.5 bar abs.
  • the air is then purified in a purification unit 5 by adsorption.
  • the purified air 7 is divided into two parts. Part 9 is overpressed in a booster 13 to a pressure of between 4. and 20 bar abs and then cooled in the exchange line 63 until the cold end.
  • the air 9 is divided into two fractions 15, 17.
  • a fraction 15 is sent to the vaporizer 51 where it is used to partially vaporize liquid oxygen comprising at most 97% mol. oxygen, to produce gaseous oxygen 59 which heats up in the exchange line 63.
  • This gas 59 is sent to an oxy-fuel unit.
  • An oxygen-rich liquid 53 is withdrawn from the vaporizer 51 as a purge.
  • the air is condensed.
  • the other fraction of the air 17 is sent to the tank reboiler 61 of the pure oxygen column 49.
  • This column comprises the tank reboiler and means for exchanging heat and material above this reboiler.
  • Liquid oxygen 65 comprising at most 97 mol%. oxygen is sent to the top of the column 49 and is enriched to form the liquid product 71 withdrawn from the tank and containing at least 98% mol. oxygen.
  • the gaseous oxygen 67 at the head of the column 49 is sent to the bottom of the low pressure column 25.
  • the condensed air 17 mixes with the condensed air coming from the vaporizer 51 and, after expansion in a valve 21, is sent to the MP 23 column, which operates at between 2.5 and 4.5 bar abs.
  • Another part 11 of the air is cooled in the exchange line 63, is sent to the tank reboiler 35 of the LP column 25, at least partially condenses there and is sent to the tank of the MP column 23, in below the liquid air inlet point 19.
  • Liquid enriched in oxygen 27 is withdrawn from the tank of the MP column 23, cooled in the sub-cooler 33, expanded and sent to the column BP 25.
  • Liquid 29 is withdrawn from the column MP 23, cooled in the sub- cooler 33, expanded and sent to the LP column 25.
  • Liquid rich in nitrogen 31 is withdrawn from the head of the MP column 23, cooled in the sub-cooler 33, expanded and sent to the head of the BP column 25.
  • Low pressure nitrogen 39 is drawn off at the head of the LP column, heated in the sub-cooler 33 and heated in the exchange line 63.
  • Medium pressure nitrogen 41 is divided into two to form a part 43 and a part 45.
  • Part 43 is used to heat the intermediate reboiler 37 of the low pressure column 25.
  • Part 45 heats up in the exchange line 63 , is expanded in the turbine 47 and is returned to the exchange line 63.
  • Liquid oxygen is withdrawn from the tank of the LP column and divided into two.
  • Part 55 is pressurized in the pump 57 upstream of the vaporizer 51 and the rest 65 is sent to the head of the column of pure oxygen 49 without having been pressurized.
  • the head of the pure oxygen column 49 is therefore at the same pressure as the tank of the low pressure column 25. All or part of the purge liquid 53 can also supply the head of the column 49.
  • a flow of cryogenic liquid 69 for example liquid nitrogen, is sent to the head of the LP column to keep the process cool.
  • the process of Figure 1 bis differs from that of the Figure 1 in that the column 49 is supplied at the head exclusively by the purge 53 of the vaporizer 51, following an expansion step in a valve.
  • the tank reboiler 61 of the column 49 is always heated by the supercharged air 17, the air thus condensed being mixed with the supercharged air 15 which served to heat the vaporizer 51. It is also possible to supply the column with purge liquid 53 and liquid oxygen 65 coming from the tank of the low pressure column 25.
  • the process of Figure 2 differs from that of the Figure 1 in that the air flow 9 is sent first to the tank vaporizer 61 of the pure oxygen column 49 and then to the vaporizer 51 where it condenses.
  • the air thus formed is expanded in the valve 21 and sent to the medium pressure column 23.
  • the air fraction 11 cools in the exchange line 11 and is sent to the tank of the medium pressure column 23 without having been expanded or compressed downstream of the compressor 3.
  • the intermediate reboiler 37 is always heated by medium pressure nitrogen 43 but another part of the medium pressure nitrogen 73 is compressed in a cold booster 71 from a cryogenic temperature and sent to the tank reboiler 35.
  • the condensed nitrogen is expanded in a valve 36 and sent to the head of the MP 23 column.
  • the tank oxygen 55 of the low pressure column is entirely pressurized in the pump 57 sent to the vaporizer 51 where it partially vaporizes.
  • the vaporized gas constitutes the oxygen product gaseous 59 containing less than 97 mol%. oxygen.
  • the non-vaporized liquid 53 feeds the head of the column 49.
  • the gaseous oxygen 67 at the head of the column 49 is mixed with the gaseous oxygen 59.
  • the liquid oxygen 71 constitutes the liquid product. In this case, the pure oxygen column 49 does not operate at the same pressure as the BP column 25.
  • the process of Figure 1 or 1 bis can use nitrogen to heat the tank reboiler 35 and the process of Figure 2 can use air to heat the tank reboiler 35.

Description

La présente invention est relative à un procédé et à un appareil de séparation d'air par distillation cryogénique.The present invention relates to a method and an apparatus for separating air by cryogenic distillation.

L'invention propose en particulier une méthode de production d'oxygène pur utilisant une unité de séparation d'air à double vaporiseur.The invention provides in particular a method for producing pure oxygen using a double vaporizer air separation unit.

Le procédé selon l'invention permet la production d'oxygène liquide pur (contenant au moins 99% mol., voire au moins 99,6% mol. d'oxygène) sur un appareil produisant de l'oxygène gazeux impur (inférieur à 97% mol., voire à 96% mol.) à faible pression, par exemple dans le cadre d'un appareil pour l'oxycombustion.The method according to the invention allows the production of pure liquid oxygen (containing at least 99% mol., Or even at least 99.6% mol. Of oxygen) on an apparatus producing impure gaseous oxygen (less than 97 % mol., or even 96% mol.) at low pressure, for example in the context of a device for oxy-fuel combustion.

Les schémas d'unités de séparation d'air (ASU) produisant l'oxygène destiné à une centrale à charbon à oxycombustion comprennent en général deux vaporiseurs (voire trois) situés entre la colonne moyenne pression (colonne MP) et la colonne basse pression (colonne BP). L'installation de ces deux vaporiseurs permet de réduire la pression de la colonne MP jusqu'à une valeur de l'ordre de 3 bar absolus, ce qui permet de minimiser la consommation énergétique de l'ASU.The air separation unit (ASU) diagrams producing oxygen intended for an oxycombustion coal-fired power plant generally include two vaporizers (or even three) located between the medium pressure column (MP column) and the low pressure column ( BP column). The installation of these two vaporizers makes it possible to reduce the pressure of the MP column up to a value of the order of 3 bar absolute, which makes it possible to minimize the energy consumption of the ASU.

La pureté de l'oxygène produit par ce type de centrale est typiquement comprise entre 95 et 97% mol. O2. La vaporisation de l'oxygène est assurée dans un vaporiseur dédié. Les frigories de vaporisation de l'oxygène liquide sont utilisées pour condenser de l'air gazeux. Un procédé de ce genre est connu de US-A-4936099 et de EP-A-0547946 .The purity of the oxygen produced by this type of plant is typically between 95 and 97 mol%. O 2 . The vaporization of oxygen is ensured in a dedicated vaporizer. Liquid oxygen vaporization frigories are used to condense gaseous air. A process of this kind is known from US-A-4936099 and of EP-A-0547946 .

Par ailleurs, on peut tenter de profiter de l'installation d'un tel ASU pour produire de l'azote liquide pur et de l'oxygène pur (pureté de l'ordre de 99,6%), stockés puis destinés au commerce liquide par camions.Furthermore, we can try to take advantage of the installation of such an ASU to produce pure liquid nitrogen and pure oxygen (purity of the order of 99.6%), stored and then intended for liquid trade. by trucks.

La production d'azote liquide ne pose pas de difficulté majeure, car il suffit de rajouter des plateaux en haut de la colonne MP pour atteindre la pureté désirée, sans impact sur le reste du procédé de l'ASU, à part le coût de l'énergie de liquéfaction.The production of liquid nitrogen does not pose any major difficulty, because it suffices to add trays at the top of the MP column to achieve the desired purity, without impacting the rest of the ASU process, apart from the cost of l liquefaction energy.

En revanche, la production d'oxygène pur (> 99,6%) induit un impact plus important sur le procédé ; en effet, la pureté du liquide produit est nettement supérieure à celle de l'oxygène gazeux livré à la centrale à oxycombustion. Il est donc nécessaire d'installer une petite colonne supplémentaire, récupérant une fraction du débit liquide recueilli dans la colonne BP (en cuve ou à un plateau intermédiaire), le distillant, ce qui permet de récupérer en bas de cette petite colonne additionnelle l'oxygène pur destiné au commerce par camions. Le retour gazeux depuis la colonne de LOX pur s'effectue alors au même niveau que le piquage de liquide dans la colonne BP.On the other hand, the production of pure oxygen (> 99.6%) has a greater impact on the process; in fact, the purity of the liquid produced is much higher than that of the gaseous oxygen delivered to the oxycombustion plant. It is therefore necessary to install an additional small column, recovering a fraction of the liquid flow collected in the LP column (in tank or at an intermediate plate), distilling it, which makes it possible to recover at the bottom of this additional small column the pure oxygen intended for the trade by trucks. The gas return from the pure LOX column is then carried out at the same level as the liquid tapping into the LP column.

Néanmoins, la pression de la colonne MP est tellement basse qu'il n'est pas possible d'utiliser un des débits gazeux entrant ou sortant de la colonne MP ni de la colonne BP pour se condenser dans le vaporiseur de cuve de la colonne de LOX pure additionnelle (leur température de condensation est trop basse).However, the pressure of the MP column is so low that it is not possible to use one of the gas flow rates entering or leaving the MP column or the LP column to condense in the tank vaporizer of the column. Additional pure LOX (their condensation temperature is too low).

L'invention décrite ici propose d'utiliser comme fluide se condensant, une fraction de l'air gazeux sortant de la ligne d'échange et qui va par la suite entrer dans l'échangeur dédié assurant la vaporisation de la production d'oxygène pur (qu'on désigne par le terme d'air HP). Ce débit d'air est comprimé en amont de la ligne d'échange principale par le surpresseur (BAC) de l'unité.The invention described here proposes to use as condensing fluid, a fraction of the gaseous air leaving the exchange line and which will subsequently enter the dedicated exchanger ensuring the vaporization of the production of pure oxygen. (which is designated by the term HP air). This air flow is compressed upstream of the main exchange line by the unit's booster (BAC).

La pression de ce débit est de l'ordre de 4,5 bars abs, supérieure à celle de la colonne MP, et telle que sa température de bulle soit supérieure à la température d'équilibre de l'oxygène liquide pur.The pressure of this flow rate is of the order of 4.5 bar abs, greater than that of the column MP, and such that its bubble temperature is greater than the equilibrium temperature of pure liquid oxygen.

L'écart de température entre le débit d'air considéré et l'oxygène pur est de l'ordre de 2 à 3°C, valeur assez élevée, ce qui permet d'installer un vaporiseur de petite taille.The temperature difference between the air flow considered and pure oxygen is of the order of 2 to 3 ° C, a fairly high value, which makes it possible to install a small vaporizer.

Dans l'invention, selon la variante de la Figure 1, la production d'oxygène liquide pur est gratuite en termes d'énergie de séparation et ne joue pas sur l'énergie de séparation de la production de l'oxygène gazeux impur. Il faut juste payer l'énergie de liquéfaction. L'appoint frigorifique peut être effectué par un système de liquéfaction indépendant de l'ASU.In the invention, according to the variant of the Figure 1 , the production of pure liquid oxygen is free in terms of separation energy and does not affect the separation energy from the production of impure oxygen gas. You just have to pay for the liquefaction energy. The refrigeration top-up can be carried out by a liquefaction system independent of the ASU.

L'invention propose une méthode permettant de produire de l'oxygène pur (Pureté > 99,6%) sur une unité de séparation d'air à double vaporiseur, typiquement utilisée pour l'oxycombustion, dont la majorité de l'oxygène est produite à une pureté de l'ordre de 95 à 97%.The invention provides a method for producing pure oxygen (Purity> 99.6%) on an air separation unit with double vaporizer, typically used for oxy-fuel combustion, in which the majority of the oxygen is produced. at a purity of the order of 95 to 97%.

En effet, sur ce type de procédé, hormis l'air HP, il n'existe pas de fluide disponible à température de condensation suffisamment haute pour réaliser le rebouillage de la colonne d'oxygène pur.In fact, on this type of process, apart from HP air, there is no fluid available at a condensation temperature high enough to reboil the column of pure oxygen.

A l'heure actuelle, il n'existe pas de solution référencée pour produire de l'oxygène pur sur une unité de séparation d'air à double vaporiseur.At present, there is no solution referenced for producing pure oxygen on a double vaporizer air separation unit.

On pourrait utiliser, dans ce but, un débit soutiré à un niveau intermédiaire (et donc à température plus élevée) dans la ligne d'échange principale, mais ceci complexifierait le procédé. Ce serait également moins efficace car il s'agirait d'utiliser de la chaleur sensible contre de la chaleur latente.One could use, for this purpose, a flow withdrawn at an intermediate level (and therefore at a higher temperature) in the main exchange line, but this would complicate the process. It would also be less effective because it would involve using sensible heat against latent heat.

On trouve fréquemment des unités de séparation d'air (ASU) à un seul vaporiseur, où une petite colonne produisant de production l'oxygène ultra-pur est rajoutée en cuve de la colonne BP. Dans ce cas, la pression de la colonne MP est de l'ordre de 5 à 6 bars et le rebouillage de la colonne de LOX ultra pur est assuré par une fraction du débit d'air gazeux alimentant la colonne MP.Air separation units (ASU) with a single vaporizer are frequently found, where a small column producing ultra-pure oxygen is added to the bottom of the LP column. In this case, the pressure of the MP column is of the order of 5 to 6 bars and the reboiling of the ultra pure LOX column is ensured by a fraction of the flow of gaseous air supplying the MP column.

EP-A-0793069 décrit un procédé selon le préambule de la revendication 1. Selon ce procédé, de l'air à une première pression est utilisé pour vaporiser de l'oxygène dans un vaporiseur et de l'air à une deuxième pression, plus élevée que la première, est utilisée pour le rebouillage d'une colonne d'oxygène pur. EP-A-0793069 describes a process according to the preamble of claim 1. According to this process, air at a first pressure is used to vaporize oxygen in a vaporizer and air at a second pressure, higher than the first, is used for reboiling a column of pure oxygen.

US-A-5916262 décrit un procédé de production d'oxygène à deux puretés, utilisant une colonne d'épuration d'oxygène chauffé en cuve par de l'air. De l'oxygène liquide pressurisé par pompe est également vaporisé dans la ligne d'échange principale par échange de chaleur avec de l'air surpressé. US-A-5916262 describes a process for the production of oxygen with two purities, using an oxygen purification column heated in the tank by air. Liquid oxygen pressurized by a pump is also vaporized in the main exchange line by heat exchange with compressed air.

La présente invention propose de produire de l'oxygène pur sur un schéma à double vaporiseur en installant une colonne d'oxygène pur supplémentaire, dont la pression est égale à la pression de la colonne BP.The present invention proposes to produce pure oxygen on a double vaporizer scheme by installing an additional pure oxygen column, the pressure of which is equal to the pressure of the LP column.

Selon un objet de l'invention, il est prévu un procédé selon la revendication 1.According to an object of the invention, there is provided a method according to claim 1.

Selon d'autres aspects facultatifs de l'invention :

  • on pressurise le premier débit de liquide riche en oxygène en amont du vaporiseur.
  • on divise de l'air surpressé à la deuxième pression en deux parties, on envoie une première partie d'air surpressé à la deuxième pression au rebouilleur de cuve de la colonne d'oxygène pur et on envoie une deuxième partie d'air surpressé à la deuxième pression au vaporiseur.
  • on envoie de l'air à la première pression au rebouilleur de cuve de la colonne basse pression pour le chauffer.
  • tout l'air est divisé en un débit à la première pression et un débit à la deuxième pression en amont de la ligne d'échange.
  • le premier débit de liquide riche en oxygène se vaporise partiellement dans le vaporiseur, le liquide formé constituant le deuxième débit de liquide riche en oxygène.
  • le débit d'air surpressé à la deuxième pression chauffe d'abord le rebouilleur de cuve de la colonne d'oxygène pur et ensuite le vaporiseur.
  • de l'air à la première pression se refroidit dans la ligne d'échange et est envoyé sous forme gazeuse à la colonne moyenne pression.
  • un liquide cryogénique d'une source auxiliaire est envoyé à la double colonne.
According to other optional aspects of the invention:
  • the first flow of oxygen-rich liquid is pressurized upstream of the vaporizer.
  • divide the compressed air at the second pressure into two parts, send a first part of the compressed air at the second pressure to the tank reboiler of the pure oxygen column and send a second part of the compressed air to the second press on the vaporizer.
  • air is sent at the first pressure to the reboiler of the low pressure column tank to heat it.
  • all the air is divided into a flow at the first pressure and a flow at the second pressure upstream of the exchange line.
  • the first flow of oxygen-rich liquid partially vaporizes in the vaporizer, the liquid formed constituting the second flow of oxygen-rich liquid.
  • the flow of air boosted at the second pressure first heats the tank reboiler of the pure oxygen column and then the vaporizer.
  • air at the first pressure cools in the exchange line and is sent in gaseous form to the medium pressure column.
  • a cryogenic liquid from an auxiliary source is sent to the double column.

Les termes « moyenne pression » et « basse pression » désignent simplement que la colonne moyenne pression opère à une pression plus élevée que la colonne basse pression. Ces termes sont communs dans l'art et clairs pour l'homme de l'art.The terms "medium pressure" and "low pressure" simply mean that the medium pressure column operates at a higher pressure than the low pressure column. These terms are common in the art and clear to those skilled in the art.

Selon un autre objet de l'invention, il est prévu un appareil selon la revendication 6. Selon d'autres objets facultatifs de l'invention, il est prévu que l'appareil comprenne :

  • les moyens pour envoyer l'air surpressé du surpresseur au vaporiseur sont reliés au rebouilleur de cuve de la colonne d'oxygène pur de sorte que l'air destiné au vaporiseur passe à travers le rebouilleur de cuve de la colonne d'oxygène pur.
  • les moyens pour envoyer un deuxième débit de liquide riche en oxygène en tête de la colonne d'oxygène pur sont constitués par la conduite pour envoyer un liquide de cuve de la colonne basse pression en tête de la colonne d'oxygène pur.
  • des moyens pour diviser l'air surpressé à la deuxième pression en deux parties, les moyens pour envoyer de l'air surpressé à la deuxième pression du surpresseur au vaporiseur et la conduite pour envoyer un débit d'air surpressé à la deuxième pression au rebouilleur de cuve de la colonne d'oxygène pur étant reliés de sorte qu'une partie d'air surpressé est envoyée au rebouilleur de cuve de la colonne d'oxygène pur et une autre partie d'air surpressé est envoyée au vaporiseur.
According to another object of the invention, there is provided an apparatus according to claim 6. According to other optional objects of the invention, it is intended that the apparatus comprises:
  • the means for sending the compressed air from the booster to the vaporizer are connected to the tank reboiler of the pure oxygen column so that the air intended for the vaporizer passes through the tank reboiler of the pure oxygen column.
  • the means for sending a second flow of liquid rich in oxygen at the head of the pure oxygen column consist of the pipe for sending a liquid from the bottom of the low pressure column at the head of the column of pure oxygen.
  • means for dividing the compressed air at the second pressure into two parts, the means for sending compressed air at the second pressure from the supercharger to the vaporizer and the pipe for sending a flow of compressed air at the second pressure to the reboiler from the bottom of the pure oxygen column being connected so that part of the compressed air is sent to the reboiler of the bottom of the pure oxygen column and another part of the compressed air is sent to the vaporizer.

Le vaporiseur ne fait pas partie d'une colonne de distillation ou d'épuisement.The vaporizer is not part of a distillation or exhaustion column.

L'appareil peut comprendre des moyens pour envoyer un liquide cryogénique à la colonne basse pression d'une source extérieure.The apparatus may include means for sending cryogenic liquid to the low pressure column from an outside source.

L'appareil peut comprendre une conduite pour envoyer le débit d'air surpressé du rebouilleur de cuve de la colonne d'oxygène pur au vaporiseur et une conduite pour envoyer l'air du vaporiseur à la colonne moyenne pression et/ou à la colonne basse pression.The apparatus may include a line for sending the compressed air flow from the bottom reboiler of the pure oxygen column to the vaporizer and a line for sending air from the vaporizer to the medium pressure column and / or to the low column pressure.

Selon une autre variante l'appareil comprend une conduite pour envoyer le débit d'air surpressé du rebouilleur de cuve de la colonne d'oxygène pur directement à la colonne moyenne pression et/ou à la colonne basse pression.According to another variant, the apparatus comprises a pipe for sending the flow of compressed air from the tank reboiler of the pure oxygen column directly to the medium pressure column and / or to the low pressure column.

La principale caractéristique innovante de l'invention présentée ici est que le rebouillage de la colonne d'oxygène pur est réalisé par une fraction du débit d'air gazeux sortant de la ligne d'échange principale, comprimée par un surpresseur à la pression requise pour la vaporisation d'oxygène dans le vaporiseur (air HP). Cette fraction d'air HP se condense partiellement ou totalement dans le condenseur de la colonne d'oxygène pur.The main innovative characteristic of the invention presented here is that the reboiling of the column of pure oxygen is carried out by a fraction of the flow of gaseous air leaving the main exchange line, compressed by a booster at the pressure required for the vaporization of oxygen in the vaporizer (HP air). This fraction of HP air partially or totally condenses in the condenser of the pure oxygen column.

Selon une variante, le débit d'air surpressé partiellement condensé, éventuellement après avoir séparé la partie condensée (qui est alors envoyée dans la colonne MP), est ensuite envoyé dans le vaporiseur produit où il finit de se condenser totalement. La condensation partielle de l'air surpressé permet, avec un débit quasi-nominal de production du GOX et la même pression, de faire fonctionner le vaporiseur en cuve de colonne pur, puis celui du vaporiseur produit. Le rebouillage de la colonne d'oxygène liquide pur est donc gratuit par rapport à l'énergie nécessaire pour vaporiser la production.According to a variant, the flow of partially condensed compressed air, possibly after having separated the condensed part (which is then sent to the column MP), is then sent to the product vaporizer where it finishes condensing completely. The partial condensation of the pressurized air allows, with a quasi-nominal production flow of GOX and the same pressure, to operate the vaporizer in a pure column tank, then that of the vaporizer produced. Reboiling the pure liquid oxygen column is therefore free compared to the energy required to vaporize the production.

La pression de ce débit d'air est supérieure à la pression de la colonne MP (typiquement de l'ordre de 4,5 bar abs. contre 3,2 bar abs.).The pressure of this air flow is greater than the pressure of the MP column (typically of the order of 4.5 bar abs. Versus 3.2 bar abs.).

On prélève une partie du liquide impur dans le vaporiseur produit (au même niveau et à la place de la purge de déconcentration du vaporiseur) que l'on envoie dans la colonne d'oxygène liquide pur qui est une colonne à distiller sensiblement à la même pression que le vaporiseur produit..One takes part of the impure liquid in the vaporizer produced (at the same level and in place of the deconcentration purge of the vaporizer) which is sent to the column of pure liquid oxygen which is a column to be distilled substantially at the same pressure that the vaporizer produces ..

Le reflux gazeux impur issu de la colonne d'oxygène pur est mélangé avec le flux gazeux issu du vaporiseur produit, les deux flux constituant le débit nominal de production du GOX impur.The impure gas reflux from the pure oxygen column is mixed with the gas flow from the produced vaporizer, the two flows constituting the nominal production flow rate of the impure GOX.

Le liquide pur est prélevé en cuve de la colonne d'oxygène pur. Il sert aussi de purge de déconcentration de l'ensemble de l'appareil.The pure liquid is taken from the bottom of the column of pure oxygen. It also serves as a deconcentration purge of the entire device.

L'appoint de frigories peut être apporté par un liquéfacteur indépendant, par exemple par production d'azote liquide, à partir d'azote pur (issu d'un minaret), qui serait alors rajouté sous forme liquide dans l'appareil. S'il n'y a pas de production d'azote pur liquide, on peut envisager de liquéfier de l'azote résiduaire dans un liquéfacteur indépendant.Addition of frigories can be provided by an independent liquefier, for example by production of liquid nitrogen, from pure nitrogen (from a minaret), which would then be added in liquid form in the device. If there is no production of pure liquid nitrogen, it is possible to envisage liquefying residual nitrogen in an independent liquefier.

Si la production de liquide pur est faible, on peut aussi envisager d'avoir un système de production de froid intégré à l'ASU.If the production of pure liquid is low, we can also consider having a cold production system integrated into the ASU.

L'invention sera décrite en plus de détail en se référant à la Figure 1 qui illustre un procédé de séparation d'air qui n'est pas selon l'invention et aux Figures 1bis et 2, qui illustrent des procédés de séparation d'air selon l'invention.The invention will be described in more detail with reference to the Figure 1 which illustrates an air separation process which is not according to the invention and to Figures 1bis and 2 , which illustrate air separation methods according to the invention.

Dans la Figure 1, l'air est séparé dans un ASU comprenant une double colonne de séparation d'air, comprenant une colonne moyenne pression 23 et une colonne basse pression 25. Des frigories pour la séparation sont fournies par détente d'azote moyenne pression dans une turbine 47. L'appareil comprend une colonne d'oxygène liquide pur 49, une pompe 57, un vaporiseur 51 et une ligne d'échange 63.In the Figure 1 , the air is separated in an ASU comprising a double air separation column, comprising a medium pressure column 23 and a low pressure column 25. Refrigerants for the separation are supplied by expansion of medium pressure nitrogen in a turbine 47 The device includes a column of pure liquid oxygen 49, a pump 57, a vaporizer 51 and an exchange line 63.

L'air 1 est pressurisé par un compresseur 3 à une pression entre 2,5 et 4,5 bars abs. L'air est ensuite épuré dans une unité d'épuration 5 par adsorption. L'air épuré 7 est divisé en deux parties. Une partie 9 est surpressée dans un surpresseur 13 jusqu'à une pression d'entre 4.et 20 bars abs et puis refroidie dans la ligne d'échange 63 jusqu'au bout froid. L'air 9 est divisé en deux fractions 15, 17. Une fraction 15 est envoyée au vaporiseur 51 où elle sert à vaporiser partiellement de l'oxygène liquide comprenant au plus 97 % mol. d'oxygène, pour produire l'oxygène gazeux 59 qui se réchauffe dans la ligne d'échange 63. Ce gaz 59 est envoyé à une unité d'oxycombustion. Un liquide riche en oxygène 53 est soutiré du vaporiseur 51 comme purge. L'air se trouve condensé. L'autre fraction de l'air 17 est envoyée au rebouilleur de cuve 61 de la colonne d'oxygène pur 49. Cette colonne comporte le rebouilleur de cuve et des moyens d'échange de chaleur et de matière au-dessus de ce rebouilleur. De l'oxygène liquide 65 comprenant au plus 97% mol. d'oxygène est envoyé en tête de la colonne 49 et s'enrichit pour former le produit liquide 71 soutiré en cuve et contenant au moins 98% mol. d'oxygène. L'oxygène gazeux 67 de tête de la colonne 49 est envoyé en cuve de la colonne basse pression 25. L'air condensé 17 se mélange avec l'air condensé provenant du vaporiseur 51 et, après détente dans une vanne 21, est envoyé à la colonne MP 23, qui opère à entre 2,5 et 4,5 bars abs.The air 1 is pressurized by a compressor 3 at a pressure between 2.5 and 4.5 bar abs. The air is then purified in a purification unit 5 by adsorption. The purified air 7 is divided into two parts. Part 9 is overpressed in a booster 13 to a pressure of between 4. and 20 bar abs and then cooled in the exchange line 63 until the cold end. The air 9 is divided into two fractions 15, 17. A fraction 15 is sent to the vaporizer 51 where it is used to partially vaporize liquid oxygen comprising at most 97% mol. oxygen, to produce gaseous oxygen 59 which heats up in the exchange line 63. This gas 59 is sent to an oxy-fuel unit. An oxygen-rich liquid 53 is withdrawn from the vaporizer 51 as a purge. The air is condensed. The other fraction of the air 17 is sent to the tank reboiler 61 of the pure oxygen column 49. This column comprises the tank reboiler and means for exchanging heat and material above this reboiler. Liquid oxygen 65 comprising at most 97 mol%. oxygen is sent to the top of the column 49 and is enriched to form the liquid product 71 withdrawn from the tank and containing at least 98% mol. oxygen. The gaseous oxygen 67 at the head of the column 49 is sent to the bottom of the low pressure column 25. The condensed air 17 mixes with the condensed air coming from the vaporizer 51 and, after expansion in a valve 21, is sent to the MP 23 column, which operates at between 2.5 and 4.5 bar abs.

Une autre partie 11 de l'air est refroidie dans la ligne d'échange 63, est envoyée au rebouilleur de cuve 35 de la colonne BP 25, s'y condense au moins partiellement et est envoyée en cuve de la colonne MP 23, en dessous du point d'arrivée d'air liquide 19.Another part 11 of the air is cooled in the exchange line 63, is sent to the tank reboiler 35 of the LP column 25, at least partially condenses there and is sent to the tank of the MP column 23, in below the liquid air inlet point 19.

Du liquide enrichi en oxygène 27 est soutiré de la cuve de la colonne MP 23, refroidi dans le sous-refroidisseur 33, détendu et envoyé à la colonne BP 25. Du liquide 29 est soutiré de la colonne MP 23, refroidi dans le sous-refroidisseur 33, détendu et envoyé à la colonne BP 25. Du liquide riche en azote 31 est soutiré de la tête de la colonne MP 23, refroidi dans le sous-refroidisseur 33, détendu et envoyé à la tête de la colonne BP 25.Liquid enriched in oxygen 27 is withdrawn from the tank of the MP column 23, cooled in the sub-cooler 33, expanded and sent to the column BP 25. Liquid 29 is withdrawn from the column MP 23, cooled in the sub- cooler 33, expanded and sent to the LP column 25. Liquid rich in nitrogen 31 is withdrawn from the head of the MP column 23, cooled in the sub-cooler 33, expanded and sent to the head of the BP column 25.

De l'azote basse pression 39 est soutiré en tête de la colonne BP, réchauffé dans le sous-refroidisseur 33 et réchauffé dans la ligne d'échange 63.Low pressure nitrogen 39 is drawn off at the head of the LP column, heated in the sub-cooler 33 and heated in the exchange line 63.

De l'azote moyenne pression 41 est divisé en deux pour former une partie 43 et une partie 45. La partie 43 sert à chauffer le rebouilleur intermédiaire 37 de la colonne basse pression 25. La partie 45 se réchauffe dans la ligne d'échange 63, est détendue dans la turbine 47 et est renvoyée à la ligne d'échange 63. De l'oxygène liquide est soutiré de la cuve de la colonne BP et divisé en deux. Une partie 55 est pressurisée dans la pompe 57 en amont du vaporiseur 51 et le reste 65 est envoyé en tête de la colonne d'oxygène pur 49 sans avoir été pressurisé. La tête de la colonne d'oxygène pur 49 se trouve donc à la même pression que la cuve de la colonne basse pression 25. Tout ou une partie du liquide de purge 53 peut également alimenter la tête de la colonne 49.Medium pressure nitrogen 41 is divided into two to form a part 43 and a part 45. Part 43 is used to heat the intermediate reboiler 37 of the low pressure column 25. Part 45 heats up in the exchange line 63 , is expanded in the turbine 47 and is returned to the exchange line 63. Liquid oxygen is withdrawn from the tank of the LP column and divided into two. Part 55 is pressurized in the pump 57 upstream of the vaporizer 51 and the rest 65 is sent to the head of the column of pure oxygen 49 without having been pressurized. The head of the pure oxygen column 49 is therefore at the same pressure as the tank of the low pressure column 25. All or part of the purge liquid 53 can also supply the head of the column 49.

Un débit de liquide cryogénique 69, par exemple de l'azote liquide, est envoyé en tête de la colonne BP pour tenir le procédé en froid.A flow of cryogenic liquid 69, for example liquid nitrogen, is sent to the head of the LP column to keep the process cool.

Le procédé de la Figure 1 bis diffère de celui de la Figure 1 en ce que la colonne 49 est alimentée en tête exclusivement par la purge 53 du vaporiseur 51, suite à une étape de détente dans une vanne. Le rebouilleur de cuve 61 de la colonne 49 est toujours chauffé par l'air surpressé 17, l'air ainsi condensé étant mélangé avec l'air surpressé 15 qui a servi à chauffer le vaporiseur 51. Il est également possible d'alimenter la colonne avec du liquide de purge 53 et de l'oxygène liquide 65 provenant de la cuve de la colonne basse pression 25.The process of Figure 1 bis differs from that of the Figure 1 in that the column 49 is supplied at the head exclusively by the purge 53 of the vaporizer 51, following an expansion step in a valve. The tank reboiler 61 of the column 49 is always heated by the supercharged air 17, the air thus condensed being mixed with the supercharged air 15 which served to heat the vaporizer 51. It is also possible to supply the column with purge liquid 53 and liquid oxygen 65 coming from the tank of the low pressure column 25.

Le procédé de la Figure 2 diffère de celui de la Figure 1 en ce que le débit d'air 9 est envoyé d'abord au vaporiseur de cuve 61 de la colonne d'oxygène pur 49 et ensuite au vaporiseur 51 où il se condense. L'air ainsi formé est détendu dans la vanne 21 et envoyé à la colonne moyenne pression 23. La fraction d'air 11 se refroidit dans la ligne d'échange 11 et est envoyée à la cuve de la colonne moyenne pression 23 sans avoir été détendue ou comprimée en aval du compresseur 3.The process of Figure 2 differs from that of the Figure 1 in that the air flow 9 is sent first to the tank vaporizer 61 of the pure oxygen column 49 and then to the vaporizer 51 where it condenses. The air thus formed is expanded in the valve 21 and sent to the medium pressure column 23. The air fraction 11 cools in the exchange line 11 and is sent to the tank of the medium pressure column 23 without having been expanded or compressed downstream of the compressor 3.

Le rebouilleur intermédiaire 37 est toujours chauffé par de l'azote moyenne pression 43 mais une autre partie de l'azote moyenne pression 73 est comprimée dans un surpresseur froid 71 à partir d'une température cryogénique et envoyée au rebouilleur de cuve 35. L'azote condensé est détendu dans une vanne 36 et envoyé en tête de la colonne MP 23. L'oxygène de cuve 55 de la colonne basse pression est entièrement pressurisé dans la pompe 57 envoyé au vaporiseur 51 où il se vaporise partiellement. Le gaz vaporisé constitue le produit d'oxygène gazeux 59 contenant moins que 97% mol. d'oxygène. Le liquide non-vaporisé 53 alimente la tête de la colonne 49. L'oxygène gazeux 67 de tête de la colonne 49 est mélangé avec l'oxygène gazeux 59. L'oxygène liquide 71 constitue le produit liquide. Dans ce cas, la colonne d'oxygène pur 49 n'opère pas à la même pression que la colonne BP 25.The intermediate reboiler 37 is always heated by medium pressure nitrogen 43 but another part of the medium pressure nitrogen 73 is compressed in a cold booster 71 from a cryogenic temperature and sent to the tank reboiler 35. The condensed nitrogen is expanded in a valve 36 and sent to the head of the MP 23 column. The tank oxygen 55 of the low pressure column is entirely pressurized in the pump 57 sent to the vaporizer 51 where it partially vaporizes. The vaporized gas constitutes the oxygen product gaseous 59 containing less than 97 mol%. oxygen. The non-vaporized liquid 53 feeds the head of the column 49. The gaseous oxygen 67 at the head of the column 49 is mixed with the gaseous oxygen 59. The liquid oxygen 71 constitutes the liquid product. In this case, the pure oxygen column 49 does not operate at the same pressure as the BP column 25.

Le procédé de la Figure 1 ou 1 bis peut utiliser de l'azote pour chauffer le rebouilleur de cuve 35 et le procédé de la Figure 2 peut utiliser de l'air pour chauffer le rebouilleur de cuve 35.The process of Figure 1 or 1 bis can use nitrogen to heat the tank reboiler 35 and the process of Figure 2 can use air to heat the tank reboiler 35.

Claims (11)

  1. Method for separating air by cryogenic distillation in a separation unit comprising a medium-pressure column (23) and a low-pressure column (25), thermally connected to each other, the low-pressure column comprising a sump reboiler (35) and an intermediate reboiler (37) and a column of pure oxygen (49) wherein:
    i) gaseous air purified and then cooled is sent at a first pressure in an exchange line to the medium-pressure column,
    ii) oxygen-enriched liquid and nitrogen-enriched liquid are sent from the medium-pressure column to the low-pressure column,
    iii) nitrogen-enriched gas is taken from the low-pressure column,
    iv) oxygen-enriched liquid containing at most 97% mol. of oxygen is taken from the sump of the low-pressure column,
    v) a first flow of oxygen-enriched liquid is sent to a vaporiser (51) and the gaseous oxygen thus formed is sent to the exchange line,
    vi) a second flow of oxygen-enriched liquid is sent to the top of the column of pure oxygen, having a sump reboiler (61), where it is purified to form a sump liquid containing at least 98% mol. of oxygen,
    vii) a flow of pressurised air at a second pressure, higher than the first pressure, is sent to the sump reboiler of the column of pure oxygen,
    viii) nitrogen-enriched gas is taken at the top of the medium-pressure column, it is sent to the intermediate reboiler of the low-pressure column and the condensed gas is sent to the top of the medium-pressure column, and
    ix) gas rich in nitrogen or air is sent to the sump reboiler of the low-pressure column and the liquid which is condensed therein is sent to the medium-pressure column characterised in that liquid is taken from the sump of the column of pure oxygen as product, and air pressurised at the second pressure is sent to the vaporiser to vaporise the first flow of oxygen-enriched liquid, and the first flow of oxygen-enriched liquid is less rich in oxygen than the second flow of oxygen-enriched liquid.
  2. Method according to claim 1, wherein the first flow of oxygen-enriched liquid is pressurised upstream of the vaporiser (51).
  3. Method according to claim 1 or 2, wherein the first flow of oxygen-enriched liquid is partially vaporised in the vaporiser (51), the liquid formed constituting the second flow of oxygen-enriched liquid.
  4. Method according to claim 3, wherein the flow of air pressurised at the second pressure firstly heats the sump reboiler (61) of the column of pure oxygen (49) and then the vaporiser (51).
  5. Method according to any one of the preceding claims, wherein cryogenic liquid (69) from an auxiliary source is sent to the double column.
  6. Apparatus for separating air by cryogenic distillation comprising a medium-pressure column (23) and a low-pressure column (25), thermally connected to each other, the low-pressure column comprising a sump reboiler (35) and an intermediate reboiler (37) and a column of pure oxygen (49), an exchange line (63), a vaporiser (51), means for sending gaseous air purified and then cooled at a first pressure of the exchange line to the medium-pressure column, means for sending an oxygen-enriched liquid and a nitrogen-enriched liquid from the medium-pressure column to the low-pressure column, means for taking nitrogen-enriched gas from the low-pressure column, means for taking oxygen-enriched liquid containing at most 97% mol. of oxygen in the sump of the low-pressure column, means for sending a first flow of oxygen-enriched liquid to the vaporiser, a pipe for sending the gaseous oxygen thus formed to the exchange line, means for sending a second flow of oxygen-enriched liquid to the top of the column of pure oxygen, having a sump reboiler (61), where it is purified to form a sump liquid containing at least 98% mol. of oxygen, a supercharger (13), a pipe for sending a flow of air (17) pressurised in the supercharger at a second pressure higher than the first pressure at the sump reboiler of the column of pure oxygen, pipes for taking nitrogen-enriched gas at the top of the medium-pressure column, to send it to the intermediate reboiler of the low-pressure column and to send the condensed gas to the top of the medium-pressure column and pipes to send a gas rich in nitrogen or air to the sump reboiler of the low-pressure column and to send the liquid which condenses therein to the medium-pressure column characterised in that it comprises a pipe for taking the sump liquid (71) from the column of pure oxygen as product, means for sending air (15) pressurised at the second pressure of the supercharger to the vaporiser, and a pipe for sending liquid (53) from the vaporiser (51) to the top of the column of pure oxygen (49).
  7. Apparatus according to claim 6 comprising: a pipe for sending liquid from the sump (65) of the low-pressure column (25) to the top of the column of pure oxygen (49).
  8. Apparatus according to claim 7, wherein the means for sending pressurised air from the supercharger (3) to the vaporiser (51) are connected to the sump reboiler (61) of the column of pure oxygen (49) such that air intended for the vaporiser passes through the sump reboiler of the column of pure oxygen.
  9. Apparatus according to claim 7, wherein the means for sending a second flow of oxygen-enriched liquid to the top of the column of pure oxygen are constituted by the pipe for sending liquid from the sump of the low-pressure column (65) to the top of the column of pure oxygen (49).
  10. Apparatus according to claim 6, 7 or 8 comprising means for separating air pressurised at the second pressure into two parts, the means for sending air pressurised at the second pressure of the supercharger (3) to the vaporiser (51) and the pipe for sending a flow of air pressurised at the second pressure to the sump reboiler (61) of the column of pure oxygen (49) being connected such that part of the pressurised air (17) is sent to the sump reboiler of the column of pure oxygen and another part of pressurised air (15) is sent to the vaporiser.
  11. Apparatus according to one of claims 6 to 10 comprising means (69) for sending cryogenic liquid to the low-pressure column from an external source.
EP12720248.9A 2011-04-08 2012-04-05 Method and device for separating air by cryogenic distillation Active EP2694898B1 (en)

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FR1153070A FR2973865B1 (en) 2011-04-08 2011-04-08 METHOD AND APPARATUS FOR AIR SEPARATION BY CRYOGENIC DISTILLATION
PCT/FR2012/050742 WO2012136939A2 (en) 2011-04-08 2012-04-05 Method and device for separating air by cryogenic distillation

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US11746013B2 (en) 2016-06-27 2023-09-05 Texas Tech University System Apparatus and method for separating liquid oxygen from liquified air
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CN112781321B (en) * 2020-12-31 2022-07-12 乔治洛德方法研究和开发液化空气有限公司 Air separation device with nitrogen liquefier and method

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FR2973865A1 (en) 2012-10-12
US9696087B2 (en) 2017-07-04
US20140053601A1 (en) 2014-02-27
FR2973865B1 (en) 2015-11-06
CA2830826A1 (en) 2012-10-11
CA2830826C (en) 2018-10-16
WO2012136939A2 (en) 2012-10-11
AU2012238460A1 (en) 2013-10-31
CN103842753A (en) 2014-06-04

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