WO2007068858A2 - Process for separating air by cryogenic distillation - Google Patents

Process for separating air by cryogenic distillation Download PDF

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Publication number
WO2007068858A2
WO2007068858A2 PCT/FR2006/051350 FR2006051350W WO2007068858A2 WO 2007068858 A2 WO2007068858 A2 WO 2007068858A2 FR 2006051350 W FR2006051350 W FR 2006051350W WO 2007068858 A2 WO2007068858 A2 WO 2007068858A2
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WO
WIPO (PCT)
Prior art keywords
oxygen
flow
air
column
pressure
Prior art date
Application number
PCT/FR2006/051350
Other languages
French (fr)
Other versions
WO2007068858A3 (en
Inventor
Olivier De Cayeux
Richard Dubettier-Grenier
Alain Guillard
Patrick Le Bot
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 BRPI0619924-0A priority Critical patent/BRPI0619924A2/en
Priority to KR1020087014219A priority patent/KR101341278B1/en
Priority to CN2006800473992A priority patent/CN101331374B/en
Publication of WO2007068858A2 publication Critical patent/WO2007068858A2/en
Publication of WO2007068858A3 publication Critical patent/WO2007068858A3/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
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04375—Details relating to the work expansion, e.g. process parameter etc.
    • F25J3/04393—Details relating to the work expansion, e.g. process parameter etc. using multiple or multistage gas work expansion
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B13/00—Oxygen; Ozone; Oxides or hydroxides in general
    • C01B13/02—Preparation of oxygen
    • C01B13/0229—Purification or separation processes
    • C01B13/0248—Physical processing only
    • 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
    • F25J3/04054—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 air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04006—Providing pressurised feed air or process streams within or from the air fractionation unit
    • F25J3/04078—Providing pressurised feed air or process streams within or from the air fractionation unit providing pressurized products by liquid compression and vaporisation with cold recovery, i.e. so-called internal compression
    • F25J3/0409—Providing pressurised feed air or process streams within or from the air fractionation unit providing pressurized products by liquid compression and vaporisation with cold recovery, i.e. so-called internal compression of oxygen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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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
    • F25J3/04163—Hot end purification of the feed air
    • F25J3/04169—Hot end purification of the feed air by adsorption of the impurities
    • F25J3/04175—Hot end purification of the feed air by adsorption of the impurities at a pressure of substantially more than the highest pressure column
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
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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
    • F25J3/04284—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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04284—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams
    • F25J3/0429—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams of feed air, e.g. used as waste or product air or expanded into an auxiliary column
    • F25J3/04296—Claude expansion, i.e. expanded into the main or high pressure column
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04248—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
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    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04375—Details relating to the work expansion, e.g. process parameter etc.
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04406—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using a dual pressure main column system
    • F25J3/04412—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using a dual pressure main column system in a classical double column flowsheet, i.e. with thermal coupling by a main reboiler-condenser in the bottom of low pressure respectively top of high pressure column
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/0446—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using the heat generated by mixing two different phases
    • F25J3/04466—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using the heat generated by mixing two different phases for producing oxygen as a mixing column overhead gas by mixing gaseous air feed and liquid 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
    • F25J3/04763—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
    • F25J3/04812—Different modes, i.e. "runs" of operation
    • 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
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    • F25J3/04824—Stopping of the process, e.g. defrosting or deriming; Back-up procedures
    • 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
    • F25J3/04763—Start-up or control of the process; Details of the apparatus used
    • F25J3/04866—Construction and layout of air fractionation equipments, e.g. valves, machines
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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
    • F25J3/04763—Start-up or control of the process; Details of the apparatus used
    • F25J3/04866—Construction and layout of air fractionation equipments, e.g. valves, machines
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    • F25J3/04957—Arrangements of multiple air fractionation units or multiple equipments fulfilling the same process step, e.g. multiple trains in a network and inter-connecting equipments upstream of the fractionation unit (s), i.e. at the "front-end"
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2210/00—Purification or separation of specific gases
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    • C01B2210/0046—Nitrogen
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2210/00—Purification or separation of specific gases
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    • C01B2210/0051—Carbon dioxide
    • C—CHEMISTRY; METALLURGY
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    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2210/00—Purification or separation of specific gases
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    • C01B2210/0062—Water
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2210/00—Purification or separation of specific gases
    • C01B2210/0043—Impurity removed
    • C01B2210/0078—Noble gases
    • C01B2210/0082—Argon
    • 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
    • F25J2200/04—Processes or apparatus using separation by rectification in a dual pressure main column system
    • F25J2200/06—Processes or apparatus using separation by rectification in a dual pressure main column system in a classical double column flow-sheet, 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
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/90—Details relating to column internals, e.g. structured packing, gas or liquid distribution
    • F25J2200/94—Details relating to the withdrawal point
    • 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
    • F25J2215/52—Oxygen production with multiple 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
    • 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
    • F25J2215/54—Oxygen production with multiple pressure 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
    • F25J2230/00—Processes or apparatus involving steps for increasing the pressure of gaseous process streams
    • F25J2230/24—Multiple compressors or compressor stages in parallel
    • 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
    • F25J2230/00—Processes or apparatus involving steps for increasing the pressure of gaseous process streams
    • F25J2230/40—Processes or apparatus involving steps for increasing the pressure of gaseous process streams the 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
    • F25J2240/00—Processes or apparatus involving steps for expanding of process streams
    • F25J2240/02—Expansion of a process fluid in a work-extracting turbine (i.e. isentropic expansion), e.g. of the feed stream
    • F25J2240/04—Multiple expansion turbines in parallel
    • 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
    • F25J2240/00—Processes or apparatus involving steps for expanding of process streams
    • F25J2240/40—Expansion without extracting work, i.e. isenthalpic throttling, e.g. JT valve, regulating valve or venturi, or isentropic nozzle, e.g. Laval
    • F25J2240/42—Expansion without extracting work, i.e. isenthalpic throttling, e.g. JT valve, regulating valve or venturi, or isentropic nozzle, e.g. Laval the 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
    • 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

Definitions

  • the present invention relates to a process for air separation by cryogenic distillation, in particular to a method and installation for supplying oxygen at two pressures and / or two purities.
  • a steel production unit typically comprises several elements with different oxygen requirements, as described in "The Making, Shaping and Treating of Steel", AISE, 1985.
  • the blast furnace consumes air enriched with oxygen, usually produced by mixing compressed air with medium pressure oxygen (P ⁇ 10 bar) and in some cases low purity.
  • the low purity oxygen has a purity of between 80 and 97%.
  • Converters and arc furnaces consume oxygen at high pressure (P> 15 bar for injection into a converter, and P> 25 bar typically in the gas buffer capacities installed upstream of the converters) with a high purity of between 99 and 99.8%.
  • high pressure P> 15 bar for injection into a converter, and P> 25 bar typically in the gas buffer capacities installed upstream of the converters
  • P> 15 bar for injection into a converter
  • P> 25 bar typically in the gas buffer capacities installed upstream of the converters
  • high purity of between 99 and 99.8% a high purity of between 99 and 99.8%.
  • it is often provided two devices for producing oxygen by air distillation the one that produces the medium pressure oxygen being for example a mixing column apparatus of the type described in US-A. 4022030 and EP-A-0531 182 and the one producing the high purity oxygen typically being a conventional double column apparatus. All the purities mentioned are molar percentages and the pressures are absolute pressures.
  • the present invention aims to solve the following problem: sometimes the customer has increased needs for high pressure oxygen while he no longer needs medium pressure oxygen (or no longer needs as much oxygen) medium pressure / or can operate with a reduced (or even zero) amount of medium pressure oxygen [as is the case for the blast furnace]).
  • the object of the invention is to satisfy the customer without resorting to either a second air separation apparatus or to the vaporization of cryogenic liquid oxygen from storage.
  • a method for separating air by cryogenic distillation in an air separation apparatus comprising a column system in which i) according to a first step a) is compressed in a main compressor all the air intended for distillation b) a first compressed air flow is sent at least in the main compressor, purified and cooled in an exchange line to the medium pressure column of a double column c) separating the air flow in flows enriched in nitrogen and oxygen in the medium pressure column d) the nitrogen and oxygen enriched streams of the medium pressure column are sent to a low pressure column of the double column, directly or indirectly e) a flow rich in nitrogen is withdrawn from the low pressure column and is heated in the exchange line f) a liquid oxygen flow rate is withdrawn from the low pressure column, pressurized to a high pressure e and vaporized in the exchange line to form a first gaseous flow rich in oxygen and at high pressure g) liquefies at least a portion of the compressed air in the main compressor, optionally after recompress
  • the second gaseous flow rich in oxygen is produced by withdrawing a liquid flow from the low pressure column and pressurizing it at the lower pressure before vaporizing it in the exchange line;
  • the second gas flow rich in oxygen is produced by withdrawing a gas flow from a mixing column supplied with air or the low pressure column; the at least one second compressor compresses all the air intended for the apparatus;
  • the at least one second compressor compresses only a portion of the air intended for the apparatus
  • a portion of the compressed air in the second compressor is expanded in a turbine coupled to the second compressor and sent to the double column and in which the flow expanded during the second step reduced compared to that during the first step; during the second step, the flow rate sent to the second compressor with respect to the same flow rate during the first step is kept constant;
  • the first flow rich in oxygen has a purity higher than 98.5%, and the second flow rich in oxygen has a purity lower than 98%; -
  • the first step is withdrawn from the double column as a final product oxygen-rich liquid flow and in the second step the withdrawal of this flow is reduced, possibly to zero;
  • the sum of the first and second oxygen-rich flow rates is substantially constant between the first and second steps;
  • a flow of air is expanded in a turbine and sent to the double column and during the second step is the expanded flow is rejected to the atmosphere or a part of the expanded flow is sent to the double column while the rest is rejected to the atmosphere; during the second step, compressed air is sent to the double column coming from a backup compressor;
  • the first and second oxygen-rich flow rates have the same purity or different purities.
  • a method for supplying a high pressure oxygen flow rate wherein in a first step each of two air separation plants supplies high pressure oxygen and according to a second step, a first of the two facilities provides an increased high pressure oxygen flow compared to that in the first step and the second installation provides a reduced flow, or even zero; at least the first plant operating as described above and providing in addition to its initial production of high pressure oxygen at least 50% of the amount of high pressure oxygen produced during the first step by the second installation.
  • an air compressor of the second installation sends compressed air to the first installation during the second step
  • FIG. 1 A schematic diagram of a typical air separation apparatus.
  • FIG. 1 A schematic diagram of a typical air separation apparatus.
  • FIG. 1 A schematic diagram of a typical air separation apparatus.
  • FIG. 1 A schematic diagram of a typical air separation apparatus.
  • FIG. 1 A schematic diagram of a typical air separation apparatus.
  • FIG. 1 A schematic diagram of a typical air separation apparatus.
  • FIG. 1 A schematic diagram of a typical air separation apparatus.
  • FIG. 1 The air distillation plant shown in FIG.
  • an air compressor 1 essentially comprises: an air compressor 1, an apparatus 2 for cleaning compressed air with water and adsorption CO 2 , this apparatus comprising two bottles of adsorption 2A, 2B, one of which operates in adsorption while the other is being regenerated, a turbine-booster assembly 3 comprising an expansion turbine 4, and optionally a booster 5 whose shaft is coupled to that of the turbine 4, a heat exchanger 6 constituting the heat exchange line of the installation, a double distillation column 7 comprising a medium pressure column 8 surmounted by a low pressure column 9, with a vaporizer-condenser 10 setting the steam head (nitrogen) of the column 8 in heat exchange relation with the tank liquid (oxygen) of the column 9, a liquid oxygen tank 11 whose bottom is connected to a liquid oxygen pump 12, and a reservoir of liquid nitrogen 13 whose bottom is connected to a liquid nitrogen pump 14.
  • This installation is intended to supply, via a pipe 15, gaseous oxygen under a predetermined high pressure, which may be between a few bars and a few tens of bars (in this specification, the pressures considered are absolute pressures).
  • liquid oxygen withdrawn from the tank of the column 9 via a pipe 16 and stored in the tank 11, is brought to the high pressure by the pump 12 in the liquid state, then vaporized and heated under this high pressure in passages 17 of the exchanger 8.
  • the heat required for this vaporization and reheating, as well as the reheating and possibly the vaporization of other fluids withdrawn from the double column, is provided by the air to be distilled under the following conditions.
  • All of the air to be distilled is compressed by the compressor 1 at a pressure higher than the average pressure of the column 8 but lower than the high pressure of oxygen. Then the air, pre-cooled at 18 and cooled to near room temperature at 19, is purified in one, 2A for example, adsorption bottles, and supercharged entirely at high pressure by the booster 5, which is driven by the turbine 4.
  • the air is then introduced to the hot end of the exchanger 6 and completely cooled to an intermediate temperature. At this temperature, a fraction of the air continues cooling and is liquefied in passages 20 of the exchanger, then is expanded at low pressure in an expansion valve 21 and introduced at an intermediate level in column 9. The the remainder of the air, or excess air, is expanded at the medium pressure in the turbine 4 and then sent directly, via a pipe 22, to the base of the column 8.
  • the low pressure nitrogen is heated in passages 28 of the exchanger 6 and then discharged via a line 29, while the residual gas, after heating in passages 30 of the exchanger, is used to regenerate an adsorption bottle, the bottle 2B in the example under consideration, before being discharged via a pipe 31.
  • a part of liquid oxygen 36 withdrawn at an intermediate level of the low pressure column is, after expansion in an expansion valve 32, stored in the reservoir 13 and pressurized by the pumped 14 and a liquid oxygen production is provided via a pipe 33 (medium purity) and / or 34 (high purity).
  • Part of the medium purity liquid oxygen is vaporized after pressurization in the pump 14 in the heat exchanger 6.
  • the pump 14 has a lower outlet pressure than the pump 12.
  • the valve 32 is closed and no more medium pressure oxygen is withdrawn or the medium pressure oxygen flow is reduced.
  • the withdrawal of the flow rate 16 is increased and more high purity oxygen and high pressure are pumped from the pump 12 into the exchanger 6.
  • the outlet pressure of the compressor 1 is increased. as well as the flow rate of compressed air by adjusting the blades of the compressor 1. If there is no production of liquid oxygen, the sum of the flow rates 16 and 36 is constant, between the first and second steps because the flow of compressed air in the compressor 1 remains substantially constant between the two steps.
  • the sum of the flow rates 16 and 36 is constant between the first and second steps, or a greater sum can be produced during the second step by reducing or even suppressing the production of liquid oxygen. If the production of liquid is reduced, a part of the air coming from the Claude 4 turbine will be sent to the atmosphere after being mixed with the waste gas 27.
  • the installation represented in FIG. 2 is intended to produce oxygen. gaseous at two pressures and two purities.
  • the double column is constituted, in a conventional manner, a medium pressure column 50 operating at about 6 bar and surmounted by a low pressure column 51 operating slightly above atmospheric pressure with, in the tank of the latter, a vaporizer-condenser 52 which puts in heat exchange relation the liquid oxygen of the tank of the low pressure column with the head nitrogen of the medium pressure column.
  • the air compressor 44 of the installation directly compresses all the air at the first high pressure of the order of 23 bar, and a first stream of this air is treated as previously in the passages 53, the turbine 46 and the expansion valve 54 then sent to the base of the column 50.
  • blower a single-wheel compressor whose energy expenditure, by the flow of gas treated and the compression ratio, is considerably lower than that of the main compressor 44 of the installation , and for example of the order of 2 to 3% of the latter.
  • the compression ratio of such a blower is generally less than 2.
  • Each of the blowers in question here comprises at its output a water or atmospheric refrigerant not shown.
  • the liquid oxygen withdrawn from the bottom of the column 51 is fed by the pump 49 to the high pressure, then vaporized and reheated in passages 58 of the exchange line before being evacuated from the installation via a production line. 59 as a flow of high pressure, high purity oxygen gas.
  • the liquid oxygen withdrawn at an intermediate level of the column 51 is fed by the pump 70 at medium pressure, then vaporized and reheated in passages 58 of the exchange line before being evacuated from the installation via a pipe as the flow rate of gaseous oxygen medium pressure and medium purity. Furthermore, in the installation of FIG.
  • the second step either no more medium pressure oxygen is withdrawn or the medium pressure oxygen flow is reduced.
  • the withdrawal of the flow of liquid oxygen in the vat of the low pressure column is increased and more high purity oxygen and high pressure are pumped from the pump 49 into the exchanger 6.
  • the output pressure of the compressor 1 and the compressed air flow are increased by adjusting the blades of the compressor 1.
  • the air flow is regulated by means of the blowers 70, 71.
  • the sum of the flow rates 59 and 72 is constant, between the first and second steps.
  • the compressed flow rate increases during the second step, the sum of the gaseous oxygen products may increase. Reducing or even suppressing the production of liquid oxygen also allows more variation in gaseous productions. If the liquid production is reduced, at least a portion of the air from at least one of the turbines 46, 72 will be sent to the atmosphere after being mixed with the waste gas 66 during the second step.
  • a flow of air at atmospheric pressure is compressed to about 15 bar in a main compressor 1.
  • the air is then optionally cooled, before being purified to remove impurities (not shown).
  • the clean air is divided in two.
  • Part of the air 3 is sent to a booster 5 where it is compressed to a pressure of between 17 and 20 bar and then the supercharged air is cooled by a water cooler 7 before being sent to the hot end of the main exchange line 9 of the air separation apparatus.
  • the pressurized air 11 cools to an intermediate temperature before exiting the exchange line and being divided into two fractions. It is obviously possible for a fraction of the flow 11 to continue cooling down to the cold end of the exchange line 9 from which it will exit liquefied.
  • a fraction 13 is sent into a turbine 17 and the remainder, a fraction 15 is sent into a turbine 19.
  • the two turbines have the same temperature and suction pressure and the same temperature and outlet pressure but it is obviously possible that these temperatures and pressure are close to each other instead of being identical.
  • the two turbine flows are mixed to form an air flow 21 of which a portion 121 is sent to the double column and the remainder 122 to the mixing column 300.
  • the flow 122 constitutes a part of the flow 21 or possibly a fraction of the gas part of the flow 21 in the case where it would be two-phase. It is obviously possible to send all the flow 21 to the medium pressure column 100 and to leave a gaseous part 122 for sending to the mixing column, the medium pressure column replacing in this case the phase separator.
  • the pressures of the medium pressure column and the mixing column may be different.
  • the turbine 19 may be an insufflation turbine opening to the pressure of the low pressure column.
  • Another part 2 of the air at 15 bars constituting the rest of the air is cooled in the exchange line at an intermediate temperature higher than the suction temperature of the turbines 17, 19, compressed in a second booster 23 until at about 30 bar and reintroduced into the exchange line 9 at a higher temperature to continue cooling.
  • the air 37 to 30 bars approximately liquefies in the exchange line and the liquid oxygen 25 vaporizes in the exchange line, the vaporization temperature of the liquid being close to the suction temperature of the second blower 23.
  • the liquefied air leaves the exchange line and is sent to the column system.
  • the first booster 5 is coupled with one of the turbines 17, 19 and the second booster 23 is coupled with the other of the turbines 19, 17.
  • the column system of an air separation apparatus is constituted by a medium pressure column 100 thermally connected with a low pressure column 200 to minaret, a mixing column 300 and an optional argon column (not shown).
  • the low pressure column does not necessarily have a minaret.
  • the medium pressure column operates at a pressure of 5.5 bar but can operate at a higher pressure.
  • the air 121 coming from the two turbines 17, 19 is the flow rate delivered to the bottom of the medium pressure column 100.
  • the liquefied air 37 is expanded in the valve 39 or possibly in a turbine and sent to the column system.
  • Rich liquid 51, lower lean liquid 53 and upper lean liquid 55 are sent from the medium pressure column 100 to the low pressure column 200 after expansion stages in valves and subcooling.
  • Liquid oxygen is pressurized by the pump 500 and sent as a pressurized liquid to the exchange line 9.
  • Part of the liquid 501 can be stored as a liquid product.
  • Other liquids, pressurized or not, can vaporize in the exchange line.
  • Nitrogen gas is optionally withdrawn from the medium pressure column and is also cooled in the exchange line 9.
  • Nitrogen 33 is withdrawn at the top of the low pressure column and heats up in the exchange line, after having served to sub-cool the reflux liquids.
  • Residual nitrogen 27 is withdrawn from a lower level of the low pressure column and warms in the exchange line 9, after having been used to sub-cool the reflux liquids.
  • the column can possibly produce argon by treating a flow
  • the flow 52 is the tank liquid returned from the argon column, if there is one.
  • the mixing column 300 is fed at the top with an oxygen rich liquid withdrawn at an intermediate level of the low pressure column 200. pressurized by the pump 600 and in the tank by a flow of gaseous air 122 from the turbines 17, 19.
  • the mixing column operates essentially at medium pressure.
  • a flow of oxygen gas 137 is withdrawn at the top of the mixing column and then warms in the exchange line 9 and a liquid flow 41 is withdrawn in the tank and sent to the low pressure column after expansion in a valve. It is possible to withdraw an intermediate flow from the column 300 which is sent to the low pressure column.
  • the second step differs from the first in that the oxygen production of the mixing column is reduced or suppressed.
  • the withdrawal of the flow of liquid oxygen in the tank from the low pressure column is increased and more high purity and high pressure oxygen from the pump 600 is vaporized in the exchanger 9 to form the flow 125.
  • the outlet pressure of the compressor 1 and the compressed air flow rate are increased by adjusting the blades of the compressor 1.
  • the air flow and its pressure are regulated by means of the booster 23.
  • the air pressure 37 can be changed for the second step by changing the blades of the compressor 1 and / or those of the cold booster 23.
  • the mixing column does not produce oxygen
  • the surplus of the air is sent to the double column.
  • the booster 23 compresses the air 2 to a higher pressure, which makes it possible to vaporize more liquid oxygen by increasing the tank withdrawal from the low pressure column to pressurize a larger flow rate in the pump 500.
  • the only rich gas in oxygen product is oxygen medium pressure and medium purity.
  • the second step is sent less air 122 in the tank of the mixing column. This receives less liquid oxygen and its operation is reduced. The surplus of the air is sent to the double column.
  • the booster 23 compresses the air 2 to a higher pressure, which makes it possible to vaporize more liquid oxygen by increasing the tank extraction. of the low pressure column to pressurize a larger flow rate in the pump 500.
  • the apparatus produces more medium pressure and medium purity oxygen than with the first step but continues to produce a reduced amount of low purity, low pressure oxygen.
  • the sum of the flow rates 125 and 137 is constant, between the first and second steps.
  • the compressed flow rate increases during the second step, the sum of the gaseous oxygen products may increase.
  • the reduction or even the suppression of the liquid oxygen production 501 also allows more variation in the gaseous productions. If the liquid production is reduced, at least a portion of the air from at least one of the turbines 17, 19 will be sent to the atmosphere after being mixed with the waste gas 27 during the second step.
  • the booster is driven by an air turbine but it will be easily understood that the booster could be driven by a nitrogen turbine, a steam turbine or other turbine present on the site.
  • the invention makes it possible to solve the problem when two air separation devices produce high pressure oxygen. If one of the devices produces more or produces less, the other can increase the production of high pressure oxygen at the cost of producing oxygen medium pressure operating according to the invention.
  • the additional air required can be supplied to the other apparatus from an air compressor or an air booster of the apparatus in stationary or reduced operation.
  • the invention allows the other apparatus to provide up to 50% of the product previously from the device in stop or reduced walking. It is obviously possible to produce the two oxygen pressures during the first and possibly the second step by pumping a single flow of oxygen into a pump and by relaxing a portion. In this case, the flows will obviously have the same purity.
  • the apparatus can also produce nitrogen and / or argon under pressure by spraying pumped nitrogen and argon (s). It is also possible to reduce or stop the production of nitrogen and / or argon under pressure during the second step compared to the production during the first step.
  • the device can also produce liquid nitrogen as the final product during the first step. In this case, it is conceivable to reduce or stop the production of liquid during the second step.
  • FIG 4 shows two air separation units ASU 1 and ASU 2, at least the first ASU 1 works according to the invention. Both devices are supplied with air by their respective compressors C1, C2. If the ASU 2 reduces its production of high purity oxygen 15, the ASU 1 begins to operate on the second step to produce more high pressure oxygen 15. To assist, purified or unpurified air can be sent from the compressor C2 to the ASU 1.

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Abstract

According to a first step in an air separation unit, all the air intended for distillation is compressed in a main compressor (1), a first stream of air, compressed in at least the main compressor, purified and cooled in a heat exchange line (6), is sent to the medium-pressure column (8) of a double column, said stream of air is divided into a nitrogen-enriched stream and an oxygen-enriched stream in the medium-pressure column, a liquid oxygen stream (16) is withdrawn from the low-pressure column, said stream is pressurized up to a high pressure and vaporized in the heat exchange line in order to form a first high-pressure oxygen-rich gas stream, at least one portion (24) of the air compressed in the main compressor is liquefied and the liquefied portion is sent to the double column, and a second oxygen-rich gas stream (115) is also produced, but at a lower pressure than the first oxygen-rich gas stream, and, in a second step, the air liquefaction pressure is increased by adjusting the blades of the main compressor (1), which set this pressure, the production of the second oxygen-rich gas stream is reduced, and the withdrawal of the first oxygen-rich gas stream is increased.

Description

Procédé de séparation d'air par distillation cryogénique Process for the separation of air by cryogenic distillation
La présente invention est relative à un procédé de séparation d'air par distillation cryogénique, en particulier à un procédé et installation de fourniture d'oxygène à deux pressions et/ou a deux puretés.The present invention relates to a process for air separation by cryogenic distillation, in particular to a method and installation for supplying oxygen at two pressures and / or two purities.
Certains contextes industriels nécessitent la fourniture simultanée, en grandes quantités, d'oxygène à une seule pureté sous des pressions différentes, voire d'oxygène pratiquement pur et d'oxygène impur sous des pressions différentes. Par ailleurs, certaines applications industrielles nécessitent des quantités importantes d'oxygène impur sous diverses pressions : gazéification du charbon, gazéification de résidus pétroliers, réduction-fusion directe du minerai de fer, injection de charbon dans les hauts fourneaux, métallurgie des métaux non-ferreux, etc. Une unité de production sidérurgique comprend classiquement plusieurs éléments ayant des besoins différents en oxygène, tel que décrit dans « The Making, Shaping and Treating of Steel », AISE, 1985. Le haut fourneau consomme de l'air enrichi en oxygène, produit en général en mélangeant de l'air comprimé avec de l'oxygène moyenne pression (P<10 bar)et dans certains cas basse pureté. L'oxygène basse pureté a une pureté d'entre 80 et 97 %. Par contre les convertisseurs et les fours à arc consomment de l'oxygène à haute pression (P>15 bar pour injection dans convertisseur, et P>25 bar typiquement dans les capacités tampons gaz installé en amont des convertisseurs) avec une haute pureté d'entre 99 et 99,8 %. Pour fournir ces deux qualités d'oxygène, il est souvent prévu deux appareils de production d'oxygène par distillation d'air, celui qui produit l'oxygène moyenne pression étant par exemple un appareil à colonne de mélange du type décrit dans US-A-4022030 et EP-A-0531 182 et celui qui produit l'oxygène haute pureté étant typiquement un appareil à double colonne classique. Toutes les puretés mentionnées sont des pourcentages molaires et les pressions sont des pressions absolues.Certain industrial contexts require the simultaneous supply, in large quantities, of oxygen with a single purity under different pressures, or even of practically pure oxygen and impure oxygen under different pressures. In addition, certain industrial applications require large amounts of impure oxygen under various pressures: coal gasification, gasification of petroleum residues, direct reduction-iron ore smelting, coal injection in blast furnaces, metallurgy of non-ferrous metals etc. A steel production unit typically comprises several elements with different oxygen requirements, as described in "The Making, Shaping and Treating of Steel", AISE, 1985. The blast furnace consumes air enriched with oxygen, usually produced by mixing compressed air with medium pressure oxygen (P <10 bar) and in some cases low purity. The low purity oxygen has a purity of between 80 and 97%. Converters and arc furnaces, on the other hand, consume oxygen at high pressure (P> 15 bar for injection into a converter, and P> 25 bar typically in the gas buffer capacities installed upstream of the converters) with a high purity of between 99 and 99.8%. To provide these two qualities of oxygen, it is often provided two devices for producing oxygen by air distillation, the one that produces the medium pressure oxygen being for example a mixing column apparatus of the type described in US-A. 4022030 and EP-A-0531 182 and the one producing the high purity oxygen typically being a conventional double column apparatus. All the purities mentioned are molar percentages and the pressures are absolute pressures.
La présente invention vise à résoudre le problème suivant : parfois le client a des besoins augmentés en oxygène haute pression alors qu'il n'a plus besoin d'oxygène moyenne pression (ou n'a plus besoin d'autant d'oxygène moyenne pression / ou peut fonctionner avec une quantité réduite (voire nulle) d'oxygène moyenne pression [comme c'est le cas pour le haut fourneau]). Le but de l'invention est de satisfaire le client sans avoir recours ni à un deuxième appareil de séparation d'air, ni à la vaporisation d'oxygène liquide cryogénique venant d'un stockage.The present invention aims to solve the following problem: sometimes the customer has increased needs for high pressure oxygen while he no longer needs medium pressure oxygen (or no longer needs as much oxygen) medium pressure / or can operate with a reduced (or even zero) amount of medium pressure oxygen [as is the case for the blast furnace]). The object of the invention is to satisfy the customer without resorting to either a second air separation apparatus or to the vaporization of cryogenic liquid oxygen from storage.
Selon un objet de l'invention, il est prévu un procédé de séparation d'air par distillation cryogénique dans un appareil de séparation d'air comprenant un système de colonnes dans lequel i) selon une première marche a) on comprime dans un compresseur principal tout l'air destiné à la distillation b) on envoie un premier débit d'air comprimé au moins dans le compresseur principal, épuré et refroidi dans une ligne d'échange à la colonne moyenne pression d'une double colonne c) on sépare le débit d'air en des flux enrichis en azote et en oxygène dans la colonne moyenne pression d) on envoie les flux enrichis en azote et en oxygène de la colonne moyenne pression à une colonne basse pression de la double colonne, directement ou indirectement e) on soutire un débit riche en azote de la colonne basse pression et on les réchauffe dans la ligne d'échange f) on soutire un débit d'oxygène liquide de la colonne basse pression, on le pressurise jusqu'à une pression élevée et on le vaporise dans la ligne d'échange pour former un premier débit gazeux riche en oxygène et à pression élevée g) on liquéfie au moins une partie de l'air comprimé dans le compresseur principal, éventuellement après l'avoir recomprimée dans au moins un deuxième compresseur, et on envoie la partie liquéfiée à la double colonne et h) on produit également un deuxième débit gazeux riche en oxygène mais à une pression moins élevée que le premier débit gazeux riche en oxygène ii) selon une deuxième marche a) on augmente la pression de liquéfaction de l'air dans en réglant les aubages du compresseur principal et éventuellement du deuxième compresseur qui fixe(nt) cette pression b) on réduit, éventuellement à zéro, la production du deuxième débit gazeux riche en oxygène c) on augmente le soutirage du premier débit gazeux riche en oxygèneAccording to one object of the invention, there is provided a method for separating air by cryogenic distillation in an air separation apparatus comprising a column system in which i) according to a first step a) is compressed in a main compressor all the air intended for distillation b) a first compressed air flow is sent at least in the main compressor, purified and cooled in an exchange line to the medium pressure column of a double column c) separating the air flow in flows enriched in nitrogen and oxygen in the medium pressure column d) the nitrogen and oxygen enriched streams of the medium pressure column are sent to a low pressure column of the double column, directly or indirectly e) a flow rich in nitrogen is withdrawn from the low pressure column and is heated in the exchange line f) a liquid oxygen flow rate is withdrawn from the low pressure column, pressurized to a high pressure e and vaporized in the exchange line to form a first gaseous flow rich in oxygen and at high pressure g) liquefies at least a portion of the compressed air in the main compressor, optionally after recompressing it in at minus a second compressor, and the liquefied part is sent to the double column and h) a second gaseous flow rich in oxygen is also produced but at a lower pressure than the first gaseous flow rich in oxygen ii) according to a second step a) increasing the liquefaction pressure of the air by adjusting the blades of the main compressor and possibly the second compressor which sets (s) this pressure b) is reduced, possibly to zero, the production of the second gas flow rich in oxygen c) increasing the withdrawal of the first gas flow rich in oxygen
Selon d'autres aspects facultatifs :According to other optional aspects:
- le deuxième débit gazeux riche en oxygène est produit en soutirant un débit liquide de la colonne basse pression et en le pressurisant à la pression moins élevée avant de le vaporiser dans la ligne d'échange ;the second gaseous flow rich in oxygen is produced by withdrawing a liquid flow from the low pressure column and pressurizing it at the lower pressure before vaporizing it in the exchange line;
- le deuxième débit gazeux riche en oxygène est produit en soutirant un débit gazeux d'une colonne de mélange alimentée par de l'air ou de la colonne basse pression ; - l'au moins un deuxième compresseur comprime(nt) tout l'air destiné à l'appareil ;the second gas flow rich in oxygen is produced by withdrawing a gas flow from a mixing column supplied with air or the low pressure column; the at least one second compressor compresses all the air intended for the apparatus;
- l'au moins un deuxième compresseur ne comprime qu'une partie de l'air destiné à l'appareil ;the at least one second compressor compresses only a portion of the air intended for the apparatus;
- lors de la deuxième marche on augmente le débit envoyé au deuxième compresseur ;during the second step, the flow rate sent to the second compressor is increased;
- une partie de l'air comprimé dans le deuxième compresseur est détendue dans une turbine couplée au deuxième compresseur puis envoyé à la double colonne et dans lequel le débit détendu pendant la deuxième marche réduit par rapport à celui pendant la première marche ; - lors de la deuxième marche on maintient constant le débit envoyé au deuxième compresseur par rapport au même débit pendant la première marche ;- A portion of the compressed air in the second compressor is expanded in a turbine coupled to the second compressor and sent to the double column and in which the flow expanded during the second step reduced compared to that during the first step; during the second step, the flow rate sent to the second compressor with respect to the same flow rate during the first step is kept constant;
- on augmente la quantité de gaz envoyée une turbine entraînant le deuxième compresseur dans la deuxième marche par rapport à celle envoyée pendant la première marche ;increasing the quantity of gas sent to a turbine driving the second compressor in the second step relative to that sent during the first step;
- le premier débit riche en oxygène a une pureté supérieure à 98.5%, et le deuxième débit riche en oxygène a une pureté inférieure à 98% ; - lors de la première marche on soutire de la double colonne en tant que produit final un débit liquide riche en oxygène et lors de la deuxième marche le soutirage de ce débit est réduit, éventuellement à zéro ;the first flow rich in oxygen has a purity higher than 98.5%, and the second flow rich in oxygen has a purity lower than 98%; - During the first step is withdrawn from the double column as a final product oxygen-rich liquid flow and in the second step the withdrawal of this flow is reduced, possibly to zero;
- la somme des premier et deuxième débits riches en oxygène est substantiellement constante entre la première et la deuxième marches ;the sum of the first and second oxygen-rich flow rates is substantially constant between the first and second steps;
- pendant la première marche un débit d'air est détendu dans une turbine et envoyé à la double colonne et pendant la deuxième marche soit le débit détendu est rejeté à l'atmosphère soit une partie du débit détendu est envoyée à la double colonne alors que le reste est rejeté à l'atmosphère ; - pendant la deuxième marche on envoie de l'air comprimé à la double colonne provenant d'un compresseur de secours ;- during the first step a flow of air is expanded in a turbine and sent to the double column and during the second step is the expanded flow is rejected to the atmosphere or a part of the expanded flow is sent to the double column while the rest is rejected to the atmosphere; during the second step, compressed air is sent to the double column coming from a backup compressor;
- une partie de l'air traité vient d'une soufflante de haut fourneau ;- part of the treated air comes from a blower blast furnace;
- pendant la première marche on produit un débit d'azote sous pression et/ou d'argon sous pression par vaporisation de liquide pressurisé et pendant la deuxième marche on réduit ou on arrête la production de ce(s) débit(s) ;during the first step, a flow of nitrogen under pressure and / or argon under pressure is produced by vaporization of pressurized liquid and during the second step the production of this flow (s) is reduced or stopped;
- pendant la première marche on produit un débit d'azote liquide et/ou d'argon liquide comme produit final et pendant la deuxième marche, on réduit ou on arrête cette (ces) production(s) ;during the first step, a flow of liquid nitrogen and / or liquid argon is produced as final product and during the second step, this (these) production (s) is reduced or stopped;
- les premier et deuxième débits riches en oxygène ont la même pureté ou des puretés différentes.the first and second oxygen-rich flow rates have the same purity or different purities.
Selon un autre aspect de l'invention, il est prévu un procédé de fourniture d'un débit d'oxygène haute pression dans lequel selon une première marche chacune de deux installations de séparation d'air fournit de l'oxygène haute pression et selon une deuxième marche, une première des deux installations fournit un débit d'oxygène haute pression augmenté par rapport à celui selon la première marche et la deuxième installation fournit un débit réduit, voire à zéro ; au moins la première installation fonctionnant comme décrit ci-dessus et fournissant en plus de sa production initiale d'oxygène haute pression au moins 50% de la quantité d'oxygène haute pression produite pendant la première marche par la deuxième installation.According to another aspect of the invention, there is provided a method for supplying a high pressure oxygen flow rate wherein in a first step each of two air separation plants supplies high pressure oxygen and according to a second step, a first of the two facilities provides an increased high pressure oxygen flow compared to that in the first step and the second installation provides a reduced flow, or even zero; at least the first plant operating as described above and providing in addition to its initial production of high pressure oxygen at least 50% of the amount of high pressure oxygen produced during the first step by the second installation.
Selon d'autres aspects de l'invention, il est prévu que :According to other aspects of the invention, it is provided that:
- un compresseur d'air de la deuxième installation envoie de l'air comprimé à la première installation pendant la deuxième marche- an air compressor of the second installation sends compressed air to the first installation during the second step
- aucun surpresseur d'air n'est entraîné par un moteur. Les Figures 1 , 2 et 3 représentent un appareil de séparation d'air capable de fonctionner selon le procédé de l'invention et la Figure 4 montre un ensemble d'appareils de séparation d'air dont au moins un qui fonctionne selon l'invention. L'installation de distillation d'air représentée à la Figure 1 comprend essentiellement : un compresseur d'air 1 , un appareil 2 d'épuration de l'air comprimé en eau et en CO2 par adsorption, cet appareil comprenant deux bouteilles d'adsorption 2A, 2B dont l'une fonctionne en adsorption pendant que l'autre est en cours de régénération, un ensemble turbine-surpresseur 3 comprenant une turbine de détente 4, et éventuellement un surpresseur 5 dont l'arbre est couplé à celui de la turbine 4, un échangeur de chaleur 6 constituant la ligne d'échange thermique de l'installation, une double colonne de distillation 7 comprenant une colonne moyenne pression 8 surmontée d'une colonne basse pression 9, avec un vaporiseur-condenseur 10 mettant la vapeur de tête (azote) de la colonne 8 en relation d'échange thermique avec le liquide de cuve (oxygène) de la colonne 9, un réservoir d'oxygène liquide 11 dont le fond est relié à une pompe d'oxygène liquide 12, et un réservoir d'azote liquide 13 dont le fond est relié à une pompe d'azote liquide 14.- No air booster is driven by a motor. Figures 1, 2 and 3 show an air separation apparatus capable of operating according to the method of the invention and Figure 4 shows a set of air separation apparatus of which at least one operating according to the invention . The air distillation plant shown in FIG. 1 essentially comprises: an air compressor 1, an apparatus 2 for cleaning compressed air with water and adsorption CO 2 , this apparatus comprising two bottles of adsorption 2A, 2B, one of which operates in adsorption while the other is being regenerated, a turbine-booster assembly 3 comprising an expansion turbine 4, and optionally a booster 5 whose shaft is coupled to that of the turbine 4, a heat exchanger 6 constituting the heat exchange line of the installation, a double distillation column 7 comprising a medium pressure column 8 surmounted by a low pressure column 9, with a vaporizer-condenser 10 setting the steam head (nitrogen) of the column 8 in heat exchange relation with the tank liquid (oxygen) of the column 9, a liquid oxygen tank 11 whose bottom is connected to a liquid oxygen pump 12, and a reservoir of liquid nitrogen 13 whose bottom is connected to a liquid nitrogen pump 14.
Cette installation est destinée à fournir, via une conduite 15, de l'oxygène gazeux sous une haute pression prédéterminée, qui peut être comprise entre quelques bars et quelques dizaines de bars (dans le présent mémoire, les pressions considérées sont de pressions absolues).This installation is intended to supply, via a pipe 15, gaseous oxygen under a predetermined high pressure, which may be between a few bars and a few tens of bars (in this specification, the pressures considered are absolute pressures).
Pour cela, de l'oxygène liquide soutiré de la cuve de la colonne 9 via une conduite 16 et stocké dans le réservoir 11 , est amené à la haute pression par la pompe 12 à l'état liquide, puis vaporisé et réchauffé sous cette haute pression dans des passages 17 de l'échangeur 8.For this, liquid oxygen withdrawn from the tank of the column 9 via a pipe 16 and stored in the tank 11, is brought to the high pressure by the pump 12 in the liquid state, then vaporized and heated under this high pressure in passages 17 of the exchanger 8.
La chaleur nécessaire à cette vaporisation et à ce réchauffage, ainsi qu'au réchauffage et éventuellement à la vaporisation d'autres fluides soutirés de la double colonne, est fournie par l'air à distiller, dans les conditions suivantes.The heat required for this vaporization and reheating, as well as the reheating and possibly the vaporization of other fluids withdrawn from the double column, is provided by the air to be distilled under the following conditions.
La totalité de l'air à distiller est comprimée par le compresseur 1 à une pression supérieure à la moyenne pression de la colonne 8 mais inférieure à la haute pression d'oxygène. Puis l'air, prérefroidi en 18 et refroidi au voisinage de la température ambiante en 19, est épuré dans l'une, 2A par exemple, des bouteilles d'adsorption, et surpressé en totalité à la haute pression par le surpresseur 5, lequel est entraîné par la turbine 4.All of the air to be distilled is compressed by the compressor 1 at a pressure higher than the average pressure of the column 8 but lower than the high pressure of oxygen. Then the air, pre-cooled at 18 and cooled to near room temperature at 19, is purified in one, 2A for example, adsorption bottles, and supercharged entirely at high pressure by the booster 5, which is driven by the turbine 4.
L'air est alors introduit au bout chaud de l'échangeur 6 et refroidi en totalité jusqu'à une température intermédiaire. A cette température, une fraction de l'air poursuit son refroidissement et est liquéfié dans des passages 20 de l'échangeur, puis est détendu à la basse pression dans une vanne de détente 21 et introduit à un niveau intermédiaire dans la colonne 9. Le reste de l'air, ou air excédentaire, est détendu à la moyenne pression dans la turbine 4 puis envoyé directement, via une conduite 22, à la base de la colonne 8. On reconnaît par ailleurs sur la Figure 1 les conduites habituelles des installations à double colonne, celle représentée étant du type dit « à minaret », c'est-à-dire avec production d'azote sous la basse pression : les conduites 23 à 25 d'injection dans la colonne 9, à des niveaux croissants, de « liquide riche » (air enrichi en oxygène) détendu, de « liquide pauvre inférieur » (azote impur) détendu et de « liquide pauvre supérieur » (azote pratiquement pur) détendu, respectivement, ces trois fluides étant respectivement soutirés à la base, en un point intermédiaire et au sommet de la colonne 8 ; et les conduites 28 de soutirage d'azote gazeux partant du sommet de la colonne 9 et 27 d'évacuation du gaz résiduaire (azote impur) partant du niveau d'injection du liquide pauvre inférieur. L'azote basse pression est réchauffé dans des passages 28 de l'échangeur 6 puis évacué via une conduite 29, tandis que le gaz résiduaire, après réchauffement dans des passages 30 de l'échangeur, est utilisé pour régénérer une bouteille d'adsorption, la bouteille 2B dans l'exemple considéré, avant d'être évacué via une conduite 31. On voit encore sur la Figure 1 qu'une partie d'oxygène liquide 36 soutiré à un niveau intermédiaire de la colonne basse pression est, après détente dans une vanne de détente 32, stockée dans le réservoir 13 et pressurisé par la pompé 14 et une production d'oxygène liquide est fournie via une conduite 33 (moyenne pureté) et/ou 34 (haute pureté). Une partie de l'oxygène liquide moyenne pureté est vaporisée après pressurisation dans la pompe 14 dans l'échangeur 6. La pompe 14 a une pression de sortie plus basse que la pompe 12. Ainsi selon la première marche, l'appareil produit un débit d'oxygène 15 à haute pureté et haute pression ainsi qu'un débit d'oxygène 1 15 à moyenne pureté et moyenne pression.The air is then introduced to the hot end of the exchanger 6 and completely cooled to an intermediate temperature. At this temperature, a fraction of the air continues cooling and is liquefied in passages 20 of the exchanger, then is expanded at low pressure in an expansion valve 21 and introduced at an intermediate level in column 9. The the remainder of the air, or excess air, is expanded at the medium pressure in the turbine 4 and then sent directly, via a pipe 22, to the base of the column 8. It is also recognized in Figure 1 the usual lines of the facilities with double column, the one represented being of the type called "minaret", that is to say with production of nitrogen under the low pressure: the lines 23 to 25 of injection in the column 9, at increasing levels, of "rich liquid" (oxygen enriched air) expanded, "lower poor liquid" (impure nitrogen) expanded and "upper poor liquid" (substantially pure nitrogen) expanded, respectively, these three fluids being respectively drawn down at the bottom e, at an intermediate point and at the top of column 8; and nitrogen gas withdrawal lines 28 from the top of the column 9 and 27 for evacuation of the waste gas (impure nitrogen) from the level of injection of the lower lean liquid. The low pressure nitrogen is heated in passages 28 of the exchanger 6 and then discharged via a line 29, while the residual gas, after heating in passages 30 of the exchanger, is used to regenerate an adsorption bottle, the bottle 2B in the example under consideration, before being discharged via a pipe 31. It can still be seen in FIG. 1 that a part of liquid oxygen 36 withdrawn at an intermediate level of the low pressure column is, after expansion in an expansion valve 32, stored in the reservoir 13 and pressurized by the pumped 14 and a liquid oxygen production is provided via a pipe 33 (medium purity) and / or 34 (high purity). Part of the medium purity liquid oxygen is vaporized after pressurization in the pump 14 in the heat exchanger 6. The pump 14 has a lower outlet pressure than the pump 12. Thus, according to the first step, the apparatus produces a high purity, high pressure oxygen flow rate and a medium purity and medium pressure oxygen flow.
Selon la deuxième marche, soit la vanne 32 est fermée et on ne soutire plus d'oxygène moyenne pression soit le débit d'oxygène moyenne pression est réduit. Dans ce cas, on augmente le soutirage du débit 16 et on vaporise plus d'oxygène haute pureté et haute pression provenant de la pompe 12 dans l'échangeur 6. Afin de vaporiser ce débit augmenté, on augmente la pression de sortie du compresseur 1 ainsi que le débit d'air comprimé en réglant les aubages du compresseur 1. S'il n'y pas de production d'oxygène liquide, la somme des débits 16 et 36 est constante, entre les première et deuxième marches car le débit d'air comprimé dans le compresseur 1 reste substantiellement constant entre les deux marches. S'il y a production d'oxygène liquide, soit la somme des débits 16 et 36 est constante, entre les première et deuxième marches, soit on peut produire une somme plus grande pendant la deuxième marche en réduisant voire en supprimant la production d'oxygène liquide. Si la production de liquide est réduite, une partie de l'air provenant de la turbine Claude 4 sera envoyé à l'atmosphère après être mélangé au gaz résiduaire 27. L'installation représentée à la Figure 2 est destinée à produire de l'oxygène gazeux à deux pressions et à deux puretés. Elle comprend essentiellement une double colonne de distillation 41 , une ligne d'échange thermique principale 42, un sous-refroidisseur 43, un compresseur d'air unique 44, une soufflante 45 de surpression d'air, une turbine de détente 46 dont la roue est montée sur le même arbre que celle du surpresseur 45, une soufflante additionnelle 47 entraînée par un moteur électrique 48, et une pompe d'oxygène liquide 49. La double colonne est constituée, de manière classique, d'une colonne moyenne pression 50 fonctionnant sous environ 6 bars et surmontée d'une colonne basse pression 51 fonctionnant légèrement au- dessus de la pression atmosphérique avec, en cuve de cette dernière, un vaporiseur-condenseur 52 qui met en relation d'échange thermique l'oxygène liquide de cuve de la colonne basse pression avec l'azote de tête de la colonne moyenne pression. En fonctionnement pendant la première marche, le compresseur d'air 44 de l'installation comprime directement la totalité de l'air à la première haute pression de l'ordre de 23 bars, et un premier courant de cet air est traité comme précédemment dans les passages 53, la turbine 46 et la vanne de détente 54 puis envoyé à la base de la colonne 50.According to the second step, the valve 32 is closed and no more medium pressure oxygen is withdrawn or the medium pressure oxygen flow is reduced. In this case, the withdrawal of the flow rate 16 is increased and more high purity oxygen and high pressure are pumped from the pump 12 into the exchanger 6. In order to vaporize this increased flow rate, the outlet pressure of the compressor 1 is increased. as well as the flow rate of compressed air by adjusting the blades of the compressor 1. If there is no production of liquid oxygen, the sum of the flow rates 16 and 36 is constant, between the first and second steps because the flow of compressed air in the compressor 1 remains substantially constant between the two steps. If liquid oxygen is produced, the sum of the flow rates 16 and 36 is constant between the first and second steps, or a greater sum can be produced during the second step by reducing or even suppressing the production of liquid oxygen. If the production of liquid is reduced, a part of the air coming from the Claude 4 turbine will be sent to the atmosphere after being mixed with the waste gas 27. The installation represented in FIG. 2 is intended to produce oxygen. gaseous at two pressures and two purities. It essentially comprises a double distillation column 41, a main heat exchange line 42, a subcooler 43, a single air compressor 44, a blower 45 of air overpressure, an expansion turbine 46 whose wheel is mounted on the same shaft as that of the booster 45, an additional fan 47 driven by an electric motor 48, and a liquid oxygen pump 49. The double column is constituted, in a conventional manner, a medium pressure column 50 operating at about 6 bar and surmounted by a low pressure column 51 operating slightly above atmospheric pressure with, in the tank of the latter, a vaporizer-condenser 52 which puts in heat exchange relation the liquid oxygen of the tank of the low pressure column with the head nitrogen of the medium pressure column. In operation during the first step, the air compressor 44 of the installation directly compresses all the air at the first high pressure of the order of 23 bar, and a first stream of this air is treated as previously in the passages 53, the turbine 46 and the expansion valve 54 then sent to the base of the column 50.
En revanche, le reste de cet air est surpressé en deux étapes, par deux soufflantes montées en série : une première soufflante 70 qui est couplée directement à la turbine 46, et une deuxième soufflante 71 directement couplée à une deuxième turbine de détente 72. L'air surpressé en 70 passe en totalité dans la soufflante 71 puis dans les passages 56 de la ligne d'échange 42, et une partie de cet air est sorti de la ligne d'échange à une température T2 supérieure à la température T1 pour être détendu dans la turbine 72. L'échappement de cette dernière, à la moyenne pression, est relié à la base de la colonne 50 comme celui de la turbine 46. L'air à la plus haute pression non détendu dans la turbine 72 poursuit son refroidissement et est liquéfié dans les passages 56 jusqu'au bout froid de la ligne d'échange, puis est détendu dans des vannes de détente 57 et 57A et réparti entre les deux colonnes 50 et 51.On the other hand, the rest of this air is supercharged in two stages, by two fans mounted in series: a first fan 70 which is coupled directly to the turbine 46, and a second fan 71 directly coupled to a second expansion turbine 72. air blown 70 passes entirely in the blower 71 and in the passages 56 of the exchange line 42, and a portion of this air is out of the exchange line at a temperature T2 greater than the temperature T1 to be expanded in the turbine 72. The exhaust of the latter, at medium pressure, is connected to the base of the column 50 as that of the turbine 46. The air at the highest pressure not relaxed in the turbine 72 continues its cooling and is liquefied in the passages 56 to the cold end of the exchange line, then is expanded in expansion valves 57 and 57A and distributed between the two columns 50 and 51.
On entend ici par « surpresseur » ou « soufflante » un compresseur à une seule roue dont la dépense d'énergie, de par le débit de gaz traité et le taux de compression, est considérablement inférieure à celle du compresseur principal 44 de l'installation, et par exemple de l'ordre de 2 à 3 % de cette dernière. Le taux de compression d'une telle soufflante est généralement inférieur à 2. Chacune des soufflantes dont il est question ici comporte à sa sortie un réfrigérant à eau ou à air atmosphérique non représenté. L'oxygène liquide soutiré en cuve de la colonne 51 est amené par la pompe 49 à la haute pression, puis vaporisé et réchauffé dans des passages 58 de la ligne d'échange avant d'être évacué de l'installation via une conduite de production 59 comme débit d'oxygène gazeux haute pression et haute pureté. L'oxygène liquide soutiré à un niveau intermédiaire de la colonne 51 est amené par la pompe 70 à la moyenne pression, puis vaporisé et réchauffé dans des passages 58 de la ligne d'échange avant d'être évacué de l'installation via une conduite de production 59 comme débit d'oxygène gazeux moyenne pression et moyenne pureté. On retrouve par ailleurs dans l'installation de la Figure 2 les conduites et accessoires habituels des installations à double colonne : une conduite 60 de remontée dans la colonne 51 du « liquide riche » (air enrichi en oxygène) recueilli en cuve de la colonne 50, avec sa vanne de détente 61 , une conduite 62 de remontée en tête de la colonne 51 du « liquide pauvre » (azote à peu prêt pur) soutiré en tête de la colonne 50, avec sa vanne de détente 83, ainsi qu'une conduite 64 de production d'oxygène liquide, piquée en cuve de la colonne 51 , qu'une conduite 65 de production d'azote liquide, piquée sur la conduite 62, et qu'une conduite 66 de soutirage d'azote impur, constituant le gaz résiduaire de l'installation, piquée en tête de la colonne 51 , cet azote impur étant réchauffé dans le sous-refroidisseur 43 puis dans des passages 67 de la ligne d'échange avant d'être évacué via une conduite 68.Here is meant by "booster" or "blower" a single-wheel compressor whose energy expenditure, by the flow of gas treated and the compression ratio, is considerably lower than that of the main compressor 44 of the installation , and for example of the order of 2 to 3% of the latter. The compression ratio of such a blower is generally less than 2. Each of the blowers in question here comprises at its output a water or atmospheric refrigerant not shown. The liquid oxygen withdrawn from the bottom of the column 51 is fed by the pump 49 to the high pressure, then vaporized and reheated in passages 58 of the exchange line before being evacuated from the installation via a production line. 59 as a flow of high pressure, high purity oxygen gas. The liquid oxygen withdrawn at an intermediate level of the column 51 is fed by the pump 70 at medium pressure, then vaporized and reheated in passages 58 of the exchange line before being evacuated from the installation via a pipe as the flow rate of gaseous oxygen medium pressure and medium purity. Furthermore, in the installation of FIG. 2, the usual conduits and accessories of the double-column installations are found: a pipe 60 for rising up in the column 51 of the "rich liquid" (air enriched with oxygen) collected in the vat of the column 50 , with its expansion valve 61, a line 62 upstream of the column 51 of the "lean liquid" (nitrogen almost pure) withdrawn at the top of the column 50, with its expansion valve 83, and a pipe 64 for producing liquid oxygen, quenched in the tank of the column 51, a line 65 for producing liquid nitrogen, stitched on the pipe 62, and that a line 66 for withdrawing impure nitrogen, constituting the waste gas from the plant, stitched at the top of the column 51, the impure nitrogen being heated in the subcooler 43 and in passages 67 of the exchange line before being discharged via a pipe 68.
Selon la deuxième marche, soit on ne soutire plus d'oxygène moyenne pression soit le débit d'oxygène moyenne pression est réduit. Dans ce cas, on augmente le soutirage du débit d'oxygène liquide en cuve de la colonne basse pression et on vaporise plus d'oxygène haute pureté et haute pression provenant de la pompe 49 dans l'échangeur 6. Afin de vaporiser ce débit augmenté, on augmente la pression de sortie du compresseur 1 ainsi que le débit d'air comprimé en réglant les aubages du compresseur 1. Alternativement ou additionnellement, on règle le débit d'air au moyen des soufflantes 70, 71.According to the second step, either no more medium pressure oxygen is withdrawn or the medium pressure oxygen flow is reduced. In this case, the withdrawal of the flow of liquid oxygen in the vat of the low pressure column is increased and more high purity oxygen and high pressure are pumped from the pump 49 into the exchanger 6. In order to vaporize this increased flow rate the output pressure of the compressor 1 and the compressed air flow are increased by adjusting the blades of the compressor 1. Alternatively or additionally, the air flow is regulated by means of the blowers 70, 71.
S'il n'y a pas de production d'oxygène liquide et le débit d'air comprimé dans le compresseur 44 reste substantiellement constant entre les deux marches la somme des débits 59 et 72 est constante, entre les première et deuxième marches. Par contre si le débit comprimé augmente pendant la deuxième marche, la somme des produits oxygénés gazeux peut augmenter. La réduction voire la suppression de la production d'oxygène liquide permet également plus de variation dans les productions gazeuses. Si la production de liquide est réduite, au moins une partie de l'air provenant d'au moins une des turbines 46,72 sera envoyée à l'atmosphère après être mélangée au gaz résiduaire 66 pendant la deuxième marche.If there is no production of liquid oxygen and the compressed air flow in the compressor 44 remains substantially constant between the two steps the sum of the flow rates 59 and 72 is constant, between the first and second steps. On the other hand, if the compressed flow rate increases during the second step, the sum of the gaseous oxygen products may increase. Reducing or even suppressing the production of liquid oxygen also allows more variation in gaseous productions. If the liquid production is reduced, at least a portion of the air from at least one of the turbines 46, 72 will be sent to the atmosphere after being mixed with the waste gas 66 during the second step.
Dans la Figure 3, un débit d'air à la pression atmosphérique est comprimé à environ 15 bars dans un compresseur principal 1. L'air est ensuite éventuellement refroidi, avant d'être épuré pour enlever les impuretés (non- illustré). L'air épuré est divisé en deux. Une partie de l'air 3 est envoyée à un surpresseur 5 où elle est comprimée jusqu'à une pression d'entre 17 et 20 bars et ensuite l'air surpressé est refroidi par un réfrigérant à l'eau 7 avant d'être envoyé au bout chaud de la ligne d'échange principal 9 de l'appareil de séparation d'air. L'air surpressé 11 se refroidit jusqu'à une température intermédiaire avant de sortir de la ligne d'échange et d'être divisé en deux fractions. Il est évidemment possible qu'une fraction du débit 11 poursuive son refroidissement jusqu'au bout froid de la ligne d'échange 9 d'où il sortira liquéfié. Une fraction 13 est envoyée dans une turbine 17 et le reste, une fraction 15 est envoyée dans une turbine 19. Les deux turbines ont la même température et pression d'aspiration et la même température et pression de sortie mais il est évidemment possible que ces températures et pression soient proches les unes des autres au lieu d'être identiques. Les deux débits turbines sont mélangés pour former un débit 21 d'air dont une partie 121 est envoyée vers la double colonne et le reste 122 vers la colonne de mélange 300. Le débit 122 constitue une partie du débit 21 ou éventuellement une fraction de la partie gazeuse du débit 21 dans le cas où celui-ci serait diphasique. Il est évidemment possible d'envoyer tout le débit 21 à la colonne moyenne pression 100 et d'en sortir une partie gazeuse 122 pour envoi à la colonne de mélange, la colonne moyenne pression remplaçant dans ce cas, le séparateur de phases. Les pressions de la colonne moyenne pression et de la colonne de mélange peuvent être différentes. En variante, la turbine 19 peut être une turbine d'insufflation débouchant à la pression de la colonne basse pression.In Figure 3, a flow of air at atmospheric pressure is compressed to about 15 bar in a main compressor 1. The air is then optionally cooled, before being purified to remove impurities (not shown). The clean air is divided in two. Part of the air 3 is sent to a booster 5 where it is compressed to a pressure of between 17 and 20 bar and then the supercharged air is cooled by a water cooler 7 before being sent to the hot end of the main exchange line 9 of the air separation apparatus. The pressurized air 11 cools to an intermediate temperature before exiting the exchange line and being divided into two fractions. It is obviously possible for a fraction of the flow 11 to continue cooling down to the cold end of the exchange line 9 from which it will exit liquefied. A fraction 13 is sent into a turbine 17 and the remainder, a fraction 15 is sent into a turbine 19. The two turbines have the same temperature and suction pressure and the same temperature and outlet pressure but it is obviously possible that these temperatures and pressure are close to each other instead of being identical. The two turbine flows are mixed to form an air flow 21 of which a portion 121 is sent to the double column and the remainder 122 to the mixing column 300. The flow 122 constitutes a part of the flow 21 or possibly a fraction of the gas part of the flow 21 in the case where it would be two-phase. It is obviously possible to send all the flow 21 to the medium pressure column 100 and to leave a gaseous part 122 for sending to the mixing column, the medium pressure column replacing in this case the phase separator. The pressures of the medium pressure column and the mixing column may be different. Alternatively, the turbine 19 may be an insufflation turbine opening to the pressure of the low pressure column.
Une autre partie 2 de l'air à 15 bars constituant le reste de l'air est refroidie dans la ligne d'échange à une température intermédiaire supérieure à la température d'aspiration des turbines 17, 19, comprimée dans un deuxième surpresseur 23 jusqu'à 30 bars environ et réintroduite dans la ligne d'échange 9 à une température plus élevée afin de poursuivre son refroidissement.Another part 2 of the air at 15 bars constituting the rest of the air is cooled in the exchange line at an intermediate temperature higher than the suction temperature of the turbines 17, 19, compressed in a second booster 23 until at about 30 bar and reintroduced into the exchange line 9 at a higher temperature to continue cooling.
Ainsi, l'air 37 à 30 bars environ se liquéfie dans la ligne d'échange et de l'oxygène liquide 25 se vaporise dans la ligne d'échange, la température de vaporisation du liquide étant proche de la température d'aspiration du deuxième surpresseur 23. L'air liquéfié sort de la ligne d'échange et est envoyé vers le système de colonnes.Thus, the air 37 to 30 bars approximately liquefies in the exchange line and the liquid oxygen 25 vaporizes in the exchange line, the vaporization temperature of the liquid being close to the suction temperature of the second blower 23. The liquefied air leaves the exchange line and is sent to the column system.
Le premier surpresseur 5 est couplé avec l'une des turbines 17, 19 et le deuxième surpresseur 23 est couplé avec l'autre des turbines 19, 17. Le système de colonnes d'un appareil de séparation d'air est constitué par une colonne moyenne pression 100 thermiquement reliée avec une colonne basse pression 200 à minaret, une colonne de mélange 300 et une colonne argon optionnelle (non-illustrée). La colonne basse pression ne comporte pas obligatoirement de minaret.The first booster 5 is coupled with one of the turbines 17, 19 and the second booster 23 is coupled with the other of the turbines 19, 17. The column system of an air separation apparatus is constituted by a medium pressure column 100 thermally connected with a low pressure column 200 to minaret, a mixing column 300 and an optional argon column (not shown). The low pressure column does not necessarily have a minaret.
La colonne moyenne pression opère à une pression de 5,5 bars mais peut opérer à une pression plus élevée.The medium pressure column operates at a pressure of 5.5 bar but can operate at a higher pressure.
L'air 121 provenant des deux turbines 17, 19 est le débit envoyé en cuve de la colonne moyenne pression 100. L'air liquéfié 37 est détendu dans la vanne 39 ou éventuellement dans une turbine et envoyé au système de colonnes.The air 121 coming from the two turbines 17, 19 is the flow rate delivered to the bottom of the medium pressure column 100. The liquefied air 37 is expanded in the valve 39 or possibly in a turbine and sent to the column system.
Du liquide riche 51 , du liquide pauvre inférieur 53 et du liquide pauvre supérieur 55 sont envoyés depuis la colonne moyenne pression 100 vers la colonne basse pression 200 après des étapes de détente dans des vannes et de sous-refroidissement.Rich liquid 51, lower lean liquid 53 and upper lean liquid 55 are sent from the medium pressure column 100 to the low pressure column 200 after expansion stages in valves and subcooling.
Il sera maintenant décrit l'opération de l'appareil selon une première marche.The operation of the apparatus will now be described in a first step.
De l'oxygène liquide est pressurisé par la pompe 500 et envoyé comme liquide pressurisé 25 vers la ligne d'échange 9. Une partie du liquide 501 peut être stocké pour servir de produit liquide. D'autres liquides, pressurisés ou non, peuvent se vaporiser dans la ligne d'échange.Liquid oxygen is pressurized by the pump 500 and sent as a pressurized liquid to the exchange line 9. Part of the liquid 501 can be stored as a liquid product. Other liquids, pressurized or not, can vaporize in the exchange line.
De l'azote gazeux est optionnellement soutiré de la colonne moyenne pression et se refroidit également dans la ligne d'échange 9.Nitrogen gas is optionally withdrawn from the medium pressure column and is also cooled in the exchange line 9.
De l'azote 33 est soutiré en tête de la colonne basse pression et se réchauffe dans la ligne d'échange, après avoir servi à sous-refroidir les liquides de reflux.Nitrogen 33 is withdrawn at the top of the low pressure column and heats up in the exchange line, after having served to sub-cool the reflux liquids.
De l'azote résiduaire 27 est soutiré d'un niveau inférieur de la colonne basse pression et se réchauffe dans la ligne d'échange 9, après avoir servi à sous-refroidir les liquides de reflux. La colonne peut éventuellement produire de l'argon en traitant un débitResidual nitrogen 27 is withdrawn from a lower level of the low pressure column and warms in the exchange line 9, after having been used to sub-cool the reflux liquids. The column can possibly produce argon by treating a flow
51 soutiré en colonne basse pression 200. Le débit 52 est le liquide de cuve renvoyé de la colonne argon, s'il y en a une.51 The flow 52 is the tank liquid returned from the argon column, if there is one.
La colonne de mélange 300 est alimentée en tête par un liquide 35 riche en oxygène soutiré à un niveau intermédiaire de la colonne basse pression 200 pressurisé par la pompe 600 et en cuve par un débit d'air gazeux 122 provenant des turbines 17, 19. La colonne de mélange opère essentiellement à la moyenne pression.The mixing column 300 is fed at the top with an oxygen rich liquid withdrawn at an intermediate level of the low pressure column 200. pressurized by the pump 600 and in the tank by a flow of gaseous air 122 from the turbines 17, 19. The mixing column operates essentially at medium pressure.
Un débit d'oxygène gazeux 137 est soutiré en tête de la colonne de mélange et se réchauffe ensuite dans la ligne d'échange 9 et un débit liquide 41 est soutiré en cuve et envoyé à la colonne basse pression après détente dans une vanne. Il est possible de soutirer un débit intermédiaire de la colonne 300 qui est envoyé à la colonne basse pression.A flow of oxygen gas 137 is withdrawn at the top of the mixing column and then warms in the exchange line 9 and a liquid flow 41 is withdrawn in the tank and sent to the low pressure column after expansion in a valve. It is possible to withdraw an intermediate flow from the column 300 which is sent to the low pressure column.
La deuxième marche diffère de la première en ce que la production d'oxygène de la colonne de mélange est réduite voire supprimée. Dans ce cas, on augmente le soutirage du débit d'oxygène liquide 35 en cuve de la colonne basse pression et on vaporise plus d'oxygène haute pureté et haute pression provenant de la pompe 600 dans l'échangeur 9 pour former le débit 125. Afin de vaporiser ce débit augmenté, on augmente la pression de sortie du compresseur 1 ainsi que le débit d'air comprimé en réglant les aubages du compresseur 1. Alternativement ou additionnellement, on règle le débit d'air et sa pression au moyen du surpresseur froid 23. Ainsi la pression de l'air 37 peut être modifiée pour la deuxième marche en modifiant les aubages du compresseur 1 et/ou ceux du surpresseur froid 23. Selon la variante de la deuxième marche où la colonne de mélange ne produit pas d'oxygène, on n'envoie plus d'air 122 en cuve de la colonne de mélange. Celle-ci n'est plus alimentée non plus en oxygène liquide et son fonctionnement est arrêté. Le surplus de l'air est envoyé à la double colonne. Le surpresseur 23 comprime l'air 2 à une pression plus élevée, ce qui permet de vaporiser plus d'oxygène liquide en augmentant le soutirage en cuve de la colonne basse pression pour pressuriser un débit plus grand dans la pompe 500. Le seul gaz riche en oxygène produit est de l'oxygène moyenne pression et moyenne pureté.The second step differs from the first in that the oxygen production of the mixing column is reduced or suppressed. In this case, the withdrawal of the flow of liquid oxygen in the tank from the low pressure column is increased and more high purity and high pressure oxygen from the pump 600 is vaporized in the exchanger 9 to form the flow 125. In order to vaporize this increased flow rate, the outlet pressure of the compressor 1 and the compressed air flow rate are increased by adjusting the blades of the compressor 1. Alternatively or additionally, the air flow and its pressure are regulated by means of the booster 23. Thus the air pressure 37 can be changed for the second step by changing the blades of the compressor 1 and / or those of the cold booster 23. According to the variant of the second step where the mixing column does not produce oxygen, it no longer sends air 122 in the tank of the mixing column. This is no longer supplied with liquid oxygen and its operation is stopped. The surplus of the air is sent to the double column. The booster 23 compresses the air 2 to a higher pressure, which makes it possible to vaporize more liquid oxygen by increasing the tank withdrawal from the low pressure column to pressurize a larger flow rate in the pump 500. The only rich gas in oxygen product is oxygen medium pressure and medium purity.
Selon une autre variante de la deuxième marche on envoie moins d'air 122 en cuve de la colonne de mélange. Celle-ci reçoit moins d'oxygène liquide 35 et son fonctionnement est réduit. Le surplus de l'air est envoyé à la double colonne.According to another variant of the second step is sent less air 122 in the tank of the mixing column. This receives less liquid oxygen and its operation is reduced. The surplus of the air is sent to the double column.
Le surpresseur 23 comprime l'air 2 à une pression plus élevée, ce qui permet de vaporiser plus d'oxygène liquide en augmentant le soutirage en cuve de la colonne basse pression pour pressuriser un débit plus grand dans la pompe 500.The booster 23 compresses the air 2 to a higher pressure, which makes it possible to vaporize more liquid oxygen by increasing the tank extraction. of the low pressure column to pressurize a larger flow rate in the pump 500.
L'appareil produit plus d'oxygène moyenne pression et moyenne pureté 25 qu'avec la première marche mais continue à produire une quantité réduite d'oxygène basse pureté et basse pression 137.The apparatus produces more medium pressure and medium purity oxygen than with the first step but continues to produce a reduced amount of low purity, low pressure oxygen.
S'il n'y a pas de production d'oxygène liquide 501 et le débit d'air comprimé dans le compresseur 1 reste substantiellement constant entre les deux marches la somme des débits 125 et 137 est constante, entre les première et deuxième marches. Par contre si le débit comprimé augmente pendant la deuxième marche, la somme des produits oxygénés gazeux peut augmenter. La réduction voire la suppression de la production d'oxygène liquide 501 permet également plus de variation dans les productions gazeuses. Si la production de liquide est réduite, au moins une partie de l'air provenant d'au moins une des turbines 17, 19 sera envoyée à l'atmosphère après être mélangée au gaz résiduaire 27 pendant la deuxième marche.If there is no liquid oxygen production 501 and the compressed air flow in the compressor 1 remains substantially constant between the two steps the sum of the flow rates 125 and 137 is constant, between the first and second steps. On the other hand, if the compressed flow rate increases during the second step, the sum of the gaseous oxygen products may increase. The reduction or even the suppression of the liquid oxygen production 501 also allows more variation in the gaseous productions. If the liquid production is reduced, at least a portion of the air from at least one of the turbines 17, 19 will be sent to the atmosphere after being mixed with the waste gas 27 during the second step.
Pendant la deuxième marche, il est souhaitable de varier le rapport des quantités d'air envoyées aux turbines 17, 19, de sorte que si le débit surpressé dans le surpresseur 23 augmente, la turbine 19 entraînant ce surpresseur reçoit un pourcentage augmenté de l'air provenant du surpresseur froid 23 et la turbine 17, évidemment un pourcentage réduit.During the second step, it is desirable to vary the ratio of the quantities of air sent to the turbines 17, 19, so that if the supercharged flow rate in the booster 23 increases, the turbine 19 driving the booster receives an increased percentage of the booster. air from the cold booster 23 and the turbine 17, obviously a reduced percentage.
Ici le surpresseur est entraîné par une turbine d'air mais il sera aisément compris que le surpresseur pourrait être entraîné par une turbine d'azote, une turbine à vapeur ou une autre turbine présente sur le site.Here the booster is driven by an air turbine but it will be easily understood that the booster could be driven by a nitrogen turbine, a steam turbine or other turbine present on the site.
L'invention permet en particulier de résoudre le problème posé quand deux appareils de séparation d'air sont produisent de l'oxygène haute pression. Si l'un des appareils n'en produit plus ou en produit moins, l'autre peut augmenter la production d'oxygène haute pression au prix de la production d'oxygène moyenne pression en fonctionnant selon l'invention. Eventuellement l'air additionnel requis peut être amené à l'autre appareil à partir d'un compresseur d'air ou d'un surpresseur d'air de l'appareil en arrêt ou marche réduite. En particulier l'invention permet à l'autre appareil permet de fournir jusqu'à 50% du produit provenant précédemment de l'appareil en arrêt ou marche réduite. II est évidemment possible de produire les deux pressions d'oxygène pendant la première et éventuellement la deuxième marche en pompant un débit unique d'oxygène dans une pompe et en détendant une partie. Dans ce cas, les débits auront évidemment la même pureté. L'appareil peut également produire de l'azote et/ou d'argon sous pression par vaporisation d'azote et d'argon pompé(s). Il est également envisageable de baisser ou arrêter les productions d'azote et/ou argon sous pression pendant la deuxième marche par rapport à la production pendant la première marche. L'appareil peut également produire de l'azote liquide comme produit final pendant la première marche. Dans ce cas, il est envisageable de réduire ou d'arrêter la production de liquide pendant la deuxième marche.In particular, the invention makes it possible to solve the problem when two air separation devices produce high pressure oxygen. If one of the devices produces more or produces less, the other can increase the production of high pressure oxygen at the cost of producing oxygen medium pressure operating according to the invention. Optionally, the additional air required can be supplied to the other apparatus from an air compressor or an air booster of the apparatus in stationary or reduced operation. In particular, the invention allows the other apparatus to provide up to 50% of the product previously from the device in stop or reduced walking. It is obviously possible to produce the two oxygen pressures during the first and possibly the second step by pumping a single flow of oxygen into a pump and by relaxing a portion. In this case, the flows will obviously have the same purity. The apparatus can also produce nitrogen and / or argon under pressure by spraying pumped nitrogen and argon (s). It is also possible to reduce or stop the production of nitrogen and / or argon under pressure during the second step compared to the production during the first step. The device can also produce liquid nitrogen as the final product during the first step. In this case, it is conceivable to reduce or stop the production of liquid during the second step.
La Figure 4 montre deux appareils de séparation d'air ASU 1 et ASU 2, dont au moins le premier ASU 1 fonctionne selon l'invention. Les deux appareils sont alimentés en air par leurs compresseurs respectifs C1 , C2. Si l'appareil ASU 2 réduit sa production d'oxygène haute pureté 15, l'ASU 1 commence à fonctionner selon la deuxième marche pour produire plus d'oxygène haute pression 15. Pour assister, de l'air épuré ou non épuré peut être envoyé du compresseur C2 à l'appareil ASU 1. Figure 4 shows two air separation units ASU 1 and ASU 2, at least the first ASU 1 works according to the invention. Both devices are supplied with air by their respective compressors C1, C2. If the ASU 2 reduces its production of high purity oxygen 15, the ASU 1 begins to operate on the second step to produce more high pressure oxygen 15. To assist, purified or unpurified air can be sent from the compressor C2 to the ASU 1.

Claims

Revendications claims
1. Procédé de séparation d'air par distillation cryogénique dans un appareil de séparation d'air comprenant un système de colonnes dans lequel i) selon une première marche a) on comprime dans un compresseur principal (1 , 44) tout l'air destiné à la distillation b) on envoie un premier débit d'air comprimé au moins dans le compresseur principal, épuré et refroidi dans une ligne d'échange (6, 42, 9) à la colonne moyenne pression (8, 50, 100) d'une double colonne c) on sépare le débit d'air en des flux enrichis en azote et en oxygène dans la colonne moyenne pression d) on envoie les flux enrichis en azote et en oxygène de la colonne moyenne pression à une colonne basse pression (9, 51 , 200) de la double colonne, directement ou indirectement e) on soutire un débit riche en azote de la colonne basse pression et on les réchauffe dans la ligne d'échange f) on soutire un débit d'oxygène liquide de la colonne basse pression, on le pressurise jusqu'à une pression élevée et on le vaporise dans la ligne d'échange pour former un premier débit gazeux riche en oxygène (15, 59, 125) et à pression élevée g) on liquéfie au moins une partie de l'air comprimé dans le compresseur principal, éventuellement après l'avoir recomprimée dans au moins un deuxième compresseur, et on envoie la partie liquéfiée à la double colonne et h) on produit également un deuxième débit gazeux riche en oxygène (1 15, 72, 137) mais à une pression moins élevée que le premier débit gazeux riche en oxygène ii) selon une deuxième marche a) on augmente la pression de liquéfaction de l'air dans en réglant les aubages du compresseur principal et éventuellement du deuxième compresseur qui fixe(nt) cette pression b) on réduit, éventuellement à zéro, la production du deuxième débit gazeux riche en oxygène c) on augmente le soutirage du premier débit gazeux riche en oxygène.A method of separating air by cryogenic distillation in an air separation apparatus comprising a column system wherein i) according to a first step a) is compressed in a main compressor (1, 44) all air intended at distillation b) a first compressed air flow is sent at least in the main compressor, purified and cooled in an exchange line (6, 42, 9) to the medium pressure column (8, 50, 100) d a double column c) the air flow is separated into flows enriched in nitrogen and oxygen in the medium pressure column d) the nitrogen and oxygen enriched streams of the medium pressure column are sent to a low pressure column ( 9, 51, 200) of the double column, directly or indirectly e) a flow rich in nitrogen from the low pressure column is withdrawn and heated in the exchange line f) a flow of liquid oxygen is withdrawn from the low pressure column, it is pressurized to a high pressure and vaporized in the exchange line to form a first gaseous flow rich in oxygen (15, 59, 125) and at high pressure g) liquefies at least a portion of the compressed air in the main compressor, optionally after recompressing it in at least a second compressor, and sending the liquefied part to the double column and h) also producing a second gas flow rich in oxygen (1 15, 72, 137) but at a lower pressure than the first gas flow rich in oxygen ii) according to a second step a) the air liquefaction pressure is increased in by adjusting the blades of the main compressor and possibly the second compressor which fixes (s) this pressure b) is reduced, possibly at zero, the production of the second gaseous flow rich in oxygen c) increasing the withdrawal of the first gas flow rich in oxygen.
2. Procédé selon la revendication 1 dans lequel le deuxième débit gazeux riche en oxygène est produit en soutirant un débit liquide (36) de la colonne basse pression et en le pressurisant à la pression moins élevée avant de le vaporiser dans la ligne d'échange.2. The method of claim 1 wherein the second gas flow rich in oxygen is produced by withdrawing a liquid flow (36) of the low pressure column and pressurizing it at the lower pressure before vaporizing in the exchange line. .
3. Procédé selon la revendication 1 dans lequel le deuxième débit gazeux riche en oxygène est produit en soutirant un débit gazeux d'une colonne de mélange (300) alimentée par de l'air ou de la colonne basse pression.3. The method of claim 1 wherein the second gas flow rich in oxygen is produced by withdrawing a gas flow of a mixing column (300) supplied with air or low pressure column.
4. Procédé selon l'une des revendications précédentes dans lequel l'au moins un deuxième compresseur (5) comprime tout l'air destiné à l'appareil.4. Method according to one of the preceding claims wherein the at least one second compressor (5) compresses all the air for the device.
5. Procédé selon l'une des revendications 1 à 3 dans lequel l'au moins un deuxième compresseur (70, 71 , 23) ne comprime qu'une partie de l'air destiné à l'appareil.5. Method according to one of claims 1 to 3 wherein the at least one second compressor (70, 71, 23) compresses only a portion of the air for the device.
6. Procédé selon la revendication 5 dans lequel lors de la deuxième marche, on augmente le débit envoyé au deuxième compresseur(70, 71 , 23).6. The method of claim 5 wherein during the second step, the flow rate is sent to the second compressor (70, 71, 23).
7. Procédé selon la revendication 6 dans lequel une partie de l'air comprimé dans le deuxième compresseur (70, 71 , 23) est détendu dans une turbine puis envoyé à la double colonne et dans lequel le débit détendu (15) pendant la deuxième marche réduit par rapport à celui pendant la première marche.7. The method of claim 6 wherein a portion of the compressed air in the second compressor (70, 71, 23) is expanded in a turbine and sent to the double column and in which the expanded flow (15) during the second walking reduced compared to that during the first walk.
8. Procédé selon l'une des revendications 1 à 5 dans lequel lors de la deuxième marche on maintient constant le débit envoyé au deuxième compresseur (70, 71 , 23) par rapport au même débit pendant la première marche.8. Method according to one of claims 1 to 5 wherein during the second step is maintained constant flow sent to the second compressor (70, 71, 23) with respect to the same flow during the first step.
9. Procédé selon la revendication 8 dans lequel on augmente la quantité de gaz envoyée une turbine (19, 46, 72) entraînant le deuxième compresseur (70, 71 , 23) dans la deuxième marche par rapport à celle envoyée pendant la première marche.9. The method of claim 8 wherein increasing the amount of gas sent a turbine (19, 46, 72) driving the second compressor (70, 71, 23) in the second step compared to that sent during the first step.
10. Procédé suivant une des revendications précédentes tel que le premier débit riche en oxygène (15, 59, 125) a une pureté supérieure à 98.5%, et le deuxième débit riche en oxygène (115, 72, 137) a une pureté inférieure à 98%.The method according to one of the preceding claims, wherein the first oxygen-rich flow (15, 59, 125) has a purity greater than 98.5%, and the second oxygen-rich flow (115, 72, 137) has a purity lower than 98%.
11. Procédé selon l'une des revendications précédentes dans lequel lors de la première marche on soutire de la double colonne en tant que produit final un débit liquide riche en oxygène (34, 501 ) et lors de la deuxième marche le soutirage de ce débit est réduit, éventuellement à zéro.11. Method according to one of the preceding claims wherein during the first step is withdrawn from the double column as a final product oxygen-rich liquid flow (34, 501) and in the second step the withdrawal of this flow rate. is reduced, possibly to zero.
12. Procédé selon l'une des revendications précédentes dans lequel la somme des premier et deuxième débits riches en oxygène est substantiellement constante entre la première et la deuxième marches.12. Method according to one of the preceding claims wherein the sum of the first and second flow rich in oxygen is substantially constant between the first and second steps.
13. Procédé selon l'une des revendications précédentes dans lequel pendant la première marche un débit d'air est détendu dans une turbine (4, 46, 72, 19) et envoyé à la double colonne et pendant la deuxième marche soit le débit détendu est rejeté à l'atmosphère soit une partie du débit détendu est envoyée à la double colonne alors que le reste est rejeté à l'atmosphère.13. Method according to one of the preceding claims wherein during the first step a flow of air is expanded in a turbine (4, 46, 72, 19) and sent to the double column and during the second step is the flow relaxed is released to the atmosphere or a portion of the expanded flow is sent to the double column while the rest is released to the atmosphere.
14. Procédé selon l'une des revendications précédentes dans lequel pendant la deuxième marche on envoie de l'air comprimé à la double colonne provenant d'un compresseur de secours.14. Method according to one of the preceding claims wherein during the second step is sent compressed air to the double column from a backup compressor.
15. Procédé suivant une des revendications précédentes dans lequel une partie de l'air traité vient d'une soufflante de haut fourneau.15. Method according to one of the preceding claims wherein a portion of the treated air comes from a blast furnace blower.
16. Procédé selon l'une des revendications précédentes dans lequel pendant la première marche on produit un débit d'azote sous pression et/ou d'argon sous pression par vaporisation de liquide pressurisé et pendant la deuxième marche on réduit ou on arrête la production de ce(s) débit(s). 16. Method according to one of the preceding claims wherein during the first step is produced a flow of nitrogen under pressure and / or argon under pressure by vaporization of pressurized liquid and during the second step is reduced or stopped production of this (s) debit (s).
17. Procédé selon l'une des revendications précédentes dans lequel pendant la première marche on produit un débit d'azote liquide et/ou d'argon liquide comme produit final et pendant la deuxième marche, on réduit ou on arrête cette (ces) production(s).17. Method according to one of the preceding claims wherein during the first step is produced a flow of liquid nitrogen and / or liquid argon as the final product and during the second step, it reduces or stops this (these) production (s).
18. Procédé selon l'une des revendications précédentes dans lequel les premier et deuxième débits riche en oxygène ont la même pureté ou des puretés différentes.18. Method according to one of the preceding claims wherein the first and second flow rich in oxygen have the same purity or different purities.
19. Procédé selon l'une des revendications 1 à 3 ou 8 à 18 dans lequel le compresseur principal amène tout l'air à la pression de liquéfaction de l'air.19. Method according to one of claims 1 to 3 or 8 to 18 wherein the main compressor brings all the air at the liquefaction pressure of the air.
20. Procédé de fourniture d'un débit d'oxygène haute pression dans lequel selon une première marche chacune de deux installations de séparation d'air (ASU 1 , ASU 2) fournit de l'oxygène haute pression (15) et selon une deuxième marche, une première des deux installations (ASU 1 ) fournit un débit d'oxygène haute pression augmenté par rapport à celui selon la première marche et la deuxième installation fournit un débit réduit, voire à zéro ; au moins la première installation fonctionnant selon l'une des revendications précédentes et fournissant en plus de sa production initiale d'oxygène haute pression au moins 50% de la quantité d'oxygène haute pression produite pendant la première marche par la deuxième installation.20. A method for supplying a high-pressure oxygen flow rate in which, according to a first step, each of two air separation plants (ASU 1, ASU 2) supplies high-pressure oxygen (15) and according to a second in operation, a first of the two installations (ASU 1) provides an increased high pressure oxygen flow rate relative to that in the first step and the second installation provides a reduced flow, or even zero; at least the first plant operating according to one of the preceding claims and providing in addition to its initial production of high pressure oxygen at least 50% of the amount of high pressure oxygen produced during the first step by the second installation.
21. Procédé selon la revendication 20 dans lequel un compresseur d'air (C2) de la deuxième installation envoie de l'air comprimé à la première installation pendant la deuxième marche. 21. The method of claim 20 wherein an air compressor (C2) of the second installation sends compressed air to the first installation during the second step.
PCT/FR2006/051350 2005-12-15 2006-12-14 Process for separating air by cryogenic distillation WO2007068858A2 (en)

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