EP1318368A1 - Méthode de séparation d'air pour la production d'un produit gazeux à débit variable - Google Patents

Méthode de séparation d'air pour la production d'un produit gazeux à débit variable Download PDF

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Publication number
EP1318368A1
EP1318368A1 EP01310298A EP01310298A EP1318368A1 EP 1318368 A1 EP1318368 A1 EP 1318368A1 EP 01310298 A EP01310298 A EP 01310298A EP 01310298 A EP01310298 A EP 01310298A EP 1318368 A1 EP1318368 A1 EP 1318368A1
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EP
European Patent Office
Prior art keywords
air
liquid
stream
demand
product
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP01310298A
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German (de)
English (en)
Inventor
Paul Higginbotham
Niranjan Sundaram
Leighton Baines Wilson
Joseph Straub
Joseph P Naumovitz
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Linde LLC
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BOC Group Inc
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Publication date
Application filed by BOC Group Inc filed Critical BOC Group Inc
Priority to EP01310298A priority Critical patent/EP1318368A1/fr
Publication of EP1318368A1 publication Critical patent/EP1318368A1/fr
Withdrawn legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04006—Providing pressurised feed air or process streams within or from the air fractionation unit
    • F25J3/04078—Providing pressurised feed air or process streams within or from the air fractionation unit providing pressurized products by liquid compression and vaporisation with cold recovery, i.e. so-called internal compression
    • F25J3/0409—Providing pressurised feed air or process streams within or from the air fractionation unit providing pressurized products by liquid compression and vaporisation with cold recovery, i.e. so-called internal compression of oxygen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04006—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
    • F25J3/04103—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 using solely hydrostatic liquid head
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04254—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using the cold stored in external cryogenic fluids
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04284—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams
    • F25J3/0429—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams of feed air, e.g. used as waste or product air or expanded into an auxiliary column
    • F25J3/04296—Claude expansion, i.e. expanded into the main or high pressure column
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04406—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using a dual pressure main column system
    • F25J3/04412—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using a dual pressure main column system in a classical double column flowsheet, i.e. with thermal coupling by a main reboiler-condenser in the bottom of low pressure respectively top of high pressure column
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04472—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using the cold from cryogenic liquids produced within the air fractionation unit and stored in internal or intermediate storages
    • F25J3/04496—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using the cold from cryogenic liquids produced within the air fractionation unit and stored in internal or intermediate storages for compensating variable air feed or variable product demand by alternating between periods of liquid storage and liquid assist
    • F25J3/04503—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using the cold from cryogenic liquids produced within the air fractionation unit and stored in internal or intermediate storages for compensating variable air feed or variable product demand by alternating between periods of liquid storage and liquid assist by exchanging "cold" between at least two different cryogenic liquids, e.g. independently from the main heat exchange line of the air fractionation and/or by using external alternating storage systems
    • F25J3/04509—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using the cold from cryogenic liquids produced within the air fractionation unit and stored in internal or intermediate storages for compensating variable air feed or variable product demand by alternating between periods of liquid storage and liquid assist by exchanging "cold" between at least two different cryogenic liquids, e.g. independently from the main heat exchange line of the air fractionation and/or by using external alternating storage systems within the cold part of the air fractionation, i.e. exchanging "cold" within the fractionation and/or main heat exchange line
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04472—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using the cold from cryogenic liquids produced within the air fractionation unit and stored in internal or intermediate storages
    • F25J3/04496—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using the cold from cryogenic liquids produced within the air fractionation unit and stored in internal or intermediate storages for compensating variable air feed or variable product demand by alternating between periods of liquid storage and liquid assist
    • F25J3/04503—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using the cold from cryogenic liquids produced within the air fractionation unit and stored in internal or intermediate storages for compensating variable air feed or variable product demand by alternating between periods of liquid storage and liquid assist by exchanging "cold" between at least two different cryogenic liquids, e.g. independently from the main heat exchange line of the air fractionation and/or by using external alternating storage systems
    • F25J3/04509—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using the cold from cryogenic liquids produced within the air fractionation unit and stored in internal or intermediate storages for compensating variable air feed or variable product demand by alternating between periods of liquid storage and liquid assist by exchanging "cold" between at least two different cryogenic liquids, e.g. independently from the main heat exchange line of the air fractionation and/or by using external alternating storage systems within the cold part of the air fractionation, i.e. exchanging "cold" within the fractionation and/or main heat exchange line
    • F25J3/04515—Simultaneously changing air feed and products output
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/40—Air or oxygen enriched air, i.e. generally less than 30mol% of 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
    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/42—Nitrogen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2215/00—Processes characterised by the type or other details of the product stream
    • F25J2215/40—Air or oxygen enriched air, i.e. generally less than 30mol% of O2

Definitions

  • the present invention relates to a method of separating air to produce a gaseous product to meet a varying demand for it.
  • the air is generally separated by being purified to remove impurities of low volatility, cooled to near its dew point, and separated in a double rectification column comprising a higher pressure rectification column, a lower pressure rectification column, and a condenser-reboiler placing the top of the higher pressure column in heat exchange relationship with the bottom of the lower pressure column.
  • liquid oxygen that has been previously produced during a low demand period and stored within a storage tank, is pressurised by being pumped and then fully vaporised within the main heat exchanger of the air separation plant against condensing flow of air that has been boosted in pressure to well above the operating pressure of the higher pressure column.
  • the resultant condensed air stream is in part stored and in part introduced into the higher pressure distillation column.
  • the previously stored liquid air is supplied to the higher pressure distillation column.
  • a practical difficulty in effectuating a process such as been described above is that during periods of high demand, more air must be further compressed and therefore liquefied in order to vaporise the increase in the flow rate of product.
  • Inlet flow to the booster compressor can vary by as much as 50%.
  • Most known compressors are not able to accommodate such a variation of inlet flow without recirculating of the outlet flow.
  • part of the outlet flow of the compressor must be recirculate back to the inlet.
  • the compressor must be sized, however, to produce the requisite outlet flow.
  • the booster compressor has an over capacity when flow rates are 50% and therefore, practically, a larger compressor is used than would theoretically be necessary. This is not efficient from standpoints of both equipment cost and electrical power usage.
  • the present invention makes it possible to meet a demand cycle without excessive swings of air flow rate for further compression (typically in a booster-compressor) and thereby permits more efficient compressor utililisation.
  • a method of separating air to produce a first gaseous product, enriched in a component of the air in accordance with a demand cycle having high and low periods of demand, and a second liquid product comprising:
  • condensation encompasses not only a process in which a substance changes state from a vapour to a liquid, but also to processes in which a supercritical fluid is depressurised, after having been fully cooled, to produce a liquid.
  • refrigeration is produced by expanding a second further compressed air stream with performance of work, thereby to refrigerate the low temperature rectification process and to permit production of the first and second liquid streams and also, producing a liquid product composed of the second liquid stream.
  • the flow rate of the air to be further compressed during the low period of demand is greater than that that would otherwise have been required had the liquid product not been produced.
  • the advantage of the foregoing method is that increasing the air flow rate of the air to be further compressed, while resulting in an increase in compression requirements, actually reduces the required percentage increase between high and low demand periods that would otherwise have occurred.
  • production can be made to vary as can the amount of further compressed air that serves refrigeration purposes.
  • the air that is further compressed can serve in vaporizing the pressurized liquid product and thus air flow swings to the main air compressor can be further reduced.
  • a process can be carried out in which the air flow rate to the booster compressor remains unchanged during periods of both high and low demand.
  • air separation apparatus 1 in accordance with the present invention is illustrated that can be used to produce both gaseous nitrogen and gaseous oxygen products.
  • air after having been filtered in a filter 10 is compressed by a main air compressor 12.
  • the heat of compression is removed from the resultant compressed air by an after-cooler 14.
  • the air is further purified by removal of impurities such as carbon dioxide and moisture by a known prepurification unit 16.
  • the air is further compressed by a booster compressor 18 to form a further compressed air stream 20.
  • Further compressed air stream 20 is introduced into a main heat exchanger 22 where it is cooled against other warming streams passing countercurrently through main heat exchanger 22.
  • main heat exchanger 22 is illustrated as a single unit, in practice, the heat exchanger might be a heat exchanger complex of several heat exchangers.
  • Further compressed air stream 20 after having been partly cooled, that is cooled to a temperature that is less than the temperature at the warm end and greater than the temperature at the cold end of main heat exchanger 22, is divided into first and second further compressed air streams 24 and 26.
  • First further compressed air stream 24 is cooled to a liquefaction temperature and second further compressed air stream 26 is turboexpanded within a turboexpander 28 to produce a refrigerant stream 30.
  • Refrigerant stream 30 adds refrigeration to air separation apparatus 1 and helps in making a liquid product.
  • turboexpander 28 provides most of the refrigeration. It is possible, however, to conduct a method in accordance with the present invention by supplementing the refrigeration by liquid assist (i.e. the introduction of liquid nitrogen or liquid air from a separate source into the apparatus) as for instance during periods of high demand for product. In fact during such high periods of demand, all of the refrigeration might be supplied by liquid assist.
  • liquid assist i.e. the introduction of liquid nitrogen or liquid air from a separate source into the apparatus
  • a compressed air stream 32 is formed by diversion of part of the prepurified air upstream of the booster compressor 18 to the main heat exchanger 22.
  • Compressed air stream 32 is cooled to approximately its dew point and combined with refrigerant stream 30.
  • the resultant stream is introduced into the bottom of an air separation unit 34.
  • Air separation unit 34 consists of a higher pressure column 36 and a lower pressure column 38.
  • Higher and lower pressure columns 36 and 38 contain mass transfer elements, which can consist of trays or packing, either random or structured.
  • Higher pressure column 36 functions to distil the incoming air to produce a nitrogen rich overhead traction and a crude liquid oxygen bottom fraction.
  • Higher pressure column 36 is refluxed by removing a nitrogen rich stream 40 from the overhead fraction and condensing such stream in a condenser reboiler 42 to produce a reflux stream 44.
  • Reflux stream 44 is divided into two parts. One part 46 is used to reflux higher pressure column 36.
  • the other part 48 is subcooled within the subcooling unit 50, expanded through an expansion valve 52 to the pressure of the lower pressure column 38, and then introduced as reflux into lower pressure column 38.
  • the crude liquid oxygen produced as the bottom fraction of higher pressure column 36 is extracted as a crude liquid oxygen stream 54 for further refinement in the lower pressure column 38.
  • Crude liquid oxygen stream 54 is subcooled within subcooling unit 50 and expanded through an expansion valve 56 before introduction into lower pressure column 38 for further refinement.
  • This further refinement produces an oxygen rich liquid bottom fraction within lower pressure column 38.
  • the oxygen-rich liquid bottom fraction is boiled by condenser-reboiler 42 to produce boil up within lower pressure column 38.
  • the oxygen-rich liquid fraction is the source of the oxygen product (s).
  • High purity oxygen products to wit: having a purity above 99% or relatively impure oxygen products, for instance, oxygen enriched air at 30% may be separated.
  • Lower pressure column 38 also produces a gaseous nitrogen stream 58 which passes counter currently through subcooling unit 50 to subcool part 48 of reflux stream 44 and crude liquid oxygen stream 54 before fully warming within heat exchanger 22 and being discharged from the process.
  • Apparatus 1 is designed to function to produce a gaseous oxygen product at elevated pressure at greater output during periods of high demand than that required at periods of low demand.
  • a liquid oxygen stream 60 is extracted from the lower pressure column 38 and divided into first and second liquid streams 62 and 64.
  • the first stream 62 is introduced into a liquid storage tank 66.
  • the second liquid stream 64 is introduced via a valve 67 into liquid product tank 68 from which liquid oxygen product stream 70 can be extracted.
  • a liquid oxygen stream 72 is taken from the tank 66 and is pressurised by operation of a pump 74.
  • the pressurised liquid oxygen stream is vaporized within main heat exchanger 22 to produce the gaseous oxygen product at a chosen pressure.
  • a hydrostatic head can be utilized to pressurise the liquid provided that the pressure at which the gaseous oxygen product is required is not too high.
  • a single liquid oxygen storage tank may replace the storage tanks 66 and 68 with both the streams 70 and 72 being taken therefrom.
  • apparatus 1 is continually loaded by production of a liquid product stream 70 in addition to the gaseous product.
  • turboexpander 28 is turned down.
  • turboexpander 28 is provided with variable inlet vanes to control the flow thereto.
  • the illustrated compressor 18 is provided with a similar arrangement.
  • turboexpander 28 will cause an excess flow, that would otherwise have gone into turboexpander 28 to form the make-up of first further compressed air stream 24.
  • Such operation provides more available air to be liquefied and therefore more liquid air for use in vaporising liquid oxygen product stream 72. Since, however, there will be less refrigeration, there will be less liquid produced and thus, valve 67 will be turned down so that more liquid oxygen will flow to liquid oxygen storage tank 66.
  • the entire system may be adjusted so that booster compressor 18 sees no change in air flow and main air flow compressor 12 sees only a slight change in air flow.
  • Case 1 is a comparative known production method in which no liquid product is taken.
  • Case 2 involves the production of a liquid product in the amount of 30 tons per day.
  • Case 3 involves an average liquid production of 30 tons per day.
  • the liquid production in Case 3 is not however constant and varies.
  • Case I there is a flow to booster compressor 18 varying (between high and low demand periods) by about 48%.
  • the variance is reduced to about 31%.
  • case III the flow to booster compressor 18 is constant.
  • the present invention has applicability not only to pressurized oxygen production but also to production of pressurized nitrogen.
  • a liquid nitrogen product is produced instead of a liquid oxygen product.
  • more than one turbo-expansion can be employed at more than one temperature.
  • an argon column can be provided for the production of argon.
  • the liquid oxygen to be pumped (or any alternative product) could be stored in a pressurized state. This would allow the pump 74 to run at a constant nominal rate to conserve energy.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Emergency Medicine (AREA)
  • Separation By Low-Temperature Treatments (AREA)
EP01310298A 2001-12-10 2001-12-10 Méthode de séparation d'air pour la production d'un produit gazeux à débit variable Withdrawn EP1318368A1 (fr)

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EP01310298A EP1318368A1 (fr) 2001-12-10 2001-12-10 Méthode de séparation d'air pour la production d'un produit gazeux à débit variable

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EP01310298A EP1318368A1 (fr) 2001-12-10 2001-12-10 Méthode de séparation d'air pour la production d'un produit gazeux à débit variable

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EP1318368A1 true EP1318368A1 (fr) 2003-06-11

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0556861A1 (fr) * 1992-02-21 1993-08-25 Praxair Technology, Inc. Système de séparation cryogénique d'air pour la production d'oxygène gazeuse
US5526647A (en) * 1994-07-29 1996-06-18 L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude Process and installation for the production of gaseous oxygen under pressure at a variable flow rate
US6062044A (en) * 1996-07-25 2000-05-16 L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude Method and plant for producing an air gas with a variable flow rate
US6357259B1 (en) * 2000-09-29 2002-03-19 The Boc Group, Inc. Air separation method to produce gaseous product

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0556861A1 (fr) * 1992-02-21 1993-08-25 Praxair Technology, Inc. Système de séparation cryogénique d'air pour la production d'oxygène gazeuse
US5526647A (en) * 1994-07-29 1996-06-18 L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude Process and installation for the production of gaseous oxygen under pressure at a variable flow rate
US6062044A (en) * 1996-07-25 2000-05-16 L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude Method and plant for producing an air gas with a variable flow rate
US6357259B1 (en) * 2000-09-29 2002-03-19 The Boc Group, Inc. Air separation method to produce gaseous product

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