WO2024256036A1 - Method and apparatus for producing air products from an oxygen fraction - Google Patents

Method and apparatus for producing air products from an oxygen fraction Download PDF

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Publication number
WO2024256036A1
WO2024256036A1 PCT/EP2024/025179 EP2024025179W WO2024256036A1 WO 2024256036 A1 WO2024256036 A1 WO 2024256036A1 EP 2024025179 W EP2024025179 W EP 2024025179W WO 2024256036 A1 WO2024256036 A1 WO 2024256036A1
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WO
WIPO (PCT)
Prior art keywords
krypton
xenon
rectification
liquid
feed mixture
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.)
Ceased
Application number
PCT/EP2024/025179
Other languages
French (fr)
Inventor
Chao Liang
Edward Colman
Daniel OTTE
Christian Hermann
Kathrin Hummel
Christian Kunz
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Linde GmbH
Original Assignee
Linde GmbH
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 Linde GmbH filed Critical Linde GmbH
Priority to EP24736652.9A priority Critical patent/EP4728229A1/en
Priority to KR1020257041281A priority patent/KR20260022947A/en
Priority to CN202480039074.8A priority patent/CN121358995A/en
Publication of WO2024256036A1 publication Critical patent/WO2024256036A1/en
Anticipated expiration legal-status Critical
Ceased 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
    • F25J3/04642—Recovering noble gases from air
    • F25J3/04745—Krypton and/or Xenon
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04151—Purification and (pre-)cooling of the feed air; recuperative heat-exchange with product streams
    • F25J3/04187—Cooling of the purified feed air by recuperative heat-exchange; Heat-exchange with product streams
    • F25J3/0423—Subcooling of liquid process streams
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04254—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using the cold stored in external cryogenic fluids
    • F25J3/0426—The cryogenic component does not participate in the fractionation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04333—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using quasi-closed loop internal vapor compression refrigeration cycles, e.g. of intermediate or oxygen enriched (waste-)streams
    • F25J3/04351—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using quasi-closed loop internal vapor compression refrigeration cycles, e.g. of intermediate or oxygen enriched (waste-)streams of nitrogen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04763—Start-up or control of the process; Details of the apparatus used
    • F25J3/04866—Construction and layout of air fractionation equipments, e.g. valves, machines
    • F25J3/0489—Modularity and arrangement of parts of the air fractionation unit, in particular of the cold box, e.g. pre-fabrication, assembling and erection, dimensions, horizontal layout "plot"
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04763—Start-up or control of the process; Details of the apparatus used
    • F25J3/04866—Construction and layout of air fractionation equipments, e.g. valves, machines
    • F25J3/04969—Retrofitting or revamping of an existing air fractionation unit
    • 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
    • F25J3/08—Separating gaseous impurities from gases or gaseous mixtures or from liquefied gases or liquefied gaseous mixtures
    • 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
    • F25J2200/02—Processes or apparatus using separation by rectification in a single pressure main column system
    • 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
    • F25J2200/04—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
    • F25J2200/30—Processes or apparatus using separation by rectification using a side column in a single pressure column system
    • 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
    • F25J2200/50—Processes or apparatus using separation by rectification using multiple (re-)boiler-condensers at different heights of the 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
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/60—Processes or apparatus using other separation and/or other processing means using adsorption on solid adsorbents, e.g. by temperature-swing adsorption [TSA] at the hot or cold end
    • 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
    • F25J2210/06—Splitting of the feed stream, e.g. for treating or cooling in different ways
    • 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
    • F25J2215/50—Oxygen or special cases, e.g. isotope-mixtures or low purity O2
    • F25J2215/56—Ultra high purity oxygen, i.e. generally more than 99,9% 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
    • F25J2220/00—Processes or apparatus involving steps for the removal of impurities
    • F25J2220/50—Separating low boiling, i.e. more volatile components from oxygen, e.g. N2, Ar
    • 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
    • F25J2220/00—Processes or apparatus involving steps for the removal of impurities
    • F25J2220/52—Separating high boiling, i.e. less volatile components from oxygen, e.g. Kr, Xe, Hydrocarbons, Nitrous oxides, O3
    • 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
    • F25J2235/00—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams
    • F25J2235/50—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams the fluid being oxygen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2245/00—Processes or apparatus involving steps for recycling of process streams
    • F25J2245/90—Processes or apparatus involving steps for recycling of process streams the recycled stream being boil-off gas from storage
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2290/00—Other details not covered by groups F25J2200/00 - F25J2280/00
    • F25J2290/34—Details about subcooling of liquids

Definitions

  • the present invention relates to a method and to an apparatus for producing air products, particularly including a krypton/xenon mixture and oxygen.
  • the noble gases krypton and xenon which are contained in atmospheric air at concentrations of about 1 ppm and about 0.09 ppm can be obtained by processing considerable amounts of air in air separation units.
  • the boiling temperatures of krypton and xenon are well above the boiling temperatures of nitrogen and oxygen.
  • the task of producing krypton and/or xenon products includes an enrichment to obtain a krypton/xenon mixture and separating said mixture as further explained below.
  • a krypton-xenon enrichment column integrated in the main air separation plant for separating nitrogen and oxygen.
  • Such enrichment column is, however, not installed in about 95 % of the existing air separation units. Therefore, they cannot be used for the production of krypton and xenon.
  • the direct oxygen product upstream a possible krypton-xenon enrichment column
  • the present invention provides a method and an apparatus for producing air products, particularly including a krypton/xenon mixture and oxygen, comprising the features of the independent claims, such features being able to be connected to an existing air separation plant without changing the air separation plant itself and providing an enrichment of krypton and xenon which is worth to be transported to a separate krypton-xenon enrichment unit.
  • Embodiments are subject of the dependent claims and of the explanations that follow hereinbelow.
  • the liquid feed mixture may comprise:
  • the feed mixture comprises more than 90 mol-%, more preferably more than 98 mol-%, even more preferably more than 98 mol-%, for example 98 to 99.9 mol-% oxygen.
  • the liquid feed mixture or a part thereof is subjected to a rectification providing a first fraction depleted in oxygen and enriched in krypton and xenon relative to the feed mixture and a second fraction enriched in oxygen and depleted in krypton and xenon relative to the feed mixture.
  • the first fraction and the second fraction are withdrawn from a rectification column arrangement used in the rectification in liquid form, the liquid feed mixture or the part thereof subjected to the rectification is introduced with a proportion of liquid of 90% or more, particularly of 95% or more or 99% or more, particularly in an essentially liquid form, into the rectification column arrangement, and a total feed to the rectification column arrangement is made up to at least 90%, particularly of at least 95% or 99%, particularly essentially completely, by the liquid feed mixture or the part thereof subjected to the rectification.
  • the feed mixture will be in liquid state. Firstly, such a liquid is easier to transport and to store than a gas; secondly it can be directly used as a reflux liquid in the krypton-xenon rectification system.
  • the rectification system for krypton-xenon has its own coldbox, enclosing the column(s) of such rectification system only and no other separation columns, in particular not of the main air separation plant for nitrogen-oxygen separation.
  • Such coldbox may, however, enclose other parts of the rectification system like heat exchangers, pipelines, valves and/or possibly other cold parts, e.g. a cryogenic adsorption system.
  • the krypton-xenon rectification system of the invention is retrofit-ready, i.e. it can be added to an existing tank or air separation unit without opening the insulation of the tank or the ASU.
  • a "coldbox” is an insulating enclosure having walls normally made of metal sheets and having an insulation in the walls (e.g. vacuum insulation) or at the inner surface of the walls or by filling its interior (outside the apparatus parts themselves) with powder or granulate material like perlite.
  • the insulation methods mentioned may, of course be combined.
  • compositions, fluid, stream, etc. when used herein to describe constituents of a composition, fluid, stream, etc., shall indicate that, in addition to one or more specified constituents, one or more further constituents may be present in the composition, fluid, stream, etc., but that the essential features of the composition, stream, etc., in terms of at least one of physical properties, chemical properties, reactivity in one or more reaction units, treatability in one or more treatment units, compatibility with one or more materials, etc., are not significantly, not practically, or neglectably changed by the one or more further constituents.
  • the one or more specified constituents may make up at least 90%, particularly at least 95%, 99%, 99.9%, 99.99% or 99.999% of the composition, stream, etc.
  • Terms such as “essentially free from”, etc. may refer to one or more constituents being present in a composition, fluid, stream, etc., in minor amounts which likewise do not influence the essential features referred to above, such as in amounts of less than 10%, 5%, 1%, 0.1%, 0.01% or 0.001%.
  • compositions, fluid, stream, etc. being made up from, or being formed by, etc., “essentially” one or more other compositions, fluids, streams, etc.
  • a reference to a composition, fluid, stream, etc., being made up from, or being formed by, etc., “essentially” one or more other compositions, fluids, streams, etc. shall indicate that such a composition, fluid, stream, etc., may also include parts from other sources, i.e., compositions, fluids, streams, etc., but that these generally only contribute to a small part to the overall amount. That is, the one or more compositions, fluids, streams, etc., specified as being made up from, or being formed by, “essentially” one or more specified compositions, fluids, streams, etc., may be provided from the one or more specified compositions, fluids, streams, etc., by at least 90%, particularly at least 95% or 99%. All percentage values indicated herein, if not otherwise indicated or excluded by the technical understanding of the skilled person, may refer to volume, weight,
  • the liquid feed mixture comprises 4 to 7 or 5 to 6 ppm by volume krypton, 0.2 to 0.6 or 0.3 to 0.5 ppm by volume xenon, and 99.5 to 99.9 % by volume oxygen.
  • Embodiments of the present invention may therefore be used for treating liquid oxygen withdrawn from the sump of a low-pressure column of an air separation unit as generally known from the prior art.
  • the liquid feed mixture is provided using a liquid withdrawn from a cryogenic storage tank.
  • the storage tank may be the usual liquid oxygen product and/or backup tank which belongs to an air separation plant or a set of air separation plants.
  • the liquid withdrawn from the cryogenic storage tank comprises one or more hydrocarbons and providing the liquid feed mixture comprises removing at least a part of the hydrocarbons from the liquid withdrawn from the cryogenic storage tank. Removal of hydrocarbons may be performed upstream the rectification column arrangement using methods as known in the prior art which may be adapted to the proposed process if necessary, according to the understanding of the skilled person.
  • An embodiment of the present invention includes that the liquid withdrawn from the cryogenic storage tank is at least in part made up by a liquid produced in one or more air separation units and stored in the cryogenic storage tank, as mentioned.
  • the cold needed for driving the rectification system is preferably provided by liquid nitrogen e.g. taken from a LIN tank, a nearby nitrogen liquefier or an air separation plant producing liquid nitrogen.
  • LIN tank may be filled by a remote source or by an air separation plant that delivers the liquid feed mixture or fills the LOX tank, the liquid feed mixture is taken from.
  • the rectification column arrangement comprises a rectification column with sump evaporator and a head condenser.
  • This rectification column is referred to herein as a “first” rectification column at certain places, even if it may be the sole rectification column in the rectification column arrangement.
  • the sump evaporator may be heated using gaseous nitrogen and/or wherein the head condenser may be cooled using liquid nitrogen.
  • the same fraction, e.g. nitrogen is used for both purposes.
  • the liquid nitrogen is or produced by a recycle attached to the rectification column arrangement and made up by external gaseous nitrogen from a nitrogen pipeline connected to a pipeline network or to a near air separation plant producing pressurized nitrogen.
  • Such air separation plant may or may not be the one delivering the feed mixture.
  • the gaseous nitrogen used for heating the sump evaporator is, after having been used for heating the sump evaporator, at least in part expanded into the head condenser, more precisely into an evaporation space thereof, to form a part of the liquid nitrogen used for cooling the head condenser.
  • the gaseous nitrogen used for heating the sump evaporator may be cooled during said heating the sump evaporator to an extent that it is partly or completely liquefied or brought close to the liquefaction temperature at an elevated pressure. Expansion into the head condenser then may cause (further) liquefaction.
  • the gaseous nitrogen after use for cooling the head condenser may at least in part be subjected to a compression step and a cooling step before being used for heating the sump evaporator. Suitable pressure and temperature levels are used as required to perform a satisfactory separation.
  • a nitrogen cooling cycle may be formed. That is, gaseous nitrogen may be withdrawn from the head condenser, more precisely from an evaporation space thereof, and used at least in part used as the gaseous nitrogen used for heating the sump evaporator. Said gaseous nitrogen withdrawn from the head condenser may, together with gaseous makeup nitrogen, be subjected to the compression and cooling steps mentioned.
  • liquid nitrogen used for cooling the head condenser be provided from a source of liquid nitrogen external to the first rectification column, either as the sole liquid nitrogen source, or in addition to another liquid nitrogen source, e.g. the above compression cooling cycle.
  • a purge liquid is withdrawn from the evaporation space of a condenser-evaporator in a distillation column system for nitrogen-oxygen separation and the liquid feed mixture is provided using such purge liquid.
  • Such providing of the liquid feed mixture may be realized by a direct introduction, possibly through a purification step into the rectifications system, or by using a liquid tank as described above.
  • the "distillation column system for nitrogen-oxygen separation" may be a classical double-column unit, the evaporation space of the main condenser being the source for the feed mixture.
  • the ASU may be a single-column plant for nitrogen production having a top condenser, the feed mixture originating from evaporation space such top condenser.
  • the single-column plant may have a recycling of the gaseous fraction from the evaporation space of the top condenser to the single column, in particular by a cold compressor, in particular driven by a waste gas turbine (SPECTRATM plant, see e.g. EP 412793 B1 , EP 773417 B1 , US 2007204652 , US 2008289362 A1 , US 2009120128 A1 , US 2009107177 A1 , US 2010242537 A1 , EP 2662653 A1 , US 10209004 B2).
  • SPECTRATM plant see e.g. EP 412793 B1 , EP 773417 B1 , US 2007204652 , US 2008289362 A1 , US 2009120128 A1 , US 2009107177 A1 , US 2010242537 A1 , EP 2662653 A1 , US 10209004 B2).
  • the first fraction enriched in krypton and xenon is transported to a downstream separation unit for further enrichment of krypton and xenon not enclosed by the coldbox of the krypton-xenon rectification column arrangement.
  • the transport may be performed continuously by a pipeline or intermittently by tank vehicles, depending on the distance between krypton-xenon rectification system and downstream separation unit.
  • An apparatus for producing air products is also provided, the apparatus being adapted to perform the steps of providing a liquid feed mixture comprising 1 to 10 ppm by volume krypton, 0.1 to 1 ppm by volume xenon, and 99 to 99.9 % by volume oxygen, and subjecting the liquid feed mixture or a part thereof to a rectification providing a first fraction depleted in oxygen and enriched in krypton and xenon relative to the feed mixture and a second fraction enriched in oxygen and depleted in krypton and xenon relative to the feed mixture.
  • the apparatus is adapted to withdraw the first fraction and the second fraction from a rectification column used in the rectification in liquid form, introduce the liquid feed mixture or the part thereof subjected to the rectification with a proportion of liquid of 90% or more into the rectification column, and make up a total feed to the rectification column to at least 90% by the liquid feed mixture or the part thereof subjected to the rectification.
  • such an apparatus may comprise means adapted to perform a method according to any of the embodiments of the present invention.
  • Figure 1 illustrates a unit for processing of a mixture containing krypton, xenon and oxygen in a configuration not usable according to an embodiment of the present invention.
  • Figure 2 illustrates a unit for processing of a mixture containing krypton, xenon and oxygen in a configuration not usable according to an embodiment of the present invention.
  • FIG. 3 illustrates another embodiment which is outside the present invention.
  • Figure 4 shows an embodiment of the present invention having a split feed line and a single integrated heat exchanger.
  • Krypton and xenon production based on cryogenic air separation may be performed in three sub-units or steps which are often referred to as C1 , C2 and C3.
  • the C1 unit or step is typically a part of, or performed in, an air separation unit as described at the outset and it produces so-called crude krypton/xenon which has comparatively low concentrations of krypton and xenon and contains about 99.3% oxygen.
  • Crude krypton/xenon from several air separation units may be collected and transported to the C2 unit or step, in which a purification is performed, mainly by removing the oxygen.
  • the product of the C2 unit or step is essentially a krypton/xenon mixture with traces of impurities.
  • FIG. 1 illustrates an apparatus 10 which may be used as a C1 unit or in a C1 step. More generally, the apparatus 10 illustrated in Figure 1 may be used in connection with producing air products, particularly including a krypton/xenon mixture and oxygen from liquid oxygen which is withdrawn from a sump of a low pressure column of an air separation unit or a comparable liquid in cryogenic state.
  • Apparatus 10 comprises a cryogenic storage tank 11 which may be supplied with cryogenic liquid 9 from one or more air separation units, e.g. by tank trucks. Such a liquid 9 may be withdrawn from the cryogenic storage tank 11 using a pump 12. and provides a liquid feed mixture 1 .
  • a rectification column arrangement 14 which comprises, in the embodiment illustrated in Figure 1 , a single rectification column 141 , is part of apparatus 10 and is adapted to perform a rectification providing a first fraction 2 depleted in oxygen and enriched in krypton and xenon relative to the feed mixture 1 , which may be supplied to a C2 unit as may be known to the skilled person, or any other subsequent processing step or steps, and a second fraction 3 enriched in oxygen and depleted in krypton and xenon relative to the feed mixture 1 .
  • Second fraction 3 may essentially consist of oxygen and some impurities already mentioned above.
  • the first fraction 2 and the second fraction 3 are withdrawn from the rectification column arrangement 14, i.e. from the rectification column 141 , in liquid form, the liquid feed mixture 1 or the part thereof subjected to the rectification is introduced with a proportion of liquid of 90% or more into the rectification column arrangement 14, and a total feed to the rectification column arrangement 14 is made up to at least 90% by the liquid feed mixture 1 or the part thereof subjected to the rectification. Particularly, only liquid in form of the feed mixture 1 is introduced into rectification column arrangement 14, and liquid oxygen is withdrawn at an upper position in form of the second fraction 3.
  • the rectification column 141 of the rectification column arrangement 14 comprises a sump evaporator 141 a and a head condenser 141b, wherein the sump evaporator 141 a is heated using gaseous nitrogen 4 and wherein the head condenser 141b is cooled using liquid nitrogen 5 which both, in parts, are provided from external source in the example illustrated.
  • the gaseous nitrogen used for heating the sump evaporator 141 a is, in the example shown, after having been used for heating the sump evaporator 141 a, at least in part expanded into the head condenser 141b to form a part of the liquid nitrogen used for cooling the head condenser 141b.
  • the gaseous nitrogen 4 used for heating the sump evaporator 141 a is at least in part subjected to a compression step in a compression unit 17 and a cooling step in counterstream heat exchangers 16 and 15 before being used for heating the sump evaporator 141 a.
  • Gaseous nitrogen is withdrawn from the head condenser 141 b and used at least in part used as the gaseous nitrogen used for heating the sump evaporator 141 a, i.e. it is, in the example shown, combined with the gaseous nitrogen 4 from the external source and compressed and cooled together therewith as shown for a stream 8.
  • a part may also be vented to the atmosphere or used otherwise, as shown for a fraction 6 in Figure 1 .
  • Coldbox 300 is schematically shown in Figure 1 as a dotted line. It encloses all cold parts of the krypton-xenon rectification system. It encloses a single column, the rectification column 141 and other cold parts like condenser-evaporators 141a, 141 b and gas-gas or liquid-liquid heat exchangers 15, 16.
  • the coldbox 300 does not enclose further separation columns not being part of the krypton-xenon rectification system, in particular not a column of a main plant like an air separation plant for nitrogen-oxygen separation, in particular not a column of the air separation unit, the feed mixture may come from.
  • the krypton-xenon rectification system is retrofit-ready, i.e. it can be added to an existing tank or air separation unit without opening the insulation of the tank or the ASU.
  • FIG 2 an apparatus 20 is illustrated which can be used for essentially the same purposes as the apparatus 10 according to Figure 1 .
  • Some of the elements, which may have essentially the same or a comparable function and configuration, are not again described for reasons of clarity.
  • storage tank 11 which is illustrated in Figure 1 is not illustrated in Figure 2.
  • Apparatus 20 according to Figure 2 comprises a rectification column arrangement 14 which, however, comprises two rectification columns 141 and 142.
  • Rectification column 141 may essentially be provided as described before in connection with apparatus 10 shown in Figure 1 .
  • Rectification column 142 may be provided to further treat sump liquid of rectification column 141 .
  • adsorption unit 13 of apparatus 20 shown in Figure 2 is arranged at a different position to treat the sump liquid of rectification column 141 fed into rectification column 142.
  • a side stream of the gaseous nitrogen 4 is used to heat a sump evaporator 142a of rectification column 142, forming a condensate which is also expanded into head condenser 141b of rectification column 141 .
  • the columns of the rectification column arrangement (14) of all embodiments may have an inlet for gaseous oxygen in order to introduce gases losses from a tank or a filling process for transporting one or more products, in particular products from the rectification column arrangement.
  • Coldbox 300 is schematically shown in Figure 2 as a dotted line. It encloses all cold parts of the krypton-xenon rectification system. It encloses a single column, the rectification column 141 and other cold parts like condenser-evaporators 141a, 141 b and gas-gas or liquid-liquid heat exchangers 15, 16.
  • the coldbox 300 does not enclose further separation columns not being part of the krypton-xenon rectification system, in particular not a column of a main plant like an air separation plant for nitrogen-oxygen separation, in particular not a column of the air separation unit, the feed mixture may come from.
  • the krypton-xenon rectification system is retrofit-ready, i.e.
  • FIG 3 an apparatus, and a process is illustrated which can be used for essentially the same purposes as those shown in Figures 1 and 2.
  • Figure 2 it comprises two separation columns 141 , 143, having, however, a slightly different operating regime.
  • Liquid oxygen 9 containing krypton and xenon is supplied from a cryogenic storage tank or one or more air separation units, in particular by impure LOX (LOX imp) having an oxygen concentration of less than 99.5 mol-%, in particular 70 to 90 mol-% and into a coldbox 300.
  • a least a portion of the mixture 9 may be subcooled in a nitrogen heat exchanger 316.
  • the subcooled feed mixture 309 is purified in adsorption unit 13, having two switchable vessels in this example.
  • the purified liquid constitutes a liquid feed mixture 1 to a rectification column arrangement 14 comprising a first column 141 for krypton-xenon concentration and a second column 143 for high-purity oxygen production.
  • the second column (upper column) is specifically used to separate oxygen from other (lighter) gases such as nitrogen, argon, hydrogen and/or carbon monoxide.
  • Those two columns 141/143 are arranged one above the other according to a classical double column, the top condenser of the lower column 141 simultaneously operating as bottom reboiler of the upper column 143.
  • Those two columns 141 , 143 are the only separation columns in the krypton-xenon rectification system of this embodiment.
  • the coldbox 300 does not contain any further column, in particular no separation column fur nitrogen-oxygen separation.
  • the rectification column arrangement 14 is adapted to perform a rectification providing a first fraction 2 depleted in oxygen and enriched in krypton and xenon relative to the feed mixture 1 , which may be supplied to a C2 unit as may be known to the skilled person, or any other subsequent processing step or steps, and a second fraction 3 enriched in oxygen and depleted in krypton and xenon relative to the feed mixture 1 .
  • Second fraction 3 may essentially consist of oxygen and some impurities already mentioned above.
  • the first fraction 2 and the second fraction 3 are withdrawn from the rectification column arrangement 14, i.e. from the rectification columns 141 resp. 143, in liquid form, the liquid feed mixture 1 or the part thereof subjected to the rectification is introduced with a proportion of liquid of 90% or more into the rectification column arrangement 14, and a total feed to the rectification column arrangement 14 is made up to at least 90% by the liquid feed mixture 1 or the part thereof subjected to the rectification. Particularly, only liquid in form of the feed mixture 1 is introduced into rectification column arrangement 14, and liquid oxygen is withdrawn at an upper position in form of the second fraction 3.
  • the rectification column 141 of the rectification column arrangement 14 comprises a sump evaporator (bottom reboiler) 141 a and a head condenser (top condenser) 141 b, wherein the sump evaporator 141a is heated using gaseous nitrogen 4 and wherein the head condenser 141b is cooled using liquid oxygen collecting in the bottom of the second column 143.
  • top condenser 141b works as bottom reboiler of the second column 143 as well.
  • the gaseous nitrogen used for heating the sump evaporator 141a is, in the example shown, after having been used for heating the sump evaporator 141a and thereby liquefied, at least in part expanded into the top condenser 143b of the second column 143 to form a part of the liquid nitrogen used for cooling the head condenser 141b. Before expansion, it may be subcooled in the nitrogen heat exchanger 316.
  • the gaseous nitrogen 4 is supplied from a pressurized nitrogen pipeline 320 (PGAN pipeline). (Alternatively, it may be taken pressureless and then compressed in a nitrogen compressor - not shown in the drawing.
  • the low pressure nitrogen from the reboiler/condenser cycle in the coldbox can be “recycled” to the feed of the compressor (recycle compressor) to reduce the required amount of nitrogen from the pipeline.)
  • a first portion 322 of the gaseous nitrogen 321 is cooled in the nitrogen heat exchanger 316 and taken as the heating medium 4 for the bottom reboiler 141 a.
  • a second portion 323 is used for regenerating the adsorption unit 13.
  • Gaseous nitrogen is withdrawn from the head condenser 143b, fully warmed in the nitrogen heat exchanger 316 and rejected, e.g. vented to the atmosphere or used otherwise.
  • a nitrogen recycle as in Figures 1 or 2 could be used for heating and cooling evaporator-condenser 141a and 143b.
  • the feed mixture to the second column 143 is provided by the top fraction of the lower column 325 after liquefaction in the condenser-evaporator 141b.
  • a non-condensed portion 326 of the top fraction of the upper column 143 is taken as oxygen-rich waste gas, fully warmed in the nitrogen heat exchanger 316 and rejected, e.g. vented to the atmosphere or used otherwise.
  • a small amount of liquid 327 is withdrawn from the top condenser 143b as a purge fraction.
  • Addition liquid nitrogen (PLIN) 328 may be introduced as a cooling medium into the top condenser 413b; it may be taken from a liquid storage tank.
  • Coldbox 300 is schematically shown in Figure 3 as a dotted line. It encloses all cold parts of the krypton-xenon rectification system. It encloses a single column, the rectification columns 141 and 143 and other cold parts like condenser-evaporators 141 a, 141 b, 143b and gas-gas and heat exchanger 316 without phase changes.
  • the coldbox 300 does not enclose further separation columns not being part of the kryptonxenon rectification system, in particular not a column of a main plant like an air separation plant for nitrogen-oxygen separation, in particular not a column of the air separation unit, the feed mixture may come from.
  • the krypton-xenon rectification system is retrofit-ready, i.e., it can be added to an existing tank or air separation unit without opening the insulation of the tank or the ASU.
  • Figure 4 is an embodiment of the invention and has two major differences over Figure 1 .
  • the liquid feed mixture 1 is split into a first portion 1 A and a second portion 1 B before being introduced into the single rectification column 141.
  • the first portion 1 A is fed to the top of the column like in Figure 1
  • the second portion is introduced into the bottom of column 141 .
  • This configuration improves recovery of Krypton.
  • the two heat exchangers 15, 16 of Figure 1 are integrated into a single heat exchanger 15A.
  • liquid nitrogen drawn from storage tank 400 is directly pumped through the single integrated heat exchanger 15A to subcool the second fraction 3 and provide the cold needed for driving the rectification column 141 ; unlike in Figure 1 pumping through heat exchanger 15 to subcool the second fraction 3, and then to top condenser 141 b to provide the cold.
  • the first fraction 2 and the second fraction 3 are like in Figure 1 withdrawn from the rectification column arrangement, i.e. from the single rectification column 141 , in liquid form.
  • the second fraction 3 is subcooled in integrated heat exchanger 15A and introduced into liquid tank 403.
  • Liquid nitrogen is taken from storage tank 400, pumped in pump 401 and warmed in the same integrated heat exchanger 15A.

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Abstract

In a method and an apparatus for producing air products comprising the steps of a liquid feed mixture (1) comprising krypton, xenon and more than 50 mol-% oxygen is provided. The liquid feed mixture (1) is subjected to a rectification in a krypton-xenon rectification system having a single rectification column (141) and providing a first fraction (2) depleted in oxygen and enriched in krypton and xenon relative to the feed mixture (1) and a second fraction (3) enriched in oxygen and depleted in krypton and xenon relative to the feed mixture (1). The first fraction (2) and the second fraction (3) are withdrawn from the krypton-xenon rectification system comprising a rectification column arrangement (14), the rectification column arrangement (14) being arranged in a coldbox (300) that does not contain further separation columns not being part of the krypton-xenon rectification system.

Description

Description
Method and apparatus for producing air products from an oxygen fraction
The present invention relates to a method and to an apparatus for producing air products, particularly including a krypton/xenon mixture and oxygen.
Field of the invention
The production of air products in liquid or gaseous state by cryogenic separation of air in air separation units is well known and described, for example, in H.-W. Haring (ed.), Industrial Gases Processing, Wiley-VCH, 3006, especially sections 2.2.5, “Cryogenic Rectification” and 3.3 "Recovery of Krypton and Xenon". Unless expressly defined otherwise, the terms used below have the meanings customary in the technical literature.
The noble gases krypton and xenon, which are contained in atmospheric air at concentrations of about 1 ppm and about 0.09 ppm can be obtained by processing considerable amounts of air in air separation units. The boiling temperatures of krypton and xenon are well above the boiling temperatures of nitrogen and oxygen. The task of producing krypton and/or xenon products includes an enrichment to obtain a krypton/xenon mixture and separating said mixture as further explained below.
It is an object of the present invention to improve the processing of mixtures particularly including a krypton/xenon mixture and oxygen, particularly to provide additional or improved air products. According to prior art, that is done by a krypton-xenon enrichment column integrated in the main air separation plant for separating nitrogen and oxygen. Such enrichment column is, however, not installed in about 95 % of the existing air separation units. Therefore, they cannot be used for the production of krypton and xenon. The direct oxygen product (upstream a possible krypton-xenon enrichment column) contains only traces of krypton, which is not profitable to be transported to a separate krypton-xenon recovery unit.
In prior art, adding a krypton-xenon recovery to an air separation plant not yet having a krypton-xenon enrichment column by means would require opening the coldbox of the plant and other heavy intrusions into the original installation. Such steps would require months of shut-down of the main air separation plant meaning large production losses. Such shut-down is typically not acceptable to the customer. The invention seeks for a possibility to add a krypton-xenon recovery with moderate effort to an existing air separation which was previously not adapted for krypton-xenon recovery plant, in particular with minimum or no shut-down time of the main plant.
Summary of the invention
Against this background, the present invention provides a method and an apparatus for producing air products, particularly including a krypton/xenon mixture and oxygen, comprising the features of the independent claims, such features being able to be connected to an existing air separation plant without changing the air separation plant itself and providing an enrichment of krypton and xenon which is worth to be transported to a separate krypton-xenon enrichment unit. Embodiments are subject of the dependent claims and of the explanations that follow hereinbelow.
In the invention, a method for producing air products comprising the step of providing a liquid oxygen feed mixture is proposed. Other systems may be operated by a gaseous oxygen feed mixture. In the invention, for example, the liquid feed mixture may comprise:
Krypton
- less than 120 ppm
- preferably less than 50 ppm
- more preferably 1 to 50 ppm
Xenon
- less than 15 ppm
- preferably less than 10 ppm
- more preferably 0.3 to 10 ppm
Most of the remainder of the feed mixture is usually oxygen. The invention works with oxygen concentrations in the feed mixture of more than 50 mol-%. Preferably the feed mixture comprises more than 90 mol-%, more preferably more than 98 mol-%, even more preferably more than 98 mol-%, for example 98 to 99.9 mol-% oxygen. The liquid feed mixture or a part thereof is subjected to a rectification providing a first fraction depleted in oxygen and enriched in krypton and xenon relative to the feed mixture and a second fraction enriched in oxygen and depleted in krypton and xenon relative to the feed mixture.
The first fraction and the second fraction are withdrawn from a rectification column arrangement used in the rectification in liquid form, the liquid feed mixture or the part thereof subjected to the rectification is introduced with a proportion of liquid of 90% or more, particularly of 95% or more or 99% or more, particularly in an essentially liquid form, into the rectification column arrangement, and a total feed to the rectification column arrangement is made up to at least 90%, particularly of at least 95% or 99%, particularly essentially completely, by the liquid feed mixture or the part thereof subjected to the rectification.
The feed mixture will be in liquid state. Firstly, such a liquid is easier to transport and to store than a gas; secondly it can be directly used as a reflux liquid in the krypton-xenon rectification system.
In the invention, the rectification system for krypton-xenon has its own coldbox, enclosing the column(s) of such rectification system only and no other separation columns, in particular not of the main air separation plant for nitrogen-oxygen separation. Such coldbox may, however, enclose other parts of the rectification system like heat exchangers, pipelines, valves and/or possibly other cold parts, e.g. a cryogenic adsorption system. Thus, the krypton-xenon rectification system of the invention is retrofit-ready, i.e. it can be added to an existing tank or air separation unit without opening the insulation of the tank or the ASU.
A "coldbox" is an insulating enclosure having walls normally made of metal sheets and having an insulation in the walls (e.g. vacuum insulation) or at the inner surface of the walls or by filling its interior (outside the apparatus parts themselves) with powder or granulate material like perlite. The insulation methods mentioned may, of course be combined. Terms such as “essentially comprising”, “essentially consisting of”, etc., when used herein to describe constituents of a composition, fluid, stream, etc., shall indicate that, in addition to one or more specified constituents, one or more further constituents may be present in the composition, fluid, stream, etc., but that the essential features of the composition, stream, etc., in terms of at least one of physical properties, chemical properties, reactivity in one or more reaction units, treatability in one or more treatment units, compatibility with one or more materials, etc., are not significantly, not practically, or neglectably changed by the one or more further constituents. In this connection, the one or more specified constituents may make up at least 90%, particularly at least 95%, 99%, 99.9%, 99.99% or 99.999% of the composition, stream, etc. Terms such as “essentially free from”, etc., may refer to one or more constituents being present in a composition, fluid, stream, etc., in minor amounts which likewise do not influence the essential features referred to above, such as in amounts of less than 10%, 5%, 1%, 0.1%, 0.01% or 0.001%.
Similarly, a reference to a composition, fluid, stream, etc., being made up from, or being formed by, etc., “essentially” one or more other compositions, fluids, streams, etc., shall indicate that such a composition, fluid, stream, etc., may also include parts from other sources, i.e., compositions, fluids, streams, etc., but that these generally only contribute to a small part to the overall amount. That is, the one or more compositions, fluids, streams, etc., specified as being made up from, or being formed by, “essentially” one or more specified compositions, fluids, streams, etc., may be provided from the one or more specified compositions, fluids, streams, etc., by at least 90%, particularly at least 95% or 99%. All percentage values indicated herein, if not otherwise indicated or excluded by the technical understanding of the skilled person, may refer to volume, weight, mass, or molar proportions.
In an embodiment of the present invention, the liquid feed mixture comprises 4 to 7 or 5 to 6 ppm by volume krypton, 0.2 to 0.6 or 0.3 to 0.5 ppm by volume xenon, and 99.5 to 99.9 % by volume oxygen. Embodiments of the present invention may therefore be used for treating liquid oxygen withdrawn from the sump of a low-pressure column of an air separation unit as generally known from the prior art.
In an embodiment of the present invention, the liquid feed mixture is provided using a liquid withdrawn from a cryogenic storage tank. This advantageously allows for collecting such liquid from one or more air separation units. The storage tank may be the usual liquid oxygen product and/or backup tank which belongs to an air separation plant or a set of air separation plants.
According to an embodiment of the present invention, the liquid withdrawn from the cryogenic storage tank comprises one or more hydrocarbons and providing the liquid feed mixture comprises removing at least a part of the hydrocarbons from the liquid withdrawn from the cryogenic storage tank. Removal of hydrocarbons may be performed upstream the rectification column arrangement using methods as known in the prior art which may be adapted to the proposed process if necessary, according to the understanding of the skilled person.
An embodiment of the present invention includes that the liquid withdrawn from the cryogenic storage tank is at least in part made up by a liquid produced in one or more air separation units and stored in the cryogenic storage tank, as mentioned.
The cold needed for driving the rectification system is preferably provided by liquid nitrogen e.g. taken from a LIN tank, a nearby nitrogen liquefier or an air separation plant producing liquid nitrogen. Such LIN tank may be filled by a remote source or by an air separation plant that delivers the liquid feed mixture or fills the LOX tank, the liquid feed mixture is taken from. In embodiments of the present invention, the rectification column arrangement comprises a rectification column with sump evaporator and a head condenser. This rectification column is referred to herein as a “first” rectification column at certain places, even if it may be the sole rectification column in the rectification column arrangement. In this embodiment, the sump evaporator may be heated using gaseous nitrogen and/or wherein the head condenser may be cooled using liquid nitrogen. In a preferred embodiment, the same fraction, e.g. nitrogen, is used for both purposes.
Alternatively, the liquid nitrogen is or produced by a recycle attached to the rectification column arrangement and made up by external gaseous nitrogen from a nitrogen pipeline connected to a pipeline network or to a near air separation plant producing pressurized nitrogen. Such air separation plant may or may not be the one delivering the feed mixture. In embodiments of the present invention, the gaseous nitrogen used for heating the sump evaporator is, after having been used for heating the sump evaporator, at least in part expanded into the head condenser, more precisely into an evaporation space thereof, to form a part of the liquid nitrogen used for cooling the head condenser. The gaseous nitrogen used for heating the sump evaporator may be cooled during said heating the sump evaporator to an extent that it is partly or completely liquefied or brought close to the liquefaction temperature at an elevated pressure. Expansion into the head condenser then may cause (further) liquefaction.
The gaseous nitrogen after use for cooling the head condenser may at least in part be subjected to a compression step and a cooling step before being used for heating the sump evaporator. Suitable pressure and temperature levels are used as required to perform a satisfactory separation.
In embodiments of the present invention, a nitrogen cooling cycle may be formed. That is, gaseous nitrogen may be withdrawn from the head condenser, more precisely from an evaporation space thereof, and used at least in part used as the gaseous nitrogen used for heating the sump evaporator. Said gaseous nitrogen withdrawn from the head condenser may, together with gaseous makeup nitrogen, be subjected to the compression and cooling steps mentioned.
In embodiments of the present invention, liquid nitrogen used for cooling the head condenser be provided from a source of liquid nitrogen external to the first rectification column, either as the sole liquid nitrogen source, or in addition to another liquid nitrogen source, e.g. the above compression cooling cycle.
In another embodiment of the invention, a purge liquid is withdrawn from the evaporation space of a condenser-evaporator in a distillation column system for nitrogen-oxygen separation and the liquid feed mixture is provided using such purge liquid. Such providing of the liquid feed mixture may be realized by a direct introduction, possibly through a purification step into the rectifications system, or by using a liquid tank as described above.
The "distillation column system for nitrogen-oxygen separation" (air separation unit, ASU) may be a classical double-column unit, the evaporation space of the main condenser being the source for the feed mixture. Alternatively, the ASU may be a single-column plant for nitrogen production having a top condenser, the feed mixture originating from evaporation space such top condenser. (The term "condenser" is a short form of "condenser-evaporator" in both cases.) The single-column plant may have a recycling of the gaseous fraction from the evaporation space of the top condenser to the single column, in particular by a cold compressor, in particular driven by a waste gas turbine (SPECTRA™ plant, see e.g. EP 412793 B1 , EP 773417 B1 , US 2007204652 , US 2008289362 A1 , US 2009120128 A1 , US 2009107177 A1 , US 2010242537 A1 , EP 2662653 A1 , US 10209004 B2).
In the invention, the first fraction enriched in krypton and xenon is transported to a downstream separation unit for further enrichment of krypton and xenon not enclosed by the coldbox of the krypton-xenon rectification column arrangement. The transport may be performed continuously by a pipeline or intermittently by tank vehicles, depending on the distance between krypton-xenon rectification system and downstream separation unit.
An apparatus for producing air products is also provided, the apparatus being adapted to perform the steps of providing a liquid feed mixture comprising 1 to 10 ppm by volume krypton, 0.1 to 1 ppm by volume xenon, and 99 to 99.9 % by volume oxygen, and subjecting the liquid feed mixture or a part thereof to a rectification providing a first fraction depleted in oxygen and enriched in krypton and xenon relative to the feed mixture and a second fraction enriched in oxygen and depleted in krypton and xenon relative to the feed mixture. The apparatus is adapted to withdraw the first fraction and the second fraction from a rectification column used in the rectification in liquid form, introduce the liquid feed mixture or the part thereof subjected to the rectification with a proportion of liquid of 90% or more into the rectification column, and make up a total feed to the rectification column to at least 90% by the liquid feed mixture or the part thereof subjected to the rectification.
As to further details and advantages of such an apparatus, reference is made to the explanations above in connection with the method according to the present invention and its embodiments. Particularly, such an apparatus provided according to the present invention may comprise means adapted to perform a method according to any of the embodiments of the present invention. Brief description of the Figures
Embodiments of the invention will now be described, by way of example only, with reference to accompanying drawings, in which:
Figure 1 illustrates a unit for processing of a mixture containing krypton, xenon and oxygen in a configuration not usable according to an embodiment of the present invention.
Figure 2 illustrates a unit for processing of a mixture containing krypton, xenon and oxygen in a configuration not usable according to an embodiment of the present invention.
Figure 3 illustrates another embodiment which is outside the present invention.
Figure 4 shows an embodiment of the present invention having a split feed line and a single integrated heat exchanger.
Embodiments in the Drawings
Krypton and xenon production based on cryogenic air separation may be performed in three sub-units or steps which are often referred to as C1 , C2 and C3. The C1 unit or step is typically a part of, or performed in, an air separation unit as described at the outset and it produces so-called crude krypton/xenon which has comparatively low concentrations of krypton and xenon and contains about 99.3% oxygen. Crude krypton/xenon from several air separation units may be collected and transported to the C2 unit or step, in which a purification is performed, mainly by removing the oxygen. The product of the C2 unit or step is essentially a krypton/xenon mixture with traces of impurities. The removed oxygen is conventionally used as a gaseous oxygen product at low pressure. From several C2 units or steps, the krypton/xenon mixture may be passed on to a C3 unit or step to produce pure krypton and xenon. The designation of units or steps as C1 , C2, C3 is not limiting and the present invention can be used with other arrangements of apparatus units or method steps. Figure 1 illustrates an apparatus 10 which may be used as a C1 unit or in a C1 step. More generally, the apparatus 10 illustrated in Figure 1 may be used in connection with producing air products, particularly including a krypton/xenon mixture and oxygen from liquid oxygen which is withdrawn from a sump of a low pressure column of an air separation unit or a comparable liquid in cryogenic state.
Apparatus 10 comprises a cryogenic storage tank 11 which may be supplied with cryogenic liquid 9 from one or more air separation units, e.g. by tank trucks. Such a liquid 9 may be withdrawn from the cryogenic storage tank 11 using a pump 12. and provides a liquid feed mixture 1 .
A rectification column arrangement 14 which comprises, in the embodiment illustrated in Figure 1 , a single rectification column 141 , is part of apparatus 10 and is adapted to perform a rectification providing a first fraction 2 depleted in oxygen and enriched in krypton and xenon relative to the feed mixture 1 , which may be supplied to a C2 unit as may be known to the skilled person, or any other subsequent processing step or steps, and a second fraction 3 enriched in oxygen and depleted in krypton and xenon relative to the feed mixture 1 . Second fraction 3 may essentially consist of oxygen and some impurities already mentioned above.
The first fraction 2 and the second fraction 3 are withdrawn from the rectification column arrangement 14, i.e. from the rectification column 141 , in liquid form, the liquid feed mixture 1 or the part thereof subjected to the rectification is introduced with a proportion of liquid of 90% or more into the rectification column arrangement 14, and a total feed to the rectification column arrangement 14 is made up to at least 90% by the liquid feed mixture 1 or the part thereof subjected to the rectification. Particularly, only liquid in form of the feed mixture 1 is introduced into rectification column arrangement 14, and liquid oxygen is withdrawn at an upper position in form of the second fraction 3.
The rectification column 141 of the rectification column arrangement 14 comprises a sump evaporator 141 a and a head condenser 141b, wherein the sump evaporator 141 a is heated using gaseous nitrogen 4 and wherein the head condenser 141b is cooled using liquid nitrogen 5 which both, in parts, are provided from external source in the example illustrated. The gaseous nitrogen used for heating the sump evaporator 141 a is, in the example shown, after having been used for heating the sump evaporator 141 a, at least in part expanded into the head condenser 141b to form a part of the liquid nitrogen used for cooling the head condenser 141b.
In the example shown, the gaseous nitrogen 4 used for heating the sump evaporator 141 a is at least in part subjected to a compression step in a compression unit 17 and a cooling step in counterstream heat exchangers 16 and 15 before being used for heating the sump evaporator 141 a. Gaseous nitrogen is withdrawn from the head condenser 141 b and used at least in part used as the gaseous nitrogen used for heating the sump evaporator 141 a, i.e. it is, in the example shown, combined with the gaseous nitrogen 4 from the external source and compressed and cooled together therewith as shown for a stream 8. A part may also be vented to the atmosphere or used otherwise, as shown for a fraction 6 in Figure 1 .
Coldbox 300 is schematically shown in Figure 1 as a dotted line. It encloses all cold parts of the krypton-xenon rectification system. It encloses a single column, the rectification column 141 and other cold parts like condenser-evaporators 141a, 141 b and gas-gas or liquid-liquid heat exchangers 15, 16. The coldbox 300 does not enclose further separation columns not being part of the krypton-xenon rectification system, in particular not a column of a main plant like an air separation plant for nitrogen-oxygen separation, in particular not a column of the air separation unit, the feed mixture may come from. Thus, the krypton-xenon rectification system is retrofit-ready, i.e. it can be added to an existing tank or air separation unit without opening the insulation of the tank or the ASU.
In Figure 2, an apparatus 20 is illustrated which can be used for essentially the same purposes as the apparatus 10 according to Figure 1 . Some of the elements, which may have essentially the same or a comparable function and configuration, are not again described for reasons of clarity. For reasons of clarity and generality, furthermore, storage tank 11 which is illustrated in Figure 1 is not illustrated in Figure 2.
Apparatus 20 according to Figure 2 comprises a rectification column arrangement 14 which, however, comprises two rectification columns 141 and 142. Rectification column 141 may essentially be provided as described before in connection with apparatus 10 shown in Figure 1 . Rectification column 142 may be provided to further treat sump liquid of rectification column 141 . Different from what is shown in Figure 1 for apparatus 10, furthermore, adsorption unit 13 of apparatus 20 shown in Figure 2 is arranged at a different position to treat the sump liquid of rectification column 141 fed into rectification column 142. A side stream of the gaseous nitrogen 4 is used to heat a sump evaporator 142a of rectification column 142, forming a condensate which is also expanded into head condenser 141b of rectification column 141 .
The columns of the rectification column arrangement (14) of all embodiments may have an inlet for gaseous oxygen in order to introduce gases losses from a tank or a filling process for transporting one or more products, in particular products from the rectification column arrangement.
The various embodiments described herein are presented only to assist in understanding and teaching the claimed features. These embodiments are provided as a representative sample of embodiments only and are not exhaustive and/or exclusive. It is to be understood that advantages, embodiments, examples, functions, features, structures, and/or other aspects described herein are not to be considered limitations on the scope of the invention as defined by the claims or limitations on equivalents to the claims, and that other embodiments may be utilised, and modifications may be made without departing from the scope of the claimed invention. Various embodiments of the invention may suitably comprise, consist of, or consist essentially of, appropriate combinations of the disclosed elements, components, features, parts, steps, means, etc., other than those specifically described herein. In addition, this disclosure may include other inventions not presently claimed, but which may be claimed in future.
Coldbox 300 is schematically shown in Figure 2 as a dotted line. It encloses all cold parts of the krypton-xenon rectification system. It encloses a single column, the rectification column 141 and other cold parts like condenser-evaporators 141a, 141 b and gas-gas or liquid-liquid heat exchangers 15, 16. The coldbox 300 does not enclose further separation columns not being part of the krypton-xenon rectification system, in particular not a column of a main plant like an air separation plant for nitrogen-oxygen separation, in particular not a column of the air separation unit, the feed mixture may come from. Thus, the krypton-xenon rectification system is retrofit-ready, i.e. it can be added to an existing tank or air separation unit without opening the insulation of the tank or the ASU. In Figure 3, an apparatus, and a process is illustrated which can be used for essentially the same purposes as those shown in Figures 1 and 2. As Figure 2, it comprises two separation columns 141 , 143, having, however, a slightly different operating regime. Some of the elements, which may have essentially the same or a comparable function and configuration, are not again described for reasons of clarity.
Liquid oxygen 9 containing krypton and xenon, is supplied from a cryogenic storage tank or one or more air separation units, in particular by impure LOX (LOX imp) having an oxygen concentration of less than 99.5 mol-%, in particular 70 to 90 mol-% and into a coldbox 300. A least a portion of the mixture 9 may be subcooled in a nitrogen heat exchanger 316. The subcooled feed mixture 309 is purified in adsorption unit 13, having two switchable vessels in this example. The purified liquid constitutes a liquid feed mixture 1 to a rectification column arrangement 14 comprising a first column 141 for krypton-xenon concentration and a second column 143 for high-purity oxygen production. The second column (upper column) is specifically used to separate oxygen from other (lighter) gases such as nitrogen, argon, hydrogen and/or carbon monoxide. Those two columns 141/143 are arranged one above the other according to a classical double column, the top condenser of the lower column 141 simultaneously operating as bottom reboiler of the upper column 143. Those two columns 141 , 143 are the only separation columns in the krypton-xenon rectification system of this embodiment. The coldbox 300 does not contain any further column, in particular no separation column fur nitrogen-oxygen separation.
The rectification column arrangement 14 is adapted to perform a rectification providing a first fraction 2 depleted in oxygen and enriched in krypton and xenon relative to the feed mixture 1 , which may be supplied to a C2 unit as may be known to the skilled person, or any other subsequent processing step or steps, and a second fraction 3 enriched in oxygen and depleted in krypton and xenon relative to the feed mixture 1 . Second fraction 3 may essentially consist of oxygen and some impurities already mentioned above.
The first fraction 2 and the second fraction 3 are withdrawn from the rectification column arrangement 14, i.e. from the rectification columns 141 resp. 143, in liquid form, the liquid feed mixture 1 or the part thereof subjected to the rectification is introduced with a proportion of liquid of 90% or more into the rectification column arrangement 14, and a total feed to the rectification column arrangement 14 is made up to at least 90% by the liquid feed mixture 1 or the part thereof subjected to the rectification. Particularly, only liquid in form of the feed mixture 1 is introduced into rectification column arrangement 14, and liquid oxygen is withdrawn at an upper position in form of the second fraction 3.
The rectification column 141 of the rectification column arrangement 14 comprises a sump evaporator (bottom reboiler) 141 a and a head condenser (top condenser) 141 b, wherein the sump evaporator 141a is heated using gaseous nitrogen 4 and wherein the head condenser 141b is cooled using liquid oxygen collecting in the bottom of the second column 143. Thereby, top condenser 141b works as bottom reboiler of the second column 143 as well. The gaseous nitrogen used for heating the sump evaporator 141a is, in the example shown, after having been used for heating the sump evaporator 141a and thereby liquefied, at least in part expanded into the top condenser 143b of the second column 143 to form a part of the liquid nitrogen used for cooling the head condenser 141b. Before expansion, it may be subcooled in the nitrogen heat exchanger 316.
In the example shown, the gaseous nitrogen 4 is supplied from a pressurized nitrogen pipeline 320 (PGAN pipeline). (Alternatively, it may be taken pressureless and then compressed in a nitrogen compressor - not shown in the drawing. The low pressure nitrogen from the reboiler/condenser cycle in the coldbox can be “recycled” to the feed of the compressor (recycle compressor) to reduce the required amount of nitrogen from the pipeline.) A first portion 322 of the gaseous nitrogen 321 is cooled in the nitrogen heat exchanger 316 and taken as the heating medium 4 for the bottom reboiler 141 a. A second portion 323 is used for regenerating the adsorption unit 13.
Gaseous nitrogen is withdrawn from the head condenser 143b, fully warmed in the nitrogen heat exchanger 316 and rejected, e.g. vented to the atmosphere or used otherwise. (As an Alternative, a nitrogen recycle as in Figures 1 or 2 could be used for heating and cooling evaporator-condenser 141a and 143b.
The feed mixture to the second column 143 is provided by the top fraction of the lower column 325 after liquefaction in the condenser-evaporator 141b. A non-condensed portion 326 of the top fraction of the upper column 143 is taken as oxygen-rich waste gas, fully warmed in the nitrogen heat exchanger 316 and rejected, e.g. vented to the atmosphere or used otherwise. A small amount of liquid 327 is withdrawn from the top condenser 143b as a purge fraction. Addition liquid nitrogen (PLIN) 328 may be introduced as a cooling medium into the top condenser 413b; it may be taken from a liquid storage tank.
Coldbox 300 is schematically shown in Figure 3 as a dotted line. It encloses all cold parts of the krypton-xenon rectification system. It encloses a single column, the rectification columns 141 and 143 and other cold parts like condenser-evaporators 141 a, 141 b, 143b and gas-gas and heat exchanger 316 without phase changes. The coldbox 300 does not enclose further separation columns not being part of the kryptonxenon rectification system, in particular not a column of a main plant like an air separation plant for nitrogen-oxygen separation, in particular not a column of the air separation unit, the feed mixture may come from. Thus, the krypton-xenon rectification system is retrofit-ready, i.e., it can be added to an existing tank or air separation unit without opening the insulation of the tank or the ASU.
Figure 4 is an embodiment of the invention and has two major differences over Figure 1 . Firstly, the liquid feed mixture 1 is split into a first portion 1 A and a second portion 1 B before being introduced into the single rectification column 141. The first portion 1 A is fed to the top of the column like in Figure 1 , the second portion is introduced into the bottom of column 141 . This configuration improves recovery of Krypton. As a second main difference, the two heat exchangers 15, 16 of Figure 1 are integrated into a single heat exchanger 15A.
As a further important main difference, liquid nitrogen drawn from storage tank 400 is directly pumped through the single integrated heat exchanger 15A to subcool the second fraction 3 and provide the cold needed for driving the rectification column 141 ; unlike in Figure 1 pumping through heat exchanger 15 to subcool the second fraction 3, and then to top condenser 141 b to provide the cold.
The first fraction 2 and the second fraction 3 are like in Figure 1 withdrawn from the rectification column arrangement, i.e. from the single rectification column 141 , in liquid form. The second fraction 3 is subcooled in integrated heat exchanger 15A and introduced into liquid tank 403. Liquid nitrogen is taken from storage tank 400, pumped in pump 401 and warmed in the same integrated heat exchanger 15A.
5

Claims

Patent Claims
1 . A method for producing air products comprising the steps of
- providing a liquid feed mixture (1) comprising krypton, xenon and more than 50 mol-% oxygen and
- subjecting the liquid feed mixture (1 ) or a part thereof to a rectification in a krypton-xenon rectification system providing a first fraction (2) depleted in oxygen and enriched in krypton and xenon relative to the feed mixture (1 ) and a second fraction (3) enriched in oxygen and depleted in krypton and xenon relative to the feed mixture (1), whereby
- the first fraction (2) and the second fraction (3) are withdrawn from the kryptonxenon rectification system comprising a rectification column arrangement (14), the rectification column arrangement (14) being arranged in a coldbox (300) that does not contain further separation columns not being part of the krypton-xenon rectification system, characterized in that
- the krypton-xenon rectification system comprises a single rectification column
(141 ),
- the liquid feed mixture (1 ) is split into a first portion (1A) and a second portion (1 B) before being introduced into the single rectification column (141 ),
- the first portion (1A) is fed to the top of the single rectification column (141 ) and
- the second portion (1 B) is introduced into the bottom of the single rectification column (141 ).
2. A method according to claim 1 , wherein the single rectification column (141 ) rectification column arrangement (14) comprises a sump evaporator (141 a) and a head condenser (141 b).
3. A method according to claim 2, wherein the sump evaporator (141a) is heated using gaseous nitrogen (4).
4. A method according to claim 3, wherein the head condenser (141 b) is cooled using liquid nitrogen (5), the gaseous nitrogen used for heating the sump evaporator (141 a) is, after having been used for heating the sump evaporator (141 a), at least in part expanded into the head condenser (141 b) to cool the head condenser (141 b).
5. A method according claim 3 or 4, wherein the gaseous nitrogen (4) is cooled in an integrated multi-stream heat exchanger (15A) before being used for heating the sump evaporator 141 a.
6. A method according claim 5, wherein gaseous nitrogen withdrawn from the top condenser 141 b is warmed in the integrated multi-stream heat exchanger (15A).
7. The method according to any of claims 4 to 6, wherein the gaseous nitrogen (4) used for cooling the head condenser (141b) is at least in part subjected to a compression step and a cooling step before being used for heating the sump evaporator (141a).
8. The method according to any of the preceding claims, wherein the liquid feed mixture (1) is provided using a liquid withdrawn from a cryogenic storage tank (11 ).
9. The method according to claim 8, wherein the liquid withdrawn from the cryogenic storage tank (11 ) is at least in part made up by a liquid produced in one or more air separation units and delivered via an oxygen product line to the cryogenic storage tank (11 ), the oxygen product line and the line for the feed mixture being the only flow connection between the one or more air separation units and the rectification system.
10. The method according to any of the preceding claims, wherein a purge liquid is withdrawn from the evaporation space of a condenser-evaporator in a distillation column system for nitrogen-oxygen or argon-oxygen separation and the liquid feed mixture (1 ) is provided using such purge liquid.
11 . The method according to any of the preceding claims, wherein the first fraction (2) enriched in krypton and xenon is transported to a downstream separation unit for further enrichment of krypton and xenon which is not enclosed by the coldbox (300) of the krypton-xenon rectification column arrangement (14). 12. The method according to any one of the preceding claims, wherein the liquid feed mixture (1 ) comprises at most 99.9 % by volume oxygen.
13. An apparatus (10, 20) for producing air products, the apparatus (10, 20) being adapted to perform the steps of
- providing a liquid feed mixture (1 ) comprising krypton, xenon and more than 50 mol-% oxygen and
- subjecting the liquid feed mixture (1 ) or a part thereof to a krypton-xenon rectification system providing a first fraction (2) depleted in oxygen and enriched in krypton and xenon relative to the feed mixture (1 ) and a second fraction (3) enriched in oxygen and depleted in krypton and xenon relative to the feed mixture (1 ), the apparatus (10) being adapted to
- withdraw the first fraction (2) and the second fraction (3) from the kryptonxenon rectification system comprising a rectification column arrangement (14) used in the rectification in liquid form, the rectification column arrangement (14) being arranged in a coldbox (300) that does not contain further separation columns not being part of the kryptonxenon rectification system characterized in that
- the krypton-xenon rectification system comprises a single rectification column
(141 ), and a single integrated heat exchanger 15A,
- means to split the liquid feed mixture (1 ) into a first portion (1 A) and a second portion (1 B) before being introduced into the single rectification column (141 ),
- means for feeding the first portion (1 A) to the top of the single rectification column (141 ), and
- means for introducing the second portion (1 B) into the bottom of the single rectification column (141.
14. An apparatus according to claim 13, wherein the krypton-xenon rectification system comprises a single integrated heat exchanger (15A).
15. An apparatus according to claim 14 having means for drawing liquid nitrogen from storage tank (400) and pumping (401 ) through the single integrated heat exchanger (15A) to subcool the second fraction (3) and provide the cold needed for driving the rectification column (141 ).
PCT/EP2024/025179 2023-06-15 2024-06-05 Method and apparatus for producing air products from an oxygen fraction Ceased WO2024256036A1 (en)

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