Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B23/00—Noble gases; Compounds thereof
  • C01B23/001—Purification or separation processes of noble gases
  • C01B23/0015—Chemical processing only
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
  • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
  • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
  • F25J3/04642—Recovering noble gases from air
  • F25J3/04745—Krypton and/or Xenon
  • F25J3/04751—Producing pure krypton and/or xenon recovered from a crude krypton/xenon mixture
  • F25J3/04757—Producing pure krypton and/or xenon recovered from a crude krypton/xenon mixture using a hybrid system, e.g. using adsorption, permeation or catalytic reaction
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B2210/00—Purification or separation of specific gases
  • C01B2210/0043—Impurity removed
  • C01B2210/005—Carbon monoxide
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B2210/00—Purification or separation of specific gases
  • C01B2210/0043—Impurity removed
  • C01B2210/0051—Carbon dioxide
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B2210/00—Purification or separation of specific gases
  • C01B2210/0043—Impurity removed
  • C01B2210/0068—Organic compounds
• • 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
  • F25J2205/00—Processes or apparatus using other separation and/or other processing means
  • F25J2205/82—Processes or apparatus using other separation and/or other processing means using a reactor with combustion or catalytic reaction

Definitions

• the invention relates to a process for obtaining krypton and/or xenon by cryogenic separation of air, in which krypton and xenon are enriched to form a krypton/xenon concentrate and krypton and/or xenon are obtained from the krypton/xenon concentrate by means of distillation.
• cryogenic separation of air in general as well as the structure of rectification systems for nitrogen/oxygen separation in particular are described in the monograph “Tieftemperaturtechnik” [cryogenic engineering] by Hausen/Linde (2nd Edition, 1985) and in an article by Latimer in Chemical Engineering Progress (Vol. 63, No. 2, 1967, page 35).
• the high-pressure column is operated at a higher pressure than the low-pressure column; the two columns preferably exchange heat with one another, for example via a main condenser, in which top gas of the high-pressure column is liquefied against evaporating bottom liquid of the low-pressure column.
• the rectification system of the invention may be designed as a conventional double column system or alternatively as a three-column system or a system comprising even more than three columns.
• the columns for nitrogen/oxygen separation it is also possible for there to be further apparatuses for obtaining other air constituents, in particular noble gases, for example argon recovery.
• krypton/xenon concentrate contains several hundred vppm of hydrocarbons, CO 2 , N 2 O and traces of fluorine-containing components, such as for example CF 4 , SF 6 and C 2 F 6 .
• some halogenated compounds constitute disruptive impurities which are difficult to separate off.
• the fully fluorinated compounds are highly inert and can only be broken down at very high temperatures.
• the feed air of which is purified in molecular sieve adsorbers in principle only those halogenated compounds which can also pass through the molecular sieve adsorbers as constituents of the feed air pass into the bottom oxygen.
• the primary purpose of the molecular sieve adsorbers is to remove CO 2 and H 2 O from the feed air.
• NF 3 , CClF 3 and C 3 F 8 have also been proven to break through an adsorber filled with the molecular sieve 13X, which is regularly used for air purification, even before CO 2 . They therefore represent possible impurities in the krypton/xenon concentrate.
• the krypton/xenon concentrate produced in the bottom oxygen of the cryogenic air separation unit can be separated in situ in further process steps to form pure krypton and/or xenon. Alternatively, it is stored, for example in a liquid tank, and processed further elsewhere.
• the krypton/xenon concentrate is generally evaporated and reacted at approximately 500° C. over a catalyst which contains platinum or palladium and on which methane is completely burnt to form CO 2 and H 2 O, and in addition N 2 O is broken down to form nitrogen and oxygen. Only a small proportion of the fluorine-containing compounds are reacted. CO 2 and moisture are removed from the resulting gas in molecular sieve adsorbers, and the gas is then fed to cryogenic separation, where krypton and/or xenon have to be separated not only from oxygen, argon and nitrogen, by distillation, but also from the abovementioned fluorinated compounds. The latter constitutes a particularly high level of outlay.
• the invention is based on the object of realizing the removal of halogen compounds in a particularly economical way.
• krypton/xenon concentrate is passed over a bed which contains a catalyst based on a transition metal oxide, in particular based on TiO 2 or ZrO 2 and in which at least one fully halogenated compound, in particular at least one fully fluorinated compound, is reacted.
• the invention now employs a method of this type to remove fully halogenated compounds from the krypton/xenon concentrate.
• TiO 2 and ZrO 2 are chemically inert with respect to the HF formed during the reaction.
• methane contained in the krypton/xenon concentrate to form CO 2 and H 2 O; moreover, N 2 O is broken down into N 2 and O 2 .
• the catalyst bed can be used instead of or in addition to the catalyst bed which has hitherto been customary for the conversion of methane. If it is used in addition to the previously customary catalyst bed, the krypton/xenon concentrate is, for example, first of all passed, at approximately 400 to 500° C., over a material containing platinum and/or palladium, and is then passed over the transition metal oxide at approximately 750° C.
• the two catalyst beds may be arranged in separate containers or in one common housing.
• the catalyst bed is operated at a temperature of 650° C. or more, in particular of 700° C. or more, typically at approximately 750° C.
• TiO 2 and ZrO 2 can be stabilized in order to be able to perform their role at temperatures from 650° C. to 700° C. (cf. Solid State Technology, July 2001, pages 189-200).
• At least one hydrogen halide, HF and/or HCl is produced.
• the krypton/xenon concentrate Downstream of the catalyst bed, it is preferable for the krypton/xenon concentrate to be fed to a purification stage for removing the hydrogen halide, in particular a water or lye scrub.
• the scrub can also be used to separate off SO 3 ; furthermore, it serves to further cool the gas stream.
• CO 2 is generally also formed during the conversion.
• This component is removed again from the krypton/xenon concentrate by being passed through an adsorption bed downstream of the catalyst bed, as has hitherto already been customary.
• the adsorption bed is preferably located downstream of the purification stage for removing the hydrogen halide.
• the invention also relates to an apparatus for obtaining krypton and/or xenon by cryogenic separation of air according to patent claims 8 to 10 .
• the cryogenic air separation is carried out in a conventional Linde double column which comprises high-pressure column and low-pressure column.
• An oxygen fraction is removed from the bottom of the low-pressure column or the bottom of the crude argon condenser; this fraction also contains all the air components of relatively low volatility and is passed into a krypton/xenon enrichment column.
• a krypton/xenon concentrate is extracted from the bottom of this column, evaporated and fed to a catalyst bed operated at 750° C. After cooling, HF and HCl are removed downstream of the catalyst bed by a water scrub.
• the krypton/xenon concentrate then flows through an adsorption bed, in which water and CO 2 as well as any SO 2 which may have formed from SF 6 are removed.
• the purified krypton/xenon concentrate is fed to a distillation device, in which oxygen, argon and nitrogen are separated off and then a pure krypton product and a pure xenon product are obtained.
• the krypton/xenon concentrate from the double column or the krypton/xenon enrichment column can be collected in a liquid reservoir and transported to a spatially remote preparation plant which includes the catalyst bed according to the invention.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Thermal Sciences (AREA)
• Mechanical Engineering (AREA)
• General Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Separation By Low-Temperature Treatments (AREA)
• Catalysts (AREA)

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• 2005
  • 2005-08-09 DE DE102005037576A patent/DE102005037576A1/de not_active Withdrawn
  • 2005-09-20 EP EP05020457A patent/EP1752417A1/de not_active Withdrawn
• 2006
  • 2006-07-31 JP JP2006207632A patent/JP2007045702A/ja active Pending
  • 2006-08-03 US US11/498,258 patent/US20070033968A1/en not_active Abandoned
  • 2006-08-09 CN CNA2006101148586A patent/CN1911789A/zh active Pending

Patent Citations (12)

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