EP0299364B1 - Process and apparatus for air separation by rectification - Google Patents

Process and apparatus for air separation by rectification Download PDF

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Publication number
EP0299364B1
EP0299364B1 EP88110876A EP88110876A EP0299364B1 EP 0299364 B1 EP0299364 B1 EP 0299364B1 EP 88110876 A EP88110876 A EP 88110876A EP 88110876 A EP88110876 A EP 88110876A EP 0299364 B1 EP0299364 B1 EP 0299364B1
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Prior art keywords
column
nitrogen
rectification
oxygen
purity
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EP88110876A
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German (de)
French (fr)
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EP0299364A3 (en
EP0299364A2 (en
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Dietrich Dipl.-Ing. Rottmann
Horst Dipl.-Ing. Corduan
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Linde GmbH
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Linde GmbH
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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
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04284—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams
    • F25J3/0429—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams of feed air, e.g. used as waste or product air or expanded into an auxiliary column
    • F25J3/04303—Lachmann expansion, i.e. expanded into oxygen producing or low pressure column
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04151—Purification and (pre-)cooling of the feed air; recuperative heat-exchange with product streams
    • F25J3/04187—Cooling of the purified feed air by recuperative heat-exchange; Heat-exchange with product streams
    • F25J3/04193—Division of the main heat exchange line in consecutive sections having different functions
    • F25J3/04206—Division of the main heat exchange line in consecutive sections having different functions including a so-called "auxiliary vaporiser" for vaporising and producing a gaseous product
    • F25J3/04212—Division of the main heat exchange line in consecutive sections having different functions including a so-called "auxiliary vaporiser" for vaporising and producing a gaseous product and simultaneously condensing vapor from a column serving as reflux within the or another column
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04406—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using a dual pressure main column system
    • F25J3/04412—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using a dual pressure main column system in a classical double column flowsheet, i.e. with thermal coupling by a main reboiler-condenser in the bottom of low pressure respectively top of high pressure column
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04642—Recovering noble gases from air
    • F25J3/04648—Recovering noble gases from air argon
    • F25J3/04654—Producing crude argon in a crude argon column
    • F25J3/04666—Producing crude argon in a crude argon column as a parallel working rectification column of the low pressure column in a dual pressure main column system
    • F25J3/04672—Producing crude argon in a crude argon column as a parallel working rectification column of the low pressure column in a dual pressure main column system having a top condenser
    • F25J3/04678—Producing crude argon in a crude argon column as a parallel working rectification column of the low pressure column in a dual pressure main column system having a top condenser cooled by oxygen enriched liquid from high pressure column bottoms
    • 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
    • F25J3/04648—Recovering noble gases from air argon
    • F25J3/04654—Producing crude argon in a crude argon column
    • F25J3/04709—Producing crude argon in a crude argon column as an auxiliary column system in at least a dual pressure main column system
    • F25J3/04715—The auxiliary column system simultaneously produces 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
    • 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
    • F25J2200/32—Processes or apparatus using separation by rectification using a side column fed by a stream from the 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
    • F25J2200/34—Processes or apparatus using separation by rectification using a side column fed by a stream from the low pressure column
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/90—Details relating to column internals, e.g. structured packing, gas or liquid distribution
    • F25J2200/94—Details relating to the withdrawal point
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/02—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum
    • 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
    • F25J2215/42—Nitrogen or special cases, e.g. multiple or low purity N2
    • F25J2215/44—Ultra high purity nitrogen, i.e. generally less than 1 ppb impurities
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2215/00—Processes characterised by the type or other details of the product stream
    • F25J2215/50—Oxygen or special cases, e.g. isotope-mixtures or low purity O2
    • F25J2215/52—Oxygen production with multiple purity O2
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2215/00—Processes characterised by the type or other details of the product stream
    • F25J2215/50—Oxygen or special cases, e.g. isotope-mixtures or low purity O2
    • F25J2215/56—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
    • F25J2220/42—Separating low boiling, i.e. more volatile components from nitrogen, e.g. He, H2, Ne
    • 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
    • F25J2250/00—Details related to the use of reboiler-condensers
    • F25J2250/20—Boiler-condenser with multiple exchanger cores in parallel or with multiple re-boiling or condensing 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
    • F25J2250/00—Details related to the use of reboiler-condensers
    • F25J2250/30—External or auxiliary boiler-condenser in general, e.g. without a specified fluid or one fluid is not a primary air component or an intermediate fluid
    • F25J2250/42—One fluid being nitrogen
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S62/00—Refrigeration
    • Y10S62/923—Inert gas
    • Y10S62/924—Argon

Definitions

  • the invention further relates to an apparatus for performing such a method.
  • U.S. Patent No. 4,575,388 also shows a crude argon column into which argon-enriched gas is introduced from the second rectification stage.
  • a liquid bottom fraction consisting essentially of oxygen is returned from the crude argon column to the second rectification stage.
  • the oxygen-rich liquid that accumulates in the bottom of the crude argon column has a relatively high concentration of impurities, since the argon-enriched fraction from the second rectification stage contains oxygen and nitrogen in addition to krypton, xenon and hydrocarbons, all of which collect in the bottom of the crude argon column .
  • the impurities By returning the bottom liquid to the second rectification stage, the impurities get into the bottom of the second rectification stage and thus into the oxygen removed as a decomposition product.
  • the process does not allow high-purity, in particular liquid, oxygen which is free from krypton, xenon and hydrocarbons to be obtained from the second rectification stage.
  • High-purity oxygen is required, for example, in the electronics industry.
  • Nitrogen which is obtained in the known process, also contains traces of other gases, for example of helium, neon, hydrogen and carbon monoxide. However, nitrogen of the highest purity is required for the modern semiconductor industry.
  • the removal of carbon monoxide can be carried out catalytically.
  • a helium discharge usually attached to the head of the first rectification stage can only bring about a slight reduction in helium, neon and hydrogen.
  • the invention is therefore based on the object of developing a method of the type mentioned at the outset which enables the production of high-purity decomposition products, preferably high-purity oxygen and high-purity nitrogen.
  • This object is achieved in that a further fraction above the bottom is taken from a crude argon column into which a stream essentially containing oxygen and argon is introduced from the second rectification stage and is broken down into high-purity oxygen and a lighter residual fraction in a high-purity oxygen column.
  • oxygen can be produced as a high-purity decomposition product which is essentially free of argon, krypton, xenon and hydrocarbons.
  • the concentration of krypton, xenon and hydrocarbons in the crude argon column decreases from the bottom of the column.
  • the fraction removed above the bottom of the column therefore only contains the components oxygen, argon and nitrogen, while it is free from krypton, xenon and hydrocarbons.
  • the oxygen is separated by rectification from nitrogen and argon. In this way, oxygen with a purity of less than 10 ppm, preferably less than 5 ppm, most preferably less than 2 ppm of hydrocarbons, krypton, xenon and nitrogen and a content of less than 20 ppm, preferably less than 15 ppm, of argon produce.
  • the oxygen obtained in the bottom of the pure oxygen column is preferably taken off in liquid form. If high-purity gaseous oxygen is to be produced using the method, at least a portion of the high-purity oxygen is removed in gaseous form from the high-purity oxygen column. The removal takes place just above the column bottom.
  • the residual fraction which essentially contains oxygen, argon and nitrogen, is removed from the top of the high-purity oxygen column and preferably returned to the crude argon column or to the second rectification stage above the removal point of the further fraction.
  • the further fraction is removed in liquid form and added to the ultrapure oxygen column as reflux liquid.
  • the further fraction is removed from several trays above the column bottom of the crude argon column.
  • the bottoms between the column sump and the tapping point act as a barrier to the undesirable proportions of krypton, xenon and hydrocarbons.
  • the high-purity oxygen is removed from a plurality of trays above the bottom of the ultrapure oxygen column.
  • the only fraction which is introduced into the pure oxygen column generally contains impurities of the type mentioned only in orders of magnitude far below ppm. Nevertheless, such fractions can get into the bottom of the ultrapure oxygen column by enriching the smallest traces or by penetrating from the outside, for example through leaks in the bottom heating. Therefore, the removal is a few, preferably three to five floors above the sump
  • the ultra-pure oxygen column is particularly inexpensive, since these trays - as in the crude argon column - serve as a barrier for unwanted traces of krypton, xenon and hydrocarbons.
  • the high-purity oxygen can be withdrawn at this point both in liquid and in gaseous form. In order to avoid a slow accumulation of impurities in the sump during operation, it is advantageous if a small part of the sump liquid is led out of the high-purity oxygen column and discarded or returned to the second rectification stage.
  • the column bottom of the further column is heated by nitrogen from the top of the first rectification stage.
  • the heating is preferably carried out by heat exchange in a condenser evaporator arranged in the bottom of the ultrapure oxygen column. It is advantageous here if the nitrogen condenses at least partially during the heating and the condensate is returned to the pressure stage.
  • An apparatus for carrying out the process according to the invention comprises a two-stage rectification column and a crude argon column connected to its second stage and is characterized by a high-purity oxygen column which is connected to the crude argon column by means of a lateral removal line, the lateral withdrawal line being arranged a plurality of rectification trays above the bottom of the crude argon column .
  • the object on which the invention is based is further achieved in that a further nitrogen-rich fraction is introduced from the top of the first rectification stage into a high-purity nitrogen column and is broken down there into a bottom liquid and into a residual gas fraction, the bottom liquid being returned to the top of the first rectification stage and some trays below a liquid fraction of high-purity nitrogen is removed from the top of the first rectification stage.
  • nitrogen can be produced as a very pure decomposition product.
  • helium, neon, hydrogen and carbon monoxide are rectified from the nitrogen in the high-purity nitrogen column and removed in a residual gas fraction.
  • the residual gas fraction can, for example, be admixed with impure nitrogen, which is usually taken from the second rectification stage and used to regenerate molecular sieve adsorbers.
  • liquid nitrogen to the first rectification stage and the removal below some barrier trays cause residues of light gases such as helium, neon or hydrogen to be retained, which despite a helium discharge are also present at the top of the first rectification stage when the additional rectification is used in the high-purity nitrogen column can enrich.
  • the liquid high-purity nitrogen has a purity of 99.999% and still contains argon, helium, neon, hydrogen and carbon monoxide.
  • the liquid high-purity nitrogen is at least partially subcooled. This makes it easier to store the liquid product portion in a tank.
  • the cooling is preferably carried out in indirect heat exchange with nitrogen from the second rectification stage.
  • the nitrogen can then be fed into a separator and removed as a liquid.
  • liquid high-purity nitrogen is at least partially evaporated from the top of the first rectification stage in heat exchange with condensing nitrogen.
  • An apparatus for carrying out the process for the production of high-purity nitrogen comprises a two-stage rectification column, in which a first and a second rectification stage are in heat-exchanging connection via a common condenser-evaporator, a high-purity nitrogen column, the lower region of which is connected to the through a gas line and through a liquid line is connected to the upper region of the first rectification stage, and a removal line for high-purity nitrogen, which is attached to the first rectification stage some trays below the head.
  • the process steps from one of claims 1 to 5 and the process steps from one of claims 7 to 9 are used together in the process according to the invention and, moreover, the bottom liquid of the ultrapure oxygen column is heated by heat exchange with the gas in the top of the ultrapure nitrogen column.
  • both oxygen and nitrogen can be produced as decomposition products of the highest purity.
  • the energy consumption is particularly low due to the heat exchange between the high-purity oxygen and high-purity nitrogen columns.
  • a device for carrying out this method additionally has a condenser-evaporator which is fitted between the high-purity oxygen and high-purity nitrogen column.
  • a condenser-evaporator which is fitted between the high-purity oxygen and high-purity nitrogen column.
  • Air contaminated with impurities such as C0 2 and H 2 0 and compressed to a pressure of approx. 6.3 bar is fed via a line 1 to the first stage 2 of a two-stage rectification column 3.
  • the air is split into a nitrogen-rich fraction in the head and an oxygen-rich fraction in the swamp.
  • a portion of the nitrogen-rich fraction is removed in liquid form (line 4), subcooled in a heat exchanger 5, decompressed and fed at a temperature of about ⁇ 193 ° C. as reflux to the second stage 6 of the rectification column 3.
  • the two stages 2, 6 of the rectification column 3 are in heat-exchanging connection with one another via a common condenser-evaporator 7.
  • the oxygen-rich fraction from the bottom of the first stage 2 is removed via a line 8, subcooled in the heat exchanger 5 and removed therefrom at an intermediate point which is at a higher temperature level than the nitrogen-rich fraction 4 supplied.
  • a portion of the oxygen-rich fraction, which is at a temperature of approximately ⁇ 182 ° C., is fed to the second stage 6 at an intermediate point, while the rest is fed as a coolant to a condenser-evaporator 9 in the top of a crude argon column 10.
  • Another pre-cleaned air stream which has been compressed to generate cold and then expanded, is fed via a line 11 to the second stage 6 approximately at the level of the supply of the oxygen-rich fraction 8.
  • the pre-separation fractions from the first stage are converted into pure oxygen, which is obtained in the column bottom and pure nitrogen, which is obtained in the top of the column, disassembled.
  • the oxygen is typically 99.5% pure and contains about 0.5% argon and additionally all krypton and xenon as well as the hydrocarbons in the ppm range that are present in the air.
  • the oxygen is withdrawn in gaseous form above the column bottom via a line 12 and / or in liquid form from the column bottom via a line 13.
  • the liquid oxygen is subcooled in the heat exchanger 5.
  • Liquid nitrogen (line 14) with a purity of 99.995% is led out of the top of the second stage 6.
  • Gaseous pure nitrogen with a purity of 99.995% is removed from the top of the second stage 6 via a line 15.
  • These two nitrogen fractions are still contaminated by the usual components such as oxygen, argon, helium, neon, hydrogen and carbon monoxide.
  • Impure gaseous nitrogen (approx. 0.15% 0 2 content) is removed from the upper third of the column via a line 16.
  • the two gaseous nitrogen streams are heated in the heat exchanger 5 and removed from the system.
  • the argon concentration is highest in the second stage 6 somewhat below the middle of the column, for example between the 35th and 36th plate with a total plate number of 96.
  • a fraction from the second stage is removed via line 17, which contains up to 91% 0 2 a few ppm N 2 to 9% argon and traces of xenon, krypton, hydrocarbons in the ppm range.
  • This fraction is fed to the crude argon column 10 at its lower end and is broken down there by rectification into a gaseous crude argon fraction which is taken from the top of the crude argon column via a line 18 and a liquid bottom fraction which is returned to the second stage via a line 19.
  • the crude argon fraction preferably has a composition of 2% 0 2 , 97% argon and 1% N 2 , the bottom liquid has a composition of 94% 0 2 , 6% argon.
  • a portion of the crude argon is condensed to form reflux liquid in the condenser-evaporator 9 by heat exchange with previously relaxed oxygen-rich liquid from the first rectification stage 2.
  • the oxygen-rich liquid is partially evaporated.
  • the vaporized portion is removed via a line 20 and passed into the second stage 6 together with the liquid (line 21) removed from the evaporator space.
  • a liquid fraction is removed from the crude argon column via a line 22 and fed to a high-purity oxygen column 23.
  • the fraction 22 consists only of the components 0 2 , argon and N 2 and is free of krypton, xenon and hydrocarbons. The reason for this is that the impurities (krypton, xenon, hydrocarbons) are retained in the bottom of the column between the column sump and the removal point in the column sump and are returned to the second stage 6 via line 19.
  • the ultrapure oxygen column 23 which is operated at a temperature of -179 ° C and a pressure of 1.5 bar, nitrogen and argon are separated from the oxygen and removed as a gaseous residual fraction via a line 24 from the top and above the removal point of the liquid fraction 22 fed back into the crude argon column 10 or above the line 17 into the column 6 (dashed line 42).
  • High-purity liquid oxygen with a purity of 99.999% is removed from the bottom of the ultrapure oxygen column 23 via a line 25.
  • the oxygen typically has the following impurities: hydrocarbons, krypton, xenon, nitrogen each less than 1 ppm, argon less than 10 ppm.
  • the high-purity liquid oxygen is subcooled in the heat exchanger 5 and then removed from the system. If necessary, in addition or alternatively, high-purity gaseous oxygen above the Column sump can be removed via a line 26.
  • the column sump is heated by nitrogen, which is removed from the top of the first stage 2 and fed via a line 27 to a condenser-evaporator 28 arranged in the column sump. During the heat exchange, the nitrogen condenses and is returned to the head of the first stage 2 via a line 29. Part of the gaseous nitrogen is branched off from line 27 and removed via line 30.
  • FIG. 2 shows a modification of the method of FIG. 1. Since the major part of the modified method is identical to that of FIG. 1, only the ultrapure oxygen column 23 is shown in FIG.
  • the removal of the liquid high-purity oxygen via line 25 or the gaseous high-purity oxygen via line 26 takes place here some floors above the sump.
  • the preferably three to five rectification trays retain undesirable fractions such as krypton, xenon and hydrocarbons, which can get into the bottom of the ultrapure oxygen column 23 by enriching traces or by penetrating through a less dense point on the condenser-evaporator 28.
  • Line 43 is used to discharge a small amount of bottom liquid, which is either discarded or returned to the second rectification stage. In this way, the accumulation of undesirable fractions in the bottom of the ultrapure oxygen column 23 can be largely prevented.
  • FIG. 3 shows a further embodiment of the method according to the invention, in which high-purity nitrogen is generated.
  • Analog system parts are provided with the same reference numerals as in Figure 1.
  • Gaseous nitrogen from the top of the first rectification stage 2 is fed via line 27 into a high-purity nitrogen column 31, which is operated at approximately the same pressure as the first rectification stage, and is separated there into a liquid bottom fraction and a residual gas fraction.
  • the residual gas fraction contains undesirable fractions such as helium, neon and carbon monoxide and is drawn off via line 33 and admixed with the impure nitrogen fraction 16 from the second rectification stage 6.
  • the bottom fraction flows back via line 29 to the first rectification stage, from which high-purity nitrogen is withdrawn via line 34.
  • the high-purity nitrogen 34 has a purity of 99.999%, the rest consists essentially of argon.
  • a further line 32 opens into the high-purity nitrogen column 31.
  • the line 32 is connected directly to the condenser 7 and is also referred to as a helium drain.
  • the air components helium, neon and carbon monoxide accumulate in this area. These constituents are removed together with the nitrogen via line 32 from the first stage 2 and removed with the top fraction of the high-purity nitrogen column 31.
  • the top of the high-purity nitrogen column 31 is cooled with oxygen-rich liquid 46, which comes from the bottom of the first rectification stage 2.
  • the oxygen-rich liquid is partially evaporated, leaves the top condenser of the high-purity nitrogen column 31 via line 44 or 45 and is then introduced into the second rectification stage 6.
  • the nitrogen removed via line 34 is subcooled in heat exchanger 5 and then expanded.
  • the gas produced during the expansion is separated in a separator 35 and mixed with the nitrogen in line 15 via a line 36.
  • Liquid nitrogen of the highest purity can be removed via line 37.
  • the high-purity liquid nitrogen (line 38) is partially or completely expanded without prior cooling and fed to an evaporator 39.
  • the evaporator is heated by a partial flow of the gaseous nitrogen in line 30, which is branched off via a line 40 and, after the heat exchange in the evaporator 39, is admixed with the nitrogen-rich fraction 4.
  • the high-purity gaseous nitrogen is discharged from the evaporator 39 via a line 41.
  • FIG. 1 An embodiment of the method according to the invention, in which both high-purity oxygen and high-purity nitrogen can be produced, is shown in FIG.
  • the high-purity oxygen column 23 and the high-purity nitrogen column 31 are combined into one unit and are in heat-exchanging connection via a condenser-evaporator 28 now common.
  • the heating of the bottom of the ultrapure oxygen column 27 and the cooling of the head of the ultrapure nitrogen column 31 can be carried out with the aid of only one heat exchange apparatus.

Abstract

In a process and apparatus for air separation by rectification air 1 is preliminarily separated in a first rectification stage 2 of a two-stage rectification column to obtain a nitrogen-rich fraction 4 and an oxygen-rich fraction 8. These two fractions are fed to the second rectification stage 6 and separated into oxygen and nitrogen fractions. An argon-enriched fraction, containing essentially oxygen and argon, is removed from the second rectification stage at an intermediate point and is separated in a raw argon column 10 by rectification into an argon-rich fraction 18 and a liquid fraction 19 containing essentially oxygen. The liquid fraction 19 is fed back into the second rectification stage. Another fraction 22 is removed from the raw argon column above the bottom thereof and is separated in a high-purity oxygen column 23 to produce a high-purity oxygen fraction 25, 26 and a lighter residual fraction 24. An additional nitrogen-rich fraction is removed from the head of the first rectification stage and separated in a high-purity nitrogen column 31 producing a bottom liquid fraction 29, which is fed back to the head of the first rectification stage, and a residual gas fraction 33. A high-purity nitrogen fraction 34 is removed at a point several plates below the head of the first rectification stage.

Description

Die Erfindung betrifft ferner eine Vorrichtung zur Durchführung eines derartigen Verfahrens.The invention further relates to an apparatus for performing such a method.

Ein Verfahren, bei dem Sauerstoff und Stickstoff durch zweistufige Rektifikation gewonnen werden, ist in der US-PS 4 575 388 beschrieben worden. Die Zerlegungsprodukte Sauerstoff und Stickstoff werden dabei dem Sumpf beziehungsweise dem Kopf der zweiten Rektifizierstufe entnommen.A process in which oxygen and nitrogen are obtained by two-stage rectification has been described in US Pat. No. 4,575,388. The decomposition products oxygen and nitrogen are removed from the bottom or the top of the second rectification stage.

Die US-PS 4 575 388 zeigt auch eine Rohargonkolonne, in die mit Argon angereichertes Gas aus der zweiten Rektifizierstufe eingeführt wird. Aus der Rohargonkolonne wird eine im wesentlichen aus Sauerstoff bestehende flüssige Sumpffraktion in die zweite Rektifizierstufe zurückgeleitet.U.S. Patent No. 4,575,388 also shows a crude argon column into which argon-enriched gas is introduced from the second rectification stage. A liquid bottom fraction consisting essentially of oxygen is returned from the crude argon column to the second rectification stage.

Die sauerstoffreiche Flüssigkeit, die im Sumpf der Rohargonkolonne anfällt, weist eine relativ hohe Konzentration an Verunreinigungen auf, da die mit Argon angereicherte Fraktion aus der zweiten Rektifizierstufe neben Sauerstoff und Stickstoff nach Krypton, Xenon und Kohlenwasserstoffe enthält, die sich alle im Sumpf der Rohargonkolonne ansammeln. Durch die Rückführung der Sumpfflüssigkeit in die zweite Rektifizierstufe gelangen die Verunreinigungen in den Sumpf der zweiten Rektifizierstufe und damit in den als Zerlegungsprodukt entnommenen Sauerstoff.The oxygen-rich liquid that accumulates in the bottom of the crude argon column has a relatively high concentration of impurities, since the argon-enriched fraction from the second rectification stage contains oxygen and nitrogen in addition to krypton, xenon and hydrocarbons, all of which collect in the bottom of the crude argon column . By returning the bottom liquid to the second rectification stage, the impurities get into the bottom of the second rectification stage and thus into the oxygen removed as a decomposition product.

Aufgrund der Verunreinigungen im Sauerstoff erlaubt es das Verfahren nicht, hochreinen, insbesondere flüssigen Sauerstoff, der frei von Krypton, Xenon und Kohlenwasserstoffen ist, aus der zweiten Rektifizierstufe zu gewinnen. Hochreiner Sauerstoff wird beispielsweise in der Elektronikindustrie benötigt.Because of the impurities in the oxygen, the process does not allow high-purity, in particular liquid, oxygen which is free from krypton, xenon and hydrocarbons to be obtained from the second rectification stage. High-purity oxygen is required, for example, in the electronics industry.

Auch Stickstoff, der in dem bekannten Verfahren gewonnen wird, enthält Spuren von anderen Gasen, beispielsweise von Helium, Neon, Wasserstoff und Kohlenmonoxid. Für die moderne Halbleiterindustrie wird jedoch Stickstoff höchster Reinheit benötigt.Nitrogen, which is obtained in the known process, also contains traces of other gases, for example of helium, neon, hydrogen and carbon monoxide. However, nitrogen of the highest purity is required for the modern semiconductor industry.

Die Entfernung von Kohlenmonoxid kann katalytisch durchgeführt werden. Ein üblicherweise am Kopf der ersten Rektifizierstufe angebrachter Heliumablaß kann jedoch nur eine geringe Reduktion an Helium, Neon und Wasserstoff bewirken. Zur weiteren Reinigung ist beispielsweise aus der EP-A 136 926 bekannt, Stickstoff aus der ersten Stufe einer zweistufigen Rektifizierkolonne in eine weitere Kolonne einzuleiten und aus dieser eine gasförmige und eine flüssige Fraktion abzuziehen. Auch dieses Verfahren führt nicht zu einer vollständig befriedigenden Entfernung von Helium, Neon, Wasserstoff und Kohlenmonoxid.The removal of carbon monoxide can be carried out catalytically. However, a helium discharge usually attached to the head of the first rectification stage can only bring about a slight reduction in helium, neon and hydrogen. For further purification it is known, for example from EP-A 136 926, to introduce nitrogen from the first stage of a two-stage rectification column into a further column and to draw off a gaseous and a liquid fraction from this. This method also does not lead to a completely satisfactory removal of helium, neon, hydrogen and carbon monoxide.

Der Erfindung liegt daher die Aufgabe zugrunde, ein Verfahren der eingangs genannten Art zu entwickeln, das die Erzeugung von hochreinen Zerlegungsprodukten, vorzugsweise von hochreinem Sauerstoff und hochreinem Stickstoff ermöglicht.The invention is therefore based on the object of developing a method of the type mentioned at the outset which enables the production of high-purity decomposition products, preferably high-purity oxygen and high-purity nitrogen.

Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß aus einer Rohargonkolonne, in die ein im wesentlichen Sauerstoff und Argon enthaltender Strom aus der zweiten Rektifizierstufe eingeführt wird, eine weitere Fraktion oberhalb des Sumpfes entnommen und in einer Reinstsauerstoffkolonne in hochreinen Sauerstoff und eine leichtere Restfraktion zerlegt wird.This object is achieved in that a further fraction above the bottom is taken from a crude argon column into which a stream essentially containing oxygen and argon is introduced from the second rectification stage and is broken down into high-purity oxygen and a lighter residual fraction in a high-purity oxygen column.

Mit Hilfe dieser Verfahrensschritte kann Sauerstoff als hochreines Zerlegungsprodukt hergestellt werden, das im wesentlichen frei von Argon, Krypton, Xenon und Kohlenwasserstoffen ist.With the aid of these process steps, oxygen can be produced as a high-purity decomposition product which is essentially free of argon, krypton, xenon and hydrocarbons.

Die Konzentration an Krypton, Xenon und Kohlenwasserstoffen in der Rohargonkolonne nimmt vom Kolonnensumpf nach oben ab. Die oberhalb des Kolonnensumpfes entnommene Fraktion enthält daher lediglich noch die Komponenten Sauerstoff, Argon und Stickstoff, während sie frei von Krypton, Xenon und Kohlenwasserstoffen ist. In der Reinstsauerstoffkolonne wird der Sauerstoff rektifikatorisch von Stickstoff und Argon abgetrennt. Auf diese Weise läßt sich Sauerstoff mit einer Reinheit von weniger als jeweils 10 ppm, vorzugsweise weniger als 5 ppm, höchst vorzugsweise weniger als 2 ppm Kohlenwasserstoffen, Krypton, Xenon und Stickstoff sowie einem Gehalt von weniger als 20 ppm, vorzugsweise weniger als 15 ppm Argon herstellen.The concentration of krypton, xenon and hydrocarbons in the crude argon column decreases from the bottom of the column. The fraction removed above the bottom of the column therefore only contains the components oxygen, argon and nitrogen, while it is free from krypton, xenon and hydrocarbons. In the high-purity oxygen column, the oxygen is separated by rectification from nitrogen and argon. In this way, oxygen with a purity of less than 10 ppm, preferably less than 5 ppm, most preferably less than 2 ppm of hydrocarbons, krypton, xenon and nitrogen and a content of less than 20 ppm, preferably less than 15 ppm, of argon produce.

Der im Sumpf der Reinsauerstoffkolonne gewonnene Sauerstoff wird vorzugsweise in flüssiger Form entnommen. Soll mit dem Verfahren hochreiner gasförmiger Sauerstoff erzeugt werden, so wird zumindest ein Teil des hochreinen Sauerstoffs gasförmig aus der Reinstsauerstoffkolonne entnommen. Die Entnahme erfolgt hierbei dicht oberhalb des Kolonnensumpfes.The oxygen obtained in the bottom of the pure oxygen column is preferably taken off in liquid form. If high-purity gaseous oxygen is to be produced using the method, at least a portion of the high-purity oxygen is removed in gaseous form from the high-purity oxygen column. The removal takes place just above the column bottom.

Die Restfraktion, die im wesentlichen Sauerstoff, Argon und Stickstoff enthält, wird vom Kopf der Reinstsauerstoffkolonne abgeführt und vorzugsweise oberhalb der Entnahmestelle der weiteren Fraktion in die Rohargonkolonne oder in die zweite Rektifizierstufe zurückgeleitet.The residual fraction, which essentially contains oxygen, argon and nitrogen, is removed from the top of the high-purity oxygen column and preferably returned to the crude argon column or to the second rectification stage above the removal point of the further fraction.

Bei einer bevorzugten Weiterbildung des erfindungsgemäßen Verfahrens wird die weitere Fraktion in flüssiger Form entnommen und als Rücklaufflüssigkeit auf die Reinstsauerstoffkolonne aufgegeben.In a preferred development of the method according to the invention, the further fraction is removed in liquid form and added to the ultrapure oxygen column as reflux liquid.

Gemäß einer bevorzugten Weiterbildung des erfindungsgemäßen Verfahrens erfolgt die Entnahme der weiteren Fraktion mehrere Böden oberhalb des Säulensumpfes der Rohargonkolonne.According to a preferred development of the method according to the invention, the further fraction is removed from several trays above the column bottom of the crude argon column.

Die Böden zwischen dem Säulensumpf und der Entnahmestelle wirken als Sperre für die unerwünschten Anteile Krypton, Xenon und Kohlenwasserstoffen. Vorzugsweise sind drei bis fünf Rektifizierböden als Sperre vorgesehen.The bottoms between the column sump and the tapping point act as a barrier to the undesirable proportions of krypton, xenon and hydrocarbons. Preferably three to five rectification trays are provided as a barrier.

Bei einer bevorzugten Weiterbildung des erfindungsgemäßen Verfahrens wird der hochreine Sauerstoff mehrere Böden oberhalb des Sumpfes der Reinstsauerstoffkolonne entnommen.In a preferred development of the process according to the invention, the high-purity oxygen is removed from a plurality of trays above the bottom of the ultrapure oxygen column.

Die einzige Fraktion, die in die Reinsauerstoffkolonne eingeführt wird, enthält zwar im allgemeinen Verunreinigungen der genannten Art nur in Größenordnungen weit unterhalb von ppm. Trotzdem können sich solche Anteile durch Anreicherung von kleinsten Spuren oder durch Eindringen von außen beispielsweise durch undichte Stellen in der Sumpfheizung in den Sumpf der Reinstsauerstoffkolonne gelangen. Deswegen ist die Entnahme einige, vorzugsweise drei bis fünf Böden oberhalb des Sumpfes der Reinstsauerstoffkolonne besonders günstig, da diese Böden - wie in der Rohargonsäule - als Sperre für unerwünschte Spuren von Krypton, Xenon und Kohlenwasserstoffen dienen. Der hochreine Sauerstoff kann an dieser Stelle sowohl flüssig als auch gasförmig entnommen werden. Um eine langsame Anreicherung von Verunreinigungen im Sumpf während des Betriebs zu vermeiden, ist es vorteilhaft, wenn ein kleiner Teil der Sumpfflüssigkeit aus der Reinstsauerstoffkolonne herausgeführt und verworfen oder in die zweite Rektifizierstufe zurückgeführt wird.The only fraction which is introduced into the pure oxygen column generally contains impurities of the type mentioned only in orders of magnitude far below ppm. Nevertheless, such fractions can get into the bottom of the ultrapure oxygen column by enriching the smallest traces or by penetrating from the outside, for example through leaks in the bottom heating. Therefore, the removal is a few, preferably three to five floors above the sump The ultra-pure oxygen column is particularly inexpensive, since these trays - as in the crude argon column - serve as a barrier for unwanted traces of krypton, xenon and hydrocarbons. The high-purity oxygen can be withdrawn at this point both in liquid and in gaseous form. In order to avoid a slow accumulation of impurities in the sump during operation, it is advantageous if a small part of the sump liquid is led out of the high-purity oxygen column and discarded or returned to the second rectification stage.

Bei einer weiteren bevorzugten Ausgestaltung des erfindungsgemäßen Verfahrens wird der Säulensumpf der weiteren Kolonne durch Stickstoff vom Kopf der ersten Rektifizierstufe beheizt.In a further preferred embodiment of the process according to the invention, the column bottom of the further column is heated by nitrogen from the top of the first rectification stage.

Die Beheizung erfolgt vorzugsweise durch Wärmetausch in einem im Sumpf der Reinstsauerstoffkolonne angeordneten Kondensator-Verdampfer. Hierbei ist es von Vorteil, wenn der Stickstoff bei der Beheizung mindestens teilweise kondensiert und das Kondensat in die Druckstufe zurückgeleitet wird.The heating is preferably carried out by heat exchange in a condenser evaporator arranged in the bottom of the ultrapure oxygen column. It is advantageous here if the nitrogen condenses at least partially during the heating and the condensate is returned to the pressure stage.

Eine Vorrichtung zur Durchführung des erfindungsgemäßen Verfahrens umfaßt eine zweistufige Rektifizierkolonne und eine mit deren zweiter Stufe verbundene Rohargonkolonne und ist gekennzeichnet durch eine Reinstsauerstoffkolonne, die mittels einer seitlichen Entnahmeleitung mit der Rohargonkolonne verbunden ist, wobei die seitliche Entnahmeleitung mehrere Rektifizierböden oberhalb des Sumpfes der Rohargonkolonne angeordnet ist.An apparatus for carrying out the process according to the invention comprises a two-stage rectification column and a crude argon column connected to its second stage and is characterized by a high-purity oxygen column which is connected to the crude argon column by means of a lateral removal line, the lateral withdrawal line being arranged a plurality of rectification trays above the bottom of the crude argon column .

Die der Erfindung zugrundeliegende Aufgabe wird weiterhin dadurch gelöst, daß eine weitere stickstoffreiche Fraktion vom Kopf der ersten Rektifizierstufe in eine Reinststickstoffkolonne eingeführt und dort in eine Sumpfflüssigkeit und in eine Restgasfraktion zerlegt wird, wobei die Sumpfflüssigkeit zum Kopf der ersten Rektifzierstufe zurückgeleitet wird und einige Böden unterhalb des Kopfes der ersten Rektifizierstufe eine flüssige Fraktion aus hochreinem Stickstoff entnommen wird.The object on which the invention is based is further achieved in that a further nitrogen-rich fraction is introduced from the top of the first rectification stage into a high-purity nitrogen column and is broken down there into a bottom liquid and into a residual gas fraction, the bottom liquid being returned to the top of the first rectification stage and some trays below a liquid fraction of high-purity nitrogen is removed from the top of the first rectification stage.

Durch die Anwendung dieser Verfahrensschritte kann Stickstoff als sehr reines Zerlegungsprodukt hergestellt werden. Dazu werden in der Reinststickstoffkolonne Helium, Neon, Wasserstoff und Kohlenmonoxid rektifikatorisch vom Stickstoff abgetrennt und in einer Restgasfraktion herausgeführt. Die Restgasfraktion kann beispielsweise unreinem Stickstoff, der üblicherweise der zweiten Rektifizierstufe entnommen und zur Regenerierung von Molsiebadsorbern eingesetzt wird, beigemischt werden.By using these process steps, nitrogen can be produced as a very pure decomposition product. For this purpose, helium, neon, hydrogen and carbon monoxide are rectified from the nitrogen in the high-purity nitrogen column and removed in a residual gas fraction. The residual gas fraction can, for example, be admixed with impure nitrogen, which is usually taken from the second rectification stage and used to regenerate molecular sieve adsorbers.

Die Rückführung von flüssigen Stickstoff in die erste Rektifizierstufe und die Entnahme unterhalb einiger Sperrböden bewirken, daß Reste von leichten Gasen wie Helium, Neon oder Wasserstoff zurückgehalten werden, die sich trotz eines Heliumablasses auch bei Anwendung der zusätzlichen Rektifikation in der Reinststickstoffkolonne am Kopf der ersten Rektifizierstufe anreichern können. Der flüssige hochreine Stickstoff weist eine Reinheit von 99,999% auf und enthält noch Argon, Helium, Neon, Wasserstoff und Kohlenmonoxid.The return of liquid nitrogen to the first rectification stage and the removal below some barrier trays cause residues of light gases such as helium, neon or hydrogen to be retained, which despite a helium discharge are also present at the top of the first rectification stage when the additional rectification is used in the high-purity nitrogen column can enrich. The liquid high-purity nitrogen has a purity of 99.999% and still contains argon, helium, neon, hydrogen and carbon monoxide.

In einer günstigen Weiterbildung des erfindungsgemäßen Verfahrens wird der flüssige hochreine Stickstoff mindestens teilweise unterkühlt. Dadurch wird die Speicherung des Flüssigproduktanteils in einem Tank erleichtert. Die Abkühlung wird vorzugsweise in indirektem Wärmetausch mit Stickstoff aus der zweiten Rektifizierstufe durchgeführt. Danach kann der Stickstoff in einen Abscheider geführt und aus diesem als Flüssigkeit entnommen werden.In a favorable development of the method according to the invention, the liquid high-purity nitrogen is at least partially subcooled. This makes it easier to store the liquid product portion in a tank. The cooling is preferably carried out in indirect heat exchange with nitrogen from the second rectification stage. The nitrogen can then be fed into a separator and removed as a liquid.

Falls ein Teil des hochreinen Stickstoffs gasförmig gewonnen werden soll, erweist es sich als günstig, wenn der flüssige hochreine Stickstoff mindestens teilweise in Wärmetausch mit kondensierendem Stickstoff aus dem Kopf der ersten Rektifizierstufe verdampft wird.If part of the high-purity nitrogen is to be obtained in gaseous form, it proves to be advantageous if the liquid high-purity nitrogen is at least partially evaporated from the top of the first rectification stage in heat exchange with condensing nitrogen.

Eine Vorrichtung zur Durchführung des Verfahrens zur Gewinnung von hochreinem Stickstoff umfaßt eine zweistufige Rektifizierkolonne, bei der eine erste und eine zweite Rektifizierstufe über einen gemeinsamen Kondensator-Verdampfer in wärmetauschender Verbindung stehen, eine Reinststickstoffkolonne, deren unterer Bereich durch eine Gasleitung und durch eine Flüssigkeitsleitung mit dem oberen Bereich der ersten Rektifizierstufe verbunden ist, und eine Entnahmeleitung für hochreinen Stickstoff, die einige Böden unterhalb des Kopfes an der ersten Rektifizierstufe angebracht ist.An apparatus for carrying out the process for the production of high-purity nitrogen comprises a two-stage rectification column, in which a first and a second rectification stage are in heat-exchanging connection via a common condenser-evaporator, a high-purity nitrogen column, the lower region of which is connected to the through a gas line and through a liquid line is connected to the upper region of the first rectification stage, and a removal line for high-purity nitrogen, which is attached to the first rectification stage some trays below the head.

In einer bevorzugten Weiterbildung werden bei dem erfindungsgemäßen Verfahren die Verfahrensschritte aus einem der Ansprüche 1 bis 5 und die Verfahrensschritte aus einem der Ansprüche 7 bis 9 gemeinsam angewandt und außerdem die Sumpfflüssigkeit der Reinstsauerstoffkolonne durch Wärmetausch mit dem Gas im Kopf der Reinststickstoffkolonne beheizt.In a preferred development, the process steps from one of claims 1 to 5 and the process steps from one of claims 7 to 9 are used together in the process according to the invention and, moreover, the bottom liquid of the ultrapure oxygen column is heated by heat exchange with the gas in the top of the ultrapure nitrogen column.

Auf diese Weise können sowohl Sauerstoff als auch Stickstoff als Zerlegungsprodukte von höchster Reinheit hergestellt werden. Der Energieaufwand ist durch den Wärmetausch zwischen Reinstsauerstoff- und Reinststickstoffkolonne besonders gering.In this way, both oxygen and nitrogen can be produced as decomposition products of the highest purity. The energy consumption is particularly low due to the heat exchange between the high-purity oxygen and high-purity nitrogen columns.

Eine Vorrichtung zur Durchführung dieses Verfahrens weist zusätzlich einen Kondensator-Verdampfer auf, der zwischen Reinstsauerstoff- und Reinststickstoffkolonne angebracht ist. Auf diese Weise können Reinstsauerstoff- und Reinststickstoffkolonne als eine Einheit gefertigt werden, was weitere Einsparungen bei Fertigungs- und Kapitalkosten bewirkt.A device for carrying out this method additionally has a condenser-evaporator which is fitted between the high-purity oxygen and high-purity nitrogen column. In this way, high-purity oxygen and high-purity nitrogen columns can be manufactured as one unit, which brings further savings in production and capital costs.

Die Erfindung sowie weitere Einzelheiten der Erfindung werden anhand von schematisch dargestellten Ausführungsbeispielen näher erläutert:

  • Hierbei zeigen:
    • Figur 1 ein Verfahrensschema einer Ausführungsform des erfindungsgemäßen Verfahrens zur Erzeugung von hochreinem Sauerstoff,
    • Figur 2 eine schematische Darstellung eines Details aus einer weiteren Ausführungsform zur Erzeugung von hochreinem Sauerstoff,
    • Figur 3 eine Ausführungsform des erfindungsgemäßen Verfahrens zur Erzeugung von hochreinem Stickstoff und
    • Figur 4 ein Verfahrensschema einer weiteren Ausführungsform des erfindungsgemäßen Verfahrens zur gleichzeitigen Erzeugung von hochreinem Sauerstoff und hochreinem Stickstoff.
The invention and further details of the invention are explained in more detail with reference to schematically illustrated exemplary embodiments:
  • Here show:
    • FIG. 1 shows a process diagram of an embodiment of the process according to the invention for producing high-purity oxygen,
    • FIG. 2 shows a schematic illustration of a detail from a further embodiment for producing high-purity oxygen,
    • FIG. 3 shows an embodiment of the method according to the invention for producing high-purity nitrogen and
    • FIG. 4 shows a process diagram of a further embodiment of the process according to the invention for the simultaneous production of high-purity oxygen and high-purity nitrogen.

Gleiche oder analoge Verfahrensschritte beziehungsweise Anlagenteile tragen in den Figuren dieselben Bezugszeichen.Identical or analogous process steps or plant parts have the same reference symbols in the figures.

Von Verunreinigungen wie C02 und H20 in üblicher Weise vorgereinigte und auf einen Druck von ca. 6,3 bar komprimierte Luft wird über eine Leitung 1 der ersten Stufe 2 einer zweistufigen Rektifizierkolonne 3 zugeführt. Bei einer Temperatur von ca. -177°C wird die Luft in eine stickstoffreiche Fraktion im Kopf und eine sauerstoffreiche Fraktion im Sumpf vorzerlegt. Ein Teil der stickstoffreichen Fraktion wird in flüssiger Form entnommen (Leitung 4), in einem Wärmetauscher 5 unterkühlt, entspannt und mit einer Temperatur von etwa - 193°C als Rücklauf auf die zweiten Stufe 6 der Rektifizierkolonne 3 aufgegeben. Die beiden Stufen 2,6 der Rektifizierkolonne 3 stehen über einen gemeinsamen Kondensator-Verdampfer 7 in wärmetauschender Verbindung miteinander.Air contaminated with impurities such as C0 2 and H 2 0 and compressed to a pressure of approx. 6.3 bar is fed via a line 1 to the first stage 2 of a two-stage rectification column 3. At a temperature of approx. -177 ° C, the air is split into a nitrogen-rich fraction in the head and an oxygen-rich fraction in the swamp. A portion of the nitrogen-rich fraction is removed in liquid form (line 4), subcooled in a heat exchanger 5, decompressed and fed at a temperature of about −193 ° C. as reflux to the second stage 6 of the rectification column 3. The two stages 2, 6 of the rectification column 3 are in heat-exchanging connection with one another via a common condenser-evaporator 7.

Die sauerstoffreiche Fraktion aus dem Sumpf der ersten Stufe 2 wird über eine Leitung 8 entnommen, im Wärmetauscher 5 unterkühlt und an einer Zwischenstelle, die auf einem höheren Temperaturniveau als die zugeführte stickstoffreiche Fraktion 4 liegt, daraus entnommen. Ein Teil der sauerstoffreichen Fraktion, die auf einer Temperatur von ca. - 182°C ist, wird an einer Zwischenstelle auf die zweite Stufe 6 aufgegeben, während der Rest als Kühlmittel einem Kondensator-Verdampfer 9 im Kopf einer Rohargonkolonne 10 zugeführt wird.The oxygen-rich fraction from the bottom of the first stage 2 is removed via a line 8, subcooled in the heat exchanger 5 and removed therefrom at an intermediate point which is at a higher temperature level than the nitrogen-rich fraction 4 supplied. A portion of the oxygen-rich fraction, which is at a temperature of approximately −182 ° C., is fed to the second stage 6 at an intermediate point, while the rest is fed as a coolant to a condenser-evaporator 9 in the top of a crude argon column 10.

Ein weiterer vorgereinigter Luftstrom, der zur Kälteerzeugung komprimiert und anschließend entspannt worden ist, wird über eine Leitung 11 der zweiten Stufe 6 etwa in Höhe der Zuführung der sauerstoffreichen Fraktion 8 zugeführt. In der zweiten Stufe 6, die bei einer Temperatur von ca. -179°C und einem Druck von ca. 1,6 bar betrieben wird, werden die Vorzerlegungsfraktionen aus der ersten Stufe in reinen Sauerstoff, der im Kolonnensumpf gewonnen wird und reinen Stickstoff, der im Kopf der Kolonne gewonnen wird, zerlegt. Der Sauerstoff hat typischerweise eine Reinheit von 99,5 % und enthält noch ca. 0,5% Argon und zusätzlich das gesamte Krypton und Xenon sowie die Kohlenwasserstoffe im ppm-Bereich, die in der Luft vorhanden sind.Another pre-cleaned air stream, which has been compressed to generate cold and then expanded, is fed via a line 11 to the second stage 6 approximately at the level of the supply of the oxygen-rich fraction 8. In the second stage 6, which is operated at a temperature of approximately -179 ° C. and a pressure of approximately 1.6 bar, the pre-separation fractions from the first stage are converted into pure oxygen, which is obtained in the column bottom and pure nitrogen, which is obtained in the top of the column, disassembled. The oxygen is typically 99.5% pure and contains about 0.5% argon and additionally all krypton and xenon as well as the hydrocarbons in the ppm range that are present in the air.

Der Sauerstoff wird gasförmig oberhalb des Kolonnensumpfes über eine Leitung 12 und/oder in flüssiger Form aus dem Kolonnensumpf über eine Leitung 13 entnommen. Der flüssige Sauerstoff wird im Wärmetauscher 5 unterkühlt.The oxygen is withdrawn in gaseous form above the column bottom via a line 12 and / or in liquid form from the column bottom via a line 13. The liquid oxygen is subcooled in the heat exchanger 5.

Aus dem Kopf der zweiten Stufe 6 wird flüssiger Stickstoff (Leitung 14) mit einer Reinheit von 99,995 % herausgeführt. Gasförmiger reiner Stickstoff mit einer Reinheit von 99,995% wird über eine Leitung 15 vom Kopf der zweiten Stufe 6 entnommen. Diese beiden Stickstofffraktionen sind noch durch die üblichen Bestandteile wie Sauerstoff, Argon, Helium, Neon, Wasserstoff und Kohlenmonoxid verunreinigt.Liquid nitrogen (line 14) with a purity of 99.995% is led out of the top of the second stage 6. Gaseous pure nitrogen with a purity of 99.995% is removed from the top of the second stage 6 via a line 15. These two nitrogen fractions are still contaminated by the usual components such as oxygen, argon, helium, neon, hydrogen and carbon monoxide.

Unreiner gasförmiger Stickstoff (ca. 0,15% 02-Gehalt) wird über eine Leitung 16 aus dem oberen Kolonnendrittel entnommen. Die beiden gasförmigen Stickstoffströme werden im Wärmetauscher 5 angewärmt und aus der Anlage abgeführt.Impure gaseous nitrogen (approx. 0.15% 0 2 content) is removed from the upper third of the column via a line 16. The two gaseous nitrogen streams are heated in the heat exchanger 5 and removed from the system.

Etwas unterhalb der Kolonnenmitte, etwa zwischen dem 35. und 36. Boden bei einer Gesamtbodenzahl von 96 ist die Argonkonzentration in der zweiten Stufe 6 am höchsten. In Höhe dieser Stelle wird über eine Leitung 17 eine Fraktion aus der zweiten Stufe entnommen, die bis 91% 02 wenige ppm N2 bis 9% Argon sowie Spuren von Xenon, Krypton, Kohlenwasserstoffen im ppm-Bereich enthält. Diese Fraktion wird der Rohargonkolonne 10 an ihrem unteren Ende zugeführt und dort durch Rektifikation in eine gasförmige Rohargonfraktion, die vom Kopf der Rohargonkolonne über eine Leitung 18 entnommen wird und eine flüssige Sumpffraktion, die über eine Leitung 19 in die zweite Stufe zurückgeleitet wird, zerlegt. Die Rohargonfraktion weist vorzugsweise eine Zusammensetzung von 2% 02, 97% Argon und 1% N2 auf, die Sumpfflüssigkeit eine Zusammensetzung von 94% 02, 6% Argon auf.The argon concentration is highest in the second stage 6 somewhat below the middle of the column, for example between the 35th and 36th plate with a total plate number of 96. At this point, a fraction from the second stage is removed via line 17, which contains up to 91% 0 2 a few ppm N 2 to 9% argon and traces of xenon, krypton, hydrocarbons in the ppm range. This fraction is fed to the crude argon column 10 at its lower end and is broken down there by rectification into a gaseous crude argon fraction which is taken from the top of the crude argon column via a line 18 and a liquid bottom fraction which is returned to the second stage via a line 19. The crude argon fraction preferably has a composition of 2% 0 2 , 97% argon and 1% N 2 , the bottom liquid has a composition of 94% 0 2 , 6% argon.

Eine Teil des Rohargons wird unter Bildung von Rücklaufflüssigkeit im Kondensator-Verdampfer 9 durch Wärmetausch mit zuvor entspannter sauerstoffreicher Flüssigkeit aus der ersten Rektifizierstufe 2 kondensiert. Dabei wird die sauerstoffreiche Flüssigkeit zum Teil verdampft. Der verdampfte Anteil wird über eine Leitung 20 entnommen und zusammen mit aus dem Verdampferraum entnommener Flüssigkeit (Leitung 21) in die zweite Stufe 6 geleitet. Drei bis fünf Böden oberhalb der Sumpfflüssigkeit wird eine flüssige Fraktion über eine Leitung 22 aus der Rohargonkolonne entnommen und auf eine Reinstsauerstoffkolonne 23 aufgegeben. Die Fraktion 22 besteht nur noch aus den Komponenten 02, Argon und N2 und ist frei von Krypton, Xenon und Kohlenwasserstoffen. Der Grund hierfür liegt darin, daß die Verunreinigungen (Krypton, Xenon, Kohlenwasserstoffe) durch die Böden zwischen dem Kolonnensumpf und der Entnahmestelle im Kolonnensumpf festgehalten werden und über die Leitung 19 in die zweite Stufe 6 zurückgeschleust werden.A portion of the crude argon is condensed to form reflux liquid in the condenser-evaporator 9 by heat exchange with previously relaxed oxygen-rich liquid from the first rectification stage 2. The oxygen-rich liquid is partially evaporated. The vaporized portion is removed via a line 20 and passed into the second stage 6 together with the liquid (line 21) removed from the evaporator space. Three to five trays above the bottom liquid, a liquid fraction is removed from the crude argon column via a line 22 and fed to a high-purity oxygen column 23. The fraction 22 consists only of the components 0 2 , argon and N 2 and is free of krypton, xenon and hydrocarbons. The reason for this is that the impurities (krypton, xenon, hydrocarbons) are retained in the bottom of the column between the column sump and the removal point in the column sump and are returned to the second stage 6 via line 19.

In der Reinstsauerstoffkolonne 23, die bei einer Temperatur von -179°C und einem Druck von 1,5 bar betrieben wird, werden Stickstoff und Argon vom Sauerstoff abgetrennt und als gasförmige Restfraktion über eine Leitung 24 vom Kopf entnommen und oberhalb der Entnahmestelle der flüssigen Fraktion 22 in die Rohargonkolonne 10 oder oberhalb der Leitung 17 in die Kolonne 6 (gestrichelte Leitung 42) zurückgeleitet. Aus dem Sumpf der Reinstsauerstoffkolonne 23 wird hochreiner flüssiger Sauerstoff mit einer Reinheit von 99,999% über eine Leitung 25 entnommen. Der Sauerstoff weist typisch folgende Verunreinigungen auf: Kohlenwasserstoffe, Krypton, Xenon, Stickstoff jeweils weniger als 1 ppm, Argon weniger als 10 ppm. Der hochreine flüssige Sauerstoff wird im Wärmetauscher 5 unterkühlt und anschließend aus der Anlage abgeführt. Bei Bedarf kann zusätzlich oder alternativ hochreiner gasförmiger Sauerstoff oberhalb des Kolonnensumpfes über eine Leitung 26 entnommen werden.In the ultrapure oxygen column 23, which is operated at a temperature of -179 ° C and a pressure of 1.5 bar, nitrogen and argon are separated from the oxygen and removed as a gaseous residual fraction via a line 24 from the top and above the removal point of the liquid fraction 22 fed back into the crude argon column 10 or above the line 17 into the column 6 (dashed line 42). High-purity liquid oxygen with a purity of 99.999% is removed from the bottom of the ultrapure oxygen column 23 via a line 25. The oxygen typically has the following impurities: hydrocarbons, krypton, xenon, nitrogen each less than 1 ppm, argon less than 10 ppm. The high-purity liquid oxygen is subcooled in the heat exchanger 5 and then removed from the system. If necessary, in addition or alternatively, high-purity gaseous oxygen above the Column sump can be removed via a line 26.

Die Beheizung des Kolonnensumpfes erfolgt durch Stickstoff, der vom Kopf der ersten Stufe 2 entnommen und über eine Leitung 27 einem im Kolonnensumpf angeordneten Kondensator-Verdampfer 28 zugeführt wird. Bei dem Wärmetausch kondensiert der Stickstoff und wird über eine Leitung 29 wieder in den Kopf der ersten Stufe 2 zurückgeleitet. Ein Teil des gasförmigen Stickstoffs wird von der Leitung 27 abgezweigt und über eine Leitung 30 entnommen.The column sump is heated by nitrogen, which is removed from the top of the first stage 2 and fed via a line 27 to a condenser-evaporator 28 arranged in the column sump. During the heat exchange, the nitrogen condenses and is returned to the head of the first stage 2 via a line 29. Part of the gaseous nitrogen is branched off from line 27 and removed via line 30.

Figur 2 zeigt eine Abwandlung der Verfahrens der Figur 1. Da der größte Teil des abgewandelten Verfahrens mit dem der Figur 1 identisch ist, ist in Figur 2 lediglich die Reinstsauerstoffkolonne 23 dargestellt.FIG. 2 shows a modification of the method of FIG. 1. Since the major part of the modified method is identical to that of FIG. 1, only the ultrapure oxygen column 23 is shown in FIG.

Die Entnahme des flüssigen hochreinen Sauerstoffs über Leitung 25 beziehungsweise des gasförmigen hochreinen Sauerstoffs über Leitung 26 erfolgt hier einige Böden oberhalb des Sumpfes. Die vorzugsweise drei bis fünf Rektifizierböden halten unerwünschte Anteile wie Krypton, Xenon und Kohlenwasserstoffe zurück, die durch Anreichern von Spuren oder durch Eindringen durch weniger dichte Stelle am Kondensator-Verdampfer 28 in den Sumpf der Reinstsauerstoffkolonne 23 gelangen können.The removal of the liquid high-purity oxygen via line 25 or the gaseous high-purity oxygen via line 26 takes place here some floors above the sump. The preferably three to five rectification trays retain undesirable fractions such as krypton, xenon and hydrocarbons, which can get into the bottom of the ultrapure oxygen column 23 by enriching traces or by penetrating through a less dense point on the condenser-evaporator 28.

Leitung 43 dient zum Abführen einer kleinen Menge Sumpfflüssigkeit, die entweder verworfen oder in die zweite Rektifizierstufe zurückgeleitet wird. Auf diese Weise kann die Anreicherung von unerwünschten Anteilen im Sumpf der Reinstsauerstoffkolonne 23 weitgehend verhindert werden.Line 43 is used to discharge a small amount of bottom liquid, which is either discarded or returned to the second rectification stage. In this way, the accumulation of undesirable fractions in the bottom of the ultrapure oxygen column 23 can be largely prevented.

Figur 3 zeigt eine weitere Ausführungsform des erfindungsgemäßen Verfahrens, bei dem hochreiner Stickstoff erzeugt wird. Analoge Anlagenteile sind mit denselben Bezugszeichen wie in Figur 1 versehen.FIG. 3 shows a further embodiment of the method according to the invention, in which high-purity nitrogen is generated. Analog system parts are provided with the same reference numerals as in Figure 1.

Gasförmiger Stickstoff aus dem Kopf der ersten Rektifizierstufe 2 wird über Leitung 27 in eine Reinststickstoffkolonne 31, die etwa beim gleichen Druck wie die erste Rektifizierstufe betrieben wird, eingespeist und dort in eine flüssige Sumpffraktion und in eine Restgasfraktion getrennt. Die Restgasfraktion enthält unerwünschte Anteile wie Helium, Neon und Kohlenmonoxid und wird über Leitung 33 abgezogen und der unreinen Stickstofffraktion 16 aus der zweiten Rektifizierstufe 6 beigemischt.Gaseous nitrogen from the top of the first rectification stage 2 is fed via line 27 into a high-purity nitrogen column 31, which is operated at approximately the same pressure as the first rectification stage, and is separated there into a liquid bottom fraction and a residual gas fraction. The residual gas fraction contains undesirable fractions such as helium, neon and carbon monoxide and is drawn off via line 33 and admixed with the impure nitrogen fraction 16 from the second rectification stage 6.

Die Sumpffraktion fließt über Leitung 29 zurück zur ersten Rektifizierstufe, aus der über Leitung 34 hochreiner Stickstoff abgezogen wird. Zwischen Kopfkondensator und Entnahmestelle für Leitung 34 liegen zwei bis fünf Rektifizierböden, die als Sperre für Helium, Neon und Kohlenmonoxid wirken, deren Konzentration im Kopf der Kolonne am größten ist. Der hochreine Stickstoff 34 weist eine Reinheit von 99,999% auf, der Rest besteht im wesentlichen aus Argon.The bottom fraction flows back via line 29 to the first rectification stage, from which high-purity nitrogen is withdrawn via line 34. Between the top condenser and the tapping point for line 34 there are two to five rectification trays which act as a barrier for helium, neon and carbon monoxide, the concentration of which is greatest in the top of the column. The high-purity nitrogen 34 has a purity of 99.999%, the rest consists essentially of argon.

Neben der Leitung 27 mündet eine weitere Leitung 32 in die Reinststickstoffkolonne 31. Die Leitung 32 ist unmittelbar am Kondensator 7 angeschlossen und wird auch als Heliumablaß bezeichnet. In diesem Bereich reichern sich die Luftbestandteile Helium, Neon und Kohlenmonoxid an. Diese Bestandteile werden zusammen mit dem Stickstoff über die Leitung 32 aus der Ersten Stufe 2 abgeführt und mit der Kopffraktion der Reinststickstoffkolonne 31 entnommen.In addition to the line 27, a further line 32 opens into the high-purity nitrogen column 31. The line 32 is connected directly to the condenser 7 and is also referred to as a helium drain. The air components helium, neon and carbon monoxide accumulate in this area. These constituents are removed together with the nitrogen via line 32 from the first stage 2 and removed with the top fraction of the high-purity nitrogen column 31.

Der Kopf der Reinststickstoffkolonne 31 wird mit sauerstoffreicher Flüssigkeit 46 gekühlt, die aus dem Sumpf der ersten Rektifizierstufe 2 stammt. Die sauerstoffreiche Flüssigkeit wird dabei teilweise verdampft, verläßt den Kopfkondensator der Reinststickstoffkolonne 31 über Leitung 44 beziehungsweise 45 und wird anschließend in die zweite Rektifizierstufe 6 eingeleitet.The top of the high-purity nitrogen column 31 is cooled with oxygen-rich liquid 46, which comes from the bottom of the first rectification stage 2. The oxygen-rich liquid is partially evaporated, leaves the top condenser of the high-purity nitrogen column 31 via line 44 or 45 and is then introduced into the second rectification stage 6.

Sofern der hochreine Stickstoff in flüssiger Form gewünscht wird, wird der über Leitung 34 entnommene Stickstoffe in Wärmetauscher 5 unterkühlt und anschließend entspannt. Das bei der Entspannung entstehende Flaschgas wird in einem Abscheider 35 abgetrennt und über eine Leitung 36 dem Stickstoff in Leitung 15 zugemischt. Über Leitung 37 kann flüssiger Stickstoff höchster Reinheit entnommen werden.If the high-purity nitrogen is desired in liquid form, the nitrogen removed via line 34 is subcooled in heat exchanger 5 and then expanded. The gas produced during the expansion is separated in a separator 35 and mixed with the nitrogen in line 15 via a line 36. Liquid nitrogen of the highest purity can be removed via line 37.

Sofern zusätzlich oder alternativ hochreiner Stickstoff als Gas benötigt wird, wird der hochreine flüssige Stickstoff (Leitung 38) teilweise oder ganz ohne vorherige Unterkühlung entspannt und einem Verdampfer 39 zugeführt. Der Verdampfer wird durch einen Teilstrom des gasförmigen Stickstoffs in Leitung 30 beheizt, der über eine Leitung 40 abgezweigt und nach dem Wärmetausch im Verdampfer 39 der stickstoffreichen Fraktion 4 zugemischt wird. Der hochreine gasförmige Stickstoff wird über eine Leitung 41 aus dem Verdampfer 39 abgeführt.If, in addition or as an alternative, high-purity nitrogen is required as a gas, the high-purity liquid nitrogen (line 38) is partially or completely expanded without prior cooling and fed to an evaporator 39. The evaporator is heated by a partial flow of the gaseous nitrogen in line 30, which is branched off via a line 40 and, after the heat exchange in the evaporator 39, is admixed with the nitrogen-rich fraction 4. The high-purity gaseous nitrogen is discharged from the evaporator 39 via a line 41.

Eine Ausführungsform des erfindungsgemäßen Verfahrens, bei sowohl hochreiner Sauerstoff als auch hochreiner Stickstoff hergestellt werden kann, ist in Figur 4 dargestellt. Hier sind die Reinstsauerstoffkolonne 23 und die Reinststickstoffkolonne 31 zu einer Einheit zusammengefaßt und stehen über einen nunmehr gemeinsamen Kondensator-Verdampfer 28 in wärmetauschender Verbindung. Dadurch können die Beheizung des Sumpfes der Reinstsauerstoffkolonne 27 und die Kühlung des Kopfes der Reinststickstoffsäule 31 mit Hilfe von nur einer Wärmetauschapparatur durchgeführt werden.An embodiment of the method according to the invention, in which both high-purity oxygen and high-purity nitrogen can be produced, is shown in FIG. Here the high-purity oxygen column 23 and the high-purity nitrogen column 31 are combined into one unit and are in heat-exchanging connection via a condenser-evaporator 28 now common. In this way, the heating of the bottom of the ultrapure oxygen column 27 and the cooling of the head of the ultrapure nitrogen column 31 can be carried out with the aid of only one heat exchange apparatus.

Claims (12)

1. A process for separating air by rectification in which the air is preliminarily separated into a nitrogen-rich fraction and an oxygen-rich fraction in a first rectification stage and the two fractions are fed to a second rectification stage and are separated into oxygen and nitrogen, and wherein a stream (17), fundamentally containing oxygen and argon, from the second rectification stage (6) is introduced into a crude argon column (10), characterised in that from the crude argon column (10) a further fraction (22) is discharged above the sump and is separated in a high-purity oxygen column (23) into high-purity oxygen (25, 26) and a lighter residual fraction (24).
2. A process as claimed in claim 1, characterised in that the further fraction (22) is discharged in liquid form and is fed to the high-purity oxygen column (23) as reflux liquid.
3. A process as claimed in claim 1 or claim 2, characterised in that the discharge of the further fraction (22) takes place several plates above the column sump of the crude argon column (10).
4. A process as claimed in one of claims 1 to 3, characterised in that the high-purity oxygen (25, 26) is discharged several plates above the sump of the high-purity oxygen column (23).
5. A process as claimed in one of claims 1 to 4, characterised in that the column sump of the high-purity oxygen column (23) is heated by nitrogen (27) from the head of the first rectification stage (2).
6. A device for implementing the process claimed in claim 1 comprising a two-stage rectification column and a crude argon column which is connected to the second stage of the two-stage rectification column, characterised by a high-purity oxygen column (23), the upper part of which is connected by a lateral discharge pipeline (22) to the crude argon column (10), where the lateral discharge pipeline (22) is arranged several rectification plates above the sump of the crude argon column (10).
7. A process for separating air by rectification, wherein the air is preliminarily separated in a first rectification stage into a nitrogen-rich fraction and an oxygen-rich and the two fractions are fed to a second rectification stage and are separated into oxygen and nitrogen, and wherein a further nitrogen-rich fraction (27) from the head of the first rectification stage (2) is introduced into a high-purity nitrogen column (31) and here is separated into a sump liquid (29) and a residual gas fraction (33), characterised in that the sump liquid (29) is returned to the head of the first rectification stage (2) and that a liquid fraction (34) of high-purity nitrogen is discharged a few plates below the head of the first rectification stage (2).
8. A process as claimed in claim 7, characterised in that the liquid, high-purity nitrogen (34) is at least partially supercooled.
9. A process as claimed in claim 7 or claim 7, characterised in that the liquid, high-purity nitrogen (34) is at least partially vaporised in heat exchange with condensing nitrogen (40) form the head of the first rectification stage (2).
10. A device for the implementatoin of the process claimed in one of claims 7 to 9, comprising a two-stage rectification column (3) wherien a first rectification stage (2) and a second rectification stage (6) are connected in heat-exchanging fashion via a common condenser-vaporiser (7) and comprising a high-purity nitrogen column (31), characterised in that the lower part of the high-purity nitrogen column (31) is connected by a gas pipeline (27) and a liquid pipeline (29) to the upper part of the first rectification stage (2) and that a discharge pipeline (34) for high-purity nitrogen is arranged a few plates below the head of the first rectification stage (2).
11. A process for separating air wherein the process steps from one of claims 1 to 5 and the process steps from one of claims 7 to 9 are applied jointly, characterised in that the sump liquid from the high-purity oxygen column (23) is heated by heat exchange with the gas at the head of the high-purity nitrogen column (31).
12. A device for the implementation of the process claimed in claim 11, which comprises the features of claim 6 and those of claim 10, characterised by a condenser-vaporiser (28) which is arranged between the high-purity oxygen column (23) and the high-purity nitrogen column (31).
EP88110876A 1987-07-09 1988-07-07 Process and apparatus for air separation by rectification Expired - Lifetime EP0299364B1 (en)

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US4824453A (en) 1989-04-25
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