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EP0363861B1 - Process for obtaining impure argon - Google Patents

Process for obtaining impure argon Download PDF

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Publication number
EP0363861B1
EP0363861B1 EP89118671A EP89118671A EP0363861B1 EP 0363861 B1 EP0363861 B1 EP 0363861B1 EP 89118671 A EP89118671 A EP 89118671A EP 89118671 A EP89118671 A EP 89118671A EP 0363861 B1 EP0363861 B1 EP 0363861B1
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EP
European Patent Office
Prior art keywords
air
stage
pressure
argon
raw argon
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EP89118671A
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German (de)
French (fr)
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EP0363861A3 (en
EP0363861A2 (en
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Wilhelm Rohde
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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
    • F25J3/04151—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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04006—Providing pressurised feed air or process streams within or from the air fractionation unit
    • F25J3/04078—Providing pressurised feed air or process streams within or from the air fractionation unit providing pressurized products by liquid compression and vaporisation with cold recovery, i.e. so-called internal compression
    • F25J3/04096—Providing pressurised feed air or process streams within or from the air fractionation unit providing pressurized products by liquid compression and vaporisation with cold recovery, i.e. so-called internal compression of argon or argon enriched stream
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04006—Providing pressurised feed air or process streams within or from the air fractionation unit
    • F25J3/04078—Providing pressurised feed air or process streams within or from the air fractionation unit providing pressurized products by liquid compression and vaporisation with cold recovery, i.e. so-called internal compression
    • F25J3/04103—Providing pressurised feed air or process streams within or from the air fractionation unit providing pressurized products by liquid compression and vaporisation with cold recovery, i.e. so-called internal compression using solely hydrostatic liquid head
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04284—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
    • F25J3/04406—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
    • 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
    • F25J2250/40—One fluid being air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • 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
    • F25J2250/58—One fluid being argon or crude argon
    • 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
    • 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
    • Y10S62/939—Partial feed stream expansion, air

Definitions

  • the invention relates to a process for obtaining gaseous crude argon by low-temperature rectification of air, in which air is compressed, pre-cleaned, cooled and fed to the pressure stage of a two-stage rectification and in which crude argon is obtained in the liquid state after the two-stage rectification and evaporated under increased pressure is, with a partial stream of the air being branched off before cooling, post-compressed, cooled and then partially expanded to perform the work and fed to the low-pressure stage of the rectification, work obtained during the expansion of the post-compressed air being used for post-compression.
  • WO 88/01037 shows a method of the type described in the introduction, in which crude argon is obtained in liquid form and is compressed hydrostatically.
  • a coupled compressor / turbine unit is used, in which part of the separation air is post-compressed, all of the post-compressed air in the turbine is expanded and then fed to the low-pressure stage.
  • a large part of the separation air is introduced into the low-pressure stage without pre-separation, as a result of which its rectifying effect deteriorates. This is reflected in an incompletely satisfactory cost-effectiveness of the process, especially with regard to the argon yield.
  • a method with similar raw argon production is also known from DE-A 34 28 968, in which raw argon is removed from the top of a raw argon column in liquid form or liquefied after being removed from a raw argon column.
  • the liquid raw argon experiences an increase in pressure using its hydrostatic potential in order to bring the raw argon, which is generally obtained approximately under atmospheric pressure, to the pressure of approximately 3.5 to 5 bar required for further processing.
  • This procedure offers the advantage that a machine for compressing the raw argon, which is required, for example, in the case of gaseous extraction of the raw argon, can be saved.
  • the raw argon which is under increased pressure, must be evaporated to obtain pure argon.
  • the evaporation cold is removed in the process of DE-A 34 28 968 by heat exchange with nitrogen.
  • such a process stream is not available at such a high pressure in a low-pressure system in which the air is compressed to about 6 bar that it could be liquefied against the crude argon to be evaporated at elevated pressure, so that only the heat capacity of the gaseous one Nitrogen and not its latent heat is available to dissipate the evaporative cold of the raw argon.
  • the heat exchanger for crude argon evaporation must be made relatively large.
  • the rectification is supplied with an amount of liquid which is equivalent to the amount of crude argon removed, for which additional cold has to be generated elsewhere.
  • the object of the invention is to provide an improved process of the type mentioned at the outset for obtaining gaseous crude argons under increased pressure, in which in particular a high product yield is achieved with little expenditure on energy and apparatus.
  • the invention shows two solutions to this problem.
  • part of the post-compressed air is branched off before the expansion, brought into heat exchange with the crude argon obtained in liquid form and under increased pressure, and thereby liquefied.
  • the liquefied air is fed to the pressure stage of the rectification as the return liquid.
  • it is brought into heat exchange with gas in the head of a crude argon column from which the crude argon is removed.
  • the air under increased pressure is also used to give off heat to liquid raw argon and to evaporate it in the process. Since the post-compressed air is under increased pressure, it is liquefied during the heat exchange with the evaporating raw argon. The latent heat of the air is thus also available for absorbing the evaporative cold of the crude argon, whereby on the one hand a relatively small process stream is sufficient for the evaporation and on the other hand liquid is generated which is required for the cold balance of the rectification.
  • the peak cold transferred during the evaporation of the crude argon obtained in liquid form is particularly advantageously returned to the process; on the one hand as a return liquid for the pressure stage, on the other hand for the production of liquid during rectification, especially in the crude argon column.
  • the air evaporated during the heat exchange with gas at the top of the crude argon column can be introduced into the low-pressure column.
  • the invention is explained in more detail below with reference to an exemplary embodiment schematically illustrated in the drawing.
  • the figure shows a form of the method according to the invention from sucking in the air to be broken down to evaporating and heating the crude argon, the less essential and known method steps being shown in a highly simplified manner.
  • the work steps following the crude argon evaporation for the fine cleaning of the crude argon are not shown.
  • Air is drawn in via line 1, compressed in an air compressor 2, pre-cleaned in a cleaning stage 3 - for example a molecular sieve system - and introduced through line 4 into a main heat exchanger 5, in which it is cooled in counterflow to product streams.
  • the cold air becomes the Pressure stage 7 is fed to a two-stage rectification column 6, which is operated at a pressure of 5.0 to 7.0 bar and is in heat-exchanging connection with the low-pressure stage 8 via a condenser-evaporator 9.
  • Liquid enriched with oxygen is removed from the bottom of pressure stage 7 via line 10 and throttled at a suitable point in low pressure stage 8, which is under a pressure of 1.0 to 2.0 bar. From the low-pressure stage, nitrogen (line 11) and oxygen (line 12) are led out as product streams and then warmed to almost ambient temperature in the main heat exchanger 5. In addition, a further oxygen stream, which has a relatively high argon concentration, is led out via line 13 and introduced into a crude argon column 14. Liquid also flows back from the crude argon column 14 into the low-pressure stage 8 via the same line 13.
  • the crude argon column 14 is taken as liquid crude argon product (line 15).
  • the crude argon could also be taken in whole or in part in gaseous form and then liquefied, as proposed in DE-OS 34 28 968.
  • the hydrostatic potential of approx. 30 to 40 m along the line 15 the liquid raw argon experiences a pressure increase to 3.0 to 5.0 bar, preferably approx. 4.0 bar, is evaporated in a raw argon evaporator 16, in the main heat exchanger 5 warmed to about ambient temperature and fed via line 17 to a further cleaning stage.
  • part of the air is branched off via line 18 after the preliminary cleaning (3), further compressed in a post-compressor 19 to a pressure of 7.0 to 11.0 bar, preferably 9.0 bar, in the main heat exchanger 5 to a medium one Cooled temperature and largely relaxed in a turbine 20 work and introduced into the low pressure stage 8 (line 21).
  • the turbine 20 is mechanically coupled to the post-compressor 19.
  • part of the post-compressed air is branched off via line 22 before decompression (20), passed in countercurrent to the evaporating crude argon through the crude argon evaporator 16 and at least partially liquefied and then via line 23 and throttle valve 24 as a return to the pressure stage 7 initiated.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Separation By Low-Temperature Treatments (AREA)

Description

Die Erfindung betrifft ein Verfahren zur Gewinnung von gasförmigem Rohargon durch Tieftemperaturrektifikation von Luft, bei dem Luft verdichtet, vorgereinigt, abgekühlt und der Druckstufe einer zweistufigen Rektifikation zugeführt wird und bei dem im Anschluß an die zweistufige Rektifikation Rohargon in flüssigem Zustand gewonnen und unter erhöhtem Druck verdampft wird, wobei ein Teilstrom der Luft vor dem Abkühlen abgezweigt, nachverdichtet, abgekühlt und anschließend teilweise arbeitsleistend entspannt und der Niederdruckstufe der Rektifikation zugeführt wird, wobei beim Entspannen der nachverdichteten Luft gewonnene Arbeit zur Nachverdichtung eingesetzt wird.The invention relates to a process for obtaining gaseous crude argon by low-temperature rectification of air, in which air is compressed, pre-cleaned, cooled and fed to the pressure stage of a two-stage rectification and in which crude argon is obtained in the liquid state after the two-stage rectification and evaporated under increased pressure is, with a partial stream of the air being branched off before cooling, post-compressed, cooled and then partially expanded to perform the work and fed to the low-pressure stage of the rectification, work obtained during the expansion of the post-compressed air being used for post-compression.

Die WO 88/01037 zeigt ein Verfahren der eingangs beschriebenen Art, bei dem Rohargon flüssig gewonnen und hydrostatisch komprimiert wird. Zur Erzeugung von Verfahrenskälte wird eine gekoppelte Verdichter/Turbinen-Einheit eingesetzt, bei der ein Teil der Zerlegungsluft nachverdichtet, die gesamte nachverdichtete Luft in der Turbine entspannt und anschließend der Niederdruckstufe zugeführt wird. Eine Rückgewinnung der bei der Verdampfung des flüssig gewonnenen und unter Druck stehenden Rohargons gewonnene Kälte ist nicht vorgesehen. Außerdem wird ein großer Teil der Zerlegungsluft ohne Vorzerlegung in die Niederdruckstufe eingeleitet, wodurch sich deren Rektifizierwirkung verschlechtert. Dies schlägt sich in einer nicht vollständig zufriedenstellenden Wirtschaftlichkeit des Verfahrens, insbesondere auch hinsichtlich der Argonausbeute nieder.WO 88/01037 shows a method of the type described in the introduction, in which crude argon is obtained in liquid form and is compressed hydrostatically. To generate process cooling, a coupled compressor / turbine unit is used, in which part of the separation air is post-compressed, all of the post-compressed air in the turbine is expanded and then fed to the low-pressure stage. There is no provision for recovering the cold obtained during the vaporization of the crude argon obtained in liquid form and under pressure. In addition, a large part of the separation air is introduced into the low-pressure stage without pre-separation, as a result of which its rectifying effect deteriorates. This is reflected in an incompletely satisfactory cost-effectiveness of the process, especially with regard to the argon yield.

Ein Verfahren mit ähnlicher Rohargongewinnung ist auch aus der DE-A 34 28 968 bekannt, bei dem Rohargon flüssig aus dem Kopf einer Rohargonsäule entnommen oder nach der Entnahme aus einer Rohargonsäule verflüssigt wird. Das flüssige Rohargon erfährt eine Druckerhöhung unter Ausnützung seines hydrostatischen Potentials, um das im allgemeinen ungefähr unter Atmosphärendruck gewonnene Rohargon auf den zur Weiterverarbeitung notwendigen Druck von ungefähr 3,5 bis 5 bar zu bringen. Diese Verfahrensweise bietet den Vorteil, daß eine - beispielsweise bei gasförmiger Entnahme des Rohargons benötigte - eigene Maschine zur Verdichtung des Rohargons eingespart werden kann.A method with similar raw argon production is also known from DE-A 34 28 968, in which raw argon is removed from the top of a raw argon column in liquid form or liquefied after being removed from a raw argon column. The liquid raw argon experiences an increase in pressure using its hydrostatic potential in order to bring the raw argon, which is generally obtained approximately under atmospheric pressure, to the pressure of approximately 3.5 to 5 bar required for further processing. This procedure offers the advantage that a machine for compressing the raw argon, which is required, for example, in the case of gaseous extraction of the raw argon, can be saved.

Das unter erhöhtem Druck stehende Rohargon muß für die Reinargongewinnung verdampft werden. Die Verdampfungskälte wird beim Verfahren der DE-A 34 28 968 durch Wärmetausch mit Stickstoff abgeführt. Ein solcher Prozeßstrom steht jedoch bei einer Niederdruckanlage, bei der die Luft auf etwa 6 bar verdichtet wird, nicht unter einem solch hohen Druck zur Verfügung, daß er gegen das bei erhöhtem Druck zu verdampfende Rohargon verflüssigt werden könnte, so daß lediglich die Wärmekapazität des gasförmigen Stickstoffs und nicht seine latente Wärme zum Abführen der Verdampfungskälte des Rohargons zur Verfügung steht. Dadurch muß der Wärmetauscher zur Rohargonverdampfung relativ groß ausgeführt werden. Außerdem der Rektifikation eine zur flüssig entnommenen Rohargonmenge äquivalente Menge an Flüssigkeit zugeführt werden, für die an anderer Stelle zusätzlich Kälte erzeugt werden muß.The raw argon, which is under increased pressure, must be evaporated to obtain pure argon. The evaporation cold is removed in the process of DE-A 34 28 968 by heat exchange with nitrogen. However, such a process stream is not available at such a high pressure in a low-pressure system in which the air is compressed to about 6 bar that it could be liquefied against the crude argon to be evaporated at elevated pressure, so that only the heat capacity of the gaseous one Nitrogen and not its latent heat is available to dissipate the evaporative cold of the raw argon. As a result, the heat exchanger for crude argon evaporation must be made relatively large. In addition, the rectification is supplied with an amount of liquid which is equivalent to the amount of crude argon removed, for which additional cold has to be generated elsewhere.

Aufgabe der Erfindung ist es, ein verbessertes Verfahren der eingangs genannten Art zur Gewinnung gasförmigen Rohargons unter erhöhtem Druck zur Verfügung zu stellen, bei dem insbesondere eine hohe Produktausbeute mit geringem Aufwand an Energie und Apparatur erreicht wird.The object of the invention is to provide an improved process of the type mentioned at the outset for obtaining gaseous crude argons under increased pressure, in which in particular a high product yield is achieved with little expenditure on energy and apparatus.

Die Erfindung zeigt zwei Lösungen für diese Aufgabe auf. In beiden Fällen wird ein Teil der nachverdichteten Luft vor dem Entspannen abgezweigt, in Wärmetausch mit dem flüssig gewonnenen und unter erhöhtem Druck stehenden Rohargon gebracht, und dabei verflüssigt. Die verflüssigte Luft wird im ersten Fall der Druckstufe der Rektifikation als Rücklaufflüssigkeit zugeführt. Bei der zweiten Variante der Erfindung wird sie in Wärmetausch mit Gas im Kopf einer Rohargonsäule gebracht, aus der das Rohargon entnommen wird.The invention shows two solutions to this problem. In both cases, part of the post-compressed air is branched off before the expansion, brought into heat exchange with the crude argon obtained in liquid form and under increased pressure, and thereby liquefied. In the first case, the liquefied air is fed to the pressure stage of the rectification as the return liquid. In the second variant of the invention, it is brought into heat exchange with gas in the head of a crude argon column from which the crude argon is removed.

Bei den bisher bekannten Verfahren wird die gesamte nachverdichtete Luft arbeitsleistend entspannt. Bei dem Verfahren gemaß der Erfindung wird die unter erhöhtem Druck stehende Luft auch dazu ausgenutzt, Wärme an flüssiges Rohargon abzugeben und dieses dabei zu verdampfen. Da die nachverdichtete Luft unter erhöhtem Druck steht, wird sie beim Wärmetausch mit dem verdampfenden Rohargon verflüssigt. Damit steht auch die latente Wärme der Luft für die Aufnahme der Verdampfungskälte des Rohargons zur Verfügung, wodurch einerseits ein relativ kleiner Prozeßstrom für die Verdampfung ausreicht und andererseits Flüssigkeit erzeugt wird, die für den Kältehaushalt der Rektifikation benötigt wird.In the previously known methods, all of the post-compressed air is expanded while performing work. In the method according to the invention, the air under increased pressure is also used to give off heat to liquid raw argon and to evaporate it in the process. Since the post-compressed air is under increased pressure, it is liquefied during the heat exchange with the evaporating raw argon. The latent heat of the air is thus also available for absorbing the evaporative cold of the crude argon, whereby on the one hand a relatively small process stream is sufficient for the evaporation and on the other hand liquid is generated which is required for the cold balance of the rectification.

Durch beide Arten der erfindungsgemäßen Verwendung eines Teils der nachverdichteten Luft wird die bei der Verdampfung des flüssig gewonnen Rohargons übertragene Spitzenkälte besonders vorteilhaft in das Verfahren zurückgeführt; zum einen als Rücklaufflüssigkeit für die Druckstufe, zum anderen zur Flüssigkeitserzeugung bei der Rektifikation, insbesondere in der Rohargonsäule. Die bei dem Wärmetausch mit Gas am Kopf der Rohargonsäule verdampfte Luft kann in die Niederdrucksäule eingeleitet werden.Through both types of use of part of the post-compressed air according to the invention, the peak cold transferred during the evaporation of the crude argon obtained in liquid form is particularly advantageously returned to the process; on the one hand as a return liquid for the pressure stage, on the other hand for the production of liquid during rectification, especially in the crude argon column. The air evaporated during the heat exchange with gas at the top of the crude argon column can be introduced into the low-pressure column.

Im folgenden wird die Erfindung anhand eines in der Zeichnung schematisch dargestellten Ausführungsbeispiels näher erläutert. Die Figur zeigt eine Form des erfindungsgemäßen Verfahrens vom Ansaugen der zu zerlegenden Luft bis zum Verdampfen und Anwärmen des Rohargons, wobei die weniger wesentlichen und bekannten Verfahrensschritte stark vereinfacht dargestellt sind. Die nach der Rohargonverddampfung folgenden Arbeitsschritte zur Feinreinigung des Rohargons sind nicht gezeigt.The invention is explained in more detail below with reference to an exemplary embodiment schematically illustrated in the drawing. The figure shows a form of the method according to the invention from sucking in the air to be broken down to evaporating and heating the crude argon, the less essential and known method steps being shown in a highly simplified manner. The work steps following the crude argon evaporation for the fine cleaning of the crude argon are not shown.

Luft wird über Leitung 1 angesaugt, in einem Lufterdichter 2 komprimiert, in einer Reinigungsstufe 3 - beispielsweise einer Molsiebanlage - vorgereinigt und durch Leitung 4 in einen Hauptwärmetauscher 5 eingeführt, in dem sie im Gegenstrom zu Produktströmen abgekühlt wird. Die kalte Luft wird der Druckstufe 7 einer zweistufigen Rektifiziersäule 6 zugeführt, die bei einem Druck von 5,0 bis 7,0 bar betrieben wird und über einen Kondensator-Verdampfer 9 mit der Niederdruckstufe 8 in wärmetauschender Verbindung steht.Air is drawn in via line 1, compressed in an air compressor 2, pre-cleaned in a cleaning stage 3 - for example a molecular sieve system - and introduced through line 4 into a main heat exchanger 5, in which it is cooled in counterflow to product streams. The cold air becomes the Pressure stage 7 is fed to a two-stage rectification column 6, which is operated at a pressure of 5.0 to 7.0 bar and is in heat-exchanging connection with the low-pressure stage 8 via a condenser-evaporator 9.

Aus dem Sumpf der Druckstufe 7 wird mit Sauerstoff angereicherte Flüssigkeit über Leitung 10 entnommen und an geeigneter Stelle in die Niederdruckstufe 8, die unter einem Druck von 1,0 bis 2,0 bar steht, eingedrosselt. Aus der Niederdruckstufe werden als Procuktströme Stickstoff (Leitung 11) und Sauerstoff (Leitung 12) herausgeführt und anschließend im Hauptwärmetauscher 5 auf nahezu Umgebungstemperatur angewärmt. Außerdem wird ein weiterer Sauerstoffstrom, der eine relativ hohe Argonkonzentration aufweist, über Leitung 13 heraus- und in eine Rohargonsäule 14 eingeführt. Über dieselbe Leitung 13 fließt auch Flüssigkeit von der Rohargonsäule 14 in die Niederdruckstufe 8 zurück.Liquid enriched with oxygen is removed from the bottom of pressure stage 7 via line 10 and throttled at a suitable point in low pressure stage 8, which is under a pressure of 1.0 to 2.0 bar. From the low-pressure stage, nitrogen (line 11) and oxygen (line 12) are led out as product streams and then warmed to almost ambient temperature in the main heat exchanger 5. In addition, a further oxygen stream, which has a relatively high argon concentration, is led out via line 13 and introduced into a crude argon column 14. Liquid also flows back from the crude argon column 14 into the low-pressure stage 8 via the same line 13.

Der Rohargonsäule 14 wird als Produkt flüssiges Rohargon (Leitung 15) entnommen. Das Rohargon könnte auch ganz oder teilweise gasförmigen entnommen und anschließend verflüssigt werden, wie es in der DE-OS 34 28 968 vorgeschlagen wird. Das flüssige Rohargon erfährt durch Ausnützung des hydrostatischen Potentials von ca. 30 bis 40 m entlang der Leitung 15 eine Druckerhöhung auf 3,0 bis 5,0 bar, vorzugsweise ca. 4,0 bar, wird in einem Rohargonverdampfer 16 verdampft, im Hauptwärmetauscher 5 auf etwa Umgebungstemperatur angewärmt und über Leitung 17 einer weiteren Reinigungsstufe zugeführt.The crude argon column 14 is taken as liquid crude argon product (line 15). The crude argon could also be taken in whole or in part in gaseous form and then liquefied, as proposed in DE-OS 34 28 968. By using the hydrostatic potential of approx. 30 to 40 m along the line 15, the liquid raw argon experiences a pressure increase to 3.0 to 5.0 bar, preferably approx. 4.0 bar, is evaporated in a raw argon evaporator 16, in the main heat exchanger 5 warmed to about ambient temperature and fed via line 17 to a further cleaning stage.

Erfindungsgemäß wird ein Teil der Luft nach der Vorreinigung (3) über Leitung 18 abgezweigt, in einem Nachverdichter 19 auf einen Druck von 7,0 bis 11,0 bar, vorzugsweise 9,0 bar weiter verdichet, im Hauptwärmetauscher 5 auf eine mittlere Temperatur abgekühlt und zum größten Teil in einer Turbine 20 arbeitsleistend entspannt und in die Niederdruckstufe 8 eingeführt (Leitung 21). Die Turbine 20 is mechanisch an den Nachverdichter 19 gekoppelt. Gemäß dem Hauptgedanken der Erfindung wird ein Teil der nachverdichteten Luft über Leitung 22 vor dem Entspannen (20) abgezweigt, im Gegenstrom zum verdampfenden Rohargon durch den Rohargonverdampfer 16 geführt und dabei mindestens teilweise verflüssigt und anschließend über Leitung 23 und Drosselventil 24 als Rücklauf in die Druckstufe 7 eingeleitet.According to the invention, part of the air is branched off via line 18 after the preliminary cleaning (3), further compressed in a post-compressor 19 to a pressure of 7.0 to 11.0 bar, preferably 9.0 bar, in the main heat exchanger 5 to a medium one Cooled temperature and largely relaxed in a turbine 20 work and introduced into the low pressure stage 8 (line 21). The turbine 20 is mechanically coupled to the post-compressor 19. According to the main idea of the invention, part of the post-compressed air is branched off via line 22 before decompression (20), passed in countercurrent to the evaporating crude argon through the crude argon evaporator 16 and at least partially liquefied and then via line 23 and throttle valve 24 as a return to the pressure stage 7 initiated.

Claims (3)

1. Method of obtaining gaseous raw argon by low-temperature rectification of air, in which air (1) is compressed (2), initially cleaned (3), cooled (5) and fed to the pressure stage (7) of a two-stage rectifier (6) and in which following the two-stage rectification (6) raw argon (15) is obtained in liquid state and evaporated under increased pressure, and before the cooling a part (18) of the stream of air is tapped, recompressed (19), cooled and then partially expanded (20) performing work and fed to the low-pressure stage (8) of the rectifier, and work obtained during the expansion (20) of the recompressed air is used for the recompression (19), characterised in that before the expansion (20) a part (22) of the recompressed air is tapped, brought into heat exchange (16) with the raw argon (15) obtained in liquid state and standing under increased pressure, thereby liquified and then fed to the pressure stage (7) of the rectifier as reflux liquid.
2. Method of obtaining gaseous raw argon by low-temperature rectification of air, in which air (1) is compressed (2), initially cleaned (3), cooled (5) and fed to the pressure stage (7) of a two-stage rectifier (6) and in which following the two-stage rectification (6) raw argon (15) is obtained in liquid state and evaporated under increased pressure, and before the cooling a part (18) of the stream of air is tapped, recompressed (19), cooled and then partially expanded (20) performing work and fed to the low-pressure stage (8) of the rectifier, and work obtained during the expansion (20) of the recompressed air is used for the recompression (19), characterised in that before the expansion (20) a part (22) of the recompressed air is tapped, brought into heat exchange (16) with the raw argon (15) obtained in liquid state and standing under increased pressure, thereby liquified and then brought into heat exchange with gas in the head of a raw argon column (14) from which the raw argon (15) is extracted.
3. Method as in claim 2, characterised in that the unexpanded part (22) of the recompressed air is fed to the rectifier after the heat exchange with gas in the head of the raw argon column.
EP89118671A 1988-10-12 1989-10-07 Process for obtaining impure argon Expired - Lifetime EP0363861B1 (en)

Applications Claiming Priority (2)

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DE3834793A DE3834793A1 (en) 1988-10-12 1988-10-12 METHOD FOR OBTAINING ROHARGON
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EP0363861A3 (en) 1990-06-20
CA2000595A1 (en) 1990-04-12
US4932212A (en) 1990-06-12
EP0363861A2 (en) 1990-04-18
DE3834793A1 (en) 1990-04-19
CN1052940A (en) 1991-07-10

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