EP0399197B1 - Process and apparatus for the low temperature separation of air - Google Patents

Process and apparatus for the low temperature separation of air Download PDF

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Publication number
EP0399197B1
EP0399197B1 EP90106968A EP90106968A EP0399197B1 EP 0399197 B1 EP0399197 B1 EP 0399197B1 EP 90106968 A EP90106968 A EP 90106968A EP 90106968 A EP90106968 A EP 90106968A EP 0399197 B1 EP0399197 B1 EP 0399197B1
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Prior art keywords
oxygen
pressure stage
liquid
low
nitrogen
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EP90106968A
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German (de)
French (fr)
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EP0399197A1 (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
    • F25J3/04472—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using the cold from cryogenic liquids produced within the air fractionation unit and stored in internal or intermediate storages
    • F25J3/04496—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using the cold from cryogenic liquids produced within the air fractionation unit and stored in internal or intermediate storages for compensating variable air feed or variable product demand by alternating between periods of liquid storage and liquid assist
    • F25J3/04503—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using the cold from cryogenic liquids produced within the air fractionation unit and stored in internal or intermediate storages for compensating variable air feed or variable product demand by alternating between periods of liquid storage and liquid assist by exchanging "cold" between at least two different cryogenic liquids, e.g. independently from the main heat exchange line of the air fractionation and/or by using external alternating storage systems
    • F25J3/04509—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using the cold from cryogenic liquids produced within the air fractionation unit and stored in internal or intermediate storages for compensating variable air feed or variable product demand by alternating between periods of liquid storage and liquid assist by exchanging "cold" between at least two different cryogenic liquids, e.g. independently from the main heat exchange line of the air fractionation and/or by using external alternating storage systems within the cold part of the air fractionation, i.e. exchanging "cold" within the fractionation and/or main heat exchange line
    • F25J3/04515—Simultaneously changing air feed and products output
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • 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
    • 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
    • F25J2235/00—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams
    • F25J2235/50—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams the fluid being oxygen
    • 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
    • Y10S62/912—External refrigeration system
    • Y10S62/913—Liquified gas

Definitions

  • the invention relates to a method and apparatus for the low-temperature separation of air with variable oxygen production, in which air is compressed, pre-cleaned, cooled and pre-separated in the pressure stage of a two-stage rectification into an oxygen-rich liquid fraction and a nitrogen fraction, and the oxygen-enriched liquid fraction into the low-pressure stage of the rectification , which is in heat-exchanging connection with the pressure stage, is introduced and further broken down into an oxygen and a nitrogen fraction and in which oxygen is removed from an oxygen tank when there is an increased demand for oxygen and liquid oxygen is fed from the low-pressure stage to the oxygen tank when the demand for oxygen is reduced.
  • Such a method is known for example from "LINDE reports from technology and science", 54/1984, pages 18-20.
  • the oxygen demand is subject to greater fluctuations over a period of minutes, hours or days. Because of the inertia of a low-temperature air separator, it would be uneconomical to adapt such a system by briefly changing the amount of air supplied and at the same time changing the sales in the rectification columns. Besides, one would have such a procedure has an unfavorable impact on the effectiveness of the separation process.
  • liquid oxygen is supplied to the bottom of the low-pressure stage from the oxygen tank and is evaporated there in the heat exchange with pressurized nitrogen at the top of the pressure stage. Nitrogen is liquefied during the heat exchange, removed from the pressure stage and stored in the nitrogen tank. At times when excess gaseous oxygen is produced, the stored liquid nitrogen is then available as a return in the low pressure column; Excess oxygen is removed from the bottom of the low-pressure column and stored in the oxygen tank.
  • the amount of additional oxygen that can be removed is set by the amount of pressurized nitrogen which is drawn off in gaseous form under normal load.
  • This part of the nitrogen generated in the pressure stage is generally not fed into the low-pressure stage, but is removed from the process, either directly as a gaseous product (under normal load and with reduced oxygen demand) or through intermediate storage in the nitrogen tank (with increased oxygen demand). Regardless of the current load, this amount of nitrogen is not available as a return for the low pressure stage.
  • the object of the invention is now to develop a method which enables variable oxygen production with cheaper product yields, in particular with an attached argon rectification.
  • This object is achieved in that when there is an increased oxygen requirement, the conversion in the pressure stage is increased and at least part of the oxygen-enriched liquid fraction is introduced into a liquid air tank and stored there, and in that when the oxygen requirement is reduced, the conversion in the pressure stage is reduced and oxygen-enriched liquid fraction from the liquid air tank removed and fed to the rectification.
  • the intermediate storage of sump liquid from the pressure stage according to the invention permits an operation of the system in which, on the one hand, the reflux conditions in the pressure and low pressure stage and the conversion in the low pressure stage can be kept constant, on the other hand, all nitrogen generated in the pressure stage can be withdrawn in liquid and the Low pressure stage are supplied. This provides the optimal amount of reflux for the low pressure rectification, the maximum achievable argon concentration is achieved.
  • the amount of air supplied is increased when there is an increased demand for oxygen.
  • This causes the desired increase in column turnover and thus the evaporation of the liquid additionally introduced from the oxygen tank into the sump of the low-pressure column.
  • the air supply is throttled and liquid is removed from the liquid air tank and the nitrogen tank in order to keep the sales in the low pressure column constant. Due to the lower conversion at the top of the pressure stage, a smaller part of the oxygen accumulating in the low pressure column is evaporated. The corresponding amount is drawn off in liquid form and stored in the oxygen tank.
  • the process according to the invention is advantageously controlled such that both the reflux ratio and the conversion in the low-pressure stage are kept essentially constant in the event of fluctuations in the amount of oxygen produced.
  • the return ratio also remains constant in the pressure stage.
  • an argon-containing oxygen fraction can be taken from the middle area of the low-pressure stage and in one Raw argon rectification can be broken down into raw argon and into a residual fraction.
  • the invention further relates to a device for carrying out the method described above with a two-stage rectification column which consists of a pressure column and a low pressure column with a common condenser / evaporator, a nitrogen tank which is connected to the pressure and low pressure column by means of nitrogen lines, and with an oxygen tank , which is connected to the low pressure column by means of oxygen lines.
  • the device according to the invention is characterized by a liquid air tank, a first liquid air line between the sump of the pressure column and the liquid air tank and a second liquid air line which connects the liquid air tank and the low pressure column.
  • the device has measuring devices for the liquid level in the pressure column and low-pressure column sump, a flow measuring device in the nitrogen line between the pressure column and nitrogen tank, throttle devices for controlling the flow in liquid air, oxygen and nitrogen lines and control devices which are compatible with the Measuring devices are connected and control the throttle devices.
  • the figure shows this variant of the method according to the invention in a schematic sketch.
  • Air is drawn in by an air compressor 1, then pre-cooled and cleaned (2) and passed via line 3 through a main heat exchanger 4, in which it is cooled in countercurrent to product gases. 70 to 95%, preferably 88%, of the air becomes cold End of the main heat exchanger 4 and fed via line 5 at a temperature of 95 to 105K and under a pressure of 4 to 8 bar into the pressure stage 10 of a two-stage rectification 9.
  • the remainder of the air is led out of the main heat exchanger 4 via line 6 at a temperature of 130 to 190 K, expanded to a pressure of 2.0 to 1.1 bar in an expansion turbine 7 and fed to the low pressure stage 11 of the rectification 9.
  • the air introduced via line 5 is broken down into liquid nitrogen and into an oxygen-enriched bottom liquid. Both fractions are withdrawn in liquid form, the nitrogen via line 14 and the bottom liquid via line 12.
  • the nitrogen is expanded using valve 134 and fed into a nitrogen tank which stores liquid nitrogen under a pressure of 1 to 6 bar.
  • the liquid is at least partially passed on via line 37, subcooled in a heat exchanger 23 and applied via line 15 to the top of the low-pressure stage 11.
  • the bottom liquid in line 12 is also depressurized (valve 132) and introduced into a liquid air tank 40 in which pressure conditions similar to those in the nitrogen tank 35 prevail. Liquid is removed from the tank 40 via line 42, cooled in the heat exchanger 23 and introduced into the low-pressure stage 11 via line 13b. There the oxygen-enriched liquid from pressure stage 10 is further broken down.
  • low-pressure stage 11 gaseous oxygen is taken off above the sump via line 16 and warmed to almost ambient temperature in main heat exchanger 4 (line 19).
  • nitrogen is drawn off at the top via line 18, heated in heat exchanger 23 against the liquid fractions 37 and 42 from the pressure stage 10 or from the tanks 35, 40, passed through line 19 through the main heat exchanger 4 and continues there except for im essential ambient temperature warmed.
  • liquid oxygen can be withdrawn from the bottom of the low-pressure stage 11 by means of the pump 31 and introduced into an oxygen tank 32.
  • liquid can be fed from the oxygen tank 32 into the low-pressure column 11 via line 34.
  • an argon-rich oxygen fraction is drawn off from the low pressure stage 11 via line 20, fed to a crude argon rectification 21 and there in crude argon, which is withdrawn via line 22 at the top of the crude argon rectification 21, and into one liquid residual fraction that over Line 20 flows back into the low pressure stage 11, disassembled.
  • the head of the crude argon rectification 21 is cooled by liquid from the bottom of the pressure column 10 or from the liquid air tank 40.
  • a secondary line 24 branches off from line 42 and leads into the top condenser 45 of the crude argon rectification 21.
  • the oxygen-enriched air evaporated there is drawn off via line 46 and via line 13a somewhat below the feed point of the liquid fraction (line 13b) into the low-pressure stage 11 introduced.
  • an increased flow is set on the air compressor 1.
  • the flow rate is monitored by the measuring device 125, which is connected to the air compressor 1 (line shown in broken lines in the figure).
  • the flow through line 6 via the expansion turbine 7 to the low-pressure stage 11 is kept essentially constant by controlling the flow through the expansion turbine 7 in accordance with the values indicated by the measuring device 127 (see dashed line in the drawing).
  • the amount of air additionally sucked in by the air compressor 1 is thus practically completely introduced into the pressure stage 10 and increases the column turnover there. For example, to remove a 25% increase in the amount of gaseous product oxygen, the total amount of air must be increased by approximately 6.8%.
  • the increased conversion in the pressure stage 10 now causes an increased heat input via the condenser / evaporator 48 into the bottom of the low pressure stage 11.
  • the additionally evaporated oxygen can be drawn off via line 16 as an increased amount of product. This process is controlled by the flow meter 126 and valve 136 in line 17.
  • a quantity of liquid oxygen corresponding to the additionally removed oxygen gas is removed from the oxygen tank 32 (line 34).
  • the replenishment of liquid oxygen is controlled by means of the liquid level measurement 123 at the bottom of the low pressure stage 11 and the valve 133.
  • the pressure in the liquid tanks 32, 35, 40 is monitored by means of measuring devices 101, 102, 103. If necessary, gas is released from tanks 32, 35, 40 by opening valves 111, 112 and 113, from liquid air tank 40 via lines 41 and 13a to the low pressure stage, from oxygen tank 32 via line 33 into product line 17 and from the nitrogen tank 35 via line 36 into the product line 19.

Abstract

A process and apparatus for the low-temperature separation of air with variable oxygen production are described. Compressed, pre-purified and cool air (line 5) is pre-separated in the pressure stage 10 of a two-stage rectification 9. The bottom liquid thus formed is further separated in the low-pressure stage 11. Liquid nitrogen 14 from the pressure stage 10 and liquid oxygen from the low-pressure stage 11 can be temporarily stored in tanks 35, 32. In addition, a liquid-air tank 14 is provided for storing bottom liquid 12 from the pressure stage 10. If the production of oxygen is increased, the throughput in the pressure stage 10 can be increased and at the same time the throughput in the low-pressure stage 11 and the reflux ratios in the two rectification stages 10, 11 can be kept constant.

Description

Die Erfindung betrifft ein Verfahren und Vorrichtung zur Tieftemperaturzerlegung von Luft mit variabler Sauerstoffproduktion, bei denen Luft verdichtet, vorgereinigt, abgekühlt und in der Druckstufe einer zweistufigen Rektifikation in eine sauerstoffreiche flüssige Fraktion und in eine Stickstofffraktion vorzerlegt und die sauerstoffangereicherte flüssige Fraktion in die Niederdruckstufe der Rektifikation, die mit der Druckstufe in wärmetauschender Verbindung steht, eingeleitet und weiter in eine Sauerstoff- und in eine Stickstofffraktion zerlegt wird und bei dem bei erhöhtem Sauerstoffbedarf Sauerstoff aus einem Sauerstofftank entnommen und bei erniedrigtem Sauerstoffbedarf dem Sauerstofftank flüssiger Sauerstoff aus der Niederdruckstufe zugeführt wird. Ein desartiges Verfahren ist beispielsweise aus "LINDE-Berichte aus Technik und Wissenschaft", 54/1984, Seiten 18-20 bekannt.The invention relates to a method and apparatus for the low-temperature separation of air with variable oxygen production, in which air is compressed, pre-cleaned, cooled and pre-separated in the pressure stage of a two-stage rectification into an oxygen-rich liquid fraction and a nitrogen fraction, and the oxygen-enriched liquid fraction into the low-pressure stage of the rectification , which is in heat-exchanging connection with the pressure stage, is introduced and further broken down into an oxygen and a nitrogen fraction and in which oxygen is removed from an oxygen tank when there is an increased demand for oxygen and liquid oxygen is fed from the low-pressure stage to the oxygen tank when the demand for oxygen is reduced. Such a method is known for example from "LINDE reports from technology and science", 54/1984, pages 18-20.

In verschiedenen Industriezweigen unterliegt der Sauerstoffbedarf größeren Schwankungen in Zeitspannen von Minuten, Stunden oder Tagen. Wegen der Trägheit eines Tieftemperatur-Luftzerlegers wäre eine Anpassung einer solchen Anlage durch kurzzeitige Veränderung der Menge an zugeführter Luft und gleichzeitiger Änderung der Umsätze in den Rektifizierkolonnen unwirtschaftlich. Außerdem hätte eine solche Verfahrensweise ungünstige Auswirkungen auf die Effektivität des Trennprozesses.In various branches of industry, the oxygen demand is subject to greater fluctuations over a period of minutes, hours or days. Because of the inertia of a low-temperature air separator, it would be uneconomical to adapt such a system by briefly changing the amount of air supplied and at the same time changing the sales in the rectification columns. Besides, one would have such a procedure has an unfavorable impact on the effectiveness of the separation process.

Andererseits ist es ebenso ungünstig, überschüssigen Sauerstoff in Gasdruckbehältern zu speichern und diesen dann bei erhöhtem Bedarf wieder zu entnehmen. Zu diesem Zweck würden große Gasdruckbehälter und zusätzliche Verdichtungsenergie benötigt.On the other hand, it is just as unfavorable to store excess oxygen in gas pressure containers and then to remove it again when there is an increased need. Large gas pressure vessels and additional compression energy would be required for this purpose.

Aus diesen Gründen wurde ein Verfahren für eine flexible Sauerstoffproduktion entwickelt, bei dem Zerlegungsprodukte in flüssigem Zustand der Rektifikation entnommen und in Flüssigtanks zu speichern. Ein solches Verfahren mit je einem Behälter für Sauerstoff und Stickstoff ist aus den Linde-Berichten aus Technik und Wissenschaft Nr. 54/1984, Seiten 18 bis 20 bekannt.For these reasons, a process for flexible oxygen production has been developed in which decomposition products in the liquid state are removed from the rectification and stored in liquid tanks. Such a method, each with a container for oxygen and nitrogen, is known from the Linde Reports from Technology and Science No. 54/1984, pages 18 to 20.

Bei dem vorveröffentlichten Verfahren wird während der Zeit, in der mehr gasförmiger Sauerstoff benötigt wird, als der Apparat aufgrund der eingebrachten Luftmenge erzeugen kann, dem Sumpf der Niederdruckstufe flüssiger Sauerstoff aus dem Sauerstofftank zugeführt und dort im Wärmeaustausch mit Druckstickstoff am Kopf der Druckstufe verdampft. Stickstoff wird bei dem Wärmeaustausch verflüssigt, der Druckstufe entnommen und im Stickstofftank gespeichert. In Zeiten, in denen überschüssiger gasförmiger Sauerstoff anfällt, steht dann der gespeicherte flüssige Stickstoff als Rücklauf in der Niederdrucksäule zur Verfügung; überschüssiger Sauerstoffs wird dem Sumpf der Niederdrucksäule flüssig entnommen und im Sauerstofftank gespeichert.In the previously published method, during the time in which more gaseous oxygen is required than the apparatus can generate due to the amount of air introduced, liquid oxygen is supplied to the bottom of the low-pressure stage from the oxygen tank and is evaporated there in the heat exchange with pressurized nitrogen at the top of the pressure stage. Nitrogen is liquefied during the heat exchange, removed from the pressure stage and stored in the nitrogen tank. At times when excess gaseous oxygen is produced, the stored liquid nitrogen is then available as a return in the low pressure column; Excess oxygen is removed from the bottom of the low-pressure column and stored in the oxygen tank.

Bei dem bekannten Verfahren mit Wechselspeicherung mittels zwei Flüssigkeitstanks bleibt die zerlegte Luftmenge immer konstant. Man erreicht damit einen stationären Betrieb der Rektifikation sowohl in der Druck- als auch in der Niederdruckstufe.In the known method with exchangeable storage by means of two liquid tanks, the air volume split always remains constant. This achieves stationary operation of the rectification in both the pressure and the low pressure stage.

Bei erhöhtem Sauerstoffbedarf ist es jedoch notwendig, am Kopf der Druckstufe gasförmigen Stickstoff zur Verfügung zu haben, um damit flüssigen Sauerstoff im Sumpf der Niederdruckstufe verdampfen und anschließend als gasförmiges Produkt entnehmen zu können. Aus diesem Grund muß bei Normallast eine gewisse Menge gasförmiger Druckstickstoff entnommen werden, um konstante Säulenumsätze einhalten zu können. Diese bei Normallastbetrieb entnommene Druckstickstoffmenge steht dann bei erhöhtem Sauerstoffbedarf zum Verdampfen von Sauerstoff zu Verfügung. Sie beeinflußt aber nicht die Rektifikation, da einerseits am Kopf der Drucksäule verflüssigter Stickstoff und andererseits vom Sumpf der Niederdrucksäule verdampfender Sauerstoff sofort abgezogen werden und nicht am jeweiligen Säulenumsatz teilnehmen. Der zusätzlich anfallende flüssige Stickstoff wird im Stickstofftank gespeichert, der verdampfte Sauerstoff ist das gewünschte zusätzliche Produkt.If there is an increased need for oxygen, however, it is necessary to have gaseous nitrogen available at the top of the pressure stage in order to vaporize liquid oxygen in the bottom of the low pressure stage and then to be able to take it off as a gaseous product. For this reason, a certain amount of gaseous pressurized nitrogen must be removed at normal load in order to maintain constant column sales. This amount of pressurized nitrogen withdrawn during normal load operation is then available to evaporate oxygen when there is an increased demand for oxygen. However, it does not affect the rectification, since on the one hand liquefied nitrogen at the top of the pressure column and on the other hand oxygen evaporating from the bottom of the low-pressure column are immediately withdrawn and do not participate in the respective column turnover. The additional liquid nitrogen is stored in the nitrogen tank, the vaporized oxygen is the desired additional product.

Die Menge an zusätzlich entnehmbarem Sauerstoff, also die Schwankungsbreite der Produktmenge, wird durch die Menge an im Normallastfall gasförmig abgezogenem Druckstickstoff eingestellt. Dieser Teil des in der Druckstufe erzeugten Stickstoffs wird grundsätzlich nicht auf die Niederdruckstufe aufgegeben, sondern aus dem Verfahren entnommen, entweder direkt als gasförmiges Produkt (im Normallastfall und bei erniedrigtem Sauerstoffbedarf) oder durch Zwischenspeicherung im Stickstofftank (bei erhöhtem Sauerstoffbedarf). Unabhängig von der momentan gefahrenen Last steht diese Stickstoffmenge also nicht als Rücklauf für die Niederdruckstufe zur Verfügung.The amount of additional oxygen that can be removed, that is to say the fluctuation range of the product amount, is set by the amount of pressurized nitrogen which is drawn off in gaseous form under normal load. This part of the nitrogen generated in the pressure stage is generally not fed into the low-pressure stage, but is removed from the process, either directly as a gaseous product (under normal load and with reduced oxygen demand) or through intermediate storage in the nitrogen tank (with increased oxygen demand). Regardless of the current load, this amount of nitrogen is not available as a return for the low pressure stage.

Dieser Mangel an Rücklauf wirkt sich ungünstig auf die Rektifikation in der Niederdruckstufe aus. Diese Auswirkungen sind besonders gravierend, wenn im Anschluß an die Luftzerlegung Argon gewonnen werden soll. Zu diesem Zweck erfolgt ein Anstich in der Niederdruckstufe an einer Stelle erhöhter Argonkonzentration, dem sogenannten Argonbauch. Die Ausbildung dieses Argonbauches hängt allerdings stark vom Rücklaufverhältnis ab. Die Argonkonzentration an dieser Stelle und damit die mögliche Argonausbeute sinken, wenn weniger als die gesamte in der Druckstufe erzeugte Stickstoffmenge flüssig auf die Niederdruckstufe aufgegeben wird. Deshalb sind die Rektifikationsverhältnisse in der Niederdrucksäule und speziell die Argonausbeute bei dem vorbekannten Verfahren zur variablen Sauerstoffgewinnung nicht zufriedenstellend, und zwar umso mehr, je größer die Schwankungsbreite der Sauerstoffproduktion eingestellt wird.This lack of reflux has an adverse effect on rectification in the low pressure stage. These effects are particularly serious if argon is to be obtained after the air separation. To this end there is a tapping in the low pressure stage at a point of increased argon concentration, the so-called argon belly. The formation of this argon belly depends strongly on the reflux ratio. The argon concentration at this point and thus the possible argon yield decrease if less than the total amount of nitrogen generated in the pressure stage is applied to the low pressure stage in liquid form. Therefore, the rectification ratios in the low-pressure column and especially the argon yield in the previously known method for variable oxygen production are unsatisfactory, and the more so the greater the range of fluctuation in oxygen production is set.

Aufgabe der Erfindung ist nun, ein Verfahren zu entwickeln, das eine variable Sauerstoffgewinnung mit günstigeren Produktausbeuten, insbesondere bei einer angeschlossenen Argonrektifikation, ermöglicht.The object of the invention is now to develop a method which enables variable oxygen production with cheaper product yields, in particular with an attached argon rectification.

Diese Aufgabe wird dadurch gelöst, daß bei erhöhtem Sauerstoffbedarf der Umsatz in der Druckstufe erhöht und mindestens ein Teil der sauerstoffangereicherten flüssigen Fraktion in einen Flüssiglufttank eingeführt und dort gespeichert wird und daß bei erniedrigtem Sauerstoffbedarf der Umsatz in der Druckstufe vermindert und sauerstoffangereicherte flüssige Fraktion aus dem Flüssiglufttank entnommen und der Rektifikation zugeführt wird.This object is achieved in that when there is an increased oxygen requirement, the conversion in the pressure stage is increased and at least part of the oxygen-enriched liquid fraction is introduced into a liquid air tank and stored there, and in that when the oxygen requirement is reduced, the conversion in the pressure stage is reduced and oxygen-enriched liquid fraction from the liquid air tank removed and fed to the rectification.

Die erfindungsgemäße Zwischenspeicherung von Sumpfflüssigkeit aus der Druckstufe erlaubt eine Betriebsweise der Anlage, bei der einerseits die Rücklaufverhältnisse in Druck- und Niederdruckstufe und der Umsatz in der Niederdruckstufe konstant gehalten werden kann, andererseits kann im Normallastfall der gesamte in der Druckstufe erzeugte Stickstoff flüssig abgezogen und der Niederdruckstufe zugeführt werden. Damit steht die optimale Menge an Rücklauf für die Niederdruckrektifikatlon zur Verfügung, die maximal erreichbare Argonkonzentration wird erzielt.The intermediate storage of sump liquid from the pressure stage according to the invention permits an operation of the system in which, on the one hand, the reflux conditions in the pressure and low pressure stage and the conversion in the low pressure stage can be kept constant, on the other hand, all nitrogen generated in the pressure stage can be withdrawn in liquid and the Low pressure stage are supplied. This provides the optimal amount of reflux for the low pressure rectification, the maximum achievable argon concentration is achieved.

Dies wird gemäß der Erfindung dadurch erreicht, daß zusätzlich benötigter Sauerstoff durch erhöhten Umsatz in der Druckstufe verdampft wird. Die dabei anfallende erhöhte Menge an Sumpfflüssigkeit kann in dem zusätzlichen Flüssiglufttank gespeichert werden und steht bei erniedrigtem Sauerstoffbedarf zur Einspeisung in die Niederdrucksäule wieder zur Verfügung. Der am Kopf der Drucksäule gegen verdampfenden Sauerstoff zusätzlich verflüssigte Stickstoff wird wie bei dem vorbekannten Verfahren in einen Stickstofftank abgeführt.This is achieved according to the invention in that additionally required oxygen is evaporated by increased conversion in the pressure stage. The resulting increased amount of sump liquid can be stored in the additional liquid air tank and is available for feeding into the low-pressure column when the oxygen requirement is reduced. The nitrogen additionally liquefied at the top of the pressure column against evaporating oxygen is discharged into a nitrogen tank as in the previously known method.

Zu diesem Zweck ist es günstig, wenn gemäß einem weiteren Merkmal der Erfindung bei erhöhtem Sauerstoffbedarf die zugeführte Luftmenge erhöht wird. Dies bewirkt die gewünschte Erhöhung des Säulenumsatzes und damit die Verdampfung der zusätzlich aus dem Sauerstofftank in den Sumpf der Niederdrucksäule eingeführten Flüssigkeit. Umgekehrt wird bei erniedrigtem Sauerstoffbedarf die Luftzufuhr gedrosselt und Flüssigkeit aus dem Flüssiglufttank und dem Stickstofftank entnommen, um die Umsätze in der Niederdrucksäule konstant zu halten. Durch den geringeren Umsatz am Kopf der Druckstufe wird ein geringerer Teil des in der Niederdrucksäule anfallenden Sauerstoffs verdampft. Die entsprechende Menge wird flüssig abgezogen und in dem Sauerstofftank gespeichert.For this purpose, it is advantageous if, according to a further feature of the invention, the amount of air supplied is increased when there is an increased demand for oxygen. This causes the desired increase in column turnover and thus the evaporation of the liquid additionally introduced from the oxygen tank into the sump of the low-pressure column. Conversely, when the oxygen demand is reduced, the air supply is throttled and liquid is removed from the liquid air tank and the nitrogen tank in order to keep the sales in the low pressure column constant. Due to the lower conversion at the top of the pressure stage, a smaller part of the oxygen accumulating in the low pressure column is evaporated. The corresponding amount is drawn off in liquid form and stored in the oxygen tank.

Das erfindungsgemäße Verfahren wird vorteilhafterweise so gesteuert, daß bei Schwankungen der produzierten Sauerstoffmenge sowohl das Rücklaufverhältnis als auch der Umsatz in der Niederdruckstufe im wesentlichen konstant gehalten werden. In der Druckstufe bleibt das Rücklaufverhältnis ebenfalls konstant.The process according to the invention is advantageously controlled such that both the reflux ratio and the conversion in the low-pressure stage are kept essentially constant in the event of fluctuations in the amount of oxygen produced. The return ratio also remains constant in the pressure stage.

Um neben Sauerstoff und Stickstoff auch Argon zu gewinnen, kann dem mittleren Bereich der Niederdruckstufe eine argonhaltige Sauerstofffraktion entnommen und in einer Rohargonrektifikation in Rohargon und in eine Restfratkion zerlegt werden. Mit Hilfe des erfindungsgemäßen Verfahrens ist dabei eine besonders hohe Ausbeute an Argon und damit eine sehr wirtschaftliche Verfahrensführung möglich.In order to obtain argon in addition to oxygen and nitrogen, an argon-containing oxygen fraction can be taken from the middle area of the low-pressure stage and in one Raw argon rectification can be broken down into raw argon and into a residual fraction. With the aid of the process according to the invention, a particularly high yield of argon and thus very economical process management are possible.

Die Erfindung betrifft weiterhin eine Vorrichtung zur Durchführung des oben beschriebenen Verfahrens mit einer zweistufigen Rektifizierkolonne, welche aus einer Drucksäule und einer Niederdrucksäule mit einem gemeinsamen Kondensator/Verdampfer besteht, einem Stickstofftank, der mittels Stickstoffleitungen mit Druck- und Niederdrucksäule verbunden ist, und mit einem Sauerstofftank, welcher mittels Sauerstoffleitungen mit der Niederdrucksäule verbunden ist. Die erfindungsgemäße Vorrichtung ist gekennzeichnet durch einen Flüssiglufttank, eine erste Flüssigluftleitung zwischen dem Sumpf der Drucksäule und dem Flüssiglufttank und eine zweite Flüssigluftleitung, welche Flüssiglufttank und Niederdrucksäule verbindet.The invention further relates to a device for carrying out the method described above with a two-stage rectification column which consists of a pressure column and a low pressure column with a common condenser / evaporator, a nitrogen tank which is connected to the pressure and low pressure column by means of nitrogen lines, and with an oxygen tank , which is connected to the low pressure column by means of oxygen lines. The device according to the invention is characterized by a liquid air tank, a first liquid air line between the sump of the pressure column and the liquid air tank and a second liquid air line which connects the liquid air tank and the low pressure column.

Um eine solche Vorrichtung nach dem erfindungsgemäßen Verfahren zu steuern, müssen verschiedene Parameter gemessen werden. Zu diesem Zweck ist es vorteilhaft, wenn die Vorrichtung Meßeinrichtungen für den Flüssigkeitsstand im Drucksäulen- und Niederdrucksäulensumpf, eine Durchflußmeßeinrichtung in der Stickstoffleitung zwischen Drucksäule und Stickstofftank, Drosseleinrichtungen zur Steuerung des Durchflusses in Flüssigluft-, Sauerstoff- und Stickstoffleitung und Regelungseinrichtungen aufweist, welche mit den Meßeinrichtungen verbunden sind und die Drosseleinrichtungen steuern.In order to control such a device using the method according to the invention, various parameters must be measured. For this purpose, it is advantageous if the device has measuring devices for the liquid level in the pressure column and low-pressure column sump, a flow measuring device in the nitrogen line between the pressure column and nitrogen tank, throttle devices for controlling the flow in liquid air, oxygen and nitrogen lines and control devices which are compatible with the Measuring devices are connected and control the throttle devices.

Die Erfindung und nähere Einzelheiten der Erfindung werden im folgenden anhand eines Ausführungsbeispiels näher erläutert.The invention and further details of the invention are explained below with reference to an embodiment.

Die Figur zeigt diese Variante des erfindungsgemäßen Verfahrens in einer Schemaskizze.The figure shows this variant of the method according to the invention in a schematic sketch.

Luft wird durch einen Luftverdichter 1 angesaugt, anschließend vorgekühlt und -gereinigt (2) und über Leitung 3 durch einen Hauptwärmetauscher 4 geführt, in dem sie im Gegenstrom zu Produktgasen abgekühlt wird.70 bis 95%, vorzugsweise 88% der Luft werden bis zum kalten Ende des Hauptwärmetauschers 4 geführt und über Leitung 5 mit einer Temperatur von 95 bis 105K und unter einem Druck von 4 bis 8 bar in die Druckstufe 10 einer zweistufigen Rektifikation 9 eingespeist.Air is drawn in by an air compressor 1, then pre-cooled and cleaned (2) and passed via line 3 through a main heat exchanger 4, in which it is cooled in countercurrent to product gases. 70 to 95%, preferably 88%, of the air becomes cold End of the main heat exchanger 4 and fed via line 5 at a temperature of 95 to 105K and under a pressure of 4 to 8 bar into the pressure stage 10 of a two-stage rectification 9.

Der restliche Anteil der Luft wird bei einer Temperatur von 130 bis 190 K aus dem Hauptwärmetauscher 4 über Leitung 6 herausgeführt, in einer Entspannungsturbine 7 auf einen Druck von 2,0 bis 1,1 bar entspannt und der Niederdruckstufe 11 der Rektifikation 9 zugeführt.The remainder of the air is led out of the main heat exchanger 4 via line 6 at a temperature of 130 to 190 K, expanded to a pressure of 2.0 to 1.1 bar in an expansion turbine 7 and fed to the low pressure stage 11 of the rectification 9.

In der Druckstufe 10 wird die über Leitung 5 eingeleitete Luft in flüssigen Stickstoff und in eine sauerstoffangereicherte Sumpfflüssigkeit zerlegt. Beide Fraktionen werden flüssig entnommen, der Stickstoff über Leitung 14 und die Sumpfflüssigkeit über Leitung 12. Der Stickstoff wird mit Hilfe des Ventils 134 entspannt und in einen Stickstofftank eingespeist, der flüssigen Stickstoff unter einem Druck von 1 bis 6 bar speichert. Die Flüssigkeit wird mindestens teilweise über Leitung 37 weitergeführt, in einem Wärmetauscher 23 unterkühlt und über Leitung 15 auf den Kopf der Niederdruckstufe 11 aufgegeben.In the pressure stage 10, the air introduced via line 5 is broken down into liquid nitrogen and into an oxygen-enriched bottom liquid. Both fractions are withdrawn in liquid form, the nitrogen via line 14 and the bottom liquid via line 12. The nitrogen is expanded using valve 134 and fed into a nitrogen tank which stores liquid nitrogen under a pressure of 1 to 6 bar. The liquid is at least partially passed on via line 37, subcooled in a heat exchanger 23 and applied via line 15 to the top of the low-pressure stage 11.

Die Sumpfflüssigkeit in Leitung 12 wird ebenfalls entspannt (Ventil 132 ) und in einen Flüssiglufttank 40, in dem ähnliche Druckverhältnisse wie im Stickstofftank 35 herrschen, eingeführt. Dem Tank 40 wird über Leitung 42 Flüssigkeit entnommen, im Wärmetauscher 23 abgekühlt und über Leitung 13b in die Niederdruckstufe 11 eingeführt. Dort wird die sauerstoffangereicherte Flüssigkeit aus der Druckstufe 10 weiter zerlegt.The bottom liquid in line 12 is also depressurized (valve 132) and introduced into a liquid air tank 40 in which pressure conditions similar to those in the nitrogen tank 35 prevail. Liquid is removed from the tank 40 via line 42, cooled in the heat exchanger 23 and introduced into the low-pressure stage 11 via line 13b. There the oxygen-enriched liquid from pressure stage 10 is further broken down.

Als Hauptprodukt wird der Niederdruckstufe 11 gasförmiger Sauerstoff oberhalb des Sumpfes über Leitung 16 entnommen und im Hauptwärmetauscher 4 auf nahezu Umgebungstemperatur angewärmt (Leitung 19). Als Nebenprodukt anfallender Stickstoff wird am Kopf über Leitung 18 abgezogen, in Wärmetauscher 23 gegen die flüssigen Fraktionen 37 und 42 aus der Druckstufe 10 bzw. aus den Tanks 35, 40 angewärmt, über Leitung 19 durch den Hauptwärmetauscher 4 geführt und dort weiter bis auf im wesentlichen Umgebungstemperatur erwärmt.As the main product, low-pressure stage 11 gaseous oxygen is taken off above the sump via line 16 and warmed to almost ambient temperature in main heat exchanger 4 (line 19). As a by-product, nitrogen is drawn off at the top via line 18, heated in heat exchanger 23 against the liquid fractions 37 and 42 from the pressure stage 10 or from the tanks 35, 40, passed through line 19 through the main heat exchanger 4 and continues there except for im essential ambient temperature warmed.

Über Leitung 30 kann mittels der Pumpe 31 flüssiger Sauerstoff aus dem Sumpf der Niederdruckstufe 11 abgezogen und in einen Sauerstofftank 32 eingeführt werden. In umgekehrter Richtung kann über Leitung 34 Flüssigkeit aus dem Sauerstofftank 32 in die Niederdrucksäule 11 eingespeist werden.Via line 30, liquid oxygen can be withdrawn from the bottom of the low-pressure stage 11 by means of the pump 31 and introduced into an oxygen tank 32. In the opposite direction, liquid can be fed from the oxygen tank 32 into the low-pressure column 11 via line 34.

An einer Stelle mit relativ hoher Argonkonzentration, dem "Argonbauch", wird über Leitung 20 eine argonreiche Sauerstofffraktion aus der Niederdruckstufe 11 abgezogen, einer Rohargonrektifikation 21 zugeführt und dort in Rohargon, das über Leitung 22 am Kopf der Rohargonrektifikation 21 abgezogen wird, und in eine flüssige Restfraktion, die über Leitung 20 in die Niederdruckstufe 11 zurückfließt, zerlegt.At a point with a relatively high argon concentration, the "argon belly", an argon-rich oxygen fraction is drawn off from the low pressure stage 11 via line 20, fed to a crude argon rectification 21 and there in crude argon, which is withdrawn via line 22 at the top of the crude argon rectification 21, and into one liquid residual fraction that over Line 20 flows back into the low pressure stage 11, disassembled.

Der Kopf der Rohargonrektifikation 21 wird durch Flüssigkeit aus dem Sumpf der Drucksäule 10 bzw. aus dem Flüssiglufttank 40 gekühlt. Zu diesem Zweck zweigt von Leitung 42 eine Nebenleitung 24 ab und führt in den Kopfkondensator 45 der Rohargonrektifikation 21. Die dort verdampfte sauerstoffangereicherte Luft wird über Leitung 46 abgezogen und über Leitung 13a etwas unterhalb der Einspeisestelle der flüssigen Fraktion (Leitung 13b) in die Niederdruckstufe 11 eingeführt.The head of the crude argon rectification 21 is cooled by liquid from the bottom of the pressure column 10 or from the liquid air tank 40. For this purpose, a secondary line 24 branches off from line 42 and leads into the top condenser 45 of the crude argon rectification 21. The oxygen-enriched air evaporated there is drawn off via line 46 and via line 13a somewhat below the feed point of the liquid fraction (line 13b) into the low-pressure stage 11 introduced.

Im folgenden wird nun beschrieben, auf welche Weise bei dem Verfahren des Ausführungsbeispiels die erfindungsgemäße Art des Lastwechsels vorgenommen wird. Exemplarisch sei dazu ein Umschalten von Normallast auf erhöhte Sauerstoffproduktion geschildert.The manner in which the type of load change according to the invention is carried out in the method of the exemplary embodiment is now described below. A switch from normal load to increased oxygen production is described as an example.

Wenn die über Leitung 16 entnommene Sauerstoffmenge erhöht werden soll, wird am Luftverdichter 1 ein erhöhter Durchfluß eingestellt. Die Durchflußmenge wird durch die Meßeinrichtung 125, die mit dem Luftverdichter 1 verbunden ist (in der Figur gestrichelt eingezeichnete Leitung), überwacht.If the amount of oxygen withdrawn via line 16 is to be increased, an increased flow is set on the air compressor 1. The flow rate is monitored by the measuring device 125, which is connected to the air compressor 1 (line shown in broken lines in the figure).

Der Durchfluß durch Leitung 6 über die Entspannungsturbine 7 zur Niederdruckstufe 11 wird im wesentlichen konstant gehalten, indem gemäß den von der Meßeinrichtung 127 angezeigten Werten der Durchfluß durch die Expansionsturbine 7 gesteuert wird (siehe gestrichelte Linie in der Zeichnung).The flow through line 6 via the expansion turbine 7 to the low-pressure stage 11 is kept essentially constant by controlling the flow through the expansion turbine 7 in accordance with the values indicated by the measuring device 127 (see dashed line in the drawing).

Die vom Luftverdichter 1 zusätzlich angesaugte Luftmenge wird also praktisch vollständig in die Druckstufe 10 eingeführt und erhöht dort den Säulenumsatz. Beispielsweise muß zur Entnahme einer um 25% erhöhten Menge an gasförmigem Produktsauerstoff die Gesamtluftmenge um ca. 6.8% gesteigert werden.The amount of air additionally sucked in by the air compressor 1 is thus practically completely introduced into the pressure stage 10 and increases the column turnover there. For example, to remove a 25% increase in the amount of gaseous product oxygen, the total amount of air must be increased by approximately 6.8%.

Entsprechend der zusätzlichen Luftmenge muß mehr Flüssigkeit über die Leitungen 14 und 12 abgezogen werden. Dieser Vorgang wird von den Meßeinrichtungen 124 und 122 für den Durchfluß in Leitung 14 und für den Flüssigkeitsstand in der Druckstufe 10 in Verbindung mit den Steuerventilen 132, 134 geregelt. Die über die Leitung 15 und 13b eingespeisten Flüssigkeitsmengen werden konstant gehalten (Durchflußmessungen 127, 128). Überschüssige Flüssigkeit aus der Druckstufe wird im Stickstofftank 35 bzw. im Flüssiglufttank 40 gespeichert.Depending on the additional amount of air, more liquid must be drawn off via lines 14 and 12. This process is regulated by the measuring devices 124 and 122 for the flow in line 14 and for the liquid level in the pressure stage 10 in connection with the control valves 132, 134. The quantities of liquid fed in via line 15 and 13b are kept constant (flow measurements 127, 128). Excess liquid from the pressure stage is stored in the nitrogen tank 35 or in the liquid air tank 40.

Der vergrößerte Umsatz in der Druckstufe 10 bewirkt nun einen erhöhten Wärmeeintrag über den Kondensator/Verdampfer 48 in den Sumpf der Niederdruckstufe 11. Der zusätzlich verdampfte Sauerstoff kann über Leitung 16 als erhöhte Produktmenge abgezogen werden. Dieser Vorgang wird über den Durchflußmesser 126 und Ventil 136 in Leitung 17 geregelt. Um die Rektifikation in der Niederdruckstufe 11 aufrecht zu erhalten, wird eine dem zusätzlich entnommenen Sauerstoffgas entsprechende Menge flüssigen Sauerstoffs aus dem Sauerstofftank 32 entnommen (Leitung 34). Der Nachschub an flüssigem Sauerstoff wird mittels der Flüssigkeitsstandmessung 123 am Sumpf der Niederdruckstufe 11 und des Ventils 133 geregelt.The increased conversion in the pressure stage 10 now causes an increased heat input via the condenser / evaporator 48 into the bottom of the low pressure stage 11. The additionally evaporated oxygen can be drawn off via line 16 as an increased amount of product. This process is controlled by the flow meter 126 and valve 136 in line 17. In order to maintain the rectification in the low-pressure stage 11, a quantity of liquid oxygen corresponding to the additionally removed oxygen gas is removed from the oxygen tank 32 (line 34). The replenishment of liquid oxygen is controlled by means of the liquid level measurement 123 at the bottom of the low pressure stage 11 and the valve 133.

Wenn unterdurchschnittlich viel Sauerstoff produziert werden soll, wird umgekehrt die in die Druckstufe 10 eingeführte Luftmenge verringert, zusätzlich Flüssigkeit aus dem Stickstofftank 35 und dem Flüssiglufttank 40 in die Niederdruckstufe eingeführt und Sauerstoff flüssig aus dem Sumpf der Niederdruckstufe 11 in den Sauerstofftank 32 abgeführt.Conversely, if below average oxygen production is to be produced, the amount of air introduced into the pressure stage 10 is reduced, liquid from the nitrogen tank 35 and the liquid air tank 40 is additionally introduced into the low pressure stage and liquid oxygen is discharged from the sump of the low pressure stage 11 into the oxygen tank 32.

Der Druck in den Flüssigkeitstanks 32, 35, 40 wird mittels Meßeinrichtungen 101, 102, 103 überwacht. Falls nötig, wird durch Öffnung der Ventile 111, 112 bzw. 113 Gas aus den Tanks 32, 35, 40 abgelassen, aus dem Flüssiglufttank 40 über Leitung 41 und 13a in die Niederdruckstufe, aus dem Sauerstofftank 32 über Leitung 33 in die Produktleitung 17 und aus dem Stickstofftank 35 über Leitung 36 in die Produktleitung 19.The pressure in the liquid tanks 32, 35, 40 is monitored by means of measuring devices 101, 102, 103. If necessary, gas is released from tanks 32, 35, 40 by opening valves 111, 112 and 113, from liquid air tank 40 via lines 41 and 13a to the low pressure stage, from oxygen tank 32 via line 33 into product line 17 and from the nitrogen tank 35 via line 36 into the product line 19.

Claims (5)

1. A process for the low-temperature separation of air with variable oxygen production, wherein air is compressed (1), pre-purified (2), cooled (4) and pre-separated in the pressure stage (10) of a two-stage rectification column (9) into an oxygen-rich liquid fraction (12) and into a first nitrogen fraction (14), and the oxygen-enriched, liquid fraction (12) is introduced (13a,13b) into the low-pressure stage (11) of the rectification column (9) which is coupled to the pressure stage (10) in a heat-exchanging connection (48) and is further separated into an oxygen fraction (16, 30) and a second nitrogen fraction (18), and wherein in the case of an increased oxygen requirement oxygen is withdrawn from an oxygen tank (32) and in the case of a reduced oxygen requirement liquid oxygen is supplied (30) to the oxygen tank (32) from the low-pressure stage (11), characterised in that in the case of an increased oxygen requirement the conversion rate in the pressure stage (10) is increased and at least a part of the oxygen-enriched, liquid fraction (12) is introduced into a liquid air tank (40) and stored therein and that in the case of a reduced oxygen requirement the conversion rate in the pressure stage (10) is reduced and oxygen-enriched, liquid fraction (12) is withdrawn from the liquid air tank (40) and supplied to the rectification column (9).
2. A process as claimed in Claim 1, characterised in that in the event of fluctuations in the quantity of produced oxygen, both the reflux ratio and the conversion rate in the low-pressure stage (11) are maintained substantially constant.
3. A process as claimed in Claims 1 or 2, characterised in that an oxygen fraction (20) containing argon is withdrawn from the central region of the low-pressure stage (11) and is separated into crude argon (22) and a residual fraction (20) in a crude argon rectification stage (21).
4. A device for the execution of the process claimed in one of Claims 1 to 3, comprising a two-stage rectifier column (9) composed of a pressure stage (10) and a low-pressure stage (11), with a common condenser/vaporizer (48), a nitrogen tank (35) which is connected by means of nitrogen lines (14; 37, 15) to the pressure- and low-pressure stages (10, 11), and with an oxygen tank (32) which is connected by means of oxygen lines (30, 13a, 13b) to the low-pressure stage, characterised by a liquid air tank (40), a line (12) between the sump of the pressure stage (10) and the liquid air tank (40), and a further line (41, 13a; 42, 13b) which connects the liquid air tank (40) and the low-pressure stage (11).
5. A device as claimed in Claim 4, characterised by measuring devices (122, 123) for the liquid level in the sumps of the pressure stage and the low-pressure stage, with a flow measuring device (124) in the nitrogen line (14) between the pressure stage (10) and the nitrogen tank (35), with throttling devices (132, 133, 134) for controlling the flow in the liquid air line (12), the oxygen line (30) and the nitrogen line (14), and with regulating devices which are connected to the measuring devices (122, 123, 124) and control the throttling devices (132, 133, 134).
EP90106968A 1989-04-27 1990-04-11 Process and apparatus for the low temperature separation of air Expired - Lifetime EP0399197B1 (en)

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AT90106968T ATE77687T1 (en) 1989-04-27 1990-04-11 METHOD AND DEVICE FOR THE LOW-TEMPERATURE DECOMPOSITION OF AIR.

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DE3913880A DE3913880A1 (en) 1989-04-27 1989-04-27 METHOD AND DEVICE FOR DEEP TEMPERATURE DISPOSAL OF AIR
DE3913880 1989-04-27

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EP0399197B1 true EP0399197B1 (en) 1992-06-24

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UA19155A (en) 1997-12-25
CS9002111A2 (en) 1991-08-13
HU207154B (en) 1993-03-01
JP3048373B2 (en) 2000-06-05
DE59000177D1 (en) 1992-07-30
HU902576D0 (en) 1990-08-28
JPH0363490A (en) 1991-03-19
HUT54310A (en) 1991-02-28
DE3913880A1 (en) 1990-10-31
RU1838732C (en) 1993-08-30
ZA903182B (en) 1991-04-24
ATE77687T1 (en) 1992-07-15
CA2015458C (en) 1998-09-29
EP0399197A1 (en) 1990-11-28
CA2015458A1 (en) 1990-10-27
ES2033556T3 (en) 1993-03-16
US5084081A (en) 1992-01-28
AU627869B2 (en) 1992-09-03
CZ277911B6 (en) 1993-06-16
AU5398390A (en) 1990-11-01

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