EP0904518B1 - Process for starting an installation for low temperature air separation and installation for low temperature air separation - Google Patents

Process for starting an installation for low temperature air separation and installation for low temperature air separation Download PDF

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Publication number
EP0904518B1
EP0904518B1 EP97921813A EP97921813A EP0904518B1 EP 0904518 B1 EP0904518 B1 EP 0904518B1 EP 97921813 A EP97921813 A EP 97921813A EP 97921813 A EP97921813 A EP 97921813A EP 0904518 B1 EP0904518 B1 EP 0904518B1
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EP
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Prior art keywords
liquid
distillation column
column
process according
installation
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EP97921813A
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German (de)
French (fr)
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EP0904518A1 (en
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Georg Demski
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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
    • F25J3/04478—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 controlling purposes, e.g. start-up or back-up procedures
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
    • F25J3/04254—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using the cold stored in external cryogenic fluids
    • 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
    • F25J3/0443—A main column system not otherwise provided, e.g. a modified double column flowsheet
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04763—Start-up or control of the process; Details of the apparatus used
    • F25J3/04769—Operation, control and regulation of the process; Instrumentation within the process
    • F25J3/04812—Different modes, i.e. "runs" of operation
    • F25J3/04824—Stopping of the process, e.g. defrosting or deriming; Back-up procedures
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/50—Processes or apparatus using separation by rectification using multiple (re-)boiler-condensers at different heights of the column
    • F25J2200/54—Processes or apparatus using separation by rectification using multiple (re-)boiler-condensers at different heights of the column in the low pressure column of a double pressure main column system
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/90—Details relating to column internals, e.g. structured packing, gas or liquid distribution
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/42—Nitrogen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2215/00—Processes characterised by the type or other details of the product stream
    • F25J2215/42—Nitrogen or special cases, e.g. multiple or low purity N2
    • F25J2215/44—Ultra high purity nitrogen, i.e. generally less than 1 ppb impurities
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2245/00—Processes or apparatus involving steps for recycling of process streams
    • F25J2245/42—Processes or apparatus involving steps for recycling of process streams the recycled stream being nitrogen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2250/00—Details related to the use of reboiler-condensers
    • F25J2250/30—External or auxiliary boiler-condenser in general, e.g. without a specified fluid or one fluid is not a primary air component or an intermediate fluid
    • F25J2250/42—One fluid being nitrogen
    • 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
    • F25J2280/00—Control of the process or apparatus
    • F25J2280/10—Control for or during start-up and cooling down of the installation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2290/00—Other details not covered by groups F25J2200/00 - F25J2280/00
    • F25J2290/62—Details of storing a fluid in a tank

Definitions

  • the invention relates to a method for starting up a plant for the low-temperature separation of a gas mixture, in particular air, which has at least one distillation column in which a more volatile fraction, in particular nitrogen, is produced and at least one source for cryogenic liquid, the method at least temporarily cryogenic liquid from this source is introduced into an upper region of the distillation column, this introduction of liquid starting at a time t 0 .
  • the process was developed as part of the production of nitrogen from air; however, the invention is also applicable to any other method for separation by distillation of a gas mixture at a temperature below the ambient temperature applicable. It mainly relates to restarting a system a business interruption, especially in the event that the pillar is still open low temperature, but is also due to the start of a warm system applicable.
  • the invention has for its object a particularly economical working Method and a corresponding device to specify a particular enable favorable start-up, in particular high purity in the more volatile product when restarting after business interruptions.
  • This object is achieved in that no air or essentially no air is introduced into the distillation column between the time t 0 and a later time t 1 > t 0 .
  • the air feed is opened, preferably carefully, that is, the amount of air fed in is regulated and slowly increased from zero to the normal value. It preferably rises strictly monotonously until it has reached this normal value.
  • the time t 1 can either be predetermined or determined by the fact that the liquid falling into the column has reached a certain lower column section, for example the sump, or that the liquid level in the sump of the column has reached a certain minimum height. In practice, it is sufficient if a reasonable time interval t 1 - t 0 (for example 3 to 10 minutes) is determined when the column is started up and this is used for later cases when the system is started up.
  • the Mass transfer elements in the column (floors, packing and / or ordered Packs) at least partially wetted and, if necessary, liquid distributors replenished.
  • the air is later admitted to the distillation column rectification in the entire column or in most of it immediately insert, and the more volatile fraction, which is obtained in the upper part of the column has the desired product purity.
  • the pressure in the distillation column is, for example, 3 to 15 bar, preferably 6 up to 9 bar.
  • the distillation column is designed for a nominal product quantity of the more volatile fraction. In the process, between the time t 0 and a later time t 1 > t 0 cryogenic liquid can be introduced into the distillation column in an amount which is less than the nominal product amount of the more volatile fraction.
  • the amount of liquid initially fed in is, for example, less than the nominal product amount. It can also be greater than or equal to the nominal product quantity, if this accelerates the wetting of the mass transfer elements.
  • the amount of liquid added preferably remains constant in the time interval from t 0 to t 1 and is subsequently reduced, for example to zero.
  • the column is therefore driven in particular even after the start of the air supply (time t 1 ) with total or almost total return, i.e. at least 90 mol% of the rising steam is condensed at the top of the column and at most 10 mol%, preferably at most 5 mol %, most preferably a maximum of 1 mol% of the vapor rising in the column as a volatile fraction.
  • the corresponding product line remains completely closed until time t 2 (for example 4 to 15 minutes after the start time t 0 ).
  • the time t 2 can be, for example, only about 3 to 20 minutes after the start time t 0 .
  • the amount of air supplied reaches its normal value; the removal of the more volatile fraction is increased to the nominal product quantity up to a time t 4 ⁇ t 3 .
  • the times t 3 and t 4 are, for example, 12 to 25 minutes after the start time t 0 .
  • the invention equally relates to single methods Distillation column and those with other columns. Often contains the volatile fraction from the top of the distillation column Very low boiling point contaminants. in the case of nitrogen, this can Helium, neon and / or hydrogen. That is why it is particularly high Purity requirements favorable if the more volatile fraction in the stationary Operation is initiated in a pure column, the pure column being a high purity product is removed.
  • the removal point of the high-purity product is preferably located below the introduction of the more volatile fraction. In such a process prevents the start-up method according to the invention in particular that the clean column due to less volatile components (in the case of nitrogen extraction: oxygen) is contaminated.
  • the upper region of the distillation column and the lower region of the are preferably Pure column via a condenser-evaporator in a heat-exchanging connection.
  • Such a double column is known per se from DE 4432137 A1.
  • the source of cryogenic liquid can be formed by a reservoir that is formed by is filled outside the system.
  • This reservoir can, for example, as Liquid tank to be formed, from which also in excess of the nominal product quantity additional requirements or in the event of an interruption to the plant Liquid is removed and counteracted in an external evaporator, for example Ambient air is evaporated.
  • the source of cryogenic liquid can be through a reservoir be formed, which is filled by a fluid obtained within the system. The amount of liquid consumed during start-up is then in the stationary Operation again generated and introduced into the reservoir.
  • the system has a pure column, it is particularly advantageous if that Reservoir is filled with a liquid from the pure column. This is in particular the bottom liquid of the pure column is suitable.
  • the bottom of the pure column can itself as Act as reservoir for the cryogenic liquid.
  • the reservoir is preferably through the evaporation space of the condenser-evaporator educated.
  • the condenser-evaporator can be in the bottom of the Pure column (see DE 4432137 A1) or be arranged outside the pure column. in the In the first case, the evaporation space is identical to the bottom of the column, in the second In this case, it is formed by its own container.
  • a liquid fraction from an external Source is introduced into the distillation column, as is known from DE 2417766 A is known.
  • all or substantially all Cold process requirements are covered by liquid feed, none of which Process streams is relaxed while working and the system does not generate any refrigeration Has relaxation machine (for example turbine).
  • you can this liquid fraction and the cryogenic liquid that is used when starting. be identical, i.e. come from the same reservoir.
  • One of these two reservoirs, or preferably a third can be used for emergency supply or for additional production through external evaporation be used.
  • External evaporation can, for example, by indirect Heat exchange with atmospheric air or water or with any other known method.
  • the regulation of the amount introduced to compensate for cold losses liquid fraction preferably takes place depending on the liquid level in the Bottom of the distillation column. In principle, the regulation is also dependent on other liquid levels in the system possible.
  • the method has at least a first and a second source of cryogenic liquid, cryogenic liquid from both sources being introduced into the distillation column at least at times, and the liquid from the second source from at least one theoretical base below the liquid the first source is fed.
  • the feeding of both liquids preferably begins approximately simultaneously, namely at time t 0 .
  • the simultaneous feeding of liquid at several points enables wetting of the mass transfer elements to be carried out more quickly; the air supply (time t 1 ) can start earlier, the starting process is further shortened.
  • This effect can be further enhanced by feeding liquid at three or more points on the column, for example in a packed column at each liquid distributor.
  • the different feeds can be carried out, for example, at the top and at two thirds of the column height (from below), at the top of the column and at half the column height or - in the case of three sources - at the top, at two thirds and at a third of the column height .
  • the feed quantities depend in each case on the number of theoretical plates located between the feed point and the feed point underneath or the column bottom;
  • the main criterion is the adequate wetting of the mass transfer elements that can be achieved as quickly as possible.
  • Wetting of the mass transfer elements can also be achieved if the two liquids applied in different places are the same Have composition; preferably have the liquids from the two However, sources differ in composition, particularly close to the equilibrium concentration in the distillation column in stationary operation liquid flowing down at the respective feed point. In this way can make a certain adjustment to the Concentration curve during the stationary operation of the distillation column be made. The starting process is further shortened.
  • the invention also relates to a plant for the low-temperature separation of air according to claims 15 to 17.
  • Atmospheric air is drawn in at 1, in the air compressor 2 to a pressure of over 3 bar, preferably 6.5 to 9.5 bar compressed and in one or more Cleaning stages 3, 4 of water, carbon dioxide and possibly of Free carbon monoxide and / or hydrogen by indirect heat exchange 5 cooled and via line 6 into a distillation column 7 operated as a pressure column fed.
  • the top gas 8 from the distillation column 7 is partly (9) in Condenser-evaporator 11 at least partially liquefied, the condensate 12 is given as a return to the distillation column 7 and not condensed Shares, mainly helium and neon, with a purge stream via line 13 subtracted from.
  • the gas in line 13 can for example be discarded or with a residual gas fraction are mixed. It is preferably continuously fed into the Pure column 14 described below passed by line 13 includes a valve and after this valve opens into line 10 downstream of the Dross valve there (in the drawing not shown).
  • the part of the top gas which is not introduced into the condenser-evaporator 11 Distillation column is removed as volatile fraction 10 and over a Throttle valve fed into a pure column (helium-neon discharge column) 14.
  • the Feed point is at the middle level of the pure column 14, in the lower Area of high purity nitrogen.
  • This high purity product is preferably in Vapor form taken directly above the bottom of the pure column (line 15).
  • the pure product nitrogen is used in 5 against air to be broken down to about Ambient temperature warmed up and drawn off via the product line 20.
  • the bottom of the helium-neon discharge column 14 is through the condenser-evaporator 11 heated, which also serves to form a return for the pressure column 7.
  • the head capacitor 16 of the helium-neon discharge column becomes more relaxed Bottom liquid 17 operated from the pressure column 7.
  • the against the condensing Head fraction of the helium-neon discharge column evaporated fraction is piped 19 deducted.
  • the residual gas 19 can, optionally together with an or several flushing streams, warmed against air to be separated and then for example as a regeneration gas in one or more purification stages 3, 4 be used. Parts not liquefied in the top condenser 16, in particular Helium and neon, possibly also hydrogen, leave the plant with the Purge stream 18.
  • a liquid fraction 24 for example Liquid nitrogen of ordinary purity
  • This liquid is supplied from outside the system and stored in a liquid tank.
  • This liquid tank is preferably independent of an emergency supply tank, its content to cover additional product needs or for emergency care in the Can be vaporized externally in the event of a business interruption.
  • the feed 24 preferably occurs at an intermediate point, that is, at least one theoretical floor below the head of the column.
  • the amount of imported here Liquid is, for example, a liquid level controller in the sump Distillation column 7 or depending on the liquid level in one of the Capacitors 11 or 16 set.
  • the product line 20 can alternatively or additionally externally via line 21 evaporated product fed from the emergency supply tank, not shown become.
  • To supply liquid from the emergency supply tank to start up the system can use a line from the emergency supply tank to the upper area of the Distillation column 7 may be provided.
  • the emergency supply tank can be removed from the system and / or filled from an external source. In the latter case it is Emergency supply system independent of the operation of the columns.
  • the two columns 7 and 14 can be arranged inside a vacuum insulation be, which also encloses a liquid tank, preferably the one in which the liquid fraction is stored, which is fed at 24. Details of this Arrangement can be found in EP 538857 A1.
  • the valve 23 When restarting after the interruption of operation, the valve 23 is partially or completely opened at the start time t 0 , while the air feed line 6 remains closed.
  • the liquid from the bottom of the pure column 14 flows via line 22 into the top of the distillation column 7.
  • the mass transfer elements trays, packing and / or ordered packing
  • the liquid distributors in the column 7 are gradually wetted or filled.
  • the line 6 is opened and air flows into the distillation column 7 in a quantity which slowly increases to the stationary value.
  • the gas introduced is partially or preferably completely condensed in the condenser-evaporator 11, as a result of which additional return liquid is produced.
  • the valve 23 is slowly closed, so that the amount of liquid flowing over 22 slowly decreases until it has dropped to zero at a time t 2 .
  • the liquid supply above 22 may remain open at most as long as the pressure at the top of the distillation column 7 is lower than the pressure in the bottom of the pure column 14 plus the hydrostatic pressure of the liquid. Otherwise, overhead gas would be pressed from the distillation column 7 into the pure column 14 via line 22 and contaminate it with oxygen. This can be ensured either by monitoring the corresponding pressure difference or by specifying a fixed point in time t 2 based on previously determined empirical values.
  • the entire process of restarting is preferably carried out automatically.

Abstract

An installation has at least one distillation column (7) in which a more volatile fraction (10), in particular nitrogen, is generated, as well as at least one source of refrigerated liquid. When starting the installation after an interruption, at least temporarily refrigerated liquid (22) is led from a given moment in time t0 from this source into a top area of the distillation column (7). No air (6) is introduced into the distillation column (7) between the starting moment t0 and a later moment in time t1 > t0.

Description

Die Erfindung betrifft ein Verfahren zum Anfahren einer Anlage zur Tieftemperaturzerlegung eines Gasgemischs, insbesondere von Luft, die mindestens eine Destilliersäule, in der eine leichterflüchtige Fraktion, insbesondere Stickstoff, erzeugt wird, und mindestens eine Quelle für tiefkalte Flüssigkeit aufweist, wobei bei dem Verfahren mindestens zeitweise tiefkalte Flüssigkeit aus dieser Quelle in einen oberen Bereich der Destilliersäule eingeführt wird, wobei diese Flüssigkeitseinführung zu einem Zeitpunkt t0 beginnt.The invention relates to a method for starting up a plant for the low-temperature separation of a gas mixture, in particular air, which has at least one distillation column in which a more volatile fraction, in particular nitrogen, is produced and at least one source for cryogenic liquid, the method at least temporarily cryogenic liquid from this source is introduced into an upper region of the distillation column, this introduction of liquid starting at a time t 0 .

Das Verfahren wurde im Rahmen der Gewinnung von Stickstoff aus Luft entwickelt; die Erfindung ist jedoch auch bei jedem anderen Verfahren zur destillativen Trennung eines Gasgemischs bei einer Temperatur unterhalb der Umgebungstemperatur anwendbar. Es bezieht sich hauptsächlich auf das Wiederanfahren einer Anlage nach einer Betriebsunterbrechung, insbesondere für den Fall, daß die Säule sich noch auf tiefer Temperatur befindet, ist jedoch auch auf das Anfahren einer warmen Anlage anwendbar.The process was developed as part of the production of nitrogen from air; however, the invention is also applicable to any other method for separation by distillation of a gas mixture at a temperature below the ambient temperature applicable. It mainly relates to restarting a system a business interruption, especially in the event that the pillar is still open low temperature, but is also due to the start of a warm system applicable.

Ein Verfahren der eingangs genannten Art ist aus der EP 452177 A1 bekannt. Dort wird beim Wiederanfahren der Anlage sofort eine große Menge tiefkalter Flüssigkeit, nämlich Stickstoffs, aus einem extern befüllten Flüssigtank in die Destilliersäule eingespeist; gleichzeitig wird Luft in die Säule eingeblasen. Dadurch steht sofort gasförmiges Produkt am Kopf der Säule zur Verfügung.A method of the type mentioned is known from EP 452177 A1. There If the system is restarted, a large amount of cryogenic liquid namely nitrogen, from an externally filled liquid tank into the distillation column fed; at the same time, air is blown into the column. This immediately stands gaseous product available at the top of the column.

Das leichterflüchtige Kopfprodukt weist jedoch zunächst eine relativ niedrige Reinheit auf, da anfangs fast keine Rektifikation in der Säule stattfindet.However, the more volatile top product initially has a relatively low purity because there is almost no rectification in the column at first.

Der Erfindung liegt die Aufgabe zugrunde, ein besonders wirtschaftlich arbeitendes Verfahren und eine entsprechende Vorrichtung anzugeben, die ein besonders günstiges Anfahren ermöglichen, insbesondere eine hohe Reinheit im leichterflüchtigen Produkt beim Wiederanfahren nach Betriebsunterbrechungen. The invention has for its object a particularly economical working Method and a corresponding device to specify a particular enable favorable start-up, in particular high purity in the more volatile product when restarting after business interruptions.

Diese Aufgabe wird dadurch gelöst, daß zwischen dem Zeitpunkt t0 und einem späteren Zeitpunkt t1 > t0 keine oder im wesentlichen keine Luft in die Destilliersäule eingeleitet wird.This object is achieved in that no air or essentially no air is introduced into the distillation column between the time t 0 and a later time t 1 > t 0 .

Unter dem Merkmal, daß "im wesentlichen keine Luft" in die Säule eingespeist wird, ist hier eine Einsatzluftmenge gemeint, die höchstens 20 mol%, vorzugsweise höchstens 10 mol%, höchst vorzugsweise maximal 1 mol% der Luftmenge beträgt, die die Destilliersäule im stationären Betrieb verarbeitet. Im allgemeinen ist es am günstigsten, wenn die Luftzuspeisung in die Säule zwischen den genannten Zeitpunkten vollständig versperrt ist.With the feature that "essentially no air" is fed into the column, what is meant here is an amount of feed air which is preferably at most 20 mol% is at most 10 mol%, most preferably at most 1 mol% of the amount of air which processed the distillation column in stationary operation. In general it is on cheapest if the air supply to the column between the above Times is completely blocked.

Im Zeitpunkt t1 wird die Luftzuspeisung geöffnet, und zwar vorzugsweise behutsam, das heißt die eingespeiste Luftmenge wird geregelt und dabei langsam von Null auf den Normalwert erhöht. Sie steigt dabei vorzugsweise streng monoton an, bis sie diesen Normalwert erreicht hat.At time t 1 , the air feed is opened, preferably carefully, that is, the amount of air fed in is regulated and slowly increased from zero to the normal value. It preferably rises strictly monotonously until it has reached this normal value.

Der Zeitpunkt t1 kann entweder fest vorgegeben oder dadurch bestimmt werden, daß die in der Säule herabfallende Flüssigkeit einen bestimmten unteren Säulenabschnitt erreicht hat, beispielsweise den Sumpf, oder daß der Flüssigkeitsstand im Sumpf der Säule eine gewisse Mindesthöhe erreicht hat. In der Praxis reicht es aus, wenn bei der Inbetriebnahme der Säule ein sinnvolles Zeitintervall t1 - t0 (beispielsweise 3 bis 10 Minuten) ermittelt und dieses für spätere Fälle des Anfahrens der Anlage verwendet wird.The time t 1 can either be predetermined or determined by the fact that the liquid falling into the column has reached a certain lower column section, for example the sump, or that the liquid level in the sump of the column has reached a certain minimum height. In practice, it is sufficient if a reasonable time interval t 1 - t 0 (for example 3 to 10 minutes) is determined when the column is started up and this is used for later cases when the system is started up.

Bei dem erfindungsgemäßen Verfahren werden also zunächst die Stoffaustauschelemente in der Säule (Böden, Füllkörper und/oder geordnete Packungen) mindestens teilweise benetzt und gegebenenfalls Flüssigkeitsverteiler aufgefüllt. Wenn die Luft zum späteren Zeitpunkt in die Destilliersäule eingelassen wird, kann die Rektifikation in der gesamten Säule oder in ihrem größten Teil sofort einsetzen, und die leichterflüchtige Fraktion, die im oberen Teil der Säule gewonnen wird, weist unmittelbar die gewünschte Produktreinheit auf.In the method according to the invention, the Mass transfer elements in the column (floors, packing and / or ordered Packs) at least partially wetted and, if necessary, liquid distributors replenished. When the air is later admitted to the distillation column rectification in the entire column or in most of it immediately insert, and the more volatile fraction, which is obtained in the upper part of the column has the desired product purity.

Der Druck in der Destilliersäule beträgt beispielsweise 3 bis 15 bar, vorzugsweise 6 bis 9 bar.The pressure in the distillation column is, for example, 3 to 15 bar, preferably 6 up to 9 bar.

Die Destilliersäule ist für eine Nennproduktmenge der leichterflüchtigen Fraktion ausgelegt. Bei dem Verfahren kann zwischen dem Zeitpunkt t0 und einem späteren Zeitpunkt t1 > t0 tiefkalte Flüssigkeit in einer Menge in die Destilliersäule eingeführt werden, die geringer als die Nennproduktmenge der leichterflüchtigen Fraktion ist.The distillation column is designed for a nominal product quantity of the more volatile fraction. In the process, between the time t 0 and a later time t 1 > t 0 cryogenic liquid can be introduced into the distillation column in an amount which is less than the nominal product amount of the more volatile fraction.

Vor der Einführung von Luft (Zeitpunkt t1) verdampft kaum Flüssigkeit in der Säule, sondern es werden lediglich die Stoffaustauschelemente in der Säule benetzt und gegebenenfalls Flüssigkeitsverteiler aufgefüllt. Die anfangs eingespeiste Flüssigkeitsmenge beträgt beispielsweise weniger als die Nennproduktmenge. Sie kann auch größer oder gleich der Nennproduktmenge sein, falls dadurch die Benetzung der Stoffaustauschelemente beschleunigt wird. Die zugespeiste Flüssigkeitsmenge bleibt im Zeitintervall von t0 bis t1 vorzugsweise konstant und wird anschließend reduziert, beispielsweise auf Null.Before the introduction of air (time t 1 ), hardly any liquid evaporates in the column, but only the mass transfer elements in the column are wetted and, if necessary, liquid distributors are filled up. The amount of liquid initially fed in is, for example, less than the nominal product amount. It can also be greater than or equal to the nominal product quantity, if this accelerates the wetting of the mass transfer elements. The amount of liquid added preferably remains constant in the time interval from t 0 to t 1 and is subsequently reduced, for example to zero.

Es ist besonders günstig, wenn zwischen dem Zeitpunkt t0 und einem noch späteren Zeitpunkt t2 > t1 keine oder im wesentlichen keine leichterflüchtige Fraktion aus der Destilliersäule entnommen wird.It is particularly advantageous if no or essentially no volatile fraction is removed from the distillation column between the time t 0 and an even later time t 2 > t 1 .

Die Säule wird also insbesondere auch nach dem Beginn der Luftzufuhr (Zeitpunkt t1) mit totalem oder fast totalem Rücklauf gefahren, das heißt es werden mindestens 90 mol% des aufsteigenden Dampfs am Kopf der Säule kondensiert und höchstens 10 mol%, vorzugsweise höchstens 5 mol%, höchst vorzugsweise maximal 1 mol% des in der Säule aufsteigenden Dampfs als leichterflüchtige Fraktion entnommen. Im Regelfall bleibt die entsprechende Produktleitung bis zum Zeitpunkt t2 (beispielsweise 4 bis 15 Minuten nach dem Startzeitpunkt t0) vollständig geschlossen.The column is therefore driven in particular even after the start of the air supply (time t 1 ) with total or almost total return, i.e. at least 90 mol% of the rising steam is condensed at the top of the column and at most 10 mol%, preferably at most 5 mol %, most preferably a maximum of 1 mol% of the vapor rising in the column as a volatile fraction. As a rule, the corresponding product line remains completely closed until time t 2 (for example 4 to 15 minutes after the start time t 0 ).

Dadurch kann gewährleistet werden, daß bei der Öffnung der Produktentnahmeleitung der Destilliersäule unmittelbar leichterflüchtige Fraktion in der gewünschten Reinheit vorliegt, also in derjenigen Reinheit, die auch beim stationären Betrieb der Anlage erzielt wird. Der Zeitpunkt t2 kann beispielsweise nur etwa 3 bis 20 Minuten nach dem Startzeitpunkt t0 liegen. Zu einem späteren Zeitpunkt t3 > t2 erreicht die zugeführte Luftmenge ihren Normalwert; die Entnahme der leichterflüchtigen Fraktion wird bis zu einem Zeitpunkt t4 ≥ t3 auf die Nennproduktmenge erhöht. Die Zeitpunkte t3 und t4 liegen beispielsweise 12 bis 25 Minuten nach dem Startzeitpunkt t0.This can ensure that when the product removal line of the distillation column is opened, the more readily volatile fraction is immediately present in the desired purity, that is to say in the purity which is also achieved in the stationary operation of the system. The time t 2 can be, for example, only about 3 to 20 minutes after the start time t 0 . At a later point in time t 3 > t 2 , the amount of air supplied reaches its normal value; the removal of the more volatile fraction is increased to the nominal product quantity up to a time t 4 ≥ t 3 . The times t 3 and t 4 are, for example, 12 to 25 minutes after the start time t 0 .

Die Erfindung bezieht sich gleichermaßen auf Verfahren mit einer einzelnen Destilliersäule und auf solche mit weiteren Kolonnen. Häufig enthält die leichterflüchtige Fraktion aus dem oberen Bereich der Destilliersäule noch Verunreinigungen mit sehr niedrigem Siedepunkt. im Fall von Stickstoff können dies Helium, Neon und/oder Wasserstoff sein. Deshalb ist es bei besonders hohen Reinheitsanforderungen günstig, wenn die leichterflüchtige Fraktion im stationären Betrieb in eine Reinsäule eingeleitet wird, wobei der Reinsäule ein Hochreinprodukt entnommen wird. Die Entnahmestelle des Hochreinprodukts liegt vorzugsweise unterhalb der Einleitung der leichterflüchtigen Fraktion. Bei einem derartigen Prozeß verhindert die erfindungsgemäße Anfahrmethode insbesondere, daß die Reinsäule durch schwererflüchtige Komponenten (im Falle der Stickstoffgewinnung: Sauerstoff) verunreinigt wird.The invention equally relates to single methods Distillation column and those with other columns. Often contains the volatile fraction from the top of the distillation column Very low boiling point contaminants. in the case of nitrogen, this can Helium, neon and / or hydrogen. That is why it is particularly high Purity requirements favorable if the more volatile fraction in the stationary Operation is initiated in a pure column, the pure column being a high purity product is removed. The removal point of the high-purity product is preferably located below the introduction of the more volatile fraction. In such a process prevents the start-up method according to the invention in particular that the clean column due to less volatile components (in the case of nitrogen extraction: oxygen) is contaminated.

Vorzugsweise stehen der obere Bereich der Destilliersäule und der untere Bereich der Reinsäule über einen Kondensator-Verdampfer in wärmetauschender Verbindung. Eine derartige Doppelsäule ist aus der DE 4432137 A1 an sich bekannt.The upper region of the distillation column and the lower region of the are preferably Pure column via a condenser-evaporator in a heat-exchanging connection. Such a double column is known per se from DE 4432137 A1.

Die Quelle für tiefkalte Flüssigkeit kann durch ein Reservoir gebildet werden, das von außerhalb der Anlage befüllt wird. Dieses Reservoir kann beispielsweise als Flüssigtank ausgebildet sein, aus dem außerdem bei über die Nennproduktmenge hinausgehendem Bedarf oder im Falle einer Betriebsunterbrechung der Anlage Flüssigkeit entnommen und in einem externen Verdampfer beispielsweise gegen Umgebungsluft verdampft wird.The source of cryogenic liquid can be formed by a reservoir that is formed by is filled outside the system. This reservoir can, for example, as Liquid tank to be formed, from which also in excess of the nominal product quantity additional requirements or in the event of an interruption to the plant Liquid is removed and counteracted in an external evaporator, for example Ambient air is evaporated.

Alternativ oder zusätzlich kann die Quelle für tiefkalte Flüssigkeit durch ein Reservoir gebildet werden, das durch ein innerhalb der Anlage gewonnenes Fluid befüllt wird. Die während des Anfahrens verbrauchte Flüssigkeitsmenge wird dann im stationären Betrieb wieder erzeugt und in das Reservoir eingeführt.Alternatively or additionally, the source of cryogenic liquid can be through a reservoir be formed, which is filled by a fluid obtained within the system. The amount of liquid consumed during start-up is then in the stationary Operation again generated and introduced into the reservoir.

Falls die Anlage eine Reinsäule aufweist, ist es besonders günstig, wenn das Reservoir durch eine Flüssigkeit aus der Reinsäule befüllt wird. Dazu ist insbesondere die Sumpfflüssigkeit der Reinsäule geeignet. Der Sumpf der Reinsäule kann selbst als Reservoir für die tiefkalte Flüssigkeit fungieren.If the system has a pure column, it is particularly advantageous if that Reservoir is filled with a liquid from the pure column. This is in particular the bottom liquid of the pure column is suitable. The bottom of the pure column can itself as Act as reservoir for the cryogenic liquid.

Das Reservoir wird vorzugsweise durch den Verdampfungsraum des Kondensator-Verdampfers gebildet. Der Kondensator-Verdampfer kann dabei im Sumpf der Reinsäule (siehe DE 4432137 A1) oder außerhalb der Reinsäule angeordnet sein. Im ersten Fall ist der Verdampfungsraum mit dem Sumpf der Säule identisch, im zweiten Fall wird er durch einen eigenen Behälter gebildet. The reservoir is preferably through the evaporation space of the condenser-evaporator educated. The condenser-evaporator can be in the bottom of the Pure column (see DE 4432137 A1) or be arranged outside the pure column. in the In the first case, the evaporation space is identical to the bottom of the column, in the second In this case, it is formed by its own container.

Bei derartigen Anlagen ist es günstig, wenn während des stationären Betriebs der Anlage zum Ausgleich von Kälteverlusten eine flüssige Fraktion aus einer äußeren Quelle in die Destilliersäule eingeleitet wird, wie es für sich aus der DE 2417766 A bekannt ist. Vorzugsweise wird der gesamte oder im wesentlichen der gesamte Kältebedarf der Prozesses durch Flüssigkeitszuspeisung gedeckt, wobei keiner der Prozeßströme arbeitsleistend entspannt wird und die Anlage keine kälteerzeugende Entspannungsmaschine (beispielsweise Turbine) aufweist. Grundsätzlich können diese flüssige Fraktion und die tiefkalte Flüssigkeit, die beim Anfahren eingesetzt wird. identisch sein, also aus dem gleichen Reservoir stammen. Vorzugsweise sind jedoch unterschiedliche Reservoirs für die tiefkalte Flüssigkeit, die zum Anfahren genutzt wird, und für die flüssige Fraktion, die beim stationären Betrieb die Kälteverluste ausgleicht, vorgesehen. Eines dieser beiden Reservoirs oder vorzugsweise ein drittes kann zur Notversorgung oder zu zusätzlicher Produktion durch externe Verdampfung genutzt werden. Die externe Verdampfung kann beispielsweise durch indirekten Wärmeaustausch mit atmosphärischer Luft oder Wasser oder mit jeder anderen bekannten Methode erfolgen.In such systems, it is advantageous if the System to compensate for cold losses a liquid fraction from an external Source is introduced into the distillation column, as is known from DE 2417766 A is known. Preferably all or substantially all Cold process requirements are covered by liquid feed, none of which Process streams is relaxed while working and the system does not generate any refrigeration Has relaxation machine (for example turbine). Basically you can this liquid fraction and the cryogenic liquid that is used when starting. be identical, i.e. come from the same reservoir. However, are preferred different reservoirs for the cryogenic liquid used to start up and for the liquid fraction, the cold losses during stationary operation compensates, provided. One of these two reservoirs, or preferably a third can be used for emergency supply or for additional production through external evaporation be used. External evaporation can, for example, by indirect Heat exchange with atmospheric air or water or with any other known method.

Die Regelung der Menge der zum Ausgleich von Kälteverlusten eingeführten flüssigen Fraktion erfolgt vorzugsweise in Abhängigkeit vom Flüssigkeitsstand im Sumpf der Destilliersäule. Grundsätzlich ist auch die Regelung in Abhängigkeit von anderen Flüssigkeitsständen in der Anlage möglich.The regulation of the amount introduced to compensate for cold losses liquid fraction preferably takes place depending on the liquid level in the Bottom of the distillation column. In principle, the regulation is also dependent on other liquid levels in the system possible.

Es ist ferner vorteilhaft, wenn das Verfahren mindestens eine erste und eine zweite Quelle für tiefkalte Flüssigkeit aufweist, wobei mindestens zeitweise tiefkalte Flüssigkeit aus beiden Quellen gleichzeitig in die Destilliersäule eingeführt wird, und die Flüssigkeit aus der zweiten Quelle mindestens einen theoretischen Boden unterhalb der Flüssigkeit aus der ersten Quelle eingespeist wird. Vorzugsweise beginnt die Einspeisung beider Flüssigkeiten etwa gleichzeitig, nämlich zum Zeitpunkt t0. Durch die gleichzeitige Einspeisung von Flüssigkeit an mehreren Stellen kann die Benetzung der Stoffaustauschelemente schneller durchgeführt werden; die Luftzufuhr (Zeitpunkt t1) kann früher beginnen, der Anfahrvorgang verkürzt sich weiter. Dieser Effekt kann weiter verstärkt werden, indem Flüssigkeit an drei oder mehr Stellen der Säule eingespeist wird, beispielsweise bei einer gepackten Kolonne an jedem Flüssigkeitsverteiler. Die unterschiedlichen Einspeisungen können beispielsweise am Kopf und bei zwei Dritteln der Kolonnenhöhe (von unten), am Kopf der Säule und bei der Hälfte der Kolonnenhöhe oder - im Fall von drei Quellen - am Kopf, bei zwei Dritteln und bei einem Drittel der Kolonnenhöhe vorgenommen werden. Die Einspeisemengen richten sich jeweils nach der Anzahl der zwischen der Einspeisestelle und der darunterliegenden Einspeisestelle beziehungsweise dem Kolonnensumpf liegenden theoretischen Böden; Hauptkriterium ist die möglichst rasch zu erreichende ausreichende Benetzung der Stoffaustauschelemente.It is also advantageous if the method has at least a first and a second source of cryogenic liquid, cryogenic liquid from both sources being introduced into the distillation column at least at times, and the liquid from the second source from at least one theoretical base below the liquid the first source is fed. The feeding of both liquids preferably begins approximately simultaneously, namely at time t 0 . The simultaneous feeding of liquid at several points enables wetting of the mass transfer elements to be carried out more quickly; the air supply (time t 1 ) can start earlier, the starting process is further shortened. This effect can be further enhanced by feeding liquid at three or more points on the column, for example in a packed column at each liquid distributor. The different feeds can be carried out, for example, at the top and at two thirds of the column height (from below), at the top of the column and at half the column height or - in the case of three sources - at the top, at two thirds and at a third of the column height . The feed quantities depend in each case on the number of theoretical plates located between the feed point and the feed point underneath or the column bottom; The main criterion is the adequate wetting of the mass transfer elements that can be achieved as quickly as possible.

Zwar kann eine Benetzung der Stoffaustauschelemente auch dann erreicht werden, wenn die beiden an verschiedenen Stellen aufgegebenen Flüssigkeiten dieselbe Zusammensetzung aufweisen; vorzugsweise haben die Flüssigkeiten aus den beiden Quellen jedoch eine unterschiedliche Zusammensetzung, die insbesondere nahe bei der Gleichgewichtskonzentration der in der Destilliersäule im stationären Betrieb herabfließenden Flüssigkeit an der jeweiligen Einspeisestelle liegen. Auf diese Weise kann vor der Einspeisung der Luft eine gewissen Anpassung an den Konzentrationsverlauf während des stationären Betriebs der Destilliersäule vorgenommen werden. Der Anfahrvorgang verkürzt sich weiter.Wetting of the mass transfer elements can also be achieved if the two liquids applied in different places are the same Have composition; preferably have the liquids from the two However, sources differ in composition, particularly close to the equilibrium concentration in the distillation column in stationary operation liquid flowing down at the respective feed point. In this way can make a certain adjustment to the Concentration curve during the stationary operation of the distillation column be made. The starting process is further shortened.

Die Erfindung betrifft außerdem eine Anlage zur Tieftemperaturzerlegung von Luft gemäß den Patentansprüchen 15 bis 17.The invention also relates to a plant for the low-temperature separation of air according to claims 15 to 17.

Die Erfindung sowie weitere Einzelheiten der Erfindung werden im folgenden anhand eines in der Zeichnung schematisch dargestellten Ausführungsbeispiels näher erläutert.The invention and further details of the invention are described below an embodiment shown schematically in the drawing explained.

Atmosphärische Luft wird bei 1 angesaugt, im Luftverdichter 2 auf einen Druck von über 3 bar, vorzugsweise 6.5 bis 9.5 bar komprimiert und in einer oder mehreren Reinigungsstufen 3, 4 von Wasser, Kohlendioxid und unter Umständen von Kohlenmonoxid und/oder Wasserstoff befreit, durch indirekten Wärmeaustausch 5 abgekühlt und über Leitung 6 in eine als Drucksäule betriebene Destilliersäule 7 eingespeist. Das Kopfgas 8 aus der Destilliersäule 7 wird zum einen Teil (9) im Kondensator-Verdampfer 11 mindestens teilweise verflüssigt, wobei das Kondensat 12 als Rücklauf auf die Destilliersäule 7 aufgegeben wird und nicht kondensierte Anteile, hauptsächlich Helium und Neon, mit einem Spülstrom über Leitung 13 abgezogen werden. Das Gas in Leitung 13 kann beispielsweise verworfen oder mit einer Restgasfraktion vermischt werden. Vorzugsweise wird es kontinuierlich in die unten beschriebene Reinsäule 14 geleitet, indem Leitung 13 ein Ventil enthält und nach diesem Ventil in Leitung 10 stromabwärts des dortigen Drosseiventils mündet (in der Zeichnung nicht dargestellt). Atmospheric air is drawn in at 1, in the air compressor 2 to a pressure of over 3 bar, preferably 6.5 to 9.5 bar compressed and in one or more Cleaning stages 3, 4 of water, carbon dioxide and possibly of Free carbon monoxide and / or hydrogen by indirect heat exchange 5 cooled and via line 6 into a distillation column 7 operated as a pressure column fed. The top gas 8 from the distillation column 7 is partly (9) in Condenser-evaporator 11 at least partially liquefied, the condensate 12 is given as a return to the distillation column 7 and not condensed Shares, mainly helium and neon, with a purge stream via line 13 subtracted from. The gas in line 13 can for example be discarded or with a residual gas fraction are mixed. It is preferably continuously fed into the Pure column 14 described below passed by line 13 includes a valve and after this valve opens into line 10 downstream of the Dross valve there (in the drawing not shown).

Der nicht in den Kondensator-Verdampfer 11 eingeleitete Teil des Kopfgases der Destilliersäule wird als leichterflüchtige Fraktion 10 entnommen und über ein Drosselventil in eine Reinsäule (Helium-Neon-Ausschleussäule) 14 eingespeist. Die Einspeisestelle befindet sich auf mittlerer Höhe der Reinsäule 14, in deren unterem Bereich hochreiner Stickstoff anfällt. Dieses Hochreinprodukt wird vorzugsweise in Dampfform direkt oberhalb des Sumpfes der Reinsäule entnommen (Leitung 15). Der reine Produktstickstoff wird in 5 gegen zu zerlegende Luft auf etwa Umgebungstemperatur angewärmt und über die Produktleitung 20 abgezogen.The part of the top gas which is not introduced into the condenser-evaporator 11 Distillation column is removed as volatile fraction 10 and over a Throttle valve fed into a pure column (helium-neon discharge column) 14. The Feed point is at the middle level of the pure column 14, in the lower Area of high purity nitrogen. This high purity product is preferably in Vapor form taken directly above the bottom of the pure column (line 15). The pure product nitrogen is used in 5 against air to be broken down to about Ambient temperature warmed up and drawn off via the product line 20.

Der Sumpf der Helium-Neon-Ausschleussäule 14 wird durch den Kondensator-Verdampfer 11 beheizt, der auch zur Bildung von Rücklauf für die Drucksäule 7 dient. Der Kopfkondensator 16 der Helium-Neon-Ausschleussäule wird mit entspannter Sumpfflüssigkeit 17 aus der Drucksäule 7 betrieben. Die gegen die kondensierende Kopffraktion der Helium-Neon-Ausschleussäule verdampfte Fraktion wird über Leitung 19 abgezogen. Das Restgas 19 kann, gegebenenfalls gemeinsam mit einem oder mehreren Spülströmen, gegen zu zerlegende Luft angewärmt und anschließend beispielsweise als Regeneriergas in einer oder mehreren Reinigungsstufen 3,4 eingesetzt werden. Im Kopfkondensator 16 nicht verflüssigte Anteile, insbesondere Helium und Neon, unter Umständen auch Wasserstoff, verlassen die Anlage mit dem Spülstrom 18.The bottom of the helium-neon discharge column 14 is through the condenser-evaporator 11 heated, which also serves to form a return for the pressure column 7. The head capacitor 16 of the helium-neon discharge column becomes more relaxed Bottom liquid 17 operated from the pressure column 7. The against the condensing Head fraction of the helium-neon discharge column evaporated fraction is piped 19 deducted. The residual gas 19 can, optionally together with an or several flushing streams, warmed against air to be separated and then for example as a regeneration gas in one or more purification stages 3, 4 be used. Parts not liquefied in the top condenser 16, in particular Helium and neon, possibly also hydrogen, leave the plant with the Purge stream 18.

Das Ventil 23 in einer Leitung 22, die den Sumpf der Reinsäule 14 mit dem Kopf der Destilliersäule 7 verbindet, ist im stationären Betrieb der Anlage geschlossen. Über Leitung 24 wird im stationären Betrieb eine flüssige Fraktion 24 (beispielsweise Flüssigstickstoff gewöhnlicher Reinheit) in die Säule 7 eingespeist, um den durch Isolations- und Austauschverluste bedingten Kältebedarf zu decken. Diese Flüssigkeit wird von außerhalb der Anlage zugeführt und in einem Flüssigtank gespeichert. Dieser Flüssigtank ist vorzugsweise unabhängig von einem Notversorgungstank, dessen Inhalt zur Deckung zusätzlichen Produktbedarfs oder zur Notversorgung im Falle einer Betriebsunterbrechung extern verdampft werden kann. Die Einspeisung 24 geschieht vorzugsweise an einer Zwischenstelle, das heißt mindestens einen theoretischen Boden unterhalb des Kopfs der Säule. Die Menge der hier eingeführten Flüssigkeit wird beispielsweise über einen Flüssigkeitsstandregler im Sumpf der Destilliersäule 7 oder in Abhängigkeit vom Flüssigkeitsstand in einem der Kondensatoren 11 oder 16 eingestellt. The valve 23 in a line 22, the bottom of the pure column 14 with the head of Distillation column 7 connects is closed in stationary operation of the system. about Line 24 becomes a liquid fraction 24 (for example Liquid nitrogen of ordinary purity) is fed into the column 7 to the by Insulation and exchange losses to cover the cooling requirement. This liquid is supplied from outside the system and stored in a liquid tank. This liquid tank is preferably independent of an emergency supply tank, its content to cover additional product needs or for emergency care in the Can be vaporized externally in the event of a business interruption. The feed 24 preferably occurs at an intermediate point, that is, at least one theoretical floor below the head of the column. The amount of imported here Liquid is, for example, a liquid level controller in the sump Distillation column 7 or depending on the liquid level in one of the Capacitors 11 or 16 set.

Der Produktleitung 20 kann über Leitung 21 alternativ oder zusätzlich extern verdampftes Produkt aus dem nicht dargestellten Notversorgungstank zugespeist werden. Um Flüssigkeit aus dem Notversorgungstank zum Anfahren der Anlage zu nutzen, kann eine Leitung vom Notversorgungstank in den oberen Bereich der Destilliersäule 7 vorgesehen sein. Der Notversorgungstank kann aus der Anlage und/oder aus einer externen Quelle befüllt werden. Im letzten Fall ist das Notversorgungssystem unabhängig vom Betrieb der Säulen.The product line 20 can alternatively or additionally externally via line 21 evaporated product fed from the emergency supply tank, not shown become. To supply liquid from the emergency supply tank to start up the system can use a line from the emergency supply tank to the upper area of the Distillation column 7 may be provided. The emergency supply tank can be removed from the system and / or filled from an external source. In the latter case it is Emergency supply system independent of the operation of the columns.

Die beiden Kolonnen 7 und 14 können im Inneren einer Vakuumisolierung angeordnet sein, die auch einen Flüssigtank umschließt, vorzugsweise denjenigen, in dem die flüssige Fraktion gespeichert ist, die bei 24 eingespeist wird. Einzelheiten zu dieser Anordnung sind der EP 538857 A1 zu entnehmen.The two columns 7 and 14 can be arranged inside a vacuum insulation be, which also encloses a liquid tank, preferably the one in which the liquid fraction is stored, which is fed at 24. Details of this Arrangement can be found in EP 538857 A1.

Bei einer Betriebsunterbrechung bleibt die Sumpfflüssigkeit der Reinsäule 14, ergänzt durch die von den Stoffaustauschelementen dieser Säule herabfließende Rücklaufflüssigkeit, im Sumpf der Reinsäule 14, also im Verdampfungsraum des Kondensator-Verdampfers 11, stehen; diese Flüssigkeit kann auf die erfindungsgemäße Weise zum Wiederanfahren der Anlage genutzt werden:In the event of an interruption in operation, the bottom liquid of the pure column 14 remains supplemented by the flowing down from the mass transfer elements of this column Return liquid, in the bottom of the pure column 14, that is in the evaporation chamber of the Condenser-evaporator 11, stand; this liquid can on the way according to the invention can be used to restart the system:

Beim Wiederanfahren nach der Betriebsunterbrechung wird zum Startzeitpunkt t0 das Ventil 23 teilweise oder vollständig geöffnet, während die Luftzuspeisungsleitung 6 noch geschlossen bliebt. Die Flüssigkeit aus dem Sumpf der Reinsäule 14 fließt über Leitung 22 in den Kopf der Destilliersäule 7. Die Stoffaustauschelemente (Böden, Füllkörper und/oder geordnete Packung) und gegebenenfalls die Flüssigkeitsverteiler in der Säule 7 werden nach und nach benetzt beziehungsweise gefüllt. Ab dem späteren Zeitpunkt t1 wird die Leitung 6 geöffnet und Luft strömt in langsam auf den stationären Wert ansteigender Menge in die Destilliersäule 7. Das eingeführte Gas wird teilweise oder vorzugsweise vollständig im Kondensator-Verdampfer 11 kondensiert, wodurch zusätzliche Rücklaufflüssigkeit entsteht. Etwa ab t1 wird das Ventil 23 langsam geschlossen, so daß sich die über 22 strömende Flüssigkeitsmenge langsam verringert, bis sie zu einer Zeit t2 auf Null gesunken ist. Die Flüssigkeitszufuhr über 22 darf höchstens solange geöffnet bleiben, wie der Druck am Kopf der Destilliersäule 7 geringer ist als der Druck im Sumpf der Reinsäule 14 plus dem hydrostatischen Druck der Flüssigkeit. Ansonsten würde über Leitung 22 Kopfgas aus der Destilliersäule 7 in die Reinsäule 14 gedrückt werden und diese mit Sauerstoff verunreinigen. Dies kann entweder durch die Überwachung der entsprechenden Druckdifferenz oder durch Vorgabe eines festen Zeitpunkts t2 nach vorher ermittelten Erfahrungswerten sichergestellt werden.When restarting after the interruption of operation, the valve 23 is partially or completely opened at the start time t 0 , while the air feed line 6 remains closed. The liquid from the bottom of the pure column 14 flows via line 22 into the top of the distillation column 7. The mass transfer elements (trays, packing and / or ordered packing) and, if appropriate, the liquid distributors in the column 7 are gradually wetted or filled. From the later time t 1 , the line 6 is opened and air flows into the distillation column 7 in a quantity which slowly increases to the stationary value. The gas introduced is partially or preferably completely condensed in the condenser-evaporator 11, as a result of which additional return liquid is produced. From approximately t 1 , the valve 23 is slowly closed, so that the amount of liquid flowing over 22 slowly decreases until it has dropped to zero at a time t 2 . The liquid supply above 22 may remain open at most as long as the pressure at the top of the distillation column 7 is lower than the pressure in the bottom of the pure column 14 plus the hydrostatic pressure of the liquid. Otherwise, overhead gas would be pressed from the distillation column 7 into the pure column 14 via line 22 and contaminate it with oxygen. This can be ensured either by monitoring the corresponding pressure difference or by specifying a fixed point in time t 2 based on previously determined empirical values.

Etwa ab dem Zeitpunkt t2 wird über Leitung 10 leichterflüchtiges Produkt in bis zur Nennproduktmenge ansteigendem Umfang entnommen und der Reinsäule 14 zugeleitet. Parallel dazu wird die Leitung 15 für Hochreinprodukt geöffnet.From about time t 2 , volatile product is withdrawn via line 10 to an extent increasing up to the nominal product quantity and fed to the clean column 14. In parallel, line 15 is opened for high-purity product.

Zwischen t1 und einem späteren Zeitpunkt t3 wird die Luftmenge kontinuierlich auf ihren Normalwert gesteigert. Gleichzeitig oder etwas später (t4) die durch die Leitung 10 fließende leichterflüchtige Fraktion auf die Nennproduktmenge und die Hochreinproduktmenge in Leitung 15 auf den entsprechenden Wert angestiegen. Damit ist der stationäre Betriebsfall der Anlage erreicht.Between t 1 and a later time t 3 , the amount of air is continuously increased to its normal value. Simultaneously or somewhat later (t 4 ), the more volatile fraction flowing through line 10 rose to the nominal product quantity and the high-purity product quantity in line 15 to the corresponding value. The stationary operation of the system is now achieved.

Der gesamte Ablauf des Wiederanfahrens erfolgt vorzugsweise automatisch.The entire process of restarting is preferably carried out automatically.

Claims (17)

  1. Process for starting up an installation for the low-temperature fractionation of a gas mixture, in particular air, which has at least one distillation column (7) in which a more volatile fraction (10), in particular nitrogen, is produced and at least one source of low-temperature liquid (22), in the process, at least temporarily, low-temperature liquid being introduced from this source into an upper region of the distillation column (7), this liquid introduction beginning at a time point t0, characterized in that no, or essentially no, gas mixture (6) is introduced into the distillation column (7) between the time point t0 and a later time point t1 > t0.
  2. Process according to Claim 1, characterized in that the distillation column (7) is designed for a nominal product rate of the more volatile fraction (10) and in that, between the time point t0 and a later time point t1 > t0, low-temperature liquid (22) is introduced into the distillation column at a rate which is less than the nominal product rate of the more volatile fraction (10).
  3. Process according to Claim 1 or 2, characterized in that, between the time point t0 and a still later time point t2 > t1, no, or essentially no, more volatile fraction (10) is withdrawn from the distillation column (7).
  4. Process according to one of Claims 1 to 3, characterized in that the more volatile fraction (10) is introduced into a purifying column (14), a highpurity product (15) being withdrawn from the purifying column (14).
  5. Process according to Claim 4, characterized in that the upper region of the distillation column (7) and the lower region of the purifying column (14) are in heat-exchanging connection via a condenser-evaporator (11).
  6. Process according to one of Claims 1 to 5, characterized in that the source of low-temperature liquid is formed by a reservoir which is filled from outside the installation.
  7. Process according to one of Claims 1 to 6, characterized in that the source of low-temperature liquid is formed by a reservoir which is filled by a fluid produced inside the installation.
  8. Process according to Claim 7 and according to one of Claims 4 or 5, characterized in that the reservoir is filled by a liquid from the purifying column (14).
  9. Process according to Claims 5 and 7, characterized in that the reservoir is formed by the evaporation space of the condenser-evaporator (11).
  10. Process according to one of Claims 1 to 9, characterized in that a liquid fraction (24) is introduced from an external source into the distillation column (7) during the steady state operation of the installation to compensate for refrigeration losses.
  11. Process according to Claim 10, characterized in that the flow rate of the liquid fraction (24) fed into the distillation column (7) is set as a function of the liquid level at the bottom of the distillation column (7).
  12. Process according to one of Claims 1 to 11, characterized by at least one first and one second source of low-temperature liquid, at least temporarily low-temperature liquid being introduced into the distillation column (7) from both sources simultaneously, and the liquid (24) from the second source being fed in at least one theoretical plate below the liquid (22) from the first source.
  13. Process according to Claim 12, characterized in that the liquids from the two sources have a different composition.
  14. Process according to Claim 13, characterized in that the compositions of the two liquids are close to the equilibrium concentration of the liquid flowing down in the distillation column (7) in the steady state operation at the respective feed point.
  15. Installation for the low-temperature fractionation of a gas mixture, in particular air, having at least one distillation column (7) to produce a more volatile fraction (10), in particular nitrogen, having a feed line (1, 6) which leads to the lower area of the distillation column (7), having a liquid line (22) which leads to the upper area of the distillation column (7) and having control means which are designed in such a manner that when start-up of the installation is begun, the liquid line (22) is opened and the feed line (1, 6) is completely or essentially completely closed.
  16. Installation according to Claim 15, having a gas line (10) which leads from the upper area of the distillation column (7) into a purifying column (14) and possesses a throttle valve, having a pure product line (15) which is connected to the lower area of the purifying column (14), and having a liquid line (22) which can be shut off (23), via which a flow connection can be established between the lower area of the purifying column (14) and the upper area of the first distillation column (7).
  17. Installation according to Claim 15, having a gas line (10) which leads from the upper area of the first distillation column (7) to a purifying column (14) and possesses a throttle valve, having a pure product line (15) which is connected to the lower area of the purifying column (14), having a condenser-evaporator (11), whose evaporation space is in flow-connection on the liquid side and gas side to the lower area of the purifying column (14), and having a liquid line (22) which can be shut off (23), via which a flow connection can be established between the evaporation space of the condenser-evaporator (11) and the upper area of the first distillation column (7).
EP97921813A 1996-04-30 1997-04-28 Process for starting an installation for low temperature air separation and installation for low temperature air separation Expired - Lifetime EP0904518B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE19617377A DE19617377A1 (en) 1996-04-30 1996-04-30 Process for restarting a plant for the low-temperature separation of air and plant for the low-temperature separation of air
DE19617377 1996-04-30
PCT/EP1997/002188 WO1997041400A1 (en) 1996-04-30 1997-04-28 Process for starting an installation for low temperature air decomposition and installation for low temperature air decomposition

Publications (2)

Publication Number Publication Date
EP0904518A1 EP0904518A1 (en) 1999-03-31
EP0904518B1 true EP0904518B1 (en) 2001-12-19

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EP97921813A Expired - Lifetime EP0904518B1 (en) 1996-04-30 1997-04-28 Process for starting an installation for low temperature air separation and installation for low temperature air separation

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EP (1) EP0904518B1 (en)
DE (2) DE19617377A1 (en)
ES (1) ES2170951T3 (en)
PT (1) PT904518E (en)
WO (1) WO1997041400A1 (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2774752B1 (en) * 1998-02-06 2000-06-16 Air Liquide AIR DISTILLATION SYSTEM AND CORRESPONDING COLD BOX

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1463075A (en) * 1973-04-13 1977-02-02 Cryoplants Ltd Air separation
DE3732363A1 (en) * 1987-09-25 1989-04-06 Linde Ag Method and device for restarting a gas fractionation plant
FR2660741A1 (en) * 1990-04-10 1991-10-11 Air Liquide PROCESS AND PLANT FOR GENERATING GASEOUS NITROGEN AND CORRESPONDING NITROGEN SUPPLY SYSTEM THEREFOR.

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EP0904518A1 (en) 1999-03-31
PT904518E (en) 2002-05-31
ES2170951T3 (en) 2002-08-16
WO1997041400A1 (en) 1997-11-06
DE59705898D1 (en) 2002-01-31
DE19617377A1 (en) 1997-11-06

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