EP0904518A1 - Process for starting an installation for low temperature air decomposition and installation for low temperature air decomposition - Google Patents

Process for starting an installation for low temperature air decomposition and installation for low temperature air decomposition

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Publication number
EP0904518A1
EP0904518A1 EP97921813A EP97921813A EP0904518A1 EP 0904518 A1 EP0904518 A1 EP 0904518A1 EP 97921813 A EP97921813 A EP 97921813A EP 97921813 A EP97921813 A EP 97921813A EP 0904518 A1 EP0904518 A1 EP 0904518A1
Authority
EP
European Patent Office
Prior art keywords
distillation column
liquid
column
line
source
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP97921813A
Other languages
German (de)
French (fr)
Other versions
EP0904518B1 (en
Inventor
Georg Demski
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Linde GmbH
Original Assignee
Linde GmbH
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Filing date
Publication date
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Application filed by Linde GmbH filed Critical Linde GmbH
Publication of EP0904518A1 publication Critical patent/EP0904518A1/en
Application granted granted Critical
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Classifications

    • 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 beginning at a time to
  • the process was developed as part of the production of nitrogen from air, but the invention can also be used for any other process for the separation of a gas mixture by distillation at a temperature below the ambient temperature.It mainly relates to the restart of a system after an interruption in operation, in particular for the If the column is still at a low temperature, it can also be used when starting up a warm system
  • the invention is based on the object of specifying a particularly economically working method and a corresponding device which enable particularly economical starting, 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 to and a later time ti> to
  • the air feed is opened, preferably gently, that is, the amount of air fed in is regulated and slowly increased from zero to the normal value. It preferably rises in a strictly monotonous manner until it has reached this normal value
  • the time ti 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 ti - 1 0 (for example 3 to 10 minutes) is determined when the column is started up and used for later cases when the system is started up
  • the mass transfer elements in the column (bottom, full body and / or ordered packings) are therefore at least partially wetted and, if necessary, liquid distributors are filled in. If the air is later introduced into the distillation column, rectification can take place in the entire column or in Most of them are used immediately, and the more volatile fraction, which is obtained in the upper part of the column, immediately shows the desired product purity
  • the pressure in the distillation column is, for example, 3 to 15 bar, preferably 6 to 9 bar
  • the distillation column is designed for a nominal product quantity of the more volatile fraction. In the process, between time t 0 and a later one Time ti> t 0 cryogenic liquid is introduced into the distillation column in an amount which is less than the nominal product amount of the more volatile fraction
  • liquid quantity initially fed in is, for example, less than the nominal product quantity. It can also be greater than or equal to the nominal product quantity. if the wetting of the mass transfer elements is accelerated as a result, the amount of liquid added preferably remains constant in the time interval from to to ti and is subsequently reduced, for example to zero
  • the column is therefore driven in particular after the start of the air supply (time ti) with total or almost total return, that is to say 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 taken off as a more volatile fraction.
  • time ti start of the air supply
  • time ti total or almost total return
  • the invention relates equally to processes with a single distillation column and to those with further columns.
  • the more volatile fraction from the upper region of the distillation column still contains Very low boiling point contaminants, in the case of nitrogen this can be helium. Be neon and / or hydrogen.
  • the more volatile fraction is introduced into a pure column in stationary operation, a high-purity product being removed from the pure column.
  • the removal point of the high-purity product is preferably below the introduction of the more volatile fraction.
  • the start-up method according to the invention in particular prevents the pure column from being contaminated by less volatile components (in the case of nitrogen production: oxygen).
  • the upper area of the distillation column and the lower area of the pure column are preferably in a heat-exchanging connection via a condenser-evaporator.
  • 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 filled from outside the system.
  • This reservoir can be designed, for example, as a liquid tank, from which liquid is also withdrawn when there is a need exceeding the nominal product quantity or in the event of an interruption in operation of the system and is evaporated in an external evaporator, for example against ambient air.
  • the source of cryogenic liquid can be formed by a reservoir which is filled by a fluid obtained within the system. The amount of liquid consumed during start-up is then generated again in stationary operation and introduced into the reservoir.
  • the reservoir is filled with a liquid from the clean column.
  • the bottom liquid of the pure column is particularly suitable for this.
  • the bottom of the pure column can itself act as a reservoir for the cryogenic liquid.
  • the reservoir is preferably formed by the evaporation space of the condenser damper.
  • the condenser-evaporator can be arranged in the sump of the clean column (siene DE 4432137 A1) or outside the clean column. In the first case the evaporation space is identical to the bottom of the column, in the second case it is formed by a separate container In systems of this type, it is advantageous if, during the stationary operation of the system to compensate for cold losses, a liquid fraction is introduced into the distillation column from an external source, as is known per se from DE 2417766 A.
  • this liquid fraction and the cryogenic liquid used when starting up can be identical, i.e. they come from the same reservoir however, different reservoirs are provided for the cryogenic liquid which is used for starting up and for the liquid fraction which compensates for the cold losses during stationary operation.
  • a third can be too r Emergency supply or for additional production by external evaporation can be used. External evaporation can take place, for example, through indirect heat exchange with atmospheric air or water or with any other known method
  • the quantity of the liquid fraction introduced to compensate for cold losses is preferably regulated as a function of the liquid level in the bottom of the distillation column. In principle, regulation depending on other liquid levels in the system is also possible
  • the method has at least a first and a second source of cryogenic liquid, at least temporarily cryogenic liquid from both sources being introduced into the distillation column at the same time and the liquid from the second source having at least one theoretical base below the liquid from the
  • the first source is preferably fed in.
  • the feed of both liquids begins approximately simultaneously, namely at time to.
  • the wetting of the mass transfer elements can be carried out more quickly; the air supply (time ti) can start earlier, the start-up process is further shortened.
  • This effect can be further increased 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 at the top and two thirds of the column height (from below), at the top of the column and half of the column height or - in the case of three sources - at the top, two thirds and one third of the column height
  • Infeed quantities are based on the number of theoretical plates between the infeed point and the infeed point underneath or the column sump, 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 added at different points have the same composition; However, the liquids from the two sources preferably have a different composition, which is particularly close to the equilibrium concentration of the liquid flowing down in the distillation column in stationary operation at the respective feed point. In this way, before the air is fed in, a certain adjustment to the concentration curve during the stationary operation of the distillation column. 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, compressed in the air compressor 2 to a pressure of more than 3 bar, preferably 6 5 to 9 5 bar and freed from water, carbon dioxide and possibly carbon monoxide and / or hydrogen in one or more cleaning stages 3, 4, cooled by indirect heat exchange 5 and fed via line 6 into a distillation column 7 operated as a pressure column.
  • the top gas 8 from the distillation column 7 is at least partially liquefied in part (9) in the condenser-evaporator 11, the condensate 12 being fed as return to the distillation column 7 and uncondensed portions mainly helium and neon, with a flushing stream via line 13 subtracted from.
  • the gas in line 13 can, for example, be discarded or mixed with a residual gas fraction.
  • the sump of the helium-neon discharge column 14 is heated by the condenser-evaporator 11, which also serves to form a return for the pressure column 7.
  • the top condenser 16 of the helium-neon discharge column is operated with a relaxed bottom liquid 17 from the pressure column 7 the condensing top fraction of the helium-neon discharge column evaporated fraction is withdrawn via line 19.
  • the residual gas 19 can, optionally together with one or more coil currents, be warmed against air to be separated and then used, for example, as regeneration gas in one or more cleaning stages 3, 4
  • a liquid fraction 24 (for example liquid nitrogen of normal purity) is fed into the column 7 in the stationary operation fed in to cover the cooling requirements caused by insulation and exchange losses.
  • 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, the contents of which evaporate externally to cover additional product requirements or to provide emergency supply in the event of a business interruption
  • the feed 24 preferably takes place at an intermediate point, that is to say at least one theoretical floor below the top of the column.
  • the amount of the liquid introduced here is set, for example, via a liquid level controller in the bottom of the distillation column 7 or, depending on the liquid level, in one of the condensers 11 or 16
  • the product line 20 can alternatively or additionally be fed externally vaporized product from the emergency supply tank, not shown, in order to use liquid from the emergency supply tank to start the system, a line can be provided from the emergency supply tank to the upper area of the distillation column 7 System and / or be filled from an external source In the latter case, the emergency supply system is independent of the operation of the columns
  • the two columns 7 and 14 can be arranged inside a vacuum insulation which also encloses a liquid tank, preferably the one in which the liquid fraction which is fed in at 24 is stored. Details of this arrangement can be found in EP 538857 A1
  • the bottom liquid of the clean column 14 supplemented by the return liquid flowing down from the mass transfer elements of this column, remains in the bottom of the clean column 14, i.e. in the evaporation chamber of the condenser-evaporator 11, and this liquid can be used in the manner according to the invention for restarting the system
  • valve 23 When restarting after the interruption of operation, the valve 23 is partially or fully opened at the start time to, while the air feed line 6 remains closed.
  • the liquid from the sump of the clean column 14 flows via line 22 into the head of the distillation column 7. or ordered packing) and, if necessary, 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, whereby additional return liquid arises.
  • 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 k Over 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 clean column 14 plus the hydrostatic pressure of the liquid. Otherwise, top gas from the distillation column 7 was printed into the clean column 14 via line 22 and this contaminate with oxygen This can be done 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

Landscapes

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

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

Beschreibung description
Verfahren zum Anfahren einer Anlage zur Tieftemperaturzerlequnq von Luft und Anlage zur Tieftemperaturzerlequnα von LuftMethod for starting up a plant for low-temperature decomposition of air and plant for low-temperature decomposition of air
Die Erfindung betrifft ein Verfahren zum Anfahren einer Anlage zur Tieftemperaturzerlegung eines Gasgemischs, insbesondere von Luft, die mindestens eine Destilliersäule, in der eine leichterfluchtige 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 Flussigkeitseinfuhrung zu einem Zeitpunkt to beginntThe 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 beginning at a time to
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 anwendbarThe process was developed as part of the production of nitrogen from air, but the invention can also be used for any other process for the separation of a gas mixture by distillation at a temperature below the ambient temperature.It mainly relates to the restart of a system after an interruption in operation, in particular for the If the column is still at a low temperature, it can also be used when starting up a warm system
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 befullten Flussigtank in die Destilliersäule eingespeist, gleichzeitig wird Luft in die Säule eingeblasen Dadurch steht sofort gasformiges Produkt am Kopf der Säule zur VerfugungA method of the type mentioned at the outset is known from EP 452177 A1. When the system is restarted, a large amount of cryogenic liquid, namely nitrogen, is fed into the distillation column from an externally filled liquid tank, at the same time air is blown into the column, which immediately results in gaseous product at the head of the column
Das leichterfluchtige Kopfprodukt weist jedoch zunächst eine relativ niedrige Reinheit auf, da anfangs fast keine Rektifikation in der Säule stattfindetHowever, the more volatile top product initially has a relatively low purity, since almost no rectification initially takes place in the column
Der Erfindung liegt die Aufgabe zugrunde, ein besonders wirtschaftlich arbeitendes Verfahren und eine entsprechende Vorrichtung anzugeben, die ein besonders gunstiges Anfahren ermöglichen, insbesondere eine hohe Reinheit im leichterfluchtigen Produkt beim Wiederanfahren nach Betriebsunterbrechungen Diese Aufgabe wird dadurch gelost, daß zwischen dem Zeitpunkt to und einem spateren Zeitpunkt ti > to keine oder im wesentlichen keine Luft in die Destilliersäule eingeleitet wirdThe invention is based on the object of specifying a particularly economically working method and a corresponding device which enable particularly economical starting, 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 to and a later time ti> to
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 betragt, die die Destilliersäule im stationären Betrieb verarbeitet Im allgemeinen ist es am gunstigsten, wenn die Luftzuspeisung in die Säule zwischen den genannten Zeitpunkten vollständig versperrt istThe feature that "essentially no air" is fed into the column here means an amount of feed air which is at most 20 mol%, preferably at most 10 mol%, most preferably at most 1 mol% of the amount of air which the distillation column in stationary operation Processed In general, it is most favorable if the air supply to the column is completely blocked between the times mentioned
Im Zeitpunkt ti 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 hatAt time ti, the air feed is opened, preferably gently, that is, the amount of air fed in is regulated and slowly increased from zero to the normal value. It preferably rises in a strictly monotonous manner until it has reached this normal value
Der Zeitpunkt ti kann entweder fest vorgegeben oder dadurch bestimmt werden, daß die in der Säule herabfallende Flüssigkeit einen bestimmten unteren Saulenabschnitt erreicht hat, beispielsweise den Sumpf, oder daß der Flussigkeitsstand im Sumpf der Säule eine gewisse Mindesthohe erreicht hat In der Praxis reicht es aus, wenn bei der Inbetriebnahme der Säule ein sinnvolles Zeitintervall ti - 10 (beispielsweise 3 bis 10 Minuten) ermittelt und dieses für spatere Falle des Anfahrens der Anlage verwendetThe time ti 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 ti - 1 0 (for example 3 to 10 minutes) is determined when the column is started up and used for later cases when the system is started up
Bei dem erfindungsgemaßen Verfahren werden also zunächst die Stoffaustauschelemente in der Säule (Boden, Fullkorper und/oder geordnete Packungen) mindestens teilweise benetzt und gegebenenfalls Flussigkeitsverteiler aufgefüllt Wenn die Luft zum spateren Zeitpunkt in die Destilliersäule eingelassen wird, kann die Rektifikation in der gesamten Säule oder in ihrem größten Teil sofort einsetzen, und die leichterfluchtige Fraktion, die im oberen Teil der Säule gewonnen wird, weist unmittelbar die gewünschte Produktreinheit aufIn the process according to the invention, the mass transfer elements in the column (bottom, full body and / or ordered packings) are therefore at least partially wetted and, if necessary, liquid distributors are filled in. If the air is later introduced into the distillation column, rectification can take place in the entire column or in Most of them are used immediately, and the more volatile fraction, which is obtained in the upper part of the column, immediately shows the desired product purity
Der Druck in der Destilliersäule betragt beispielsweise 3 bis 15 bar, vorzugsweise 6 bis 9 barThe pressure in the distillation column is, for example, 3 to 15 bar, preferably 6 to 9 bar
Die Destilliersäule ist für eine Nennproduktmenge der leichterfluchtigen Fraktion ausgelegt Bei dem Verfahren kann zwischen dem Zeitpunkt t0 und einem spateren Zeitpunkt ti > t0 tiefkalte Flüssigkeit in einer Menge in die Destilliersäule eingeführt werden die geringer als die Nennproduktmenge der leichterfluchtigen Fraktion istThe distillation column is designed for a nominal product quantity of the more volatile fraction. In the process, between time t 0 and a later one Time ti> t 0 cryogenic liquid is introduced into the distillation column in an amount which is less than the nominal product amount of the more volatile fraction
Vor der Einfuhrung von Luft (Zeitpunkt ti) verdampft kaum Flüssigkeit in der Säule, sondern es werden lediglich die Stoffaustauschelemente in der Säule benetzt und gegebenenfalls Flussigkeitsverteiler aufgefüllt Die anfangs eingespeiste Flussigkeitsmenge betragt beispielsweise weniger als die Nennproduktmenge Sie kann auch großer oder gleich der Nennproduktmenge sein, falls dadurch die Benetzung der Stoffaustauschelemente beschleunigt wird Die zugespeiste Flussigkeitsmenge bleibt im Zeitintervall von to bis ti vorzugsweise konstant und wird anschließend reduziert, beispielsweise auf NullBefore the introduction of air (point in time ti), 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 in. The liquid quantity initially fed in is, for example, less than the nominal product quantity. It can also be greater than or equal to the nominal product quantity. if the wetting of the mass transfer elements is accelerated as a result, the amount of liquid added preferably remains constant in the time interval from to to ti and is subsequently reduced, for example to zero
Es ist besonders gunstig, wenn zwischen dem Zeitpunkt to und einem noch spateren Zeitpunkt t2 > ti keine oder im wesentlichen keine leichterfluchtige Fraktion aus der Destilliersäule entnommen wirdIt is particularly advantageous if no or essentially no more volatile fraction is removed from the distillation column between the time to and an even later time t 2 > ti
Die Säule wird also insbesondere auch nach dem Beginn der Luftzufuhr (Zeitpunkt ti) mit totalem oder fast totalem Rucklauf 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 leichterfluchtige Fraktion entnommen Im Regelfall bleibt die entsprechende Produktleitung bis zum Zeitpunkt t2 (beispielsweise 4 bis 15 Minuten nach dem Startzeitpunkt to) vollständig geschlossenThe column is therefore driven in particular after the start of the air supply (time ti) with total or almost total return, that is to say 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 taken off as a more 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 to)
Dadurch kann gewährleistet werden, daß bei der Öffnung derThis can ensure that when opening the
Produktentnahmeleitung der Destilliersäule unmittelbar leichterfluchtige 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 spateren Zeitpunkt t3 > t2 erreicht die zugefuhrte Luftmenge ihren Normalwert, die Entnahme der ieichterfluchtigen Fraktion wird bis zu einem Zeitpunkt U > t3 auf die Nennproduktmenge erhöht Die Zeitpunkte t3 und U liegen beispielsweise 12 bis 25 Minuten nach dem Startzeitpunkt toProduct extraction line of the distillation column directly lighter volatile fraction in the desired purity is present, so in that purity is achieved even in the steady operation of the plant, the time t 2, for example, only about 3 to 20 minutes after the start time t 0 are at a later time t 3 > t 2 the amount of air supplied reaches its normal value, the removal of the less volatile fraction is increased to the nominal product amount up to a time U> t 3. The times t 3 and U are, for example, 12 to 25 minutes after the start time to
Die Erfindung bezieht sich gleichermaßen auf Verfahren mit einer einzelnen Destilliersäule und auf solche mit weiteren Kolonnen Häufig enthalt die leichterfluchtige 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 leichterfluchtige Fraktion im stationären Betrieb in eine Reinsaule 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 Reinsaule durch schwererflüchtige Komponenten (im Falle der Stickstoffgewinnung: Sauerstoff) verunreinigt wird.The invention relates equally to processes with a single distillation column and to those with further columns. Often, the more volatile fraction from the upper region of the distillation column still contains Very low boiling point contaminants, in the case of nitrogen this can be helium. Be neon and / or hydrogen. For this reason, in the case of particularly high purity requirements, it is advantageous if the more volatile fraction is introduced into a pure column in stationary operation, a high-purity product being removed from the pure column. The removal point of the high-purity product is preferably below the introduction of the more volatile fraction. In such a process, the start-up method according to the invention in particular prevents the pure column from being contaminated by less volatile components (in the case of nitrogen production: oxygen).
Vorzugsweise stehen der obere Bereich der Destilliersäule und der untere Bereich der Reinsaule über einen Kondensator-Verdampfer in warmetauschender Verbindung Eine derartige Doppelsäule ist aus der DE 4432137 A1 an sich bekannt.The upper area of the distillation column and the lower area of the pure column are preferably in a heat-exchanging connection via a condenser-evaporator. 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 filled from outside the system. This reservoir can be designed, for example, as a liquid tank, from which liquid is also withdrawn when there is a need exceeding the nominal product quantity or in the event of an interruption in operation of the system and is evaporated in an external evaporator, for example against ambient air.
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 wahrend des Anfahrens verbrauchte Flüssigkeitsmenge wird dann im stationären Betrieb wieder erzeugt und in das Reservoir eingeführt.As an alternative or in addition, the source of cryogenic liquid can be formed by a reservoir which is filled by a fluid obtained within the system. The amount of liquid consumed during start-up is then generated again in stationary operation and introduced into the reservoir.
Falls die Anlage eine Reinsäule aufweist, ist es besonders gunstig, wenn das Reservoir durch eine Flüssigkeit aus der Reinsaule befüllt wird. Dazu ist insbesondere die Sumpfflüssigkeit der Reinsäule geeignet. Der Sumpf der Reinsaule kann selbst als Reservoir für die tiefkalte Flüssigkeit fungieren.If the system has a clean column, it is particularly advantageous if the reservoir is filled with a liquid from the clean column. The bottom liquid of the pure column is particularly suitable for this. The bottom of the pure column can itself act as a reservoir for the cryogenic liquid.
Das Reservoir wird vorzugsweise durch den Verdampfungsraum des Kondensator- Verdamofers gebildet. Der Kondensator-Verdampfer kann dabei im Sumpf der Reinsaule (siene DE 4432137 A1) oder außerhalb der Reinsaule angeordnet sein. Im ersten Fall ist der Verdampfungsraum mit dem Sumpf der Säule identisch, im zweiten Fall wird er durch einen eigenen Behälter gebildet Bei derartigen Anlagen ist es gunstig, wenn wahrend des stationären Betriebs der Anlage zum Ausgleich von Kalteverlusten eine flussige 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 Flussigkeitszuspeisung gedeckt, wobei keiner der Prozeßstrome arbeitsleistend entspannt wird und die Anlage keine kalteerzeugende Entspannungsmaschine (beispielsweise Turbine) aufweist Grundsätzlich können diese flussige 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 flussige Fraktion, die beim stationären Betrieb die Kalteverluste ausgleicht vorgesehen Eines dieser beiden Reservoirs oder vorzugsweise ein drittes kann zur Notversorgung oder zu zusätzlicher Produktion durcn externe Verdampfung genutzt werden Die externe Verdampfung kann beispielsweise durch indirekten Wärmeaustausch mit atmosphärischer Luft oder Wasser oder mit jeder anderen bekannten Methode erfolgenThe reservoir is preferably formed by the evaporation space of the condenser damper. The condenser-evaporator can be arranged in the sump of the clean column (siene DE 4432137 A1) or outside the clean column. In the first case the evaporation space is identical to the bottom of the column, in the second case it is formed by a separate container In systems of this type, it is advantageous if, during the stationary operation of the system to compensate for cold losses, a liquid fraction is introduced into the distillation column from an external source, as is known per se from DE 2417766 A. All or essentially all of it is preferred The cooling requirements of the process are covered by liquid supply, whereby none of the process streams is expanded to perform work and the system does not have a cold-generating expansion machine (e.g. turbine). Basically, this liquid fraction and the cryogenic liquid used when starting up can be identical, i.e. they come from the same reservoir however, different reservoirs are provided for the cryogenic liquid which is used for starting up and for the liquid fraction which compensates for the cold losses during stationary operation. One of these two reservoirs or preferably a third can be too r Emergency supply or for additional production by external evaporation can be used. External evaporation can take place, for example, through indirect heat exchange with atmospheric air or water or with any other known method
Die Regelung der Menge der zum Ausgleich von Kalteverlusten eingeführten flussigen Fraktion erfolgt vorzugsweise in Abhängigkeit vom Flussigkeitsstand im Sumpf der Destilliersäule. Grundsätzlich ist auch die Regelung in Abhängigkeit von anderen Flussigkeitsstanden in der Anlage möglichThe quantity of the liquid fraction introduced to compensate for cold losses is preferably regulated as a function of the liquid level in the bottom of the distillation column. In principle, regulation depending on other liquid levels in the system is also 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, namlich zum Zeitpunkt to. Durch die gleichzeitige Einspeisung von Flüssigkeit an mehreren Stellen kann die Benetzuπg der Stoffaustauschelemente schneller durchgeführt werden; die Luftzufuhr (Zeitpunkt ti) 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 Flussigkeitsverteiler Die unterschiedlichen Einspeisungen können beispielsweise am Kopf und bei zwei Dritteln der Kolonnenhohe (von unten), am Kopf der Säule und bei der Hälfte der Koloπnenhohe oder - im Fall von drei Quellen - am Kopf, bei zwei Dritteln und bei einem Drittel der Kolonπenhohe vorgenommen werden Die Einspeisemengen richten sich jeweils nach der Anzahl der zwischen der Einspeisestelle und der darunterliegenden Einspeisestelle beziehungsweise dem Kolonnensumpf liegenden theoretischen Boden, Hauptkriterium ist die möglichst rasch zu erreichende ausreichende Benetzung der StoffaustauschelementeIt is also advantageous if the method has at least a first and a second source of cryogenic liquid, at least temporarily cryogenic liquid from both sources being introduced into the distillation column at the same time and the liquid from the second source having at least one theoretical base below the liquid from the The first source is preferably fed in. The feed of both liquids begins approximately simultaneously, namely at time to. By simultaneously feeding in liquid at several points, the wetting of the mass transfer elements can be carried out more quickly; the air supply (time ti) can start earlier, the start-up process is further shortened.This effect can be further increased 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 at the top and two thirds of the column height (from below), at the top of the column and half of the column height or - in the case of three sources - at the top, two thirds and one third of the column height Infeed quantities are based on the number of theoretical plates between the infeed point and the infeed point underneath or the column sump, 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 Gleichgewichtskonzeπtration 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 wahrend des stationären Betriebs der Destilliersäule vorgenommen werden. Der Anfahrvorgang verkürzt sich weiterIt is true that wetting of the mass transfer elements can also be achieved if the two liquids added at different points have the same composition; However, the liquids from the two sources preferably have a different composition, which is particularly close to the equilibrium concentration of the liquid flowing down in the distillation column in stationary operation at the respective feed point. In this way, before the air is fed in, a certain adjustment to the concentration curve during the stationary operation of the distillation column. The starting process is further shortened
Die Erfindung betrifft außerdem eine Anlage zur Tieftemperaturzerlegung von Luft gemäß den Patentansprüchen 15 bis 17The invention also relates to a plant for the low-temperature separation of air according to claims 15 to 17
Die Erftndung sowie weitere Einzelheiten der Erfindung werden im folgenden anhand eines in der Zeichnung schematisch dargestellten Ausführungsbeispiels naher erläutertThe invention and further details of the invention are explained in more detail below with reference to an exemplary embodiment shown schematically in the drawing
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 Umstanden 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 hauptsachlich 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 Reinsaule 14 geleitet, indem Leitung 13 ein Ventil enthalt und nach diesem Ventil in Leitung 10 stromabwärts des dortigen Drosselventils mundet (in der Zeichnung nicht dargestellt) Der nicht in den Kondensator-Verdampfer 11 eingeleitete Teil des Kopfgases der Destilliersäule wird als leichterfluchtige Fraktion 10 entnommen und über ein Drosselventil in eine Reinsaule (Helium-Neon-Ausschleussaule) 14 eingespeist Die Einspeisestelle befindet sich auf mittlerer Hohe der Reinsaule 14, in deren unterem Bereich hochreiner Stickstoff anfallt Dieses Hochreinprodukt wird vorzugsweise in Dampfform direkt oberhalb des Sumpfes der Reinsaule entnommen (Leitung 15) Der reine Produktstickstoff wird in 5 gegen zu zerlegende Luft auf etwa Umgebungstemperatur angewärmt und über die Produktleitung 20 abgezogenAtmospheric air is drawn in at 1, compressed in the air compressor 2 to a pressure of more than 3 bar, preferably 6 5 to 9 5 bar and freed from water, carbon dioxide and possibly carbon monoxide and / or hydrogen in one or more cleaning stages 3, 4, cooled by indirect heat exchange 5 and fed via line 6 into a distillation column 7 operated as a pressure column. The top gas 8 from the distillation column 7 is at least partially liquefied in part (9) in the condenser-evaporator 11, the condensate 12 being fed as return to the distillation column 7 and uncondensed portions mainly helium and neon, with a flushing stream via line 13 subtracted from. The gas in line 13 can, for example, be discarded or mixed with a residual gas fraction. It is preferably fed continuously into the clean column 14 described below, in which line 13 contains a valve and flows downstream of the throttle valve there in line 10 (not shown in the drawing) ) The part of the top gas from the distillation column which is not introduced into the condenser-evaporator 11 is removed as a more volatile fraction 10 and is fed via a throttle valve into a clean column (helium-neon discharge column) 14 Area of high-purity nitrogen is obtained. This high-purity product is preferably taken in vapor form directly above the bottom of the pure column (line 15). The pure product nitrogen is warmed in 5 against air to be separated to about ambient temperature and drawn off via the product line 20
Der Sumpf der Helium-Neon-Ausschleussaule 14 wird durch den Kondensator- Verdampfer 11 beheizt, der auch zur Bildung von Rucklauf für die Drucksaule 7 dient Der Kopfkondensator 16 der Helium-Neon-Ausschleussaule wird mit entspannter Sumpfflussigkeit 17 aus der Drucksaule 7 betrieben Die gegen die kondensierende Kopffraktion der Helium-Neon-Ausschleussaule verdampfte Fraktion wird über Leitung 19 abgezogen Das Restgas 19 kann, gegebenenfalls gemeinsam mit einem oder mehreren Spulstromen, 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 Umstanden auch Wasserstoff, verlassen die Anlage mit dem Spulstrom 18The sump of the helium-neon discharge column 14 is heated by the condenser-evaporator 11, which also serves to form a return for the pressure column 7. The top condenser 16 of the helium-neon discharge column is operated with a relaxed bottom liquid 17 from the pressure column 7 the condensing top fraction of the helium-neon discharge column evaporated fraction is withdrawn via line 19. The residual gas 19 can, optionally together with one or more coil currents, be warmed against air to be separated and then used, for example, as regeneration gas in one or more cleaning stages 3, 4 Top condenser 16 non-liquefied components, in particular helium and neon, and possibly also hydrogen, leave the system with the coil current 18
Das Ventil 23 in einer Leitung 22, die den Sumpf der Reinsaule 14 mit dem Kopf der Destilliersäule 7 verbindet, ist im stationären Betrieb der Anlage geschlossen Über Leitung 24 wird im stationären Betrieb eine flussige Fraktion 24 (beispielsweise Flussigstickstoff 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 Flussigtank gespeichert Dieser Flussigtank 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 Flussigkeitsstandregler im Sumpf der Destilliersäule 7 oder in Abhängigkeit vom Flüssigkeitsstand in einem der Kondensatoren 11 oder 16 eingestellt Der Produktleitung 20 kann über Leitung 21 alternativ oder zusatzlich 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 befullt werden Im letzten Fall ist das Notversorgungssystem unabhängig vom Betrieb der SäulenThe valve 23 in a line 22, which connects the bottom of the pure column 14 to the head of the distillation column 7, is closed in the stationary operation of the system. Via line 24, a liquid fraction 24 (for example liquid nitrogen of normal purity) is fed into the column 7 in the stationary operation fed in to cover the cooling requirements caused by insulation and exchange losses.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, the contents of which evaporate externally to cover additional product requirements or to provide emergency supply in the event of a business interruption The feed 24 preferably takes place at an intermediate point, that is to say at least one theoretical floor below the top of the column. The amount of the liquid introduced here is set, for example, via a liquid level controller in the bottom of the distillation column 7 or, depending on the liquid level, in one of the condensers 11 or 16 The product line 20 can alternatively or additionally be fed externally vaporized product from the emergency supply tank, not shown, in order to use liquid from the emergency supply tank to start the system, a line can be provided from the emergency supply tank to the upper area of the distillation column 7 System and / or be filled from an external source In the latter case, the emergency supply system is independent of the operation of the columns
Die beiden Kolonnen 7 und 14 können im Inneren einer Vakuumisolierung angeordnet sein, die auch einen Flussigtank umschließt, vorzugsweise denjenigen in dem die flussige Fraktion gespeichert ist, die bei 24 eingespeist wird Einzelheiten zu dieser Anordnung sind der EP 538857 A1 zu entnehmenThe two columns 7 and 14 can be arranged inside a vacuum insulation which also encloses a liquid tank, preferably the one in which the liquid fraction which is fed in at 24 is stored. Details of this arrangement can be found in EP 538857 A1
Bei einer Betriebsunterbrechung bleibt die Sumpfflussigkeit der Reinsaule 14 ergänzt durch die von den Stoffaustauschelementen dieser Säule herabfließende Rucklaufflussigkeit, im Sumpf der Reinsaule 14, also im Verdampfungsraum des Kondensator-Verdampfers 11 , stehen, diese Flüssigkeit kann auf die erfindungsgemaße Weise zum Wiederanfahren der Anlage genutzt werdenIn the event of an interruption in operation, the bottom liquid of the clean column 14, supplemented by the return liquid flowing down from the mass transfer elements of this column, remains in the bottom of the clean column 14, i.e. in the evaporation chamber of the condenser-evaporator 11, and this liquid can be used in the manner according to the invention for restarting the system
Beim Wiederanfahren nach der Betriebsunterbrechung wird zum Startzeitpunkt to das Ventil 23 teilweise oder vollständig geöffnet, wahrend die Luftzuspeisungsleitung 6 noch geschlossen bliebt Die Flüssigkeit aus dem Sumpf der Reinsaule 14 fließt über Leitung 22 in den Kopf der Destilliersäule 7 Die Stoffaustauschelemente (Boden, Fullkorper und/oder geordnete Packung) und gegebenenfalls die Flussigkeitsverteiler in der Säule 7 werden nach und nach benetzt beziehungsweise gefüllt Ab dem spateren Zeitpunkt ti 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 Rucklaufflussigkeit entsteht Etwa ab ti wird das Ventil 23 langsam geschlossen, so daß sich die über 22 stromende Flussigkeitsmenge langsam verringert, bis sie zu einer Zeit k auf Null gesunken ist Die Flussigkeitszufuhr über 22 darf höchstens solange geöffnet bleiben, wie der Druck am Kopf der Destilliersäule 7 geringer ist als der Druck im Sumpf der Reinsaule 14 plus dem hydrostatischen Druck der Flüssigkeit Ansonsten wurde über Leitung 22 Kopfgas aus der Destilliersäule 7 in die Reinsaule 14 gedruckt 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 werdenWhen restarting after the interruption of operation, the valve 23 is partially or fully opened at the start time to, while the air feed line 6 remains closed. The liquid from the sump of the clean column 14 flows via line 22 into the head of the distillation column 7. or ordered packing) and, if necessary, the liquid distributors in the column 7 are gradually wetted or filled. From the later time ti, 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, whereby additional return liquid arises. From approximately ti, 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 k Over 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 clean column 14 plus the hydrostatic pressure of the liquid. Otherwise, top gas from the distillation column 7 was printed into the clean column 14 via line 22 and this contaminate with oxygen This can be done 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 t2wιrd über Leitung 10 leichterfluchtiges Produkt in bis zur Nennproduktmenge ansteigendem Umfang entnommen und der Reinsaule 14 zugeleitet Parallel dazu wird die Leitung 15 für Hochreinprodukt geöffnetFrom 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 ti und einem spateren Zeitpunkt t3wιrd die Luftmenge kontinuierlich auf ihren Normalwert gesteigert Gleichzeitig oder etwas spater (t4) die durch die Leitung 10 fließende leichterfluchtige Fraktion auf die Nennproduktmenge und die Hochreinproduktmenge in Leitung 15 auf den entsprechenden Wert angestiegen Damit ist der stationäre Betriebsfall der Anlage erreichtBetween ti and a later point in time t 3, the air quantity is continuously increased to its normal value. At the same time or somewhat later (t4), the more volatile fraction flowing through line 10 increases to the nominal product quantity and the high-purity product quantity in line 15 to the corresponding value of the plant
Der gesamte Ablauf des Wiederanfahrens erfolgt vorzugsweise automatisch The entire process of restarting is preferably carried out automatically

Claims

Patentansprüche claims
1. Verfahren zum Anfahren einer Anlage zur Tieftemperaturzerlegung eines Gasgemischs, insbesondere von Luft, die mindestens eine Destilliersäule (7), in der eine leichterflüchtige Fraktion (10), insbesondere Stickstoff, erzeugt wird, und mindestens eine Quelle für tiefkalte Flüssigkeit aufweist, wobei bei dem Verfahren mindestens zeitweise tiefkalte Flüssigkeit (22) aus dieser Quelle in einen oberen Bereich der Destilliersäule (7) eingeführt wird, wobei diese Flussigkeitseinfuhrung zu einem Zeitpunkt to beginnt, dadurch gekennzeichnet, daß zwischen dem Zeitpunkt to und einem späteren Zeitpunkt ti > to kein oder im wesentlichen kein Gasgemisch (6) in die Destilliersäule (7) eingeleitet wird.1. A method for starting up a plant for the low-temperature decomposition 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 for cryogenic liquid, wherein at the process, at least temporarily, cryogenic liquid (22) is introduced from this source into an upper region of the distillation column (7), this introduction of liquid beginning at a time to, characterized in that between the time to and a later time ti> to no or essentially no gas mixture (6) is introduced into the distillation column (7).
2. Verfahren nach Anspruch 1 , dadurch gekennzeichnet, daß die Destilliersäule (7) für eine Nennproduktmenge der leichterflüchtigen Fraktion (10) ausgelegt ist und daß zwischen dem Zeitpunkt t0 und einem späteren Zeitpunkt ti > to tiefkalte Flüssigkeit (22) in einer Menge in die Destilliersäule eingeführt wird, die geringer als die Nennproduktmenge der leichterflüchtigen Fraktion (10) ist.2. The method according to claim 1, characterized in that the distillation column (7) is designed for a nominal product amount of the more volatile fraction (10) and that between the time t 0 and a later time ti> to cryogenic liquid (22) in a quantity in the distillation column is introduced, which is less than the nominal product amount of the volatile fraction (10).
3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß zwischen dem Zeitpunkt to und einem noch späteren Zeitpunkt t2 > ti keine oder im wesentlichen keine leichterflüchtige Fraktion (10) aus der Destilliersäule (7) entnommen wird.3. The method according to claim 1 or 2, characterized in that between the time to and a later time t 2 > ti no or substantially no volatile fraction (10) is removed from the distillation column (7).
4. Verfahren nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß die leichterflüchtige Fraktion (10) in eine Reinsäule (14) eingeleitet wird, wobei der Reinsäule (14) ein Hochreinprodukt (15) entnommen wird.4. The method according to any one of claims 1 to 3, characterized in that the more volatile fraction (10) is introduced into a pure column (14), the pure column (14) being a high-purity product (15) is removed.
5. Verfahren nach Anspruch 4, dadurch gekennzeichnet, daß der obere Bereich der Destilliersäule (7) und der untere Bereich der Reinsäule (14) über einen Kondensator-Verdampfer (11) in wärmetauschender Verbindung stehen.5. The method according to claim 4, characterized in that the upper region of the distillation column (7) and the lower region of the pure column (14) via a condenser-evaporator (11) are in heat-exchanging connection.
6. Verfahren nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß die Quelle für tiefkalte Flüssigkeit durch ein Reservoir gebildet wird, das von außerhalb der Anlage befüllt wird. Verfahren nach einem der Ansprüche 1 bis 6, dadurch gekennzeichnet, daß die Quelle für tiefkalte Flüssigkeit durch ein Reservoir gebildet wird, das durch ein innerhalb der Anlage gewonnenes Fluid befullt wird6. The method according to any one of claims 1 to 5, characterized in that the source of cryogenic liquid is formed by a reservoir which is filled from outside the system. Method according to one of claims 1 to 6, characterized in that the source of cryogenic liquid is formed by a reservoir which is filled by a fluid obtained within the system
Verfahren nach Anspruch 7 und nach einem der Ansprüche 4 oder 5, dadurch gekennzeichnet, daß das Reservoir durch eine Flüssigkeit aus der Reinsaule (14) befullt wirdMethod according to claim 7 and according to one of claims 4 or 5, characterized in that the reservoir is filled with a liquid from the pure column (14)
Verfahren nach den Ansprüchen 5 und 7, dadurch gekennzeichnet, daß das Reservoir durch den Verdampfungsraum des Kondensator-Verdampfers (11) gebildet wirdMethod according to claims 5 and 7, characterized in that the reservoir is formed by the evaporation space of the condenser-evaporator (11)
Verfahren nach einem der Ansprüche 1 bis 9, dadurch gekennzeichnet, daß wahrend des stationären Betriebs der Anlage zum Ausgleich von Kalteverlusten eine flussige Fraktion (24) aus einer äußeren Quelle in die Destilliersäule (7) eingeleitet wirdMethod according to one of claims 1 to 9, characterized in that a liquid fraction (24) from an external source is introduced into the distillation column (7) during the stationary operation of the system to compensate for cold losses
Verfahren nach Anspruch 10, dadurch gekennzeichnet, daß die Menge der in die Destilliersäule (7) eingespeisten flussigen Fraktion (24) in Abhängigkeit vom Flussigkeitsstand im Sumpf der Destilliersäule (7) eingestellt wirdMethod according to claim 10, characterized in that the amount of the liquid fraction (24) fed into the distillation column (7) is adjusted as a function of the liquid level in the bottom of the distillation column (7)
Verfahren nach einem der Ansprüche 1 bis 11 , gekennzeichnet durch mindestens eine erste und eine zweite Quelle für tiefkalte Flüssigkeit, wobei mindestens zeitweise tiefkalte Flüssigkeit aus beiden Quellen gleichzeitig in die Destilliersäule (7) eingeführt wird, und die Flüssigkeit (24) aus der zweiten Quelle mindestens einen theoretischen Boden unterhalb der Flüssigkeit (22) aus der ersten Quelle eingespeist wirdMethod according to one of claims 1 to 11, characterized by at least a first and a second source of cryogenic liquid, at least temporarily cryogenic liquid from both sources being simultaneously introduced into the distillation column (7), and the liquid (24) from the second source at least one theoretical plate below the liquid (22) is fed from the first source
Verfahren nach Anspruch 12, dadurch gekennzeichnet, daß die Flüssigkeiten aus den beiden Quellen eine unterschiedliche Zusammensetzung aufweisenA method according to claim 12, characterized in that the liquids from the two sources have a different composition
Verfahren nach Anspruch 13, dadurch gekennzeichnet, daß die Zusammensetzungen der beiden Flüssigkeiten nahe bei der Gleichgewichtskonzentration der in der Destilliersäule (7) im stationären Betrieb herabfließenden Flüssigkeit an der jeweiligen Einspeisestelle liegen Anlage zur Tieftemperaturzerlegung eines Gasgemischs, insbesondere von Luft, mit mindestens einer Destilliersäule (7) zur Erzeugung einer leichterfluchttgen Fraktion (10), insbesondere von Stickstoff, mit einer Luftzuspeisungsleitung (1 , 6), die in den unteren Bereich der Destilliersäule (7) fuhrt, mit einer Flussigkeitsleitung (22), die in den oberen Bereich der Destilliersäule (7) fuhrt und mit Steuerungsmitteln, die so ausgebildet sind, daß beim Beginn des Anfahrens der Anlage die Flussigkeitsleitung (22) geöffnet und die Luftzuspeisungsleitung (1 , 6) vollständig oder im wesentlichen vollständig geschlossen istA method 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) during stationary operation at the respective feed point Plant for the low-temperature separation of a gas mixture, in particular air, with at least one distillation column (7) for producing a more easily escaping fraction (10), in particular nitrogen, with an air feed line (1, 6) which leads into the lower region of the distillation column (7) , with a liquid line (22) which leads into the upper region of the distillation column (7) and with control means which are designed in such a way that the liquid line (22) opens and the air feed line (1, 6) completely when the system starts up or is essentially completely closed
Anlage zur Tieftemperaturzerlegung eines Gasgemischs, insbesondere von Luft, mit einer ersten Destilliersäule (7) zur Erzeugung einer leichterfluchtigen Fraktion, insbesondere von Stickstoff, mit einer Gasleitung (10), die vom oberen Bereich der ersten Destilliersäule (7) in eine Reinsaule (14) fuhrt und ein Drosselventil aufweist, und mit einer Reinproduktleitung (15), die mit dem unteren Bereich der Reinsaule (14) verbunden ist, gekennzeichnet durch eine absperrbare (23) Flussigkeitsleitung (22), über die eine Stromungsverbindung zwischen dem unteren Bereich der Reinsaule (14) und dem oberen Bereich der ersten Destilliersäule (7) herstellbar istPlant for the low-temperature separation of a gas mixture, in particular air, with a first distillation column (7) for producing a more volatile fraction, in particular nitrogen, with a gas line (10) which leads from the upper region of the first distillation column (7) into a pure column (14) leads and has a throttle valve, and with a pure product line (15), which is connected to the lower area of the clean column (14), characterized by a lockable (23) liquid line (22), via which a flow connection between the lower area of the clean column ( 14) and the upper region of the first distillation column (7) can be produced
Anlage zur Tieftemperaturzerlegung eines Gasgemischs, insbesondere von Luft, mit einer ersten Destilliersäule (7) zur Erzeugung einer leichterfluchtigen Fraktion, insbesondere von Stickstoff, mit einer Gasleitung (10), die vom oberen Bereich der ersten Destilliersäule (7) in eine Reinsaule fuhrt (14) und ein Drosselventil aufweist, mit einer Reinproduktleitung (15), die mit dem unteren Bereich der Reinsaule (14) verbunden ist, und mit einem Kondensator-Verdampfer (11), dessen Verdampfungsraum flussigkeits- und gasseitig mit dem unteren Bereich der Reinsaule (14) in Stromungsverbindung steht, gekennzeichnet durch eine absperrbare (23) Flussigkeitsleitung (22), über die eine Stromungsverbindung zwischen dem Verdampfungsraum des Kondensator-Verdampfers (11) und dem oberen Bereich der ersten Destilliersäule (7) herstellbar ist Plant for the low-temperature separation of a gas mixture, in particular air, with a first distillation column (7) to produce a more volatile fraction, in particular nitrogen, with a gas line (10) which leads from the upper area of the first distillation column (7) into a pure column (14 ) and has a throttle valve, with a pure product line (15), which is connected to the lower area of the clean column (14), and with a condenser-evaporator (11), the evaporation space on the liquid and gas sides with the lower area of the clean column (14 ) is in flow connection, characterized by a lockable (23) liquid line (22), via which a flow connection between the evaporation chamber of the condenser-evaporator (11) and the upper region of the first distillation column (7) can be established
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)

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DE19617377 1996-04-30
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
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

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

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FR2774752B1 (en) * 1998-02-06 2000-06-16 Air Liquide AIR DISTILLATION SYSTEM AND CORRESPONDING COLD BOX

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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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ES2170951T3 (en) 2002-08-16
DE19617377A1 (en) 1997-11-06

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