EP0944588A1 - Suspension crystallization method - Google Patents

Suspension crystallization method

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Publication number
EP0944588A1
EP0944588A1 EP97952810A EP97952810A EP0944588A1 EP 0944588 A1 EP0944588 A1 EP 0944588A1 EP 97952810 A EP97952810 A EP 97952810A EP 97952810 A EP97952810 A EP 97952810A EP 0944588 A1 EP0944588 A1 EP 0944588A1
Authority
EP
European Patent Office
Prior art keywords
mother liquor
separated
suspension
crystallization
crystal phase
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.)
Withdrawn
Application number
EP97952810A
Other languages
German (de)
French (fr)
Inventor
Rüdiger DROPE
Dieter Grenner
Hartmut Hetzel
Hans-Peter Schal
Gerhard Wegener
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.)
Bayer AG
Original Assignee
Bayer AG
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Bayer AG filed Critical Bayer AG
Publication of EP0944588A1 publication Critical patent/EP0944588A1/en
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/0004—Crystallisation cooling by heat exchange
    • B01D9/0013—Crystallisation cooling by heat exchange by indirect heat exchange
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/004—Fractional crystallisation; Fractionating or rectifying columns
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/0059—General arrangements of crystallisation plant, e.g. flow sheets
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C263/00—Preparation of derivatives of isocyanic acid
    • C07C263/18—Separation; Purification; Stabilisation; Use of additives
    • C07C263/20—Separation; Purification
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2601/00—Systems containing only non-condensed rings
    • C07C2601/12—Systems containing only non-condensed rings with a six-membered ring
    • C07C2601/14—The ring being saturated

Definitions

  • the present invention relates to a method for separating crystallizable organic compounds from a liquid compound mixture by suspension crystallization.
  • organic compounds are generally obtained in the form of a compound mixture which, in addition to the desired organic compounds, has substantial or predominant proportions of other compounds, such as solvents, starting compounds, by-products and / or isomers of the organic compound.
  • the desired organic compound can be separated from the mixture by crystallization.
  • a characteristic of many crystallizable organic compounds is the low solid-phase solubility of foreign substances, so that crystallization is often the means of choice for the separation.
  • Common prior art methods include crystallization from solution or static crystallization from the compound mixture itself, in which the compound to be isolated is deposited on fixed, cooled surfaces, then separated from the mother liquor and melted again.
  • suspension crystallization processes are particularly suitable for aqueous systems, such as the removal of water from food liquids from US Pat. Nos. 4,004,886, 4,316,368, 4,430,104 and 4,459,144 loading knows. Furthermore, according to US Pat. No. 4,787,985, suspension crystallization processes for cleaning chemicals in several stages have already been proposed.
  • the washing column has the task of completely separating the resulting pure crystal phase from the mother liquor.
  • the crystal slurry is introduced into the column from below, compacted by a tamper designed as a sieve plate, the mother liquor flowing out through the sieve plate below and a compacted crystal block being formed above the sieve plate.
  • crystals freed from the mother liquor are scraped off the crystal block by means of a scraper, melted and discharged.
  • a liquid pressure of the melted crystals is maintained above the crystal block such that a small amount of the liquid is pressed through the crystal block to wash out adhering mother liquor.
  • the purity of the separated crystal phase depends to a large extent on the temperature difference between the melting temperature of the crystals and the temperature of the crystal slurry fed to the washing column.
  • Such washing columns can therefore advantageously only be operated up to temperature differences of 5 to a maximum of 10 ° C. between the crystal suspension supplied and the melted pure phase.
  • Mixtures of organic compounds are obtained in mixing ratios which, insofar as they are accessible for separation by crystallization, have a liquidus temperature, the difference from the melting temperature of the crystal phase to be separated is considerably greater.
  • the temperature of the crystal slurry to be fed to the washing column can only be raised to the required temperature difference by redissolving considerable amounts of the crystal phase, ie by increasing the concentration of the mother liquor in the crystal suspension the compound to be separated by crystallization is increased by supplying heat by redissolving the crystal phase in such a way that the liquidus temperature has a tolerable temperature difference from the melting temperature for the phase-pure separation of the crystal phase.
  • the present invention relates to a process for separating a crystallizable compound from a liquid compound mixture by single- or multi-stage suspension crystallization, the crystals behind the last stage being separated off by a washing column and a mother liquor depleted in the compound to be separated off by crystallization being discharged from the first stage is characterized in that the crystal phase is separated from the suspension before the introduction of the suspension into the washing column and is resuspended in a mother liquor whose liquidus temperature is not more than 8.5 ° C below the melting temperature of the crystal phase.
  • the crystal phase is preferably separated from the suspension in such a way that the crystal phase is still dripping wet with the suspension medium.
  • the crystal phase separated from the suspension can preferably also contain 5 to 10% by weight of suspension medium.
  • Suitable means for separating the crystal phase are sieves and filters.
  • sieves and filters For example, belt filters, drum filters, serpentine screws, curved sieves or similar devices suitable in the art for the continuous separation of solids from liquids can be used.
  • the separated crystal phase is conveyed immediately after the separation into a mixing container into which the mother liquor is also introduced for resuspending.
  • the starting compound mixture can be used as the resuspending mother liquor if its liquidus temperature is not more than 8.5 ° C. below the melting temperature of the crystal phase to be separated off.
  • a starting compound mixture is preferably used as the resuspending mother liquor, which is enriched by adding the crystallizable compound to be separated, in such a way that the resuspending mother liquor has the required liquidus temperature .
  • the enriched resuspending mother liquor is then returned to the mixing vessel after the crystals have been separated off in the washing column, using only an amount equal to the amount of suspension medium still adhering to the crystals after separation plus the amount of crystals to be remelted for the re-enrichment of the resuspending mother liquor is removed from the resuspending mother liquor cycle and returned to the crystallizer.
  • the invention can be used particularly advantageously if the liquidus temperature of the starting isomer mixture is less than 8 ° C. below the melting temperature of the crystal phase to be separated.
  • Another preferred area of application of the invention relates to the case that the liquidus temperature of the starting isomer mixture is sufficiently close to the melting temperature of the crystal phase, but that the mother liquor to be discharged, which is depleted in the crystallized phase, has such a low concentration of crystallized compound, i.e. that so much crystal phase was generated that its resuspension in the starting isomer mixture does not lead to a pumpable suspension.
  • the resuspending mother liquor is preferably fed to the mixing vessel at a temperature such that, after mixing with the separated crystal phase, there is undersaturation in the mixing vessel, ie the mixing temperature is above the liquidus temperature of the mixture.
  • the undersaturation should be such that just as much crystal phase is melted (or dissolved) that the resuspending mother liquor composition is maintained.
  • the melt phase re-melted in the mixing container is preferably less than 10% of the crystal phase introduced in the mixing container from 2 to 8%, more preferably between 4 and 8%
  • the process according to the invention was developed in the course of investigations into the isomer separation of isocyanates, but is generally also outstandingly suitable for other systems.
  • the conditions for the isomer separation of isocyanates are given below
  • T 100 2,4-TDI
  • T 67 The melting temperature of T 100 is 22 ° C
  • the liquidus temperature of the starting isomer mixture T 80 is 13.5 ° C.
  • the liquidus temperature of an isomer mixture of 67% 2,4-TDI and 33% 2,6-TDI is at 6.3 ° C.
  • the crystal suspension emerging from the installer or, if appropriate, the downstream recrystallizer points a temperature of 6.3 ° C and a composition of the suspension medium of
  • the ball suspension is fed to a belt filter, in which the crystals are separated from the suspension. Smaller crystals remain in the suspension medium and are returned to the crystallizer with this.
  • the crystals separated from the suspension are dripping wet, i.e. with about 8% adhering T 67 in one Mixing container initiated, into which the starting isomer mixture is simultaneously introduced at a temperature of 16 ° C.
  • the liquidus temperature of the mixture after remelting 3% of the crystals is around 13 ° C.
  • the mixture is fed to the wash column.
  • T 100 parts of the starting isomer mixture and 39.4 parts of T 100 are removed at the top of the washing column.
  • the resuspension mother liquor is introduced into the crystallizer from the wash column. 60.6 parts of T 67 are discharged from the crystallizer per 100 parts of starting isomer mixture.
  • MDI is obtained as a starting isomer mixture with 90% 4,4'-MDI and 10% 2,4'-MDI, although minor amounts of 2,2 '-MDI may still be present.
  • Starting isomer mixture is approx. 36 ° C.
  • the pure 4,4'-MDI has a melting point of 40 ° C.
  • the isomer mixture depleted in 4,4'-MDI still has 55% by weight 4,4'-MDI with a liquidus temperature of 18 ° C.
  • the crystal suspension leaving the crystallizer, from which the crystals are separated has a temperature of 18 ° C.
  • the separated crystals are fed to a mixing vessel, to which the starting isomer mixture is simultaneously fed at a temperature of 50 ° C. and 70 parts of resuspending mother liquor per 100 parts of starting isomer mixture from the washing column at 34 ° C.
  • the starting isomer mixture is introduced directly into the crystallizer.
  • a starting isomer mixture is used as the resuspending mother liquor, which is obtained by admixing pure t, t-rMDI contains 90% t, t-rMDI
  • In the mixer 7.5% of the crystals to compensate for the dilution of the resuspending mother liquor by the crystals still adhering to t, t-rMDI-depleted isomer mixture are dissolved at the top of the wash column 37.5 parts of t, t-rMDI are discharged per 100 parts of starting isomer mixture.
  • the resuspending mother liquor is heated up to 90% again and in the mixing tank returned to the container and 10% fed to the crystallizer.
  • FIG. 1 schematically shows a crystallizer 1 in which heat is withdrawn via the cooling jacket 2 of the crystal suspension therein.
  • the cooling jacket 2 is cooled via the cow unit 3.
  • the crystal suspension is fed via line 4 to a belt filter 5, shown as an example of a separating agent, from which the crystals pass into the mixing container 6.
  • the mother liquor separated from the crystal suspension is returned to the crystallizer via line 14.
  • the mixing vessel 6 the resuspending mother liquor in the form of the starting isomer mixture is simultaneously introduced via line 20. Crystals suspended in the starting isomer mixture are fed via line 17 and the reciprocating pump 9 above the sieve plate 8, which is periodically moved by the reciprocating pump, to the washing column 7 below Sieve plate 8 the mother liquor flows off and is fed to the crystallizer via line 18.
  • FIG. 1 shows an embodiment of the present invention in which the starting isomer mixture is fed to the crystallizer via line 22.
  • the resuspending mother liquor is circulated via line 20, heat exchanger 21 and line 17 between washing column 7 and mixing container 6, with a subordinate one
  • the embodiment of the invention according to FIG. 2 is suitable for the isomer separation of r-MDI described above.
  • FIG. 3 shows a further embodiment of the present invention, in which the starting isomer mixture is introduced into the mixing container 6 via arrow 22 and furthermore a part of the resuspending mother liquor is recirculated between the mixing container 6 and the washing column 7 via line 24 and line 17. 3 is particularly suitable for the isomer separation of MDI.

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  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Extraction Or Liquid Replacement (AREA)

Abstract

The invention concerns a method of separating a crystallizable organic compound from a liquid compound mixture by means of a single- or multi-stage suspension crystallization method, the crystals behind the final stage being separated by a washing column and a mother liquor, which is depleted of the compound to be separated by crystallization, being channelled out of the first stage. The method is characterized in that the crystal phase is separated out of the suspension before the suspension is introduced into the washing column and is resuspended in a mother liquor whose liquidus temperature is no more than 8.5 DEG C below the melt temperature of the crystal phase.

Description

Verfahren zur SuspensionskristallisationSuspension crystallization process
Die vorliegende Erfindung betrifft ein Verfahren zur Abtrennung von kristallisierbaren organischen Verbindungen aus einem flüssigen Verbindungsgemisch durch Suspensionskristallisation.The present invention relates to a method for separating crystallizable organic compounds from a liquid compound mixture by suspension crystallization.
Organische Verbindungen fallen aufgrund ihres Syntheseprozesses im allgemeinen in Form eines Verbindungsgemisches an, das neben den gewünschten organischen Ver- bindungen erhebliche bzw. überwiegende Anteile anderer Verbindungen wie Lösungsmittel, Ausgangsverbindungen, Nebenprodukte und/oder Isomere der organischen Verbindung besitzt. In vielen Fällen ist die gewünschte organische Verbindung durch Kristallisation aus dem Gemisch abtrennbar. Ein Charakteristikum vieler kristallisierbarer organischer Verbindungen ist die geringe Festphasenlöslichkeit von Fremdsub- stanzen, so daß die Kristallisation häufig das Mittel der Wahl für die Trennung ist.Because of their synthesis process, organic compounds are generally obtained in the form of a compound mixture which, in addition to the desired organic compounds, has substantial or predominant proportions of other compounds, such as solvents, starting compounds, by-products and / or isomers of the organic compound. In many cases, the desired organic compound can be separated from the mixture by crystallization. A characteristic of many crystallizable organic compounds is the low solid-phase solubility of foreign substances, so that crystallization is often the means of choice for the separation.
Übliche Verfahren des Standes der Technik sind u.a. die Kristallisation aus Lösung oder die statische Kristallisation aus dem Verbindungsgemisch selbst, bei dem die zu isolierende Verbindung an feststehenden gekühlten Flächen abgeschieden, anschlie- ßend von der Mutterlauge getrennt und wieder aufgeschmolzen wird.Common prior art methods include crystallization from solution or static crystallization from the compound mixture itself, in which the compound to be isolated is deposited on fixed, cooled surfaces, then separated from the mother liquor and melted again.
Beide Kristallisationsverfahren erfordern einen hohen Energieeinsatz, da die für die Kristallisation zu kühlende bzw. wieder aufzuheizende Masse die Masse der eigentlich zu trennenden Partner erheblich übersteigt.Both crystallization processes require high energy input, since the mass to be cooled or reheated for the crystallization considerably exceeds the mass of the partners actually to be separated.
Energetisch günstiger und mit besserem Trenneffekt als statische Kristallisationsverfahren lassen sich im allgemeinen Kristallisationsverfahren in Suspension durchfuhren, wenn für die Abtrennung und Aufschmelzung der Kristallphase sogenannte Waschsäulen gemäß US-A 3 777 892 und US-A 3 872 009 eingesetzt werden.Energy-efficient and with a better separation effect than static crystallization processes can generally be carried out in suspension crystallization processes if so-called washing columns according to US Pat. Nos. 3,777,892 and 3,872,009 are used for the separation and melting of the crystal phase.
Grundsätzlich sind solche Suspensionskristallisationsverfahren insbesondere für wäss- rige Systeme, wie z.B. dem Entzug von Wasser aus Lebensmittel-Flüssigkeiten aus den US-A 4 004 886, US-A 4 316 368, US-A 4 430 104 und US-A 4 459 144 be- kannt. Ferner wurden gemäß US-A 4 787 985 bereits Suspensionskristallisationsver- fahren zur Reinigung von Chemikalien in mehreren Stufen vorgeschlagen.Fundamentally, such suspension crystallization processes are particularly suitable for aqueous systems, such as the removal of water from food liquids from US Pat. Nos. 4,004,886, 4,316,368, 4,430,104 and 4,459,144 loading knows. Furthermore, according to US Pat. No. 4,787,985, suspension crystallization processes for cleaning chemicals in several stages have already been proposed.
Allen diesen Verfahren gemeinsam ist, daß sie (bei mehrstufiger Kristallisation je Stufe) einen Kristallisationsbehälter, in dem durch Wärmeentzug Kristalle ausgefroren werden, einen Rekristallisationsbehälter, in dem größere Kristalle zu Lasten der kleineren wachsen, und einen Filter, in dem die Kristalle von der Mutterlauge getrennt werden, aufweisen. Zumindest der Filter der letzten Stufe ist als Waschsäule ausgebildet.Common to all of these processes is that they (in the case of multi-stage crystallization per stage) have a crystallization container in which crystals are frozen out by means of heat removal, a recrystallization container in which larger crystals grow at the expense of the smaller ones, and a filter in which the crystals are removed from the mother liquor be separated. At least the filter of the last stage is designed as a wash column.
Die Waschsäule hat die Aufgabe, die anfallende reine Kristallphase vollständig von der Mutterlauge zu trennen. Dabei wird der Kristallbrei von unten in die Säule eingeführt, durch einen als Siebplatte ausgebildeten Stampfer kompaktiert, wobei die Mutterlauge durch die Siebplatte unten abfließt und sich oberhalb der Siebplatte ein kompaktierter Kristallblock ausbildet. Oberhalb des Kristallblocks werden mittels eines Schabers von der Mutterlauge befreite Kristalle von dem Kristallblock abgeschabt, aufgeschmolzen und ausgeschleust. Dabei wird oberhalb des Kristallblocks ein solcher Flüssigkeitsdruck der aufgeschmolzenen Kristalle aufrecht erhalten, daß eine geringe Menge der Flüssigkeit durch den Kristallblock zur Auswaschung von anhaftender Mutterlauge gedrückt wird. Die Reinheit der abgetrennten Kristallphase hängt in starkem Maße von der Temperaturdifferenz zwischen der Schmelztemperatur der Kristalle und der Temperatur des der Waschsäule zugeführten Kristallbreis ab. Daher können solche Waschsäulen lediglich bis zu Temperaturdifferenzen von 5 bis maximal 10°C zwischen zugeführter Kristallsuspension und aufgeschmolzener reiner Phase vorteilhaft betrie- ben werden.The washing column has the task of completely separating the resulting pure crystal phase from the mother liquor. The crystal slurry is introduced into the column from below, compacted by a tamper designed as a sieve plate, the mother liquor flowing out through the sieve plate below and a compacted crystal block being formed above the sieve plate. Above the crystal block, crystals freed from the mother liquor are scraped off the crystal block by means of a scraper, melted and discharged. A liquid pressure of the melted crystals is maintained above the crystal block such that a small amount of the liquid is pressed through the crystal block to wash out adhering mother liquor. The purity of the separated crystal phase depends to a large extent on the temperature difference between the melting temperature of the crystals and the temperature of the crystal slurry fed to the washing column. Such washing columns can therefore advantageously only be operated up to temperature differences of 5 to a maximum of 10 ° C. between the crystal suspension supplied and the melted pure phase.
Gemische organischer Verbindungen fallen dagegen in Mischungsverhältnissen an, die, soweit sie überhaupt der Trennung durch Kristallisation zugängig sind, eine Liquidustemperatur aufweisen, deren Differenz zur Schmelztemperatur der abzutren- nenden Kristallphase erheblich größer ist. Die Temperatur des der Waschsäule zuzuführenden Kristallbreis kann in solchen Fällen nur dadurch auf die erforderliche Temperaturdifferenz angehoben werden, daß erhebliche Mengen an Kristallphase zurückgelöst werden, d.h. daß die Konzentration der Mutterlauge der Kristallsuspension an der durch Kristallisation abzutrennenden Verbindung durch Zufuhr von Wärme durch Rücklösung von Kristallphase derart erhöht wird, daß die Liquidustemperatur eine für die phasenreine Abtrennung der Kristallphase tolerierbare Temperaturdifferenz zur Schmelztemperatur aufweist.Mixtures of organic compounds, on the other hand, are obtained in mixing ratios which, insofar as they are accessible for separation by crystallization, have a liquidus temperature, the difference from the melting temperature of the crystal phase to be separated is considerably greater. In such cases, the temperature of the crystal slurry to be fed to the washing column can only be raised to the required temperature difference by redissolving considerable amounts of the crystal phase, ie by increasing the concentration of the mother liquor in the crystal suspension the compound to be separated by crystallization is increased by supplying heat by redissolving the crystal phase in such a way that the liquidus temperature has a tolerable temperature difference from the melting temperature for the phase-pure separation of the crystal phase.
Erfindungsgemäß wird nun vorgeschlagen, die Kristalle aus der Kristallsuspension vor der Einfuhrung in die Waschsäule abzutrennen und in einer Mutterlauge zu resuspendieren, deren Liquidustemperatur maximal 8,5°C unterhalb der Schmelztemperatur der abzutrennenden Kristalle liegt.According to the invention, it is now proposed to separate the crystals from the crystal suspension before introduction into the washing column and to resuspend them in a mother liquor whose liquidus temperature is a maximum of 8.5 ° C. below the melting temperature of the crystals to be separated off.
Gegenstand der vorliegenden Erfindung ist ein Verfahren zur Abtrennung einer kristallisierbaren Verbindung aus einem flüssigen Verbindungsgemisch durch ein- oder mehrstufige Suspensionskristallisation, wobei die Kristalle hinter der letzten Stufe durch eine Waschsäule abgetrennt werden und aus der ersten Stufe eine an der durch Kristallisation abzutrennenden Verbindung abgereicherte Mutterlauge ausgeschleust wird, das dadurch gekennzeichnet ist, daß die Kristallphase vor der Einleitung der Suspension in die Waschsäule aus der Suspension separiert wird und in einer Mutterlauge resuspendiert wird, deren Liquidustemperatur nicht mehr als 8,5°C unterhalb der Schmelztemperatur der Kristallphase liegt.The present invention relates to a process for separating a crystallizable compound from a liquid compound mixture by single- or multi-stage suspension crystallization, the crystals behind the last stage being separated off by a washing column and a mother liquor depleted in the compound to be separated off by crystallization being discharged from the first stage is characterized in that the crystal phase is separated from the suspension before the introduction of the suspension into the washing column and is resuspended in a mother liquor whose liquidus temperature is not more than 8.5 ° C below the melting temperature of the crystal phase.
Die Separation der Kristallphase aus der Suspension erfolgt vorzugsweise derart, daß die Kristallphase noch tropfnaß von dem Suspensionsmedium behaftet ist. Vorzugsweise kann die von der Suspension separierte Kristallphase noch 5 bis 10 Gew.-% an Suspensionsmedium enthalten.The crystal phase is preferably separated from the suspension in such a way that the crystal phase is still dripping wet with the suspension medium. The crystal phase separated from the suspension can preferably also contain 5 to 10% by weight of suspension medium.
Geeignete Mittel zur Separation der Kristallphase sind Siebe und Filter. Beispielsweise können Bandfilter, Trommelfilter, Seiherschnecken, Bogensiebe oder ähnliche in der Technik für die kontinuierliche Abtrennung von Feststoffen aus Flüssigkeiten geeignete Vorrichtungen eingesetzt werden.Suitable means for separating the crystal phase are sieves and filters. For example, belt filters, drum filters, serpentine screws, curved sieves or similar devices suitable in the art for the continuous separation of solids from liquids can be used.
Die abgetrennte Kristallphase wird unmittelbar im Anschluß an die Abtrennung in einen Mischbehälter befördert, in den auch die Mutterlauge zur Resuspendierung eingeleitet wird. Als Resuspendierungs-Mutterlauge kann das Ausgangsverbindungsgemisch eingesetzt werden, wenn dessen Liquidustemperatur nicht mehr als 8,5°C unterhalb der Schmelztemperatur der abzutrennenden Kristallphase liegt.The separated crystal phase is conveyed immediately after the separation into a mixing container into which the mother liquor is also introduced for resuspending. The starting compound mixture can be used as the resuspending mother liquor if its liquidus temperature is not more than 8.5 ° C. below the melting temperature of the crystal phase to be separated off.
Ist die Differenz zwischen Schmelztemperatur der Kristallphase und Liquidustemperatur des Ausgangsverbindungsgemisches größer als 8,5°C, wird als Resuspendierungs- Mutterlauge vorzugsweise ein Ausgangsverbindungsgemisch eingesetzt, daß durch Zugabe der abzutrennenden kristallisierbaren Verbindung angereichert ist, derart, daß die Resuspendierungs-Mutterlauge die geforderte Liquidustemperatur aufweist. Die angereicherte Resuspendierungs-Mutterlauge wird dann nach Abtrennung der Kristalle in der Waschsäule zu dem Mischbehälter zurückgeführt, wobei lediglich eine Menge, die der den Kristallen nach Separation noch anhaftenden Menge an Suspensionsmedium zuzüglich der für die Wiederanreicherung der Resuspendierungs-Mutterlauge erforderlichen Menge an wiederaufzuschmelzenden Kristallen aus dem Resus- pendierungs-Mutterlaugen-Kreislauf ausgeschleust und zum Kristallisator zurückgeführt wird.If the difference between the melting temperature of the crystal phase and the liquidus temperature of the starting compound mixture is greater than 8.5 ° C., a starting compound mixture is preferably used as the resuspending mother liquor, which is enriched by adding the crystallizable compound to be separated, in such a way that the resuspending mother liquor has the required liquidus temperature . The enriched resuspending mother liquor is then returned to the mixing vessel after the crystals have been separated off in the washing column, using only an amount equal to the amount of suspension medium still adhering to the crystals after separation plus the amount of crystals to be remelted for the re-enrichment of the resuspending mother liquor is removed from the resuspending mother liquor cycle and returned to the crystallizer.
Die Erfindung kann insbesondere dann vorteilhaft eingesetzt werden, wenn die Liquidustemperatur der Ausgangsisomerenmischung weniger als 8°C unterhalb der Schmelztemperatur der abzutrennenden Kristallphase liegt.The invention can be used particularly advantageously if the liquidus temperature of the starting isomer mixture is less than 8 ° C. below the melting temperature of the crystal phase to be separated.
Ein weiteres bevorzugtes Einsatzgebiet der Erfindung betrifft den Fall, daß zwar die Liquidustemperatur der Ausgangsisomerenmischung ausreichend nahe an der Schmelztemperatur der Kristallphase liegt, daß aber die auszuschleusende, an der kri- stallisierten Phase verarmte Mutterlauge eine so geringe Konzentration an kristallisierter Verbindung aufweist, d.h. daß soviel Kristallphase erzeugt wurde, daß deren Resuspendierung in der Ausgangsisomerenmischung nicht zu einer pumpfähigen Suspension führt.Another preferred area of application of the invention relates to the case that the liquidus temperature of the starting isomer mixture is sufficiently close to the melting temperature of the crystal phase, but that the mother liquor to be discharged, which is depleted in the crystallized phase, has such a low concentration of crystallized compound, i.e. that so much crystal phase was generated that its resuspension in the starting isomer mixture does not lead to a pumpable suspension.
Vorzugsweise erfolgt die Zufuhr der Resuspendierungs-Mutterlauge zum Mischbehälter bei einer derartigen Temperatur, daß nach Vermischung mit der separierten Kristallphase im Mischbehälter eine Untersättigung vorliegt, d.h. daß die Mischungstemperatur oberhalb der Liquidustemperatur der Mischung liegt. Die Untersättigung soll derart bemessen sein, daß gerade so viel Kristallphase aufgeschmolzen (bzw aufgelost) wird, daß die Resuspendierungs-Mutterlaugen-Zusammensetzung aufrecht erhalten wird Die im Mischbehalter wieder aufgeschmolzene Kπstallphase betragt vorzugsweise weniger als 10 % der in dem Mischbehalter eingeführten Kristallphase Insbesondere bevorzugt ist eine Aufschmelzrate von 2 bis 8 %, weiter bevorzugt zwischen 4 und 8 %The resuspending mother liquor is preferably fed to the mixing vessel at a temperature such that, after mixing with the separated crystal phase, there is undersaturation in the mixing vessel, ie the mixing temperature is above the liquidus temperature of the mixture. The undersaturation should be such that just as much crystal phase is melted (or dissolved) that the resuspending mother liquor composition is maintained.The melt phase re-melted in the mixing container is preferably less than 10% of the crystal phase introduced in the mixing container from 2 to 8%, more preferably between 4 and 8%
Das erfindungsgemaße Verfahren wurde im Rahmen von Untersuchungen zur Isomerentrennung von Isocyanaten entwickelt, ist jedoch allgemeiner auch für andere Systeme hervorragend geeignet Beispielsweise werden nachfolgend die Bedingungen zur Isomerentrennung von Isocyanaten angegebenThe process according to the invention was developed in the course of investigations into the isomer separation of isocyanates, but is generally also outstandingly suitable for other systems. For example, the conditions for the isomer separation of isocyanates are given below
1 Toluylendnsocyanat (TDI)1 toluene end isocyanate (TDI)
TDI entsteht aufgrund des Herstellungsprozesses als eine Mischung, enthaltend 80 % 2,4-TDI und 20 % 2,6-TDI Aufgrund des unterschiedlichen Reak- tionsverhaltens der Isomeren beim Polyisocyanatpolyadditionsverfahren zur Herstellung von Polyurethanen werden technisch sowohl reines 2,4-TDI (T 100) als auch eine Mischung aus 65 bis 69 % 2,4-TDI und 35 bis 31 % 2,6- TDI (T 67) eingesetzt Die Schmelztemperatur von T 100 betragt 22°C DieDue to the manufacturing process, TDI is produced as a mixture containing 80% 2,4-TDI and 20% 2,6-TDI. Due to the different reaction behavior of the isomers in the polyisocyanate polyaddition process for the production of polyurethanes, technically both pure 2,4-TDI (T 100) as well as a mixture of 65 to 69% 2,4-TDI and 35 to 31% 2,6-TDI (T 67). The melting temperature of T 100 is 22 ° C
Liquidustemperatur der Ausgangsisomerenmischung T 80 betragt 13,5°C Die Liquidustemperatur einer Isomerenmischung aus 67 % 2,4-TDI und 33 % 2,6- TDI egt bei 6,3°C Die aus dem Kπstallisator bzw gegebenenfalls dem nachgeschalteten Rekristallisator austretende Kristallsuspension weist eine Tempe- ratur von 6,3 °C und eine Zusammensetzung des Suspensionsmediums vonThe liquidus temperature of the starting isomer mixture T 80 is 13.5 ° C. The liquidus temperature of an isomer mixture of 67% 2,4-TDI and 33% 2,6-TDI is at 6.3 ° C. The crystal suspension emerging from the installer or, if appropriate, the downstream recrystallizer points a temperature of 6.3 ° C and a composition of the suspension medium of
67 % 2,4-TDI und 33 % 2,6-TDI auf, das T 100-Kπstalie enthalt Durch entsprechende Mengenstromsteuerung kann gewährleistet werden, daß die Kri- stallsuspension einen Feststoffgehalt von 20 bis 35 Gew %, vorzugsweise etwa 30 Gew -% aufweist Die Knstallsuspension wird einem Bandfilter zugeführt, in dem die Kristalle von der Suspension getrennt werden Kleinere Kristalle verbleiben im Suspensionsmedium und werden mit diesem in den Kπstalhsator zurückgeführt Die von der Suspension separierten Kristalle werden tropfnaß, d h mit noch etwa 8 % anhaftendem T 67 in einem Mischbehalter eingeleitet, in den gleichzeitig die Ausgangsisomerenmischung bei einer Temperatur von 16°C eingeleitet wird. Die Liquidustemperatur der Mischung liegt nach Rückschmelzen von 3 % der Kristalle bei etwa 13°C. Die Mischung wird der Waschsäule zugeführt. Am Kopf der Waschsäule werden je 100 Teile Ausgangsisomerenmischung, 39,4 Teile T 100 ausgeschleust. Die Resuspensions- Mutterlauge wird von der Waschsäule in den Kristallisator eingeleitet. Aus dem Kristallisator werden je 100 Teile Ausgangsisomerenmischung 60,6 Teile T 67 ausgeschleust.67% 2,4-TDI and 33% 2,6-TDI, which contains T 100 crystals. Appropriate flow control can ensure that the crystal suspension has a solids content of 20 to 35% by weight, preferably about 30% by weight. The ball suspension is fed to a belt filter, in which the crystals are separated from the suspension. Smaller crystals remain in the suspension medium and are returned to the crystallizer with this. The crystals separated from the suspension are dripping wet, i.e. with about 8% adhering T 67 in one Mixing container initiated, into which the starting isomer mixture is simultaneously introduced at a temperature of 16 ° C. The liquidus temperature of the mixture after remelting 3% of the crystals is around 13 ° C. The mixture is fed to the wash column. 100 parts of the starting isomer mixture and 39.4 parts of T 100 are removed at the top of the washing column. The resuspension mother liquor is introduced into the crystallizer from the wash column. 60.6 parts of T 67 are discharged from the crystallizer per 100 parts of starting isomer mixture.
Diphenylmethandiisocyanat (MDI)Diphenylmethane diisocyanate (MDI)
MDI fällt aufgrund des Herstellungsprozesses als Ausgangsisomerenmischung mit 90 % 4,4'-MDI und 10 % 2,4'-MDI an, wobei noch untergeordnete Mengen an 2,2' -MDI vorhanden sein können. Die Liquidustemperatur derDue to the manufacturing process, MDI is obtained as a starting isomer mixture with 90% 4,4'-MDI and 10% 2,4'-MDI, although minor amounts of 2,2 '-MDI may still be present. The liquidus temperature of the
Ausgangsisomerenmischung beträgt ca. 36°C. Das reine 4,4'-MDI weist einen Schmelzpunkt von 40°C auf. Die auszuschleusende, an 4,4'-MDI abgerei- cherte Isomerenmischung weist noch 55 Gew.-% 4,4'-MDI mit einer Liquidustemperatur von 18°C auf. Entsprechend hat die den Kristallisator verlas- sende Kristallsuspension, aus der die Kristalle separiert werden, eine Temperatur von 18°C. Die separierten Kristalle werden einem Mischbehälter zugeführt, dem gleichzeitig die Ausgangsisomerenmischung bei einer Temperatur von 50°C und pro 100 Teile Ausgangsisomerenmischung 70 Teile Resuspendierungs-Mutterlauge von der Waschsäule bei 34°C zugeführt wird. Am Kopf der Mischsäule werden pro 100 Teilen Ausgangsisomerenmischung 77 Teile 4,4'-Starting isomer mixture is approx. 36 ° C. The pure 4,4'-MDI has a melting point of 40 ° C. The isomer mixture depleted in 4,4'-MDI still has 55% by weight 4,4'-MDI with a liquidus temperature of 18 ° C. Accordingly, the crystal suspension leaving the crystallizer, from which the crystals are separated, has a temperature of 18 ° C. The separated crystals are fed to a mixing vessel, to which the starting isomer mixture is simultaneously fed at a temperature of 50 ° C. and 70 parts of resuspending mother liquor per 100 parts of starting isomer mixture from the washing column at 34 ° C. At the top of the mixing column, 77 parts of 4,4'-
MDI ausgeschleust. Vom Ablauf der Waschsäule werden 110 Teile Resuspendierungs-Mutterlauge in den Kristallisator eingeleitet und 70 Teile in den Mischbehälter zurückgeführt.MDI removed. From the wash column outlet, 110 parts of resuspending mother liquor are introduced into the crystallizer and 70 parts are returned to the mixing container.
Dicyclohexylmethandiisocyanat (rMDI)Dicyclohexylmethane diisocyanate (rMDI)
Dicyclohexylmethandiisocyanat fällt aufgrund des Herstellungsprozesses zu 50 % in der trans-trans-, 40 % in der cis-trans- und zu 10 % in der cis-cis- Form an Ferner sind untergeordnete Mengen an ortho-Dicyclohexylmethandi- lsocyanat anwesend Die Liquidustemperatur der Ausgangsisomerenmischung liegt bei ca 54°C Das reine trans-trans-Dicyclohexylmethandiisocyanat (t,t-rMDI) hat eine Schmelztemperatur von 83°C Eine an t,t-rMDI abgerei- cherte Isomerenmischung, die noch 20 % t,t-rMDI enthält, hat eine Liquidustemperatur von 14,5°C Die Ausgangsisomerenmischung wird direkt in den Kristallisator eingeleitet Als Resuspendierungs-Mutterlauge wird eine Ausgangsisomerenmischung eingesetzt, die durch Zumischen von reinem t,t-rMDI einen Gehalt an 90 % t,t-rMDI aufweist Im Mischer werden 7,5 % der Kristalle zur Kompensation der Verdünnung der Resuspendierungs-Mutterlauge durch den Kristallen noch anhaftende, an t,t-rMDI abgereicherte Isomerenmischung aufgelost Am Kopf der Waschsaule werden je 100 Teile Ausgangsisomerenmischung 37,5 Teile t,t-rMDI ausgeschleust Die Resuspendierungs-Mutterlauge wird zu 90 % wieder aufgeheizt und in den Mischbehälter zurückgeführt und zu 10 % dem Kristallisator zugeführt.Due to the manufacturing process, 50% of dicyclohexylmethane diisocyanate falls in the trans-trans, 40% in the cis-trans and 10% in the cis-cis- Form on Furthermore, minor amounts of ortho-dicyclohexylmethane diisocyanate are present. The liquidus temperature of the starting isomer mixture is approximately 54 ° C. The pure trans-trans-dicyclohexylmethane diisocyanate (t, t-rMDI) has a melting temperature of 83 ° C. An an, t- rMDI-depleted isomer mixture, which still contains 20% t, t-rMDI, has a liquidus temperature of 14.5 ° C. The starting isomer mixture is introduced directly into the crystallizer. A starting isomer mixture is used as the resuspending mother liquor, which is obtained by admixing pure t, t-rMDI contains 90% t, t-rMDI In the mixer, 7.5% of the crystals to compensate for the dilution of the resuspending mother liquor by the crystals still adhering to t, t-rMDI-depleted isomer mixture are dissolved at the top of the wash column 37.5 parts of t, t-rMDI are discharged per 100 parts of starting isomer mixture. The resuspending mother liquor is heated up to 90% again and in the mixing tank returned to the container and 10% fed to the crystallizer.
Die Erfindung wird nachfolgend anhand der beigefugten Figuren naher erläutertThe invention is explained in more detail below with the aid of the attached figures
Fig 1 zeigt schematisch einen Kristallisator 1, in dem über den Kuhlmantel 2 der darin befindlichen Kristallsuspension Warme entzogen wird. Der Kuhlmantel 2 wird über das Kuhlaggregat 3 gekühlt. Die Kristallsuspension wird über Leitung 4 einem beispielhaft als Separationsmittel dargestellten Bandfilter 5 zugeführt, aus dem die Kristalle in den Mischbehalter 6 gelangen Die von der Kristallsuspension getrennte Mutterlauge wird über Leitung 14 in den Kristallisator zurückgeführt. In dem Misch- behalter 6 wird gleichzeitig kontinuierlich die Resuspendierungs-Mutterlauge in Form der Ausgangsisomerenmischung über Leitung 20 eingeleitet Wie in der Ausgangsisomerenmischung suspendierten Kristalle werden über Leitung 17 und die Hubkolbenpumpe 9 oberhalb der durch die Hubkolbenpumpe periodisch bewegte Siebplatte 8 der Waschsaule 7 zugeführt Unterhalb der Siebplatte 8 fließt die Mutterlauge ab und wird über Leitung 18 dem Kristallisator zugeführt Im Kopf der Waschsaule 7 befindet sich ein Kristallschaber 10, der von dem durch die Siebplatte kompaktierten Kristallblock Kristalle abschabt Die Kristalle werden in dem Wärmeaustauscher 11 zumindest teilweise aufgeschmolzen und über Pumpe 12 als Transportmittel für die ab- geschabten Kristalle und als Waschmedium dem Kopf der Waschsäule zurückgeführt. Der überwiegende Teil der zumindest teilweise aufgeschmolzenen reinen Kristalle wird entlang Pfeil 13 ausgeschleust. Die an der durch Kristallisation abzutrennenden Verbindung abgereicherte Kristallsuspension wird über Leitung 15 mittels Filter 16 aus dem Kristallisator ausgeschleust. Die in Fig. 1 dargestellte Ausfuhrungsform der vorliegenden Erfindung ist für die Isomerentrennung von TDI geeignet. Fig. 2 zeigt eine Ausführungsform der vorliegenden Erfindung, bei der die Ausgangsisomerenmischung über Leitung 22 dem Kristallisator zugeführt wird. Die Resuspendierungs- Mutterlauge wird über Leitung 20, Wärmeaustauscher 21 und Leitung 17 zwischen Waschsäule 7 und Mischbehälter 6 im Kreislauf gefahren, wobei ein untergeordneter1 schematically shows a crystallizer 1 in which heat is withdrawn via the cooling jacket 2 of the crystal suspension therein. The cooling jacket 2 is cooled via the cow unit 3. The crystal suspension is fed via line 4 to a belt filter 5, shown as an example of a separating agent, from which the crystals pass into the mixing container 6. The mother liquor separated from the crystal suspension is returned to the crystallizer via line 14. In the mixing vessel 6, the resuspending mother liquor in the form of the starting isomer mixture is simultaneously introduced via line 20. Crystals suspended in the starting isomer mixture are fed via line 17 and the reciprocating pump 9 above the sieve plate 8, which is periodically moved by the reciprocating pump, to the washing column 7 below Sieve plate 8 the mother liquor flows off and is fed to the crystallizer via line 18. In the head of the washing column 7 there is a crystal scraper 10 which scrapes crystals from the crystal block compacted by the sieve plate. The crystals are at least partially melted in the heat exchanger 11 and pump 12 as Means of transport for the scraped crystals and returned to the top of the washing column as a washing medium. The majority of the at least partially melted pure crystals are discharged along arrow 13. The depleted crystal suspension on the compound to be separated by crystallization is discharged from the crystallizer via line 15 by means of filter 16. The embodiment of the present invention shown in FIG. 1 is suitable for the isomer separation of TDI. FIG. 2 shows an embodiment of the present invention in which the starting isomer mixture is fed to the crystallizer via line 22. The resuspending mother liquor is circulated via line 20, heat exchanger 21 and line 17 between washing column 7 and mixing container 6, with a subordinate one
Anteil über Leitung 18 in den Kristallisator geleitet wird. Der untergeordnete Anteil entspricht der Menge an den im Bandfilter 5 separierten Kristallen anhaftenden abge- reicherten Mutterlauge und der im Mischer 6 wieder aufgeschmolzenen Kristallmenge zur Aufrechterhaltung der Zusammensetzung der im Kreislauf gefahrenen Suspendie- rungs-Mutterlauge. Die Ausfuhrungsform der Erfindung gemäß Fig. 2 ist für die vorher beschriebene Isomerentrennung von r-MDI geeignet.Share is fed via line 18 into the crystallizer. The minor portion corresponds to the amount of depleted mother liquor adhering to the band filter 5 separated crystals and the amount of crystals melted again in the mixer 6 to maintain the composition of the suspension mother liquor circulated. The embodiment of the invention according to FIG. 2 is suitable for the isomer separation of r-MDI described above.
Fig. 3 zeigt eine weitere Ausführungsform der vorliegenden Erfindung, bei der die Ausgangsisomerenmischung über Pfeil 22 in den Mischbehälter 6 eingeleitet wird und ferner ein Teil der Resuspendierungs-Mutterlauge über Leitung 24 und Leitung 17 zwischen Mischbehälter 6 und Waschsäule 7 rezirkuliert wird. Das Verfahren gemäß Fig. 3 ist insbesondere für die Isomerentrennung von MDI geeignet. FIG. 3 shows a further embodiment of the present invention, in which the starting isomer mixture is introduced into the mixing container 6 via arrow 22 and furthermore a part of the resuspending mother liquor is recirculated between the mixing container 6 and the washing column 7 via line 24 and line 17. 3 is particularly suitable for the isomer separation of MDI.

Claims

Patentansprüche claims
1. Verfahren zur Abtrennung einer kristallisierbaren organischen Verbindung aus einem flüssigen Verbindungsgemisch durch ein- oder mehrstufige Suspensi- onskristallisation, wobei die Kristalle hinter der letzten Stufe durch eine1. Process for the separation of a crystallizable organic compound from a liquid compound mixture by single- or multi-stage suspension crystallization, the crystals behind the last stage by a
Waschsäule abgetrennt werden und aus der ersten Stufe ein an der durch Kristallisation abzutrennenden Verbindung abgereicherte Mutterlauge ausgeschleust wird, dadurch gekennzeichnet, daß die Kristallphase vor der Einleitung der Suspension die Waschsäule aus der Suspension separiert wird und in einer Mutterlauge resuspendiert wird, deren Liquidustemperatur nicht mehr alsWash column are separated and a mother liquor depleted in the compound to be separated off by crystallization is discharged from the first stage, characterized in that the crystal phase is separated from the suspension before the suspension is introduced and the wash column is resuspended in a mother liquor whose liquidus temperature does not exceed
8,5°C unterhalb der Schmelztemperatur der Kristallphase liegt.8.5 ° C below the melting temperature of the crystal phase.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß die separierte Kristallphase in der Ausgangsisomerenmischung resuspendiert wird.2. The method according to claim 1, characterized in that the separated crystal phase is resuspended in the starting isomer mixture.
3. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß die separierte Kristallphase in einer Mutterlauge resuspendiert wird, wobei die Mutterlauge eine an der durch Kristallisation abzutrennenden Verbindung angereicherte Ausgangsisomerenmischung ist, wobei die Resuspendierungs-Mutterlauge zwischen Waschsäule und Resuspendierungs-Gefäß rezirkuliert wird.3. The method according to claim 1, characterized in that the separated crystal phase is resuspended in a mother liquor, the mother liquor being a starting isomer mixture enriched in the compound to be separated by crystallization, the resuspending mother liquor being recirculated between the washing column and the resuspending vessel.
4. Verfahren nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß die Kristallisation einstufig durchgeführt wird.4. The method according to any one of claims 1 to 3, characterized in that the crystallization is carried out in one stage.
5. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß die5. The method according to any one of claims 1 to 4, characterized in that the
Resuspendierungs-Mutterlauge mit einer solchen Temperatur in das Resuspendierungs-Gefäß eingeleitet wird, daß die resultierende Suspension untersättigt ist.Resuspending mother liquor is introduced into the resuspending vessel at a temperature such that the resulting suspension is undersaturated.
6. Verfahren nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß als6. The method according to any one of claims 1 to 5, characterized in that as
Ausgangsverbindungsgemisch eine Isocyanatisomerenmischung eingesetzt wird. An isocyanate isomer mixture is used as the starting compound mixture.
EP97952810A 1996-12-10 1997-11-27 Suspension crystallization method Withdrawn EP0944588A1 (en)

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US3217024A (en) * 1963-03-22 1965-11-09 Allied Chem Conversion of mixtures of 2, 4-and 2, 6-toluene diisocyanates to other mixtures of different isomer ratio
US3777892A (en) * 1971-01-27 1973-12-11 H Thijssen Apparatus for the separation and treatment of solid particles from a liquid suspension
US3872009A (en) * 1971-06-25 1975-03-18 Henricus Alexis Corne Thijssen Apparatus for the separation and treatment of solid particles from a liquid suspension
DE3220439A1 (en) * 1982-05-29 1983-12-01 Bayer Ag, 5090 Leverkusen METHOD FOR SEPARATING TECHNOLOGALLY PURE 2,4-DIISOCYANATOTOLUOL OR OF AN INCREASED LEVEL OF 2,4-DIISOCYANATOTOLUOL ISOMERIC MIXTURES FROM, ESSENTIALLY consisting of 2,4- and 2,6-DIISOCYANATOTOLUENE ISING
US4557741A (en) * 1984-02-13 1985-12-10 Grasso's Koniklyke Machine Fabriekon N.V. Gradient column freeze concentration system
NL8603314A (en) * 1986-12-29 1988-07-18 Grasso Koninkl Maschf METHOD AND APPARATUS FOR RECOVERING A PURE SUBSTANCE FROM A LIQUID MIXTURE BY CRYSTALLIZATION
US4787985A (en) * 1987-08-25 1988-11-29 Grenco Process Technology B.V. Multi-stage purification unit process
DE4425316A1 (en) * 1994-07-18 1996-01-25 Bayer Ag Method for cleaning water by freeze crystallisation

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* Cited by examiner, † Cited by third party
Title
See references of WO9825889A1 *

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