METHOD FOR OPERATING A CONTINUOUS SEPARATION OF TARGET PRODUCT X IN THE FORM OF A FINALLY DIVIDED CR

专利摘要:
The invention relates to a process for the continuous separation of a target product X in the form of a finely divided crystallizate from a liquid phase containing the target product X and components other than the target X by crystallization of a suspension. cooling in an indirect heat exchanger, in which the crystallizate slurry formed is supplied from the heat exchanger first to a mixed buffer tank and, from this, to a device for separating the crystallize slurry and in the liquid phase, and in which, by external measures, the supersaturation of the suspension of crystallize with target product X supplied to the buffer tank is suppressed.
公开号:BE1018574A3
申请号:E2008/0502
申请日:2008-09-11
公开日:2011-04-05
发明作者:Juerg Heilek；Ulrich Hammon；Klaus Joachim Mueller-Engel；Volker Schliephake；Dieter Baumann
申请人:Basf Se；
IPC主号:

专利说明:

A method of operating a continuous separation of a target product X in the form of a finely divided crystallizate
Description
The present invention relates to a process for the continuous separation of a target product X in the form of a finely divided crystallizate of the target product X from a liquid phase P consisting of the target product X as well as different components B, of the target product X, a phase whose total molar fraction of components Bj has the value MBiP9es, comprising the operation of an indirect heat exchanger having a secondary space and at least one primary space, in which the secondary space and the minus one primary space are spatially separated from each other by at least one material separating wall which serves as a surface for the transfer of heat from the secondary space into the at least one primary space, by introducing a liquid phase stream P in the secondary space of the heat exchanger, while the at least one primary space is traversed simultaneously by at least one fluid refrigerant so that it forms in the secondary space, while leaving a liquid residual phase R remaining from the liquid phase P, a finely divided crystallizate of the target product X, which is suspended in the remaining liquid residual phase R, and which contains, in comparison with the liquid phase P, the different components of the target product X with a total molecular fraction MB, R9s> MB, p9es and whose target product content X reaches at least 70% by weight, while retaining a suspension S, having a degree of crystallization Y, of finely divided crystallizate of the target product X in the residual liquid phase R, and removing from the secondary space of the heat exchanger continuously the suspension S at the temperature Tsaus, and further comprising conveying the suspension S removed at Tsaus temperature into a mixed buffer vessel as well as using a pump from the buffer vessel, the feed a separating device is introduced by the suspension contained in the finely divided crystalline buffer container of the target product X and the separation of the slurry conveyed to the crystallization separation device contained therein and in the liquid phase which is also contained therein.
Continuous crystallization separation methods for a target product X from a liquid phase P containing the target product X as well as different components of the target product X by suspension crystallization by cooling with a heat exchanger of heat having a secondary space and at least one primary space (cooler or crystallizer) are also known (see, for example, DE-A 103 32 758, WO 2004/035514, Research Disclosure Database Number 496005 and 479008 as well as German application with the file number 2007 004 960.0) as processes which are generally connected to this process for separating the crystallizate suspension S formed first in crystallizate and in liquid phase. Such separation may, for example, be by filtration, sieve centrifugation and / or wash columns, as disclosed, for example, in WO 01/77056 as well as in the state of the art which is quoted. Normally, a aforementioned separation also involves washing the separated crystallizate to remove the liquid phase that adheres to the surface of the crystals. Such washing may, for example, be by melting the previously separated crystallized and washed.
By heat transfer from the liquid phase P conveyed to the secondary space and containing the target product X through the material separating wall (heat transfer surface) separating the secondary space and the at least one primary space, one of the other in the coolant flowing in the at least one primary space, the liquid phase P cools until the saturation limit of the liquid phase P with the target product X is exceeded and the phase liquid P is opposed to supersaturation by crystallization of the target product X.
The term "degree of crystallization" of a crystallizate slurry having a finely divided crystallizate suspended in a liquid phase means in this application the mass fraction of the finely divided crystallizate contained in the crystallizate suspension over the total mass of the slurry. of crystallizate.
The degree of crystallization Y of the suspension S is therefore calculated as a fraction of the crystallizate mass ιτικγ, υ contained in the suspension S for the degree of crystallization Y by the total mass ms of the suspension S:
The degree of crystallization Y of the suspension S is thus necessarily between 0 and 1. The value "0" corresponds to an exclusively liquid phase and the value T to an exclusively solid phase (that is to say that in both cases, there is no suspension).
When a component Bj of a liquid phase F (for example, in the liquid phase P or in the residual liquid phase R) is contained in molar quantity n, (the molar quantity nj is calculated in this case from the mass, in which the component Bj of the liquid phase F is contained, divided by the molar mass of the component Bj) and that the target product X in the liquid phase F is contained in molar quantity nx (the molar quantity nx is calculated in l from the mass, in which the target product X is contained in the liquid phase P, divided by the molar mass of the target product X), the molar fraction M'b.f of the component Bi contained in the phase F the quotient of the number of moles nj divided by the sum formed of the number of moles nx and respective numbers of moles of all components Bj different from the target product X contained in the liquid phase F, that is to say:
provided that the liquid phase F contains, in addition to the target product X, in total I components B, different from the target product X and different from each other.
If the liquid phase F is the residual phase R or the liquid phase P, the corresponding "F" must be replaced in M'b.f by "P" or "R".
By total mole fraction Mb9®s of the components Bj different from the target product X and contained in the liquid phase F (for example, in the liquid phase P or in the liquid phase R), is meant in this application the sum of all the individual values M'b.f, calculated for respective components B ,.
Correspondingly, the molar fraction Mx, in which the target product X is contained in the liquid phase F, is defined as follows:
We can write MX F + MB, F9es = 1 ·
If the liquid phase F is the residual liquid phase R or the liquid phase P, the corresponding "F" must be replaced in Mx by "P" or "R".
A crystallization separation of a target product from a liquid phase containing the target product X as well as different components of the target product X is applied in particular to separate the target product X from secondary products formed in the course of its manufacture. . In this case, the production of the target product X can already be done directly by chemical reaction in the liquid phase. But it goes without saying that the production of the target product X can also be done, for example, in the gaseous phase from which the target product X is then converted into the liquid phase as a rule by condensation measurements and / or absorption, normally together with secondary components accompanying the target product X in the gas phase.
The crystallization separation of the target product X can now in principle be carried out directly by a "precise" thermal separation process from the liquid phase produced as described in the context of the production of the target product X and containing the target product X and secondary components.
But, frequently, the aforesaid liquid phase is subjected, prior to the application of crystallization separation of the target product X, firstly at least to an "imprecise" thermal separation process in order to separate a partial quantity the aforementioned secondary components of the target product X.
In this regard, an imprecise separation process is defined as a separation process in which, thermodynamically, the composition of the phase containing the enriched target product X which is formed during the application of the separation process depends mainly on thermodynamically necessary way of the composition of the mixture to be subjected to the separation process (refer for example to the Mc-Cabe-Thiele diagram). For example, simple distillation, rectification, absorption, fractional condensation, desorption, extraction, stripping, azeotropic rectification, etc., belong to the imprecise thermal separation process.
In contrast, the separation by crystallization is all the more a precise thermal separation process that the composition of the crystals that are formed is, thermodynamically, very largely independent of the composition of the initial liquid mixture (also refer to the documents DE -A 2005 009 890 and DE-A 103 00 816).
The advantage of imprecise separation methods is generally based on the fact that they can be exploited with higher space-time yields. However, the disadvantage of imprecise separation methods is that the separation effect which they make it possible to obtain is relatively limited.
The disadvantage of the precise separation methods lies in their normally relatively small space-time yields, whereas in the normal case there is a very high separation effect.
Given the aforementioned background, the two principles of separation are therefore often also applied in combination as follows.
On the product mixture obtained in the context of the production of the target product X, first of all at least one imprecise thermal separation process is applied and a liquid phase P which contains the target product X is produced here. already enriched in comparison with its weight fraction in the product mixture. This liquid phase P, which still contains, in addition to the target product X, secondary constituents different from the target product X, is then subjected to a separation by crystallization of the target product X and the residual liquid phase R (which is also frequently referred to as laundry. mother), which contains the secondary components in the relatively enriched state, is returned at least partly in at least one imprecise thermal separation process previously applied. In this way, the advantages of the two principles of separation can be implemented simultaneously.
In many cases, a liquid phase P having a target product X and crystallization separating the target product X therefore contains (and this also concerns the liquid phases P concerned in the present application) and at least two, often at at least three or four, frequently at least five or six and very often at least seven or eight, possibly at least nine or ten different secondary components of the target product X (these secondary components are contained then, within the meaning of the present application, in the P liquid phase if they are detectable as components of this phase, for example, by gas chromatography, by liquid chromatographic method or otherwise (eg, as water by Karl Fischer titration).
In addition to the characteristic secondary products conditioned by the manufacture of the target product X, the liquid phase P containing the target product X may also contain solvents or a mixture of solvents and / or, in the context of the separation of the target product X a mixture of reaction products, auxiliary agents used in the production of the liquid phase P (for example, absorption agents, extraction agents, etc.). In fact, the residual liquid phase R can be, for example, as much a melt of the target product X and impurities as solutions of the target product X and solvents (or solvent mixtures) and, as a rule, impurities.
The buffer container used in a method described as in the preamble of this document is primarily intended to increase flexibility in the manufacture of the target product X.
If, for example, the separation of the target product X in the indirect heat exchanger is not due to a disturbance for a limited period, the production of the target product X can still be continued continuously if the buffer container contains to some extent a supply quantity of crystalline suspension of the target product X.
Frequently, several suspension crystallizers and several separation devices are operated in parallel in the same way. If, for example, one of the separation devices operated in parallel does not operate due to a disturbance for a limited period, all suspension crystallizers may still continue to operate if the capacity, for example, of a Common buffer vessel is such that it can increase the production flow of a suspension crystallizer for a limited period of time without having to transfer it to a separation device.
If the number of suspension crystallizers operated in parallel is greater than the number of separation devices installed downstream and also operated in parallel, it is natural to combine the crystallizate suspensions extracted from the suspension crystallizers first in a buffer container and then distribute them, from the buffer vessel, on the separation devices operated in parallel.
Furthermore, in the case of parallel-operated suspension crystallizers, the quality fluctuations in the individual suspension crystallizer can be captured to a certain extent so that crystalline suspensions produced in the individual suspension crystallizers are conveyed. to a common buffer vessel, in which they are mixed with one another and from which a suspension of crystallizate is then removed for separation purposes.
However, it has proved disadvantageous in terms of the concept of the intermediate buffer that the (crystallizate) suspension S withdrawn continuously from the secondary space of the heat exchanger is not normally completely at thermodynamic equilibrium, but present to a limited extent, supersaturation to the target product X.
If supersaturated suspension S (of crystallizate) supernatant in target product X is conveyed in this manner and has the Tsaus temperature in the normally thermally insulated buffer vessel with respect to its environment, the supersaturation in the buffer vessel decreases by continuing formation. of crystallizate.
However, it is disadvantageous for the formation of crystallization in the buffer vessel that it occurs in an uncontrolled manner unlike the crystallization of the suspension in the cooled heat exchanger indirectly arranged for this purpose.
This can lead, for example, that, on the inner wall of the buffer vessel or, in the case where the contents of the buffer vessel are mixed by an agitator, on the agitator itself grow larger crystallized agglomerates, which are detached in increasing quantity and, for example, can disturb the trouble-free operation of transporting the crystallizate suspension in the buffer vessel in the separation device by means of the corresponding transport pump or can even completely interrupt it in adverse cases.
The object of the present invention is therefore to overcome at least partially or completely the aforementioned problems.
This object is achieved by a process for continuously separating a target product X in the form of a finely divided crystallizate of the target product X from a liquid phase P consisting of the target product X as well as components Bj different from target product X, the phase of which the total molar fraction of components Bj has the MB.p9es value, comprising the exploitation of an indirect heat exchanger having a secondary space and at least one primary space, in which the secondary space and the at least one primary space is spatially separated from each other by at least one material separating wall, which serves as a heat transfer surface of the secondary space in the at least one primary space, by introducing a phase current P liquid in the secondary space of the heat exchanger, while the at least one primary space is traversed simultaneously by at least one fluid refrigerant so that it forms in the secondary space, while leaving a liquid residual phase R coming from the liquid phase P, a finely divided crystallizate of the target product X, which is suspended in the remaining liquid residual phase R, and which contains, in comparison of the liquid phase P, the different components of the target product X with a total molar ratio MB, R9s> MB, p9es and whose target product content X reaches at least 70% by weight, while maintaining a suspension S, exhibiting a degree of crystallization Y, finely divided crystallizate of the target product X in the liquid residual phase R, and is removed from the secondary space of the heat exchanger continuously S suspension at Tsaus temperature and, furthermore, comprising transporting the suspension S withdrawn (from the secondary space) to the Tsaus temperature in a mixed buffer vessel, as well as using a pump, from the buffer vessel, the al imentation of a separation device by the suspension contained in the finely divided crystalline buffer container of the target product X and the separation of the slurry conveyed to the crystallization separation device contained therein and in the liquid phase contained therein, characterized in that, in the path of the secondary space in the buffer container, in the buffer container itself and / or in one or more pump lines leading out of the buffer vessel and again into it (these lines of pumping may also be such as to maintain, for example, the pumps in operation, which feed the crystallization suspension separation device from the buffer vessel when the separation device fails for a short time; in this way, it is against deposition of the crystallizer in the pump), the temperature of the suspension S conveyed to the buffer vessel is increased with the aid of an external source of energy at a value TPu at above Tsaus and / or the total molar fraction of the different components of the target product X is contained in the residual liquid phase R of the suspension S conveyed to the buffer vessel by external addition (from the outside into the crystallizate suspension S) of different components of the target product X at a MBiPu9es value above MB, R9es.
As a general rule, TPu-Tsaus can be written> 0.1 K. However, in order not to counteract the crystallization of the suspension carried out in the indirect heat exchanger, the difference TPu-Tsaus will normally reach a value less than or equal to 3 K, preferably less than or equal to 2 K and, as a rule, less than or equal to 1 K. Frequently, the difference TPu-Tsaus will also reach a value less than or equal to 0.7 K or less than or equal to 0.5 K.
Correspondingly, the increase of Mb, r9®s to MβPu9es (with Mβ, Rges as a base) will normally reach plus or minus 0.1%. However, in order not to thwart the crystallization of the suspension previously carried out in the indirect heat exchanger, the aforementioned increase is generally a value less than or equal to 5%, usually less than or equal to 3% and most of the time less than or equal to 1%.
It goes without saying that in the process according to the invention, the increase of Tsaus to TPu and the increase of MB, R9es to MB, Pu9es can also be applied in combination. But, according to the invention, preferably, the suppression of the supersaturation contained in the suspension S is achieved by only increase Tsaus TPu.
In this case, the temperature increase mentioned above can be done by direct and / or indirect supply of energy (for example heat).
The "external" concept means here that the heat of crystallization released by suppressing the supersaturation by continuing the crystallization of the target product X must be excluded as a source of energy or heat.
A direct supply of energy, for example, heat is, for example, possible by dosing the added substances in the buffer vessel and / or in the pipe leading to the buffer vessel, whose temperature is above Tsaus.
As such substance, there may be mentioned, for example, a target product X heated correspondingly per se, preferably a target product X which has been recovered previously in the context of a separation according to the invention. Alternatively, mixtures containing the target product X heated for this purpose may be considered, the liquid phase P and the residual liquid phase R being preferably composed of these mixtures. But, in principle, acidic water will also be used for this mixture (see, for example, WO 2004/035514, EP-A-1,818,324, DE-A 10243625, DE-A10323758 and DE-A 10 2007 004960).
But it goes without saying that, for the purpose of a direct supply of heat, it is also possible to dose correspondingly heated substances which, by their nature, correspond to an individual component B, or to a mixture of several components B ,, which are also contained in the liquid phase P because of their manufacture. But, in principle, for direct heating, it is also possible to take into account correspondingly heated substances, which by their nature do not form any component of the liquid phase P because of their manufacture. For direct heating, it is advantageous (as has already been said), for example, to use a liquid residual phase R correspondingly heated and previously separated from the suspension. In a direct heat supply, which is not done as a supply of target product X heated correspondingly, the essential thing is that one simultaneously obtains an increase of MBtR9es automatically with this contribution.
According to the invention, it is therefore advantageous for the purposes of direct heating to preferably use substances whose molecular weight is smaller than three times, more preferably smaller than twice, and preferably smaller than once the molecular weight of the target product X (eg water).
Preferably, the substances dosed for direct heating purposes dissolve in the residual liquid phase R.
As already mentioned, the liquid phase obtained during the separation of the crystallizate suspension extracted from the crystallization buffer container of the target product X contained therein and in the liquid phase contained therein for the purpose of increasing the yield of the target product X is preferably recycled in the method of manufacturing the liquid phase P. Preferably, this recycling is done in an imprecise separation process frequently used in the context of the manufacture of the liquid phase P (see, for example, FIG. Of WO 01/77056). It is therefore recommended as a direct heat source to be used according to the invention to measure substances, which can be separated, in the context of the aforementioned imprecise process, in a relatively simple manner from the target product X, or substances which, in the context of of the crystallization separation according to the invention of the target product X, a depletion coefficient AB | high, (at least greater than or equal to 5, preferably greater than or equal to 10, more preferably greater than or equal to 15). By depletion coefficient AB1 is meant the concentration ratio of the concentration of the component Bj remaining, during the crystallization separation according to the invention of the target product X of the liquid phase P which contains it, in the mother liquor ( in the liquid residual phase R) at the concentration of the component Bj remaining in the crystallizate (respectively expressed as a percentage by weight relative to the total amount of the remaining mother liquor (or residual liquid phase R) or the total amount of crystallizate formed) .
A separation between the crystallizate and the mother liquor of more than 90% by weight, preferably greater than 95% by weight or even 97, 98 or 99% by weight of the total amount of mother liquor is sufficient in the rule general to determine the coefficient AB | (the influence of the residual moisture on the crystallizate is generally insignificant). Preferably, the aforementioned values for the coefficient AB | Referring to the combination applied in the process according to the invention of crystallization of the suspension followed by the separation of the suspension S thus formed.
But a direct supply of energy or heat is also possible, for example, provided that it is in the buffer vessel, in the supply line leading to the buffer vessel or in a pumping line, a resistance heating for example, by which heating of heat can be applied directly to the desired extent in the crystallizer slurry fed to the buffer vessel and / or in the buffer vessel. However, it is also possible to provide a direct supply of energy by introducing hot gas or by exposure to electromagnetic radiation (for example, microwave radiation or infrared radiation).
According to the invention, the supply of energy or heat is preferably indirectly. For example, for this purpose, an externally heated pipe (or an externally heated pumping line) may be used to transport the crystallizate slurry into the buffer vessel.
But, in a very particular way, the accompanying heating will be carried out by equipping the buffer vessel with a double wall (alternatively, it may also be applied to the wall of the buffer vessel of the tubular or tubular coils carrying a fluid correspondingly (for example, welded or laid), within which is conveyed a fluid heat transfer agent, which has at least the desired target temperature for the contents of the buffer vessel.In principle, it is often sufficient that the bottom of the buffer container has a double wall or is equipped with mid-tubular or tubular coils.
The buffer vessel or buffer tank is conveniently equipped according to the application technique of a stirrer (preferably a propeller stirrer or other suspension stirrer), which mixes the crystallizate slurry in the buffer vessel. Alternatively, an inert gas can also be guided (bubbled) through the crystallizer slurry for mixing purposes (and also simultaneously for the purpose of supplying energy).
But it goes without saying that the mixing can also be carried out according to the mixing variants described in the documents DE-A 10 2006 045 088 and DE-A 10 2006 045 089. Similarly, the mixing can be done by means of decanting. As fluid heat transfer agent, for the aforementioned indirect accompanying heating, it is possible in principle to use the same materials as are recommended herein as a fluid refrigerant for the suspension crystallizer.
With regard to the increase of Mβ, R9es to MB, pu9es. In principle, it is also possible to dose the components B, different from the target product X, which have a temperature less than or equal to Tsaus. Moreover, this has already been expressed in relation to the direct supply of heat to pass from Tsaus to TPu.
The preferred building material for the buffer tank is the stainless steel because of its favorable thermal conductivity. The preferred fine steels are those of material numbers DIN 1.4541 and 1.4571. The thickness of the wall typically reaches 3 to 30 mm.
The removal of the (crystallizate) suspension S from the secondary space is advantageously done by overflow adjustment with the aid of an overflow weir adjustable in height. But it can also be done by level adjustment through a submerged tube.
The suspension crystallizer as well as the buffer tank and the separating device are normally operated both by thermal insulation and by water vapor sealing by heat-insulating materials (eg Stiropor®) applied to their sheathing and by barriers to water vapor glued over it (for example, an alubutyl sheet from the company Wego SystemBaustoffe, subsidiary VTI at D-67014 Ludwigschaffen / Rhein).
As a pump for supplying the separation device with a crystallizate suspension extracted from the buffer tank, it is possible in principle to mention transport pumps of all types. It is advantageous according to the invention to use radial centrifugal pumps. Among these are advantageous those recommended in DE-A 103 53 014. Among these are particularly favorable centrifugal pumps Kanalrad type. Quantitative control is normally done by adjusting the number of revolutions of the pumps.
The direct displacement of the fluid phase in the secondary space of the indirect heat exchanger (of the suspension crystallizer) through this exchanger is in many cases already sufficient to condition a suspension of the crystallization of the target product X separated in the secondary space.
But, as a rule, the secondary space also has one or more mixing devices. This can be in the simplest case a bubbling with an auxiliary gas (for example air), one or more agitators, a scraping device to release the separating wall between the secondary space and the primary space of the crystallizer and / or a transfer device. The mass flow conveyed to the secondary space through it is normally set so that the liquid phase P is forced into the secondary space by means of pumps.
To achieve the process according to the invention, all types of indirect heat exchangers can be mentioned in principle (they have, by their definition, the primary space / secondary space structure required according to the invention) (see, for example, Kristallization, Grundlage und Technik, Günther Metz, Springer-Verlag, Berlin 1969, pp. 214 et seq., and the Ullmanns Encyclopedia of Technische Chemie, Verfahrenstechnik I, Verlag Chemie Weinheim, 4th Edition, 1972, pages 672 -682, as well as in the state of the art mentioned in these standard works).
According to the invention, it is preferred to use as an indirect heat exchanger an exchanger in which the side, turned towards the secondary space, of the at least one dividing wall separating the at least one primary space from the secondary space, respectively, is operated undergoing scraping (continuous scraping of the relevant heat exchange surface with appropriate scraping devices). These indirect heat exchangers (crystallizers, coolers) are frequently also referred to as doctor heaters. The at least one primary space can be installed in the indirect heat exchanger both stationary and movably (eg with removable cooling disks). In the latter case, the moving elements of the primary space can be replaced from time to time.
As examples of choice, it is possible to use as suspension crystallizers for the process according to the invention: - rotary tube crystallizers (the secondary space is the internal space of the tube, the sheathing of the tube is a double jacket, in which the refrigerating agent is conveyed inside the tube in the same direction or in countercurrent relative to the mass flow, preferably the inside of the tube is slightly inclined with respect to the horizontal, on the wall of the In the interior of the tube crystalline deposits may be formed which can be released continuously (for example with chains) and / or scraped (for example with radial scrapers) and the liquid phase P is conveyed. continuously at the first end of the tube, the suspension S is discharged continuously to the other end of the tube); a container with suspended cooling elements (in a non-stirred container are suspended cooling elements (for example, cooling trays), the liquid phase P is, for example, conveyed below and to the left in the container and is discharged from the container by overflow adjustment to the right and above the suspension S, possibly the cooling elements having deposits are replaced by new cooling elements); - stirring vessels (ie, for example, containers, which are surrounded by a cooling jacket and / or equipped with cooling elements (cooling tubes, cooling plates); they have a stirring mechanism which continuously mixes the contents of the internal space which is not occupied by the cooling elements, the liquid phase P is pumped and the suspension S is discharged by overflow ); a votator (agitator tube cooled by a jacket, the wall of which is scraped by scraper blades pressed by springs, the liquid phase P is pumped at one end, while the suspension S flows outwards at the end; other end); - Disk crystallizers (trough-shaped containers with a horizontally arranged shaft, on which are mounted, at regular intervals, hollow discs, which are traversed by the refrigerant as a rule against the current with the liquid phase to crystallize P and have sector-shaped sections for the passage of the liquid phase P or of the crystallizate suspension, gentle stirring of the crystallizer suspension through the disks and the refrigerant lines which connect them, the liquid phase P is introduced on the first side by pumping into the disk crystallizer and discharged from the disk crystallizer on the opposite side by adjustment of the overflow); forced circulation crystallizers from Swanson or Messo Chemietechnik.
Crystallizers particularly suitable for the process according to the invention (in particular, in the case of acrylic acid, methacrylic acid, p-xylene or N-vinylpyrrolidone as target product X) are disk crystallizers. Cooling (cooling disks in secondary space contain primary spaces), for example those described in Research Disclosure Database Number 496005 (published August 2005) and Research Disclosure Database Number 479008 (published March 2004 ).
As the fluid coolant (or auxiliary agent), both gases and liquids can be used.
It is preferred according to the invention to use liquid refrigerants (or heating agents). Liquid coolants (or heating agents) that may be mentioned include, for example, heat-transfer oils, water, salt solutions in water, mono- or multivalent organic alcohols, such as methanol, sodium hydroxide and the like. ethanol, propanol, glycol and / or glycerol, but also mixtures of one or more of the aforementioned refrigerants, for example mixtures of water and methanol or mixtures of water and glycol (for example with 10 to 60% by weight of glycol).
The temperature T "em (temperature at which the fluid coolant is conveyed to the at least one primary space) is typically set to a value of 0 to 20 K, frequently 1 to 15 K and most of the time 2 at 10 K below Tsaus (temperature at which the suspension S is removed from the secondary space). The temperature TKein is necessarily below the temperature at which the liquid phase P is conveyed simultaneously to the secondary space of the heat exchanger.
But, in many cases, there remain surface elements of the separating wall that can not be scraped or only with difficulty. This is, for example, the case where the primary space is the internal space of a circular cooling disk, which is, for example, in a simple manner, immersed in the liquid phase flowing in space secondary. While the front and rear sides of the cooling disc are relatively easily accessible for scraping, this is not normally the case on the surface of the cooling disc jacket. These surface elements are therefore generally subject to an accompanying heating, which must remove these crystalline deposits. Such an accompanying heater may, for example, be a resistive companion heater. It goes without saying that such accompanying heating can however be achieved by indirect heat exchange (for example, by passing a hollow profile formed with a fluid heating agent).
The crystals of the suspension crystallizer formed in carrying out the process according to the invention typically have a longitudinal extension (the longest direct straight line of two points lying on the surface of the crystals) in the zone of 1 at 10,000 μm, frequently from 10 to 1,000 μm, more frequently from 100 to 800 μm and very often from 300 to 600 μm.
Moreover, the separation by crystallization can be carried out just like the suspension crystallizations carried out in the state of the art.
The increase of Ts.sub.2 to TP.sub.u and / or of Me.sub.B to M.sub.B.sub.e.sup.es is generally only performed in the context of the present invention when this is necessary to reduce the supersaturation in the suspension S. Otherwise, the effect of the crystallization of the suspension would be counteracted to a certain extent.
The process according to the invention is also suitable when the content of the liquid residual phase R (mother liquor) containing the suspension S taken from the secondary space as the target product X is greater than 70% by weight. But it is also suitable when the above-mentioned target product content X in the liquid residual phase R has a value of 80% by weight or 85% by weight or 87% by weight or> 90% by weight or 92% by weight. or> 94% by weight or> 95% by weight or> 96% by weight or> 97% by weight or> 98% by weight or 99% by weight.
In fact, the process according to the invention is suitable in the case of such liquid phases whose target product content X has a value> 70% by weight or 75% by weight or 80% by weight or 85% by weight. or> 87% by weight or 90% by weight or 92% by weight or 94% by weight or> 95% by weight or> 96% by weight or> 98% by weight or> 99% by weight. As a general rule, the aforementioned content of the liquid phase P conveyed in the process according to the invention to the secondary space of the heat exchanger in target product X however reaches a value of less than or equal to 99.995% by weight, more preferably less than or equal to 99.99% by weight.
As the target product X, there will be mentioned for the suspension crystallization carried out according to the invention as cooling crystallization, for example, saturated or unsaturated carboxylic acids, such as acetic acid, propionic acid, acrylic acid and methacrylic acid, or substituted aromatics (for example with halogen, methyl, carboxyl, hydroxyl and / or nitrogen (e.g., -NH2) as substituents), especially p-xylene, cresol and chlorobenzene, or multi-ring aromatic compounds, such as naphthalene and phenol A, or isocyanates, such as TDI and MDI, or vinyl compounds, such as N-vinylpyrrolidone, or formaldehyde oligomers, such as trioxane; or inorganic salts, such as Na or K salts (eg, sulfates, chlorides, bromides and iodides).
The process according to the invention is particularly suitable in the case of acrylic acid, methacrylic acid, p-xylene or N-vinylpyrrolidone as target product X.
If acrylic acid is the target product X, water, diacrylic acid (Michael adduct), methacrylic acid, benzoic acid, acetic acid and the like are formed, for example. propionic acid, which are substances suitable for the invention for increasing by external addition MB, R9 to MB, may be advantageous according to the invention, in the case of acrylic acid as the target product X as part of the abovementioned increase in MB, Rges to MB, Puges, to also use so-called acidic water, as is normally produced in the context of an acid separation Acrylic mixture of gaseous products of a heterogeneously catalyzed partial gas phase oxidation of a C3 precursor compound of acrylic acid (eg propane, propylene, acrolein, propionic acid, propanol , glycerin and / or propionaldehyde) (refer, for example, to document WO 2004/035514, German Application No. 10 2007 004 960.0, DE-A 10243625 and DE-A 10323758). In general, the acidic water contains at least 60% by weight (frequently less than 70% by weight, most of the time less than 75% by weight, often less than 80% by weight) of water and at least 3% by weight. % by weight (frequently at least 5% by weight, more frequently at least 7% by weight, quite frequently at least 9% by weight or at least 11% by weight) of acrylic acid.
If the methacrylic acid is the target product X, water, acrylic acid and acetic acid are formed which are substances suitable for the present invention to increase by MB external addition. Rges to MB, Puges.
If p-xylene is the target product X, for example, water is formed as well as n- and o-xylenes which are substances suitable for the invention to increase by MB external addition, to MBiPuges.
If N-vinylpyrrolidone (also 1-vinyl-2-pyrrolidone) is the target product X, water and 2-pyrrolidone, which are substances suitable for the invention to increase by addition, are formed, for example. external MB, Rges to MB, Pu9es.
The process according to the invention is particularly suitable in the case of acrylic acid as target product X and a crude acrylic acid as the liquid phase, which has one of the following salts in the following contents:> 70% by weight Acrylic acid,
Up to 15% by weight acetic acid,
Up to 5% by weight propionic acid,
Up to 5% by weight Aldehydes of low molecular weight,
Up to 3% by weight polymerization inhibitors, 0 to 5% by weight Diacrylic acid (Michael's adduct), and
Up to 25% by weight; or> 80% by weight Acrylic acid,> 100 ppm by weight to <15% Acetic acid, weight> 10 ppm by weight to <5% propionic acid, weight
Up to 5% by weight Aldehydes of low molecular weight,
Up to 3% by weight polymerization inhibitors, and 0 to 5% by weight acrylic acid (adduct of
Michael), and
Up to 15% by weight; or 85% by weight Acrylic acid,> 100 ppm by weight to <10% Acetic acid, by weight> 10 ppm by weight to <5% Propionic acid, weight
Up to 5% by weight Aldehydes of low molecular weight,
Up to 3% by weight polymerization inhibitors, 0 to 5% by weight Acrylic acid (Michael's adduct), and
Up to 10% by weight; or> 90% by weight Acrylic acid,> 100 ppm by weight to <5% Acetic acid, weight> 10 ppm by weight to <2% Propionic acid, weight
Up to 2% by weight Aldehydes of low molecular weight,
Up to 2% by weight polymerization inhibitors, 0 to 3% by weight Acrylic acid (Michael's adduct), and
Up to 9% by weight; or> 95% by weight Acrylic acid,> 100 ppm by weight to <3% Acetic acid, weight> 10 ppm by weight to <2% Propionic acid, weight
Up to 2% by weight Aldehydes of low molecular weight,
Up to 2% by weight polymerization inhibitors, 0 to 2% by weight acrylic acid (adduct of
Michael), and
Up to 4.9% by weight; or 93 to 98% by weight Acrylic acid, 1 to 5% by weight Water, 0.001 to 3% by weight Acrolein,> 0 to 3% by weight Methacrolein, 0 to 3% by weight Methacrylic acid, 0.1 to 3 % by weight Acetic acid, 0.01 to 3% by weight Propionic acid, 0.001 to 3% by weight Formaldehyde, 0.001 to 3% by weight Aldehydes other than formaldehyde, 0.01 to 3% by weight Maleic acid, and> 0 at 3% by weight Protoanemonin.
Crude acrylic acids are obtained, for example, according to the methods known from the state of the art (see, for example, EP-A 1,818,324, WO 01/77056, DE-A 103 32 758, DE -A 102 43 625, to the German application for file number 10 2006 057 631.4, to the German application for file number 10 2006 062 258.8, to the German application for file number 10 2007 004 960.0, to document WO 2004 / 035514, to the German application of file number 10 2006 049 939.5, to the documents DE-A 10 2005 029 629, WO 03/041832 and DE-A 10 2005 015 639 as well as to the state of the art cited in these documents).
In this case, it is generally a question of raw acrylic acids, which have been obtained from the mixture of gaseous products by partial oxidation, with heterogeneous catalysis, of at least one C3 precursor compound of the acid. acrylic (for example, propane, propylene, glycerol, acrolein, propionic acid, propanol and / or propionaldehyde) (return to these).
In this case, for the process according to the invention for the production of the liquid phase P, mention may in particular be made of such crude acrylic acid, which has been produced from the gaseous product mixture by partial gas phase oxidation. heterogeneous catalysis of a C3 precursor compound using at least one imprecise separation method. This in particular when the liquid phase produced during the separation according to the invention is recycled at least partly in at least one of the imprecise separation processes applied at least partially in at least one of the imprecise separation methods. applied to the manufacture of crude acrylic acid from the gaseous product mixture of partial gas phase oxidation.
The basic structure of such a combined application of the imprecise separation method and the precise separation method for crystallization is taught, for example, in DE-A 196 06 877, EP-A 792 867 as well as in the documents EP-A 1 484 308, EP-A 1 116 709, EP-A 1 818 324 and in particular EP-A 1015 410.
In the simplest case, the crude acrylic acid to be used for obtaining the liquid phase P may be the absorbate and / or the condensate obtained partially and / or fractionally from an absorption separation and / or by condensing the acrylic acid of the gaseous product mixture with a heterogeneous catalytic partial gas phase oxidation of at least one C3 precursor produced in this document. Recycling of the liquid phase produced in the separation according to the invention is suitably carried out by absorption and / or condensation (see EP-A-1,818,324).
The acrylic acid contained as target product X in the liquid phase P is advantageously recycled to a mixture of gaseous products subjected to partial oxidation, which contains: 1 to 30% by volume of acrylic acid,> 0 to optionally 0.005 to 10 % by volume of propylene, 0 0 or 0.001 to 2% by volume of acrolein, 0 0 or 0.001 to 2% by volume of methacrolein, 0 0 or 0.001 to 2% by volume of methacrylic acid, 0 0 or 0.005 to 10% by volume of molecular oxygen, £ 0 or 0.005 to 3% by volume of acetic acid, 0 0 or 0.001 to 2% by volume of propionic acid, 0 0 or 0.001 to 2% by volume of formaldehyde, > 0 or 0.001 to 2% by volume of other aldehydes, and 10 to 98 or 50 to 98% by volume of dilution gas (inert).
The dilution gases may contain, for example:> 0 or 0.005 to 90% by volume of saturated hydrocarbons having 1 to 6 carbon atoms (in particular propane, methane and / or ethane),> 0 or 0.05 to 30 % by volume of water vapor, 0 0 or 0.05 to 15% by volume of carbon oxides (CO and / or CO2), and 0 0 or 1 to 90% by volume of molecular nitrogen.
In this case, the mixture of gaseous partial oxidation products can be reduced in particular to partial oxidation, as described in DE-A 10 2004 032 129 and their equivalent foreign protection rights, DE-A 102 45 585, WO 03/076370, WO 01/96271, EP-A 117 146, WO 03/011804, US-A 3,161,670, DE-A 33 13 573, DE-A 103 16 039 and WO 01/96270 from propylene and / or propane, and the propylene source optionally exhibits hydrogenation of propane and / or hydrogenation of propane oxide (optionally heterogeneously catalyzed) as a reaction stage arranged upstream.
In order to separate the crystallized suspension conveyed from the buffer container of the crystallization separation device contained therein and in the liquid phase contained therein, in the context of the process according to the invention, all the processes can be mentioned in a very general manner. detailed in WO 2006/111565, WO 01/77856, WO 02/055469 as well as WO 03/078378 (eg mechanical separation methods, such as centrifugation). In this case it is advantageously a washing column with a forced transport of the separated crystals (for example acrylic acid crystals). The volume fraction of crystallizate in the crystallizate bed in this case generally reaches values greater than 0.5. In general, the wash column is operated at values of 0.6 to 0.75. As washing liquid, the melt of crystals (for example, acrylic acid crystals) which have been previously purified (separated) in the washing column is advantageously used. The washing is normally done against the current.
In particular, the process according to the invention comprises processes in which the liquid phase P has values> 70% by weight or> 75% by weight or> 80% by weight or 85% by weight or> 90% by weight or> 95% by weight.
Furthermore, it is advantageous according to the invention for the water content of the acrylic acid as the liquid phase P containing the target product X, relative to the acrylic acid contained in the liquid phase P, to have values of 0, 2 or 0.4 to 8, or 10, or 20, or 30% by weight, or 0.60 to 5% by weight or 0.60 to 3% by weight.
It goes without saying that the process according to the invention can also be used on all the crude acrylic acids of the WO document
98/01414 as well as on all the crude p-xylenes of EP-A-097405 as liquid phase P.
As a general rule, the temperature of the (crystallizate) suspension S is, when it is removed from the secondary space (Tsaus), using crude acrylic acid as the liquid phase P containing the target product X in the process according to the invention in the range of -25 ° C to + 14 ° C, particularly in the range of -5 ° C to + 12 ° C and most preferably in the range of 4 or 6 to 9 ° C.
It goes without saying that all the steps of the process, in which acrylic acid is involved, are carried out by preventing any polymerization. In this case, one can proceed as described in the state of the art. A dominant position among all of the available process stabilizers operating on acrylic acid is dibenzo-1,4-thiazine (ppz), 4-hydroxy-2,2,6,6- tetramethyl-piperidine-1-oxyl (40H-TEMPO) and p-methoxyphenol (MEHQ), which can be respectively used individually, at a rate of two or a mixture of three of the components of the liquid phase P (e.g. crude acrylic acid). Usually, its total amount is 0.001 to 2% by weight relative to the acrylic acid contained in the liquid phase P.
Correspondingly and as detailed, for example, for acrylic acid, the process of the invention can also be integrated with the process of manufacturing other X target products.
In particular, the present invention therefore comprises processes, in which, starting from the buffer tank, a washing column used as separating device is supplied with a suspension of crystallizate contained in the buffer tank, in which process: a wash column wall, which includes a treatment space, - maintaining the crystallizate contained in the crystallizate suspension and forming a crystallizate bed in the treatment space from the crystallized suspension conveyed into the space process, a liquid phase is delivered from the treatment space, - the crystallizate bed is transported into the treatment space, - in the treatment space, at least one force different from the gravitation acts in the direction of transporting the crystallizate bed, which force carries the crystallizate bed into the treatment space, - in the treatment space, to control e-stream with the crystallizate bed, a pure melt consisting of crystallized melt and separated previously by this separation process of the washing column is fed so that in the crystallizate bed, a washing front is formed, which divides the crystallizate bed into a liquid phase zone and a pure melting zone, and at the opposite end to the delivery of the crystallization slurry of the washing column, the crystallizate which is continuously extracted is extracted continuously. is developed in the wash column in a solid and / or melted form.
What has been said above is especially valid when, in the process according to the invention, the target product X is acrylic acid. In general, in this case, after separation of the finely divided acrylic acid crystallizate, another process is carried out in which the separated acrylic acid crystallizate is melted and then subjected in itself to a polymerization (for example radical) or with other mono-ethylenically unsaturated compounds (eg, solution polymerization, emulsion polymerization, suspension polymerization, gas phase polymerization or bulk polymerization). Such a process can also be connected when the separation of the crystallizate suspension in crystallizate and in liquid phase is carried out in another way than with a washing column.
As a general rule, in the process according to the invention, the liquid phase mass current P conveyed to the secondary space of an indirect heat exchanger reaches 2 to 80 t / h. Corresponding to this are mass currents mx fed to the liquid phase P of a value of 1.4 to 79.8 t / h.
Depending on the respective separation problem (including the separation device used) as well as the type and size of crystals constituting the crystallizate, the degree of crystallization Y of the suspension S is frequently in the range of 0.10 to 0. , 50, with a greater frequency in the range of 0.20 to 0.40, and most preferably in the range of 0.25 to 0.35 or 0.30.
EXAMPLE AND COMPARATIVE EXAMPLE I. EXAMPLE
Two stirred and scraped cooling disc crystallizers of the type described in Research Disclosure Database Number 496005 (published August 2005) are operated in parallel. These are formed of a trough, in which 24 scraped circular cooling discs (cooling discs) are suspended one behind the other at an equidistant distance of 30 ± 1 cm. The diameter of the plates is 3.3 m. The thickness of the plates is 5.2 cm.
As the cooling agent, a mixture of 70% by weight of water and 30% by weight of glycol is used for each of the two crystallizers. The coolant is fed into the respective crystallizer countercurrently with the liquid phase P fed to the crystallizer therethrough and, in this case, further enriched by passing from a cooling disc to the next cooling disc. In fact, the refrigerant is fed into each of the two crystallizers, distributed in the form of two parallel streams of the same magnitude on the cooling plates of the respective crystallizer. Half of the current passes through the digitally aligned cooling plates, the other half flow passes through the numerically non-aligned cooling plates (the cooling disc counting in the coolant flow direction starting with 1) . The cooling surfaces are made of thin steel (material DIN 1.4541). The wall thickness of the stainless steel cooling surfaces is 4 mm. The number of revolutions of the scraping device is 5 to 6 rpm. The shaft driving the scraper and guided by the cooling discs is sealed by water-rinsed packing glands (Teflon packing cord, rinse quantity: a few liters of water per hour). up to 10 liters per hour per filling). On the periphery of each cooling disc, where there can be scraping, a hollow profile (a welded tube; (material: fine steel (DIN 1.4541 material), wall thickness = 3.6 mm) is applied. hollow profile of the individual cooling discs of a crystallizer is traversed in parallel for accompanying heating purposes by a liquid heat-transfer agent I, which consists of 70% by weight of water and 30% by weight of glycol.
The scraping devices are segmented in the radial direction (4 segments).
The specific compressive force of the scraper devices is in the mounted state perpendicular to the scraping surface at about 4 N per centimeter of active scribing edge length. As scraper material, Multilene®PE1000 is used. In addition to the scraping devices, the shaft drives pallets (between two cooling discs and in front of the first and last cooling discs, respectively in symmetrical arrangement), which ensures a reinforced mixture. In the rear part of the respective crystallizer in the conveying direction of the crystallizer slurry (behind the last cooling disc) flows the (crystallizate) suspension formed in the individual crystallizer S respectively via an overflow weir in a Buffer tank agitated by means of a helical stirrer (fine steel tank made of DIN material 1.4541, internal volume 20 m3, wall thickness 10 mm, internal diameter = 2.58 m, the bottom of the buffer vessel is made with welded half-tubular coils, through the space of the half-tubular coils, is conveyed as liquid coolant II a mixture of 70% by weight of water and 30% by weight of glycol; stationary suspension of crystallizate suspension buffer reaches 16 m3, from which two hydraulic melting columns of the same structure are fed in parallel by the suspension of crystallizate extracted from the buffer tank (after separation of the suspension mass flow S removed from the buffer tank S), the intensity of the withdrawal current corresponds to the intensity of the total supply stream from the crystallizers) on the two washing columns the flow through a Coriolis mass flowmeter is also carried out respectively before the entry into the respective washing column in order to determine the degree of crystallization Y via the mass density of the respective partial mass flow) in order to separate it in the liquid phase. and in crystallizate. The separation in the melt wash columns is as in the documents EP-A 1 272 453, EP-A 1 448 283, WO 03/041833, EP-A 1 305 097, DE-A 101 56 016, DE-A A 10 2005 018702, DE-A 102 23 058 and in the German application file number 10 2007 004 960.0. The internal diameter of the individual washing column is 1.4 m. The washing columns are fed with the crystallizate suspension by means of a centrifugal pump (Kanalrat type, company KSB), in which the quantitative control is carried out by adjusting the number of revolutions of the pumps. The liquid phase separated in the washing columns is recycled via another buffer tank as in FIG. Of WO 01/77056 or as described in German Application No. 10 2007 004 960.0 in the fractional condensation used for the production of acrylic acid as the liquid phase P containing the target product.
Both crystallizers have a stainless steel roof (DIN 1.4541 material) and are closed against any ambient air inlet. Both the washing columns, also made of stainless steel (material DIN 1.4541, wall thickness 10 mm), the crystallizers and the buffer tank are insulated and sealed against water vapor (see, for example, document DE- A 2007 032 633) because of the Styropor applied on their stainless steel shells and the alubutyl sheet glued on top and coming from the company WeGo System Baustofe, subsidiary VTI at 67014 Ludwigshafen / Rhein.
The washing columns, the buffer tank and the crystallizers are housed in a common enclosure. The temperature of the air in the common enclosure is between 25 ° C and 28 ° C. The material transport from the crystallizers to the buffer tank and from the latter in the washing column is also protected from the ambient air as well as under heat-insulating and waterproofing. The degree of crystallization Y is set at 0.28 for each of the two crystallizers operated in parallel autonomously. It is possible to oppose a deviation of adjustment in both cases by increasing or reducing the respective value of the temperature T e, n.
The operating conditions of two crystallizers are characterized by the following framework conditions.
Target product X = acrylic acid
The P-phase fed to the crystallizers is crude acrylic acid, which is converted to acrylic acid by fractional condensation of a mixture of gaseous products of a heterogeneous catalytic partial gas phase oxidation into two stages of chemical grade propylene. Its acrylic acid content is 94.44% by weight. The MB has reached 0.1483.
The inlet temperature T "6" 1 of the coolant in the area of the primary space of the respective crystallizer is about 2.1 ° C.
The outlet temperature Τκ3υδ of the refrigerant of the zone of the primary space of the respective crystallizer is about 4.7 ° C.
The mass flow of coolant supplied to the primary space of the respective catalyst ιτίκ reaches about 208 t / h.
The inlet temperature TH, iem of the coolant in the respective hollow section of the cooling discs of the respective crystallizer is about 12 ° C.
The outlet temperature TH, ia of the coolant I of the respective hollow section of the cooling discs of the respective crystallizer is about 10.4 ° C.
The mass flow of coolant I itih.i conveyed to hollow profiles of. crystallizer cooling discs; The total amount is approximately 43 t / h.
The inlet temperature Tpem of the liquid phase P in the respective secondary space is about 14 ° C.
The temperature Tsaus of the suspension S upon removal from the respective secondary space reaches about 7.0 ° C.
The acrylic acid content of the residual liquid phase R in the suspension removed from the secondary space S is 92.34% by weight.
The total molar fraction Ms, R9es of the different components of the acrylic acid in the aforementioned liquid residual phase R is 0.1991.
The intensity of the mass flow mp, to which the liquid phase P is fed to the secondary space of the respective crystallizer and the suspension S is removed from the secondary space of the respective crystallizer, is about 26.5 t / h. The result is a mw of about 25.0 t / h for each secondary space.
The inlet temperature Τη, ι® "1 of the heat transfer medium II in the space of the mid-tubular coils of the bottom of the buffer tank is about 32 ° C. The exit temperature THinaus of the heat transfer medium II the space of the mid-tubular coils of the bottom of the buffer tank is about 26 ° C. The total heat-transfer mass II conveyed in total to the space of coils of the bottom of the buffer tank is about 5 t / h.
The temperature T of the crystallizate suspension in the buffer tank is 7.7 ° C.
The operating state described above is maintained with the usual fluctuations as described above over a period of two weeks without difficulty. In this case, the reduction of supersaturation is observed continuously.
II. COMPARATIVE EXAMPLE
The procedure is as in the example, but the heat transfer agent stream II is not routed to the space of mid-tubular coils of the bottom of the buffer tank.
Instead, the half-tubular coil space closed from the bottom of the buffer tank contains a stationary liquid heat transfer medium II. The temperature of the crystallizate suspension in the buffer tank substantially corresponds to the temperature Tsaus of the suspension S at its removal from the respective secondary space. It does not follow from reducing the supersaturation as described in the example.
After an operating time of 4 days, the operation had to be interrupted, because a Kanalrat pump used to feed the crystallizer suspension washing column no longer carried the suspension S (shut off of the pipe and / or or pump).
US Provisional Patent Application Serial No. 60 / 971,994, filed September 13, 2007, is included in this application by reference to the literature.
With respect to the above teaching, many variations and many variations of the present invention are possible. It can therefore be concluded that the invention, within the scope of the appended claims, can also be realized other than as specifically described herein.

权利要求:
Claims (7)
[1]
A process for continuously separating a target product X in the form of a finely divided crystallizate of the target product X from a liquid phase P consisting of the target product X as well as components B, different from the target product X , the phase of which the total molar fraction of components B, has the value MB, p9es, comprising the operation of an indirect heat exchanger having a secondary space and at least one primary space, in which the secondary space and the at least one a primary space are spatially separated from one another by at least one material separating wall, which serves as a heat transfer surface of the secondary space in the at least one primary space, by introducing a liquid phase current P in the secondary space of the heat exchanger, while the at least one primary space is traversed simultaneously by at least one fluid refrigerant so that it is formed in the space s while maintaining a liquid residual phase R from the liquid phase P, a finely divided crystallizate of the target product X, which is suspended in the residual liquid phase R, and which contains, in comparison with the liquid phase P, , the different components of the target product X with a total molar ratio MB, Rgs> MB, p9es and whose target product content X reaches at least 70% by weight, while maintaining a suspension S, having a degree of crystallization Y, finely divided crystalline product target X in the liquid residual phase R, and is removed from the secondary space of the heat exchanger continuously S suspension at Tsaus temperature and, furthermore, including the routing of the suspension S removed at Tsaus temperature in a mixed buffer vessel, and with the aid of a pump, from the buffer vessel, the feed of a separation device by the suspension contained in the finely divided crystalline buffer container of the target product X and the separation of the slurry conveyed to the crystallizer separation device contained therein and in the liquid phase contained therein, characterized in that, on the the secondary space in the buffer vessel, in the buffer vessel itself and / or in one or more pump lines leading out of the buffer vessel and again in the latter, the temperature of the suspension S conveyed to the buffer vessel is increased using an external energy source at a TPu value above Tsaus and / or the total molar fraction of the different components of the target product X is contained in the residual liquid phase R of the suspension S conveyed to buffer container by external addition of different components of the target product X to a value MB, pu9es above MB, R9es.
[2]
2. Method according to claim 1, characterized in that

[3]
3. Method according to claim 1, characterized in that the increase of Mb, r96S to MB, pu9es with respect to MB, R9es is> 0.1%.
[4]
4. Process according to any one of claims 1 to 3, characterized in that the target product X is acrylic acid, methacrylic acid, N-vinylpyrrolidone or o-xylene.
[5]
5. Method according to any one of claims 1 to 4, characterized in that the content of the residual liquid phase R of the target product X is greater than or equal to 80% by weight.
[6]
6. Method according to any one of claims 1 to 4, characterized in that the content of the residual liquid phase R of the target product X is greater than or equal to 90% by weight.
[7]
7. Method according to any one of claims 1 to 6, characterized in that the degree of crystallization Y is 0.20 to 0.40.

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法律状态:

优先权:

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申请号 | 申请日 | 专利标题

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US97199407P| true| 2007-09-13|2007-09-13|

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DE102007043759|2007-09-13|

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US97199407|2007-09-13|

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DE102007043759A|DE102007043759A1|2007-09-13|2007-09-13|Procedure for continuous separation of target product in the form of fine particle of crystallisate, comprises indirectly operating a heat exchanger having primary and secondary areas, which are spatially separated with one another|

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