DE10309832B4 - Method and device for obtaining a medium from a raw medium - Google Patents

Abstract

method for obtaining a medium from a raw medium, wherein the raw medium by means of a membrane separation device (30) into a permeate and a retentate is separated and the medium from the retentate by means of a distillation device (13), characterized in that the energy for the membrane separation process and for the distillation process by means of a common heating (14) provided.

Description

The The invention relates to a method for obtaining a medium a raw medium, wherein the raw medium by means of a membrane separation device is separated into a permeate and a retentate and the medium from the retentate is obtained by means of a distillation device. Furthermore, the invention relates to a device for obtaining a Medium from a crude medium, wherein a membrane separation device for the Separation of the crude medium into a permeate and a retentate and a distillation device are provided for recovering the medium from the retentate.

The reclamation of solvents Adopted for environmental and economic reasons Meaning too. With the help of conventional distillation can be however, process only a limited number of solvent mixtures.

to reclamation of solvents from solvent mixtures, for example in large laboratories in the course of analytical, preparative and separation work, the mixtures of impurities be freed. Often these impurities include water, which often passes through Simple redistillation can not be eliminated because the mixtures Azeotrope form or due to the substance by distillation, no high selectivity is possible. For large-scale Plants is under a sequence of distillation steps under Inclusion of the entrainer distillates worked. This process combination requires for a cost-effective Processing larger throughputs and one possible continuous operation. For Small amounts, the process is unsuitable.

Further were for the recovery of solvents from mixtures freezing techniques and salting out in combination with Proposed distillation. However, these procedures have barely prevailed because they are difficult to handle with toxic solvents and Follow-up problems with the residues exist. Therefore, these are methods reasonably practicable only for small quantities up to 3 kg.

at Quantities from about 100 kg solvent mixtures As a separation process, pervaporation can be used economically. However, this can not produce analytically pure solvents. Out the publications from Therre, Brüschke, Chemie Technik, 20th ed., 1991, No. 3, p. 63 f. or from Raiser, Steinhauser, Chemie Technik, 23 rd., 1994, No. 7, p. 44 ff., It is known that the drainage organic liquids with azeotrope formation by coupling of distillation with subsequent pervaporation of the distillate becomes. In these methods is enriched by distillation to azeotrope and this afterwards by pervaporation so far lowered in water content that as Retentate the desired Concentration of organic component arises. The retentate forms the product of the arrangement.

The Purity of the final product (retentate) of these plants is for technical Purposes sufficiently well. For use in the purest range of analysis are However, further treatments are necessary, because the product in the membrane process over countless Seals and surfaces the membranes are guided must and does not remain contamination free.

In US 5,868,906 describes a hybrid process of three plant sections for the recovery of isopropanol with high purity, whereby the recovery is carried out in large plants. The process is directed to the recovery of isopropanol on an industrial scale.

In DE 43 03 528 A1 Furthermore, a method for separating liquid mixtures having azeotropic boiling behavior by interconnecting pervaporation and distillation is described, wherein in a first process step by pervaporation, a mixture is concentrated to such an extent that the azeotropic composition is exceeded and in a second process step, the enriched component to the promoted purity is distilled by means of a distillation unit, and the resulting lighter or heavier boiling mixture of pervaporation is fed back. The reflux from the distillation to the pervaporation requires a continuous equilibrium column system to carry out a continuous separation of the mixture. The partial streams from the distillation to the pervaporation are taken off as side draw in the enrichment section, wherein the return flow takes place continuously and with constant composition. By optimizing the pressure in the distillation column, it is possible to use the heat of condensation from the distillation for pervaporation in the heat network. This presupposes that the membrane separation device and the distillation device are operated synchronously and always continuously in a network.

Moreover, it is off EP 0 596 381 A1 discloses a further continuous process for separating trioxane from an aqueous mixture wherein water is removed from the mixture by pervaporation and the water-depleted mixture (retentate) is decomposed by trioxane and an azeotropic mixture of trioxane, water and formaldehyde.

outgoing from this prior art, it is an object of the present invention a method and apparatus for recovering solvents from mixtures to provide a solvent with a high purity is obtained in a simple way and where it should be possible that smaller daily Quantities of about 10 kg to 100 kg of solvent mixture economically can be processed and cleaned at the place of origin.

Is solved this task according to the inventive method in that the energy for the membrane separation process and for provided the distillation process by means of a common heating becomes.

Both Functional parts, membrane separation device and distillation device, are for this coupled to a unit and collect together their required process energy from the bottom circulation heating of the distillation. The next to the target products naturally as by-products resulting, not sufficiently separated mixtures of each stage remain in the process and are each taken over by the other stage for processing. The separation-active steps, distillative rectification and membrane separation, are preferably discontinuous in coordinated parallel and serial program steps operated such that the internal transmission of material flows on the other level always takes place, if this in the achieved concentration for the further call separation one higher Achieved efficiency. Thus, a method is provided in those by distillation with integrated membrane separation circuit the separation mixture and the side stream mixtures of the process in a Permeate and a retentate are separated and the pure medium as Distillate of the retentate is recovered.

The Invention is based on the idea that a hydrous crude medium, the water is removed by means of the membrane separation device and the remaining mixture with the solvent in a combined Step the solvent is extracted in a high purity. By the nature of the integrative Combination of a distillation device with a membrane separator will be an economic recovery of solvents also on a small scale reached. Here, sporadic mixtures are pure solvent obtained, wherein the mixtures can form azeotropes and in the composition vary greatly. The plant simple in construction can by existing Laboratory staff easily operated and operated.

In addition, will toxic waste avoided. According to the invention is at the distillation device recovered the solvent. A discharge of the solvent does not occur through the membrane separator.

According to one advantageous development of the invention, the permeate is condensed, wherein the non-condensed fractions contained in the permeate in the Retentate be recycled. As a result, solvent components the water-rich membrane permeates, so that in effect only Water discharged with the membrane separation device or withdrawn becomes. It is thus ensured that the solvent no over the membrane separator is removed.

There the retentate of the membrane separation step as a solvent concentrate an intermediate product forms, which is worked up by the distillation stage and also the low solvent content of the permeate are recycled as an intermediate in the process, the membrane stage does not give any solvent (Medium) to the outside from. Advantageously, the permeates of a fractionating Subjected to step condensation.

Lies the water content in the crude medium is very high, e.g. over 20%, allows the inventive arrangement the advantage of reducing the operating energy costs Pretreatment. It will be first in the distillation part, the crude mixture in the water content to such Value diminished, in which the separation of pure water in the swamp the distillation still guaranteed is. This pretreatment leads to a separation medium for the subsequent steps, whose water content is already close to the Height of Azeotrope lies.

advantageously, are the non-condensed fractions contained in the permeate condensed.

Lies the water content in the raw medium over one fixed value, e.g. 20%, it is beneficial if the raw medium is pretreated by means of the distillation device. Thereby is achieved that the water content of the raw medium to a lower Value is lowered.

Especially the raw medium becomes aqueous Raw medium provided.

According to one advantageous embodiment of the method, the membrane separation device after operated on the principle of pervaporation and vapor permeation.

In a preferred embodiment, the permeate is increased in its water content and the Re tentat in its water content lowered.

to Recovery of the solvent from the retentate, in particular, the water content of the retentate reduced to a predetermined value.

preferably, the medium becomes after reaching a predetermined value of the water content recovered in the retentate.

at an advantageous embodiment of the method is from a solvent-based Raw medium at least one solvent recovered as end product.

at An advantageous development of the method is the water content adjusted retentate fed to a distillative treatment and at least one pure solvent recovered as end product.

Of the The residual water content of the retentate to be adjusted becomes azeotropic forming mixtures are preferably chosen so that the remaining residual water content in the distillative treatment as a lead still economical can be cut out.

Of the to be adjusted residual water content of the retentate is not azeotropic forming mixtures preferably chosen so that the residual water at the distillative treatment of low-boiling media in the distillation residue or in high-boiling media as a lead still be cut out can.

Further The object is achieved according to the device according to the invention solved by that for the Membrane separation device and the distillation device a common Heating is provided. Therefor are a membrane separation device for the separation of the raw medium in a permeate and a retentate, and that a distillation device intended to recover the medium from the retentate. These separating active Stages are linked by it; that they share functional parts in common use, in particular the heating system, collecting tanks for intermediates, process control and agitation and independent the type of raw medium also a common coolant supply.

The Advantages achieved by the inventive device solution These are essentially the benefits that are related above called with the process solution according to the invention have been. For the non-condensed fractions contained in the permeate is at least one condensation device for the permeate is provided.

advantageously, are recycling agents for in the permeate included, uncondensed fractions formed to retentate.

The Invention will be described below without limiting the general inventive concept of exemplary embodiments with reference to the drawings, to the rest with respect to all not closer in the text explained details of the invention expressly is referenced. Show it.

1 the basic structure of the device by means of which the method according to the invention can be carried out;

2 a cross section through a membrane separation device;

3 the basic structure of an alternative arrangement for carrying out the method according to the invention and

4 the basic structure of another arrangement.

In the figures are the same or similar elements or parts with provided with the same reference numerals, so that of a new idea each is apart.

In 1 is a block diagram of an apparatus for carrying out the method shown schematically. The device 10 has a distillation facility 13 with a heater 14 to which a liquid to be separated 11 as input medium is given on the input side, and via a membrane separation device 30 , Is the water content of the liquid to be separated 11 For example, over 20%, a pre-separation is carried out, for example, with a bubble distillation, so that as the bottom in the distillation device 13 a water fraction is obtained with high-boiling and non-volatile substances. The distillate is the liquid to be separated 11 with a water content of, for example, 20% via a line 15 and a capacitor 16 condensed and into a container 20 directed to the intermediate storage. If the initial water content of the liquid to be separated from the outset is not higher than 20%, eliminating the pretreatment of the liquid to be separated 11 or the pre-distillation.

The into the distillation device 13 introduced and to be separated liquid 11 is via lines 17 . 18 in a circuit with a membrane separator 30 coupled. Using the heater 14 the liquid to be separated is heated and passed over the line 17 on the membrane separation device 30 directed. The membrane separator 30 is operated according to the principle of vaporizing steam.

That from the membrane separation device 30 over the line 18 guided retentate is the distillation device 13 fed again. In addition, the in the container 20 collected liquid are also added to the retentate.

By means of the membrane separation device 30 Water is withdrawn from the heated and liquid to be separated, so that from the membrane separation device 30 leaking permeate is enriched in its water content.

Since the exiting permeate, in addition to water, also has small amounts of residual constituents, for example of solvents, the permeate is passed through a conduit 40 on a capacitor 41 directed so that the water component is essentially deposited there and over the line 42 is led away. The non-condensed solvent-water mixture portion is as residual vapor via a line 43 from a pump 45 sucked in and over another capacitor 44 directed so that the remaining solvent-water mixture in the container 20 is separated and collected. As a result of the recycling of the solvent-water mixture, solvent-containing components are separated from the exiting permeate and added to the solvent-containing retentate, so that the water content of the liquid to be separated is reduced without solvent being lost. As the liquid to be separated is increasingly withdrawn water by means of the membrane separation device, the dewatering rate in the membrane cycle decreases steadily with increasing degree of drying of the circulating retentate. Therefore, it is recommended that the pervaporation cycle is not operated to total dryness, but that the retentate has a low residual water content of <1%, preferably <0.5%, provided that the crude mixture can form water azeotropes. The low residual water content is then completely cut out in advance in the subsequent rectifying distillation of the total tetracycline as a precursor in the form of the water-solvent azeotrope which forms the light-boiling fraction. It gets into the container 20 derived for products and intermediates of the membrane separator and remains in the process. The subsequent main run of the rectifying distillation consists of pure anhydrous solvent which forms the yield and the target product.

In the container 50 the yield of the process is collected in the form of a solvent of high purity, which is passed through a conduit 55 is led away.

A special feature of the membrane separation device 30 lies in the mode of operation according to the invention is that over the time course of the membrane separation process, the membranes with initially very water-rich until towards the end very low-water feed mixtures are applied, whereby the temperature of Memb ranoberflächen can vary during operation. It results in contrast to the usual mode of operation no permanent stationary state in the membrane area. Since the membranes react to changes in the level of the water content of the separation medium and different temperatures due to surface elongation or contraction, it must be ensured that the membrane set can withstand the damage caused by the procedure according to the invention continuous expansion game. In a conventional rigid fixation of the membranes, for example by outer edge seals on the housing, membranes would be exposed to shear forces and form wrinkles, so that the life of the membranes would be significantly reduced.

In 2 is schematically a membrane separation device 30 shown in cross section, which does not limit the expansion game and favors the procedure of the invention. The membrane separator 30 has a centrally arranged Permeatableitrohr 31 on, that of plate-shaped membranes 34 is surrounded. The membrane surfaces are connected at the outer edge back to back and hermetically sealed, so that the expansion thrust is compensated for differently supplied water content of the separation medium. As a result, shear forces and frictional contacts on the housing or outer seals are avoided. The membranes 34 and the permeate discharge tube 31 are in a housing 38 with a feed 32 and a process 33 arranged.

When Membranes are particularly solvent-stable Membranes used with a selective water transport. These Membranes can with Membrane separation layers based on organic polymers or copolymers and inorganic materials in the form of selective ceramic layers or ceramic-metal combinations consist.

In 3 a further embodiment of the device according to the invention is shown in a schematic arrangement. This is the contents of the container 20 during the distillation by means of a heat exchanger 23 and a pump 22 via a connecting line of the membrane separation device 30 fed. The membrane separator 30 separates from that in the container 20 accumulated mixture predominantly water, while subsequently contained in the permeate, non-condensed solvent residues in a container 12 attributed to who the. In this container 12 , the distillation unit 13 is upstream, the liquid to be separated 11 taken in and mixed with the solvent-containing substances of the permeate. That at the condenser 41 separated water of the permeate is placed in a container 46 collected and then drained.

During the separation of the water from the container 20 accumulated medium is the connection 17 closed.

In 4 a further embodiment of the device is shown in a schematic diagram, wherein a return of the non-condensed solvent contained in the permeate in the container 20 he follows. A pump 21 promotes the hot medium from the heated floor space of the distillation device in this embodiment 13 together with the intermediates of the container 20 through the membrane separation device, thus forming the drainage loop of the system.

The capacitor 41 is shown in all three shown embodiments of the invention ( 1 . 3 . 4 ) is operated at a surface temperature of, for example, 275 ° K, so that water is deposited under the prevailing vacuum, via the line 42 is dissipated.

The distillation device 13 is operated on the principle of rectification distillation, wherein the first distillate of the rectification forms on separation of the solvent from the retentate a flow, so that due to the bottoms concentration above an azeotrope reinforced water is distilled near the azeotrope composition. The flow is in the intermediate container 20 derived. After achieving a desired dryness of the distillate stream, the subsequent distillate is added to the container 50 passed and the contents of the distillation device 13 distilled.

example 1

A mixture of acetonitrile with 50% water content is intended with a device according to 3 be treated. The amount of acetonitrile to be separated is added to the container 12 4.5 kg of a mixture of 14% acetonitrile and 86% water as by-products of previous treatment courses. At the start, the total amount of 34.5 kg of the mixture with 45.2%, acetonitrile and 54.8% water and dissolved salts in the distillation device 13 directed. With a heating power of 6 kW at a reflux ratio of 2: 1, the amount introduced in the distillation device 13 fractionated. The distillate is condensed and enters the container 20 , After 3.5 hours, the rectification is stopped. The in the distillation device 13 remaining sump consists besides salts of water and possibly high-boiling and acetonitrile with approx. 0.02%. This remaining sump, after the rectification end, continues to act as heating fluid for the membrane device 30 used. Addition of sodium hypochlorite destroys the residual organic substance in the sump and converts the acetonitrile into the harmless ammonium acetate. By means of the pump 21 and the heat exchanger 23 and further lines, the heating circuit for supplying the membrane separator is formed from the distillation bottoms. In the container 20 are 19.54 kg 80% acetonitrile with a water content of 20%.

The contents of the container 20 is already during the course of the distillation through the membrane stage circuit 20 . 23 . 22 . 30 Deprived of water. The circulation operation is continued until a desired degree of dryness of the acetonitrile is reached. The duration depends on the size of the membrane separation module and the desired degree of dryness. In the context of this example, the in the container 20 accumulated amount with dried to a proportion of 99.9% acetonitrile, so that 15.015 kg remain as a retentate.

This via the membrane separation device 30 Separated permeate adds up over the process time to 4.5 kg and consists on average of 86% water and 14% acetonitrile. The capacitor 41 , which operates at a surface temperature of 275 ° K, separates water from that in the refrigerated container 46 is collected under the prevailing vacuum and has a mass of 2.725 kg. The at the condenser 41 as a result of the vacuum applied there, non-separated permeate vapor is passed through the vacuum pump 45 in the post-condenser 44 passed and deposited there at atmospheric pressure. There fall to 1.145 kg of a condensate with 45% water and 55% acetonitrile and drop through a pipe into the sump 12 ,

Into the free, dry distillation device 13 then the acetonitrile of the membrane circulation from the container 20 and subsequently rectified at a reflux ratio of .667. In this case, a flow of about 250-350 ml with about 3-5% water in the container 20 and then the pure acetonitrile as a yield with a mass of 15 kg to the container 50 distilled. For a better understanding, the complementary separation processes are added 13 and 30 explained as a step sequence. By coordinative process control, the separation steps in the execution are handled simultaneously or temporally overlapping.

Example 2

According to the in 4 illustrated principle is in the distillation device 13 a mixture of collected solvent fractions and the intermediates of the vessel 20 filled with a total mass of 28 kg, which consists of 18% water and 82% acetonitrile with little contamination by large organic molecules. The mixture to be separated is dewatered in the membrane circulation up to 99.5% and a quantity of 22.3 kg. The permeate formed has a mass of 5.7 kg and consists of 86.47% water and 13.53% acetonitrile. After leaving the membrane module, the permeate vapor mixture reaches the condenser 411 operated with cooling brine from 272 to 275 K. There condenses over the process time from a water fraction, which is in the container 46 with 4.0 kg and 99.82% water.

The residual fraction of the permeate of 1.7 kg with 55% water and 45% acetonitrile drips into the container 20 , At a residual water content in the bottom of the distillation device 13 of 0.5% is the circulation pump 21 switched off.

At a reflux ratio of 0.5 and low distillation capacity, a feed distillate with about 14% water content is passed over the line 15 in the container 20 directed. There it is united with the residual permeate fractions. After about 1 liter of flow collection, the line 15 closed and the contents of the distillation device 13 in the container 50 distilled over. As a yield for reuse 21.5 kg of acetonitrile with high purity and a water content <0.1% are obtained. The in the container 46 accumulated amount of 4 kg of water is drained, with the addition of a small amount of sodium peroxide or hydrogen peroxide acetonitrile tracks are destroyed after an appropriate residence time, so that the accumulated water can be discharged into a spout system.

In the container 20 In the apparatus for the intermediates, the non-directly recyclable residue is combined with 2.3 kg of the composition of 54.53% acetonitrile and 45.47% of water added to the feed for a subsequent pass to recover the solvent.

Provided residues from Solids or high songs in the distillation device accumulated have, these are over a line in a usual disposal containers for organic Waste to Combustion drained.

Example 3

According to the in 4 represented principle, propanol-2 is obtained. There is a lot of 40 kg of liquid to be separated in the container 12 provided in the distillation device 13 is directed. The distillation device 13 separates the mixture of 60% propanol-2, 39.9% water and 0.1% dissolved substances, consisting of potassium chloride, monosaccharides, soluble oligosaccharides and low surfactants, at a reflux ratio of 2: 1, wherein the heating power about 6 kW is. The distillate is made by means of the condenser 16 condenses, with the yield in the container 20 is directed. After 3.5 hours, 30.77 kg of 78% propanol-2 are obtained with 22% water. From the previous separation process are in the container 20 still 0.41 kg of the same composition, so that a total of 31.18 kg is available. In the distillation bottoms are 9.19 kg of water with 0.04 kg of dissolved salts and a residual load of propanol-2 of <300 ppm, which are discharged into a clarifier.

The contents of the container 20 is over the line 18 into the distillation device 13 which is operated as reflux distillation, while the distillation bottoms are dried by means of the membrane separation device. To 16 Hours are 24.2 kg retentate in circulation with 1% residual water content. The total permeate is 6.97 kg with a water content of 95%. At the permeate condenser 41 6.25 kg of water are separated from it. For the second permeate condenser 44 0.7 kg of a mixture containing about 50% propanol-2 and 50% water are separated and placed in the container 20 directed.

The distillation device 13 is switched to partial withdrawal, and over the line 15 is a flow of 99% propanol-2 of about 0.2 kg in the container 20 passed to the permeate of the membrane stage and the pure 99% propanol-2 in the container 50 distilled. Thereafter, 24 kg of propanol-2 of the desired purity over the line 55 bottled.

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contraption

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to separating liquid

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intermediate container

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distillation device

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heater

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management

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capacitor

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container

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pump

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pump

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heat exchangers

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Membrane separation unit

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Permeatableitrohr

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Intake

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procedure

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membrane

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casing

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permeate

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capacitor

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management

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capacitor

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compressor

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Claims (13)

Process for obtaining a medium from a raw medium, the raw medium being separated by means of a membrane separation device ( 30 ) is separated into a permeate and a retentate and the medium from the retentate by means of a distillation device ( 13 ), characterized in that the energy for the membrane separation process and for the distillation process by means of a common heating ( 14 ) provided. Method according to claim 1, characterized in that that the permeate is condensed, whereby in the permeate contained, uncondensed fractions are recycled to the retentate. Method according to claim 2, characterized in that that the non-condensed fractions contained in the permeate be condensed. Method according to one of claims 1 to 3, characterized that the raw medium pretreated by means of a distillation device becomes. Method according to one or more of claims 1 to 4, characterized in that the raw medium as an aqueous Raw medium is provided. Method according to one or more of claims 1 to 5, characterized in that the membrane separation device according to the principle of pervaporation or vapor permeation is operated. Method according to one or more of claims 1 to 6, characterized in that the permeate in its water content elevated is and the retentate is lowered in its water content. Method according to one or more of claims 1 to 7, characterized in that the water content of the retentate a predetermined value is reduced. Method according to one or more of claims 1 to 8, characterized in that the medium after reaching a predetermined value of the water content in the retentate is obtained. Method according to one or more of claims 1 to 9, characterized in that from a solvent-containing raw medium at least one solvent is obtained as a final product. Device for obtaining a medium from a raw medium, wherein a membrane separation device ( 30 ) for the separation of the crude medium into a permeate and a retentate and a distillation device ( 13 ) are provided for recovering the medium from the retentate, characterized in that for the membrane separation device ( 30 ) and the distillation device ( 13 ) a common heating ( 14 ) is provided. Device according to claim 11, characterized in that in that at least one condensation device for the permeate is provided. Device according to claim 11 or 12, characterized in that that repatriation agent for im Permeate contained, uncondensed fractions formed to retentate are.