IE43206B1 - A process for separating crystallizable materials from a multi-component system - Google Patents

Abstract

1507034 Crystallisation process DEJ INTERNATIONAL RESEARCH CO BV 26 Nov 1975 [6 Dec 1974] 52900/74 Heading BIG A process for separating crystallisable material out of a multi - component liquid system comprises the following steps performed in sequence latchwise: (a) confining a batch of liquid in a heat exchanger, (b) applying cooling to the heat exchanger to crystallise at least part of the crystallisable material and create a substantially coherent matrix of crystals, (c) removing the material formed in step (b) from the heat exchanger, (d) breaking up the material from step (c) into a predetermined size and (e) separating crystallised material from the remainder of the multi - component system. Suitable aparatus, as shown in Fig. 1, for the freeze concentration of e.g. aqueous systems such as coffee extract and fruit juices, comprises a storage vessel (1), a number of shell and tube heat exchangers (3-12) mounted in parallel and connected to a central feed line, below the heat exchangers are an equal number of grinding means for breaking up the columns of ice and concentrate and simultaneously mixing the broken ice with recirculated concentrate and a washing column (13) for separating ice and concentrate. The process is carried out so that at the end of each freeze cycle the pump (2) pumps feed solution into the heat exchanger and so forces the columns of ice crystals and concentrate which have formed in the heat exchanger out of the exchanger, the columns of ice having first been released from the tube walls by briefly applying heat. A new freezing cycle starts when only a small frozen plug (28) remains in each tube (27). The frozen columns are broken up upon leaving the tubes by the knives (30) driven by a motor (33). The mixture of ice and concentrates enters the mixing vessel (32) at regular intervals and is transformed into a slurry for processing by the separating apparatus i.e. a washing column (13).

Description

The present invention relates to a process and apparatus for the separation of crystal!izable material out of a multicomponent liquid system, whereby in a first phase of the process crystallized material is produced within that multi-component liquid system by cooling, leaving a mother liquor, after which in subsequent phases of the process a mechanical separation (i.e. a separation without phase transformation) is accomplished between the crystallized material and the mother liquor.

The process is not only technologically very important in the case of freeze concentration of fruit juices, coffee extract and the like, but quite generally for the separation of a wide variety of crystal!izable chemical compounds from their solutions in solvents like water, alcohol or benzene.

It is on the grounds of economy of the utmost importance that the crystals are as little as possible contaminated with the mother liquor. In those cases where the valuable material resides in the crystals, contamination with mother liquor results in a less pure product which may necessitate a second crystallization process. On the other hand, when the substance to be recovered is to be found in the mother liquor, valuable material is lost by being discarded with the crystals (e.g. coffee extract contaminating the ice crystals in a freeze concentration process). A widely used process for the separation between a mass of crystals and mother liquor is centrifugation. The use of a centrifuge, however, has distinct disadvantages.

First, in the case of e.g. fruit juices, coffee extract and the like, flavour components may be lost by volatilization; secondly, oxidation of chemically delicate components ray take place leading to off-flavours. Moreover, generally removal of the mother liquor is not complete in one pass. These inadequacies of the centrifugation process have led to the development of the washing column, e.g. as described in U.S. P. Nos. 3,777,892 and 3,872,009. Presses are also often used e.g. in the case of freeze concentration of wine.

In all processes whereby the crystals are separated from the mother liquor it is important to have the crystals or crystal agglomerates so large and so homogeneous in size that separation from the mother liquor is easily accomplished. The resistance against liquid flow through the mass of crystals will be the lower, the larger in size the crystals or crystal agglomerates are and the more homogeneous. This is of particular importance when a washing column is being used. The packed column of crystals or crystal agglomerates will build up considerable resistance against liquid flow if the requirements about size and homogeneity of the crystals are not sufficiently met, which will adversely influence the capacity of the installation.

Crystallization processes for the separation in substantially pure form of a crystallizable component out of a multicomponent liquid system whereby the liquid is cooled creating crystals and a mother liquid, normally involve cooling this liiuid while it is thoroughly agitated (e.g. in a scraped surface he it exchanger) thereby inducing nucleating and having the 320 6 nuclei grow while in suspension. This is what we might call a dynamic process of crystallization. As fresh liquid is constantly brought into contact with the heat exchanger surface through which the cooling takes place, new nuclei are > constantly formed. Numerous methods have been proposed to advantageously influence size and homogeneity of the crystals in a ripening process, whereby growth and recrystal 1ization take place. In most cases these goals are not sufficiently attained, and if attained the equipment is rather bulky and the processes need careful regulation.

The process according to the invention for separating crystal!izable material out of a multi-component liquid system as herein defined, is performed batchwise, each batch being subjected to the following sequential steps: b a) a first step wherein a batch of the liquid is confined at rest in a treatment space of a static heat exchanger; b) a second step in which heat is withdrawn from said .the batch of/liquid confined at rest through the heat .of said heat exchanger exchange surface/so as to crystallize part of the crystal 1izable material and create a substantially coherent matrix of crystals with mother liquor trapped in between; c) a third step wherein the material after the foregoing treatment present in the space mentioned under (a) is extracted out of that space; d) a fourth step wherein the material extracted in step (c) is broken up; e) a fifth step in which the mass obtained in the foregoing step is treated in a mechanical separator to b substantially separate crystallized material from the rest of the multi-component system.

The inventive concept is as simple as it is radical in its departure from the principles hitherto applied in the art at issue.

Now when speaking in the foregoing about a crystal!izable material which we want to separate out of the multi-component system this will generally be one of the components which we want to separate out of the system in substantially pure condition. In principle however the crystallized crystallizable material may consist of mixed crystals (in the sense of more than one component in any crystal) this case thus not being excluded.

With the term liquid system is meant any system having sufficient fluidity to be pumpable and be readily introduced in the space mentioned under a). Thus e.g. a slurry is possible, containing solid material, and a foam containing gas or gas and solid materi al.

The space in which a batch of liquid is confined may of course be a combination of spaces. It can be a treatment chamber of any equipment which may be called a static heat exchanger 4330 6 whether known in the art or not and having a treatment space for holding liquid and a separate space for the circulation of a heat exchange medium. A static heat exchanger is any heat exchanger adapted to cool batchwise liquid introduced into its treatment space in order to induce crystallization and not provided with appurtenances to keep the liquid in a state of agitation while the cooling is proceeding. Generally the space should be rather narrow in order to keep the time necessary for an adequate degree of solidification of the liquid in that space within an economically acceptable range. Narrowness in this sense is to be understood in such a way that the cyrstallization process does not need to proceed more than about.5-25 mm away from the heat exchange Surface.

This we will call the maximum conductive distance.

Though spaces with flat heat exchange surfaces are not excluded, very conveniently long metal tubes can be used, particularly those having an inside diameter of about 20-30 mm; thus a maximum conductive distance of about 0-15 mm. These tubes can e.g. be provided each with a mantle for cooling purposes or they may be arranged as a bundle within one shell (as in a shell-and-tube heat exchanger).

Now, if we intend to use a mechanical method to separate the crystallized crystallizable material from the rest of the mu 1ti-component system, we will continue the cooling in step (b) only so far that the components which we do not want to mix with the crystallized crystallizable material remain in the liquid phase, be it in solution or in suspension. This liquid phase will be embedded in a matrix of crystals.

Preferably the cooling in this second step will be continued sufficiently that the matrix of crystals formed will bridge the treatment space. For the extraction in step (c) of the material present in the space after the cooling step (b) it is i> convenient to supply a small about of heat through the heat exchange surface, just sufficient to release the mass. This mass may fall out of the space by its own weight. Generally however, it will be desirable to push the mass out of the space by the application of pressure. This may be accomplished by a number of ways e.g. with gas or with a piston. In many cases the pressure to expel the crystal mass from the narrow space can conveniently be obtained by the introduction under pressure of a new batch of liquid to replace the treated batch. This means that the third step (c) of the cycle for any one batch of liquid coincides with the first step (a) of the cycle for tne next batch of liquid to be treated. Advantageously the crystal mass will not be completely expelled out of the narrow space, but part of it will be left remaining at the “expelling end of the narrow space. This will act as a plug to ensure proper separation between a treated batch and the next one yet to be treated.

Extraction and supply of heat through the heat exchange surface as mentioned above can be performed in any conventional way, but in a preferred embodiment of the invention using e.g. tunes as described above, heat is withdrawn in the first step of the cycle by connecting the space around the tubes with the evaporation chamber of a refrigerating unit and heat is supplied •χ Μ Μ V» vr in the third step of the cycle by connecting said space with the condensation chamber of the refrigerating unit.

Breaking up of the material extracted from the narrow treatment space can be performed in any conventional way, but advantageously this is done e.g. by a set of knives attached to a rotatable disk placed at the end of the space where the material emerges in the third step (c).

The mixture of crystals and mother liquor obtained in the fourth step (d) is often not sufficiently fluid to be easily fed to the separatory device which has to separate the crystals from the mother liquor.

If this holds true advantageously the broken up mass may therefore be transformed into a pumpable slurry or suspension by mixing it with mother liquor which is recycled from the separatory device.

The process as described above is not continuous. As the second step of the process in which heat is withdrawn so as to ensure crystallization takes much more time than the third step in which the crystal mass in the narrow space is extracted from the treatment space, advantageously a buffer will have to be created of treated material to be fed to the separatory device.

It is, however, possible to obviate this by parallel connection of a series of treating units and having each unit start its performance a little later than the foregoing one.

If e.g. we have ten units the first ma.y be performing the extracting step c) (and at the same time step a)), while the nine others will be performing the crystallizing step b).

After the first unit has finished the expelling step, the second unit will start with expelling. The first unit will have ended its second round of cooling when the tenth unit is through with its expelling step. In this way a virtually continuous stream of material may be kept feeding the separatory device.

According to another aspect of the invention, apparatus is provided specifically adapted for use in the processes described above. The apparatus according to the invention for separating part of the crystallizable component in substantially pure condition from a multi-component liquid system will comprise the following operationally connected parts: a) a static heat exchanger comprising a treatment space for holding liquid and a separate phase for the circulation of a heat exchange medium; b) means operationally connected with said heat exchanger, adapted to subdivide a substantially coherent mixture of crystals, formed in the treatment space of said heat exchanger, after extraction of this matrix of crystals out of the treatment space, into particles of a predetermined size. c) means adapted to separate crystallized material from a multi-component liquid system as herein defined which has been partly solidified by cooling in the treatment space of the heat exchanger.

Reiterating what has been already said above, under static heat exchanger we understand any heat exchanger adapted to cool batchwise liquid introduced into its treatment space in order to induce crystallization and not provided with appurtenances to keep the liquid in a state of agitation while the cooling is proceeding.

A multiplicity of these static heat exchangers may be arranged in parallel connection and provided with means adapted for sequential functioning (as already explained above), in order to obtaih a virtually continuous output of treated material.

Each of the static heat exchangers may be provided with separate means for subdividing the output of this heat exchanger, but a multiplicity of cooperating static heat exchangers may also be provided with one means for subdividing their output.

In a preferred embodiment of the invention the static heat exchanger will be tubular. In its simplest form this will be one metal tube, hut conveniently it will comprise a bundle of parallel arranged tubes. These tubes may be each surrounded by a tubiform mantle or providing a chamber for the circulation of the heat exchange medium (the coolant from the refrigeration unit) or they may be enclosed together in a common shell providing a common space for the heat exchange medium e.g. as in a shell and tube heat exchanger. Conveniently, > the inside diameter of the tubes will be about 10-30 mm. 43306 The means to subdivide the matrix of crystals mentioned under (b) will conveniently comprise a disk provided with knives and means to rotate said disk. This disk will prefer5 ably be located just outside that end of tne tubes where the matrix of crystals emerge when they are released and extracted from the tubes. Additional to the knives for cutting and breaking up the column of material emerging from the tubes the disk will conveniently be provided with slots as passageways for the particles created by this cutting action.

It is advantageous to place the disk just below the bottom end of the tubes, while these, in use, will preferably be in a substantially vertical position.

A possible arrangement when a multiplicity of co-operating static hear exchangers are provided with a single means for subdividing their output is for each static heat exchanger to comprise a parallel bundle of tubes and the tubes to be circularly arranged between two concentric shells, the combined bundles being provided at one end with a common disk at right angles to the axes of the tubes, and means to rotate said disk, the disk being provided with knives adapted to break up matrix of crystals emerging from the tubes when the apparatus is in operation.

The apparatus according to the invention as just defined above under a) and b) may be combined with the following appurtenances to form one unit; 6 · d) means to withdraw heat from the treatment space of the heat exchanger mentioned under a) and e) means to supply heat to said treatment space.

The means mentioned under d) and e) may conveniently comprise a refrigerator unit and means to alternately connect its evaporation chamber and its condensation chamber with the said separate space surrounding the treatment space wherein the heat exchange medium, i.e. the coolant, of that refrigerator is to circulate Processes and apparatus embodying the invention may be respectively more efficient and easier to regulate, and less bulky than is known in the prior art.

Examples of apparatuses according to the invention and the way these operate are illustrated in the Figures 1-3.

Figure 1 is a schematical representation of an apparatus according to the invention connected to a washing column and suitable e.g. for the freeze concentration of aqueous systems such as coffee extract and fruit juices. In this figure the following parts are shown: - a feed pump (2) with constant out-put, to dose a predetermined volume of liquid for each batch to be treated, fed from storage vessel (1). - a number of identical shell and tube heat exchangers (3) to (12) mounted in parallel and connected to a central feed line by valves (16) to (25). Below the heat exchangers an equal number of grinding means are provided for breaking up the columns of ice and concentrate and simultaneously mixing the broken up ice conglomerates with recirculated concentrate a washing column (13), represented schematics!ly for separating ice and concentrate - a concentrate recycling pump (14) a concentrate outlet (15) a melt water outlet (34) a concentrate recycle line (26) 'buffering' vessels (36) and (37) - a safety valve (38).

The process as it takes place in one heat exchanger will be described in a general way. At the end of each freeze cycle of heat exchanger (3> pump (2) pumps a given quantity of feed solution from storage tank (1) through line (35) to shell and tube heat exchanger (3), valves (17) to (25) being closed.

The columns of ice crystals and enclosed concentrate which have formed in the heat exchanger tubes during freezing are simultaneously forced out of the tubes. The columns of ice have first been released from the tube walls by briefly applying heat as described below. A new freezing cycle starts when only a relat ively small frozen 'plug' (28) remains in each tube (27) of the he.it exchanger (3). At that moment valve (16) is closed and coolant from the refrigerating unit (not shown) is introduced into the space between the shell and the tubes of heat exchanger (3) through valved line (29). The remaining plugs of ice are immediately frozen to the walls of the tubes (27) and the fresh solution starts to crystallize in tne tubes. 4320 6 At the end of each freezing cycle heat exchanger (3) is briefly connected to the condensation chamber of the refrigerating unit instead of to the evaporation chamber, a thin film of liquid being formed between column and tube wall. After valve (16) has been re-opened, the columns of ice and concentrate are replaced by fresh solution as described above. The frozen columns expelled by the fresh feed solution are broken up upon leaving the tubes by the knives (30) mentioned above. Through apertures in the disk the mixture of ice particles and concentrate passes to mixing vessel (32), which contains concentrated mother liquor. The cutting position of the knives and the speed of the rotation of the disk control the size of the ice particles. The speed of rotation of the disk, in combination with the number of knives, determines the time required to force out the columns of ice.

The rotating disk is driven by a motor (33) located outside the heat exchanger.

The mixture of ice particles and concentrate enters the mixing vessel at regular intervals and they must be transformed into a slurry which can easily be processes by the separating apparatus, which in this embodiment of the invention is a washing column (13) schematically shown. The percentage of ice in the slurry should preferably be about 25?-35% w.w.

To this end concentrate recycling pump (14) continuously circulates part of the concentrate so that in the mixing vessel the mixture of ice particles and concentrate is mixed with recycled concentrate in the right proportion. The slurry is immediately transported to the washing column.

The shell and tube heat exchangers are connected in such a way that at any given moment one heat exchanger is engaged in the expelling step, while the other exchangers are engaged in the cooling step. Thus a suspension of ice and concentrate is for all practical purposes continuously fed to the washing column and the refrigerating unit is loaded evenly. The concentrate discharged through outlet (15) and the melting water discharged through outlet (34) taken together have the same composition as the feed solution.

The melter of the washing column is connected to the condenser of the refrigerating unit and so also is the one heat exchanger in which a film of liquid is being formed to enable expulsion of the matrix of ice crystals.

Figure 2 is a cross section of the lower part of the heat exchanger with the 'cutting disk', according to a plane parallel to the axis of the tubes.

At (40) the wall of the tube is shown and at (39) the wall of the shell enclosing the tubes. At (41) we see the opening for the introduction of coolant. The tubes at their bottom end are fastened to the tube sheet (52).

The disk (42) is screwed on the axle (50), the upper end of which is threaded (53 i. The axle (50) passes through the bottom sheet (51). At (43) one of the knives protruding out of the upper surface of the disk is shown. The distance between the cutting edge of the knives and tha bottom end of the tubes can be adjusted by variation of the thin metal rings (49). 3206 The inlet and outlet for the recirculated mother liquor are shown at respectively (46) and (47), while (48) is the 'mixing chamber' where the crystal agglomerates are mixed with the recirculated mother liquor to form a pumpable slurry.

In Figure 3 we see a top view of the 'cutting disk' (42) and a drawing of part of the disk in perspective. In this perspective drawing the space (44) for inserting the replaceable knife (43) is shown for only one knife. At (45) we see a slot through which the particles of crystal agglomerates created by the action of the cutting knives pass through the disk.

In the underfollowing examples will be given of processes accomplished with the apparatus described above.

Example 1 A sugar solution containing 10% dry solid is concentrated to about 20% d.s. (specific mass of 10% d.s. is 1.04 kg/1, Equilibrium = ’0-5°C; specific mass 20% d.s. is 1.09 kg/1, Equilibrium = ” The apparatus used is represented in the Figures 1, 2 and 3.

Each heat exchanger is operated semi-continuously with a cycle time of 30 minutes, made up of a freezing time of about 26 minutes, a melting time of about 1 minute and an ejection time of about 3 minutes. The crystallizer consists of 10 shell and tube heat exchangers, each containing 6 stainless steel tubes with an internal diameter of 25 mm and a length of 3000 mm.

Below each heat exchanger a rotating disk, provided with 6 knives with a thickness of 5 mm is mounted. The knives protrude 1.8 mm above the disk. The distance between the edge of each knife and the bottom end of tha tubes is 3 mm. The disk is 3206 provided with apertures through which the ice particles pass into a mixing vessel below. The disk rotates at a speed of 79 revolutions a minute. The total holding capacity of the tubes is about 8.81 per heat exchanger. At the end of the ejection period, frozen plugs of a length of about 45 cm, which approximately equal 1,3 1, remain in the heat exchanger. At that moment there is about 7.5 1 fresh extract of 10% d.s. iri the space above the frozen plugs. This new batch of extract weighs about 7.8 kg and has a temperature of 0°C.

The extract is cooled by means of evaporating coolant.

The temperature difference between the contents of the tubes and the evaporation chamber formed by the space between the shell and the tubes is kept at about 8°C. 26 minutes after the start of freezing the original 7.8 kg extract has been transformed into about 3.9 kg ice and about 3.9 kg concentrated extract with a d.s. content of about 20%. The temperature of the ice columns is then about -1.5°C. The space between the shell and the tubes, i.e. the evaporation chamber of the refrigerating unit, is connected to the condensation chamber of the refrigerating unit so that heat is briefly applied to the tubes. A thin film of liquid forms on the walls of the tubes. Then the valve in the feed line with fresh feed solution is opened, so that the pressure of the feed pump is applied to the columns of ice and enclosed concentrate. The pressure differential across the length of the heat exchanger is about 5 atm. Owing to the difference in pressure the frozen columns are expelled from the tubes for a distance of about 2.55 m and are simultaneously broken up by the rotating disk with knives. 3306 The ice conglomerates formed are mixed with recycled concentrate in the mixing vessel to give a slurry with an ice concentration of about 30%. The slurry is transported to the washing column.

When the ice column has been expelled far enough, a new freezing cycle starts in the heat exchanger, after the valve in the feed line has been closed. At the same time expulsion starts in the next heat exchanger. At any given moment 9 heat exchangers are freezing extract and 1 heat exchanger is releasing and expelling the ice columns formed. The total concentrating capacity of the apparatus is about 75 1 fresh extract every 30 minutes, i.e. 150 1 fresh extract per hour. The washing column removes about 78 kg ice per hour. The capacity of the recycling pump is about 95 1 per hour (104 kg concentrate per hour).

Example 2 Coffee extract containing 10% dry solid is concentrated to about 34% dry solid (specific mass of 10% dry solid is 1.04 kg/1, specific mass of 34% dry solid is 1.16 kg/1). The apparatus used ‘ and its operation are described in example 1. The only differences are the following. minutes after the start of freezing the original 7.8 kg extract has been transformed into about 5.5 kg ice and about 2.3 kg concentrated extract with a d.s. content of about 34%.

The total concentrating capacity of the apparatus is about 75 1 fresh extract every 30 minutes, i.e. 150 1 fresh extract per hour. The washing column removes about 110 kg ice per hour.

The capacity of the recycling pump is about 182 1 per hour (211 kg concentrate per hour).

Claims (21)

CLAIMS 4 32 0 q

1. Process for separating crystal!izable material out of a multi-component liquid system as herein defined, the process being performed batchwise, each batch being subjected to the following sequential steps: a) a first step wherein a batch of the liquid is confined at rest in a treatment space of a static heat exchanger; b) a second step in which heat is withdrawn from said batch of the liquid confined at rest through the heat exchange of said heat exchanger surface/so as to crystallize part of the crystallizable material and create a substantially coherent matrix of crystals with mother liquor trapped in between; c) a third step wherein the material after the foregoing treatment present in the space mentioned under (a) is extracted out of that space; d) a fourth step wherein the material extracted in step (c) is broken up; e) a fifth step in which the mass obtained in the foregoing step is treated in a mechanical separator to substantially separate crystallized material from the rest of the multicomponent system.

2. Process according to claim 1 wherein the crystallization is continued so far that the matrix of ice crystals bridges the said treatment space.

3. Process according to any one of the preceding claims wherein the extraction of the substantially coherent matrix of crystals out of the said space as mentioned in claim 1 under (c) includes first releasing said matrix by briefly supplying heat to the heat exchange surface of the space so as to create a film of liquid between the matrix and the heat exchange surface. 1206

4. Process according to claim 3 wherein after release of the matrix of crystals this is forced out of the said space by the application of pressure.

5. Process according to claim 4 wherein the pressure is obtained by introducion of a new batch of liquid into the said space.

6. Process according to any one of the preceding claims wherein the static heat exchanger is essentially a shell and tube heat exchanger.

7. Process according to any one of the preceding claims wherein the material extracted from the treatment space is broken up by a rotating disk, provided with knives.

8. Process according to any one of the preceding claims wherein mother liquor from the mechanical separator is recycled and mixed with the broken up matrix of crystals extracted from the said space so as to form a pumpable slurry.

9. Process according to claim 8 wherein the separation between the crystallized material and the mother liquor is accomplished by a washing column.

10. Process according to claim 8 wherein the separation between the crystallized material and the mother liquor is accomplished by centrifugation.

11. Process according to any one of the preceding claims applied to an aqueous system.

12. Process according to claim 11 wherein the multi-component liquid system is coffee extract.

13. Process according to claim 11 wherein the multi-component liquid system is fruit juice. 43 30 6

14. Apparatus for use in a process according to any one of the preceding claims comprising the following operationally connected parts: a) a static heat exchanger comprising a treatment space for 5 holding liquid and a separate space for the circulation of a heat exchange medium; b) means operationally connected with said heat exchanger, adapted to subdivide a substantially coherent matrix of crystals, formed in the treatment space of said heat 10 exchanger, after extraction of this matrix of crystals out of the treatment space, into particles of a predetermined size. c) means adapted to separate crystallized material from a multi-component liquid system as herein defined which 15. Has been partly solidified by cooling in the treatment :·> space of the heat exchanger.

15. Apparatus comprising a multiplicity of static heat exchangers as mentioned in claim 14 under (a) connected in 'parallel and means for causing the sequential functioning of these 20 heat exchangers.

16.. Apparatus according to claim 14 or claim 15 wherein the or each static heat exchanger comprises a bundle of parallel arranged metal tubes at one end of which is provided a disk at right angles with the axis of the tubes and means to rotate said 25 disk, the disk being provided with knives adapted to break up a matrix of crystals emerging from the tubes when the apparatus is in operation. 4 3 2 0 6

17. Apparatus according to claim 15 whereby each static heat exchanger comprises a parallel bundle of tubes and the bundles are circularly arranged between two concentric shells, the combined bundles being provided at one end with a common disk at right angles to the axes of the tubes, and means to rotate said disk, the disk being provided with knives adapted to break up a matrix of crystals emerging from the tubes when the apparatus is in operation.

18. A process for separating crystal!izable material out of a multi-component system substantially as herein described with reference to the accompanying drawings.

19. A process for separating crystallizable material out of a multi-component system substantially as herein described with reference to either one of the examples.

20. Apparatus for separating crystallizable material out of a multi-coinponertt system substantially as herein described with reference to the accompanying drawings.

21. Material separated or concentrated by the process of any one of claims 1-13, 18 or 19 or with the apparatus of any one of claims 14-17 or 20.