EP1938036B1 - Tube bundle heat exchanger and method for removing dissolved substances from a polymer solution by means of degassing in a tube bundle heat exchanger - Google Patents

Abstract

The invention proposes a tube bundle heat exchanger (R) for removing dissolved substances from a polymer solution (4) by means of degassing, having a bundle of tubes (1) which are arranged parallel to one another and vertically and are fastened at both ends in each case in a tube base (2), having a fixture (3) in each tube (1) which narrows the free passage cross section through the tube (1), wherein the tubes (1) are traversed by the polymer solution (4), and having a casing space (5) around the tubes (1) which is traversed by a liquid heat carrier (6), having deflecting plates (7) in the casing space (5) which are each arranged in cross-sectional planes of the tube bundle heat exchanger (R) and in each case form a deflecting region (8) for the heat carrier (6), which tube bundle heat exchanger (R) is characterized in that no tubes (1) are arranged in the deflecting regions (8), and in that all the fixtures (3) are of identical design.

Description

The invention relates to a tube bundle heat exchanger for the removal of solutes from a polymer solution by degassing, a continuous process for the removal of solutes from a polymer solution by degassing in a shell and tube heat exchanger and a use. US-A-3 426 841 describes a tube bundle heat exchanger according to the Oberbergriff of claim 1.

An essential process step in the preparation of polymers is the removal of solutes from the solution obtained in the polymerization, in particular unreacted monomers, low molecular weight reaction products (oligomers), decomposition products, excipients and solvents to represent the concentrated polymers in a technically utilizable state ,

The isolation of the solutes from polymer solutions is often carried out by degassing, the dissolved substances are converted by heat and optionally pressure reduction in the vapor state and separated in this from the liquid polymers.

Apparatively, the degassing of polymer solutions is often carried out in Rohrbündelwärmeübertragem, with a bundle of parallel and vertically arranged tubes which are fixed at their ends in each case in a tube bottom and wherein a heat carrier is passed through the shell space between the tubes, the polymer solution and the Relaxation product of the polymer solution heated.

Known tube bundle heat exchangers for degassing of polymer solutions can often not meet strict quality requirements regarding permissible residual contents of dissolved substances in the degassed polymer solution.

In order to ensure the most uniform heat transfer coefficient in the apparatus from the heat transfer medium through the pipe wall in the liquid polymer solution, a Queranströmung the tubes is sought by the flow direction of the heat carrier in the shell space is controlled by the installation of baffles.

These may be formed, for example, in the form of circular segments, which leave open alternately at the opposite inner pipe walls passage cross-sections.

Another common design consists in the alternating arrangement of annular and disc-shaped baffles, which leave open alternately passage cross-sections for the heat transfer medium in the reactor center or on the reactor inner jacket.

While the tubes arranged in the region of the baffles are flowed transversely by the heat carrier, there is a predominant longitudinal flow through the heat carrier for the tubes in the deflection regions which are free of baffle plates. Accordingly, the heat transfer in the tubes with longitudinal flow is worse and consequently the product quality in the individual tubes over the reactor cross-section unequal.

It is known to provide internals in the individual tubes, which narrow the free passage cross-section in order to build up a pressure drop and to effect an improved heat transfer from the heat transfer medium to the polymer solution to be degassed.

Due to the above-described uneven heat transfer due to the different flow of the tubes through the heat carrier in particular unequal internals over the reactor cross section are required to compensate for this effect. This requires an increased effort in the production and in particular in the assembly of the internals.

It was accordingly an object of the invention to provide an improved process for degassing a liquid polymer solution in a Rohrbündeiwärmeübertrager available, which ensures lower residual contents of solutes at the same time simpler design and installation of the apparatus.

The solution consists in a shell and tube heat exchanger for the removal of solutes from a polymer solution by degassing, with a bundle of parallel to each other and vertically arranged tubes, which are fixed at both ends in a tube plate, with an installation in each tube, the free Narrowed passage cross-section through the tube and wherein the tubes are flowed through by the polymer solution, as well as with a jacket space around the tubes, which is flowed through by a liquid heat carrier, with baffles in the shell space, which are each arranged in cross-sectional planes of the tube bundle heat transfer and each a deflection for the Release heat carrier, which is characterized in that in the deflection no pipes are arranged and that all internals are identical.

By installing a strong pressure drop from an inlet pressure of up to 50 bar absolute on a very low vacuum, often in the range between 4 and 200 mbar, in particular between 4 and 30 mbar, causes.

The internals, which are arranged in the tubes and narrow the free passage cross section of the same, may preferably be fixed by a threaded screw in the tube plate, wherein the welds of the tubes in the tubesheet below the threaded connection for the internals. As a result, the internals for cleaning the apparatus can be easily installed and removed.

The internals are preferably screwed into the tubesheet with a Vielzahnschlüssel, preferably a hexagonal Allen key. The insert opening for the multi-tooth key is preferably arranged centrally and continuously in the installation. As a result, it can be advantageously used after screwing in the installation and removing the key for the supply of the polymer solution.

The invention is not limited with regard to the specific design of the baffles and the deflection areas released from them. Preferably, the deflection regions, which are released from the baffles for the heat carrier, formed within the shell space of the tube bundle heat exchanger. This may preferably be baffles in the form of circular segments, which leave the deflector for the heat transfer medium alternately on the inner shell of Rohrbündelwärmeübertragers or to baffles, which are formed alternately in ring or disc shape, such that the baffles release in the form of deflection areas , which are arranged centrally in the tube bundle heat exchanger and the disc-shaped baffles release deflection areas, which are arranged on the inner shell of the tube bundle heat exchanger.

In a further constructive variant, one or more chambers may be provided on the outer shell of the tube bundle heat exchanger, through which the heat transfer medium circulates through perforations in the outer jacket of the tube bundle heat exchanger and wherein the deflection regions which are released from the baffles for the heat transfer medium are arranged in the chambers the perforations serve to equalize the flow.

The heat carrier is preferably in each case via a ring channel or partial ring channel in the mantle space or removed, wherein the annular channel or partial ring channel has openings, preferably such that their free passage area decreases in the flow direction of the heat carrier.

The shell-and-tube heat exchanger is preferably designed in such a way that the heat transfer coefficient heat transfer coefficient is between 500 and 2000 W / m ² / K, preferably 800 to 1200 W / m ² / K.

Preferably, a liquid heat transfer medium, in particular a heat transfer oil, is used.

The tube bundle heat exchanger preferably comprises 100 to 10,000, preferably 450 to 3,500 tubes, in particular a length between 1.0 and 6.0 m, preferably between 1.2 and 2.0 m and an inner diameter between 10 and 25 mm, preferably between 13 and 18 mm. The baffles are preferably formed with a thickness between 6 and 30 mm, in particular between 8 and 16 mm.

Preferably, the tube bundle heat exchanger is designed in such a way that the upper tube sheet is substantially thicker compared to the lower tube plate, in particular five times thicker, preferably that the upper tube plate 150 mm thick and the lower tube plate is 30 mm thick.

Preference may be provided in the upper tube sheet or shortly below the same vent holes for the heat transfer medium, via which a pipeline leads to a surge tank or a collecting container.

Advantageously, an emptying system for the heat transfer medium can be provided via the lower tube plate or via a bore in the wall of the tube bundle heat exchanger.

It is advantageous not to roll the tubes in the baffles, but to make sure during manufacture that the gaps between the tubes and the baffles are as small as it is possible in terms of manufacturing technology, in particular in the range between 0.1 to 0.4 mm, preferably in the range between 0.14 and 0.25 mm.

The baffles are preferably made sealingly to the wall of the Rohrbündeiwärmeübertragers.

It may be advantageous not to equidistantly arrange the baffles, but to specifically adjust the distance of the baffles to each other the degassing process in the tubes, in such a way that the heat transfer coefficients in the pipe sections are higher, where this is necessary for procedural reasons.

Advantageously, a compensator for the thermal expansion in the shell of the shell and tube heat exchanger is provided.

In particular, for the degassing of multi-component products, such as ABS solutions, the tube bundle heat exchanger can be formed two or more zonig, such that two or more separate circuits are provided for the heat carrier to achieve a different temperature and thus different Entgasungsstadien.

The invention also provides a continuous process for the removal of solutes from a polymer solution by degassing in a shell and tube heat exchanger as described above, wherein the polymer solution is passed from top to bottom through the tubes of Rohrbündelwärmeübertragers and the heat transfer medium in the cross countercurrent or in the cross-direct current to the polymer solution.

The procedure with direct conduction of polymer solution and heat carrier, respectively from top to bottom through the apparatus, is particularly suitable when overheating is desired already in the inlet region of the polymer solution in the apparatus, for example in the degassing of polystyrene.

The invention also relates to the use of the above-described Rohrbündelwärmeübertragers for degassing of polystyrene or ABS.

The invention will be explained in more detail below with reference to a drawing and an embodiment.

Figur 1

einen Längsschnitt durch eine bevorzugte Ausführungsform eines erfindungsgemäßen Rohrbündelwärmeübertragers mit Kreuzgegenstromführung von Polymerlösung und Wärmeträger, mit Darstellung eines Querschnittes in der Ebene B-B in Figur 1A,

Figur 2

einen Längsschnitt durch eine weitere bevorzugte Ausführungsform eines erfindungsgemäßen Rohrbündelwärmeübertragers unter Radialstromführung des Wärmeträgers, mit Querschnittsdarstellung in der Ebene E-E in Figur 2A,

Figur 3

einen Längsschnitt durch einen Reaktor mit Kreuzstromführung des Wärmeträgers nach dem Stand der Technik, mit Querschnittsdarstellung in der Ebene A-A in Figur 3A,

Figur 4

eine Längsschnittdarstellung durch einen Rohrbündelwärmeübertrager nach dem Stand der Technik, mit Radialstromführung des Wärmeträgers, mit Querschnittsdarstellung in der Ebene E-E in Figur 4A,

Figur 5

eine Längsschnittdarstellung durch eine weitere bevorzugte Ausführungsform eines erfindungsgemäßen Rohrbündelwärmeübertragers, mit Querschnittsdarstellung in der Ebene C-C in Figur 5A und Querschnittsdarstellung in der Ebene D-D in Figur 5B,

Figur 6

einen Längsschnitt durch eine weitere bevorzugte Ausführungsform eines erfindungsgemäßen Rohrbündelwärmeübertragers mit Gleichstromführung von Polymerlösung und Wärmeträger,

Figur 7

einen Längsschnitt durch eine weitere bevorzugte Ausführungsform eines erfindungsgemäßen Rohrbündelwärmeübertragers, der mehrzonig ausgestaltet ist,

Figur 8

einen Längsschnitt durch eine weitere bevorzugte Ausführungsform eines erfindungsgemäßen Rohrbündelwärmeübertragers mit Radialstromführung des Wärmeträgers und Gleichstromführung von Polymerlösung und Wärmeträger,

Figuren 9A bis 9C

bevorzugte Ausführungsformen von Hauben für den Rohrbündelwärmeübertrager,

Figur 10

einen Längsschnitt durch eine bevorzugte Ausführungsform eines erfindungsgemäßen Rohrbündelwärmeübertragers mit Dummy-Körpern in den Hauben des Apparates und

Figuren11A und 11B

bevorzugte Ausführungsformen für die Öffnungen in den Ringkanälen für die Zu- und Abführung des Wärmeträgers.

They show in detail:

FIG. 1

a longitudinal section through a preferred embodiment of a Rohrbündelwärmeübertragers invention with cross-countercurrent flow of polymer solution and heat transfer medium, with representation of a cross section in the plane BB in Figure 1A .

FIG. 2

a longitudinal section through a further preferred embodiment of a Rohrbündelwärmeübertragers invention under radial flow guidance of the heat carrier, with a cross-sectional view in the plane EE in FIG. 2A .

FIG. 3

a longitudinal section through a reactor with cross-flow guidance of the heat carrier according to the prior art, with a cross-sectional view in the plane AA in FIG. 3A .

FIG. 4

a longitudinal sectional view through a tube bundle heat exchanger according to the prior art, with radial flow guidance of the heat carrier, with a cross-sectional view in the plane EE in FIG. 4A .

FIG. 5

a longitudinal sectional view through a further preferred embodiment of a Rohrbündelwärmeübertragers invention, with a cross-sectional view in the plane CC in FIG. 5A and cross-sectional representation in the plane DD in FIG. 5B .

FIG. 6

a longitudinal section through a further preferred embodiment of a Rohrbündelwärmeübertragers invention with DC control of polymer solution and heat transfer medium,

FIG. 7

a longitudinal section through a further preferred embodiment of a Rohrbündelwärmeübertragers invention, which is configured mehrzonig,

FIG. 8

a longitudinal section through a further preferred embodiment of a Rohrbündelwärmeübertragers invention with radial flow of the heat carrier and DC flow of polymer solution and heat transfer,

FIGS. 9A to 9C

preferred embodiments of hoods for the tube bundle heat exchanger,

FIG. 10

a longitudinal section through a preferred embodiment of a Rohrbündelwärmeübertragers invention with dummy bodies in the hoods of the apparatus and

Figures 11A and 11B

preferred embodiments of the openings in the annular channels for the supply and discharge of the heat carrier.

In the figures, like reference numerals designate like or corresponding features.

The in FIG. 1 shown tube bundle heat exchanger R has a bundle of tubes 1 through which a polymer solution 4 is passed from top to bottom. The tubes 1 are attached sealingly at their two ends in a tube plate 2. In the tubes 1 internals 3 are provided, which narrow the passage cross-section for the liquid polymer solution 4. All fittings 3 are identical.

In the jacket space 5 between the tubes 1 baffles 7 are arranged, which are formed in a circle segment and the alternately on the inner wall of the Rohrbündelwärmeübertragers R deflection 8 for the heat transfer medium 6 release.

The cross-sectional view in Figure 1A illustrates that the deflection areas 8 are free of tubes 1.

FIG. 2 shows a further preferred embodiment of a Rohrbündelwärmeübertragers invention, with radial flow guidance of the heat carrier 6. This is effected by the geometry of the baffles 7, which are formed alternately in ring or disc shape. In the figure, by way of example, the lowermost deflection plate is annular, the disc-shaped and the uppermost deflecting plate 7, which is arranged above it, again has a ring shape.

As in particular in the cross-sectional representation in FIG. 2A illustrates, is preferably the centrally arranged deflection 8 free of tubes. 1

In contrast, the illustration in FIG. 3 a tube bundle heat exchanger according to the prior art with cross-countercurrent flow of the heat carrier 6 by circular segment deflecting 7. The apparatus is fully drilled. As a result, prevails in the deflection 8 before an undefined flow, in the worst case, a pure longitudinal flow of the heat carrier outside of the tubes and thus significantly lower heat transfer coefficients over a pure Queranströmung the tubes. For example, internals 3 different geometry are required to compensate, with a correspondingly high effort in the design and installation.

The cross-sectional view in FIG. 3A illustrates that the apparatus is fully drilled.

In FIG. 4 is a further embodiment of an apparatus according to the prior art, shown with radial flow guidance of the heat carrier 6, which is effected by deflecting plates 7 which are formed alternately in ring or disc shape. As illustrated in the figure, it comes in the deflection 8 to recirculation zones and areas of longitudinal flow for the heat carrier 7 according to deteriorated heat transfer, which is compensated for example by an adapted, different design of the fixtures 3, with a correspondingly high design and installation effort.

The cross-sectional view in FIG. 4A illustrates that the apparatus is fully drilled. The area between the two dashed lines corresponds to the overlapping area of the baffles by a pure cross-flow of the tubes is guaranteed safe.

FIG. 5 shows a preferred embodiment with chambers 9, which are arranged on the outer jacket of the tube bundle heat exchanger R. The deflection regions 8 are in the chambers 9. The arrangement of the chambers 9 on the outer jacket of the tube bundle heat exchanger R is in the cross-sectional views in the FIGS. 5A and 5B especially clear.

FIG. 6 shows another variant of in FIG. 5 shown apparatus, but with DC control of polymer solution 4 and heat transfer. 6

FIG. 7 shows a further variant of the in the Figures 5 and 6 apparatus shown, however, the multi-zone, exemplified two-tone, that is with two circuits for the heat transfer medium 6, is equipped.

The FIG. 8 shows another variant of in FIG. 2 shown Radialstromapparates, but with DC control of polymer solution 4 and heat transfer. 6

In the FIGS. 9A to 9B preferred constructive designs for hoods are shown, which limit the tube bundle heat exchanger R at both ends: accordingly Figure 9A a central displacer is provided in FIG. 9B variant shown, the hood is plate-shaped or in the in FIG. 9C illustrated variant in a pipe shape.

A further preferred embodiment of the tube bundle heat exchanger R limiting hood areas is in FIG. 10 illustrated: In the hoods dummy bodies are provided in the poorly flowed hood areas.

Figure 11A schematically shows the configuration of openings 12 in the annular channels 11, which are rectangular in the illustrated variant, with decreasing size of the openings in the flow direction.

Another variant of openings 12 in the annular channels 11 is in FIG. 11B shown. In this embodiment, the openings 12 are circular.

embodiment

In a double-jacket test tube with an outer diameter of 17.8 mm and a wall thickness of 1.5 mm were by varying the heat transfer Umlaufmenge (Marlotherm® heat transfer oil), the operating conditions of good heat transfer, corresponding to a transverse inflow of the tubes with the heat carrier, that is one Heat transfer coefficient of about 1000 W / m ² / K and compared for a longitudinal flow, with a poor heat transfer coefficient, of about 200 W / m ² / K, readjusted. The jacketed test tube had an installation length of 300 mm. The temperature of the Marlotherm® thermal oil was 300 ° C when entering the jacket and the inlet temperature of the polystyrene solution from which the residual monomers styrene and ethylbenzene should be separated by relaxation, 160 ° C.

The test results are summarized in the table below.

As can be seen from the table below, were at a heat transfer coefficient of 200 W / m ² / K, corresponding to a longitudinal flow of the tube (Experiment No. V1, for comparison) higher residual concentrations of the monomers styrene and ethylbenzene in comparison to the experiments with good heat transfer coefficient, according to a cross-flow or predominant cross-flow (experiments E1 or E2 or according to the invention). Experiment no. Heat transfer coefficient [W / m ² / K] Temperature at the place of relaxation [° C] ^c styrene [ppm] ^c ethylbenzene [ppm] V1 200 203.5 442 499 E1 600 211.3 377 423 E2 1000 213.1 363 407

LIST OF REFERENCE NUMBERS

R

Shell and tube heat exchanger

1

Tube

2

tube sheet

3

installation

4

polymer solution

5

Mantle space around the pipes

6

heat transfer

7

baffles

8th

deflection

9

Chambers on the outer jacket

10

Perforations in the outer jacket

11

annular channel

12

Openings in the annular channel

S1-S4

column

Claims (23)

1. A shell-and-tube heat exchanger (R) for removing dissolved materials from a polymer solution (4) by degassing, which comprises a bundle of parallel vertical tubes (1) which are fixed at each end in a tube plate (2), with the polymer solution (4) flowing through the tubes (1), and a space (5) within the shell around the tubes (1) through which a liquid heat transfer medium (6) flows, with deflection plates (7) in the space (5) within the shell which are each arranged in cross-sectional planes of the shell-and-tube heat exchanger (R) and each leave a deflection region (8) for the heat transfer medium (6) free, with no tubes (1) being located in the deflection regions (8); wherein each tube (1) is provided with an internal which constructs the free open cross section through the tube and all internals (3) have an identical construction and also the internals (3) are fixed into the tube plate (2) by means of a threaded connection and the weld points of the tubes (1) are located below the threaded connection for the internals (3) and the internals (3) have an opening which goes right through the middle of the internals (3) and can be used for inserting a polygon key for screwing the internals into the tube plate (2) by means of a polygon key and for introducing the polymer solution (4) after removing the polygon key.
2. The shell-and-tube heat exchanger (R) according to claim 1, wherein the deflection plates (8) which are left free for the heat transfer medium (6) by the deflection plates (7) are formed within the space (5) within the shell of the shell-and-tube heat exchanger (R).
3. The shell-and-tube heat exchanger (R) according to claim 2, wherein the deflection plates (6) have the shape of segments of a circle which alternately leave deflection regions (8) free for the heat transfer medium (6) at the interior wall of the shell-and-tube heat exchanger (R).
4. The shell-and-tube heat exchanger (R) according to claim 2, wherein the deflection plates (7) alternately have an annular shape or a disk shape so that the deflection plates (7) having an annular shape leave deflection regions (8) located centrally in the shell-and-tube heat exchanger (R) free and the disk-shaped deflection plates (7) leave deflection regions (8) located at the interior wall of the shell-and-tube heat exchanger (R) free.
5. The shell-and-tube heat exchanger (R) according to any of claims 1 to 4, wherein the deflection regions (8) which are left free by the deflection plates (7) in each case take up from 5 to 20%, preferably from 8 to 14%, of the total cross-sectional area of the shell-and-tube heat exchanger (R).
6. The shell-and-tube heat exchanger (R) according to claim 1 to 3 or 5, wherein the outer wall of the shell-and-tube heat exchanger (R) is provided with one or more chambers (9) through which the heat transfer medium (6) circulates via perforations (10) in the outer wall of the shell-and-tube heat exchanger (R) and the deflection regions (8) which are left free for the heat transfer medium (6) by the deflection plates (7) are located in the chambers (9).
7. The shell-and-tube heat exchanger (R) according to any of claims 1 to 6, wherein the heat transfer medium (6) is introduced into or discharged from the space (4) within the shell in each case via a ring channel or part ring channel (11), with the ring channel or part ring channel (11) having openings (12) whose free open area decreases in the flow direction of the heat transfer medium (6) .
8. The shell-and-tube heat exchanger (R) according to any of claims 1 to 7, wherein the heat transfer coefficient on the heat transfer medium side is from 500 to 2000 W/m²/K, preferably from 800 to 1200 W/m²/K.
9. The shell-and-tube heat exchanger (R) according to any of claims 1 to 8, wherein the heat transfer medium (6) is liquid, preferably a heat transfer oil.
10. The shell-and-tube heat exchanger (R) according to any of claims 1 to 9, wherein the bundle of parallel vertical tubes (1) comprises from 100 to 10 000 tubes (1), preferably from 450 to 3500 tubes (1).
11. The shell-and-tube heat exchanger (R) according to any of claims 1 to 10, wherein the tubes (1) have a length of from 1.0 to 6.0 m, preferably from 1.2 to 2.0 m.
12. The shell-and-tube heat exchanger (R) according to any of claims 1 to 11, wherein the internal diameter of the tubes (1) is from 10 to 25 mm, preferably from 13 to 18 mm.
13. The shell-and-tube heat exchanger (R) according to any of claims 1 to 12, wherein the thickness of the deflection plates (7) is from 6 to 30 mm, preferably from 8 to 16 mm.
14. The shell-and-tube heat exchanger (R) according to any of claims 1 to 13, wherein the upper tube plate (2) is significantly thicker than the lower tube plate (2), in particular five times as thick, preferably so that the upper tube plate (2) is 150 mm thick and the lower tube plate (2) is 30 mm thick.
15. The shell-and-tube heat exchanger (R) according to any of claims 1 to 14, wherein venting holes for the heat transfer medium (6) are provided in the upper tube plate (2) or just below this, with a pipe leading from these holes to an equalization reservoir or a collection vessel.
16. The shell-and-tube heat exchanger (R) according to any of claims 1 to 15, wherein an emptying system for the heat transfer medium (6) via the lower tube plate (2) or via a hole in the wall of the shell-and-tube heat exchanger (R) is provided.
17. The shell-and-tube heat exchanger (R) according to any of claims 1 to 16, wherein gaps having a gap width in the range from 0.1 to 0.4 mm, preferably in the range from 0.14 to 0.25 mm, are present between the tubes (1) and the deflection plates (7).
18. The shell-and-tube heat exchanger (R) according to any of claims 1 to 17, wherein the deflection plates (7) seal against the wall of the shell-and-tube heat exchanger.
19. The shell-and-tube heat exchanger (R) according to any of claims 1 to 18, wherein a compensator for thermal expansion is provided in the shell of the shell-and-tube heat exchanger.
20. The shell-and-tube heat exchanger (R) according to any of claims 1 to 19, wherein the shell-and-tube heat exchanger (R) has two or more zones so that two or more separate circuits are provided for the heat transfer medium (6).
21. The shell-and-tube heat exchanger (R) according to any of claims 1 to 20, wherein the distance between the deflection plates (7) is matched to the degassing process in the tubes.
22. A continuous process for removing dissolved materials from a polymer solution (4) by degassing in a shell-and-tube heat exchanger (R) according to any of claims 1 to 21, which comprises passing the polymer solution (4) from the top downward through the tubes (1) of the shell-and-tube heat exchanger (R) and conveying the heat transfer medium (6) in cross-countercurrent or in cross-cocurrent to the polymer solution (4).
23. The use of the shell-and-tube heat exchanger (R) according to any of claims 1 to 21 or of the process according to claim 22 for degassing polystyrene or ABS.

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