ROTATING-SCREW DRYING REACTOR

Abstract

The present disclosure relates to a rotating-screw drying reactor for filtering and drying a fluid-containing material, and to a method for continuously filtering and drying a fluid-containing material by means of the rotating-screw drying reactor.

Claims

1. A screw conveyor drying reactor, wherein the screw conveyor drying reactor has at least a first screw conveyor housing and at least one outer vacuum housing that at least partially surrounds the first screw conveyor housing, wherein the first screw conveyor housing has at least one housing wall, wherein the housing wall has at least one gas- and liquid-permeable but solid-impermeable wall section, wherein the vacuum housing is arranged at least below the gas- and liquid-permeable but solid-impermeable wall section and receives gas and liquid passing through the permeable wall section, wherein a conveying screw extends into the first screw conveyor housing and is mounted at least at one end of the housing, wherein the conveying screw is connected to a drive motor to form a continuous rotary connection, wherein the first screw conveyor housing has at least one inlet port for a fluid-comprising material, and at least one outlet opening for removal of particles from which fluid has been extracted, wherein the conveying screw extends into the first screw conveyor housing in such a way that the material is transported from the inlet port to the outlet opening, and wherein the conveying screw has screw flights, wherein the vacuum housing is sealed off with respect to the first screw conveyor housing for the purpose of applying a vacuum, wherein the vacuum housing has at least one connection port for applying a vacuum and for discharging fluid which penetrates into the vacuum housing through the gas- and liquid-permeable wall section of the screw conveyor housing.

2. The screw conveyor drying reactor as claimed in claim 1, wherein the screw flights are spaced apart in a regular, varying manner or in an irregular manner.

3. The screw conveyor drying reactor as claimed in claim 1, wherein the screw flights are formed from a material selected from the group comprising polytetrafluoroethylene, aluminum and/or stainless steel.

4. The screw conveyor drying reactor as claimed in claim 1, wherein the first screw conveyor housing additionally has at least one washing solution port for introducing a washing solution into the first screw conveyor housing for washing the material.

5. The screw conveyor drying reactor as claimed in claim 1, wherein the permeable wall section has a filter material having an average pore size in the range from ≥1 μm to ≤500 μm, the permeable wall section is at least partially in the form of a glass frit and/or metal filter.

6. The screw conveyor drying reactor as claimed in claim 1, wherein at least one wall of a screw conveyor housing has at least one heat source.

7. The screw conveyor drying reactor as claimed in claim 1, wherein the first screw conveyor housing is of tubular form.

8. The screw conveyor drying reactor as claimed in claim 1, wherein the conveying screw has a shaft.

9. The screw conveyor drying reactor as claimed in claim 8, wherein at least the first screw conveyor housing has a bearing for receiving the shaft at the start of the housing.

10. The screw conveyor drying reactor as claimed in claim 1, wherein a gap size between a screw helix and the screw conveyor housing amounts to ≥0.02 mm and ≤5 mm.

11. The screw conveyor drying reactor as claimed in claim 1, wherein at least one drying housing adjoins the end of the screw conveyor housing, wherein the screw conveyor housing is connected to the drying housing preferably via a flange connection.

12. The screw conveyor drying reactor as claimed in claim 11, wherein the drying housing has at least one inlet port for gas and at least one outlet opening for gas, wherein the inflowing gas has a temperature that is higher than the temperature of the fluid-comprising material in the screw conveyor housing, of ≥30° C. and ≤100° C.

13. The screw conveyor drying reactor as claimed in claim 11, wherein a lock is arranged between the first screw conveyor housing and the adjoining drying housing, wherein the lock is a rotary feeder.

14. The screw conveyor drying reactor as claimed in claim 1, wherein a length of the first screw conveyor housing amounts to ≥5 cm and ≤150 cm.

15. The screw conveyor drying reactor as claimed in claim 1, wherein an internal volume of the first screw conveyor housing amounts to ≥3 cm.sup.3 and ≤3000 cm.sup.3.

16. The screw conveyor drying reactor as claimed in claim 11, wherein the drying housing has a transport device for transporting the material from the inlet opening of the drying housing to the outlet of the drying housing, wherein the transport device is preferably a conveyor belt or more preferably a conveying screw.

17. The screw conveyor drying reactor as claimed in claim 16, wherein the conveying screw extends from the start of the housing of the first screw conveyor housing to the outlet opening of the first screw conveyor housing; or wherein the conveying screw extends from the start of the housing of the first screw conveyor housing to the outlet of the drying housing.

18. A process for the continuous filtration and drying of a material that comprises a fluid, by means of a screw conveyor drying reactor as claimed in claim 1, wherein the material is present in the form of a dispersion or suspension, and forms solid particles as a result of the extraction of the fluid, comprising the steps of: adding the fluid-comprising material into the inlet port, wherein the fluid-comprising material is transported through the screw conveyor housing by means of the conveying screw, applying a vacuum to the vacuum housing, discharging the fluid from the material through the gas- and liquid-permeable but solid-impermeable wall section of the screw conveyor housing into the vacuum housing, optionally one or more steps of washing the material by adding a solvent, transporting the solid particles, formed as a result of the discharging of the fluid, through the screw conveyor housing to the outlet opening by means of the conveying screw.

19. The process for continuous filtration and drying as claimed in claim 18, wherein a shaft of the conveying screw is rotated by the drive motor at a speed of ≥0.1 rpm and ≤100 rpm, wherein the shaft is rotated at a constant speed.

20. The process for continuous filtration and drying as claimed in claim 18, wherein the material is transported by means of conveying screw without compression and/or pressing of the material.

21. The process for continuous filtration and drying as claimed in claim 18, wherein the screw conveyor speed is ≥0.02 cm/min and ≤500 cm/min.

22. The process for continuous filtration and drying as claimed in claim 18, wherein the pressure applied to the vacuum housing amounts to ≥1 kPa and ≤500 kPa.

23. The process for continuous filtration and drying as claimed in claim 18, wherein the separated fluid is removed from the vacuum housing, evaporated down and then resupplied to the screw conveyor drying reactor.

24. The process for continuous filtration and drying as claimed in claim 18, wherein the solid particles are subjected to at least one further washing step and/or at least one further drying step.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0060] The subject matter of the present invention is additionally elucidated in more detail on the basis of the following figures.

[0061] FIG. 1 shows a screw conveyor drying reactor according to an embodiment;

[0062] FIG. 2 shows a screw conveyor drying reactor according to an embodiment with a washing solution port;

[0063] FIG. 3 shows a screw conveyor drying reactor according to an embodiment with an adjoining drying housing;

[0064] FIG. 4 shows the mass-based cumulative distribution of the L-alanine particles before and after the screw conveyor drying reactor;

[0065] FIG. 5 shows the mass-based distribution density of the L-alanine particles before and after the screw conveyor drying reactor;

[0066] FIG. 6 shows the mass-based cumulative distribution of the paracetamol particles before and after the screw conveyor drying reactor; and

[0067] FIG. 7 shows the mass-based distribution density of the paracetamol particles before and after the screw conveyor drying reactor.

DETAILED DESCRIPTION

[0068] FIG. 1 shows a screw conveyor drying reactor 1 according to an embodiment, wherein the screw conveyor drying reactor 1 has at least a first screw conveyor housing 2 and at least one outer vacuum housing 3 that at least partially surrounds the first screw conveyor housing 2, wherein the first screw conveyor housing 2 has at least one housing wall 4, wherein this housing wall 4 has at least one gas- and liquid-permeable but solid-impermeable wall section 5, wherein the vacuum housing 3 is arranged at least below the gas- and liquid-permeable but solid-impermeable wall section 5 and receives gas and liquid passing through the permeable wall section 5, wherein a conveying screw 6 extends into the first screw conveyor housing 2 and is mounted by means of a bearing 7 at least at one end of the housing, wherein the conveying screw 6 is connected to a drive motor 8 to form a continuous rotary connection, wherein the first screw conveyor housing 2 has at least one inlet port 9 for a fluid-comprising material 14a, wherein the material 14 is preferably present in the form of a dispersion or suspension, and at least one outlet opening 10 for removal of the material 14b from which fluid has been extracted, this material being present in the form of particles, wherein the conveying screw 6 extends into the first screw conveyor housing in such a way that the material is transported from the inlet port 9 to the outlet opening 10, and wherein the conveying screw 6 has screw flights 11, wherein the vacuum housing 3 is sealed off with respect to the first screw conveyor housing 2 for the purpose of applying a vacuum, wherein the vacuum housing 3 has at least one connection port 12 for applying a vacuum and for discharging fluid which penetrates into the vacuum housing 3 through the gas- and liquid-permeable wall section 5 of the screw conveyor housing 2.

[0069] FIG. 2 shows a screw conveyor drying reactor 1 according to the invention, wherein the screw conveyor drying reactor 1 has at least a first screw conveyor housing 2 and at least one outer vacuum housing 3 that at least partially surrounds the first screw conveyor housing 2, wherein the first screw conveyor housing 2 has at least one housing wall 4, wherein this housing wall 4 has at least one gas- and liquid-permeable but solid-impermeable wall section 5, wherein the vacuum housing 3 is arranged at least below the gas- and liquid-permeable but solid-impermeable wall section 5 and receives gas and liquid passing through the permeable wall section 5, wherein a conveying screw 6 extends into the first screw conveyor housing 2 and is mounted by means of a bearing 7 at least at one end of the housing, wherein the conveying screw 6 is connected to a drive motor 8 to form a continuous rotary connection, wherein the first screw conveyor housing 2 has at least one inlet port 9 for a fluid-comprising material 14a, and at least one outlet opening 10 for removal of the particles 14b from which fluid has been extracted, wherein the conveying screw 6 extends into the first screw conveyor housing in such a way that the material is transported from the inlet port 9 to the outlet opening 10, and wherein the conveying screw 6 has screw flights 11, wherein the vacuum housing 3 is sealed off with respect to the first screw conveyor housing 2 for the purpose of applying a vacuum, wherein the vacuum housing 3 has at least one connection port 12 for applying a vacuum and for discharging fluid which penetrates into the vacuum housing 3 through the gas- and liquid-permeable wall section 5 of the screw conveyor housing 2. The screw conveyor housing 2 may additionally have at least one washing solution port 13 for introducing a washing solution into the first screw conveyor housing 2 for washing the material 14. At least one wall of the screw conveyor housing 2 may for example have at least one heat source 15. The conveying screw 6 may furthermore have a shaft 16, wherein at least the first screw conveyor housing 2 has a bearing 7 for receiving the shaft 16 at the start of the housing 17.

[0070] FIG. 3 shows a screw conveyor drying reactor 1 according to an embodiment as per FIG. 2, at least one drying housing 19 adjoining the end 18 of the screw conveyor housing 2, wherein the screw conveyor housing 2 is connected to the drying housing 19 preferably via a flange connection. The drying housing 19 has at least one inlet port for gas 20 and at least one outlet opening for gas 21, wherein a lock 22 is arranged between the first screw conveyor housing 2 and the adjoining drying housing 19. The drying housing 19 has a transport device for transporting the material 14 from the inlet opening 23 of the drying housing 19 to the outlet 24 of the drying housing 19, wherein the transport device is preferably a conveyor belt (not shown) or more preferably a conveying screw 25, wherein the conveying screw 25 extends at least from the start of the housing 26 of the drying housing 19 to the outlet 24 of the drying housing 19.

[0071] The drying housing 19 and the screw conveyor drying reactor 1 may have one or more flanges 27.

[0072] The advantageous properties of the screw conveyor drying reactor with respect to the particle size distribution of L-alanine during the drying operation are described below, according to an embodiment.

TABLE-US-00001 TABLE 1 Experimental conditions Substance system L-alanine/water Solids content 5 percent by weight Suspension volume flow rate 15 ml/min n.sub.screw 5 rpm Pressure difference Δp 400 mbar Temperature 23° C. 6-fold determination

[0073] FIG. 4 shows the experimentally determined particle size distributions before (illustrated as black squares) and after (illustrated as white triangles) the screw conveyor drying reactor, shown as mass-based cumulative distribution Q.sub.3. As substance system, L-alanine was crystallized from aqueous solution. L-alanine is obtained from Evonik Industries AG with a purity of 99.7% and crystallized from 400 ml of Millipore water (0.215 g of L-alanine/g of H.sub.2O). Crystallization from 50° C. to 23° C. was effected in a 400 ml crystallizer at a cooling rate of 0.45 K/min. A solids content of 5 percent by weight results. The particle size distribution of the crystallization suspension (black squares) was recorded by dynamic image analysis (ISO 13322-2:2006(E)) and a QICPIC Lixell sensor (Sympatec GmbH, Clausthal-Zellerfeld). After being received from the screw conveyor drying reactor, the dry particles (illustrated as white triangles) are resuspended in saturated aqueous L-alanine solution (0.159 g of L-alanine/g of H.sub.2O) and determined by the same measurement method. In FIG. 4, the proportion of the total mass lying below a determined particle size D.sub.eq (equivalent diameter of the circle with the same projection surface area) is plotted on the ordinate.

[0074] FIG. 5 shows the experimentally determined particle size distributions before (illustrated as black squares) and after (illustrated as white triangles) reception from the screw conveyor dryer, shown as mass-based density distribution q.sub.3. The experimental procedure is equivalent to that in FIG. 4. In FIG. 5, the proportion of the total mass within a determined size interval based on a defined interval width is shown on the ordinate. It is thus possible to see here the probability of the particle sizes lying within a defined interval.

[0075] As emerges from FIGS. 4 and 5, the use of the screw conveyor drying reactor according to an embodiment does not have any influence on the particle size distribution of L-alanine particles.

[0076] This is supported statistically by a two-sample t-test with unequal variances, described for example in the literature by Wilhelm Kleppmann, Versuchsplanung, Produkte und Prozesse optimieren, 2013 and John A. Rice (2006), Mathematical Statistics and Data Analysis, Third Edition, Duxbury Advanced. Accordingly, the product quality is maintained virtually unchanged in terms of the particle size distribution and particle size of the crystallization material before and after drying.

[0077] The results in terms of particle size distribution and particle size of the crystallization material before and after drying by means of the screw conveyor drying reactor according to the invention were tested with a further substance system. Since the use of the screw conveyor drying reactor and the process in particular for the drying of active substances while preserving the particle size distribution and particle size may be of significance in particular for the preparation of medicines, experiments were conducted with paracetamol from ethanol, according to various embodiments.

TABLE-US-00002 TABLE 2 Experimental conditions Substance system paracetamol/ethanol Solids content 5 percent by weight Suspension volume flow rate 15 ml/min n.sub.screw 5 rpm Pressure difference Δp 200 mbar Temperature 23° C. 3-fold determination

[0078] FIG. 6 shows the experimentally determined particle size distributions before (illustrated as black squares) and after (illustrated as white triangles) reception from the screw conveyor drying reactor, shown as mass-based cumulative distribution Q.sub.3. As substance system, paracetamol was crystallized from ethanol. Paracetamol is obtained from Alfa Aesar with a purity of 98% and crystallized from 400 ml of absolute ethanol (0.255 g of paracetamol/g of ethanol). Crystallization from 35° C. to 23° C. was effected in a 400 ml crystallizer at a cooling rate of 0.45 K/min. A solids content of 5 percent by weight results. The particle size distribution of the crystallization suspension (illustrated as black squares) was recorded by dynamic image analysis (ISO 13322-2:2006(E)) and a QICPIC Lixell sensor (Sympatec GmbH, Clausthal-Zellerfeld). After being received from the screw conveyor drying reactor, the dry particles (illustrated as white triangles) are resuspended in saturated aqueous paracetamol solution (0.013 g of paracetamol/g of water) and determined by the same measurement method. In FIG. 6, the proportion of the total mass lying below a determined particle size D.sub.eq (equivalent diameter of the circle with the same projection surface area) is plotted on the ordinate.

[0079] FIG. 7 shows the experimentally determined particle size distributions before and after reception from the screw conveyor dryer, shown as mass-based density distribution q.sub.3. The experimental procedure is equivalent to that in FIG. 6. In FIG. 7, the proportion of the total mass within a determined size interval based on a defined interval width is shown on the ordinate. It is thus possible to see here the probability of the particles lying within a defined particle size interval.

[0080] As is shown by FIGS. 6 and 7, the use of the screw conveyor drying reactor according to an embodiment does not have any influence on the particle size distribution of paracetamol particles in comparison before and after drying by means of the screw conveyor drying reactor according to an embodiment. This is supported statistically by a two-sample t-test with unequal variances. Accordingly, the product quality of the crystallization material is maintained in comparison before and after the drying.

[0081] All the features and advantages, including structural details, spatial arrangements and method steps, which follow from the claims, the description and the drawing can be fundamental to the invention both on their own and in different combinations. It is to be understood that the foregoing is a description of one or more preferred exemplary embodiments of the invention.

[0082] The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art. All such other embodiments, changes, and modifications are intended to come within the scope of the appended claims.

[0083] As used in this specification and claims, the terms “for example,” “for instance,” “such as,” and “like,” and the verbs “comprising,” “having,” “including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation.