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Title:
ASSEMBLY AND METHOD FOR DRYING A PRODUCT
Document Type and Number:
WIPO Patent Application WO/2008/063059
Kind Code:
A1
Abstract:
The application relates to an assembly for drying a product, comprising at least on drying device and at least one adsorption device, in which the adsorption device is provided with regenerable adsorption material for extracting water from a gas and comprises a gas inlet and a gas outlet, and is adapted is to bring the gas into contact with the regenerable adsorption material between the gas inlet and the gas outlet, the drying device is adapted to transport the product along a drying section and comprises a first gas inlet, a second gas inlet situated at a distance from the first gas inlet, a first gas outlet, and a second gas outlet situated at a distance from the first gas outlet, in which the gas inlets and gas outlets of the drying device are arranged with respect to one another in such a manner that the gas and the product are brought into contact with one another along a first part of the drying section and a second part of the drying section, and the drying device and the adsorption device are in gas communication with one another in order to bring the gas in contact with the regenerable adsorption material before the first part of the drying section and before the second part of the drying section. The application furthermore relates to a method for drying a product, in which a gas is brought into contact with a regeneralbe adsorption material, and is subsequently alternately brought into contact with the product to be dried and regenerable adsorption material. The invention makes it possible to improve the drying process.

Inventors:
VAN BOXTEL ANTONIUS JOSEPH BER (NL)
BARTELS PAUL VINCENT (NL)
DJAENI MOHAMED (NL)
SANDERS JOHAN PIETER MARINUS (NL)
VAN STRATEN GERRIT (NL)
Application Number:
NL2007/050578
Publication Date:
May 29, 2008
Filing Date:
November 21, 2007
Export Citation:
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Assignee:
UNIV WAGENINGEN (NL)
VAN BOXTEL ANTONIUS JOSEPH BER (NL)
BARTELS PAUL VINCENT (NL)
DJAENI MOHAMED (NL)
SANDERS JOHAN PIETER MARINUS (NL)
VAN STRATEN GERRIT (NL)
International Classes:
A23L3/40; B01D53/06; B01D53/26; F26B5/04; F26B21/08
Domestic Patent References:
WO2004043574A12004-05-27
Foreign References:
US3547179A1970-12-15
US4475295A1984-10-09
US4251923A1981-02-24
EP1316770A22003-06-04
DE19757537A11999-07-08
DE102004013447A12005-09-29
EP0740956A21996-11-06
EP0095999A11983-12-07
Attorney, Agent or Firm:
VAN WESTENBRUGGE, Andries (LS Den Haag, NL)
Download PDF:
Claims:

CLAIMS

1. An assembly for drying a product, comprising at least one drying device and at least one adsorption device, in which: the adsorption device is provided with regenerable adsorption material for extracting water from a gas and comprises a gas inlet and a gas outlet, and is adapted to bring the gas into contact with the regenerable adsorption material between the gas inlet and the gas outlet; the drying device is adapted to transport the product along a drying section and comprises a first gas inlet, a second gas inlet situated at a distance from the first gas inlet, a first gas outlet, and a second gas outlet situated at a distance from the first gas outlet, in which the gas inlets and gas outlets of the drying device are arranged with respect to one another to bring the gas and the product into contact with one another along a first part of the drying section and a second part of the drying section, and the drying device and the adsorption device are in gas communication with one another in order to bring the gas in contact with the regenerable adsorption material before the first part of the drying section and in order to transport the gas out of the drying device and bring it into contact again with regenerable adsorption material before the second part of the drying section and to pass it into the drying device in the second part of the drying section.

2. The assembly as claimed in claim 1, in which the gas outlet of the adsorption device is connected to the first and second gas inlet of the drying device.

3. The assembly as claimed in claim 2, in which the first gas outlet of the drying device is connected to the gas inlet of the adsorption device.

4. The assembly as claimed in one of the preceding claims, in which the drying device comprises at least two drying chambers and the first gas inlet and first gas outlet are connected to the first drying chamber and the second gas inlet and second gas outlet are connected to the second drying chamber, and the drying section through the first

drying chamber forms the first part of the drying section and the drying section through the second drying chamber the second part of the drying section.

5. The assembly as claimed in one of the preceding claims, in which the adsorption device furthermore comprises a second gas inlet which is in gas communication with the first gas outlet of the drying device.

6. The assembly as claimed in one of the preceding claims, in which the adsorption device furthermore comprises a second gas outlet which is in gas communication with the second gas inlet of the drying device.

7. The assembly as claimed in claims 5 and 6, in which the first gas inlet and first gas outlet define a first flow section along regenerable absorption material, and the second gas inlet and second gas outlet define a second flow section, separate therefrom, along regenerable absorption material.

8. The assembly as claimed in one of the preceding claims, furthermore comprising a regeneration device for regenerating regenerable adsorption material from the adsorption device.

9. The assembly as claimed in one of the preceding claims, in which the regeneration device comprises a gas inlet and a gas outlet for a regenerating gas and is adapted to bring the regenerable adsorption material and the regenerating gas in contact with one another.

10. The assembly as claimed in claim 9, in which the regeneration device furthermore comprises an inlet and an outlet for the regenerable adsorption material.

11. The assembly as claimed in claim 10, in which the adsorption device furthermore comprises an inlet and outlet for the regenerable adsorption material, the inlet for the regenerable adsorption material being connected to the outlet for the regenerable adsorption material of the regeneration device and the outlet for the regenerable adsorption material being connected to the inlet for the regenerable adsorption material

of the regeneration device, and the assembly is adapted for transferring adsorption material to be regenerated from the adsorption device to the regeneration device and for transferring regenerated adsorption material from the regeneration device to the adsorption device.

12. The assembly as claimed in one of the preceding claims, in which a first and a second inlet for the gas situated at a distance from the first inlet, and a first outlet and a second outlet for the gas situated at a distance from the first outlet, with a first container for the regenerable adsorption material between the first inlet and the first outlet and a first gas flow duct between the first inlet and first outlet for bringing gas in contact with regenerable adsorption material, with a second container for the regenerable adsorption material between the second inlet and the second outlet and a second gas flow duct between the second inlet and second outlet for bringing gas in contact with regenerable adsorption material.

13. The assembly as claimed in one of the preceding claims, furthermore comprising a compressor, operationally connected to the gas outlet of the regeneration device for compressing regenerating gas.

14. The assembly as claimed in claim 9 in combination with one of the preceding claims, furthermore comprising a compressor, operationally connected to the gas outlet of the regeneration device for compressing regenerating gas.

15. The assembly as claimed in one of the preceding claims, furthermore comprising a compressor, operationally connected to the gas outlet of a regeneration device for regenerating the regenerable adsorption material, for compressing regenerating gas, furthermore comprising a further drying device comprising a third drying section in which the product is brought into contact with a gas, comprising a gas inlet which is in heat-exchanging contact with an outlet of the compressor and an inlet for product to be dried which is operationally connected to an outlet for the product of the drying device.

16. The assembly as claimed in one of the preceding claims, furthermore comprising a compressor, operationally connected to the gas outlet of a regeneration device for

regenerating the regenerable material, for compressing regenerating gas, in which the drying device furthermore comprises an additional gas inlet which is in heat- exchanging contact with an outlet of the compressor and which is arranged in order to bring the product and gas from the additional gas inlet in contact over a third part of the drying section outside the first part and second part of the drying section.

17. An assembly for drying a product, comprising at least two drying devices and at least one adsorption device, in which: the adsorption device is provided with regenerable adsorption material for extracting water from a gas and comprises a gas inlet and a gas outlet, and is adapted to bring the gas in contact with regenerable adsorption material between the gas inlet and the gas outlet; the drying devices are adapted to transport the product along a drying section and each comprise a gas inlet and a gas outlet, in which the gas inlet and gas outlet are arranged with respect to one another in such a manner that the gas and the product are brought into contact with one another along a drying section, and the drying device and the adsorption device are in gas communication with one another in order to bring the gas in contact with regenerable adsorption material before the drying section of the first drying device and to bring the gas from the first drying device in contact with regenerable absorption material before the drying section of the second drying device before it is passed onto the second drying device.

18. An assembly for drying a product, comprising a drying device, an adsorption device and a compressor, in which: the adsorption device can be provided with regenerable adsorption material for extracting water vapor from a gas, and comprises a gas inlet and a gas outlet, and is adapted for bringing the gas into contact with regenerable adsorption material between the gas inlet and the gas outlet; the drying device is adapted to transport the product along a drying section and comprises a gas inlet and a gas outlet, the gas inlet and gas outlet being arranged with respect to one another in such a manner that the gas and the product are brought into contact with one another along a drying section;

the drying device and the adsorption device are in gas communication with one another to bring the gas in contact with the regenerable adsorption material before the drying section and in the drying section, and the compressor is operationally connected to and in gas communication with an outlet of the drying device in order to increase the gas pressure of the gas, and the gas from the compressor is brought into heat-exchanging contact with gas which is transported to the inlet of the adsorption device.

19. An assembly for drying a product, comprising a drying device, an adsorption device, a regeneration device and a compressor, in which: the adsorption device can be provided with regenerable adsorption material for extracting water vapor from a gas, and comprises a gas inlet and a gas outlet, and is adapted for bringing the gas in contact with regenerable adsorption material between the gas inlet and the gas outlet; the drying device is adapted to transport the product along a drying section and comprises a gas inlet and a gas outlet, the gas inlet and gas outlet being arranged with respect to one another In such a manner that the gas and the product are brought into contact with one another along a drying section; the drying device and the adsorption device are in gas communication with one another to bring the gas in contact with the regenerable adsorption material before the drying section and in the drying section; the regeneration device and the adsorption device are in contact with one another in such a manner that regenerable adsorption material is exchanged, and the compressor is operationally connected to and in gas communication with an outlet of the regeneration device for increasing the gas pressure of the gas, and the gas from the compressor is brought into heat-exchanging contact with gas which is transported to the inlet of the adsorption device or to the inlet of the regeneration device.

20. An assembly for drying a product, comprising several drying steps of the product, in which, between the drying steps, a gas is brought into contact with a regenerable adsorption material, and the gas, after use, exchanges heat with a further gas which is brought into contact with the regenerable adsorption material for regenerating the adsorption material.

21. The assembly as claimed in one of the preceding claims, furthermore provided with a control device which is operationally connected to a meter for measuring the moisture content of the product and/or the temperature of the gas in the drying device, S and in which the control device is provided with a preset value for the moisture content of the product and/or the temperature of the gas, and the control device, on the basis of the comparison of the preset and measured values, controls the temperature of the gas which is introduced into the drying device.

0 22. A method for drying a product, comprising the steps of: passing a product along a drying section, bringing a gas in contact with a regenerable adsorption material for extracting water from the gas, subsequently bringing the gas into contact with the product along a part of the drying 5 section, then again bringing the gas in contact with regenerable adsorption material for extracting water from the gas, and subsequently again bringing the gas into contact with the product along a part of the drying section. 0

23. The method as claimed in claim 22, in which the gas passes through a gas-drying section along regenerable adsorption material, in which the gas, after having been brought into contact with the regenerable adsorption material along a first part of the gas-drying section, is brought into contact with the product over a first part of the 5 drying section, following which the gas is again brought into contact with the regenerable adsorption material along a second part of the gas-drying section, after which the gas is brought into contact with the product over a second part of the drying section.

0 24. The method as claimed in claim 23, in which the second gas-drying section is separate from the first gas-drying section.

25. The method as claimed in claim 23 of 24, in which the first drying section is separate from the second drying section.

26. A method for drying a product, in which a gas is brought into contact with a regenerable adsorption material along a gas-drying section, and the product is passed along a drying section, in which the gas is alternately brought into contact with the product along a part of the drying section, and is brought into contact with regenerable adsorption material along a part of the gas-drying section.

27. A method for drying a product, in which a gas is brought into contact with regenerable adsorption material and is subsequently brought into contact with the product to be dried and die regenerable adsorption material is regenerated, and the gas is compressed and exchanges heat with gas before it is brought into contact with the regenerable adsorption material.

28. Use of the method as claimed in one of the preceding claims for drying starch at an air temperature of approximately 50-130 degrees Celsius with an energy efficiency of 80-100%.

29. Use of the method as claimed in one of the preceding claims for drying milk powder at an air temperature of approximately 60-100 degrees Celsius with an energy efficiency of 80-100%.

30. Use of the method as claimed in one of the preceding claims for drying herbs at a temperature of approximately 30-90 degrees Celsius with an energy efficiency of 65-

100%.

31. Use of the method as claimed in one of the preceding claims for drying pharmaceutical products at a temperature of approximately 25-30 degrees Celsius with an energy efficiency of 60-100%.

32. Device provided with one or more of the characterizing features described in the attached description and/or illustrated in the attached drawings.

33. Method comprising one or more of the characterizing steps described in the accompanying description and/or illustrated in the accompanying drawings.

-o-o-o-o-o-o

Description:

Assembly and method for drying a product

Background of the invention

The invention relates to a method for drying a product, and to a assembly for drying a product, comprising a drying device through which a product can be passed, in which the product is dried by means of a gas stream which has been demoisturized using what is referred to as a regenerable adsorbent.

With a known method for drying a product, for example products for the foods and luxury foods industry and pharmaceutical industry, such as foodstuffs, medicines, herbs or other products, the product is subjected to a stream of hot air. In this case, it is also possible to dry the air in a cold state and to subsequently heat it.

Dutch patent 1,020,603 describes a method and device for drying a product in which a "regenerative adsorbent" is brought into contact with the product to be dried. In addition, a method appears to be described in which a gas stream is first passed over the "regenerative adsorbent" and then said gas stream is brought into contact with the product. However, according to the document, said method appears to be carried out in combination with the method in which the product is brought into contact with the "regenerative adsorbent". Regeneration of the adsorbent then takes place is said process by means of superheated steam. The process and in particular the energy consumption leave room for improvement. It is difficult to recover the residual energy in the steam which is released during the regeneration process in the process or the device itself.

US-3,547,179 describes a device for converting wet material into dry powder. In this case liquid material to be dried is sprayed down a drying tower which is 50-200 meters high, where it is brought into contact with a dry gas in countercurrent. As a result thereof, a powder is produced on the bottom of the drying tower. The powder is then, in a three-stage "fluidized bed", brought into contact with in each case fresh dry gas for further drying. The dry gas which is released by the "fluidized bed" is used in the

drying tower without further treatment. However, the energy efficiency of the device which is described can be improved upon.

US-3,230,689 describes a device for producing a dry gas, in which the dry gas is passed over an absorption bed, following which the released heat is used for regenerating adsorbent in a heat exchanger, referred to in said document as a regenerator. The dry gas is subsequently passed through a second absorption bed after which the dry gas is passed to a drying device. The described device has an additional absorption bed which is regenerated when the other two absorption beds are used to dry the dry gas. Furthermore, two heat exchangers Wl and W2 appear to be provided. Gas which is used to regenerate the absorption bed is first passed over the first heat exchangers (referred to as 'regenerators'), then, via a heat exchanger Wl, over the absorption bed to be regenerated, and subsequently via a heat exchanger (also referred to as 'regenerator') out of the device. Even if the device in this publication could be combined with the device from US-3,547,179, the energy efficiency leaves room for improvement.

US-4,251 ,923 describes a device for drying, for example, foods, generally liquid foods, by means of reduced pressure (vacuum). In this case, a reduced pressure is produced in a drying chamber and extracted fluid which contains water from the product to be dried is passed over an absorbent and then returned to the drying chamber. As a result of the reduced pressure, the fluid cools down and it is heated before being returned to the drying chamber. This Vacuum-drying' or 'freeze-drying' which is known per se is not suitable for every product. In addition, the energy efficiency can in this case also be improved upon.

Various publications, such as EP-95,999, WO-2004/043574, US-4,475,295 and DE- 19757537 describe a device for regenerating regenerable absorption material and returning the regenerated absorption material to a drying process in an efficient manner. EP-740,956 describes a wheel-type device for alternately regenerating regenerable absorption material and using the regenerated absorption material in a drying process.WO-2004/043574 describes what is referred to as a 'swing'-type regenerator which uses a microwave oven for regenerating the absorption material. US-4,475,295 describes a device for drying a drying gas by means of an absorbent and regenerating

the absorbent. In this case, use is made of a cylinder having various compartments in which the absorbent in the various compartments is alternately used for drying and is regenerated.

EP-1,316,770 describes a device for drying plastic material. In this case, a dry gas is recirculated and in each case passed over an absorption material and through the plastic to be dried. Even in this case, the energy in the process is not used to an optimum degree.

Summary of the invention

It is an object of the invention to provide a device and method for drying a product offering improved energy efficiency.

In addition and/or alternatively, it is an object of the invention to provide a device and method for drying a product by means of a regenerable adsorbent in which the contamination of the product by regenerable adsorbent is reduced to a minimum.

It is a further object of the invention to enable drying at relatively low temperatures in order to preserve the quality of heat-sensitive products during drying.

To this end, the invention provides an assembly for drying a product, comprising at least one drying device and at least one adsorption device.

The adsorption device is provided with regenerable adsorption material for extracting water from a gas and comprises a gas inlet and a gas outlet, and is adapted to bring the gas into contact with the regenerable adsorption material between the gas inlet and the gas outlet.

The drying device is adapted to transport the product along a drying section (traject, range) and comprises a first gas inlet, a second gas inlet situated at a distance from the first gas inlet, a first gas outlet, and a second gas outlet situated at a distance from the first gas outlet, in which the gas inlets and gas outlets of the drying device are arranged

with respect to one another in such a manner that the gas and the product are brought into contact with one another along a first part of the drying section and a second part of the drying section.

The drying device and the adsorption device are in gas communication with one another in order to bring the gas in contact with the regenerable adsorption material before the first part of the drying section and in order to transport the gas out of the drying device and bring it into contact again with the regenerable adsorption material before the second part of the drying section and to pass it into the drying device in the second part of the drying section.

The invention furthermore relates to a method for drying a product, in which a gas is brought into contact with a regenerable adsorption material, and subsequently is alternately brought into contact with the product to be dried and regenerable adsorption material. In particular, the invention relates to a method for drying a product, in which a gas is brought into contact with a regenerable adsorption material along a gas-drying section, and the product is passed along a drying section, in which the gas is alternately brought into contact with the product along part of the drying section, and is brought into contact with regenerable adsorption material along a part of the gas-drying section.

The invention furthermore relates to a method for drying a product, comprising the steps of passing a product along a drying section, bringing a gas in contact with a regenerable adsorption material for extracting water from the gas, subsequently bringing the gas into contact with the product along a part of the drying section, then again bringing the gas in contact Willi regenerable adsorption material for extracting water from the gas, and subsequently again bringing the gas into contact with the product along a part of the drying section.

It was found that by means of the device and method, it is readily possible to recover the (residual) heat of the various process steps and use it for (he drying itself and/or to use it to an optimum degree. Thus, a method or device is provided which, for example, can readily be implemented independently, that is to say does not have to be combined with, for example, combined heat and power installations or power sources other than

the device or the process. In addition, the product docs not come into contact with the regenerable adsorbent. With many products, said contact is undesirable as it is possible that a small fraction of the regenerable adsorbent remains behind in the product. The device and the method according to the invention result in very efficient and quick drying with minimal supply of energy. Characteristic of the above-described prior art is the fact that they generally relate to an efficient interaction between the adsorption and regeneration steps. The present invention relates to the possibilities of integrating the drying device and absorption device in order to achieve a higher energy efficiency.

In particular, the device is suitable for drying products which are sensitive to heat. Examples of such products are, inter alia, products from the foods and luxury foods industry, and medicines. Due to the demoisturization of the gas stream, such products can be dried at a relatively low temperature, as a result of which the degeneration of the quality is limited.

In a particular embodiment, a gas, such as air, nitrogen, carbon dioxide or helium, is used for drying.

In an embodiment, the method and device are used for drying products at a gas temperature of approximately 20-250 degrees Celsius, a medium gas temperature of approximately 30-100 degrees Celsius having been found to be particularly suitable. Particularly in the latter range, efficient drying was found to be possible.

The regenerable adsorbent or regenerable adsorption material according to the invention is a moisture/water vapor-adsorbing material which can adsorb water from a gas and retain it. The moisture can be released by means of a regenerative treatment. The regeneration usually takes place by heating of the adsorption material.

Suitable materials are adsorption materials which adsorb moisture at relatively low and medium temperatures and release moisture at relatively high temperatures, for example over 100 degrees Celsius. An example of such materials is inter alia zeolites, molecular sieves, silica gel, calcium oxide, calcium phosphate, lithium chloride and activated aluminia

Zeolites which may be used with the method and unit according to the invention are, for example, the following zeolites, which are known to those skilled in the art by their acronyms (for example from "Atlas of zeolite framework types" , Ch. Baerlocher, W.M. Meier, D.H. Olson, 2001, Elsevier Science, ISBN: 0-444-50701-9): ABW, ACO, AEI, AEL, AEN, AET, AFG, AFI, AFN, AFO, AFR, AFS, AFT, AFX, AFY, AHT, ANA, APC, APD, AST, ASV, ATN, ATO, ATS, ATT, ATV, AWO, AWW, BCT, BEA, BEC, BIK, BOG, BPH, BRE, CAN, CAS, CFI, CGF, CGS, CHA, -CHI, -CLO, CON, CZP, DAC, DDR, DFO, DFT, DOH, DON, EAB, EDI, EMT, EPI, ERI, ESV, ETR, EUO, FAU, FER, FRA, GIS, GME, GON, GOO, HEU, IFR, ISV, ITE, ITH, ITW, IWR, IWW, JBW, KFI, LAU, LEV, LIO, LOS, LOV, LTA, LTL, LTN, MAZ, MEI, MEL, MEP, MER, MFI, MFS, MON, MOR, MSO, MTF, MTN, MTT, MTW, MWW, NAB, NAT, NES, NON, NPO, OFF, OSI, OSO, -PAR, PAU, PHI, PON, RHO, -RON, RSN, RTE, RTH, RUT, RWY, SAO, SAS, SAT, SAV, SBE, SBS, SBT, SFE, SFF, SFG, SFH, SFN, SGT, SOD, SSY, STF, STI 5 STT, TER, THO, TON, TSC, UEI, UFI, UOZ, USI, VET, VFI, VNI, VSV, WEI, -WEN, YUG, ZON. Combinations of (loaded) zeolites may also be used.

Other suitable adsorbents are hormite-like clays, such as sepiolite, attapulgite, hormite, polygarskite, etc.

Zeolite 13X and zeolites of types 3A, 4A and 5A have, for example, been found to be particularly suitable.

In order to regenerate zeolites, the latter are usually exposed to a temperature between approximately 100-300 degrees Celsius. In itself, the concept of regeneration of the regenerable adsorption materials and of zeolites in particular, and the relevant process parameters and the like are well-known to those skilled in the art, and will not be discussed in any more detail here.

In this document, the energy efficiency of the drying process is defined as:

Heat of evaporation Energy efficiency = 100 % x

Energy used

In the case of standard processes and methods in which a product is brought into contact with a gas stream this energy efficiency is usually between 45-65 % for a drying process at 30-90 degrees Celsius.

Incidentally, with a device and method according to the invention, use may be made of devices as described above in the background of the invention in order to alternately regenerate absorption material and make it available for treating the gas which is used for drying.

The use of a gas stream which has been in contact with the regenerable adsorbent, and the hot air which is released after regeneration make it possible to by means of heat recovery at various locations in the method, for example by using heat exchangers, this energy efficiency can often be increased still further.

The device and method according to the invention are suitable for use in a countercurrent, cocurrent or crosscurrent arrangement. In particular when a product and the gas are brought into contact with one another in countercurrent with respect to one another, a more efficient drying process is possible when applying the invention.

A belt drier, fluidized bed drier or rotating drier, possibly even in combination, are particularly suitable as (part of) a drying device according to the invention.

In an embodiment of the device and method according to the invention, heat energy is recovered at various locations in the device and in various steps of the method by means of heat exchangers. In an embodiment, heat exchangers are inter alia switched on the basis of pinch technology.

In an embodiment of the method and device, the gas is compressed to a pressure of approximately 1.5-5 bar. In this case, it is preferable if the gas stream from the regeneration device is compressed.

In an embodiment of the assembly, the gas outlet of the adsorption device is connected to the first and second gas inlet of the drying device.

In an embodiment of the assembly, the first gas outlet of the drying device is connected to the gas inlet of the adsorption device.

In an embodiment of the assembly, the drying device comprises at least two drying chambers and the first gas inlet and first gas outlet are connected to the first drying chamber and the second gas inlet and second gas outlet are connected to the second drying chamber, and the drying section through the first drying chamber forms the first part of the drying section and the drying section through the second drying chamber the second part of the drying section.

In an embodiment of the assembly, the adsorption device furthermore comprises a second gas inlet which is in gas communication with the first gas outlet of the drying device.

In an embodiment of the assembly, the adsorption device furthermore comprises a second gas outlet which is in gas communication with the second gas inlet of the drying device.

In an embodiment of the assembly, the de first gas inlet and first gas outlet define a first flow section along regenerable absorption material, and the second gas inlet and second gas outlet define a second flow section, separate therefrom, along regenerable absorption material. This makes it possible to use released heat energy. If desired, it is also possible to pass the regenerable absorption material along a section, opposite to or in the same direction as the direction of the gas.

In an embodiment, the assembly furthermore comprises a regeneration device for regenerating regenerable adsorption material from the adsorption device.

In an embodiment of the assembly, the regeneration device comprises a gas inlet and a gas outlet for a regenerating gas and is adapted to bring the regenerable adsorption material and the regenerating gas in contact with one another.

In an embodiment thereof, the regeneration device furthermore comprises an inlet and an outlet for the regenerable adsorption material.

In an embodiment thereof, the adsorption device furthermore comprises an inlet and outlet for the regenerable adsorption material, the inlet for the regenerable adsorption material being connected to the outlet for the regenerable adsorption material of the regeneration device and the outlet for the regenerable adsorption material being connected to the inlet for the regenerable adsorption material of the regeneration device, and the assembly is adapted for transferring adsorption material to be regenerated from the adsorption device to the regeneration device and for transferring regenerated adsorption material from the regeneration device to the adsorption device.

In an embodiment, the assembly comprises a first and a second inlet for the gas situated at a distance from the first inlet, and a first outlet and a second outlet for the gas situated at a distance from the first outlet, with a first container for the regenerable adsorption material between the first inlet and the first outlet and a first gas flow duct between the first inlet and first outlet for bringing gas in contact with regenerable adsorption material, with a second container for the regenerable adsorption material between the second inlet and the second outlet and a second gas flow duct between the second inlet and second outlet for bringing gas in contact with regenerable adsorption material.

In an embodiment, the assembly furthermore comprises a compressor, operationally connected to the gas outlet of the regeneration device for compressing regenerating gas.

In an embodiment in which the assembly comprises the regeneration device, the assembly furthermore comprises a compressor, operationally connected to the gas outlet of the regeneration device for compressing regenerating gas.

5 In an embodiment, the assembly furthermore comprises a compressor, operationally connected to the gas outlet of a regeneration device for regenerating the regenerable adsorption material, for compressing regenerating gas, furthermore comprising a further drying device comprising a third drying section in which the product is brought into contact with a gas, comprising a gas inlet which is in heat-exchanging contact with 0 an outlet of the compressor and an inlet for the product to be dried which is operationally connected to an outlet for the product of the drying device.

In an embodiment, the assembly furthermore comprises a compressor, operationally connected to the gas outlet of a regeneration device for regenerating the regenerable S material, for compressing regenerating gas, in which the drying device furthermore comprises an additional gas inlet which is in heat-exchanging contact with an outlet of the compressor and which is arranged in order to bring the product and gas from the additional gas inlet in contact over a third part of the drying section outside the first part and second part of the drying section. 0

The invention furthermore relates to an assembly for drying a product, comprising at least two drying devices and at least one adsorption device, in which: the adsorption device is provided with regenerable adsorption material for extracting water from a gas and comprises a gas inlet and a gas outlet, and is adapted to bring the 5 gas in contact with regenerable adsorption material between the gas inlet and the gas outlet; the drying devices are adapted to transport the product along a drying section and each comprise a gas inlet and a gas outlet, in which the gas inlet and gas outlet are arranged with respect to one another in such a manner that the gas and the product are brought 0 into contact with one another along a drying section, and the drying device and the adsorption device are in gas communication with one another in order to bring the gas in contact with the regenerable adsorption material before the drying section of the first drying device and before the drying section of the second

drying device. In particular, the drying device and the adsorption device are in gas communication with one another in order to bring the gas in contact with regenerable adsorption material before the drying section of the first drying device and to bring the gas from the first drying device in contact with regenerable adsorption material before the drying section of the second drying device before it is passed onto the second drying device.

This alternative embodiment offers the abovementioned advantages.

The invention furthermore relates to an assembly for drying a product, comprising a drying device, an adsorption device and a compressor, in which: the adsorption device can be provided with regenerable adsorption material for extracting water vapor from a gas, and comprises a gas inlet and a gas outlet, and is adapted for bringing the gas into contact with regenerable adsorption material between the gas inlet and the gas outlet; the drying device is adapted to transport the product along a drying section and comprises a gas inlet and a gas outlet, the gas inlet and gas outlet being arranged with respect to one another in such a manner that the gas and the product are brought into contact with one another along a drying section; the drying device and the adsorption device are in gas communication with one another to bring the gas in contact with the regenerable adsorption material before the drying section and in the drying section, and the compressor is operationally connected to and in gas communication with an outlet of the drying device in order to increase the gas pressure of the gas, and the gas from the compressor is brought into heat-exchanging contact with gas which is transported to the inlet of the adsorption device.

The advantages which have been mentioned have been found to increase further by positioning the compressor at said location in the assembly.

The invention furthermore relates to an assembly for drying a product, comprising a drying device, an adsorption device, a regeneration device and a compressor, in which:

the adsorption device can be provided with regenerable adsorption material for extracting water vapor from a gas, and comprises a gas inlet and a gas outlet, and is adapted for bringing the gas in contact with regenerable adsorption material between the gas inlet and the gas outlet; the drying device is adapted to transport the product along a drying section and comprises a gas inlet and a gas outlet, the gas inlet and gas outlet being arranged with respect to one another in such a manner that the gas and the product are brought into contact with one another along a drying section; the drying device and the adsorption device are in gas communication with one another to bring the gas in contact with the regenerable adsorption material before the drying section and in the drying section; the regeneration device and the adsorption device are in contact with one another in such a manner that regenerable adsorption material is exchanged, and the compressor is operationally connected to and in gas communication with an outlet of the regeneration device for increasing the gas pressure of the gas, and the gas from the compressor is brought into heat-exchanging contact with gas which is transported to the inlet of the adsorption device or to the inlet of the regeneration device.

The invention furthermore relates to an assembly for drying a product, comprising several drying steps, in which, between the drying steps, a gas is brought into contact with a regenerable adsorption material, and the gas, after use, exchanges heat with a further gas which is brought into contact with the regenerable adsorption material for regenerating the adsorption material.

It has been found that this makes it possible to achieve a very high energy efficiency during drying, in particular at relatively low temperatures, as has already been described above.

The invention furthermore relates to a method for drying a product, in which a gas is brought into contact with a regenerable adsorption material for extracting water from the gas, the gas is then brought into contact with the product, the gas is then again brought into contact with the regenerable adsorption material in order to extract water from the gas and the gas is then again brought into contact with the product.

In an embodiment of this method, in which the product passes through a drying section in a drying unit, the gas, after having been brought into contact with the regenerable adsorption material, is brought into contact with the product over a first part of the drying section, following which the gas is brought into contact with the regenerable adsorption material again, after which the gas is brought into contact with the product over a second part of the drying section.

In this case, the gas may also pass through a gas-drying section along regenerable absorption material. The gas may pass through a first part of the gas-drying section and then the gas may pass through a first part of the drying section. Following the contact in the first part of the drying section, the gas may pass through a second part of the gas- drying section. This may be followed by a second part of the drying section. If desired, there may be several alternating drying sections and gas-drying sections.

In an embodiment thereof, the first and second drying sections may be separate from one another. In another or further embodiment, the first and second gas-drying sections may be separate from one another.

The invention furthermore relates to a method for drying a product, in which a gas is brought into contact with a regenerable adsorption material, and is subsequently alternately brought into contact with the product to be dried and regenerable adsorption material. In this case, the gas may pass through a drying section and a gas-drying section. In this case, the gas may in each case alternately pass through a part of the drying section and a part of the gas-drying section.

The invention furthermore relates to a method for drying a product, in which a gas is brought into contact with regenerable adsorption material and is subsequently brought into contact with the product to be dried and the regenerable adsorption material is regenerated, and the gas is compressed and exchanges heat with gas before it is brought into contact with the regenerable adsorption material.

The invention furthermore relates to the use of the described method for drying starch at an air temperature of approximately 50-130 degrees Celsius with an energy efficiency of 80-100%.

The invention furthermore relates to the use of the described method for drying milk powder at an air temperature of approximately 60-100 degrees Celsius with an energy efficiency of 80-100%.

The invention furthermore relates to the use of the described method for drying herbs at a temperature of approximately 30-90 degrees Celsius with an energy efficiency of 65- 100%.

The invention furthermore relates to the use of the described method for drying pharmaceutical products at a temperature of approximately 25-30 degrees Celsius with an energy efficiency of 60- 100%.

In an embodiment, the assembly, as described above, comprises a control device which is operationally connected to a meter for measuring the moisture content of the product and/or the temperature of the gas in the drying device, and in which the control device is provided with a preset value for the moisture content of the product and/or the temperature of the gas, and the control device, on the basis of the comparison of the preset and measured values, controls the temperature of the gas which is introduced into the drying device.

With the uses of the assembly and method described above, the product temperature will generally have a lower value than with standard drying systems, as a result of which the impact of the heat on temperature-sensitive products is lower and fewer volatile components are lost.

Drying products is carried out at milder/lower temperatures than in customary processes, such as spray driers, belt driers, fluidized-bed driers and rotating driers of products such as herbs, foodstuffs and pharmaceutical products.

It will be clear that the various aspects mentioned in this patent application can be combined or may each on its own be considered for a divisional patent application.

Short description of the figures

The attached figures show various embodiments of an assembly and method according to the invention, in which: fig. 1 shows an embodiment of an assembly for drying products according to the invention; fig. 2 shows an assembly according to fig. 1 to which an additional drying step has been added and a regeneration stream is returned to the process; fig. 3 shows an alternative embodiment of a device for drying products; fig.4 shows a diagram of the possible use of heat exchangers with a device and method according to the invention; fig. 5 shows a process diagram of the different temperature streams; fig. 6 shows a P-T diagram of some steps in a process according to an embodiment of the invention; fig. 7 shows a process diagram of an embodiment of the invention in a countercurrent process; fig. 8 shows a process diagram of an embodiment of the invention in a cocurrent process; fig. 9 shows a process diagram of an embodiment of the invention in a crosscurrent process.

Description of embodiments

Fig. 1 diagrammatically shows an embodiment of an assembly according to the invention for drying a product. The assembly in this case comprises a drying device 1, an adsorption device 2, and a regeneration device 3. Furthermore, the assembly in this case also has a first heating device for heating gas for regenerating the regenerable adsorbent 4 and a second heating device for preheating gas 5 which will be used for drying product.

In this case, the drying device 1 and the adsorption device 2 are arranged in countercurrent.

The drying device 1 here has a first inlet IS for the gas which is used for drying, and a second inlet 17 for the gas. In addition, the drying device 1 has a first outlet 16 and a second outlet 18 for the gas. The product is introduced into the drying device 1 via inlet 19 and discharged by means of outlet 20.

The progress of the gas through the drying device 1 is diagrammatically indicated by means of arrows 21 and 22. In this configuration, the gas is thus introduced into the drying device 1 via inlet 15, and leaves the drying device 1 in this case halfway along via outlet 16. The gas is then dried again and enters the drying device 1 again via inlet 17 and leaves the drying device 1 via outlet 18.

The adsorption device 2 here has an inlet 7 for gas, an outlet 8 which is connected to the inlet 15 of the drying device 1, a second inlet 9 for gas, connected with the outlet 19 of the drying device 1, a second outlet 10 which is connected to inlet 17 of the drying device 1, a third inlet 11 which is connected to outlet 18, and a third outlet 12.

The adsorption device in this case is furthermore provided with an inlet 13 and outlet 14 for the regenerable adsorbent. The regenerable adsorbent in this case passes through the adsorption device 2 and is in the meantime brought into contact with the gas several times in order to extract moisture from it. Arrow 23 diagrammatically illustrates a part of the path which the gas follows through the adsorption device 2.

The regeneration device 3 has an inlet 24 for regenerable adsorption material and an outlet 25 therefor. The regenerable adsorption material passes through the regeneration device. The inlet 24 is connected to outlet 14 of the adsorption device and the outlet 25 is connected to the inlet 13 thereof. The regenerable adsorption material travels along a (closed) path through the adsorption device to the regeneration device 3 and from the regeneration device 3 back to the adsorption device 2.

The illustrated unit is furthermore provided with a heating device 4 provided with an inlet 29 for gas and an outlet 26 which is connected to an inlet for gas of the regeneration device 3. The assembly is in this case furthermore provided with a heating device 5 in which the gas which is fed to the adsorption device 2 via inlet 7 is heated.

It is possible to achieve process control by means of a control device in one of the following ways.

1. Product moisture content is measured at 20 and the temperature is adjusted at 7 or 1 S by controlling the heat supply at 31 in combination with controlling the regenerator outlet temperature at 25 by regulating heat supply at 31 and/or 32. Both control operations are preferably carried out in accordance with a feedback principle.

2. The air temperature is measured at 21 and the temperature is adjusted at 7 or 15 by controlling the heat supply at 31 in combination with controlling the regenerator outlet temperature at 25 by regulating heat supply at 31 and/or 32. Both control operations are preferably carried out in accordance with a feedback principle.

3. A combination of the above procedures.

Fig. 2 shows an addition to the assembly from fig. 1. The gas with residual heat, in this case a gas, which leaves the regeneration device first passes through a compressor 46 where the pressure is increased. Via line 47, the air from the compressor 46 is supplied to the heating device 5 where it transfers its residual heat to gas by means of a heat exchanger, usually a gas which, is supplied to the adsorption device. In addition, the assembly is provided with an additional drying step 40 provided with a heating device 43 in which the gas from the compressor 46 and/or from the heating device 5 releases further residual heat to gas which is used to dry product further in the additional drying device 40. Actually, the heat recovery has made an additional drying step possible.

In this embodiment, the process may possibly be controlled as follows.

1. As indicated above under option 1 for fig. 1.

2. Product moisture content is measured at arrow 20 or at the location where the product leaves the additional drying device 40 and the temperature is adjusted at 41 or 15 by controlling the heat supply at 31 in combination with controlling the regenerator outlet temperature at 25 by regulating the heat supply at 31 and/or 32. Both control operations are preferably carried out according to a feedback principle.

3. The air temperature is measured at 21 and the temperature is adjusted at 7 or 15 by controlling the heat supply at 31 in combination with controlling the regenerator outlet temperature at 25 by regulating the heat supply at 31 and/or 32. Both control operations are preferably carried out in accordance with a feedback principle, or a combination of the above options.

Fig. 3 shows an alternative embodiment of an assembly according to the invention in which the drying device 1 here has three drying spaces or drying chambers IA, 1 B and 1C, each provided with an inlet and outlet for the product. Here, gas is brought into contact with the product in countercurrent in each drying space. Gas coming from a drying chamber IA, IB, 1C is passed through separate adsorption devices 2A, 2B. Reference numeral 12' in drying chamber 1C denotes an additional gas outlet.

The adsorption devices 2A, 2B are in this case provided with integrated regeneration devices 3A, 3B. These may be adapted in the shape of, for example, what is referred to as desiccant wheels of a system for transporting the adsorbent from the adsorber to the regenerator and from the regenerator to the adsorber; systems which are known per se to those skilled in the art. In this case, the regenerable adsorption material is disposed in wheels. As the wheels turn or by means of the conveying system, the regenerable adsorption material alternately ends up in a chamber or sub-chamber 2A, 2B where it is brought into contact with gas so that moisture is extracted therefrom and this is then brought into contact with the product in drying chambers IA, 1 B and 1C, and in a chamber or sub-chamber 3A, 3B where it is regenerated, for example by exposing it to a gas such as air, at a high temperature.

The gas leaving the regeneration devices 3 A, 3B is compressed by means of a compressor 46. Said compressed gas can then, by means of heat exchanger 50, pass on residual heat to gas which is used for the regeneration and which has to be relatively hot, and subsequently, by means of heat exchanger 51 , to gas which is then brought into contact with the product to be dried. Usually, said gas is first brought into contact with regenerable adsorption material before being passed into the drying device.

1. Product moisture content is measured at 20 and the temperature is adjusted at 7 by controlling the heat supply in heat exchanger 51 or the compressor pressure in combination with controlling the temperature of regenerator outlet 3 A by regulating heat supply in heat exchanger 50. Both control operations are preferably carried out in accordance with a feedback principle.

2. The air temperature at the air outlet at 1C is measured and the temperature is adjusted at 7 by controlling the heat supply at 31 in combination with controlling the regenerator outlet temperature at 25 by regulating heat supply at 31 and/or 32. Both control operations are preferably carried out in accordance with a feedback principle.

3. A combination of both methods 1 and 2.

Fig. 4 diagrammatically shows the options of positioning the heat exchangers in the assembly according to the invention. The gas streams from the regeneration device(s) are usually hotter than the gas which is brought into contact with the product. The gas from the regeneration device can therefore give offheat to gas which is brought into contact with the product, but it can also give off heat to gas which is used for regenerating in order to preheat it. In addition, the regenerated adsorption material, which has a higher temperature than the gas, can, by means of heat exchangers, also give offheat to gas which is used for the regeneration and to gas which is brought into contact with the product. Furthermore, gas coming from the drying device can give off heat in order to preheat gas for drying gas for regenerating. To this end, heat exchangers can be placed at various positions in the assembly.

In order to clarify the various temperatures of the different streams, fig. 5 diagrammatically shows what the temperatures could be in an exemplary process, in which the gas is air, the regenerable adsorption materia! is a zeolite, and drying takes place at 70 degrees Celsius. In this case, the arrows indicate (from top to bottom):

- air at ambient temperature which enters the process for the regeneration device

- air which is passed through the adsorption device and transported to the drying device

- air from the second regeneration device

- air from the first regeneration device - the hot zeolite

- air from the third regeneration device

Fig.6 is a P-T diagram which shows the effect of the compressor in the assembly according to the invention. Air from the regeneration device (point 1) is adiabatically compressed to point 2, during which process the temperature increases. Between point 32 and point 3, cooling takes place (through heat exchange) at a constant pressure, followed by cooling and pressure reduction between point 3 and point 4 through condensation at equilibrium, with additional heat being given off in a heat exchanger.

Fig. 7 diagrammatically shows stages 1 , 2 and n of an n-stage unit in which the product and the gas are brought into contact with one another in countercurrent. The numbers in the figures correspond to the numbers used in the figures above. For stage 1 an A has been added to the figures, for stage 2 a B, etc. Furthermore, a condenser 70 has been added here for cooling the regenerated absorption material. In order to illustrate the process more clearly, some illustrative temperatures are given. These values should not be seen as being limiting. The zeolite stream is indicated by a broken line and the product stream by a dashed line. If desired, the heat of the zeolite can also be recovered, at least partly, by means of a heat exchanger.

Analogously to fig. 7, fig. 8 illustrates the stages 1, 2 and n of an n-stage unit in which the gas and the product are brought into contact with one another in cocurrent.

Analogously to fig. 7, fig. 9 illustrates stages 1, 2, n of an n-stage unit in which the gas and the product are brought into contact with one another in crosscurrent.

The asserablys as described above and according to the invention are furthermore provided with a control device (not shown) which is connected to valves or other control means for regulating the flow rates of the gas streams. The control device is furthermore operationally connected to sensors for determining the moisture content in the gas and the product at various locations and for determining the temperature of the gas and the product at various locations or to sensors for determining the moisture content in the product.

The control device may furthermore be provided with desired values for the various measured values and be adapted to control flow rates and control the temperatures by means of the heat exchangers and heating devices in order to achieve and maintain the preset values.

It will be clear that the above description has been included in order to illustrate the functioning of preferred embodiments of the invention and not in order to limit the scope of the invention. Based on the above explanation, those skilled in the art will be able to think of many variants which are within the spirit and scope of the present invention.