WO2019145735A1

WO2019145735A1 - Process for treating a material in a toroidal fluidized-bed with electromagnetic radiations

Info

Publication number: WO2019145735A1
Application number: PCT/GB2019/050224
Authority: WO
Inventors: Dodson CHRISTOPHER EDWARD
Original assignee: Mortimer Technology Holdings Limited
Priority date: 2018-01-29
Filing date: 2019-01-28
Publication date: 2019-08-01
Also published as: GB201801430D0; GB2570501A

Abstract

Process for treating a material The present invention relates to a process for treating material, for example a particulate vegetable or mineral material. A process for treating material in a toroidal bed reactor, which process comprises providing a toroidal bed reactor comprising a chamber having an inlet and an outlet; providing a source of electromagnetic radiation; coupling said source to said chamber; introducing material to be treated into the chamber through the inlet thereof; generating a circumferentially directed flow of fluid within the chamber to cause the material to be treated to circulate about an axis of the chamber in a toroidal band; exposing the material to be treated to electromagnetic radiation; and removing the treated material from the chamber through the outlet thereof.

Description

PROCESS FOR TREATING A MATERIAL IN A TOROIDAL FLUIDIZED-BED WITH ELECTROMAGNETIC RADIATIONS

The present invention relates to a process for treating material, for example a particulate vegetable or mineral material.

A toroidal bed (TORBED) reactor and process is described in European Patent No. 0 068 853. In the process, a particulate material to be treated is

embedded and centrifugally retained within a compact, but turbulent, toroidal bed of further particles (optional) which circulate about an axis of the processing chamber.

Specifically, the resident or host particles within the bed are circulated above a

plurality of outwardly radiating, inclined vanes arranged around the base of the

processing chamber. The vanes are preferably arranged in overlapping relationship and the particles are caused to circulate around the bed by the action of a

processing fluid, for example a gas injected into the processing chamber from

beneath and through the vanes.

Both the Compact Bed Reactor (“CBR”) and Expanded Bed reactor (“EBR”) provide a rapidly mixing bed which can be used to circulate particulates through a zone in a process chamber where an interaction occurs with a gas stream.

Microwaves have been used with conventional fluidised bed processes with some success but these processes suffer from uneven microwave distribution.

Importantly, such processes cannot accommodate short particulate retention time requirements where each particle must experience uniform process conditions and retention time.

According to a first aspect of the present invention there is provided a process for treating material in a toroidal bed reactor, which process comprises: (i) providing a toroidal bed reactor comprising a

(ii) chamber having an inlet and an outlet;

(iii) providing a source of electromagnetic radiation; (iv) coupling said source to said chamber;

(v) introducing material to be treated into the chamber through the inlet thereof;

(vi) generating a circumferentially directed flow of fluid within the chamber to cause the material to be treated to circulate about an axis of the chamber in a toroidal band, whereby the material to be treated is exposed to the electromagnetic radiation; and

(vii) removing the treated material from the chamber through the outlet thereof.

Certain types of electromagnetic radiation, for example microwave radiation, tend to have an irregular pattern of penetration into a process chamber. The circulation of the material to be treated about an axis of the chamber reduces or minimises any non-homogeneous distribution of the electromagnetic radiation within the chamber. The material to be treated will typically be heated by the action of the electromagnetic radiation, which may be, for example, a microwave source and/or a radio frequency source. However, other energy sources may be used in

combination, for example convective heating, light, sound and magnetic sources. The flow of fluid within the chamber, which may be at an elevated

temperature, will typically have a horizontal and a vertical velocity component relative to the longitudinal axis of the chamber.

The chamber will typically comprise a plurality of outwardly radiating inclined vanes or appropriately angled nozzles at or adjacent a base thereof. A fluid is directed through these vanes or nozzles at the base of the chamber to generate the circumferentially directed flow of fluid within the chamber. The vanes or nozzles will typically impart both horizontal and vertical velocity components to the fluid.

Alternative chamber constructions are considered and are set out below.

Advantageously, the vanes or nozzles may be adapted or arranged to prevent or minimise the passage of electromagnetic radiation out of the chamber. For example, adjacent vanes or nozzles may preferably be arranged sufficiently close together or with small enough openings to prevent or minimise the passage of electromagnetic radiation out of the chamber, as would be known to one skilled in the art.

The fluid may be heated before and/or after entry into the chamber. This allows for thermal transfer between the fluid and the material to be treated.

The fluid may comprise, for example, air, steam and/or a gas stream produced by combustion of a fuel.

Depending upon the nature of the fluid and the material to be treated and also the processing conditions, the fluid may react chemically with the material to be treated.

In an exemplary embodiment, the processing chamber contains a resident bed of particulate material which circulates about an axis of the chamber when the flow of fluid is generated, and wherein the material to be treated interacts with said resident bed. The resident bed of particulate material may be heated (for example by the fluid) and this allows for thermal transfer between the resident bed and the material to be treated. The circulating resident bed particles will typically define substantially uniform tortuous (unpredictable) paths along which particles of the material to be treated travel before exiting the chamber through the outlet. The average density of the particles of the resident bed may preferably be such that there is little or substantially no migration thereof to the outlet. The circulating resident bed particles provide a turbulent environment within which gas/particles heat and mass transfer properties are enhanced. This consequently enhances heat transfer to the material to be treated. A tortuous/labyrinthine flow type path is provided, which can increase the effective residence time of the material to be treated in the processing chamber, hence increasing the time for heat or mass transfer between the fluid and particles. The circulating resident bed of particles can also act as a heat sink. The material to be treated will generally enter the chamber below and/or adjacent to the circulating resident bed particles in order to contact therewith. Alternatively, if the inlet is vertically spaced above the vanes at the base of the chamber and the circulating resident bed, then the material to be treated will fall down through the chamber, under the action of gravity, on to the circulating resident bed. This may be achieved by, for example, a gravity feed mechanism provided in a vertical wall of the chamber.

In some instances, the material to be treated forms the resident bed. Such a process may be operated in a batch or continuous mode with displacement of the treated particles from the processing region by an opening in the chamber wall or from the inside of the bed by‘scalping’ excess material as it circulates.

The pressure drop through the chamber will typically be less than 400 Pa. The material to be treated may be provided in any suitable form, for example as a particulate, an agglomerate, a sludge, a slurry, a fine powder.

The material to be treated may also comprise liquids and/or solids or a combination of both. Evaporation or sublimation of such liquids or solids may cause a volume, shape and/or structural change in the material to be treated.

Exposure of the material to be treated to the electromagnetic radiation can advantageously be used to cause evaporation or sublimation of any volatile liquids or solids in the material to be treated. This can result in a desired volume, shape and/or structural change in the material. For example, it may be desirable that the treated material comprises expanded, bloated and/or puffed particulates.

The material to be treated may comprise one or more of mineral, animal and/or vegetable matter. When processing vegetable matter, for example, the average residence time of the material to be treated in the chamber is typically from 10 to 600 seconds, more typically from 20 to 60 seconds. When processing fine mineral matter, for example, the average residence time of the material to be treated in the chamber is typically from 5 to 100

milliseconds, more typically 10 to 20 milliseconds.

When drying and devolatilizing organic matter, for example, the average residence time of the material to be treated in the chamber is typically from 5 to 120 seconds, more typically from 10 to 30 seconds.

The process temperature in the chamber is less than 170°C. When processing fine mineral matter, for example, the average residence time of the material to be treated in the chamber is typically from 5 to 100

milliseconds, more typically 10 to 20 milliseconds.

When drying vegetable matter, a particularly advantageous temperature range would be preferably less than 160°C, more preferably from I00°C to 150°C.

An advantage of the process according to the present invention is that the provision of a source of electromagnetic radiation means that lower process fluid stream temperatures can be used. For example, a microwave source can provide the required heat input for expansion of, for example, a particulate material. The corollary of lower fluid temperatures is a reduction in surface heating, which potentially can impart improved quality attributes such as product colour or reduced scorching. By applying a combination of a cooler process fluid stream (eg air) and microwave energy, it is possible to keep the residence times very short with an air temperature significantly less than would be needed if the heat source was convective on its own, in particular when applied to vegetable matter.

According to a second aspect of the present invention there is provided an apparatus for carrying out a process as herein described, the apparatus comprising:

(a) a toroidal bed reactor comprising a chamber having an inlet and an outlet;

(b) a source of electromagnetic radiation coupled to the chamber;

(c) means for introducing a material to be treated into the chamber

through the inlet;

(d) means for generating a circumferentially directed flow of fluid within the chamber, whereby, in use, the material to be treated circulates about an axis of the chamber in a turbulent band and is exposed to the electromagnetic radiation; and

(e) means for removing treated material from the chamber.

All aspects of the invention described in relation to the process are also applicable to the apparatus either singularly or in any combination.

The inlet for the material may be located adjacent a base of the chamber and the outlet will generally be spaced downstream from the inlet. The inlet is preferably located at a position above the vanes of the chamber. The outlet may be vertically spaced above the inlet of the processing chamber, although the inlet may be located adjacent thereto. Both the inlet and the outlet may be provided in or near the centre portion of the process chamber.

The source of electromagnetic radiation may be a microwave source and/or a radio frequency source. The distribution of energy from such a source can be non- homogeneous or non-uniform within the chamber. Thus, the rapid circulation of the material to be treated in a toroidal pattern about an axis of the chamber reduces or minimises such a non-homogeneous distribution. The material to be treated may be introduced into the processing chamber by injecting it through the inlet under the influence of a compressed gas such as compressed air and/or an inert gas such as nitrogen, CFC and other noble/mono- atomic gases. The material to be treated may also be injected with steam. In one embodiment of the present invention, the inlet is located above the vanes at the base of the chamber and the material to be treated is introduced into the chamber by a gravity feed mechanism, for example using an air-lock device such as a rotary valve. The gravity feed mechanism may be provided in a vertical wall of the chamber. It will be appreciated that the flow of fluid may be generated either before or after the material to be treated is introduced into the chamber. Alternatively, the flow of fluid may be generated at the same time as the material to be treated is

introduced into the chamber. Air and/or an inert gas may be used as the fluid. The fluid may optionally be heated. Heating may be achieved by any suitable means. Separate heating means may also be provided for heating the processing chamber and its contents.

The flow of the fluid through the chamber may be generated in a manner as described in EP-B-0 382 769 and EP-B-0 068 853, i.e. by supplying a flow of fluid into and through the processing chamber and directing the flow by means of the plurality of outwardly radiating and preferably overlapping vanes arranged in the form of a disc and located at or adjacent to the base of the processing chamber. The vanes are inclined relative to the base of the chamber so as to impart rotational motion to the heating fluid entering the chamber, hence causing the heating fluid to circulate about a substantially vertical axis of the chamber as it rises.

The present invention will now be described further, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a schematic illustration of an apparatus suitable for carrying out one embodiment of the process according to the invention; Figure 2 is a schematic illustration of part of an alternative apparatus suitable for carrying out one embodiment of the process according to the invention; and Figure 3 is a schematic illustration of a further alternative apparatus suitable for carrying out one embodiment of the process according to the invention.

In Figure 1 , a generally cylindrical processing chamber 1 suitable for carrying out the process according to the present invention is shown. The generally cylindrical chamber 1 tapers 7 towards its base 15. At the base 15 of the chamber 1 there is provided an arrangement of inlet vents 9, wherein each vent 9 is inclined so as to direct a flow of processing fluid away from the longitudinal axis 11 of the chamber 1. The inlets 9 are directed at an angle selected to generate a helical flow E as is known in the art. A flow of a heating fluid, for example steam, enters the chamber via the inlets 9 and imparts rotational motion to the heating fluid entering the chamber 1 so that the heating fluid circulates about a substantially vertical axis 1 1 of the chamber 1 as it rises. By this process, the heating fluid swirls around the chamber 1. This flow of fluid causes particulate material within the chamber to follow a circulation path F whilst rotating around the axis 1 1. A radiation generator 100 for generating electromagnetic radiation is present within the chamber.

Figure 2 depicts an alternative base to that shown in Figure 1. The processing chamber above the base would be the same as that shown in Figure 1. The only difference is that at the base 15 of the chamber 1 there is provided a circular arrangement of overlapping vanes 20, wherein each vane is inclined relative to the base. The vanes 20 radiate outwardly from a central point (optionally, a central hub 21 is provided) on the vertical axis 1 1. A flow of a heating fluid, for example steam, enters the chamber below the vanes 20 and passes through the vanes 20 to enter the chamber 1. The arrangement of the vanes 20 imparts rotational motion to the heating fluid entering the chamber 1 so that the heating fluid circulates about a substantially vertical axis 1 1 of the chamber 1 as it rises. By this process, the heating fluid acts as described for Figure 1. As can be seen from Figure 3, a generally cylindrical processing chamber 1 is shown suitable for carrying out the process according to the present invention. The processing chamber 1 has a feed inlet 5 and a product outlet 10. At the base 15 of the chamber 1 there is provided an arrangement of inlet vanes 25, wherein each vane 25 is inclined so as to direct a flow of processing fluid away from the

longitudinal axis 1 1 of the chamber 1. The inlets 25 are directed at an angle selected to generate a helical flow E as is known in the art. A flow of a heating fluid, for example steam, enters the chamber via the vanes 25 and imparts rotational motion to the heating fluid entering the chamber 1 so that the heating fluid circulates about a substantially vertical axis 1 1 of the chamber 1 as it rises. By this process, the heating fluid swirls around the chamber 1 in a turbulent fashion and then exhausts from the chamber via an outlet 12. A mesh filter may be provided within the chamber in order to restrict the circulation of particulate matter.

Whereas in Figure 1 , means for generating electromagnetic radiation 100 is present within the chamber 1 , in Figure 3, the means 100 is outside the chamber 1 , but a wave guide 102 is provided to direct the radiation into the chamber 1. These alternative ways of exposing material within the chamber 1 to electromagnetic radiation are interchangeable.

As can be seen from Figures 1 to 3, the particular structure of the apparatus is not essential (although that of Figure 3 has been found to be particularly

advantageous). In each case, there is provided a flow of heating fluid that can cause the particles to circulate within the chamber, and a source of electromagnetic radiation (either direct from a radiation generator within the chamber or indirect from an external radiation generator).

There are a number of advantages that can be achieved by a combination of a source of electromagnetic radiation (e.g. microwaves) and a toroidal bed reactor, including:

(^a) application of lower fluid (e.g. air) temperatures; (b) reduced surface over-heating;

(^c) improved colour characteristics of the product;

(d) application to temperature-sensitive products such as fruits and herbs;

(e) ability to obtain a sufficiently low final moisture content for shelf

stability;

(f) an after-drying step after puffing or bloating may be dispensed with;

(g) possibility to expand larger sized products homogeneously;

(h) shorter processing times due to higher efficiency of heating; and

(i) better controlled process due to instant control of heating profile by modifying the microwave power.

Claims

CLAIMS:

1. A process for treating material in a toroidal bed reactor, which process comprises:

(i) providing a toroidal bed reactor comprising a chamber having an inlet and an outlet;

(ii) providing a source of electromagnetic radiation;

(iii) coupling said source to said chamber;

(iv) introducing material to be treated into the chamber through the inlet thereof;

(v) generating a circumferentially directed flow of fluid within the chamber to cause the material to be treated to circulate about an axis of the chamber in a toroidal band;

(vi) exposing the material to be treated to electromagnetic radiation; and

2. A process as claimed in claim 1 , wherein the circulation of the material to be treated about an axis of the chamber reduces or minimises any non-homogeneous distribution of the electromagnetic radiation within the chamber.

3. A process as claimed in claim 1 or claim 2, wherein the material to be treated is heated by the electromagnetic radiation. 3. A process as claimed in any one of the preceding claims, wherein the source of electromagnetic radiation comprises a microwave source and/or a radio frequency source.

4. A process as claimed in any one of the preceding claims, wherein the flow of fluid within the chamber has a horizontal and a vertical velocity component.

5. A process as claimed in any one of the preceding claims, wherein the chamber comprises a plurality of outwardly radiating inclined vanes at or adjacent a base thereof, and wherein fluid is directed through the vanes at the base of the chamber to generate the circumferentially directed flow of fluid within the chamber.

6. A process as claimed in claim 5, wherein fluid directed through said vanes is given both horizontal and vertical velocity components.

7. A process as claimed in claim 5 or claim 6, wherein said vanes are adapted or arranged to prevent or minimise the passage of electromagnetic radiation out of the chamber.

8. A process as claimed in any one of claims 5 to 7, wherein adjacent vanes are arranged sufficiently close together to prevent or minimise the passage of

electromagnetic radiation out of the chamber.

9. A process as claimed in any one of the preceding claims, wherein fluid is heated before and/or after entry into the chamber.

10. A process as claimed in any one of the preceding claims, wherein the fluid comprises air, steam and/or a gas stream produced by combustion of a fuel.

1 1. A process as claimed in any one of the preceding claims, wherein there is heat and/or mass transfer between the fluid and the material to be treated.

12. A process as claimed in any one of the preceding claims, wherein the fluid reacts chemically with the material to be treated.

13. A process as claimed in any one of the preceding claims, wherein the processing chamber contains a resident bed of particulate material which circulates about an axis of the chamber when the flow of fluid is generated, and wherein the material to be treated interacts with said resident bed.

14. A process as claimed in claim 13, wherein there is heat and/or mass transfer between said resident bed and the material to be treated.

15. A process as claimed in claim 13 or claim 14, wherein the circulating resident bed particles define substantially uniform tortuous paths along which particles of the material to be treated travel before exiting the chamber through the outlet.

16. A process as claimed in any one of the preceding claims, wherein the pressure drop through the chamber is less than 400 Pa.

17. A process as claimed in any one of the preceding claims, wherein the material to be treated is provided in the form of a particulate or an agglomerate.

18. A process as claimed in any one of the preceding claims, wherein the material to be treated comprises volatile liquids or solids.

19. A process as claimed in claim 18, wherein evaporation or sublimation of said volatile liquids or solids causes a volume, shape and/or structural change in the material to be treated.

20. A process as claimed in claim 18 or claim 19, wherein exposure of the material to be treated to the electromagnetic radiation causes evaporation or sublimation of said volatile liquids or solids.

21. A process as claimed in any one of the preceding claims, wherein exposure of the material to be treated to the electromagnetic radiation causes a volume, shape and/or structural change in said material.

22. A process as claimed in any one of the preceding claims, wherein the material to be treated comprises mineral, animal and/or vegetable matter.

23. A process as claimed in any one of the preceding claims, wherein the treated material comprises expanded, bloated and/or puffed particulates.

24. A process as claimed in any one of the preceding claims, wherein the process temperature in the chamber is less than 170°C.

25. A process as claimed in any one of the preceding claims, wherein the material to be treated is vegetable matter, and wherein the average resident time of the material to be treated in the chamber is from 5 to 120 seconds, preferably from 10 to 30 seconds.

26. A process as claimed in any of the preceding claims, wherein the material to be treated is vegetable matter, and wherein the process temperature in the chamber is less than 160°C, more preferably from I00°C to 150°C.

27. A process as claimed in any one of the preceding claims, wherein the material to be treated is mineral matter, and wherein the average residence time of the material to be treated is from 5 to 120 milliseconds, preferably from 10 to 30 milliseconds.

28. An apparatus for carrying out a process as defined in any one of the preceding claim, the apparatus comprising:

(a) a toroidal bed reactor chamber having an inlet and an outlet;

(b) a source of electromagnetic radiation coupled to the chamber for exposing material to be treated circulating about an axis of the chamber to electromagnetic radiation;

(c) means for introducing a material to be treated into the chamber through the inlet;

(d) means for generating a circumferentially directed flow of fluid within the

chamber for circulating the material to be treated about an axis of the chamber; and

(e) means for removing treated material from the chamber through the outlet.

29. A method of treating material in a toroidal bed reactor, comprising the steps of:

processing the material using a flow of processing fluid having a temperature of less than 170°C; and

simultaneously exposing the material to electromagnetic radiation.

30. The method of claim 29, wherein the material to be treated is vegetable matter, and wherein the processing fluid has a temperature of less than 160°C, more preferably from I00°C to 150°C.

31. The method of claim 29 or claim 30, wherein the material to be treated is vegetable matter, and wherein the simultaneous processing and exposing steps are carried out for a period in the range 10 to 100 seconds, preferably in the range 20 to 60 seconds.

32. The method of claim 29, wherein the material to be treated is mineral matter, and wherein the average residence time of the material to be treated is from 5 to 100 milliseconds, preferably from 10 to 20 milliseconds.

33. The method of any one of claims 29 to 32, wherein the electromagnetic radiation comprises a microwave radiation and/or radio frequency radiation.

34. The method of any preceding claim, wherein the treated material comprises mineral, animal, organic and/or vegetable matter.