AU6560694A

AU6560694A - Rotary thermal processor with cooled radiant heat source

Info

Publication number: AU6560694A
Application number: AU65606/94A
Authority: AU
Inventors: Dirk Cortesi
Original assignee: INFRA RED TECH Pty Ltd
Current assignee: INFRA RED TECHNOLOGIES Pty Ltd
Priority date: 1993-04-21
Filing date: 1994-04-21
Publication date: 1994-11-08

Description

ROTARYTHERMALPROCESSORWITHCOOLEDRADIANTHEATSOURCE

FIELD OF THE INVENTION

This invention relates to an apparatus for the thermal processing of particulate material and, in particular, but not exclusively, to an apparatus for the thermal processing of particulate foodstuffs.

BACKGROUND OF THE INVENTION

It is known to thermally process foodstuffs for various purposes including drying, baking, sterilising, inactivating enzymes and cleaning etc. Typically such thermal processing has been performed by transporting a foodstuff on a conveyor through an oven or a fluidised bed. However, this form of thermal processing can suffer from the disadvantage of overheating the outside and under-heating the core of the foodstuff. Furthermore, this process is energy inefficient as the whole interior of the oven and conveyor belt is heated.

An alternative to convection heating is the use of microwaves. While microwave thermal processing can be more efficient than convection heating it can only be used if the foodstuff to be processed contains or is mixed with water or some other polar liquid.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an apparatus for the thermal processing of particulate material which attempts to alleviate at least one of the disadvantages in the above described prior art, or improve on the overall efficiency.

According to the invention there is provided an apparatus for thermal processing of particulate material comprising: an elongate hollow rotatable body through which said particulate material passes; a radiant heat source disposed within said body for illuminating the interior of said body and said particulate material with radiant heat; a cooling means extending through said elongate hollow body for absorbing a first proportion of heat to protect said radiant heat source from overheating, whereby, in use, said particulate material transverses the length of said body by the combined action of gravity and the rotation of said body and is thermally processed by the absorption of a second proportion of said radiant heat, and said cooling device operating to prevent overheating of said radiant heat source.

Preferably said cooling means transfers heat absorbed within said body to a location exterior of said body.

Preferably said cooling means comprises an elongate element disposed within said body through which a liquid can flow and a liquid storage and cooling tank located exterior of said body for storing and cooling a volume of said liquid, said storage tank being in fluid communication with said elongate element whereby, in use, said first proportion of radiant heat is absorbed by said liquid and said liquid circulates through said elongate element and storage tank to transfer heat absorbed within said body to said volume of liquid and the surrounding environment.

Preferably said cooling means includes a conduit coupled to said elongate element for returning said liquid to said tank after flowing through said body, said conduit passing through a supply of said particulate material for preheating said material and cooling said liquid.

Preferably said apparatus further comprises a reflector located within said body for reflecting radiant heat produced by said radiant heat source onto a flow path on the inner surface of the body which is traversed by said particulate material. Advantageously said reflector is disposed on a portion of the outer surface of said elongate element.

Advantageously said portion of the outer surface is concavely curved. Preferably said apparatus further comprises a guard disposed between said radiant heat source and said flow path, said guard formed in a manner to allow transmission of said radiant heat therethrough and to substantially prevent parts of said radiant heat source from falling into said particulate material in the event that said radiant heat source breaks during operation.

Preferably said guard comprises an elongate member made of radiant heat transmissible material.

Advantageously said guard is attached to said elongate element with said radiant heat source disposed between said guard and said elongate element.

Preferably said apparatus further comprises means for adjusting the inclination of said body to the horizontal to thereby allow control of the time taken for said particulate material to traverse the length of said body.

Preferably said adjusting means comprises an extendable member supporting said body.

Preferably said apparatus further comprises means for adjusting the distance between said radiant heat source and said flow path.

Preferably said apparatus further comprises at least one agitating device connected with the inner surface of said body for agitating said particulate material as said body rotates.

Preferably power supply cables for said heat source extend through said elongate element to prevent overheating of said cables.

BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention will now be described by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a view of the apparatus form the side in partial cross-section.

Figure 2 is an elevation view of the apparatus from the rear;

Figure 3 is an enlarge end view of a cooling means and heat source used in the apparatus shown in Figures 1 and 2;

Figure 4 is an enlarged side view of a length of the cooling means and heat source shown in Figure 3; and,

Figure 5 is an end view of a scraper/cleaner incorporated into the apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in the accompanying drawings, an apparatus 10 for thermal processing of a particulate material comprises an elongate hollow rotatable body (or tube) 12 through which a particulate material, for example, a mirconized foodstuff 14 passes. A radiant heat source in the form of infra-red lamps 16 (refer Figure 2) are disposed within the tube 12 for illuminating the interior of the tube 12 and the foodstuff 14 with radiant heat. The exterior of tube 12 is insulated to reduce heat loss to the surrounding environment.

A cooling means 18 is provided for absorbing a first proportion of the heat to protect the infra-red lamps and associated power cables from overheating.

The foodstuff 14 traverses the length of the tube 12 by the combined action of gravity and the rotation of the tube (as explained in more detail hereinafter) . During this motion, the foodstuff 14 is processed by the absorption of radiant heat from the infra-red lamps 16.

The tube 12 is inclined to the horizontal by an angle 1° and has an inlet opening 20 provided at one end and an outlet or discharge opening 22 at an opposite end. The angle of inclination 1° is arranged so that the inlet opening 20 is raised with respect to the outlet opening 22. The tube 12 is rotatably mounted on idler rollers 24 which in turn are supported on frame 26. An electric motor 28 is supported on a platform 30 suspended beneath the frame 26 for rotating the tube 12. The motor 28 is connected to the tube 12 by means of a chain 32 which engages a sprocket wheel 34 coupled to an output shaft of the motor 28 and a sprocket wheel 36 circumferentially mounted on the exterior of the tube 12. Electric motor 28 is fitted with a variable speed drive mechanism to enable the tube 12 to rotate at variable speeds, facilitating a variable flow of foodstuff 14.

A hopper 38 is supported on the frame 26 adjacent the inlet end of the tube 12. The hopper has an open top 40 and a discharge chute 42 which extends into the tube 12 through inlet opening 20. A rotating screw feeder 44 is located within the discharge sheet 42 for assisting in discharging foodstuff 14 from the hopper into the tube 12.

The rotating screw feeder 44 is connected to a motor 45 by chain 47 which engage a sprocket wheel 49 coupled to an output shaft of the motor 45 and a sprocket wheel 51 coupled to the rotating screw feeder 44. The speed of motor 45 is variable enabling the rate of rotation at the screw feeder 44 and thus the flow rate of the foodstuff 14 to be controlled facilitating variable product flow.

Cooling means 18 comprises an elongate element formed from a pipe 50 of square cross-section which fits within a pipe 52. Pipe 52 has three planar sides 53A, 53B, 53C and are concavely curved side 53D. The space between the exterior surface of pipe 50 and interior surface of pipe 52 forms a jacket 54 through which water can flow. A number of ducts 55 are provided which communicate between the interior of pipe 50, extend through pipe 52 and open onto curved side 53D. Pipe 52 is supported at its opposite ends by brackets 57 connected to frame 26. The brackets 57 are arranged so as to allow adjustment of the distance of the cooling means (and thus the lamps 16) to the interior surface of the tube 12 and the foodstuff 14.

A water tank 56 for holding a volume of water used for cooling the lamps 16 is supported on frame 26 located near and exterior of tube 12. A conduit 58 connects one end of the jacket 54 to a return opening near the top of the tank 56 for returning water which has passed through the jacket 54 and consequently been heated. Conduit 58 winds through the hopper 38 so as to transfer energy to the foodstuff 14 resulting in a pre-heating of the foodstuff 14 and cooling of the water. A second conduit 60 connects an opposite end of water jacket 54 with an outlet opening formed at the bottom of trunk 56.

When lamps 16 are on, the pipe 52 and in particular, surface 53D becomes heated by absorption of energy radiated by the lamps 16. This heat is transferred by conduction to water in jacket 54. The absorption of heat by the water in jacket 54 forms convection currents causing circulation of water through jacket 54, conduit 58, tank 56 and conduit 60.

The lamps 16 are disposed near surface 53D of the pipe 52 and are placed end to end extending over substantially the entire length of the tube 12. In order to direct heat radiated by lamps 16 onto the foodstuff 14, the exterior surface of concavely curved surface 53D is formed into a reflector 59. This can be done by coating this surface with a thin layer of reflective metal or alloy.

Ends 61 of the lamps 16 are supported by connector blocks 63 (refer Fig. 4) attached to the exterior surface of curved side 53D. Electrical power cables 65 for supplying power to lamps 16 extend through pipe 50. Cables 65 are coupled to connectors 67 from which wires 69 extend through ducts 55 to connector blocks 63 to supply power to individual lamps 16. As the cables 65 extend through pipe 50 they are not subject to any substantial heating.

Typically, the infra-red lamps 16 are of tubular, quartz construction having an operating temperature of 500°F-3000°F, a peak energy wave length of 1.2 - 6.0 microns, a maximum intensity of 120kw/m², a heat/cooling time period of two minutes, a maximum process temperature of 600°F with at least 80% of the heat generated being in the form of radiant heat. The applicant has discovered that ordinarily, heat absorbed by the reflector 59 is re-radiated onto the lamps 16 and can cause overheating of the lamps and in particular, to the ends 61, resulting in a breakdown of the weld connecting the end 61 to the quartz tubing of the lamps 16. This allows gases within lamps 16 to escape and subsequent failure of the lamps 16. In addition, the tube 12 itself becomes heated due to the combined effects of receiving heat from lamps 16 and by conducting heat from the foodstuff 14. The heated tube, in the absence of the cooling means 18, would re-radiate heat onto lamps 16 exacerbating the problem of overheating. The failure of the infra-red lamps 16 can be catastrophic with the infra¬ red, lamps shattering. Alternatively, the effects of overheating may lead to an accelerated degradation in lamp efficiency.

However, in the present embodiment is substantially avoided by the described cooling means 18 which effectively cools the reflector 59, and absorbs heat re-radiated by tube 12 onto sides 53A, 53B and 53C, minimising the amount of heat re-radiated onto the lamps 16.

In the event that one or more of the lamps 16 do shatter, notwithstanding the provision of the cooling means 18, a guard 62 is provided within the tube 16 between the infra-red lamps 16 and the foodstuff 14 to catch the falling lamp pieces. The guard extends for the length of the infra-red lamps 16 and is connected to the pipe 52, enclosing the lamps 16 between the guard 62 and reflector 59. The guard 62 is made of a material which allows the transmission of infra-red radiation with minimal absorption. Adjusting means 66 (refer Fig. 2) is provided for adjusting the angle 1° of inclination of the tube 12 to the horizontal to allow control over the time taken for the foodstuff 14 to traverse the length of the tube 12. In the present embodiment, the adjusting means 66 comprises a sleeve 68 connected to an underside of the frame 26 and a leg 70 which can slide within the sleeve 68. The sleeve 68 is provided with a series of holes 72. A hole (not shown) is also provided in the leg 70 for registration with one of the holes 72. When the desired angle of inclination 1° is achieved by- sliding the leg 70 in the sleeve 68, the leg 70 is locked in place by passing a pin 74 which is tethered to a frame 26 through the hole 72 which registers with the hole in the leg 70. A similar adjusting means is provided for each of the legs supporting the tube 12. To assist in the even heating of the foodstuff

14, agitators 71 can be attached to the inner surface of tube 12. The agitators can take many different forms such as rods (as shown in Fig. 2) or angle irons, flanges, etc. In order to clean the inner surface of tube 12 and the exterior of pipe 52, a cleaner/scraper 73 (refer Fig. 5) can be demountably or fixedly fitted to the interior of tube 12. The cleaner/scraper 73 includes a pipe 75 through which can flow air or another cleaning fluid (ie., including liquid) disposed above flanges 77 for dispersing the fluid. The flanges can rest on surfaces 53A and 53B of pipe 52. A belt 79 is attached to one flange 77 and is arranged to have a length bear against the inner surface of the tube 12 for scraping off any particulate material which may adhere thereto. The operation of the apparatus will now be described. The foodstuff 14 to be processed is charged into the hopper 38 through the open top 40. Motors 28 and 45 are then started, causing rotation of the screw feeder 44 and the tube 12, respectively. The tube 12 rotates at approximately four revolutions per minute, but is variable. The infra-red lamps 16 are also activated causing the irradiation of radiant heat. The foodstuff 14 contained within the hopper 38 is discharged via the chute 42, at controllable rates, through the inlet 20 into the tube 12. While traversing the length of the tube 12, the foodstuff 14 absorbs radiant heat from the infra-red lamps 16. This dries, cooks, roasts, bakes, sterilises of inactive enzymes in the foodstuff 14, driving off moisture contained therein which passes out of the tube 12 at the inlet 20. An extractor (not shown) can be used to transport the said moisture away from equipment to prevent condensation forming.

The rotation station of the tube 12 and lifters 71 causes intimate mixing of the foodstuff and uniform heat absorption.

The combined effects of the rotation of the cylinder 12 and the inclination of the tube 12 causes the foodstuff 14 to be displaced progressively from the inlet 20 toward the outlet 22. Foodstuff 14 falling from the opening 22 is collected in a container (not shown) located beneath the opening 22.

Heat from the infra-red lamps 16 absorbed by reflector 59 is in turn absorbed by water flowing through jacket 54. Heat re-radiated by tube 12 onto sides 53A, 53B and 53C is also absorbed by this water. This effectively cools the infra-red lamps 16 maintaining them in at their most efficient operating temperature. The power cables 65 are maintained at a relatively low temperature by virtue of extending through pipe 50. Heated water returning to tank 56 through conduit 58 preheats the foodstuff 14 and is thus also cooled. In the event that any of the infra-red lamps 16 break, notwithstanding the cooling effect of the circulating water, the guard 62 operates to catch fragments of the lamps 16 to substantially prevent them from falling into the foodstuff 14. Guard 62 also prevents foodstuff 14 to contaminate and soil the infra-red lamps 16 and reflector 59. Guard 62 also facilitates easy cleaning with water of the entire equipment, without water being in contact with any electrical component.

The time taken for the foodstuff 14 to transverse the length of the tube 12 is dependent upon the angle of inclination 1° and the physical properties of the foodstuff itself.

The apparatus 10 can be used on a wide variety of foodstuffs for human and animal consumption such as, soya beans, coco beans, faba beans, peas, lupins, maize, wheat and barley. In addition, the apparatus 10 can be used in other applications such as the drying of gold and andalusite ore, paper, wood shavings, brewers grains and other fodder's, leather and wood, sterilisation of paper pulp, potting soil and sewerage sludge, and thermal processing of other biological materials and substances, and the roasting of peanuts. Indeed, any product that requires energy input being it for drying, roasting, cooking, sterilisation, inactivation, expansion or whatever, and is free flowing can be processed by embodiments of this invention.

Now that an embodiment of the invention has been described in detail, it will be apparent to those skilled in the relevant arts that numerous modifications and variations may be made without departing from the basic inventive concepts. For example, the adjusting means 66 can be replaced with other equivalent mechanical devices, such as for example, a rack and pinion arrangement, hydraulic rams, or feet which readily engage with the bottom of the legs 70 and can be screwed in the direction of the length of the legs 70. In addition, the hopper 38 can be made to slide along a rail connected to frame 26 to move away from tube 12 to facilitate easy access through opening 20 for maintenance purposes. In this variation, flexible hoses are required intermediate the length of conduits 58 and 60, or alternatively couplings in conduits 58 and 60. Furthermore, the energy (ie. heat) applied to the particulate material can be controlled or varied in accordance with the type of material, the effect intended to be achieved; feed rate of the material from the hopper into the tube 12 and rotation speed of tube 12. The variation in energy can be achieved by switching the lamps on and off at programmable rates or using lamp 16 of different maximum intensity. The motors 28 and 45 and power supply to lamps 16 can be under the control of a Programmable Logic Controller. Modifications and variations are deemed to be within the scope of the present invention the nature of which is to be determined from the foregoing description and appended claims.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:-

1. An apparatus for thermal processing of particulate material comprising: an elongate hollow rotatable body through which said particulate material passes; a radiant heat source disposed within said body for illuminating the interior of said body and said particulate material with radiant heat; a cooling means extending through said elongate hollow body for absorbing a first proportion of heat to protect said radiant heat source from overheating, whereby, in use, said particulate material transverses the length of said body by the combined action of gravity and the rotation of said body and is thermally processed by the absorption of a second proportion of said radiant heat, said cooling device operating to prevent overheating of said radiant heat source.

2. An apparatus according to claim 1, wherein said cooling means comprises an elongate element through which a liquid can flow disposed within said body and a liquid storage and cooling tank located exterior of said body for storing and cooling a volume of said liquid, said storage tank being in fluid communication with said elongate element whereby, in use, said first proportion of radiant heat is absorbed by said liquid and said liquid circulates through said elongate element and storage tank to transfer heat absorbed within said body to said volume of liquid and the surrounding environment.

3. An apparatus according to claim 2, wherein said cooling means includes a conduit coupled to said elongate element for returning said liquid to said tank after flowing through said body, said conduit passing through a supply of said particulate material for preheating said material and cooling said liquid.

4. An apparatus according to claim 3, wherein a reflector located within said body for reflecting radiant heat produced by said radiant heat source onto a flow path on the inner surface of the body which is traversed by said particulate material.

5. An apparatus according to claim 4, wherein said reflector is formed on a portion of the outer surface of said elongate element.

6. An apparatus according to claim 5, wherein said portion of the outer surface is concavely curved.

7. An apparatus according to claim 6, further comprising a guard disposed between said radiant heat source and said flow path, said guard formed in a manner to allow transmission of said radiant heat therethrough and to substantially prevent parts of said radiant heat source from falling into said particulate material in the event that said radiant heat source breaks during operation.

8. An apparatus according to claim 7, wherein said guard comprises an elongate member made of radiant heat transmissible material.

9. An apparatus according to claim 8, wherein said guard is attached to said elongate element across said reflector with said radiant heat source disposed between said guard and said reflector.

10. An apparatus according to claim 9, further comprising means for adjusting the inclination of said body to the horizontal to thereby allow control of the time taken for said particulate material to traverse the length of said body.

11. An apparatus according to claim 10, further comprising at least one agitating device connected with the inner surface of said body for agitating said particulate material as said body rotates.

12. An apparatus according to claim 2, wherein power supply cables for said heat source extend through said elongate element to prevent overheating of said cables.