AU2009240871A1 - Apparatus, dryer and method for drying a particulate product with superheated steam - Google Patents

Description

meguiaion j.z AUSTRALIA Patents Act 1990 ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT Invention Title: APPARATUS, DRYER AND METHOD FOR DRYING A PARTICULATE PRODUCT WITH SUPERHEATED STEAM Applicant: Shepherd Systems Pty. Ltd. The following statement is a full description of this invention, including the best method of performing it known to me: 1 APPARATUS, DRYER AND METHOD FOR DRYING A PARTICULATE PRODUCT WITH SUPERHEATED STEAM The present invention generally relates to an apparatus, dryer and method for drying 5 product. The invention is particularly useful for drying particulate product and so will be herein generally described in that context, although it is to be appreciated that the invention may be useful in other applications. Indeed, the invention may find application in drying of other products such as minerals. The drying of food stuffs such as vegetables (for example, potatoes) is also contemplated. 10 It is to be understood that reference to drying of product in the description and claims includes reference to either partial or substantially complete product drying. The use of superheated steam dryers for the drying of particulate matter is generally 15 known. In this regard, conventional drying arrangements include a drying chamber and a separate heat exchanger for generating superheated vapour from water. The superheated vapour produced by the heat exchanger is fed into the chamber by a fan (thus, generally known as "convection dryers"), thereby providing a superheated environment within the chamber in which a particulate product may be dried. Such 20 arrangements are relatively complex in design and relatively expensive to manufacture. This is because, they require separate components in the form of a drying chamber and a heat exchanger to heat the chamber, as well as the need for a fan to direct the superheated vapour from the heat exchanger to the drying chamber. Such arrangements have been known to produce a less than satisfactory dried 25 product and an undesirably non-uniform dried product. It would therefore be desirable to provide an apparatus, dryer and drying method of simplified design. 30 It would also be desirable to provide a drying apparatus and dryer that is more cost effective to manufacture when compared to conventional superheated drying apparatus and dryers. 2 It would further be desirable to provide a drying apparatus, dryer and drying method that potentially produces a better quality and more uniform dried product. According to one aspect of the present invention, there is provided a dryer for drying 5 product. The dryer includes a drying chamber defined by a chamber wall. The drying chamber includes an inlet for entry of product to be dried into the chamber and an outlet for the removal of dried product from the chamber. The chamber includes an inlet seal about the inlet and an outlet seal for sealing the outlet. The inlet and outlet seals are configured to retain superheated steam within the chamber. The dryer 10 further includes a heater for heating the chamber wall to, in turn, heat product within the chamber. The heater is located externally of the chamber. It is to be appreciated that the dryer of the present invention is a conductive dryer, in that the wall of the drying chamber is heated to, in turn, heat the product within the 15 chamber so as to dry the product. Such an arrangement differs from existing dryers, which are generally known as convective dryers, because vapour is caused to flow through a chamber air flow inlet and into the chamber to heat and dry product within the chamber. 20 It is also to be appreciated that the present invention is generally designed such that it is operable as a superheated steam dryer. It is contemplated that the inside temperature of the chamber may have an operating temperature of up to 350 degrees Celsius, although the chamber may be designed to accommodate an operating temperature of 750 degrees Celsius or more. 25 In one preferred form, the chamber has a generally elongated shape, with the inlet provided at a first end of the chamber and the outlet provided at a second end of the chamber. Nevertheless, it is to be appreciated that the shape of the chamber may be selected as desired. 30 In one desired form, the heater includes a gas burner. The gas burner may extend in a generally longitudinal direction proximate to an outer surface of the chamber wall, with the gas burner mounted generally proximate to and below the chamber, or at any other desired position relative to the chamber. The type of gas used in the burner can ""r 3 be selected as desired. It is to be appreciated that the heater may adopt any other suitable form. For example, the heater may include a fuel oil vaporizing (linear) burner, electric heating elements, or an infrared radiation heater. The heater may also include a steam heating (or steam jacketing) arrangement, whereby steam is provided 5 in pipes mounted to, adjacent to or within the chamber wall, such that the steam heats the chamber walls. Preferably, the chamber includes a rotating device for rotating the chamber about an axis running generally longitudinally through the chamber. Chamber rotation is highly 10 desirable because it allows the chamber wall right the way around the chamber to be heated by the gas burner, rather than just the lower portion of the chamber if it was not able to be rotated. Rotation of the chamber above the gas burner allows for a more constant temperature inside the chamber. 15 The dryer may include a transfer device for transferring product through the chamber towards the outlet. The transfer device may include a helix arrangement mounted to an inner surface of the chamber wall and extending in a generally longitudinal direction about the axis. The provision of the helix arrangement will direct particulate matter fed through the inlet and into the chamber through the chamber towards the 20 outlet. It is to be appreciated that movement of product in the chamber towards the outlet occurs passively, that is, simply by rotation of the chamber and without the operation of an independently operable product movement device. One or more agitators may be mounted within the chamber to agitate or mix the 25 particulate matter within the chamber. In a preferred form, the dryer includes an insulating shell surrounding the chamber. The provision of an insulating shell defines a space between the insulating shell and the chamber for mounting of the gas burner. The provision of an insulating shell 30 improves the chamber heating efficiency of the gas burner by retaining a heated layer of air (or other appropriate gas) in the space between the insulating shell and chamber, rather than allowing the heated air to escape directly to the atmosphere. IM.-o4 If desired, a helix or other arrangement may be mounted to the inner surface of the shell and/or the outer surface of the chamber wall to promote even distribution of the heated layer of air about the chamber. 5 Each of the first and second ends of the chamber may include an insulation layer, such that the ends are not directly heated by the heater. The first end of the chamber may be coned, dished or otherwise shaped to facilitate products entering the chamber through the inlet to slide into the chamber along an 10 inner surface of the first end rather than simply falling into the chamber, which may damage or otherwise affect the product. The second end of the chamber may also be coned, dished or otherwise shaped. A vent may be provided in the wall of the chamber for removing of excess 15 superheated vapour generated within the chamber during the heating and drying process. The invention has, so far, been described in the context of a dryer. However, it is to be appreciated that another aspect of the invention relates to an apparatus for drying 20 product, with the apparatus including the aforementioned dryer. The apparatus may include an extruder for supplying extruded product through the inlet and into the chamber. 25 The apparatus may also include a heat exchanger for condensing any excess superheated vapour removed from the chamber. A water supply may extend from the heat exchanger to the extruder for adding water (or other liquid) to the product to facilitate adjustment of the product texture prior to entry into the extruder. In this way, excess superheated vapour, once condensed, may be re-used in the drying process. 30 The inlet seal is generally provided for sealing about an inlet tube, chute, pipe or similar conduit provided for feeding product to be dried into the chamber. The seal may be reconfigured to any other suitable form if desired. 5 A still further aspect of the present invention relates to a method of drying product in a drying chamber. The method includes the steps of: - heating an outer surface of a wall defining the drying chamber until a desired temperature is achieved within the chamber, 5 -adding product to be dried through a chamber inlet, - retaining the product in the chamber for a period of time sufficient to dry the product to a suitable level, and -removing the product from the chamber through a chamber outlet. 10 The method preferably includes the step of extruding the product prior to entry into chamber, although this will depend on the type of product to be dried. Certain products may not need to be extruded. The method may also include the step of removing excess superheated vapour from 15 the chamber. The excess superheated vapour may be condensed in a heat exchanger, with the possibility of later re-use in the process. Water (or other suitable liquid) may be added to the product prior to product extrusion to adjust the product texture. The condensed superheated vapour may be added to 20 the product to alter the product texture. Preferably, the chamber may be rotated during the drying process in order to achieve a more consistent chamber wall temperature when heating the outer wall surface. The speed of rotation may be selected and/or adjusted as desired. 25 The chamber pressure and temperature may be selected for drying a specific product at a pre-determined and generally constant pressure and temperature. However, the drying temperature and pressure within the chamber may be changed if the chamber is to be used for drying another type of product. Also, it is even possible that the 30 chamber pressure and temperature may be varied during the drying of certain products. "''""~ 6 It will be convenient to hereinafter describe preferred embodiments of the invention with reference to the accompanying drawings. The particularity of the drawings is to be understood as not limiting the preceding broad description of the invention. 5 Figure 1 illustrates a side view of a dryer according to one aspect of the present invention; Figure 2 illustrates a first end view of the dryer illustrated in Fig. 1; Figure 3 illustrates a second end of the dryer illustrated in Fig. 1 Figure 4 illustrates schematically an apparatus for drying a product, including the 10 dryer illustrated in Fig. 1. Figure 5 illustrates a side view of a dryer according to another aspect of the present invention. Referring to Figures 1 to 3, there is illustrated a dryer 10 for drying product. The dryer 15 10 includes a chamber 12. The dryer 10 is specifically (but not exclusively) configured to dry paper pellets (of the type generally resembling kitty litter) from an initial moisture content of approximately 30% down to a moisture content of approximately 10%, using a drying temperature within the chamber 12 of up to 350 degrees C with the pressure within the chamber 12 being approximately atmospheric pressure. 20 These operating parameters may of course be changed to suit the specific product to be dried and the extent to which it is to be dried. For example, the dryer 10 may be modified so as to dry minerals and/or foodstuffs. The dryer 10 is configured for substantially continuous operation, apart from routine 25 maintenance, inspection and repair. The drying chamber 12 is defined by a chamber wall 14. The chamber 12 is generally cylindrically shaped and includes curved end-walls 16, 18. The drying chamber 12 includes an inlet 20 at end 16 for entry of product to be dried into the chamber 12; and 30 six separate and substantially identical outlets 22 for the removal of dried product from the chamber 12 at end 18. The outlets 22 may be replaced by a single outlet, if desired. Any number of outlets 22 may be provided. 51._ 7 The chamber 12 includes an inlet seal 24 about the inlet 20. The inlet seal 24 is in the form of a 700 mm outer diameter conventional mechanical seal surrounding the inlet. It is to be emphasized that reference to a seal of 700 mm outer diameter is provided for illustrative purposes, and is in no way intended to limit the scope of the invention. 5 The chamber 12 also includes an outlet seal 26 for sealing each respective outlet 22. Each of the outlets 22 includes a pair of sluice valves 28, 30 (only some of which have been labeled in figure 3). It is to be appreciated that the outlets 22 may be replaced by any other suitable arrangement. Thus, the sluice valves 28, 30 may be 10 replaced by, for example, an auger arrangement. As another possible alternative, the outlets 22 may be replaced by a plurality of sliding plungers inside respective cylinders mounted through the chamber wall, with each plunger acting as a type of valve arrangement. Each plunger may be configured to 15 stroke longitudinally back and forth to remove product from the chamber. Such an arrangement may include a double plunger (or piston) arrangement, whereby dried product is captured between the two plungers and transferred from one end of the stroke from a first port that opens to the inside of the chamber to the other end of the stroke to a second port that opens to the outside of the chamber. 20 The inlet seal 24 and each of the outlet seals 26 are configured to retain superheated steam within the chamber, thereby providing a relatively consistent drying environment for drying product using superheated vapour. 25 The dryer includes a heater 32 (shown in Figure 1 in dashed line format) for heating the chamber wall 14 to, in turn, heat product within the chamber 12. The heater 32 is in the form of a gas burner located externally of the chamber 12 and extending in a generally longitudinal direction proximate to and below an outer surface of the chamber wall 14. The type of gas used in the burner (as well as the type of burner 30 actually used) can be selected as desired. The burner need not be located directly below the chamber 12. It can be seen that the dryer 10 is a conductive dryer, because the wall of the drying chamber 12 is heated to, in turn, heat the product within the chamber 12 so as to dry ""*""" 8 the product. This differs from existing dryers, which are generally known as convective dryers, wherein gas flows through a chamber inlet and into the chamber to heat and dry product within the chamber. 5 The dryer 10 may be used in a variety of operating conditions, depending on the type of product to be dried and the extent of drying sought. The dryer 10 is generally designed such that it is operable as a superheated steam dryer, with the inside temperature of the chamber 12 having an operating temperature of up to 350 degrees Celsius or more. Indeed, the chamber 12 may be designed to accommodate an 10 operating temperature of 750 degrees Celsius or more. The chamber 12 includes a rotating device 34 for rotating the chamber 12 about an axis X-X running generally longitudinally through the chamber 12 during the drying process. The rotating device 34 may be configured as desired, and may include a 15 conventional mechanical drive arrangement to rotate the chamber 12 on the rollers 36. The rollers 36 are rotatably mounted on the supports 38, which are fixed in position to the base 40. The chamber rotation speed may be selected as desired and, in one exemplary form, 20 may be around 4 to 5 rpm. As previously stated, chamber rotation is highly desirable because it allows the chamber wall right the way around the chamber 12 to be heated by the gas burner, rather than just the lower portion of the chamber 12 if it was not able to be rotated. Rotation of the chamber 12 above the gas burner allows for a more constant temperature and atmosphere inside the chamber 12. 25 The dryer 10 includes a transfer device for transferring product through the chamber 12 towards the outlets 22. The transfer device is in the form of an upstanding helix arrangement 42 (shown in dashed line format) mounted to an inner surface of the chamber wall 14 and extending in a generally longitudinal direction about the axis X 30 X. The provision of the helix arrangement 42 directs product (such as particulate matter) fed through the inlet 20 and into the chamber 12 towards the outlets 22. Advantageously, movement of product in the chamber 12 towards the outlets 22 occurs passively, that is, simply by rotation of the chamber 12 and without the operation of an independently operable product movement device. The helix

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9 arrangement 42 has a pitch of 500mm and is 250mm high. It is to be appreciated, however, that the helix height and pitch can be selected as desired. Blades (not illustrated) or an agitator arrangement may be fitted to the helix arrangement 42 (or possibly elsewhere within the chamber 12) to further promote steam(vapour)/product 5 mixing once the product has dried sufficiently to have the mechanical strength to withstand such agitation. The dryer 10 includes an insulating shell 44 (shown in dashed line format) surrounding the chamber 12 and separated from the chamber wall 14 by a distance in 10 the order of 25 mm. The shell does not rotate with the chamber 12, but is instead stationary. The provision of an insulating shell 44 defines a space between the insulating shell 44 and the chamber 12 for mounting of the gas burner 32. The provision of an insulating shell 44 improves the chamber heating efficiency of the gas burner 32 by retaining a heated layer of air (or other appropriate gas) in the space 15 between the insulating shell 44 and chamber 12, rather than allowing the heated air to escape directly to the atmosphere. An arrangement may be provided between the shell 44 and chamber 12 to promote the even distribution of heat about the chamber 12, if desired. 20 Figure 1 indicates that the shell 44 extends over the rollers 36. However, a more practical arrangement is for the drive rollers and associated parts to be spaced outside the length of the chamber 12 at either chamber end, and connected to the chamber 12 with appropriate mounts, which may be welded to the chamber 12. In this 25 way, the shell 44 can adopt a far simpler form. Each of the first and second ends 16, 18 of the chamber 12 includes an insulation layer, such that the air (or other gas heated by the burner) heats substantially only the cylindrical side wall of the chamber 12, and not the ends 16, 18. The arrangement 30 may, however, be reconfigured to allow for heating of one or both of the ends 16, 18, as this may suit some products. The first end 16 of the chamber 12 is of a curved or dish-shape. This shape has been selected such that product entering the chamber 12 through the inlet 20 slides into the 10 chamber 12 along an inner surface of the first end 16, rather than simply falling into the chamber 12, which may damage or otherwise affect the product. This shape is also used so as to provide strength to the chamber 12. 5 The end 18 of the chamber 12 is fitted with an access door 46 of a sufficient size to allow access for maintenance, inspection and repair of the inside of the chamber 12. Two safety valves 48, 50 are provided in the door 46. The valve 48 is provided for relieving suction conditions of about -3.5 kPa within the chamber 12 and the valve 50 10 is provided for relieving pressure in the chamber 12 in excess of about +3.5 kPa. These predefined safety settings may be selected as desired. Safety valves may not be required in some applications. Referring to Figure 4, there is illustrated schematically an apparatus 100 for drying a 15 product, the apparatus 100 including the dryer 10. The apparatus 100 includes an extruder 102 for supplying extruded product directly into and through the inlet 20 and into the chamber 12. It is envisaged that the extruder 102 will be capable of substantially continually supplying extruded product to the dryer 20 10, such that the dryer 10 is able to operate substantially continuously. A seal (not shown) is provided in the chute 103 of the extruder 102 to assist in maintaining a closed chamber 12. The inlet seal 24 extends about the chute 103. The seal 24 may be mounted on the chamber 12, the shell 44, the shute 103, or other suitable component. Similarly, the seal at the outlet end of the chamber 12 may be mounted 25 on any suitable component. The apparatus 100 also includes a heat exchanger 104 for condensing excess superheated vapour generated in the chamber 12 during the drying process. The excess vapour is removed from the chamber 12 through a chamber outlet 106. The 30 heat exchanger 104 may adopt any suitable form, such as a shell and tube heat exchanger. The inlet side of the heat exchanger 104 is fluidly connected to the outlet 106 by a pipe 108. M-11 Although not illustrated, the pipe 108 may extend some distance through the outlet 106 and into the chamber 12. The end of the pipe 108 in the chamber 12 may include a series of holes provided in the side wall of the pipe 108 (only along the section of pipe 108 located within the chamber 12). It is envisaged that the holes would extend 5 along the underside (or lower) region of this section of the pipe wall, so as to allow vapour removed from the chamber 12 to enter the pipe 108 in an upwardly direction and at a potentially low velocity. This arrangement may minimize the likelihood of pipe 108 becoming blocked as a result of dust generated during the drying process. 10 Excess superheated vapour from the drying process is extracted through the outlet 106 and drawn into the heat exchanger 104 by way of a vacuum pump 110, which is connected to the outlet side of the heat exchanger 104 via a pipe 112. Advantageously, the condensed water flowing from the outlet side of the heat exchanger 104 is then fed by a pipe 114 to a water storage arrangement 116 (such as 15 a pondage, tank or reservoir) for later re-use in the drying process. In this regard, a pump 118 is provided for pumping water from the water storage arrangement 116 to a header tank 120 by way of pipes 122, 124. From there, some of the water may optionally be fed into the extruder 102 by way of a pipe 126, and some water may optionally be fed directly to the chamber 102 by way of a pipe 128. Suitable monitors 20 (not shown) may be provided to ensure a suitable product texture for extrusion on the extruder 102, and to ensure a suitable drying conditions within the chamber 12. The water may be filtered prior to re-use. In use, the gas burner 32 initially heats the surface of the rotating chamber 12 to 25 achieve a desired drying temperature of, for example, 350 degrees C in the chamber 12. The burner 32 may be provided with differing burn rates along its length to suit the drying process involved. A sensor(s) not shown may be provided within the chamber 12 to monitor and control 30 the chamber temperature. The chamber 12 may be rotated at any suitable speed, such as 4 to 5 rpm, in order to achieve a drying time of approximately 8 minutes. Reference to a drying time of 8 *""" 12 minutes is provided for illustrative purposes only. The drying time may be selected as desired. Extruded product to be dried can then be added directly from the extruder 102, along 5 the chute 103 and into the chamber 12 through the inlet 20. Referring to the orientation of the dryer illustrated in Figures 1 and 4, product enters the left-hand end of the chamber 12, and is slowly moved towards the right-hand end of the chamber 12 by way of the helix arrangement 42, during which time the product 10 is dried to the desired moisture content (for example from an initial moisture content of 30% to a final moisture content of 10%). The helix arrangement 42 also produces some mixing and lifting of product within the chamber 12 to assist in the drying process. 15 Removal of product occurs by way of the product entering any one of the six outlets 22. Again, the configuration of the outlets 22 may be altered, if desired. For example, a single outlet may be provided. When each outlet 22 reaches its lowermost point on rotation of the chamber 12 the valve body of its respective valve 28 is displaced to the 20 right (as seen in Figure 1) by cam 46 mounted on right-hand support 38. This action allows dried product to pass valve 28 and into cavity 29, following which the valve 28 closes by way of a valve spring (not illustrated) to prevent significant vapour loss. Shortly thereafter the valve body of respective valve 30 is displaced to the right by cam 48 also mounted on right-hand support 38. This action allows dried product to 25 pass from cavity 29 past valve 30 to thereby exit the chamber 12 (but at the same time substantially prevents significant vapour loss from the chamber 12), after which the valve 30 closes by way of a valve spring (not illustrated). It is to be appreciated that in normal operation, a single rotation of the chamber 12 will result in dried product exiting each of the six outlets 22. Prevention of any substantial vapour loss through 30 the outlets 22 ensures that relatively stable drying conditions are maintained within the chamber 12. Although not illustrated, a sensor may be provided to monitor atmospheric conditions within the chamber 12, and to provide data about any water addition needed to 13 maintain the optimum drying conditions. A flow meter may also be provided to measure condensate flow rate as a feedback source for controlling the heating rate and rotation speed of the chamber 12. A filter may be fitted upstream of the vacuum pump for the capture of entrained particulate. A differential pressure transmitter may 5 be provided to monitor the internal pressure of the chamber 12 and adjust the vacuum pump accordingly via a suitable controller. As stated above, the method is described as including the step of extruding the product prior to entry into chamber 12, although this will depend on the type of 10 product to be dried. Certain products may not need to be extruded. Figure 5 illustrates a dryer 110 having a chamber 112 of very similar form to that of the dryer 10 illustrated in Figures 1 to 3, except that only a single outlet 122 is provided. The outlet 122 includes a single valve 128, past which dried product must 15 pass to exit the chamber 112. Advantageously, the present invention provides an apparatus, dryer and drying method of simplified design when compared to conventional superheated dryers. This is because the present invention dispenses with the need for a separate heat 20 exchanger and fan, as is necessary in conventional dryers in order to generate and supply superheated vapour to the drying chamber. Thus, the drying apparatus and dryer of the present invention is potentially very significantly more cost effective to manufacture when compared to conventional 25 superheated drying apparatus and dryers. Advantageously, the drying apparatus, dryer and drying method of the present invention potentially produces a better quality and more uniformly dried product, especially with regard to the drying of certain products because more consistent 30 drying conditions can be obtained and maintained. As previously stated, the dryer, apparatus and method of the present invention may be used for drying a variety of products. The drying of dusty minerals including bauxite, sand and the like is possible, in part, because the present invention involves 14 a very low disturbance of the product being dried, and does not involve high velocity movement of either the product or air, which is a problem associated with many conventional and superheated steam convection-type dryers. 5 Advantageously, the present invention uses considerably less electrical energy when compared to existing fluid, conventional and convection-type superheated steam dryers. For example, the dryer of the present invention may be designed to operate on less than 5 kW when compared to existing arrangements of a similar capacity, which can use 85 kW or more. 10 The invention may also be used for other applications. These applications include the sterilization of products and also cooking of foodstuff, both of which are possible using superheated steam. 15 Finally, it is to be understood that various alterations, modifications and/or additions may be introduced into the construction and arrangement of the parts previously described without departing from the spirit or ambit of this invention. 15

Claims (13)

1. A dryer for drying product, the dryer including: - a drying chamber defined by a chamber wall, 5 - the drying chamber including an inlet for entry of product to be dried into the chamber and an outlet for the removal of dried product from the chamber, - the chamber including an inlet seal about the inlet and an outlet seal for sealing the outlet, the inlet and outlet seals configured to retain superheated steam within the chamber, 10 - the dryer including a heater for heating the chamber wall to, in turn, heat product within the chamber, the heater located externally of the chamber.

2. A dryer according to claim 1, wherein the chamber extends generally longitudinally between the inlet and the outlet. 15

3. A dryer according to claim 1 or 2, wherein the chamber includes a rotating device for rotating the chamber about an axis running generally longitudinally through the chamber. 20 4. A dryer according to any one of the preceding claims, wherein the heater includes a gas burner.

5. A dryer according to claim 4, wherein the gas burner extends in a generally longitudinal direction proximate to an outer surface of the chamber wall. 25

6. A dryer according to claim 4 or 5, wherein the gas burner is mounted generally below the chamber.

7. A dryer according to claim 3, or any one of claims 4 to 6 when dependent on 30 claim 3, including a transfer device for transferring product through the chamber towards the outlet, the transfer device including a helix arrangement mounted to an inner surface of the chamber wall and extending in a generally longitudinal direction along the chamber about the axis. <-fj 16

8. A dryer according to claim 4, or any one of claims 5 to 7 when dependent on claim 4, including an insulating shell surrounding the chamber defining a space between the insulating shell and the chamber, wherein the gas burner is mounted in the space between the insulating shell and the chamber. 5

9. A dryer according to any one of the preceding claims, wherein the inlet is provided at a first end of the chamber and the outlet is provided at a second end of the chamber, and wherein the first and second ends include an insulation layer. 10 10. A dryer according to claim 9, wherein the first end of the chamber is coned or dished to facilitate product entering the chamber through the inlet to slide into the chamber along an inner surface of the first end.

11. A dryer according to any one of the preceding claims, wherein the chamber 15 includes a vent for removal of excess superheated vapour generated during the drying of product.

12. A dryer according to claim 3, or any one of claims 4 to 11 when dependent on claim 3, including a plurality of outlets spaced about the axis, each outlet including a 20 pair of valves provided in series in a flow path through the outlet, with the pair of valves spaced apart in the flow path for the temporary storage of dried product there between.

13. An apparatus for drying product, the apparatus including a dryer according to 25 any one of the preceding claims.

14. An apparatus according to claim 13, including an extruder for supplying extruded product through the inlet and into the chamber. 30 15. An apparatus according to claim 13 or 14, including a heat exchanger for condensing excess superheated steam exiting the chamber through the vent.

41-'oe~c 17 16. An apparatus according to claims 14 and 15, including a water supply extending from the heat exchanger to the extruder for adding water to the product to facilitate adjustment of the product texture prior to entry into the extruder. 5 17. A method of drying product in a drying chamber, including the steps of: - heating an outer surface of a wall defining the drying chamber until a desired temperature is achieved within the chamber, - adding product to be dried through a chamber inlet, - retaining the product in the chamber for a period of time sufficient to dry the 10 product to a suitable level, and - removing the product from the chamber through a chamber outlet. 18. A method according to claim 17, including any one or more of the following steps: 15 - removing excess superheated vapour from the chamber, - extruding product prior to entry into chamber, - adding water to the product prior to product extrusion to adjust the product texture, - rotating the chamber, and 20 - moving the product from the inlet provided at a first end of the chamber to the outlet at a second end of the chamber. 19. A dryer substantially as herein described and illustrated in Figures 1 to 3. 25 20. An apparatus for drying product substantially as herein described and illustrated in Figure 4. 21. A method of drying product substantially as herein described. <rl.."o 18