Dehydration plant

• US 6,233,841 B1
• Filed: 11/29/1999
• Issued: 05/22/2001
• Est. Priority Date: 05/28/1997
• Status: Expired due to Fees

• Current Assignee: Napier Stephen Beach
• Original Assignee: Australian Rural Dehydration Enterprise Pty Limited
• Inventors: Beach, Stephen Napier
• Primary Examiner(s): GRAVINI, STEPHEN MICHAEL
• Application Number:
  US09/424,713
• Time in Patent Office: 540 Days
• Field of Search: 342/59, 342/62, 342/64, 342/65, 342/75, 343/81, 344/01, 344/18, 344/29, 34/61, 34/62, 34/66, 34/76, 34/77, 34/78, 342/02, 342/03, 342/12, 342/19, 62/94, 622/71, 219/697, 219/701, 219/752, 993/52, 993/25, 994/43.C, 994/66, 426/467, 426/496, 426/503
• US Class Current: 34/262
• CPC Class Codes: A23L 3/54 using irradiation or electrical treatment, e.g. ultrasonic waves
• CPC Class Codes: F26B 17/045 the material on the belt being agitated, dispersed or turned over by mechanical means, e.g. by vibrating the belt, by fixed, rotating or oscillating elements
• CPC Class Codes: F26B 19/005 Self-contained mobile devices, e.g. for agricultural produce movable devices with radiation means F26B3/28; small self-contained devices for drying objects at rest F26B9/003
• CPC Class Codes: F26B 21/086 by condensing the moisture in the drying medium, which may be recycled, e.g. using a heat pump cycle
• CPC Class Codes: F26B 25/002 for bulk goods F26B17/103 takes precedence
• CPC Class Codes: F26B 3/343 in combination with convection

Abstract

A dehydration plant for dehydrating food products, including a microwave kiln (2), conveyor means (3) for conveying food products through the kiln (2), circulation means (21, 6) for circulating air through the kiln (2), refrigerated dehumidification means (7, 11) for dehumidifying the air to be circulated through the kiln (2), and heating means (12, 13, 14) for heating the air to be circulated through the kiln (2) such that food products conveyed through the kiln (2) are exposed to both microwave emissions and the flow of dehumidified heated air to thereby dehydrate the food products.

Claims

1. A dehydration plant for dehydrating food products, comprising:

(a) a microwave kiln;

(b) conveyor means for conveying food products along a conveying path through the kiln, the conveyor means including a plurality of conveyor segments, each said conveyor segment having a forward upstream end and a rear downstream end, the conveyor segments being positioned in an overlapping arrangement such that the rear downstream ends of at least two of said conveyor segments are spaced above the forward upstream ends of the next respective conveyor segments to define vertical drops spaced along the conveying path through which food products fall,

(c) circulation means for circulating air through the kiln including the vertical drops;

(d) refrigerated dehumidification means for dehumidifying the air to be circulated through the kiln; and

(e) heating means for heating the air to be circulated through the kiln;

such that food products conveyed through the kiln are simultaneously exposed to both microwave emissions and the flow of dehumidified heated air to thereby dehydrate the food products.

2. A dehydration plant according to claim 1 wherein each of the conveyor segments is located on an incline such that the rear downstream end is higher than the forward upstream end thereof.

3. A dehydration plant according to claim 1 wherein the conveyor segments convey food products in generally the same direction through the kiln.

4. A dehydration plant according to claim 1 wherein the microwave kiln includes a kiln tunnel through which food products can be conveyed, the kiln tunnel including microwave emission means for exposing food products conveyed therethrough with microwaves.

5. A dehydration plant according to claim 4 wherein the microwave emission means includes a plurality of microwave emitter horns in an elongated direction of the kiln tunnel.

6. A dehydration plant according to claim 1 wherein each said conveyor segment includes a conveyor belt supported on and movable about a front and rear conveyor drum, the conveyor belt being made from a low loss dielectric material and formed of a plurality of chain links interconnect by tie rods to thereby provide openings through the conveyor belt.

7. A dehydration unit according to claim 6 wherein at least a portion of the chain links includes a lateral spike.

8. A dehydration plant according to claim 6 wherein each conveyor segment includes a conveyor belt supported on and movable about a front and rear conveyor drum, the conveyor belt being formed from a mesh material to thereby provide openings through the conveyor belt.

9. A dehydration plant according to claim 7 or 8 wherein a microwave reflector dish is located between the front and rear drive drums of each said conveyor segment, the microwave dish including a cover made of a low loss dielectric material and having an extendible edge lip at the forward upstream edge thereof, for acting as an air deflector.

10. A dehydration plant according to claim 9 wherein the extendible edge lip further includes a row of resilient prongs for engaging an underside of the conveyor belt to thereby provide agitation of the said conveyor belt.

11. A dehydration plant according to claim 10 further including an upper reflector dish over each reflector dish of the conveyor segment, each said microwave emitter horn being located within a respective said upper reflector dish, at least one microwave deflector fan being further located within each said upper reflector dish.

12. A dehydration plant according to claim 1 wherein the circulation means includes an air circulation duct and a fan located within the duct for drawing air into the dehydration plant, the refrigerated dehumidification means and the heating means being located in the air duct downstream of the circulation fan.

13. A dehydration plant according to claim 12 wherein the refrigerated dehumidification means includes evaporation coils located immediately downstream of the circulation fan for cooling and therefore dehumidifying the air, and wherein the heating means includes a heat exchanger provided downstream of the evaporator coils for adding heat to the cooled air.

14. A dehydration plant according to claim 13 wherein a further heat exchanger is provided upstream of the circulation fan, said further heat exchanger absorbing heat from air exiting the kiln tunnel.

15. A dehydration plant according to claim 13 or 14 wherein the refrigerated dehumidification means includes condenser coils located downstream of the heat exchanger to further heat the air passing therethrough.

16. A dehydration unit according to claim 14 further including heating coils located downstream of the condenser coils for provide a further heat input into the dehumidified heated air prior to circulation into the microwave kiln.

17. A dehydration plant according to claim 13 further including a mixing vane within the air duct for controlling the amount of air recirculated through the air duct and the amount of air exhausted from the dehydration plant.

18. A dehydration plant according to claim 1 further including a transportable enclosure for accommodating the dehydration plant.

19. A dehydration unit according to claim 18 wherein the enclosure is an insulated standardised industrial freight container.

20. A dehydration unit according to claim 18 or 19 further including an intake conveyor for transporting food products through an inlet opening in the enclosure to the microwave kiln, and a discharge conveyor for transporting dehydrated food products from the microwave kiln and though a discharge opening of the enclosure.

21. A dehydration plant according to claim 20 further including a food pretreatment zone provided over at least a portion of the intake conveyor for preheating and bacterial control of the food product entering the microwave kiln.

22. A dehydration plant according to claim 20 wherein the intake and discharge conveyors are retractable into the enclosure, and the inlet and openings of the enclosure include closure means for sealing the dehydration plant within the enclosure.

28. A plurality of dehydration plants according to any one of claims 1 to 21, said dehydration plants being coupled in series.

23. A method of operating a dehydration plant for dehydrating food products, the method comprising:

(a) conveying a food product along a conveying path through a microwave kiln;

(b) dehumidifying and heating air within the plant;

(c) circulating the dehumidified heated air through the microwave kiln, such that the food product is simultaneously exposed to both microwave emissions and the circulated dehumidified heated air within the microwave kiln; and

(d) cascading the food product through a plurality of vertical drops spaced along the conveying path within the microwave kiln during step (c) to thereby maximize exposure of the food product to the circulated dehumidified heated air.

24. A method according to claim 23 including collecting the heat of the air that has passed through the microwave kiln and supplying said collected heat to the air upstream of the microwave kiln.

25. A method according to claims 23 or 24 further including heating the food product upstream of the microwave kiln.

26. A method according to claim 23 further including exposing the food product to ultra-violet radiation upstream of the microwave kiln for providing bacterial control for the food product.

27. A method according to claim 23 including conveying the food product through a coupled series of said dehydration plants.

29. In combination, a plurality of dehydration plants for dehydrating food products, the dehydration plants arranged in series to successively dehydrate the food products, each dehydration plant comprising:

(a) a microwave kiln;

(b) conveyor means for conveying food products along a conveying path through the kiln, the conveyor means including a plurality of conveyor segments, each said conveyor segment having a forward upstream end and a rear downstream end, the conveyor segments being positioned in an overlapping arrangement such that the rear downstream ends of at least two of said conveyor segments are spaced above the forward upstream ends of the next respective conveyor segments to define vertical drops spaced along the conveying path through which food products fall,

(c) circulation means for circulating air through the kiln including the vertical drops;

(d) refrigerated dehumidification means for dehumidifying the air to be circulated through the kiln; and

(e) heating means for heating the air to be circulated through the kiln;

such that food products conveyed through the kiln are simultaneously exposed to both microwave emissions and the flow of dehumidified heated air to thereby dehydrate the food products.