| Title of Invention | MICROWAVE TEA DRYER. |
|---|---|
| Abstract | A microwave tea dryer comprising means for generating microwave radiation which is adapted to fall on tea to be dried whereby the radiation hits the liquid molecule/volatile compound to thereby vibrate and generate heat to cause drying of the tea. The dryer utilizes a process of heating by vibration by means of microwave radiation and not by heat transfer mechanism to achieve higher efficiency. Importantly, lsince in the tea dryer such vibration does not take place if the material does not contain liquid, there is no unnecessary heating in the absence of liquid i.e. water and there is also thus no lchance lof overheating of the tea. The tea dryer is free of noise during operation and is environment friendly apart from protecting the material from any atmospheric/fuel contamination. The tea dryer is directed to provide for simple, cost-effective and efficient drying of materials/substances such as tea and the like without affecting the character and quality of the tea. |
| Full Text | The present invention relates to a microwave tea dryer for use in drying of tea. Drying is one of the most important stage in manufacturing of black tea. During drying, the fermented tea is dried up and its moisture content is reduced to about 2-5%. The main purpose of drying operation is: a) to stop the process of fermentation ; b) to reduce the moisture content; c) to give a granular form to the fermented tea. Drying of tea is performed in drying machines commonly known as dryer. The presently available dryers are of three types — a) chain type dryer b) fluid bed dryer c) vibro fluid bed dryer In all the above three dryers, the process of drying is performed by heat and mass transfer mechanism. The inlet temperature of the dryer is generally held between 95-100°C.- The outlet temperature is maintained at 50-55°C. The quality of the final made tea during drying depends on the following parameters : a) inlet and outlet temperature of the hot air b) feed rate of the fermented leaf c) run through time of solid d) volume of air Conventionally, the inlet temperature of hot blast of air into the dryer is kept constant by regulating the temperature of the furnace and velocity of not air from the furnace. In the old chain type of dryers, the fermented tea is moved from inlet to outlet over a chain type of conveyor belt in several layers inside. The hot air is blown from down end so that it moves through the layers of fermented tea residing over the conveyor. The disadvantage of the dryer is that the heat transfer mechanism to the solid particles is not efficient eausing toss of heat. The fluid bed dryers (FBD) and the Vibro fluid bed dryers (VBFD) are much more efficient than the chain type dryers in heat transfer mechanism. The movement of the solid particles takes place due to fluidization and vibration. The major disadvantages of the above type of dryers are - i) loss of heat due to inefficient heat transfer ii) low efficiency of the heating system iii) highly noisy iv) pollution of air due to the heating air fired by coal, gas or oil v) contamination of the tea as it comes in direct contact with the hot air. It is thus the basic object of the present invention to provide a new type of tea dryer which would avoid problems of heat loss and would therefore be highly efficient for drying of tea. Another object is to provide a new type of tea dryer which would be environment friendly and will not be noisy during operation. Yet further object is to provide a new type of tea dryer which apart from being efficient for tea drying purposes would not contaminate the product to be dryed and avoid problems such as contamination of tea during drying when it comes in direct contact with hot air. Yet further object is to provide for a new tea dryer which would provide for fast, economic and efficient drying of tea as compared to conventional tea dryers presently available. Thus according to the present invention there is provided a microwave tea dryer for drying of tea comprising: means for generating microwave radiation being a magnetron housed in a drying chamber (9) and allowing the thus generated radiation to fall on the tea to be dried and thereby effecting drying by vibration and consequential heating of the liquid volatile components in said tea to thereby dry said tea; means for regulated supply of the tea to the drying chamber such that the radiation generated vibrate and heat the liquid/volatile components of said tea comprising: (a) feeder/hopper (1) adapted to allow fall of tea on the top conveyor in said drying chamber and positioned adjacent to said means for generating microwave radiation; (b) means for controlling the thickness and speed of the material on the said conveyor comprising a separator means being a spreader (2); and (c) a plough means (8) adapted to provide an even distribution of heating to the tea and positioned just above the conveyors (3) so as to plough through the tea travelling on the conveyor; and means for collection of the thus dried tea, characterized in that said top conveyor is adapted such that initially the spread tea is first allowed to traverse through the said drying chamber for a first stage of primary drying and thereafter tea is allowed to fall on a further moving lower conveyor which runs in the reverse direction for further secondary drying of the tea such that a drop door (13) provided adjacent to the right end of said top conveyor allows the primary dried tea to fall on the further said moving lower conveyor, which runs in the reverse direction from said first conveyor as aforesaid and a second drop door (14) adjacent to the end of the said lower conveyor adapted to allow drop of said tea in a collecting bin (10) provided below. It is also possible by way of the above disclosed embodiment of the tea dryer having the plurality of drying chambers to provide for a tea drying system with variable power depending upon the end user requirements. The fermented tea will first enter the first drying chamber when the first drying step is initiated and thereafter the tea is required to traverse through plurality of said drying chambers until the tea is completely dried up upto the desired moisture content. Thus, depending upon the no. of such drying chambers required, the length of the dryer and the power of the dryer may be varied to meet end user requirements. The microwave radiation is generated by means of microwave heating device magnetron. The electrical and electronic circuitry for the magnetron are preferably housed at the roof of the drying chamber. The system, in particular, the drying chamber(s) is further provided with means for exiting the water vapours and/or other particles released from said material during drying from said chamber(s). Preferably, the material from the feeder/hopper is allowed to fall in the conveyor means which is first adapted to move from left to right in said drying chamber ; a drop door provided adjacent the right end of said conveyor allow the thus primary dried material to fall on a further moving lower conveyor which run from right to left for further secondary drying of the material; a second drop door adjacent the left end of said lower conveyor adapted to allow drop of said dried material in a collecting bin. The conveyor is driven by ac motor means which is coupled to the conveyor driver shaft through a variable gear box. The conveyor is adapted to first move from left to right in said drying chamber and then downwards at the rightmost end to effectuate a lower conveyor movement from right to left. Thus by way of the above conveyor means a two stage drying of the material is possible. The thickness of the tea on the conveyor is controlled by separator means and to provide an even distribution of heating to the material plough means are provided to plough through the material on the conveyor. The details of the invention its objects and advantages are explained hereunder in greater detail in relation to non-limiting exemplary embodiments of the microwave heating device as per the accompanying figures wherein Fig. 1 is a schematic illustration of an exemplary embodiment of the microwave tea dryer of the invention for use in drying of tea. Fig. 2 is an illustration of another embodiment of the microwave tea dryer of the invention. As shown in figure 1, the fermented tea is allowed to fall in the feeder (1) either manually or through conveyor. At the bottom of the feeder, the tea fall on the conveyor (3) which moves from left to right direction into the drying chamber through two slits (16). The tea is carried into the drying chamber. The thickness of the tea on the conveyor is controlled by a spreader (2). To give an evenly distribution of heating to the tea the tea is ploughed by using two ploughs (8) resting slightly above the conveyor. The drying chamber is provided with microwave heating device i.e. magnetrons (9) at the roof. The electrical and electronic circuits for the magnetron is placed in a chamber (15). The conveyor is driven by an ac motor (6) which is coupled to the conveyor driver shaft through a variable gear box (7). The variable gear box makes the speed of the conveyor very slow (which can be varied). The conveyor moves downward at the rightmost end over two sprockets (4) for the tea to get dried fully, the conveyor speed is so adjusted that the tea falls through the 1st drop door (13) to the conveyor again. The bottom chamber also get heated to some extent due to the main chamber. Therefore the tea gets an extra time to be heated to some due to the chamber. Therefore, the tea gets an extra time to be heated if some water molecules are left, while travelling from right end to the left end. Finally the dried tea is collected in a collecting bin (10) through the 2nd drop door (14). Any extra tea spilling over is collected in a spill over bin (11). The water vapours and other particles gets released from the tea in the drying chamber must be ventilated out through the ventilating ducts (18) with the help of a fan (17). The feeder can be inspected by climbing through the steps (12). Reference is now invited to accompanying figure 2 which shows another embodiment of the microwave tea dryers of variable capacity and size depending upon the end user requirements. This is an optional design of the dryer when the microwave power required is very high. In case of higher microwave power requirement for large size of tea dryer, it may not be possible to install magnetrons of high power in a single cavity. In that case the power will have to splitted up into several parts. As shown in Fig. 2 in such case the microwave tea dryer can be provided with plurality of drying chambers or cavities (D, F) operatively connected to one another through the cavity joining section B, in whereby the tea to be dried is allowed to enter the first of said drying chamber for an initial drying followed by subsequent drying chambers for stagewise drying of the tea upto the desired moisture content. Each of the cavities is separated from the earlier preceding cavities by a drive cavity (G and E), which is designed to drive the conveyor belt and thus effect the transportation of the tea from one cavity to the other. The drive cavities G and E further comprise a substantially rectangular housing comprising the inner magnetron C, which heats up the main cavities as well as the drive cavities. The whole system is furthered powered by an external magnetron A adapted to heat up the tea travelling through the drive cavities and the main cavities D and F. Each of the drying chambers is provided with means of microwave radiation of desired power preferably by use of magnetrons. Thus by way of such modified dryer it is possible to have high powered drying such as using microwave power of 120K W by using 7 drying chambers each accommodating about 3 nos. of 6K W magnetrons. The specific no. of drying chambers and the power in each can be determined based on end user requirements. The above disclosed microwave tea dryer of the invention would provide for drying of material such as tea and the like by allowing the radiation to fall on the material to be heated after scattered by a fan. When the radiation hits a liquid molecule, it is vibrated and heat is produced. This heat dries up the liquid and other volatile compounds. Since the process of heating is by vibration due to radiation and not due to heat transfer mechanism, the efficiency is much more higher. The vibration does not take place if the material does not contain liquid. Hence the material is not unnecessarily heated in the absence of liquid i.e. water. In this case there is no any chance of overheating. This characteristic is very important for tea drying because in other type of tea dryers, extra precaution has to be taken so that tea is not over dried or burnt. It is thus possible by way of the microwave tea dryers of the invention to favour drying of tea with the following advantageous features : 1. Heat loss is less because the dry particles are never heated and only wet particles are heated. 2. Since heat is produced through electricity the efficiency is high. Moreover the microwave radiation can be strictly prevented from leaking out. 3. Since there is no fuel firing system, the drier will be free from noise. 4. Radiation does not cause air pollution, so free from air pollution. 5. The tea is free from being contaminated with fuel particles since heating is done by radiation, not by fuel. 6. Total time of drying is less than conventional dryers. The drier of the invention can be scaled up or down in as per capacity requirement. The optimum result is obtained by properly selecting the a) size of the conveyor b) speed of the conveyor c) total power of the magnetron The microwave tea dryer of the invention is thus a complete solution to the problem faced in the presently used dryers based on fuel fired heating. WE CLAIM: 1. A microwave tea dryer for drying of tea comprising: means for generating microwave radiation being a magnetron housed in a drying chamber (9) and allowing the thus generated radiation to fall on the tea to be dried and thereby effecting drying by vibration and consequential heating of the liquid volatile components in said tea to thereby dry said tea; means for regulated supply of the tea to the drying chamber such that the radiation generated vibrate and heat the liquid/volatile components of said tea comprising: (a) feeder/hopper (1) adapted to allow fall of tea on the top conveyor in said drying chamber and positioned adjacent to said means for generating microwave radiation; (b) means for controlling the thickness and speed of the material on the said conveyor comprising a separator means being a spreader (2); and (c) a plough means (8) adapted to provide an even distribution of heating to the tea and positioned just above the conveyors (3) so as to plough through the tea travelling on the conveyor; and means for collection of the thus dried tea, characterized in that said top conveyor is adapted such that initially the spread tea is first allowed to traverse through the said drying chamber for a first stage of primary drying and thereafter tea is allowed to fall on a further moving lower conveyor which runs in the reverse direction for further secondary drying of the tea such that a drop door (13) provided adjacent to the right end of said top conveyor allows the primary dried tea to fall on the further said moving lower conveyor, which runs in the reverse direction from said first conveyor as aforesaid and a second drop door (14) adjacent to the end of the said lower conveyor adapted to allow drop of said tea in a collecting bin (10) provided below. 2. A microwave tea dryer as claimed in claim 1 comprising : plurality of means for generating the said microwave radiation (C) housed adjacent to respective drying chambers (D, F); said plurality of drying chambers (D, F) operatively connected to one another and each said drying chamber having means for generating said microwave radiation ; means for regulated supply of the tea to be dried through said plurality of drying chambers such that radiation generated vibrate and heat the liquid/volatile components of said tea in stages in each said drying chamber to finally dry the tea to desired extent; and means to collect the thus dried tea. 3. A microwave tea dryer as claimed in anyone of claims 1 or 2 comprising a fan for exiting the water vapors and/or other particles released from said tea during drying from said chamber(s). 4. A microwave tea dryer as claimed in anyone of claims 1 to 3 wherein the tea to be dried is allowed to fall in the feeder either manually or through conveyor. 5. A microwave tea dryer as claimed in any of the preceding claims, wherein said lower conveyor means traverses through one or more bottom chamber(s) wherein heat from the drying chamber(s) positioned above said bottom chamber(s) also provides heat to the bottom chamber(s) for secondary heating of the material. 6. A microwave tea dryer as claimed in any of the preceding claims, comprising spill over bin for collecting extra tea spilling over. 7. A microwave tea dryer as claimed in any of the preceding claims, wherein the number of said drying chambers, the power of magnetrons and size of the dryers are selected based on the end requirement. 8. A microwave tea dryer for drying of tea substantially as hereindescribed and illustrated with reference to the accompanying figures. A microwave tea dryer comprising means for generating microwave radiation which is adapted to fall on tea to be dried whereby the radiation hits the liquid molecule/volatile compound to thereby vibrate and generate heat to cause drying of the tea. The dryer utilizes a process of heating by vibration by means of microwave radiation and not by heat transfer mechanism to achieve higher efficiency. Importantly, since in the tea dryer such vibration does not take place if the material does not contain liquid, there is no unnecessary heating in the absence of liquid i.e. water and there is also thus no chance of overheating of the tea. The tea dryer is free of noise during operation and is environment friendly apart from protecting the material from any atmospheric/fuel contamination. The tea dryer is directed to provide for simple, cost- effective and efficient drying of materials/substances such as tea and the like without affecting the character and quality of the tea. |
|---|
| Patent Number | 216876 | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Indian Patent Application Number | 39/CAL/2001 | |||||||||
| PG Journal Number | 12/2008 | |||||||||
| Publication Date | 21-Mar-2008 | |||||||||
| Grant Date | 19-Mar-2008 | |||||||||
| Date of Filing | 23-Jan-2001 | |||||||||
| Name of Patentee | DR. MANABENDRA BHUYAN | |||||||||
| Applicant Address | DEPT. OF ELECTRONICS, TEZPUR UNIVERSITY | |||||||||
Inventors:
|
||||||||||
| PCT International Classification Number | F 26 B 23/08 | |||||||||
| PCT International Application Number | N/A | |||||||||
| PCT International Filing date | ||||||||||
PCT Conventions:
|
||||||||||