| Title of Invention | SHELL FIRED COPRA DRYER |
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| Abstract | A natural convection copra dryer was designed and developed and performance evaluated to dry coconut. The capacity of the dryer developed is 1000 nuts per batch. The drying air temperature in the drying chamber is 80 oC. Coconut shell is used as fuel in a specially designed burning chamber. The thermal efficiency is in the range of 25.25 to 26.4 % which indicates good performance of the dryer. The quality of copra obtained is light brown in colour which fetches good price in the market. The burner designed generates heat for 5 hours without tending and the heat is retained for one more hour. The average drying.time is 23.5 h. |
| Full Text | This invention relates to development of copra dryer with coconut shell as the source of fuel. The following are the main components. Another aspect of the invention relates to the development of twin burning chamber which can produce heat for 6 h without tending. Following are the main components of the copra dryer. Description of the dryer The dryer consists of a drying chamber, a burning chamber, a plenum chamber and ventilation holes. This dryer is fabricated using locally available materials such as asbestos sheet, galvanized iron sheet, mild steel angle and fire resistant plywood. Asbestos cement sheet is provided only at those places where the copra does not come into direct contact. The contact areas (sides) of the drying chamber with copra are provided with heat resistant bamboo plywood. The shape of the burning chamber is designed to avoid the flame and flue gas coming into direct contact with the copra (Fig. 2). This is one of the constraints reported by the farmers. As smoke does not come into contact, the quality of copra obtained is good. Air inlet chamber This is the most important part of the dryer since fresh air enters into the dryer. A 20 cm opening from the ground level is provided all around the dryer. Hinges are provided to regulate the supply of fresh air in to the plenum chamber. The air, entering from the inlet passes to the plenum chamber through the passage provided and gets heated up by the heat radiated from the heating chamber. The hot air being lighter in weight raises and passes through the drying chamber. Heating cum heat exchanging chamber Butterfly valves are provided in the exhaust pipes to control the entry of fresh air in to the dryer thus controlling the inside temperature of the dryer. This in turn regulates the entry of air for combustion and thus controls the rate of combustion of fuel so that the fuel burns slowly maintaining the temperature. Initially only one heating chamber was provided but during tests conducted it was found that due to improper burning smoke was getting accumulated in the heating chamber because of which the shells were not burning properly. Hence two fuel chambers, instead of one was provided. Also it was found during the tests that after de-shelling, the volume of copra almost reduced to half the volume of drying chamber. Hence after de-shelling the farmer can use only one heating chamber which in turn will reduce the quantity of fuel required. Also if the farmer has lesser number of nuts than the capacity of the dryer he can operate only one heating chamber there by reducing the cost of drying. Plenum chamber The empty space provided above the heating chamber is known as plenum chamber. A door has been provided mainly for cleaning the top surface of burning chamber. During loading and unloading lot of coconut pith and small piece:; of fibre adhering to the shell fall on the drying chamber. This has to be cleaned periodically to avoid its burning other wise it will produce smoke and contaminate the copra quality. Also in case of sudden rise in drying air temperature, the door can be opened so that fresh air enters there by bringing down the temperature. Drying chamber The top portion of the dryer is known as drying chamber. The dimensions of the drying chamber is 2.25 m (L), 1.5 m (B) and 0.30 m (H).The weld mesh for stacking copra is made of 10 gauge, 25 x 25 mm size weld mesh. On one side of the drying chamber a door is provided for easy loading and unloading the coconuts in to the dryer and into the de-shelling chamber, the height of which is lower than the dryer. The sides of the burning chamber is covered by 6 mm thick bamboo plywood sheets, and all other parts of the dryer is covered with 4 mm thick asbestos cement sheet to withstand high temperatures and to reduce the overall cost of the dryer. Fuel preparation Eighty half shells are required in each tray to make one row. The coconut shells are interlocked and laid on the tray. The hollow end of the row of shells is ignited (a little kerosene being added to help initial burning). When the shells begin to burn well and without smoke, the tray is pushed inside the heating chamber. The shells burn uniformly \>y the incoming air for which ventilation holes are provided on the door. The number of holes required is standardized based on tests conducted. Additional ventilation door is provided with provision to open and close in case of necessity and to retain the heat once the shells are burnt completely. Firing the dryer Each fuel tray produce heat for 6 h with a temperature of about 80 - 82 °C. Generally after about 6 h, when the temperature drops below 60 °C, the fuel trays are removed from the dryer, cleaned and reloaded with fuel, refired and replaced in to the respective burning chambers. About 4 loads of fuel are required to dry the copra to about 6.25 % d.b. moisture content. The heat generated by burning of the fuel heats the heating chamber. The air above heating chambers gets heated up and moves upwards through the layers of fresh coconut kernel and the hot air laden with moisture escapes from the top of the drying chamber in to the atmosphere, and fresh air enters through the ventilation hole's provided at the bottom. (Fig. 1).This phenomenon is carried our with the help of natural convection. Prior Art: Drying is one of the important post harvest operations for all plantation and other crops. Quality drying can produce quality end products. Sun drying, drying with solar dryers, indirect dryers suc-h as CPCRI small Holders dryer, forced hot air circulation dryers of large capacity are available in the market. Each type has got its own advantages and disadvantages. The main advantage of this dryer is that fuel has to be loaded once in six hours. No electrical energy has been used in this dryer. The unique burning chamber designed and developed is the most unique feature of this drye . Heating takes place due to natural convection. The average temperature in the drying bin is automatically maintained at 72 degree centigrade. As a iesult the risk of spoilage is reduced both during the actual process and subsequent storage. The higher temperatures attainable are also a deterrent to insect and microbial infestation. Additionally protection against dust, insects and pests is enhanced by drying in this dryer as the sides of the dryer is closed. Since smoke does not come into contact with the copra the quality obtained is very good. Most other dryers developed require frequent re-fuelling which has been completely eliminated in this dryer. The drying time is also very less as compared to other dryers developed. Detailed invention and application: This dryer is used to dry fresh fully matured split coconut in to copra. The design drawings are given in Fig. 1 and 2. Before conducting an experiment, the burner was loaded with fuei and charged for 30 minuts till the desired drying air temperature attained steady state. The dryer was tested for production of copra during January - March 2003. For making copra, the coconuts are broken into two halves and kept inverted for 4-5 minutes in order to drain the water. After the coconut water is completely drained, the cups are stacked in the drying chamber, layer by layer in such a way that in the first two layers, the kernels faced upwards (U) and in the subsequent layers, the kernels faced downwards (∩). The cups in adjacent layers are stacked in a brick-laying-fashion, one overlapping the other. Drying is carried out continuously for 24'h by firing the burner four times at intervals of approximately 6 h. The moisture content of coconuts reduces exponentially as the drying time increases. The percentage moisture content available is more in the case of coconuts placed in the top layer as compared to bottom layer at the drying air temperature of 80 °C for the same drying time. It took 22, 21, 26 and 25 h to dry coconut from the average initial moisture content of 90.14, 88.34, 92.12 and 86.23 to 6.25 % d.b., respectively in the four drying tests conducted. The average mean relative humidity of ambient air was 74.12, 72.56, 86.45 and 84.12 %, respectively in the four tests. The average time taken to reduce the moisture content from 89.21 % d.b to 6.25 % d.b is 23.5 h where as in the small holders dryer developed by CPCRI it took 36 to 40 h there by reducing the total drying time by 12.5 to 16.5 h. Thus almost two batches of copra can be dried in the time taken by small holders dryer. In case of sun drying it takes 6-7 days where as in this dryer copra can be dried in one day. Thus there is a saving of 6 days off time for the fanners during which they can atrend to other useful works. Also to dry 1000 nuts the total area required is only 3 m2 where as in case of sun drying it required a minimum of 12 m open drying yard which is hardly available with the farmers under Kerala conditions. Performance of copra dryer The performance data of the dryer is given in Table 1. From the Table 1 it can be seen that at full load the thermal efficiency was in the range of 25.25 to 26.4 % which indicates good performance of the dryer. It can be seen from the Table 1 that the thermal efficiency reduced to 9.41 % at 50 % capacity indicating that the dryer should be used at full capacity only. The quantity or fuel consumed was 86 kg at 50 % load where as it was in the range of 60 to 64 kg in case of full load indicating that the hot air escaped into the atmosphere at a faster rate there by increasing the quantity of fuel required. The heat utilization factor was in the range of 0.17 to 0.19 indicating low heat utilization which is very common in indirect type oi" dryers but the coefficient of performance was very high in the range of 0.80 to 0.86 indicating high efficiency of the dryer. Quality characteristics of copra dried in copra dryer The oil content is in the range of 62.48 to 63.55 %. It indicates that there is no loss of oil for the copra dried at drying air temperature of 80 °C (Table 2). The oil content reported for West Coast Tall variety is in the range of 60 to 68 %. The average free fatty acid content is 0.0865. The average acid value, peroxide value and saponification number are 0.265, 0.3375 and 253 respectively. The colour of copra is light brown as smoke did not come into contact with the kernel and the smell and taste are typical indicating no loss of the natural aroma of copra. 4. We claim 1. A copra dryer to dry split fresh matured coconut in copra comprising of a drying chamber (fig. 1 part 12), burning chamber (fig. 1 part 30), fuel tray (fig. 1 part 3), smoke chamber (tig. 1 part 2) and exhaust pipe(fig 1 part 7). 2. A copra dryer to dry split fresh matured coconut in copra as claimed in claim 1, where in the smoke chamber (fig 1 part 2) is connected to the burning chamber (fig 1 part 10) using Galvanized Iron pipe of both the burning chamber. 3. A copra dryer to dry split fresh matured coconut in copra as claimed in claim 1, where in the exhaust pipe (fig 1 part 7) is connected to the smoke chamber (fig 1 part 2) for release of flue gas. 4. A copra dryer to dry split fresh matured coconut in copra as claimed in claim 1, where in the drying chamber (fig. 1 part 12) is made of weld mesh, bamboo plywood and Mild Steel angle. 5. A copra dryer to dry split fresh matured coconut in copra as claimed in claim 1, where in the burning chamber (fig 1 part 10) is made of Mild Steel angle in two compartments. 6. A copra dryer to dry split fresh matured coconut in copra as claimed in claim 1, where in fuel tray (fig 1 part 3) is made of Mild Steel angle and Mild Steel sheet to hold 80 half coconut shells. |
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| Patent Number | 269186 | ||||||||
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| Indian Patent Application Number | 1127/DEL/2005 | ||||||||
| PG Journal Number | 41/2015 | ||||||||
| Publication Date | 09-Oct-2015 | ||||||||
| Grant Date | 07-Oct-2015 | ||||||||
| Date of Filing | 04-May-2005 | ||||||||
| Name of Patentee | INDIAN COUNCIL OF AGRICULTURAL RESEARCH | ||||||||
| Applicant Address | KRISHI BHAWAN, DR.RAJENDRA PRASAD ROAD, NEW DELHI-110001, INDIA. | ||||||||
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| PCT International Classification Number | F26B 11/00 | ||||||||
| PCT International Application Number | N/A | ||||||||
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