DEVELOPMENT AND PERFORMANCE EVALUATION OF A BATCH-TYPE WASTE FIRED DRYER FOR COCOA

Abstract

The project work depicts the development and performance evaluation of a batch-type waste fired dryer for cocoa. Drying is an important step in the postharvest processing of cocoa beans. Cocoa beans are dried after fermentation in order to reduce the moisture content from about 40 per cent to about 6-7 per cent At present drying of cocoa is done mostly by sun drying. Sun drying of cocoa beans has many disadvantages viz., it is weather dependent, exposure to dust, molds and pests, longer drying time etc. Electric dryers are found comparatively expensive with regard to consumption of electricity and brought very little profit to the farmers. Hence A batch-type cocoa bean dryer was developed and fabricated in the Kelappaji College of Agricultural Engineering and Technology, Tavanur workshop. The cocoa used for testing were procured from progressive farmers at Meloor Chalakudy, Thrissur district and Palachode, Malappuram district. The dryer consists of a combustion chamber, drying chamber, fins, chimney, handle, feed inlet, product outlet, grate, and frame. Biomass was weighed and stacked inside the grate. The grate was then placed inside the combustion chamber and the biomass was ignited. The cocoa beans were fed into the drying chamber through the feed inlet. The heated air entered the drying chamber through the perforations made on the drying chamber. While hot air passing through the moist cocoa beans, it absorbed moisture and came out through the exhaust port After the beans are dried to required moisture content, the dried cocoa beans were collected through the product outlet by rotating the handle in clockwise direction. The evaluation of the machine was conducted at at three different temperatures viz., 50°C, 60°C, 70°C. The capacity of dryer was found to be 12 kg. The free fatty acid content measured at different drying temperatures 50°C, 60°C and 70°C were 1.49, 1.62 and 1.85 per cent, respectively. Time required for drying at 50°C, 60°C and 70°C were 8, 6 and 5 hours respectively. Efficiency of dryer at different drying temperatures50oC, 60°C and 70°C was 24.61, 19.95 and 17.02 per cent, respectively. The energy requirement for operating the dryer was found to be 36.26 MJ/hour. The optimization of drying temperature was done based on the physico-chemical quality of the dried cocoa beans i.e. free fatty content. Based on the results, it was understood that the cocoa beans dried at 50°C was found to be superior among the other treatments. According to Dand (1997), the FFAs levels should be less than 1.75% in dried cocoa beans. Among the experiments, the free fatty acid content of the cocoa beans dried at temperatures 50°C and 60°C was within the permissible limits. Hence, by considering the economic aspects of drying, drying temperature at 60°C was selected as the optimised drying temperature. The developed cocoa bean dryer is a compact as well as portable machine. It is found efficient in drying cocoa beans and will be benefitted to small and marginal cocoa growers.