Modeling and simulation of pneumatic drying of coconut (Cocos nucifera L.) meat

The primary purpose of this study was to test the technical feasibility of pneumatic drying for coconut meat particulates. A thin-layer drying experiment using the Box and Bhenken three-level incomplete factorial design was conducted to determine the drying constants of the coconut meat particulates. The Exponential drying model best described the drying behavior of the coconut meat particulates than the Page model. The drying constants n and k were determined using the regression and response surface analysis by StatSoff (1999) and were found to be highly influenced by the initial moisture content and particle size. Based on the drying curves, the properties of the coconut meat such as the mass diffusivity , energy of activation and the drying equilibrium moisture (DEMC) content were established. For the temperature range of 70 deg C to 110 deg C and in combination with different particle sizes and initial moisture contents, the DEMC of the coconut meat ranged from 6.1 percent to 1.1 percent on wet basis. The coefficient of diffusivity ranged from 5.60 x 10 sup-10 sq m/sec to 2.202 x 10 sup-9 sq m/sec while the energy of activation was 897 kJ/kg. The time to dry to a final moisture content of 6 percent for particulates with 50 percent to 30 percent initial moisture content, particle size of 1.2 mm to 2.0 mm and air temperature of 90 deg C to 110 deg C, was predicted to range from 2.41 to 12.14 mins. The specific thermal energy consumption ranged from 48 mJ/kg to 61 mJ/kg for drying without exhaust air recirculation while 4.5 kJ/kg to 9.1 kJ/kg when exhaust air was recirculated. Thermal energy efficiency was 4 percent to 5 percent and 27 percent to 57 percent when drying air was no recirculated and when recirculated, respectively. Electrical energy consumption of the system was about 1.9 kwhr/kg. The results showed that the developed drying simulation model was sufficiently accurate to predict the performance of the pneumatic drying of coconut meat particulates.