MODIFICATION AND PERFORMANCE EVALUATION OF A MAIZE DRYING MACHINE

Abstract

Maize is a staple food, having an average post-harvest loss of 43-45 % per annum, due to high moisture content in the material. To minimize this effect, Modification and performance evaluation of a maize drying machine was carried out with the aim of achieving efficient drying of maize to safe moisture content. Steam energy of heated air, which prevented the product from burning and dis -colouration was employed in place of band heaters. The performance evaluation of the dryer was carried out using maize purchased from Agricultural Development Programme (ADP) in Ikole- Ekiti, Ekiti State as sample. The machine was tested under three feed rates; 120 kg/h, 180 kg/h, and 240 kg/h, temperatures; 120 0C, 160 0C, 200 0C and different speed of 6.6, 12.8, and 19 rpm. The machine optimum drying efficiency of 83.3 % and conveyance efficiency of 97.9 % were recorded for the product at 160 0C, 6.6 rpm and 180 kg/h feed rate, with material loss of 0.36%. The highest material loss was found as 12.9% at a temperature of 200 0C, speed of 19 rpm and feed rate of 240 kg/h. The product was dried from 27.8% to 13.7% wet basis at 160 0C, 6.6 rpm and 180 kg/h feed rate. Hence, feed rate, speed and temperature which were the evaluation parameters have significant effect on the performance of the machine. The experiment shows that, as the temperature and speed increased, the conveyance efficiency decreased, due to linear expansivity of the metal. The temperature of 160 0C, with the speed of 6.6 rpm and feed rate of 180 kg/h shows the optimum performance of the machine evaluated. However, desirability of 0.812 from the optimal solution (3-D surface response), suggested that the machine performance could be optimized at a certain condition of 6.6 rpm, 180.64 0C and 190.85 kg/h.