Thin-layer mathematical modelling of maize in a biomass-powered inclined bed dryer

Abstract

In this study, the drying kinetics of maize dried in a biomass-powered inclined bed dryer were studied using ten (10) thin-layer mathematical drying models. The drying system recorded an average plenum temperature of 73.54 oC during the drying experiment compared to an average ambient temperature of 28.41 oC. Maize grains with an initial average moisture content of 23.25 % on a wet basis were reduced to 13.61 % average final moisture content over a drying period of 2 hours 40 minutes. The results revealed a moisture extraction rate, drying rate, and drying efficiency of 6.70 kg/h, 9.50 kg/h, and 71.37 %, respectively. The two-term model best describes the thin-layer drying kinetics of maize in the biomass-powered inclined bed dryer based on the coefficient of determination (R2) and root mean square error (RMSE) values of 0.998 and 0.00738, respectively. The two-term model showed a better fit between the experimental and the predicted moisture ratios. The drying process occurred in the falling rate period with an effective moisture diffusivity of 4.65x10-9 m2/s and activation energy of 21.31 kJ/mol. The two-term model was able to imitate the behaviour of the drying process of maize in the drying system. The model would assist in predicting the drying time for different moisture contents of maize in the scale-up of the drying system and, accordingly, help farmers and agro-processors in planning drying schedules. The drying kinetics of other staples like cassava and rice are recommended for further studies using the biomass-powered inclined bed dryer.