Isothermal drying kinetics of paddy using thermogravimetric analysis

The isothermal drying kinetics of paddy with three initial dry basis moisture content of 17.18, 21.05 and 30.12% have been studied by thermogravimetric analyzer. The results indicated that the final moisture content of the three samples with initial moisture content of 17.18, 21.05 and 30.12% decreased to 4.61, 5.63 and 7.61%, respectively, under the drying temperature of 50 °C. Moreover, the peak drying rate of the three samples speeds up from 1.41% min−1 to 2.18% min−1 with the increase in initial moisture content. Subsequently, five types of drying models were compared to determine the goodness of fit of the different experimental data generated under the drying temperature of 50 °C for the three samples. It is showed that correlation coefficients (R2) determined by Midilli et al. model for the three samples were larger than that in other four models, indicating that the model could fit the experimental data perfectly. Different drying temperature of 40, 50, 60 and 70 °C was selected for the calculation of the effective moisture diffusivity ranging from 3.9747 × 10−10 to 5.2519 × 10−10 m2s−1, which was eventually used to determine the activation energy. The results show that the activation energy of the three samples is 3.92, 5.23 and 6.82 kJ mol−1, respectively.