Determination of effective moisture diffusivity and activation energy for drying of powdered peanut shell under isothermal conditions

Abstract

In this study, the effect of drying temperature, from 50 °C to 90 °C, on the drying characteristics of powdered peanut shell was investigated, and an isothermal procedure was used to determine the moisture diffusivity and the activation energy. All the experiments were performed using a thermogravimetric analyzer (TGA) for rapidly achieving the isothermal condition and accurately recording the mass loss of the sample. With increasing drying temperature, the drying rate increased and the drying time decreased. A short rising rate period was found in all drying processes due to increasing temperature of the sample in the beginning of drying. The predicted values by the diffusion model based on Fick's second law were in good agreement with the experimental data obtained from the falling rate period. The values of effective moisture diffusivity ranged from 9.60×10-9 to 2.26×10-8 m2/s, and the activation energy was determined to be 21.2 kJ/mol.