Mathematical modelling of thin-layer infrared drying of wet olive husk

The thin-layer infrared drying behaviour of wet olive husk (WOH) was experimentally investigated at the temperature range from 80 °C to 140 °C. The drying rate was found to increase with temperature, hence reducing the total drying time. In particular, as drying temperature was raised from 80 °C up to 140 °C, the time necessary to reduce the moisture content of the sample from 91.97 wt% down to 8.69 wt% (dry basis) changed from 105 min to 35 min. Using a non-linear regression (Marquartʹs method) and multiple regression analysis, a mathematical model for the thin-layer infrared drying process of WOH was proposed. The values of the diffusivity coefficients at each temperature were obtained using Fickʹs second law of diffusion. They varied from 5.958 × 10−9 m2/s to 1.589 × 10−8 m2/s over the temperature range. The temperature dependence of the effective diffusivity coefficient was described following an Arrhenius-type relationship. Activation energy for the moisture diffusion was determined as 21.30 kJ/mol.