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 degrees C to 140 degrees 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 degrees C up to 140 degrees 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 (Marquart's 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 Fick's second law of diffusion. They varied from 5.958 x 10(-9) m(2)/s to 1.589 x 10(-8) m(2)/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. (c) 2007 Elsevier B.V. All rights reserved.