Drying Characteristics of Powdered Wheat Straw and I ts Mathematical Modeling

Abstract

The objective of this research was to study the dry ing characteristics of powdered agricultural residues. Drying experiments of wheat straw ( Triticum aestivum ) were conducted at four temperatures of 50, 60, 70, and 8 0°C by a thermogravimetric analyzer. Drying temperature had a significant effect on the moisture change and drying time. There was no constant drying rate period, but a sho rt rising rate period was evident for all drying process due to increasing temperature of the sample at the beginning of drying. Six mathematical models were selected to describe t he drying characteristics of wheat straw. The goodness of fit was evaluated by the coe fficient of determination (R 2 ), the reduced chi-square ( χ χχ χ 2 ), and the root mean square error (RMSE). Midilli et al. model was found to be the best for modeling the experimental data. The values of effective moisture diffusivity of wheat straw dried at 50, 60, 70, and 80°C were calculated to be 1.13 × ×× × 10 -8 , 1.48 × ×× × 10 -8 , 1.66 × ×× × 10 -8 , and 2.29 × ×× × 10 -8 m 2 s -1 , respectively. Keywords: Biomass, Effective moisture diffusivity, Isotherma l condition, Midilli model, Thermogravimetric analysis.