DETERMINATION OF REACTION-KINETICS OF WHEAT STRAW USING THERMOGRAVIMETRIC ANALYSIS

Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) have been conducted on straws from four different wheat varieties (Absolvant, Max, Monopol, and Vuka) in an oxidizing atmosphere of 15% oxygen and 85% nitrogen. The thermal degradation of wheat straw was studied from ambient temperature to 700-degrees-C using a heating rate of 20-degrees-C/min. By applying thermoanalytical techniques to reaction kinetics, the order of reaction, preexponential factor, and energy of activation were determined from thermogravimetric curves. Two distinct reaction zones were observed on the TGA and DTA curves. Because of the two-step nature of the thermal degradation of wheat straw, it was essential to determine the kinetic parameters for each zone separately. The thermal degradation rate of the first zone was significantly higher than that of the second zone for all wheat straw varieties. Lower activation energy and preexponential factors were observed for wheat straws as compared to cellulose owing to the high inorganic material and silica contents of the wheat straw.