Thermogravimetric analysis of walnut shell as pyrolysis feedstock

Thermal degradation behavior and kinetics of a biomass waste material, namely walnut shell, were investigated by using a thermogravimetric analyzer. The desired final temperature of 800 A degrees C was achieved at three different heating rates (2, 10, and 15 A degrees C min(-1)) under nitrogen flow (50 mL min(-1)). The TG and DTG curves exhibited three distinct zones that can mainly be attributed to removal of water, decomposition of hemicellulose + cellulose, and decomposition of lignin, respectively. The kinetic parameters (activation energy, pre-exponential factor, and reaction order) of active pyrolysis zone were determined by applying Arrhenius, Coats-Redfern, and Horowitz-Metzger methods to TG results. The values of activation energies were found to be between 45.6 and 78.4 kJ mol(-1). There was a great agreement between the results of Arrhenius and Coats-Redfern methods while Horowitz-Metzger method yielded relatively higher results. The existence of kinetic compensation effect was evident.