PYROLYSIS KINETICS OF ALMOND SHELLS AND OLIVE STONES CONSIDERING THEIR ORGANIC FRACTIONS

The kinetics of thermal decomposition of two lignocellulosic materials (olive stones and almond shells) were studied using dynamic TG at hea ting rates between 2 and 25 K min(-1) at atmospheric pressure. Differe nt kinetic models were tested, that consider that the thermal decompos ition of lignocellulosic materials can be grouped in two or three over all processes (each one being the result of a great number of reaction s) corresponding to the hemicellulose, cellulose and lignin decomposit ions. The best results were obtained with a model that considers that the biomass decomposes via three independent reactions. There is a qua litative agreement between the decomposition of hemicellulose, cellulo se and lignin with the peaks observed in the TG-DTG diagram, but the s imple addition of the kinetics of isolated compounds cannot satisfacto rily reproduce the kinetic behaviour of any raw material, and conseque ntly some interactions must exist between the fractions considered. (C ) 1997 Elsevier Science B.V.