Low temperature pyrolysis of wood waste materials

Abstract

The pyrolysis of jack pine bark, jack pine sawdust, and cellulose powder has been studied by thermogravimetric (TG), and isothermal weight-loss methods in both inert and oxidizing atmospheres. The effects of particle size, solvent extraction, and a number of additives on the low temperature pyrolysis of jack pine bark have also been examined. Samples were analysed by low-temperature gas adsorption and the bark characterized by infrared spectroscopy. Residues were analysed for CHN contents and structural changes which occurred on heating were examined by scanning electron microscopy. The TG characteristics of bark were affected only slightly by particle size, solvent extraction, and additives. Isothermal decomposition data for bark and sawdust were similar and closely resembled established kinetic expressions associated with inorganic decomposition reactions controlled by diffusion processes. The data for cellulose were described by at least tv70 kinetic stages with the second or principal region resembling a standard kinetic expression for a phaseboundary controlled reaction. The pyrolysis data were found to fit a reaction rate compensation curve, often associated with oxidation processes but more generally with heterogeneous catalytic reactions. The compensation curve also relates the kinetic parameters found by other workers for a large variety of wood-derived materials.