A comparative study of thermal and combustion kinetics for raw and bio-chars of eucalyptus wood and bark

This study investigates thermal and combustion kinetics of raw and bio-char samples of eucalyptus wood and bark. Raw samples of eucalyptus wood and bark were subjected to pyrolysis at temperatures of 300, 350, 400, and 450 degrees C. The maximum mass yield was obtained at 350 degrees C for both bio-char samples of wood and bark. Gross calorific value, proximate, ultimate, and chemical analyses of the raw and their derived bio-chars showed high energy yield of bio-chars as compared to raw samples. Thermal analysis of raw and their respective bio-chars was also studied using thermogravimetric analysis in air at heating rates of 25, 35, and 45 degrees C min(-1). Raw wood and bark in comparison to their bio-chars showed delayed ignition that resulted in increase of ignition, peak, and burn-out temperatures. Mean reactivity of raw and bio-char samples was obtained using Ghetti model that showed higher reactivity of raw samples than bio-chars. Kinetic parameters including activation energy and order of reaction were found using Arrhenius model. For different heating rates, activation energies lied in the range of 61-108 kJ mol(-1) (wood) and 42-79 kJ mol(-1) (bark). Higher carbon contents in the bio-char samples resulted in higher activation energies than raw samples. This increasing carbon contents trend also furnished increase activation energies of bio-chars.