COMPARISON OF PYROLYSIS KINETIC MODELS FOR THERMOGRAVIMETRIC ANALYSIS OF BIOMASS

Pyrolysis kinetics of biomasses was studied in a thermogravimetric analyzer. Effects of biomass type (cassava pulp residue, palm kernel cake, palm shell, coconut shell and longan fruit seed), particle size (106-1,325 mu m) and heating rate (5-40 degrees C/min) on the thermal decomposition behavior were investigated and the pyrolysis kinetic data were tested with five different models to confirm their validities. The major decomposition of all biomasses occurred in the range of 250-400 degrees C and their first derivative curves (DTG) showed different characteristics of one or two major peaks depending on the type of biomass. Differences in particle size gave almost no effect on the fractional weight remaining and its first derivative but heating rate influenced strongly the range of decomposition temperature and decomposition rate. On model fitting, the best fitting was observed for the two parallel reactions model. The one-step global model assuming nth order reaction and the two-step consecutive reaction model with provision of stoichiometric coefficient gave satisfactory prediction. However, the one-step global model assuming 1st order reaction and the two-step consecutive-reaction model of Guo and Lua showed relatively large deviation between predicted and experimental results.