 Suranaree J. Sci. Technol. Vol. 7 No. 4; Oct - Dec 200 COMPARISON OF PYROLYSIS KINETIC MODELS FOR THERMOGRAVIMETRIC ANALYSIS OF BIOMASS Piyarat Weerachanchai 1 , Chaiyot Tangsathitkulchai 1,* and Malee Tangsathitkulchai 2 Received: Oct 26, 2010; Revised: Dec 20, 2010; Accepted: Dec 20, 2010 Abstract 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 µm) and heating rate (5-40°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°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 n th order reaction and the two-step consecutive reaction model with provision of stoichiometric coefficient gave satisfactory prediction. However, the one-step global model assuming 1 st order reaction and the two-step consecutive-reaction model of Guo and Lua showed relatively large deviation between predicted and experimental results. Keywords: Pyrolysis, biomass, TGA, DTG, pyrolysis kinetic parameters Introduction Pyrolysis is defined as a thermal degradation process of carbonaceous materials in the absence of oxygen. It is an important thermal conversion process being the first step of combustion and gasification (Bridgwater, 2003). In addition, it is widely applied in chemical industries, for example, for the preparation of char as a precursor for the production of activated carbon, for cracking medium weight hydrocarbons of petroleum oil to produce lighter fractions of gasoline, etc (Answers Corporation, 2009). Thus, fundamental knowledge on thermal behavior of pyrolysis is a prerequisite for the design and optimization of various thermal conversion processes. Data on pyrolysis kinetics of lignocellulosic 1 School of Chemical Engineering, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand. Tel.: 0-4422-4263, Fax: 0-4422-4609. E-mail: chaiyot@sut.ac.th 2 School of Chemistry, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand. * Corresponding author Suranaree J. Sci. Technol. 17(4):1-14