Determination of kinetic parameters and thermodynamic properties for Ash (Fraxinus) wood sawdust slow pyrolysis by thermogravimetric analysis

Ash (Fraxinus) wood sawdust pyrolysis under nitrogen was conducted using 2, 5, 10, 15, and 20°C/min heating rates. Friedman and Starink methods were used for kinetic analysis while y(α) master plots were used for pyrolysis mechanisms prediction. The mean activation energy were 198 and 202 kJ/mol for Friedman and Starink, respectively. The master plots predicted that the pyrolysis process could be a combination of diffusion, geometrical contraction, nucleation, and reaction order models. The pre-exponential factors were in the range 1012 to 1019 s−1. Gibbs free energy was 180 −185 kJ/mol. The entropy values were negative up to α = 0.75 indicating high orderliness of products relative to reactants but changed to positive at higher conversions implying likely disorderliness of the products compared to reactants. The calorific value of Ash (Fraxinus) wood sawdust was 18.3 MJ/kg.