Kinetic Analysis of Thermal Stability and Activation Energies of Agricultural Waste Residues Using Flynn-Wall-Ozawa and Coats-Redfern Models

Abstract

The objective of the study was to determine the thermal degradati on mechanisms and apparent activation energies of agro waste residues using thermo gravimetric analysis. Thermal degradation behaviors of corncob (CCF), rice hull (RHF), walnut shell (WSF) and oil palm (OPF) fibrous wastes under N 2 atmosphere were evaluate d to derive their kinetic parameters at various heating rates of 5, 10, 20 and 40oC/min. Kinetic parameters were calculated using Flynn -Wall-Ozawa (F.W.O) and Coats Redfern models. The thermo gravimetric analysis (TGA) results showed that activation energies of the fibers varied significantly with the extent of degradation indicating a multistage mechanism involving a variety of compounds. Higher heating rate affected not only the temperature of maximum weight loss, but also the activation energies and degr adation conversions of the agro fibers during decomposition. Activation energies of the agro waste residues decomposition appeared to peak around 40 -50% conversion. The apparent activation energies (Ea) of the agro waste residues according to (F.W.O) and Coats Redfern models was found to be in the range between 184.74/183.87 kJ/mol for rice hull, 184.18/180.73 kJ/mol for walnut shell, 162.37/161.33 kJ/mol for corncob and 141.64/140.54 kJ/mol for oil palm fiber.