Pyrolysis behaviors and kinetic studies on Eucalyptus residues using thermogravimetric analysis

The pyrolysis behaviors and kinetics of Eucalyptus leaves (EL), Eucalyptus bark (EB) and Eucalyptus sawdust (ESD) were investigated by using thermogravimetric analysis (TGA) technique. Three stages for EL, EB and ESD pyrolysis have been divided using differential derivative thermogravimetric (DDTG) method and the second stage is the main pyrolysis process with approximately 86.93% (EL), 88.96% (EB) and 97.84% (ESD) weight loss percentages. Kinetic parameters of Gaussian distributed activation energy model (DAEM) for EL, EB and ESD pyrolysis are: distributed centers (E-0)of 141.15 kJ/mol (EL), 149.21 kJ/mol (EB), 175.79 kJ/mol (ESD), standard deviations (sigma) of 18.35 kJ/mol (EL), 18.37 kJ/mol (EB), 14.41 kJ/mol (ESD) and pre-exponential factors (A) of 1.15E+10 s(-1) (EL), 4.34E+10 s(-1) (EB), 7.44E+12 s(-1) (ESD). A new modified discrete DAEM was performed and showed excellent fits to experimental data than Gaussian DAEM. According to the modified discrete DAEM, the activation energies are in ranges of 122.67-308.64 kJ/mol, 118.72-410.80 kJ/mol and 108.39-192.93 kJ/mol for EL, EB and ESD pyrolysis, respectively. The pre-exponential factors of discrete DAEM have wide ranges of 4.84E+13-6.12E+22 s(-1) (EL), 1.91E+12-4.51E+25 s(-1) (EB) and 63.43-4.36E+11 s(-1) (ESD). The variation of activation energy versus conversion reveals the mechanism change during pyrolysis process. The kinetic data would be of immense benefit to model, design and develop suitable thermo-chemical systems for the application of Eucalyptus residues. (C) 2015 Elsevier Ltd. All rights reserved.