Kinetic study of biomass pellet pyrolysis by using distributed activation energy model and Coats Redfern methods and their comparison

In this study, the pyrolysis behavior and kinetics of raw biomasses and their pellets were studied by Coats Redfern and DAEM methods. The results demonstrated that the similar activation energies obtained by both methods confirmed accuracy of the kinetics calculation. The activation energy of the pellets was 132.49-232.44 kJ mol^-1, slightly higher than those of raw biomasses, which was 120.58-210.55 kJ mol^-1. The results from Coats Redfern method showed that the pyrolysis of all the samples were controlled by mass and heat diffusion. DAEM revealed that the activation energies of the pellets were higher than those of raw biomasses during hemicellulose and cellulose decomposition stages, and was opposite for the lignin decomposition stage. Physical structure characterization indicated that the pellets had smaller surface area and more compact surface than those of their raw biomasses. Hence, the mass and heat diffusion were suppressed and more cross-linking reactions occurred during pellets pyrolysis.