Determination and comparison of combustion kinetics parameters of agricultural biomass from olive trees

Thermogravimetric curves in air, measured for the different types of agricultural residues from olive trees (leaves, pruning and wood) at different heating rates (5, 10, 20, 40, 100 K/min), are subjected to kinetic evaluation by model-based and model-free methods. It is shown that the combustion process in the samples analyzed can be divided into three stages: water removal, roasting phase and char decomposition. At every stage, the activated energy varies with the mass conversion for the kinetic models considered. Its value was determined by the model-free methods, of which Flynn-Wall- Ozawa and Kissinger-Akahira-Sunose were the most appropriate for this purpose and resulted in similar values of activated energy. Once the activation energy was determined, the order of the reactions and the frequency factors of each stage were calculated by means of the Coats-Redfern model-based method in order to complete the determination of the kinetic triplet. From the results obtained, it was deduced that the most feasible reaction order was one.