Determination of Combustion Kinetic Data of Some Agricultural Wastes from the Galicia-Northern Portugal Euroregion

This work concerns the study of the combustion kinetic characteristics of chars made from three different biomass species, vine and kiwi pruning wastes, and gorse from forest cleaning process in a fluidized bed combustor, operating in the bubbling bed regime, at four bed temperatures, 750, 820, 850 and 920 °C. Batches of the original biomass pellets were carbonized in a nitrogen fluidized bed, either at 900 °C, for the kiwi and vine pellets, or at 800 °C for the gorse pellets. To acquire complete information on the combustion behaviour, different sizes of the char particles were subsequently burned in a bubbling fluidized bed. The evolution of the overall combustion resistance, and information on the combustion control were obtained. It was observed that for the kiwi and vine chars, the combustion was controlled through a combination of diffusion and kinetics, while for the gorse char the combustion was diffusionally controlled. In addition, the pre-exponential factors and activation energies were obtained for the kiwi and vine chars, by applying the Arrhenius law to the kinetic data for each char. Activation energy values of 246.16 kJ/mol for the kiwi char and of 155.02 kJ/mol for the vine char were obtained.