Combustion of invasive Acacia dealbata char pellets - determination of diffusive and kinetic data
Carlos Pinho1; Tânia Ferreira1; Carlos Pereira2; João Monney Paiva3
1 Universidade do Porto; 2 Politécnico de Viseu; 3 Politecnico de Viseu
doi:10.20906/CPS/COB-2015-1369
Resumo
The use of biomass and other renewable energy sources becomes ever more essential due to the necessity to minimize the excessive consumption of fossil fuels and lower emissions of greenhouse gases into the atmosphere. A laboratory scale fixed bed reactor heated up by an electrical resistance was used in order to obtain the diffusive and kinetic parameters that control the combustion of char pellets, using a previously developed mathematical model for the batch combustion of solid biomass particles in packed beds. Thereby, these parameters were obtained both from fluidized and from fixed bed combustion of batches of char particles. Acacia dealbata pellets were carbonized in nitrogen at 800 °C for 30 min, being subsequently cut into smaller and more uniform particles with average lengths of 5, 8 and 12 mm. In fluidized bed, batches of 6 g of char pellets were burnt at three different temperatures, 700, 800 and 900 °C, using three different average equivalent diameters, defined by sphericity and Sauter mean diameter. Regarding to fixed bed combustion, the carbonized pellets were burnt in batches of 20 g at 800 °C using the same equivalent diameters. From the combustion of the Acacia char pellets specific diffusive and kinetic data, namely the Sherwood number and the heterogeneous phase carbon to CO oxidation reaction rate constant values, were obtained and the dominant controlling mechanism identified.
Palavras-chave: combustion ; invasive species; pellets ; kinetic data; diffusive data