Thermo-chemical conversion of single wood particle : a numerical study

This paper reports the main findings of the first phase of our ongoing research on numerical study of oxy-fuel combustion of single biomass particle. The primary goal was to develop a detailed one-dimensional model based on mass, energy and momentum conservation principles, and to create a simulation code for investigation of biomass particle combustion at various conditions. Initially, the pyrolysis of a woody biomass particle was studied, since a deeper understanding of biomass pyrolysis was necessary to sufficiently model particle combustion. It was shown that an accurate formulation of energy equation would need to account for variation of enthalpy of reactions with temperature usually neglected in many past studies. In the next step, the endothermic heat of volatiles formation and the exothermic heat of char generation were considered using the correlations proposed in the literature. The improved pyrolysis model enabled us to capture various experimental data including internal temperature peak reported in some past works. A parametric study was subsequently conducted to investigate pyrolysis time and final char density of a single biomass particle with diameter up to 1mm at high heating environments. The pyrolysis model was then extended to account for char gasification and oxidation and gas phase reactions within and in the vicinity of the particle to complete the particle combustion model, which was validated by comparing the predictions with different sets of experimental data reported in the literature. It was found that a correct selection of the pyrolysis kinetic data was a necessary step for accurately prediction of the biomass particle combustion. The reasonable agreement obtained between the predictions and experiments indicate that the particle model and the related simulation code can be used with sufficient accuracy to study combustion of wood particles.