Development of a particle submodel for CFD-simulations of fixed-bed combustion

Paper in proceeding, 2012

Fixed-bed conversion is one of the standard methods for conversion of biofuels. However, in several cases the performance observed in applications of fixed-bed conversion of biomass and waste is far from optimal. Mathematical modeling using computational fluid dynamics (CFD) has a large potential to assist in the optimization of the fuel conversion processes, with regard to parameters such as burnout, emissions, fuel flexibility and material wear. To this end, computationally efficient models that can handle the most important features of the fuel conversion processes are needed. In the present work, a model is derived for the drying and devolatilization of a moist wood particle in an inert atmosphere. This model is compared to experimental data and discussed in relation to similar models of higher and lower degrees of computational complexity. It is shown that the proposed model is able to predict the correct drying and devolatilization behavior by using only a small number of variables. It is also outlined how this model can be extended to include the char combustion and effects on the multi-particle scale, such as local collapses of the fuel bed.