Copyright: © WSA Picture top: Phase function and scattering coefficients, artistic representation; Picture below: SEM-photograph of coal particles

In the subproject "Modelling the radiative properties of pulverised biomass particles during oxyfuel combustion" of the Collaborative Research Center OXYFLAME, the interaction between particles and thermal radiation during the combustion of pulverised biomass in an oxyfuel atmosphere is investigated and modelled. For the radiative heat transfer during combustion as well as for the thermal balance of the particles, the scattering behavior of the particles plays an important role for a reliable simulation of the combustion – besides their absorption and emission behaviour. In this context, ash as well as soot particles are considered in addition to solid fuel particles.

As a final goal, the developed models should be used in the overall CFD simulation of oxyfuel combustion, whereby this goal directly poses a limit to the permissible complexity of the models. As a basis for the modelling, Mie-Lorentz scattering is applied, which gives an analytical solution of the scattering of electromagnetic waves by spherical particles. Based on this theory, an efficient model is developed to account for the non-spherical shape of the biomass particles. This theoretical description of the scattering behaviour is combined with measurements of the emissivity and absorptivity of the particles to provide an accurate and efficient model for calculating the scattering and absorption characteristics of particles in the numerical simulation of biomass combustion.