The shape development of spherical and non-spherical char particles in the flame zone of an entrained-flow gasifier - A numerical study

The shape of a particle affects its trajectory in an entrained-flow gasifier significantly. For that reason, the present work studies how the particle shape is changed during the conversion process. Several non-spherical particles are considered. The focus is on the conversion process in the flame zone, since that is where the highest gradients in temperature and concentration occur across the particle. A particle-resolved transient CFD model was applied together with a mesh motion algorithm, enabling a detailed analysis of the complex interphase phenomena between the flow field and the reactive particle. It is shown that the particle morphology changes significantly during the conversion process. The final shape depends on the initial particle shape and the reaction rate distribution across the particle, which is a function of the particle Reynolds number. Only in exceptional cases is the remaining particle spherical after leaving the flame zone. This fact must be taken into account if drag coefficients and Nusselt and Sherwood number correlations are applied in a CFD-based reactor model. (C) 2019 Elsevier Ltd. All rights reserved.