Modified three-dimensional percolation simulation of char fragmentation and particulate formation

The current numerical calculation of particulate formation during char combustion mainly adopts the two-dimensional model. In this paper, based on the introduction of the concept of diffusion depth, the char combustion is simulated with a three-dimensional model. The modified model can simulate the actual situation that the reactant gas dose not diffuse into the char completely. The approach to realize the combustion process of char in chemical controlled zone (zone I) and transitional controlled zone (zone II) is given, and the results are compared with those in the diffusion controlled zone (zone III). The characteristic impact of initial porosity and mineral content on particulate formation in different zones is analyzed through the simulation and comparison. It can be seen from the results that the diffusion depth do put some limits on char fragmentation and mass distribution of ash particulates, which provides theoretical basis for the further study of particulate formation during char combustion and the reduction of particulate emission.