Preliminary simulation study of particle coating process by FB-CVD method using a CFD-DEM-PBM model

The present work focused on fundamentally modelling of the fluidized bed chemical vapor deposition (FB-CVD) process, which is the extensively used method to prepare TRISO particles and other types coated particles, aimed at optimizing and scaling up of the coated fuel particles fabrication technology using a mechanistic approach rather than empirical knowledge. Based on the experimental observation of the coating process, the population balance model (PBM) was used to describe the size distribution of nanoparticles in the FB-CVD process. The deposition rate model related to nanoparticle size distribution was developed based on the homogeneous and heterogeneous deposition coexistence mechanism. Furthermore, on a macroscopic scale, the computational fluid dynamics (CFD) and discrete element method (DEM) were coupled with the deposition rate model, establishing a multiscale simulation platform for simulating the FB-CVD particle coating process. In this proposed CFD-DEM-PBM model, the mass, momentum, and energy transfer, along with chemical reaction, nanoparticle formation, deposition along homogeneous and heterogeneous pathways were considered and simulated accordingly. The preliminary study has been conducted successfully and indicates that the proposed multiscale model has clear and important significance for investigating the particle coating process. However, it should be noted that the model parameters still need to be experimentally refined in the future.