Optimization of the UO2 kernel coating process by 2D simulation of spouted bed dynamics in the coater

In the present study, a 2D Euler–Euler numerical simulation was carried out to study the hydrodynamics in the spouted bed with different gas velocities and gas inlets (single-nozzle and multi-nozzle). The maximum spouted height could be mainly determined by the gas velocity if the packing heights of particles were the same. The spatial distribution of particles was uneven and the aggregation of them near the wall could be found when using the single-nozzle gas inlet, regardless of the gas velocity. The aggregation of particles could be partly reduced by using the multi-nozzle gas inlet instead. The dead zone could be eliminated under appropriate particle loading by using the spouted bed bottom with the multi-nozzle gas inlet. Based on the simulation results, the appropriate gas distributor design was recommended to increase the gas solid contact efficiency. It can also be revealed that the temperature would affect the physical properties of gas and particles, thus affecting the particle fluidized state from the simulation results. The maximum spouted height increased with increasing temperature, but the quantitative comparison between the simulation results and the experimental ones can not be obtained because of the limitation of the measuring techniques at high temperature. The present investigation showed that the gas distributor had a critical impact on the gas-particle contact efficiency in the gas–solid two-phase system in the spouted bed, and CFD is a good alternative tool to optimize the spouted bed design in researching the coating process of the UO2 kernel.