Effects of reducing the reactor diameter on thedense gas–solid fluidization of very heavyparticles: 3D numerical simulations

In this study, 3D numerical simulations using an Eulerian n-fluid approach of a gas–solidfluidized bed composed of very dense particles of tungsten (19,300 kg.m−3) were carriedout to examine the behavior of this suspension, especially the effects of the reduction ofthe fluidization column diameter on the fluidization quality. Tungsten was selected as asurrogate material of U(Mo) (Uranium molybdene) which is of interest for new nuclear fuelswith limited enrichment. Comparisons between experiments and computations for the axialpressure profile of a 5 cm diameter column demonstrate the capability of the mathematicalmodels of the NEPTUNE CFD code to simulate the fluidization of this powder located out-side the classification of Geldart. The numerical results show that the mobility into the bedof these very dense particles is very low. The reduction of the fluidization column diam-eter from 5 cm to 2 cm does not have significant effect on the local solid circulation butstrongly decreases the axial and radial mixing of the particles due to wall-particles frictioneffects. These results confirm and allow to better understand the wall effects experimentally evidenced