CFD-DEM study of spout deflection behavior of cohesive particles in a spout fluidized bed

Abstract

The spout deflection problem limits the operating range and poses a threat to the normal production of fluidized beds especially when the cohesive particles are practised, yet these processes were not well understood at the particle scale in the past. In this work, the spout deflection behavior of cohesive particles in a pseudo-2D spout fluidized bed is studied by Computational Fluid Dynamics - Discrete Element Method featuring a cohesion sub-model. The model is validated against experimental measurements of two cases. Then three types of particles are studied including dry particles and two types of cohesive particles covered by water and honey, respectively, for comparison in terms of flow pattern, spout deflection, and bed pressure drop. The simulation results show that compared with the case of dry particles, the cases of cohesive particles have smaller spout deflection, 16.3% smaller for water-covered particles and 68.1% smaller for honey-covered particles in their base cases. Further, the effects of key parameters are studied. The median value of the spout deflection angle for dry and cohesive particles all increases with increasing spouting gas velocity. The median values of the spout deflection angle of cohesive particles are significantly affected by initial particle surface liquid content. At last, the gas pressure drops in the vertical direction caused by the particle resistance are almost the same between the cases of dry and cohesive particles; however, the gas diffusion in the horizontal direction is highly correlated with the initial particle surface liquid content, liquid types, and spouting gas velocity. This work unveils the impacts of cohesive particles on spout deflection and sheds light on the optimal operation for practical applications.