Lagrangian approach for simulating the gas-particle flow structure in a circulating fluidized bed riser

Lagrangian approach is used to simulate the realistic process of cluster formation in circulating fluidized bed riser. The influence of particle properties, porosity function and gas velocity on the global particle flow structure, and the formation and development of local regions of higher particle concentration are investigated. The collision parameters govern the formation of non-homogeneous flow structure because of the difference of kinetic energy and velocity distribution. Moreover, the porosity function has a significant effect on the clusters. The gas flows preferentially into the region of high porosity, which leads to non-uniform drag force on the particles and affects strongly the particle flow structure. Examination of the cluster microstructure shows that the particle velocity in the cluster is smaller than around it. Segregation of particles with different diameter and density is also predicted.