Numerical Study on the Instantaneous Flow Behaviors of Clusters at the Wall of CFBs

In this study, the gas-solid two-phase flow in a CFB riser was simulated by means of LES-DSMC method. The flow regime of descending clusters at the wall was characterized. The variations of their solid concentration, velocity during descending were studied. Meanwhile, the flow behaviors of particles within them were analyzed too. The results showed that clusters at the wall are dynamic collections of particles and their size, velocity, solid concentrations vary continuously during descending. There exist obvious particle exchange between them and the external dispersed particles. They are accelerated in the axial direction and the radial velocities of them decrease the longer they descend along the wall. The simulated results are in agreement with the relevant experimental data.