A three-dimensional Eulerian-Lagrangian model

based on MP-PIC method

was developed to simulate particle clusters in fast fluidized bed risers. In the model

gas phase was simulated by large eddy simulation (LES)

real particles were displaced by numerical-particles and particles was described by Newton movement equations

drag between gas and particles was calculated by Gidaspow model

and normal stress of particles was calculated and interpolated into Eulerian grids to describe particle contraction. The model was used to simulate gas solid movement in a 3D fast fluidized bed riser with dimension of height H=3 m and diameter d=0.1 m and adjusted according to experimental data. Cluster characteristics of particles (ρp=2650 kg·m-3 and dp=250 mm) was studied at operational condition of Ug=5.28 m·s-1gas velocity. The results indicate that the MP-PIC simulation can recognize different shapes of clusters

such as stripe-shaped

saddle-shaped and U-shaped

as well as disclose cluster development including formation

expansion

coalescence and breakup. Mean particle concentration distribution of clusters in the riser cross section shows a core-annular structure with low middle and high edge concentrations

which is opposite to mean cluster velocity distribution. The mean particle concentration of clusters decrease while the mean cluster velocity increase with increase of riser height

but the change of both concentration and velocity slows down above certain riser height.