FCC particles, known as Geldart’s group A particles, are slightly cohesive and have a wide range of particle size averaging 70 mu m. FCC particles have a tendency to form clusters or agglomerates in a gas/particles flow system. In order to understand the effect of cluster formations or agglomerations on the FCC particles now behavior, a numerical simulation using our modified kinetic theory model for gas/FCC particles flow in a circulating fluidized bed was performed. The simulation results compared reasonably well with the experimental data of Miller and Gidaspow (1992).