A Eulerian-Eulerian model incorporating the kinetic theory of granular flow is adopted to describe the gas-solid two-phase flows in a multizone circulating propylene polymerization reactor. Corresponding simulations are carried out in a commercial computational fluid dynamics (CFD) code Fluent. First, the model is validated by comparing simulation results with the experimental data. Entire fields in the reactor composed of a riser and a downer are also obtained numerically. Furthermore, the model is used to distinguish the flow behaviors in the riser and the downer. The effects of riser-outlet configuration and operation gas velocity on the flow behaviors in the reactor are also investigated numerically. The simulated results show that the flow behaviors in the riser of MZCR are different from those in the downer of MZCR. In addition, the simulation results also show that both the exit configuration of the riser and the operation gas velocity can significantly affect the flow behaviors in the MZCR. (c) 2011 Elsevier B.V. All rights reserved.