Both particle–fluid and particle–particle interactions have profound effects on particle segregation and aggregation phenomena. Numerically, these effects are taken into account through an appropriate drag law formulation that should be accurate enough to predict the overall particulate flow behavior. In this work, several drag law models are used to study their effects on particle segregation in a gas–solid fluidized bed. Compared to Syamlal and Bell model, the non-particle–particle drag model yields a significant particle separation in the axial direction, with the tendency of large particles to settle down in the bottom of the bed while small particles gather in the upper part of the bed. The predicted numerical results agree well with Mathiesen's experimental results. The segregation profiles generated by the ad hoc modified drag model and the binarydisperse Van der Hoef drag model are contradictory. Inverse segregation results from the use of the Van der Hoef drag model, which is similar to the Brazil Nut Effect, and the results show significant discrepancies from Mathiesen's experimental results.Highlights► Non-particle–particle model yields a significant axial separation. ► Predicted results of NPP-model agree well with Mathiesen's experimental results. ► Inversion segregation appeared when using the binary-dispersed Van der Hoef model. ► The Van der Hoef model is not suitable for dilute flow systems.

A CFD simulation was performed to evaluate the performance of a novel multiregime gas–solid fluidized riser reactor that was designed to maximize the propylene yield from the catalytic cracking process. Simulation results of the industrial-scale riser reactor show the coexistence of different regimes in the reactor. Also, both the outlet product compositions and the reaction rate vectors indicate that the cracking reactions mainly take place in the feed injection section. The product quality and distribution demonstrate the superiority of this novel process technology. The results of the CFD simulations are in good agreement with the test run results of a real industrial FCC reactor.