(201c) Effect of Particles Clusters on Reaction Behavior in FCC Risers

Fluidized catalytic cracking (FCC) is a critical approach to convert heavy oil into light products, and the riser reactor is the key part of FCC unit. The particle clustering is the typical flow characterization in the riser reactor, which leads to the heterogeneous spatial-temporal distribution of all the parameters of oil gas and catalyst particles. The numerical simulations were applied to predict the flow, heat/mass transfer, and reaction behavior in the riser reactor. However, most of these simulations were based on the conventional two-fluid model which was mainly resolved by the average method, and did not consider the particle clustering and its effects, thereby leading to the deviation of predicted results with actual data. Therefore, the present work focused on the investigation on the effect of particle clustering on the chemical reactions behavior in FCC riser reactors, and then develop a combined flow-transfer-reaction model involving the meso-scale structure, to accurately predict the reactions behavior in the riser. The results showed that the reaction rates on different particles of the clusters were of great difference. The voidage,shape and size of particle clusters as well as the slip velocity between the gas and particle phase influenced the reaction rates and the species concentrations. According to these results, a correction factor was proposed to consider quantitatively the effect of particle clustering on cracking reactions in FCC riser.