Cluster behavior in CFB riser and downer simulated by CFD-DPM method

This paper presents a numerical study of the particle cluster behavior in a circulating fluidized bed (CFB) riser/downer reactor by means of the CFD-DPM method. It is shown that the existence of particle clusters, unique to the solid flow behavior in the CFB, can be predicted from this first principle approach. The results demonstrate that there are two types of clusters in the riser and downer: one is in the near wall region where the velocities of particles are very low; the other is in the center region where the velocities of particles are very high. The extent of particle aggregation for the second type of cluster in the downer is less than that in the riser and the duration time for the first type of cluster is shorter in the downer, which are qualitatively similar to the experimental observation.