Mixing and Segregation Behavior in a Spout-Fluid Bed: Effect of Particle Size

The mixing and segregation behavior of a binary mixture have been investigated experimentally in a spout-fluid bed. Three types of binary mixtures were used by mixing glass beads with equal density and dissimilar size. The spouting and fluidizing gas flow rate were adjusted to cover a range of flow regimes, typically including internal jet (IJ), jet in fluidized bed with bubbling (JFB), spouting (S) and spout fluid (SF). The mixing and segregation behavior were analyzed in terms of flow regimes, concentration profile, and mixing index. The results show that in IJ, the particle circulation is combined with the local segregation where smaller particles migrate to the interface between the jet and Stagnant region, even into the latter. In S, the distribution of particle depends greatly on the fountain structure. In JFB, the axial segregation takes place where the smaller particles prevail in the upper part of the bed. Segregation becomes more pronounced with increasing the particle size difference. In addition, a mixing/segregation pattern map is constructed. Three regions including mixing region, segregation region, and intermediate region, are identified by the criterion of mixing index.