Macroscopic Flow Behavior in Risers of Circulating Fluidized Beds

Abstract

A review on the macroscopic flow behavior such as bed-density distribution and change in flow regime, as well as mixing and heat transfer, in risers of circulating fluidized beds is briefly made in the paper. It is usually found that formation of dense bed at the bottom or so-called S-shaped bed-density distribution in riser is usually observed in operation at relatively low gas velocity. Such density distribution, however, is easy to disappear with decreasing and/or increasing of solids circulation rate. Thus, it should be noted that the flow behavior and axial bed-density distribution in riser of circulating fluidized bed have wide variety with changing in gas velocity and solids circulation rate. For future work, it will be needed to take account of solid property for better understanding of solids and gas behavior as well as classification of flow regime.