Solids circulation in circulating fluidized beds with low riser aspect ratio and varying total solids inventory

Underlying mechanisms for the net circulation of solids in circulating fluidized beds are depicted. The presence/absence of a dense bed yields different solids entrainment patterns, but no difference in solids back-mixing along the freeboard. The solids backflow effect at riser exit is enhanced at higher gas velocities and solids concentrations.161