Experimental Study of Solids Motion in an 18 m Gas–Solids Circulating Fluidized Bed with High Solids Flux

A comprehensive experimental study of solids motion is conducted in an 18 m-high circulating fluidized bed with an extremely high solids circulation rate (Gs) up to 1000 kg/(m2 s), which has never been achieved in such a tall riser in previous research studies. The axial distributions of the particle velocity show exponential curves and slight changes in the fully developed zone with Gs higher than 400 kg/(m2 s). The radial profiles of the particle velocity have parabolic shapes and become steeper with increasing Gs. The development of the gas–solids flow structure becomes slower with increasing Gs or decreasing superficial gas velocity (Ug). When Gs reaches 800 kg/(m2 s), the full development is achieved until reaching an axial height higher than 12 m. Better correlations between the local particle velocity and solids holdup and less downflowing particles indicate better reactor performance with the reduction of solids back-mixing and uniform residence times at an extremely high Gs.