The axial distribution of the cross-sectionally averaged voidage in fast fluidized beds

Based on experimental results from two fast fluidization columns (D = 0.186 m × 8 m and D = 0.140 m × 10 m) and the results reported in the literature, the effects of gas velocity, solids circulation rate, particle diameter and density, bed diameter and solids inlet and exit restriction on the axial voidage distribution in fast fluidized beds are studied. The axial voidage distribution is found to have a basic profile described by a simple exponential function, with increasing voidage from the bottom to the top of the bed. With special bed structures, the basic axial voidage distribution profile may change into a C-shape with strong exit restriction or into a S-shape with weak solids inlet restriction.