Solids behavior in freeboard of FCC regenerator

The effect of gas velocity (0.56-1.15 m/s) on radial voidage distribution a nd cluster properties is determined by using an optical fiber probe in the freeboard of a FCC regenerator (0.48 m-I.D. x 3.4 m-high). The normalized s tandard deviation of pressure fluctuation in the freeboard region decreases with increasing gas velocity. Local voidage distribution in the radial dir ection is relatively flat in the bubbling flow regime. However, in the turb ulent flow regime, voidage in the cure region is higher than that in the wa ll region. Clusters move up and down simultaneously, and cluster velocity i n the core region is higher than that in the wall region. Cluster length de creases with increasing gas velocity. As the gas velocity is increased, clu ster frequency, fraction and voidage decrease in the transition from bubbli ng to turbulent fluidization regime, but increase in the turbulent flow reg ime, Variation of the normalized standard deviation of pressure fluctuation in the freeboard can he related with the cluster properties. Cluster lengt h decreases with increasing the suspension density. The cross-sectional mea n cluster length in the freeboard zone is correlated with the suspension de nsity as well as the experimental variables.