Radial Distribution of Liquid Velocity in a Liquid-Solids Circulating Fluidized Bed

Abstract

Local liquid velocity was measured in a liquid-solid circulating fluidized bed, with a Plexiglas riser column of 7.62 cm ID and 3.0 m in height, by a dual conductivity probe, with 508 micron glass beads. The results show that radial distribution of local liquid velocity in the LSCFB is nonuniform with higher liquid velocity at the axis and lower near the wall, compared to the more uniform radial profiles in both the conventional fluidization and the dilute liquid transport regimes. The radial nonuniformity increases with increasing liquid velocity and solids circulation rate in the LSCFB. A radial nonuniformity index, proposed by Zhu and Manyele (2001), was used to quantify the extent of the radial nonuniformity under different solids circulation rates and liquid flow rates. The radial nonuniformity index is used to qualify the radial distribution of liquid velocity. RNI values in the liquid-solid circulating fluidization regime are seen to be much higher than those in both the particulate fluidization regime and the dilute liquid transport regime, indicating the nonuniform radial distribution of local liquid velocity in the LSCFB. This illustrates the use of RNI as an effective measurement of the radial distribution of liquid velocity.