AXIAL DISTRIBUTION OF SOLID HOLDUPS IN BINARY SOLIDS CIRCULATING FLUIDIZED-BEDS

The hydrodynamic behavior of binary solids circulating fluidized beds was examined in terms of axial distributions of apparent solid holdup as well as of fine and coarse solid holdups. Experiments were carried out in two circulating fluidized beds of 3 m in height and 97 mm and 1 50 mm in diameter, using FCC catalysts with a mean diameter of 69.7 mu m as the fine particles and 321-mum silica sand and 633-mum activated alumna as coarse particles. The influences of gas velocity solids circ ulation rate, loading ratio of coarse particles and bed diameter on th e axial distributions of apparent holdup and of fine and coarse partic les holdups were investigated. Comparisons were made of the axial dist ributions of solids holdups both in the presence and absence of coarse particles. It was found that the addition of coarse (or dense) partic les results in a significant variation in both the apparent and the fi ne particles holdups. In addition, the nonuniformity of the axial soli d holdup distribution was found to vary with increasing loading ratio of coarse particles.