TRANSITION OF FLOW REGIME IN FLUIDIZED BEDS WITH SLANTING BLADE BAFFLES

Abstract

A flow model is proposed to investigate the transition of flow regime from bubbling to turbulent fluidization postulating that the flow in the emulsion phase follows the Richardson-Zaki equation. Void fraction of the whole bed εf and the mean velocity of bubbles Ub were measured in fluidized beds of 0.3 and 0.5 m ID, in which slanting blade baffles were positioned. Mo-catalyst, silica gel, sand and glass beads with size between 135-443 μm were fluidized by air. Void fraction of the emulsion phase ε e was calculated on the basis of the above model. Correlating ε e with superficial gas velocity Uƒ, we found that ε e was very close to ε mƒ in the bubbling regime and that e, increased with increasing Uƒ in the turbulent regime. Calculated values of the volume fraction of bubble phase δ were correlated with Uƒ, from which apparent transition point from bubbling to turbulent regime was estimated. Combining information obtained, transition of flow regime in the above type of fluidized beds is discussed