Measurement of local fines movement in a fluidized bed of coarse particles by a fluorescent tracer technique

Abstract

The movement of fines in a fluidized bed of coarse particles is an important factor for an understanding of multi-size particle systems. In this work, porous catalyst particles of 60 – 65 μm in size were coated with a fluorescent dye and were used as the tracer. The fluorescence emitted from the tracer particles was detected with a set of bifurcated optical fiber probes. The fluidized bed consisted of a transparent 19-cm i.d. pipe with silica gel spheres of diameter 1.54 mm. The percolation velocity of fines in a quiescent bed was well expressed by the model assuming the successive collision of fines on coarse particles. With the presence of gas bubbles, however, the fines percolation increased with increasing gas velocity and height from the gas distributor. The uptake and shedding of fines by bubble wake was found to play an important role in this case. The lateral spread and the downward movement of fines was not dominant unless large bubbles were generated.