PERCOLATING VELOCITY OF FINE PARTICLES THROUGH PACKED-BED OF COARSE PARTICLES

The percolating velocity of fines through the packed bed of glass beads of 4.5 and 12 mm in diameter and silica gel spheres of 1.5 mm in diameter was measured with bifurcated optical fiber probes. Silica-alumina particles of 68-mu-m, alumina particles of 211-mu-m and glass beads of 398-mu-m were coated with a fluorescent dye, and were used as a tracer. When 1 approximately 2 cm3 of the tracer particles was injected in the gas flow and exposed to ultraviolet light which was introduced with the silica fiber, visible light was emitted and transferred outward with the plastic fiber. The percolating velocity of fines was determined from the time period to pass the distance between the probes. The ascending velocity of fines increased with increasing gas velocity and size of packed particles. A flow model of fines was proposed on the basis of the successive collision of fines on coarse particles. The percolating velocity of fines agreed with the calculated value. The measuring system developed was proved to be able to detect the local percolating velocity of fines in packed bed. The ascending velocity near the column wall was higher than that in the core region.