DIRECT MEASUREMENT OF ASCENDING FLOW OF FINES THROUGH PACKED-BED OF COARSE PARTICLES

Silica-alumina particles of 68-mu-m diameter were continuously fed at the bottom of a bed packed with glass beads of 4.5 mm diameter and were entrained upward through the bed. A small amount of tracer particles was injected into the gas-solid flow, and the ascending velocity of the fines was measured directly using bifurcated optical fiber probes. The dynamic hold-up of fines in the bed was determined from the weight of elutriated particles after the supply of fines was suddenly stopped. Then the gas velocity was much increased, and the entrained particles was assigned as the static hold-up. The ascending velocity of fines was a little dependent on the feed rate of fines, and the value near the column wall was higher than that in the core region. The successive collision model proposed was effective to explain the behavior of fines in the gas-solid flow through the packed bed.