Particle flow patterns in a fluidized bed

Abstract

Abstract A modified thermistor anemometer probe was used to measure solid particle flow patterns in a 9.5‐in. diameter fluidized bed. The probe was calibrated and found to measure the direction and mass velocity of the silica‐alumina cracking catalyst used. Flow patterns were determined at heights of 6.5, 12.5, 18.5, and 24.5 in. above the support plate with superficial air velocity from 0.25 to 1.00 ft./sec. and bed depths of 14 to 30 in. Radial flow patterns were found not to be symmetrical about the axis of the bed but were similar at angles of 60 deg. This indicated that there were six similar particle flow pattern sections around the column axis. The percentage of the cross‐sectional area of the fluidized bed through which the particle flow is upward was found to be approximately 60%. There was no definite dependence of this area on any of the variables studied. The catalyst bulk circulation rate, defined as the average mass velocity of the particles at a given cross section in a fluidized bed without regard to the direction of flow, was determined for each fluidization condition and correlated as a function of the superficial air velocity and the ratio of the distance above the support plate to the height of the fluidized bed.