Recirculating turbulent flow of liquid in gas-liquid-solid fluidized bed.

Abstract

Axial and radial distributions of gas holdup and liquid velocity were studied in a gas-liquid-solid fluidized bed of 0.12 m i.d. Air, water and glass beads (0.58, 1.2 and 2.2 mm in diameter) were used as gas, liquid and solid particle phases, respectively. Local gas holdup was meaured by using an electric conductivity probe, and local liquid velocity was obtained by the electrolyte tracer method. The value of local gas holdup was in proportion to the square of the distance from the column wall. The liquid flow pattern was similar to that of the bubble column, showing an up-flow in the central region and a down-flow in the peripheral region with respect to the interstitial mean liquid flow. Liquid velocity at the central axis increased with increasing superficial gas velocity and with decreasing particle diameter. The results were analyzed on the basis of the circulating flow model, where a constant turbulent viscosity and a constant composition of the liquid-solid mixtures were assumed. The turbulent viscosity for fully developed fluidization was correlated as a function of particle diameter and superficial gas velocity, and was compared to that of the bubble column.