Hydrodynamics characteristics of three phase fluidized beds

Abstract

Hydrodynamic properties (phase holdups, bed porosity, bubble length, bubble rising velocity, bubble frequency, bubble chord length distribution, and radial dispersion of liquid phase) in gas-liquid systems, in liquid solid and in three phase fluidized beds have been determined in two large (0.152 m-ID × 1.8 m-high and 0.376 m-ID × 2.1 m-high) Plexiglas columns. The effects of superficial gas (0.0~0.16 m/s) and liquid (0.0 ~ 0.14 m/s) phase velocities, particle size (0.0 ~ 8.0 mm), liquid viscosity (1.0 ~ 60.0 mPa.s), and column diameter (0.152, 0.376 m-ID) on the individual phase holdups, bed porosity, bubble length, bubble rising velocity, bubble frequency, bubble chord length distribution, and radial dispersion of liquid phase have been determined. A new flow regime map based on the drift flux theory with the bubble behavior in three phase fluidized beds has been proposed. In the gas-liquid systems, gas holdup, mean bubble length and bubble rising velocity and radial dispersion coefficient increase with increasing gas velocity. The gas holdup and mean bubble length decrease, but the radial dispersion coefficient increases with increasing liquid velocity. The gas holdup, bubble rising velocity and radial dispersion coefficient slightly decrease, but bubble length increases with increasing liquid viscosity. The mean bubble velocity and bubble frequency decrease, however mean bubble length varies insignificantly with an increase in radial distance from the center of the column. The radial dispersion coefficient linearly increases, but bubble length and velocity decrease with increasing column diameter. The bubble length and bubble Reynolds number have been correlated with the experimental variables as follows: $l_{vm}=1.64 \times 10^{-2} U_g^{0.44} U_l^{-0.13} μ_l^{0.11} D_c^{-0.33}$ $Re_b=125.31 Fr_{gc}^{0.33} Fr_{lc}^{-0.05} Mo^{-0.22}$ In addition, the radial dispersion coefficients in terms of the bubble Peclet number have been well represen...