Particle dispersion and pressure fluctuations in three-phase fluidized beds

Abstract

Particle dispersion characteristics have been determined by using the stochastic method in a three-phase (gas-liquid-solid) fluidized bed (0.152 m ID x 2.5 m high). To establish the relationship between pressure fluctuations and particle dispersion in three-phase fluidized beds, dynamic pressure fluctuations have been measured and analyzed by the non-linear analysis. The fluctuating frequency, the dispersion coefficient, and velocity of fluidizing solid particles have been determined. The fluctuating frequency and the dispersion coefficient of particles increase with increasing gas velocity and particle size, but exhibit their maximum values with an increase in liquid velocity. The effects of gas velocity, liquid velocity and particle size on the particle dispersion have been determined. The data obtained can be analyzed by the correlation dimension obtained from the chaos analysis of pressure fluctuations in the bed. The correlation dimension increases with increasing gas velocity but decreases with increasing particle size. However, it exhibits a minimum value with variation of liquid velocity. The particle fluctuating frequency, the dispersion coefficient, and the correlation dimension of pressure fluctuations have been correlated with the length and velocity scales of the microeddies in the bed based on the isotropic turbulence theory. (C) 1997 Elsevier Science Ltd.