Hydrodynamics of a Three-phase Fluidized Bed

Abstract

The hydrodynamic characteristics viz. the pressure drop, bed expansion and phase hold up of a co-current gas-liquid-solid three-phase fluidized bed has been studied using liquid as the continuous phase and gas as the discontinuous phase. These have been done in order to develop a good understanding of each flow regime in gas-liquid and liquid-solid fluidization. Air, water and glass beads (2.18mm, 3.05mm and 4.05mm) are used as the gas, liquid and solid phases respectively. The experiments were carried out in a 100 mm ID, 2m-height vertical Plexiglas column. The column consists of three sections, viz., the gas-liquid disengagement section, test section and gas-liquid distributor section. Bed pressure measurements have been made to predict the minimum liquid fluidization velocity. By keeping gas velocity at a fixed value, the liquid velocity was varied and the effect on phase hold-up, minimum liquid fluidization velocity, pressure drop and the expansion ratio was studied for different particle size and static bed height. Experimental study based on statistical design has been made to investigate the expansion ratio of fluidized bed and a correlation has been developed for gas hold-up. It is evident from the correlation that gas hold-up is strongly function of modified gas Reynolds number and independent of liquid Reynolds number. The experimental values have been compared with those predicted by the correlations and have been found to agree well.