Experimental Hydrodynamic Study of a Three-phase Semi-Fluidized Bed

Abstract

A semi-fluidized bed is characterized by a fluidized bed (acts as CSTR) and a packed bed (acts as a tubular flow reactor) in series within a single contacting vessel. The possible alteration of the internal structure allows the device to be utilized for a wide range of physical, chemical and biochemical applications. Little information is available on semi-fluidization in the gas-liquid-solid three phase systems, which can best be used as immobilized cell bioreactor. In the present study hydrodynamic characteristics viz. the pressure drop, minimum and maximum semi-fluidization velocity, and rate of top packed bed formation of a co-current gas-liquid-solid three-phase semi-fluidized bed has been studied using liquid as the continuous phase and gas as the discontinuous phase Experiments has been conducted in a 100 mm ID, 2m-height vertical Plexiglas column using air, water and glass beads in order to develop a good understanding of each flow regime in gas-liquid-solid semi-fluidization. It is found that pressure drop increases with increase in particle size and static bed height. The minimum liquid semi-fluidization velocity (Ulmsf) increases with particle size but is a weak function of static bed height. Ulmsf decreases with gas velocity. The height of top packed bed increases with liquid and gas velocities, but decreases with particle size and static bed height.