Enhancement of Gas Holdup and Oxygen Transfer in Three-Phase Circulating Fluidized-Bed Bioreactors with Swirling Flow

Abstract

Enhancement of gas holdup and oxygen transfer was investigated in the riser of a three-phase circulating fluidized bed, with a diameter of 0.102 m (ID) and a height of 3.5 m, by means of liquid swirling flow. Effects of gas (0.01-0.07 m/s) and liquid (0.17-0.44 m/s) velocities, fluidized solid particle size (1.0, 1.7, 2.1, 3.0 mm), solid circulation rate (2-8 kg/(m(2)s)) and swirling liquid ratio (0-0.5) on the gas holdup and volumetric oxygen transfer coefficient in the riser were examined. The gas holdup and oxygen transfer coefficient could be increased up to 25-30% and 20-25% respectively, by means of liquid swirling flow in the riser. The values of gas holdup and volumetric oxygen transfer coefficients were well correlated in terms of dimensionless groups as well as operation variables within these experimental conditions.