Phase holdup and gas-to-liquid mass transfer coefficient in magneto stabilized G-L-S airlift fermenter

Phase holdups and gas-to-liquid mass transfer coefficient in a three-phase airlift column with magnetic particles were investigated in the presence of an external transverse magnetic field. Experiments were performed in two m odes of operation: magnetizing first and magnetizing last. Gas holdups in the riser and the bed as well as local gas holdup were measu red to examine the effect of both the gas superficial velocity and the magn etic field intensity on these parameters. It was found that gas, liquid and solid holdups showed a strong dependence on the gas superficial velocity a nd the magnetic field intensity. In addition, mass transfer coefficient was determined by the dynamic gassing-in method, and found to increase as gas velocity and magnetic field intensity increase. Correlation equations relat ing epsilon(gr), epsilon(gb), epsilon and K-L a to U-g and B in the two mod es of operations were proposed. (C) 2000 Elsevier Science S.A. AU rights re served.