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 modes of operation: magnetizing first and magnetizing last. Gas holdups in the riser and the bed as well as local gas holdup were measured to examine the effect of both the gas superficial velocity and the magnetic field intensity on these parameters. It was found that gas, liquid and solid holdups showed a strong dependence on the gas superficial velocity and 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 relating epsilon(gr), epsilon(gb), epsilon and K-L a to U-g and B in the two modes of operations were proposed. (C) 2000 Elsevier Science S.A. AU rights reserved.