THE ROLE OF GAS DISENGAGEMENT AND SURFACE-ACTIVE AGENTS ON HYDRODYNAMIC AND MASS-TRANSFER CHARACTERISTICS OF AIRLIFT REACTORS

The hydrodynamics and mass transfer characteristics of a 0.7 m(3) exte rnal loop airlift reactor were experimentally investigated for superfi cial gas velocities between 0.02 and 0.18 m s(-1). The reactor was mad e of QVF glass sections with 6.5 m in height and 0.225 m in diameter o f both riser and downcomer. The effects of the addition of minute quan tities of silicone polymer, polypropylene glycol and octanol, on air-w ater systems were examined. In general, the addition of surface active agents led to significant reductions in volumetric mass transfer coef ficients and liquid circulation velocities, relative to the values det ermined for the air-water system. However, for the gas hold-up, gas di sengagement section was found to have a great effect on the reactor pe rformance, especially when foaming increased in the system. Of the two gas disengagement sections used (namely, closed and open channel) the closed channel configuration failed to remove the increasing small bu bbles and the reactor continuity disrupted at high gas throughputs. In contrast, the open channel configuration improved the reactor perform ance with substantial reduction in downcomer gas hold-up and increase in volumetric mass transfer coefficient. (C) 1997 Published by Elsevie r Science S.A.