Mass transfer in a rectangular air-lift reactor: effects of geometry and gas recirculation

The interrelationships between the three parts of the air lift reactor, the riser, the downcomer, and gas-liquid separator, were examined with relation to the overall mass transfer in the reactor. This involved studying the mass transfer of oxygen from the gas phase to the liquid phase for 20 different reactor geometries. Both one- and two-sparger systems were studied. It was demonstrated that the gas-liquid separator plays a major role in reactor behavior and must be considered in reactor design. It was found that the overall reactor mass transfer coefficient KLA could be correlated to the pneumatic power of gas input per total dispersion volume (P/VD) and to the true riser superficial gas velocity JGR for all experimental conditions examined. The KLA is directly related to the P/VD with an exponent of approximately 1. "Two-sparger" systems, where an auxiliary gas sparger is placed near the downcomer entrance, have higher ab solute values for KLA than single-sparger systems.