Abstract
For an unbaffled aerated agitated vessel treating electrolyte solutions, power consumption of an unsteadily co-reverse rotating impeller and mass transfer were studied experimentally. Measurements were made for the torque of the drive shaft on which the cross type of impellers with four delta blades were attached multiply, and the data obtained were analyzed by fitting them to an equation consisting of two terms with respect to the resistance of fluid, one due to viscous drag and the other due to inertial drag. The effects of gas sparging rate, agitation rate and the number of impellers on the viscous and inertial drag coefficients were evaluated. Empirical relationships which predict the values of these coefficients, necessary to express the unsteady behavior and magnitude of agitation torque, were presented. A equation giving the relation between the power consumption of the co-reverse rotating impeller and the two drag coefficients was developed. It was demonstrated that the values of average power could be well predicted by using the viscous drag coefficient. The volumetric mass transfer coefficient based on absorption of oxygen in air by electrolyte solutions was examined with varying the aeration and agitation conditions, and its dependence was evaluated in relation to the average power consumption of the impellers, i.e., agitation power input. Based on a comparison of the volumetric coefficient as viewed from changes in the specific total power input due to agitation and aeration between this type of vessel and conventional baffled vessel with steadily unidirectionally rotating impellers, a feature of the former vessel as gas-liquid contactor was discussed.
