The rate of gas induction was measured in 0.57,1.0, and 1.5 m i.d. gas inducing types of mechanically agitated contactors (GIMAC). The ratio of impeller diameter to vessel diameter was varied in the range 0.13 < D/T < 0.59. The effect of impeller submergence from the top and impeller clearance from the bottom was investigated in detail. The effect of impeller speed was studied in the range 0.13 < N < 13.5 r/s. A model has been developed for the critical speed for gas induction, and for the rate of gas induction with the description of forced vortex structure in the impeller region. A unified theme has been proposed for the understanding of phenomena such as the critical speed for gas induction and the rate of gas induction. The physical significance of model parameters has been interpreted on the basis of flow information in the impeller region.

Rates of gas induction and fractional gas hold‐up were measured in a 0.57 m i.d. gas inducing type mechanically agitated contactor. Several designs of the impeller were employed for optimizing the rate of gas induction with respect to power consumption. The effect of blade width blade, angle, blade thickness, blade curvature, number of blades, etc. on gas induction, has been investigated in detail. An optimum design has been proposed. Hysteresis in the gas induction rate and power consumption was observed for a wider impeller projecting out of stator.

No abstract

The gas induction characteristics of a stator-rotor-type self-inducing impeller were investigated in the cases without and with gas line resistance. To understand the hydrodynamics near the impeller, and to characterize the mechanism of gas induction, the local liquid velocity was measured with a laser Doppler anemometer. The effect of impeller speed, impeller submergence, and gas line resistance on the volumetric flow rate of liquid, as well as the rate of gas induction, was investigated. The dominant role of local gas holdup was identified and the mechanism of gas induction was established, with the help of an energy balance.