Flooding, holdup, and drop size measurements in a multistage column extractor

The hydrodynamics of a pilot plant multistage mixer column extractor was studied for the toluene/water physically equilibrated system. The effects of rotational speed, and continuous and dispersed phase flow rates were investigated under a variety of operating conditions. Dispersed phase axial holdup profiles, determined by a noninvasive ultrasonic method, showed a strong nonuniformity. Depending on the operating conditons, holdup profiles can change from a concave shape to a sigmoidal form with a maximum in the bottom of the column. Sauter mean diameter and drop size distribution profiles are strongly affected by rotational speed. Significant, but weaker, are the effects of continuous and dispersed phase flow rates. Continuous monitoring of the holdup profile in the proximity of flooding leads to the formulation of proper criteria for the prediction of flooding. These criteria are appropriate for models allowing for axial variation of the holdup along the contactor.