The hydrodynamics of a pilot plant multistage mixer column extractor was studied for the tohenelwater 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 conditions, 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.

An ultrasonic technique is developed to determine the dispersed-phase holdup of liquid-liquid dispersions by measuring the velocity of ultrasound in suspensions and emulsions. A time-average model is proposed which permits estimation of the dispersed-phase holdup from the overall transmission time of the sound pulses. A statistical analysis on the experimental data revealed that there is no significant difference between typical data and calculated holdup values [0.00 < < 0.40] for dispersions of xylene droplets in water. Important features of this technique are (a) the ultrasonic transducers may be located on the outside of the vessel wall and (b) the transient behavior of the dispersion as well as the axial holdup profile can be accurately monitored.

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