Trajectories of charged drops in a liquid-liquid system

The enhancement of liquid droplet dispersion and motion in liquid-liquid contactors by the introduction of electrostatic charge and an electric field is a potentially important method of process intensification for solvent extraction and other liquid-liquid operations. An understanding of those factors which influence drop motion in these systems is essential for the prediction of hydraulic and mass transfer data which in turn are necessary for the design of commercial scale equipment. The work described here aims to develop an accurate method of measuring and predicting single drop trajectories in electrically charged liquid-liquid systems. Two experimental methods are described, including a simple video recording system in which the trajectories of drops were manually digitised and a more elegant procedure in which space-time images of moving droplets were analysed using image analysis software. Three liquid-liquid systems were studied: pre-saturated sunflower oil/water, pre-saturated 1-decanol/water and pre-saturated silicone oil/water. The trajectories were determined at a range of applied electrical field strengths and over a range of drop sizes and in two scales of experimental geometry. The results were compared in each case with the trajectories predicted using a quantitative finite-element model and good agreement was obtained. (C) 2003 Published by Elsevier Science B.V.