The fluid mechanic basis for the design criteria of gravity liquid-liquid settlers

The fluid mechanic phenomena governing the operation of a horizontal gravity liquid-liquid settler were experimentally investigated. The hexane-water fluid system was used throughout most of the investigation, with the kerosene-water fluid system being used to verify the generality of the results. Many variables were investigated and the settler system was operated over an extremely wide range of conditions. Velocity patterns were measured using a laser Doppler velocimeter and motion picture techniques. The most significant finding was the ability of the dispersion zone between the two fluids to absorb momentum from the surrounding bulk phases. The dispersion zone flows as a plug, but at a markedly different velocity than the surrounding bulk phases. In addition it was found that the rate of coalescence was determined not only by the fluid properties as in a static environment, but also by the hydrodynamic forces between the drops which in turn affect the rate of bubble film drainage and film rupture.