Stability of model emulsions and determination of droplet size distributions in a gravity separator with different inlet characteristics

A model system consisting of an aliphatic oil (Exxsol D60), a commercial surfactant (nonyl-phenol-ethoxylate, Berol 26) and water was examined in a gravity separator loop system. By using a surfactant, we tried to control the stability of the dispersion and to extract the influence of some of the separator characteristics. The parameters varied were water cut, pressure drop, volumetric flow rate and inlet device. Initial droplet size distributions (DSDs) were obtained and examined for both water- and oil-continuous systems. It was observed that under these experimental conditions and for these surfactant concentrations (≤330 ppm) the oil-continuous dispersion was very unstable and consequently the DSD measurements were not representative for the whole population of droplets. For the water-continuous emulsions, variations were found to be dependent on pressure drop, water cut and flow rate. In this case all the DSD data seemed reliable and accurate.