Emulsion processing using the combined electrical and shear forces

The use of electric fields to aid droplet break-up in emulsion manufacture was investigated with the aim designing more advanced processes for reducing droplet size in liquid-liquid systems. Processing conditions, equipment design and fluid properties on droplet break-up and emulsification performance were investigated, with particular emphasis on the effect of the electric field. Computational modelling established the electrical stresses in a point-and-plane electrospraying configuration, followed by the construction and investigation of custom apparatus. A minimum droplet size when spraying distilled water into air of 370 μm was achieved, which was attributed to a geometric limitation of the system, but the reduction of droplet size correlated with increased electrical stress. Further apparatus based on a Silverson L4RT high-shear mixer was developed to investigate the application of an electrical stress in addition to shear stress. There was not a direct correlation between electric stress and changing droplet size. Instead, the mean droplet sizes were seen to increase when electrical stress was applied, however the droplet size distributions showed that the increase in mean droplet size was an artefact of coalescence, with much smaller droplets being formed as a result at the smaller end of the distribution