![]() Walstra (1993), where droplet break-up in laminar and turbulent flow is discussed and quantitative relations are presented. A detailed review of the principles of emulsion formation has been published recently by P. However, the surfactant film formed at the interface of the droplet also tends to resist coalescence. Impurities or surfactants present in the system adsorb at the interfaces of the droplets, lower the interfacial tension, and thereby facilitate coalescence. These droplets are subsequently broken up into smaller droplets by the continuing agitation. Initially, the interface between the two phases is deformed and large droplets are formed. There are many ways of producing an emulsion and it is usually achieved by applying mechanical energy through agitation, normally by using an homogenizer. The material of the shearing plates for the homogenizer used in the emulsification process also influences the type of emulsion formed, e.g., oil-wetted plates strongly favor W/O emulsions. It may occur in the oil reservoir itself or while flowing through pipelines, mechanical devices, such as pumps, and gas separators.Ĭontrolling factors in the formation of an emulsion are: mechanical energy, agitation time, temperature, volumetric ratio between the two phases, degree of dispersion of the internal phase and presence of impurities or surfactants. An example is the case of the oil industry where emulsification of oil and brine is common. Other times, the formation of an emulsion is totally undesirable. This is the case, for example, in the production of mayonnaise, where ground mustard seeds are normally added to act as an emulsifying agent. Sometimes, the formation of an emulsion is the deliberate outcome of a manufacturing process. To form a stable emulsion, an emulsifying agent must be added to the system. When the agitation stops, if the drops coalesce and the two phases separate under gravity, the emulsion has been temporary. Drop sizes normally vary from 1 μm to 50 μm. Emulsions can either be oil-in-water (O/W) or water-in-oil (W/O), depending on whether the continuous phase is the water or the oil, respectively. An emulsion is formed when two nonsoluble liquids (e.g., an oil and water) are agitated together to disperse one liquid into the other, in the form of drops.
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