| The industrial production of emulsions is still a challenge for chemical engineers. In an industrial context, one has to take into account the high outputs needed for profitability as well as the particular physicochemical properties of the very system in play. We are dealing in this work with the production of low viscosity petrochemical emulsions, the quality of which is imposed for by commercial consideration. The emulsion is to be stable for month, with a controlled granulometry. These properties are first obtained at the lab scale by optimizing the formulation of the emulsion. They are then to be recovered at the industrial scale. One then needs to design a process at the required scale, preferably allowing for a continuous production.;Emulsion production is not a classical mixing and agitation process. Indeed, one needs to disperse a liquid phase in an other liquid and allows stabilizing agents to properly cover the interface. One needs to bring enough energy to mix and transport the liquids, but also create the interfacial area and respect the kinetics of all interfacial mechanisms.;The classical way to design emulsion production processes is to maximize the dispersed energy by using high-speed mixers or high-pressure homogenizers. However, it is difficult to select the right mixing tools based on criteria such as the targeted mean droplet size. Moreover, this method doesn't take any profit from low interfacial tensions that can be obtained due to the presence of interfacial agents in the emulsion.;In this work, we studied at the pilot scale as well as the industrial scale the continuous production of a gasoil-based emulsion. Various mixing tools were studied and can be ranked based on the local dissipation rate of energy. The energy can be evaluated using geometrical parameters (distance between stator teeth, clearance) and mechanical parameters (rotation speed, output). It appears that the energy alone is not the only parameter to consider and that residence time in the high-energy region of the flow is also of primary importance.;Increasing the residence time in this high-energy zone increases the interfacial coverage by interfacial agents. This can induce a stabilisation of the emulsion during its formation. This simple reasoning leads to the conclusion that an increase of the surfactant concentration during the production would be beneficial. (Abstract shortened by UMI.). |
