THE STRUCTURE CONTROL OF WATER-IN-FUEL EMULSION

Abstract

The emulsification process (receiving a mixture of two immiscible liquids in the form of disperse) is playing important role in different industries (food, pharmaceuticals, cosmetic, and fuel industries). One of the most promising methods used for emulsion preparation is the membrane emulsification. In this case for preparation of the water-in-fuel emulsion (WFE), the dispersed phase (water) under pressure just above capillary pressure is passed through membrane pores forming water droplets at the permeate side of the membrane; these droplets are then carried away from the surface by the continuous liquid phase (fuel). Under specific operating conditions, this method has better ability to form a monodispersed emulsion with lower droplet size consuming less energy compared to other methods (as ultrasonic and high pressure homogenizer).
The emulsion stability is attained by the use of surface-active substances (surfactants or emulsifiers) lowering the interfacial tension between two liquids and so preventing possibility of liquid layers to flow separately with respect to another. The lipophilic surfactants such as non-ionic sorbate esters (known as span’s) are known to be used as agents in preparation of water-in-oil emulsions (including WFE). However, in order to optimize the emulsion stability and degree of dispersion, mixtures of span’s (lipophilic surfactant) and polysorbate (tween’s- hydrophilic surfactants) emulsifiers have been used.
In the current work, at first the analysis and results of the membrane emulsification are introduced with the purpose to define its governing parameters. Secondly, experimental results obtained during the preparation of monodispersed WFE are introduced. The structure of the prepared emulsion is described in terms of the average droplets size and the water droplets size distribution determined by using of the dynamic light scattering and optical microscope. To achieve the emulsion stability, various mixtures from span-60 and tween-60 have been used. Depending on the emulsion dispersity and the mean diameter, a proper faction of mentioned emulsifiers is recommended.