École Nationale Supérieure de
Techniques Avancées

Abstract

The presence of electrolytes changes considerably the mutual solubilities of water-hydrocarbons mixtures and the representation of thermodynamic properties becomes more difficult. Often, heterogeneous models are used for these type pf problerns. Yet, this study proposes an equation of state based on methods derived from statistical thermodynamic approaches. In this work, we focus on the extension to electrolyte systems of the CP A equation of state. To account for electrolyte interactions an MSA (Mean Spherical Approximation), SR2 and Born terms contributions are used. In this thesis, we first validate the model (CAP-E) to represent the properties of electrolyte solutions (NaCI, CaCh), using density, osmotic coefficient and activity coefficient experimental data, and its temperature extension. The model was also extended to other salts. Then, the results of the model extension to ternary mixtures are presented (water-hydrocarbon-salt, waterhydrocarbon-methanol, water-methanol-salt), the aim being to allow the representation of the properties of the complete system: water-hydrocarbon-methanol-salts.