Abstract
Accurate and reliable phase equilibrium calculations of microemulsion systems are of great importance. This study deals with the thermodynamic modeling of Liquid–Liquid Equilibrium (LLE) of a system including oil (n-decane), brine (containing CaCl2 salt), and ionic surfactant (sodium dodecyl sulfonate). Two models of UNIQUAC and UNIQUAC + Debye–Hückel were used for thermodynamic calculations. The LLE experimental data were utilized to estimate the binary interaction parameters of UNIQUAC model and the adjustable parameter, b, of the Debye–Hückel model. The thermodynamic model calculates the microemulsion phase’s compositions by minimizing the Gibbs free energy of the LLE system using a combination of genetic algorithm and fmincon function in order to prevent local minima. The thermodynamic modeling results show an appropriate agreement with the experimental data. Accordingly, the presented model of this study can be used as a suitable method to investigate the liquid–liquid equilibrium of systems containing oil, water, and surfactant.
Highlights
Petroleum products, colloidal systems, and those which result from biomass conversion are among the fluids that have received much attention in various industries [1, 2]
Because of the high demand for oil around the world, more attention is being paid to Enhanced Oil Recovery (EOR) methods [3]
As Teh and Rangaiah mentioned in their study, in order to have precise phase equilibrium calculations, an accurate global minimum is required [19]
Summary
Petroleum products (oil, gas, and fuels), colloidal systems, and those which result from biomass conversion are among the fluids that have received much attention in various industries [1, 2]. In 2016, Li et al unlike the use of minimizing the Gibbs free energy (coupled with stability test), solved isoactivity equations for their LLE calculations using NRTL model, and conducted their study on two-phase LLE systems. They concluded that this approach could be applied to multiphase systems [26]. Riazi and Moshfeghian presented a thermodynamic approach using NRTL activity coefficient model They used Debye–Hückel theory to calculate the long-range interactions. The LLE of oil, brine, and surfactant systems was studied through Gibbs free energy minimization method on the data provided in Riazi and Moshfeghian’s research [37]. Two models of UNIQUAC and UNIQUAC + Debye–Hückel were used, and the results were compared with the previous research
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