Calculation of the Saturation Properties of a Model Octane-Water System Using Monte Carlo Simulation

We use Monte Carlo simulation to compute the saturation properties of a model octane-water system. The system phase separates into water-rich liquid and vapor phases, octane-rich liquid and vapor phases, and water-rich liquid and octane-rich liquid phases at various conditions. We outline a strategy for determining the saturation properties of the mixture over a wide range of temperatures, pressures, and compositions. The approach begins with direct calculations that enable one to locate a single saturation point. A variety of expanded ensemble schemes are then used to trace saturation curves along paths of interest. We show how the overall strategy provides a means to construct pressure-composition diagrams at a fixed temperature and temperature-composition diagrams at a fixed pressure. In addition, we demonstrate how the approach is used to trace the liquid-liquid-vapor triple line over a wide range of temperatures. Simulation data are compared with experimental data, when available. Overall, our results show that the approach provides an efficient means to calculate the saturation properties of a binary system.