Microemulsion flash calculations using an HLD-NAC-based equation of state

We describe the state-of-the-art for microemulsion flash calculations using a physics-based HLD-NAC equation-of-state (EoS). The approach assumes phase behavior is well defined by three pseudocomponents, typically labeled surfactant, oil, and water. These pseudocomponents can contain other components such as cosolvents or mixtures of surfactants but only after combining into three pseudocomponents. The water pseudocomponent is defined by salinity, while the oil pseudocomponent by equivalent alkane carbon number. Tie lines and tie triangles are calculated for all Winsor types once the overall composition, temperature, and pressure are specified, analogous to how liquid–vapor equilibrium is determined using cubic EoS. Flash calculations using HLD-NAC, however, require no iteration. Tuning of the EoS to experimental data predicts experimental data well for use in applications from cosmetics to enhanced oil recovery.