Development of a thermodynamically consistent, robust and efficient phase equilibrium solver and its validations

An applied phase-related equilibrium (APPLE) solver using only the Peng-Robinson equation of state is developed based on rigorous classical thermodynamics. The solver is theoretically and thermodynamically consistent with the stringent equilibrium criterion. It is mainly composed of phase stability and phase splitting calculations, which will be called routinely in the course of searching for the globally stable equilibrium state. It also makes use of various robust and efficient numerical methods. To demonstrate its performance, the solver is tested against various mixtures, such as oil and gas mixtures, hydrocarbon mixtures and hydrocarbon-nitrogen mixtures. Phase diagrams of these mixtures are constructed and verified with available experimental data or other researchers' calculations. Results show that the APPLE solver is reliable and fast to solve phase equilibrium problems, including three-phase equilibrium. Finally, its potential applications to droplet evaporation and computational fluid dynamics (CFD) calculations are discussed.