A New Molecular Simulation Algorithm to Calculate Vapour-Liquid Equilibrium and Its Applications

Abstract

CO2 capture from point sources is an important tool for ameliorating global warming and climate change. Among the many methods for CO2 capture is the use of solvents for reactive absorption. Knowledge of vapor-liquid equilibrium (VLE) properties of the flue-gas in equilibrium with a CO2-loaded solvent is crucial, but experiments to measure these properties are often time-consuming and expensive. We present a novel, computationally efficient algorithm to predict VLE properties using fundamental thermodynamic equations and molecular simulation methodology in the case of a pure fluid. This approach is very general and only requires Monte Carlo (MC) and molecular dynamics (MD) software that can correctly calculate chemical potentials. We also introduce a data smoothing procedure and a general method for calculating uncertainty on simulation results. The algorithm is validated for pure Lennard-Jones fluid and SPC/E water using existing literature results. It is then applied to several anaesthetic gases for which the VLE properties have not been measured. The algorithm can be extended to more complex pure fluids, including ionic liquids, and to mixtures.