An equation of state for solid–liquid–vapor equilibrium applied to gas processing and natural gas liquefaction

The analytical equation of state for the representation of solid, liquid, and vapor (SLV-EoS), proposed by Yokozeki, has been applied to the representation of phase equilibrium of substances involved in gas processing and in the natural gas liquefaction process. A new procedure for the parameters regression has been set up in order to achieve a better representation of phase equilibrium. This new procedure has been applied for obtaining new parameters for the original SLV-EoS equation, with the van der Waals attractive term. Different attractive terms have also been studied, in order to achieve an optimized representation for solid–liquid, solid–vapor, and liquid–vapor equilibrium of pure substances. The obtained equations have been used for representing phase equilibrium of carbon dioxide, methane, ethane, and propane in a wide range of temperature and pressure. The new equations have also been applied to the description of phase equilibrium, involving also solid phases, of the mixtures methane–carbon dioxide, ethane–carbon dioxide, and propane–carbon dioxide.