Correlation of high-pressure phase equilibria in the retrograde region with three common equations of state

Abstract

Phase equilibria in the retrograde regions were calculated for the methane — n-decane binary system and for a realistic natural-gas system (methane - Kensol-16). Calculations were performed using three equations of state (EOS): Peng-Robinson, Redlich-Kwong-Soave and Perturbed-Hard-Chain; calculations were compared to experiment. Liquid-drop-out curves and pressure-temperature diagrams were calculated between 301 and 369 K and pressures to 90 MPa. The binary system was represented best by the Peng-Robinson EOS. For the natural-gas system, the Perturbed-Hard Chain equation yielded the best results, although all equations of state showed appreciable deviations. Good results could only be obtained when binary coefficients were fitted to the experimental retrograde data. On a calcule l'equilibre de phase dans des regions retrogrades pour le systeme binaire methane — n-decane et pour un systeme au gaz naturel realiste (methane - Kensol-16). Les calculs ont ete effectues au moyen de trois equations d'etat, soit l'equation de Peng-Robinson, de Redlich-Kwong-Soave et de la chaine rigide perturbee; les calculs ont ete compares aux resultats experimentaux. Les courbes de la perte du liquide et les diagrammes des pressions et des temperatures ont ete calcules entre 301 et 369 K et les pressions jusqu'a 90 MPa. Le systeme binaire est mieux represente par l'equation d'etat de Peng-Robinson. Pour le systeme au gaz naturel, l'equation de la chaǐne rigide perturbee donne les meilleurs resultats, bien que toutes les equations d'etat montrent des ecarts appreciables. On a pu obtenir de bons resultats seulement lorsque les coefficients binaires ont ete adaptes aux donnees retrogrades experimentales.