Modeling approach for the high pressure solid-fluid equilibrium of asymmetric systems

S. B. RODRIGUEZ REARTES; CISMONDI DUARTE, M.; ZABALOY, M.

INDUSTRIAL & ENGINEERING CHEMICAL RESEARCH

AMER CHEMICAL SOC

Año: 2011 vol. 55 p. 3049 - 3059

0888-5885

In this work, we evaluate the potential of a modeling approach for describing the solid-fluid equilibria of highlyasymmetric mixtures over a wide pressure range. The model uses a mathematical expression for the fugacity of a pure heavycompound in solid state for which the reference state is the saturated solid under conditions of solid-liquid (melting) equilibriumatthe system temperature T. Such a reference state differs from a common choice, which corresponds to the pure solid underconditions of solid-vapor (sublimation) equilibrium at T. By construction, the present modeling approach matches the solidliquidequilibria at high concentration of the heavy component. We discuss and test here a parametrization strategy for avoiding thesimultaneous correlation of fluid-fluid and solid-fluid experimental data: first, the fluid-fluid equilibrium experimental data arecorrelated in the conventional way, and next, the solid-fluid equilibrium data are correlated by fitting a parameter that has noinfluence on the equation of state that describes the fluid phases. In this work, we study in detail the highly asymmetric systemmethaneþn-triacontane, for which experimental data are available over a wide range of conditions (Machado, J. J. B.; de Loos, T.W.Liquid-vapour and solid-fluid equilibria for the system methaneþtriacontane at high temperature and high pressure. Fluid PhaseEquilib. 2004, 222-223, 261-267). To model this system, we use a specific form of the present modeling approach. Such a specificmodel gives a good quantitative performance even at pressures in the order of 2000 bar. We also present additional modeling resultsfor two other systems, i.e., for methane þ n-eicosane and methane þ n-tetracosane, which are also highly asymmetric.