Solid–Liquid–Vapor Equilibrium Model Applied for a CH4–CO2 Binary Mixture

Abstract

A low-temperature process involving the formation of dry ice to separate carbon dioxide (CO2) from a CO2-containing mixture is proved to be energy efficient. An accurate prediction of the phase equilibria of the components is necessary for the development of such a process. The current work extended a model for simultaneous calculation of phase stability and flash computations for a multicomponent and multiphase system to a system involving the formation of dry ice. This study derived composition-independent correlations of solid–vapor and solid–liquid and introduced these correlations into a Gibbs energy minimization algorithm with the stability variable of phase in predicting the phase diagram of pure CO2 and the solid–fluid-phase equilibria of a methane (CH4)–CO2 binary mixture. A CO2 solid-phase equation of state (EoS) based on Gibbs free energy and a fluid-phase EoS based on Helmholtz free energy were used in this study. Experimental data were compiled for a CH4–CO2 mixture involving the solid–vapor,...