Multiphase equilibria of waxy systems with predictive equations of state and a solid solution model

Abstract
A thermodynamic model is developed to predict the vapor-liquid, solid-liquid,
solid-vapor and solid-liquid-vapor equilibria of systems containing methane with
waxy components. The model takes the advantages of equations of state to
describe the vapor and liquid phases. The solid phase is described by Coutinho’s
activity coefficient model, i.e., the solid phase is assumed to be orthorhombic
solid solution. Impact of pressure on the solid phase is included by coupling
solid-liquid Clapeyron relationship with Poynting correction factor. While no
adjustable parameter is used, the model satisfactorily predicts the phase
boundaries of the synthetic and real systems resembling gas condensate
mixtures for wide ranges of pressure and temperature.