Optimizing front-end purification units for LNG production: A novel modelling approach for predicting solid-fluid equilibria applied to benzene solubility

Abstract

Literature solid-fluid equilibrium data dealing with the solubility of benzene in 22 pure components and mixtures of interest for LNG production have been compared to values predicted by a thermodynamic package composed by a fluid-phase model and a solid-phase model (i) under the assumption that the solid phase is composed by pure benzene, and (ii) without further regression of parameters within both the fluid-phase and solid-phase models.The fluid-phase model is a reference equation of state explicit in the reduced Helmholtz Energy and based on the multi-fluid approximation for the calculation of thermodynamic properties of fluids and fluid mixtures, having the same functional form of the GERG-2008 equation of state, whereas the solid-phase model is a recently published Gibbs Energy equation of state for solid benzene.The predicted solubilities of solid benzene in the liquid phase of light components (methane + ethane, ethane, and propane) and heavy components (potential solid co-formers) are in a good agreement with literature values for almost all the systems under investigation.The two equations of state provide therefore a reliable model for the prediction of benzene freeze-out conditions in LNG mixtures, leading to front-end purification units of liquefied natural gas plants properly tailored to meet high plant availability (reducing maintenance operations and shutdown) while achieving financial targets (energy efficient purification processes, higher margins in LNG sale).