Abstract
Understanding the stability of gas hydrates in aqueous electrolyte solutions is pivotal for industrial applications, particularly in oil and gas extraction and desalination processes. Many existing thermodynamic models, while predicting the influence of salts on hydrate dissociation temperatures, are often limited because they require numerous fitting parameters and, hence, are only tailored to specific hydrate systems. Here, we present a model for hydrate stability calculations with 40% fewer parameters but equivalent accuracy to existing approaches. This model has now been extended to include a physically based description of the impact of electrolyte solutions on hydrate equilibria. Utilizing an extended Debye–Hückel equation, we first accurately describe osmotic coefficients for 191 unique single strong electrolyte solutions. Zdanovskii’s rule is then employed to predict osmotic coefficients in mixed electrolyte scenarios without any additional parameters. Finally, the predicted osmotic coefficients are used to correct water fugacities calculated via the cubic-plus-association equation of state. The resulting cage-specific hydrate equilibrium electrolyte (CaSH-e) model reliably describes multicomponent mixtures of hydrocarbon and aqueous compounds that include industrially important thermodynamic inhibitors such as methanol and monoethylene glycol. The CaSH-e model’s performance is shown to either match or exceed that of current existing models, like CPA-hydrates in MultiFlash 7.0 (CPAHYD-MF) and the Ballard and Sloan model in CSMGem, particularly for chloride and bromide salt mixtures.
