An Alternative Model for Calculating Dissociation Pressure of CO₂ Hydrate in Electrolyte Solutions

CO2 hydrate is essential for carbon capture, utilization, and storage (CCUS) and water desalination, where electrolytes significantly affect its phase behavior. This study proposes an alternative thermodynamic model to calculate the three-phase (hydrate-liquid water-vapor) equilibrium for CO2-electrolyte-water systems. The Chen-Guo model is employed for modeling the hydrate phase. The Soave–Redlich–Kwong equation of state (SRK EOS) is used for determining gas fugacity. The impact of electrolytes is incorporated through the Pitzer–Mayorga–Zavitsas-hydration (PMZH) model, with a mixing rule accounting for water–electrolyte interactions. To validate the alternative model, we measure the three-phase (hydrate-liquid water-vapor) equilibrium of CO2 hydrate in mixed electrolyte solutions using the isochoric pressure-search method. The optimized model parameters for various mixed electrolyte solutions are provided to further enhance the calculation accuracy. The proposed model accurately calculates the three-phase (hydrate–liquid water–vapor) equilibrium of CO2 hydrate in both single and mixed electrolyte solutions, achieving an overall absolute average relative deviation (AARD) of 3.44%.