Simulated and experimental thermodynamic investigations for the selection of suitable hydrate formers for water treatment

Abstract

Hydrate-former selection is important for achieving high water recovery and impurity removal efficiencies in hydrate-based water treatment. This study presents thermodynamic approaches for selecting a hydrate former suitable for water treatment. Here, carbon dioxide (CO2) and 1,1,1,2-tetrafluoroethane (HFC-134a) were investigated as hydrate formers. Simulated studies of the hydrate formation by four formers were conducted at different NaCl concentrations (0.00, 1.75, and 3.50 wt%) to predict the phase-equilibrium conditions. A commercial software (CSMGem) was used for the calculation of the hydrate-phase equilibrium of CO2. The Hu–Lee–Sum (HLS) correlation predicted the three-phase equilibrium of CO2 and HFC-134a. The results indicated that HFC-134a is a good candidate for water treatment using gas hydrates. The phase equilibrium results calculated based on the HLS correlation and the CSMGem software confirmed the experimental results obtained using an isochoric method. The predicted thermodynamic properties provide essential information for the process design in water treatment applications.