Experimental measurements and thermodynamic modeling of hydrate dissociation conditions in CO2 + THF + NaCl plus water systems

Experimental and thermodynamic modeling results for hydrate dissociation conditions in carbon dioxide + THF + NaCl + water systems were reported. Four different aqueous solutions of THF and NaCl (0.05 mass fraction of NaCl (0.05 mass fraction of THF: namely solution 1; 0.10 mass fraction of NaCl, 0.05 mass fraction of THF: namely solution 2; 0.05 mass fraction of NaCl, 0.20 mass fraction of THF: namely solution 3; 0.10 mass fraction of NaCl, 0.20 mass fraction of THF: solution 4) were studied in this work. An isochoric pressure - search method was used to perform the measurements. The equilibrium dissociation conditions are reported in the ranges of (0.92-3.89) MPa and (280.9-292.9 K). NaCl acts as an inhibitor in all of the experiences, while THF acts as a promoter. Comparing our data with the same system in the absence of NaCl, a shift is observed toward the left in the equilibrium curve. In addition, this kind of shifting to the left in the curves is more observable at high pressures. In order to predict the equilibrium conditions, a thermodynamic model was developed which uses the Peng-Robinson equation of state and e-UNIQUAC activity coefficient model, for gas/vapor, aqueous electrolyte solution and promoter, respectively. The average absolute deviation of pressure for the model results is in the range of 0.06-0.08 MPa, which confirm the model accuracy. (C) 2019 Elsevier Ltd.