High Pressure Phase Equilibrium of (Solvent + Salt + CO2) Systems by the Extended Peng-Robinson Equation of State

Abstract

<em>An extended Peng-Robinson equation of state (EPR-EOS) is used to model the vapor-liquid equilibrium (VLE) in systems containing (water + NaCl + CO₂), (water + methanol + NaCl + CO₂), (water + Na₂SO₄ + CO₂) and (water + NH₄Cl + CO₂). The binary and ternary interaction parameters between salt and solvent are adjusted to experimental mean solvent activity of salts (NaCl and Na₂SO₄). For the system containing (water + Na₂SO₄ + CO₂), the EPR-EOS is used to predict the P-T diagram when the moles of Na₂SO₄ in 1 kg water are 0.25, 0.5 and 1. The calculated results for the (water + Na₂SO₄ + CO₂) system by the extended PR-EOS are compared with the correlation results by Anderko-Pitzer EOS. The average absolute deviation of (ΔP/P_exp) % between the correlation results by Anderko-Pitzer EOS and experimental data is 8.4 % while this value for extended PR-EOS is 6 %. The P-x diagram for (water + NH₄Cl + supercritical-CO₂) system at temperatures (333 and 353 K) are also obtained and compared with the calculation results by VTPRLIFAC model. The average absolute deviation between calculation results by VTPRLIFAC model and experimental data is 7.8 % but this value for our calculations is 6.2 %.</em>