Simulations of vapor–liquid phase equilibrium and interfacial tension in the CO₂–H₂O–NaCl system

Abstract

Direct interfacial molecular dynamics simulations are used to obtain the phase behavior and interfacial tension of CO2–H2O–NaCl mixtures over a broad temperature and pressure range (50°C ≤ T ≤ 250°C, 0 ≤ P ≤ 600 bar) and NaCl concentrations (1–4 mol/kg H2O). The predictive ability of several existing water (SPC and TIP4P2005), carbon dioxide (EPM2 and TraPPE), and sodium chloride (SD and DRVH) models is studied and compared, using conventional Lorentz–Berthelot combining rules for the unlike‐pair parameters. Under conditions of moderate NaCl molality (∼1 mol/kg H2O), the predictions of the CO2 solubility in the water‐rich and CO2‐rich phase resemble those in the CO2–H2O system [Liu et al., J Phys Chem B. 2011;115:6629–6635]. Consistent with our previous work, the TraPPE/TIP4P2005 model combination gives the best overall performance in predicting coexistence composition and pressure in the water‐rich phase. Critical assessments are also made on the ranges of temperature and pressure where particular model combinations work better. The dependence of the interfacial tension on temperature and pressure is better predicted by the TraPPE/TIP4P2005 and EPM2/SPC models, whereas the EPM2/TIP4P2005 model overestimates this property by 10–20%, possibly due to the inadequacy of the combining rules. It is also found that the interfacial tension increases with salt concentration, consistent with experimental observations. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3514–3522, 2013

Thermodynamic and Transport Properties of H2O + NaCl from Polarizable Force Fields

“…51 A typical Gibbs-ensemble MC simulation took about 300 h using 16 2.6 GHz Intel Sandybridge cores. The statistical uncertainties of vapor pressures were calculated from block averages of a single run.…”

Monte Carlo simulations of H2O–CaCl2 and H2O–CaCl2–CO2 mixtures

“…For example, the properties of aqueous NaCl solutions and CO 2 solubility in H 2 O-NaCl systems have been studied by experiments [2,3], thermodynamic models [4,5], and simulations [6][7][8]. Phillips et al [2] conducted experimental measurements of density and vapor pressures of NaCl solutions at a range of temperatures and pressures.…”

“…For the ternary H 2 O-NaCl-CO 2 mixture, Vorholz et al [7] studied CO 2 solubility by Gibbs ensemble Monte Carlo simulation. Molecular dynamics simulations were also performed by Liu et al [8] for this ternary system to obtain the CO 2 solubility as well as the vapor-liquid surface tension.…”

Molecular simulation of equal density temperature in CCS under geological sequestration conditions

“…Vorhozl et al 17,18 used the Gibbs ensemble method to predict the phase equilibrium curve of the CO 2 -water system and the solubility of the CO 2 -water-NaCl system. Liu et al 19,20 used the histogram-reweighting grand canonical Monte Carlo method to simulate a wider temperature range of the CO 2 -water system and performed comprehensive tests of several existing water and CO 2 models. Orozco et al 21 used fixed point charge models to study the liquid density of NaCl-water solution.…”