Interfacial tensions of systems comprising water, carbon dioxide and diluent gases at high pressures: Experimental measurements and modelling with SAFT-VR Mie and square-gradient theory

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• 作者：Y.T. Florence Chow ; Daniel K. Eriksen ; Amparo Galindo ; Andrew J. Haslam ; George Jackson ; Geoffrey C. Maitland ; J.P. Martin Trusler ; ^{m.trusler@imperial.ac.uk" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Carbon dioxide ; Interfacial tension ; SAFT-VR ; Square-gradient theory ; Water
• 刊名：Fluid Phase Equilibria
• 出版年：2016
• 出版时间：15 January 2016
• 年：2016
• 卷：407
• 期：Complete
• 页码：159-176
• 全文大小：1385 K

文摘

Experimental interfacial tensions of the systems (H₂O + CO₂), (H₂O + N₂), (H₂O + Ar), (H₂O + CO₂ + N₂) and (H₂O + CO₂ + Ar) are compared with calculations based on the statistical associating fluid theory for variable range potentials of the Mie form (SAFT-VR Mie) in combination with the square-gradient theory (SGT). Comparisons are made at temperatures from (298 to 473) K and at pressures up to 60 MPa. Experimental data for the systems (H₂O + CO₂), (H₂O + N₂) and (H₂O + CO₂ + N₂) are taken from the literature. For the (H₂O + Ar) and (H₂O + CO₂ + Ar) systems, we report new experimental interfacial-tension data at temperatures of (298.15–473.15) K and pressures from (2 to 50) MPa, measured by the pendant-drop method. The expanded uncertainties at 95% confidence are 0.05 K for temperature, 70 kPa for pressure, 0.016 × γ for interfacial tension in the binary (Ar + H₂O) system and 0.018 × γ for interfacial tension in the ternary (CO₂ + Ar + H₂O) system.

The parameters in the SAFT-VR Mie equation of state are estimated entirely from phase-equilibrium data for the pure components and binary mixtures. For pure water, the SGT influence parameter is determined from vapour–liquid surface-tension data, as is common practice. Since the other components are supercritical over most or the entire temperature range under consideration, their pure-component influence parameters are regressed by comparison with the binary interfacial-tension data. A geometric-mean combining rule is used for the unlike influence parameter in mixtures without incorporation of adjustable binary parameters. The SAFT-VR Mie + SGT approach is found to provide an excellent correlation of the surface tension of water and of the interfacial tensions of the binary systems comprising H₂O with CO₂ or Ar or N₂. When applied to predict the interfacial tensions of the two ternary systems, generally good results are found for (H₂O + CO₂ + N₂) while, for (H₂O + CO₂ + Ar), the theory performs well at high temperatures but significant deviations are found at low temperatures. Overall, the SAFT-VR Mie + SGT approach can be recommended as a means of modelling the interfacial properties of systems comprising water, carbon dioxide and diluent gases.