Interfacial tensions of the (CO2+N2+H2O) system at temperatures of (298 to 448)K and pressures up to 40MPa

• Published in: The Journal of chemical thermodynamics Vol. 93; pp. 392 - 403
• Main Authors: Chow, Y.T. Florence, Maitland, Geoffrey C., Trusler, J.P. Martin
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.02.2016
• Subjects: Carbon dioxide; Carbon storage; Density; High pressure; Interfacial tension; Nitrogen; Water; Water; Carbon storage; Interfacial tension; Carbon dioxide; Nitrogen; Density; High pressure
• ISSN: 0021-9614; 1096-3626
• DOI: 10.1016/j.jct.2015.08.006

[Display omitted] •Interfacial tension of (CO2+N2+H2O) and (N2+H2O) measured.•Temperatures up to 448K and pressures up to 40MPa.•Pendent-drop method used with calculated density difference between coexisting phases.•Literature data for (CO2+H2O) reappraised with improved estimates of the density difference between phases.•Results for the ternary system are compared with a simple combining rule. Interfacial tension measurements of the (CO2+N2+H2O) and (N2+H2O) systems are reported at pressures of (2 to 40)MPa, and temperatures of (298.15 to 448.15)K. The pendant drop method was used in which it is necessary to know the density difference between the two phases. To permit calculation of this difference, the compositions of the coexisting phases were first computed from a combination of the Peng–Robinson equation of state (applied to the non-aqueous phase) and the NRTL model (applied to the aqueous phase). Densities of the non-aqueous phase were computed from the GERG-2008 equation of state, while those of the aqueous phase were calculated knowing the partial molar volumes of the solutes. The expanded uncertainties at 95% confidence are 0.05K for temperature, 0.07MPa for pressure, 0.019γ for interfacial tension in the binary (N2+H2O) system; and 0.032γ for interfacial tension in the ternary (CO2+N2+H2O) system. The interfacial tensions in both systems were found to decrease with both increasing pressure and increasing temperature. An empirical correlation has been developed for the interfacial tension of the (N2+H2O) system in the full range of conditions investigated, with an average absolute deviation of 0.20mN·m−1, and this is used to facilitate a comparison with literature values. Estimates of the interfacial tension for the (CO2+N2+H2O) ternary system, by means of empirical combining rules based on the coexisting phase compositions and the interfacial tensions of the binary sub-systems, (N2+H2O) and (CO2+H2O), were found to be somewhat inadequate at low temperatures, with an average absolute deviation of 1.9mN·m−1 for all the conditions investigated. To enable this analysis, selected literature data for the interfacial tensions of the (CO2+H2O) binary system have been re-analysed, allowing for improved estimates of the density difference between the two phases. The revised result on eleven isotherms were fitted with empirical models that generally represent the data to within 1mN·m−1.