(153f) Modelling of Phase and Interfacial Behavior of Ternary Mixtures

Sabine Enders

Karlsruhe Institute of Technology, Institute of Technical Thermodynamics and Refrigeration Engineering, Engler-Bunte-Ring 21, D-76131 Karlsruhe, Germany.

Email: sabine.enders@kit.edu

Key words: vapor-liquid equilibria, oil recovery, density gradient theory, interfacial tension, density profiles, PCP-SAFT-EOS

Abstract:

My stay at the TU Delft in the group of Applied Thermodynamics in 1996 inspired me to study interfacial phenomena. The reason for this situation was the well-known paper by Cornelisse, Peters and de Swaan Arons [1] dealing with the application of the density gradient theory in combination with the Peng-Robinson Equation of state (PR-model). In this paper, is written â??However, in the previous section it was concluded, that the scaling behavior of gradient theory with the PR model did not agree with the experiments. Although from the gradient theory interfacial tension calculations have been illustrated by examples for pure the carbon dioxide and carbon dioxide/butane system, the conclusions are believed to be generally applicable. This was assumed, because the error in the results is probably caused by the PR model. In any event, the results presented here demonstrate that accurate predictions will at least require an equation of state with proper scaling behavior in the critical region.â??

In the last twenty years, I studied phase- and interfacial properties related to different phase equilibria (liquid-liquid [2] or liquid-vapor [3]), different binary [4] and ternary mixtures [5] and the application of different equations of state (SAFT [5], PCP-SAFT [6,7], lattice cluster theory [8], Sanchez-Lacombe [2]).

The interfacial properties play an important role in the field of oil recovery and in separation technology, especially for extraction. In this contribution the phase equilibria and the involved interfacial properties for binary and ternary mixture representing the situation for oil recovery will discussed, where the focus is the dependence of interfacial properties, like interfacial tension and relative enrichment in the interface, on pressure. Additionally, the impact of sulphur containing components, like H₂O and SO₂, on the interfacial tension will be discussed [9]. For the investigation of this effect, thermodynamic modelling is very important, because no experimental data are available in the public literature. The following ternary mixtures: CO₂+H₂S+CH₄, CO₂+H₂S+C₇H₁₆, CO₂+SO₂+CH₄, CO₂+SO₂+C₇H₁₆ were investigated over a large pressure and temperature range. It turns out that the presence of the sulfur containing molecules leads to a decrease of the interfacial tension in comparison to the corresponding binary system [9] at the same temperature and pressure. At low pressures, CO₂ as well as H₂S will enriched at the interface in the CO₂+H₂S+C₇H₁₆ mixture, where the enrichment effect of CO₂ is more pronounced.

References

[1] P.M.W. Cornelisse, C.J. Peters, J. de Swaan Arons, Fluid Phase Equilibria 82 (1993) 119.

[2] S. Enders, K. Quitzsch, Langmuir 14 (1998) 4606.

[3] O.G. Nino-Amezquita, S. Enders, Ph. T. Jaeger, R. Eggers, Ind. Eng. Chem. Res. 49 (2010) 592.

[4] S. Enders, H. Kahl, Fluid Phase Equilibria 263 (2008) 160.

[5] H. Kahl, S. Enders, Fluid Phase Equilibria 172 (2000) 27.

[6] E. Schäfer, F. Horbach, S. Enders, Journal of Chemical & Engineering Data 59 (2014) 3003.

[7] E. Schäfer, S. Enders, G. Sadowski, Fluid Phase Equilibria 362 (2014) 151.

[8] T. Zeiner, P. Schrader, S. Enders, D. Browarzik, Fluid Phase Equilibria 302 (2011) 321.

[9] A. Danzer, C. Bühl, S. Enders, Fluid Phase Equilibria 416 (2016) 94.