Equation of state SAFT-CP for vapour–liquid equilibria and mutual solubility of carbon dioxide and water

ABSTRACT

The statistical associating fluid theory (SAFT) was proposed first in 1990, and has been extended to various forms for the calculation of thermodynamic properties of complex systems, such as oil reservoir fluids, polar systems, polymers, electrolytes, near-critical systems, interfacial phenomena, solids and even biomaterials. SAFT-CP (critical point) has been established for nonpolar fluids in 2001 with excellent expression of thermodynamic properties across critical points. It was extended later for polar and associating fluids with the addition of just a dipole–dipole interaction, which leads simple calculation procedure without an association term. In this article SAFT-CP is applied to carbon dioxide, water and their mixture. Vapour–liquid equilibria for pure components CO₂ and H₂O, CO₂ solubility in water and H₂O solubility in dense CO₂ are analysed. Expression of pure CO₂ properties is improved with the dipole–dipole interaction term used, while expression of pure water is a little bit improved with the non-spherical degree parameter less than 1.0. For the high asymmetry in polarity and association between CO₂ and H₂O molecules, the Stryjek–Vera combining rule is used with different temperature-dependent parameters. With the quadratic temperature-dependent parameters, the mutual solubilities in the system are calculated with good agreement with experimental ones over the wide range of temperature as 298–474 K and of pressure as 0.1–70 MPa.

KEYWORDS:

• Statistical associating fluid theory
• critical point
• solubility
• carbon dioxide
• water

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [grant number 51134017]; National Science and Technology Support Program of China [grant number 2015BAC04B01]; State Key Laboratory of Chemical Engineering of China [grant number SKL-ChE-12Z01].