Aspen Physical Property System - Physical Property Models

standard RKS alpha function, except that the Grabovsky-Daubert alpha
function is used for H2: � = 1.202 exp(-0.30228xTri)
References
J. F. Boston and P.M. Mathias, "Phase Equilibria in a Third-Generation Process
Simulator" in Proceedings of the 2nd International Conference on Phase
Equilibria and Fluid Properties in the Chemical Process Industries, West Berlin,
(17-21 March 1980), pp. 823-849.
P. M. Mathias, "A Versatile Phase Equilibrium Equation-of-state", Ind. Eng.
Chem. Process Des. Dev., Vol. 22, (1983), pp. 385–391.
P.M. Mathias and T.W. Copeman, "Extension of the Peng-Robinson Equationof-state
To Complex Mixtures: Evaluation of the Various Forms of the Local
Composition Concept", Fluid Phase Eq., Vol. 13, (1983), p. 91.
O. Redlich and J. N. S. Kwong, "On the Thermodynamics of Solutions V. An
Equation-of-state. Fugacities of Gaseous Solutions," Chem. Rev., Vol. 44,
(1949), pp. 223–244.
J. Schwartzentruber and H. Renon, "Extension of UNIFAC to High Pressures
and Temperatures by the Use of a Cubic Equation-of-state," Ind. Eng. Chem.
Res., Vol. 28, (1989), pp. 1049–1055.
J. Schwartzentruber, H. Renon, and S. Watanasiri, "K-values for Non-Ideal
Systems:An Easier Way," Chem. Eng., March 1990, pp. 118-124.
G. Soave, "Equilibrium Constants for a Modified Redlich-Kwong Equation-ofstate,"
Chem Eng. Sci., Vol. 27, (1972), pp. 1196-1203.
C.H. Twu, W.D. Sim, and V. Tassone, "Getting a Handle on Advanced Cubic
Equations of State", Chemical Engineering Progress, Vol. 98 #11 (November
2002) pp. 58-65.
Huron-Vidal Mixing Rules
Huron and Vidal (1979) used a simple thermodynamic relationship to equate
the excess Gibbs energy to expressions for the fugacity coefficient as
computed by equations of state:
Equation 1 is valid at any pressure, but cannot be evaluated unless some
assumptions are made. If Equation 1 is evaluated at infinite pressure, the
mixture must be liquid-like and extremely dense. It can be assumed that:
Using equations 2 and 3 in equation 1 results in an expression for a/b that
contains the excess Gibbs energy at an infinite pressure:
2 Thermodynamic Property Models 79
(1)
(2)
(3)
(4)