Select thermodynamic models for process simulation
A Practical Guide to a Three Steps Methodology

Example 4-4: Behaviour of a methane + n-decane mixture and its models

Experimental values of vapour-liquid equilibrium of methane+ n-decane mixture are available from Lin et al. (1979)[1]. The large difference in molecule size results in an asymmetric mixture with entropic deviation from ideality. In addition, since methane is largely supercritical, a critical point appears at intermediate concentration.

As shown on figure 1, the bubble points (solid dots) and the dew points (empty dots) show a large gap between both curves, indicating the experimental difficulty in locating the critical point. The Peng-Robinson model with BIP equal to zero can adequately predict the dew curve, although it excessively under-predicts the bubble curve. With the BIP predicted by the Kordas et al. method, the bubble line is better fitted with a small loss of precision for the dew line. The Jaubert et al. predictive method PPR78 is even better for the bubble line but is worse for the dew line representation.

image Figure 1: Phase envelope of methane + decane equilibrium (experimental and models) at 510.95 K.


[1] LIN H.M., SEBASTIAN H.M., SIMNICK J.J., CHAO K.C., Gas-liquid equilibrium in binary mixtures of methane with N-decane, benzene, and toluene, Journal of Chemical & Engineering Data, 1979, 24, n°2, p. 146-149.