Modeling of fluid phase equilibria with two thermodynamic theories: Non-random hydrogen bonding (NRHB) and statistical associating fluid theory (SAFT)

Two thermodynamic theories, the non-random hydrogen bonding (NRHB) and the statistical associating fluid theory (SAFT) are used to model phase equilibria of pure fluids and mixtures. The scaling parameters for several non-associating as well as self-associating fluids are estimated, for both equations of state, by fitting experimental vapor pressure and saturated liquid density data over a wide temperature range. For the correlation of phase equilibria of mixtures, one binary interaction parameter is calculated for each of the systems examined. Analysis of the results shows that NRHB model is more accurate for the correlation of saturated liquid densities and vapor pressures of most pure fluids. Also, NRHB is clearly more accurate than SAFT for the correlation of phase equilibria of binary mixtures that contain one self-associating fluid, while the accuracy of the two theories is comparable for the case of non-associating mixtures.