Design of separation equipment for the chemical processes need accurate data of thermodynamic properties, such as excess enthalpy (h(E)), excess Gibbs free energy (g(E)), and vapor-liquid equilibrium (VLE). Because of the difficulties obtaining all the required data experimentally, the designer often turns to the estimation models. It is often expected that an estimation model should be simple in mathematical form and be applicable to calculate the different thermodynamic properties simultaneously and accurately. To meet such goal, a modification of the well-known NRTL model was proposed in this work. The modifications were discussed in the manuscript. More than one different isotherm data of h(E) and g(E) were used separately to correlate the temperature-dependent parameters Delta g(11), Delta g(12), and alpha(12) and the parameters of an additional composition function in this modified NRTL model. And the identical h(E) and g(E) data were also used simultaneously to correlate all the parameters of the NRTL model of Demirel et al. (1992). Those estimated parameters of these two models were then used to estimate: isothermal binary h(E), g(E), VLE, and isobaric binary and ternary VLE. Comparisons were then made among the differently estimated results and the experimental data from literature. It is found that the proposed modifications indeed improved the capability of the NRTL model of Demirel et al. for estimating h(E), g(E), and VLE simultaneously. Finally, it should be mentioned that this modified model can be easily extended to handle multicomponent mixtures merely with the constituent binary pair parameters.
JOURNAL OF THE CHINESE INSTITUTE OF CHEMICAL ENGINEERS