January 25, 2006
siretb:
While not disagreeing with most of Professor Suppes’ article that you referenced, I would make a simple point: Nowhere does he mention that use of NRTL for liquid systems suffers from the FUNDAMENTAL FLAW that the third interaction parameter (alpha) CANNOT be found from LLE data alone.
Therefore, I am skeptical about his blanket recommendations for LLE systems, preferring to rely instead my own study of the theory, backed by experience in numerous commercial applications.
I would suggest instead reliance on Professor John M. Prausnitz's numerous publications and books on the subject. Two good sources are:
(1) Prausnitz, Lichtenthaler, and Gomes de Azevedo: "Molecular Thermodynamics of Fuid Phase Equilibria" (3rd Edition, Prentice Hall, 1999). This is the most complete discussion of the theory to date.
(2) Prausnitz, et al, "Computer Calculations for Multicomponent Vapor-Liquid and Liquid-Liquid Equilibria" (Prentice Hall, 1980). This book discusses some significant theoretical and practical advantages for UNIQUAC over the earlier models.
As just about everyone in the business knows, Prausnitz is the pre-eminent authority on this subject, and the NRTL, UNIQUAC, and UNIFAC models were all developed under his supervision. Also, I would respectfully ask you to consider that if UNIQUAC did not have an outstanding theoretical basis, the UNIFAC group contribution method (which relies on the foundations laid by UNIQUAC) would not have achieved the outstanding success it has demonstrated for over 25 years. In fact, the originator (Professor Fredenslund) continued refining this method until his untimely death, and that work has been continued very ably by his successors (Rasmussen, Gani, and others at Lyngby, Denmark and Gmehling in Germany), to this day.
