Application of Modified NRTL Models for Binary LLE Phase Characterization

Phase characterization of liquid–liquid mixtures is required in numerous chemical process calculations. The original nonrandom two-liquid (NRTL) model is used widely in describing liquid–liquid equilibria (LLE). Application of this model, however, is affected by (a) lack of reliable parameters, (b) a wide range of acceptable parameter values, and (c) highly correlated parameters. Recent modifications of the NRTL model, the two-parameter modified NRTL, "mNRTL2", and the one-parameter NRTL, "mNRTL1", address these issues and show promising results for characterizing LLE systems. The accuracy of these two modifications was tested in our previous studies using a comprehensive vapor–liquid equilibria (VLE) experimental database(1) and a representative LLE database.(2) In the current study, the efficacy of these modified NRTL models is assessed for the proper characterization of LLE phase conditions and attributes, including phase stability, miscibility, and consolute point coordinates. For the systems considered, the modified NRTL models produce acceptable LLE characterization results in comparison to those of the original NRTL; albeit, the results from the mNRTL2 model are more precise than those of the mNRTL1 model.