Simultaneous VLLE data correlation for ternary systems: Modification of the NRTL equation for improved calculations

Abstract

Simultaneous correlation of vapour-liquid-liquid equilibrium (VLLE) data is hardly ever attempted in literature with one common set of parameters for all the equilibrium regions present in the systems. It is common practice to obtain different sets of parameters for VLE, LLE and VLLE regions when experimental equilibrium data for ternary systems are fitted with a given model (e.g. an activity coefficient model for the liquid phase). Besides, when dealing with the correlation of VLE for ternary systems, it is quite frequent to obtain different sets of parameters for each one of the three binary subsystems from those obtained when exclusively binary VLE data are correlated. In

What does the NRTL model look like? Determination of boundaries for different fluid phase equilibrium regions

“…Specific mathematical restrictions quite useful have also been developed and applied successfully [43][44][45] in the thermodynamic modeling of type 0 (island), type 1, and 2 systems, for systems that had not been previously adjusted using the NRTL model or presented in the literature correlation results inconsistent with the experimenta l behavior of the system. Additionally, different extensions of classical models, such as the NRTL model, can also be found for complex LLE 44 or VLE [46][47][48][49] , and non-azeotropic or azeotropic VLLE [50][51][52] .…”

“…Additionally, different extensions of classical models, such as the NRTL model, can also be found for complex LLE 44 or VLE, [46][47][48][49] and non-azeotropic or azeotropic VLLE. [50][51][52] In the present article, a deep analysis of the NRTL model has been carried out, studying the existence of different liquid-liquid (LL) and vapor-liquid (VL) equilibrium regions and boundaries in the space defined by its binary interaction parameters, for obtaining a clear picture of this model, its possibilities and flexibility. In this sense, the different boundaries observed in the case of the LLE have been mathematically modeled, with the final aim of obtaining relationships between the binary interaction parameters that can be used as constraints for avoiding directly inconsistent results with the experimental behavior of the system under study, when the NRTL model is used in the correlation of experimental equilibrium data.…”

Identification of UNIQUAC binary interaction parameters in liquid-liquid equilibrium

“…However, local composition models show limited prediction capabilities of LLE of multicomponent systems equilibrium when the parameters are regressed only from binary data [5]. In particular, this class of models has severe limitations in the simultaneous correlation of LLE of ternary systems and VLE of the constituent pairs when the same set of parameters are used [40,41]. In order to overcome this drawback, modified versions of the original local composition models were proposed to simultaneously describe different phase equilibria [40,41].…”

Simplified Approach to Understanding, Evaluating, and Parameterizing the NRTL Model for the Description of Binary VLE: Tττ-VLE Approach

“…The benefits of the Tττ-VLE approach may be extended beyond binary VLE to the correlation of multicomponent and/or multiphase equilibria. For example, the simultaneous description of binary VL­(L)­E and ternary VL­(L)­E is known to be a difficult and complex problem, particularly sensitive to TDP initial guesses and non-randomness parameter selection. For such a case, including the Tττ-VLE insight may simplify this parameterization process by first identifying appropriate α ij values for the binary systems.…”