Modelling liquid–liquid equilibria for island type ternary systems

Olaya, Marı́a del Mar; Reyes‐Labarta, Juan A.; Velasco, Raul; Ibarra, I.; Marcilla, A.

doi:10.1016/j.fluid.2007.12.010

Cited by 25 publications

(34 citation statements)

References 11 publications

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“…We have found conditions for the NRTL binary parameters that allow the formation of island type ternary systems [62]. From a systematic study, it was concluded that the main requirement for the ternary LLE island region was the existence of a binary subsystem with a very low g M min value (dissimilar) compared to the other two binary subsystems.…”

Section: B Nrtl Binary Parameter Value Restrictions To Reproduce Islmentioning

confidence: 99%

“…The representation of the sum of the conjugated binary interaction parameters (A ij + A ji ) versus the g M min value [62] showed that the negative values of such sum corresponded to the dissimilar binary and the positive sum corresponded to the other two binary subsystems. These conclusions led to the following restrictions for the dimensionless parameters, which are used in the equilibrium data regression of this type of system: Fig.…”

Section: B Nrtl Binary Parameter Value Restrictions To Reproduce Islmentioning

confidence: 99%

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GE Models and Algorithms for Condensed Phase Equilibrium Data Regression in Ternary Systems: Limitations and Proposals

Gomis¹

2011

TOTHERJ

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Phase equilibrium data regression is an unavoidable task necessary to obtain the appropriate values for any model to be used in separation equipment design for chemical process simulation and optimization. The accuracy of this process depends on different factors such as the experimental data quality, the selected model and the calculation algorithm. The present paper summarizes the results and conclusions achieved in our research on the capabilities and limitations of the existing G E models and about strategies that can be included in the correlation algorithms to improve the convergence and avoid inconsistencies. The NRTL model has been selected as a representative local composition model. New capabilities of this model, but also several relevant limitations, have been identified and some examples of the application of a modified NRTL equation have been discussed. Furthermore, a regression algorithm has been developed that allows for the advisable simultaneous regression of all the condensed phase equilibrium regions that are present in ternary systems at constant T and P. It includes specific strategies designed to avoid some of the pitfalls frequently found in commercial regression tools for phase equilibrium calculations. Most of the proposed strategies are based on the geometrical interpretation of the lowest common tangent plane equilibrium criterion, which allows an unambiguous comprehension of the behavior of the mixtures. The paper aims to show all the work as a whole in order to reveal the necessary efforts that must be devoted to overcome the difficulties that still exist in the phase equilibrium data regression problem.

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Section: B Nrtl Binary Parameter Value Restrictions To Reproduce Islmentioning

confidence: 99%

Section: B Nrtl Binary Parameter Value Restrictions To Reproduce Islmentioning

confidence: 99%

GE Models and Algorithms for Condensed Phase Equilibrium Data Regression in Ternary Systems: Limitations and Proposals

Gomis¹

2011

TOTHERJ

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“…Explicit references to the use of parallel computing to fit equation of state (EOS) parameters could not be found in the literature. Although fitting EOS parameters is a seemingly routine problem, it is at least as complicated as fitting parameters of excess Gibbs energy models (Olaya et al, 2008, Staudt et al, 2013, and Soares and Gerber, 2013) and poses several challenges, which are often overlooked. Those relevant to this work are discussed in the next paragraphs.…”

Section: Introductionmentioning

confidence: 99%

Fitting equation of state parameters in parallel computers

Castier

Checoni

Zuber

2014

Braz. J. Chem. Eng.

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-This work compares two strategies to fit parameters of equations of state in parallel computers, emphasizing solutions that require few changes to existing sequential programs. One strategy uses the conventional Nelder-Mead algorithm coupled with parallel objective function evaluation (SSPO). The other strategy uses a parallel Nelder-Mead algorithm coupled with sequential objective function evaluation (PSSO). The PSSO strategy, which executes parallel one-dimensional searches during each iteration, is simpler to implement and converged to parameter sets with objective functions smaller than those obtained by the SSPO strategy. The SSPO strategy produced speedups consistent with the number of processes used and is more suitable when many processors are available. Both strategies are potentially useful and choosing between them is a matter of convenience, depending on the problem at hand. With parallel computers increasingly available, the easy implementation and convenience of these two strategies should appeal to developers and users of thermodynamic models.

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“…In previous papers [22][23][24][25][26] robust calculation methods, based on the topological analysis of the Gibbs energy of mixing function (g M = ( mix G)/RT ), were developed. The topological analysis of g M is a valuable tool that allows deducing the geometrical conditions that the g M function has to fulfil, in order to reproduce certain equilibrium behaviour in the whole composition diagram, and clearly evidences any existing calculation inconsistency.…”

Section: Introductionmentioning

confidence: 99%

“…The previously developed methods [22][23][24][25][26] resulted in a robust computer program that has allowed the determination of the capabilities and limitations of the NRTL equation [27] for correlating equilibrium data between condensed phases in ternary systems. NRTL equation was selected as representative of thermodynamic local composition models, and is one of the most frequently used model.…”

Section: Introductionmentioning

confidence: 99%

Methods for improving models for condensed phase equilibrium calculations

Marcilla

Olaya

Serrano

et al. 2010

Fluid Phase Equilibria

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a b s t r a c tLocal composition models like UNIQUAC, NRTL and the UNIFAC group contribution method are used the world over in the synthesis and design of separation processes, as well as for a large number of other applications of industrial interest. They can qualitatively describe the equilibrium behaviour of systems of different complexities but, sometimes, not with the precision required for the design of separation equipment. Regrettably, this precision is not even achieved for the LLE of many conventional type 1 and some type 2 ternary systems. High deviations in correlation results are not rare, thus showing that more capable and flexible models are needed. The analysis of the topology of the Gibbs energy of mixing function, and therefore the knowledge of the geometrical conditions that this function has to fulfil, is a valuable tool that has allowed avoiding inconsistencies in the use of the existing methods, to ascertain their capabilities and limitations to reproduce complex systems and additionally to suggest new models that improve the flexibility and accuracy needed. In this work, a simple equation based on the NRTL model, that takes into account such topological conditions, is proposed and its capabilities are tested with selected systems.

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Modelling liquid–liquid equilibria for island type ternary systems

Cited by 25 publications

References 11 publications

GE Models and Algorithms for Condensed Phase Equilibrium Data Regression in Ternary Systems: Limitations and Proposals

GE Models and Algorithms for Condensed Phase Equilibrium Data Regression in Ternary Systems: Limitations and Proposals

Fitting equation of state parameters in parallel computers

Methods for improving models for condensed phase equilibrium calculations

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