4.2 Double azeotrope-breaking criterion

Double azeotropic phenomena can be observed in the global phase diagram only in the vicinity of the crossing point of two straight azeotropic borders in (Z1, Z2) plane (Figures 8 and 9):

$$Z\_{2i} = \frac{\Psi^+ - \Psi^-}{2 + \Psi^+ + \Psi^-}, Z\_1^i = \frac{\Psi^+ + \Psi^-}{2 + \Psi^+ + \Psi^-}, \text{where } \Psi^\pm = \left(\frac{1 - Z\_4}{1 \pm Z\_3} - 1\right)\Lambda. \tag{18}$$

state. In general, the conflict can be described as follows: if interaction parameters are retrieved from the one class of properties, the prediction of other properties is doubtful in spite of validity of thermodynamic relationships. The final solution will

Phase equilibria in Н2О▬СО<sup>2</sup> system [20]. ● Experiment T = 275C. ▬ Best description of VLE data. °°°° von

This study provides a novel approach for defining the quantifiable estimation of boundary states and specific points which define changes of phase behavior. The global phase diagram technique is applied for deriving the analytical expressions and Pareto-based approach with fuzzy convolution scheme used for adequate eval-

There are no rigorous mathematical methods to construct adequate model without subjectively based solution due to a number of uncertainties and conflicts. To reduce the source of unavoidable uncertainty, the different compromise schemes of criteria convolution are considered. It is important to note that the selection of the

Below we provide results and discussion of application of the abovementioned approach for identification of the azeotrope- and double azeotrope-breaking criteria

depend on the problem setting and decision-maker subjective experience.

Neumann's coalition scheme [16]. ─ ─ Best description of critical curve.

Distillation - Modelling, Simulation and Optimization

convolution scheme is a subjective choice of the decision-maker.

4. Results and discussion

Figure 6.

80

uation of model parameters.

## Figure 7.

Azeotropic boundaries and their position in the global phase diagram. ● R507 (R125/R143a)—position in azeotropic sector (Z1 <sup>=</sup> 0.54 <sup>10</sup><sup>4</sup> ; Z2 = 0.07; Z3 <sup>=</sup> 0.01; Z4 = 0). ── Azeotropic boundaries for R125/ R143a mixture (Z3 = 0.01; Z4 = 0). ʘ R11/R142b—position in zeotropic sector (Z1 = 0.11; Z2 = 0.97 10<sup>3</sup> ; Z3 = 0.035; Z4 = 0). ………. Azeotropic boundaries for R11/142b mixture (Z3 = 0.035; Z4 = 0).

The best results were demonstrated by application of the Schwarzentruber-Renon and Wang-Sandler mixing rule [10] with three adjustable parameters (Figure 8). The use of local mapping shows good results of double azeotropic description at 323.05 К using the standard mixing rule (Figure 8).

4.3 Applications of ionic liquids in azeotrope mixture distillation

mapping approach [10]. equation of state approach. model [27].

Azeotrope-Breaking Potential of Binary Mixtures in Phase Equilibria Modeling

DOI: http://dx.doi.org/10.5772/intechopen.83769

behavior in the practicable range of parameters.

predictions of phase equilibria at high temperatures.

depicted in Figure 10.

Figure 9.

ionic liquids acting as absorbents.

83

The set of parameters for a given equation of state model univocally defines a global phase diagram and, consequently, evolution of phase behavior for binary mixture in a wide range of temperatures and pressures. Global phase diagram for model systems of components explores that binary mixture of industrial refrigerants with imidazolium (IL)-based ionic liquids does not experience azeotropic

Phase diagrams for R717-R125 mixture at 323.05 K. Standard mixing rule [24]. A double azeotrope near the crossing point of the two straight azeotropic borders in (Z1, Z2) plane. • Experimental data [23, 24]. Local

Distribution of critical points for major components of refrigerants [25–29] and hypothetical critical parameters of a number of imidazole-based ionic liquids is

Thanks to undetectable vapor pressure, ILs are considered as potential environmentally friendly candidates for replacing conventional solvents. The selective solubility properties of the ILs appeared for particular components of the mixtures and can be treated as extraction media for separation processes. Moreover, the increase of efficiency for absorption processes is promoted thanks to nonvolatile feature of

It shall be noted that at subcritical temperatures, IL may undergo thermal decomposition that causes uncertainty in assessment of critical parameters. Usually,

the available values of critical points of ionic liquids are derived from lowtemperature regions having extremely small saturation pressures. Computational procedures for finding model parameters are unstable. This can lead to errors in the

Figure 8. Phase diagrams for R717-R125 mixture at 323.05 K. Schwarzentruber-Renon mixing rule [23].

Azeotrope-Breaking Potential of Binary Mixtures in Phase Equilibria Modeling DOI: http://dx.doi.org/10.5772/intechopen.83769

Figure 9.

The best results were demonstrated by application of the Schwarzentruber-Renon and Wang-Sandler mixing rule [10] with three adjustable parameters (Figure 8). The use of local mapping shows good results of double azeotropic

; Z3 = 0.035; Z4 = 0). ………. Azeotropic boundaries for R11/142b mixture (Z3 = 0.035;

Azeotropic boundaries and their position in the global phase diagram. ● R507 (R125/R143a)—position in

R143a mixture (Z3 = 0.01; Z4 = 0). ʘ R11/R142b—position in zeotropic sector (Z1 = 0.11;

; Z2 = 0.07; Z3 <sup>=</sup> 0.01; Z4 = 0). ── Azeotropic boundaries for R125/

description at 323.05 К using the standard mixing rule (Figure 8).

Phase diagrams for R717-R125 mixture at 323.05 K. Schwarzentruber-Renon mixing rule [23].

Figure 7.

Z4 = 0).

Figure 8.

82

Z2 = 0.97 10<sup>3</sup>

azeotropic sector (Z1 <sup>=</sup> 0.54 <sup>10</sup><sup>4</sup>

Distillation - Modelling, Simulation and Optimization

Phase diagrams for R717-R125 mixture at 323.05 K. Standard mixing rule [24]. A double azeotrope near the crossing point of the two straight azeotropic borders in (Z1, Z2) plane. • Experimental data [23, 24]. Local mapping approach [10]. equation of state approach. model [27].
