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Drawing PT-phase envelopes and calculating critical points for multicomponent systems using flash calculations

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Objectives. This study aims to draw PT-phase envelopes and calculate the critical points for multicomponent systems using flash calculations.

Methods. Flash calculations with an equation of state and a mixing rule were used to construct phase envelopes for multicomponent systems. In general, the methodology uses the Soave–RedlichKwong equation of state and Van der Waals mixing rules; and the Peng–Robinson equation of state with Wong–Sandler mixing rules and the non-random two-liquid activity coefficient model.

Results. The method was applied to the following mixtures: ethane (1)–butane (2) (four different compositions); ethane (1)–propane (2) (four different compositions); butane (1)–carbon dioxide (2) (three different compositions); C2C3C4C5C6 (one composition); isobutane–methanol–methyl tertbutyl ether–1-butene (one composition); and propylene–water–isopropyl alcohol–diisopropyl ether (one composition).

Conclusions. Our results agreed to a large extent with the experimental data available in the literature. For mixtures that contained CO2 , the best results were obtained using the PengRobinson equation of state and the Wong–Sandler mixing rules. Our methodology, based on flash calculations, equations of state, and mixing rules, may be viewed as a shortcut procedure for drawing phase envelopes and estimating critical points of multicomponent systems.

About the Author

L. A. Toro
National University of Colombia; Autonomous University of Manizales
Russian Federation
Luis A. Toro, Associate Professor, Ph.D. (Eng.), Doctor of Philosophy, Mathematics, Department of Mathematics and Statistics, National University of Colombia (headquarters Manizales, Manizales-Caldas, Colombia) [Departamento de Matemáticas y Estadística, Universidad Nacional de Colombia sede Manizales]; Autonomous University of Manizales, Manizales-Caldas, Colombia [Departamento de Física y Matemáticas, Universidad Autónoma de Manizales, Antigua Estación del Ferrocarril]


1. Michelsen M.L. Calculation of Phase Envelopes and Critical Points for Multicomponent Mixtures. Fluid Phase Equilib. 1980;4(1-2):1-10.

2. Stradi A.B., Brennecke F.J., Khon P.J., Stadtherr A.M. Reliable Computation of Mixture Critical Points. AIChE J. 2001;47(1):212-221.

3. Heidemann R.A., Khalil A.M. The Calculation of Critical Points. AIChE J. 1980;26(5):769-779.

4. Henderson N. Freitas L. Platt M.G. Prediction of Critical Points: a new methodology using global optimization. A. I. Ch. E. Journal. 2004;50(6):1300-1314.

5. Freitas L., Platt G., Hénderson N. Novel approach for the calculation of critical points in binary mixtures using global optimization. Fluid Phase Equilib. 2004;225:29-37.

6. Justo-García D.N., García-Sanchez F. Cálculo de Puntos Críticos de sistemas multicomponentes utilizando optimización golbal. XX Congreso Nacional de Termodinámica. Apizaco, Tlaxcala, 5–9 de Septiembre de 2005. P. 342-366 (in Spanish).

7. Sánchez-Mares F., Bonilla-Petriciolet A. Cálculo de Puntos Críticos empleando una estrategia de optimización global estocástica. Afinidad. 2005;63(525):396-403 (in Spanish).

8. Goffe W.L, Ferrier G.D., Rogers J. Global Optimization of statistical functions with simulated annealing. J. Econometrics. 1994;60(1-2):65-99.

9. Corana A., Marchesi M., Martini C., Ridella S. Minimizing multimodal functions of continuous variables with simulated annealing algorithm. ACM Trans. Math. Software. 1987;13(3):262-280.

10. Tabrizi F.F., Nasrifar Kh. Application of predictive equations of state in calculating natural gas phase envelopes and critical points. Journal of Natural Gas Science and Engineering. 2010;2(1):21-28.

11. Cardona C.A., Sánchez C.A., Gutiérrez L.F. Destilación Reactiva: Análisis y Diseño Básico. Manizales, Colombia: Universidad Nacional de Colombia; 2007 (in Spanish).

12. Reid R.C., Prausnitz J.M., Poling B.E. The Properties of Gases and Liquids. 4th Edition. New York: McGraw-Hill; 1987. 741 p.

13. Justo-García D.N., García-Sánchez F., Díaz-Ramírez N.L., Romero-Martínez A. Calculation of critical points for multicomponent mixtures containing hydrocarbon and nonhydrocarbon components with the PC-SAFT equation of state. Phase Fluid Equilib. 2008;265:192-194.

14. Jun Cai, Ying Hu, Prausnitz J.M. Simplified critical-point criteria for some multicomponent systems. Chem. Eng. Sci. 2010;65(8):2443-2453.

15. Akasaka R. Calculation of the critical point for mixtures using mixture models based on Helmholtz energy equations of state. Fluid Phase Equilib. 2008;263(1):102-108.

16. Alfradique M.F., Castier M. Critical points of hydrocarbon mixtures with the Peng-Robinson, SAFT, and PC-SAFT equations of state. Fluid Phase Equilib. 2007;257(1):78-101.

17. Horstman S., Fisher K., Gahmeling J. Experimental determination of critical points of pure components and binary mixtures using a flow apparatus. Chem. Eng. Technol. 1999;22(10):839-842.<839::AID-CEAT839>3.0.CO;2-L

18. Chien-Bin Soo, Thévenau P., Coqulet C., Ramjugernath D., Richon D. Determination of critical points of pure and multicomponent mixtures using a “dynamic-synthetic” apparatus. J. of Supercritical Fluids. 2010;55(2):545-553.

19. Holland Ch.D. Fundamentos de destilación de mezclas multicomponentes. Limusa, Noriega Editores; 1992. 200 p. (in Spanish).

20. Seader J.D, Henley E.J. Separation Process Principles. 2nd Edition. John Wiley and Sons, Inc; 2006. 800 p.

21. Smith J.M., Van Ness H.C., Abbott M.M. Introducción a la Termodinámica en Ingeniería Química. McGraw-Hill; 2007. 836 p. (in Spanish).

22. Peng D., Robinson D.D. A New Two-Constant Equation of State. Ind. Eng. Chem. Fund. 1976;15(1):59-64.

23. Tester J.W., Modell M. Thermodynamics and Its Applications, 3rd Edition. Prentice Hall. 1996; 960 p.

Supplementary files

1. Ethane (1)–n-butane (2) mixtures. Phase envelope using SRK EoS and VdW MR. a) z = [0.5605 0.4395]; b) z = [0.4402 0.5598]; c) z = [0.1496 0.8504]; d) z = [0.2990 0.7010].
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2. This is to certify that the paper titled Drawing PT-phase envelopes and calculating critical pointsfor multicomponent systems using flash calculations commissioned to Enago by Luis Alberto Toro has been edited for English language and spelling by Enago, an editing brand of Crimson Interactive Inc.
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Phase envelopes and critical points were determined for several multicomponent systems using flash calculations. The calculations employed the Soave−Redlich−Kwong (SRK) equation of state with Van der Waals (VdW) mixing rules, Peng−Robinson (PR) equation of state with Wong−Sandler (WS) mixing rules, and the non-random two-liquid (NRTL) activity coefficient model.


For citations:

Toro L.A. Drawing PT-phase envelopes and calculating critical points for multicomponent systems using flash calculations. Fine Chemical Technologies. 2020;15(1):46-54.

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