Consider a binary mixture composed of hexane and heptane. This Demonstration computes and plots the isobaric vaporliquid equilibrium diagram, the equilibrium curve, the relative volatility, the value, the gasphase fugacity coefficients using the Soave–Redlich–Kwong equation of state (EOS), and the Poynting correction factor for userspecified values of the pressure. The Demonstration takes into account deviation from ideal behavior in the gas phase by including gas phase fugacity coefficients. Thus highpressure VLE data can be obtained. This Demonstration allows for the Poynting factor correction. Snapshots present calculations at a pressure approximately equal to 303.975 kPa. VLE data is computed using the following formula (the gammaphipoy equation): , where and are the vapor and liquid mole fractions of component , is the total pressure, is the saturation vapor pressure of component , is the vaporphase fugacity coefficient, and is the liquidphase activity coefficient, where and are determined using the Soave–Redlich–Kwong equation of state and the Wilson model, respectively; is the liquid molar volume of molecule determined using the Rackett equation.
For more information about pressure effects, the Rackett equation, and the Pitzer–Curl method, see [1] M. F. Doherty and M. F. Malone, Conceptual Design of Distillation Systems, New York: McGrawHill, 2001. [2] B. E. Poling, J. M. Prausnitz, and J. P. O'Connell, The Properties of Gases and Liquids, 5th ed., New York: McGrawHill, 2004. For more information about the SRK equation of state and the Wilson activity coefficients, see [3] S. I. Sandler, Chemical and Engineering Thermodynamics, New York: John Wiley & Sons, 1999. [4] J. R. Elliot and C. T. Lira, Introductory Chemical Engineering Thermodynamics, Upper Saddle River, NJ: Prentice Hall, 1999.
