Calculation of Vapor-Liquid Equilibrium

In the calculation of vapor-liquid equilibria, it is necessary to calculate separately the fugacity of each component in each of the two phases. The liquid and vapor phases require different techniques in this chapter we consider calculations for the vapor phase. 

At pressures to a few bars, the vapor phase is at a relatively low density, i.e., on the average, the molecules interact with one another less strongly than do the molecules in the much denser liquid phase. It is therefore a common simplification to assume that all the nonideality in vapor-liquid systems exist in the liquid phase and that the vapor phase can be treated as an ideal gas. This leads to the simple result that the fugacity of component i is given by its partial pressure, i.e. the product of y, the mole fraction of i in the vapor, and P, the total pressure. A somewhat less restrictive simplification is the Lewis fugacity rule which sets the fugacity of i in the vapor mixture proportional to its mole fraction in the vapor phase the constant of proportionality is the fugacity of pure i vapor at the temperature and pressure of the mixture. These simplifications are attractive because they make the calculation of vapor-liquid equilibria much easier the K factors = i i ... 

Equations 11 and 19 express the necessary liquid-phase activity coefficients for the calculation of vapor-liquid equilibria in the HCl-NaCl-HgO system. Equation 11 is very convenient... 

In this study, a thermodynamic framework has been presented for the calculation of vapor-liquid equilibria for binary solvents containing nonvolatile salts. From an appropriate definition of a pseudobinary system, infinite dilution activity coefficients for the salt-containing system may be estimated from a knowledge of vapor pressure lowering, salt-free infinite dilution activity coefficients, and a single system-dependent constant. Parameters for the Wilson equation may be determined from the infinite dilution activity coefficients. 

The final part of this monograph, Appendix E, describes programs that we include for the calculation of vapor-liquid equilibria in multicomponent mixtures. As in Appendix D, we also provide tutorials on the use of these programs. 

Feng, W. et al.. Calculation of vapor-liquid equilibria of high concentrated polymer solution by a modified SAFT equation of state, presented at the 9th International Conference on Rroperties and Phase Equilibria for Product and Process Design, Kurashiki, Japan, May 20-25, 2001, 2001. 

FUNDAMENTAL PRINCIPLES OF THERMODYNAMICS NEEDED IN THE CALCULATION OF VAPOR-LIQUID EQUILIBRIA AND ENTHALPIES OF MULTICOMPONENT MIXTURES... 

Consider the separation of 100 kmol/hr of an equimolar stream of tetrahydrofuran (THF) and water using pressure-swing distillation, as shown in Figure 7.37. The tower T1 operates at 1 bar, with the pressure of the tower T2 increased to 10 bar. As shown in the T-x-y diagrams in Figure 7.38, the binary azeotrope shifts from 19 mol% water at 1 bar to 33 mol% water at 10 bar. Assume that the bottoms product from T1 contains pure water and that from D2 contains pure THF. Also, assume that the distillates from T1 and T2 are at their azeotropic compositions. Determine the unknown flow rates of the product and internal streams. Note that data for the calculation of vapor-liquid equilibria are provided in Table 7.5. 

Calculation of Vapor-Liquid Equilibria Using g -Models... 

Calculation of Vapor-Liquid Equilibria Using g -Models 203 assuming that the value of the partial molar excess enthalpy of ethanol... 

For the calculation of vapor-liquid equilibria, an analytical expression for the fugacity coefficient is required. It can be derived according to Prausnitz ti al. [16]. With the material balances for each component... 

Shimoyama, Y Abeta, T Zhao, L, Iwai, Y. Measurement and calculation of vapor-liquid equilibria for methanol + glycerol and ethanol + glycerol... 

CALCULATION OF VAPOR-LIQUID EQUILIBRIA Table 3-2. K Values... 

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