Rigorous VLLE Model

In this method, a mixed A -value is defined as the ratio of the mole fraction of a component in the vapor to its mole fraction in the mixed liquid phase (Schuil and Bool, 1985). Applied to an equilibrium stage or a flash drum, the phase equilibrium is solved using the mixed /f-valucs instead of the usual vapor-liquid X-values to determine the flow rates and compositions of the vapor and the total liquid. The liquid phase split is then calculated on the basis of A -values for each liquid phase to determine the flow rates and compositions of the two liquid phases. An energy balance may also be included to determine the temperature or the heat transfer for the unit. 

With the molar rates of the two liquid phases designated as L and L and the mole 

When this equation is used in the definition of the mixed -value, the following 

The 7 -values for each liquid phase with the vapor are given as 

When these equations are combined with Equation 2.27, the following is obtained for the mixed A -Value  

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