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How Do I Calculate Equilibrium Ratios (K Values) For The Isothermal Pt

vle phase equilibria rachford rice k values

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#1 Ahmad Abbasi

Ahmad Abbasi

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Posted 10 July 2019 - 02:52 AM

Hi everyone


For calculating the vapour fraction and phase compositions of a hydrocarbon mixture at given Pressure, Temperature and overall compositions, the rachford-rice equation needs to be solved. 

Because of the absence of phase composition (x-y) information in the beginning, we need starting values for the equilibrium K Ratios, (since the K values are composition dependent) for initialising the rachford rice solution procedure. Upon subsequent computation of phase composition, K values are reevaluated using the new information and the procedure is repeated until convergence.
I know about the raoult's approximation for K values (vapor pressure/System pressure) and the wilson correlation.
But they don't seem to be very helpful, because it often happens that for the initial estimated values of the K ratios, no feasible solution of the vapour fraction exists, which should ideally be between 0 and 1.
So I would like for any leads which would help me set good initial values for K ratios to ensure robust evaluation of the vapour fraction

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