Effects of accuracy of equation of state for pure components on prediction of binary vapor-liquid equilibria.

The constants in the modified BWR state equations for light hydrocarbons, nitrogen and hydrogen were re-determined from volumetric data selected for their even distribution over wide ranges of temperature and pressure, and the effects of the accuracy of these equations on the prediction of vapor-liquid equilibria for binary systems consisting of the above components were investigated. It was found that the accuracy of vapor-liquid equilibrium prediction is improved greatly, even when the conventional mixing rules are used, by increasing the accuracy of the state equation for each pure component. No binary parameters in mixing rules were needed for the above binary systems, even those containing a super-critical component, if the highly improved equations of state were applied. This suggests that re-examination of the accuracy of the state equations is necessary prior to studying the effectiveness of the conventional mixing rules.