Theoretical results about Rachford-Rice equation for an isothermal two-phase flash of multicomponent systems are presented. The alternative method finds all the roots of the equation by means of an Associated Polynomial in the vapor fraction. All real roots are located and the negative flash condition is applied to the study cases. Associated polynomial significantly reduces calculations by eliminating asymptotes, which prevent the convergence of traditional numerical methods. Some numerical examples are shown in order to assess the method, principally when Rachford-Rice equation fails. Besides, proposed methodology is compared with other methods and variants of Rachford-Rice equations obtaining same results with no computational effort and its implementation is straightforward.

给出了多组分系统等温两相闪蒸过程中有关Rachford-Rice方程的理论结果。另一种方法是通过蒸气分数中的相关多项式来找到方程式的所有根。找出所有真实根，并将负闪光条件应用于研究案例。相关多项式通过消除渐近线显着减少了计算量，从而避免了传统数值方法的收敛。为了评估该方法，给出了一些数值示例，主要是在Rachford-Rice方程失效时。此外，将所提出的方法与其他方法和拉赫福德-赖斯方程的变体进行了比较，无需计算即可获得相同的结果，并且其实现也很简单。