An approximate yet standard procedure, the perturbation method, is used to solve analytically the equation for the steafiy state fractionation of multicomponent and complex mixtures in non-ideal cascades. It is shown that the formulae are easily adaptable to numerical evaluation.
The perturbation method is particularly useful when the calculations for a system which is close to ideal must be made. The perturbation method may be considered as a nonideality superimposed on the ideal solution. The ideal solution may be thought of as the ilrat approximation to the solution' while the perturbation is the second approximation. Higher order approximations are diihcult to carry out.
R&sumCS
-Pour n%oudre analytiquement l'tquation relative B la distillation continue de melanges B composants multiples et complexes, les auteurj utilllnt la methode de perturbation, mdthode classique, bien qu'approehee. La methode de perturbation s'adapte parfaitement aux evaluations numeriques : elle est particulitrement utile quand on Btudie un systeme assimilable B un systeme ideal. Bile put Ire consideree comme une correction d&at rt5el sur l'hypothbe de la solution ideale. La solution id&ale correspond a une approximation du premier ordre et la perturbation a une approximation du second ordre. II es diicile d'utiliir des approximations d'ordre plus &eve. 1.