Nonequimolar Effects in Multicomponent Distillation

In the treatment of transport processes during distillation, most textbooks (e.g., Sherwood et al., 1975) assume that conditions of equimolar countertransfer hold. That is. 

We can see from Eqs. 11.5.15 that the total flux will vanish only if the following two conditions are satisfied 

This requirement is often met in practice because the heat transfer coefficients in the vapor and liquid phases are such that they will wipe out any temperature gradients locally, say on a tray. In any event, the contribution of the Sq term to the total flux is likely to be small because it is small in comparison to the average latent heat terms A or A.  

The second requirement (Eq. 11.5.25) is that the molar latent heats of vaporization of the constituent species be identical. Now, molar latent heats of many compounds are close to one another, but the differences are not zero. Let us examine the effect of such small differences in the latent heats on the interfacial rates of transfer. Example 11.5.1 demonstrates the importance of taking into account nonequimolar effects in distillation. 

Determine the fluxes and in the vapor phase during the distillation of the 

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