New correlations for predicting sieve tray efficiencies

Sieve trays have been widely used in distillation for many years. The tray efficiency is often predicted by using empirical or semi-empirical correlations. Extensive studies have been made in developing these correlations, but almost all correlations to date still suffer same limitations.; One aspect which has not been adequately considered is the effect of surface tension and its gradients on tray efficiencies. Most experimental studies have shown that the effect of surface tension and its, gradients can substantially affect the tray efficiency by influencing the interfacial area and the rare of mass transfer in the dispersion. However, no theoretical basis has been established to include those effects in the prediction of tray efficiencies.; Two new semi-empirical correlations have been developed to predict the number of individual phase transfer units in which the effect of surface tension and its gradients was considered explicitly. The correlations were developed under distillation conditions where the number of vapour and liquid mass transfer units were determined based on the same interfacial area. The formulation of an enhancement factor with the Marangoni-index embodies the effect of surface tension gradients. Six binary systems were selected in this investigation in which a wide range of physical properties was covered with different combinations of hydrocarbons, alcohols and aqueous solution. The applicability of the correlations in all systems with different surface tension changes was successful.; The experimental results of this work indicate that the new correlations produce good accuracy in the prediction of tray efficiencies.