A fractionating column equipped with a steam-heated partial reboiler and total condenser (Figure 7.40) separates a mixture of 50 mol% A and 50 mol% B into an overhead product containing 90 mol% A and a bottoms of 20 mol% A. The column has three theoretical plates, and the reboiler is equivalent to one theoretical plate. When the system is operated at L/V = 0:75 with the feed as a saturated liquid to the bottom plate, the desired products are obtained. The steam to the reboiler is controlled and remains constant.

The reflux to the column also remains constant. The feed to the column is normally 100 kmol/h, but it was inadvertently cut back to 25 kmol/h. What will be the composition of the reflux and the vapor leaving the reboiler under these new conditions? Assume that the vapor leaving the reboiler is not superheated. Relative volatility is 3.0.

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Steam flow controller Flow controller Bottoms Figure 7.40 Data for Exercise 7.20. Feed Level controller Level controller Distillate