A valve-tray fractionating column containing eight theoretical plates, a partial reboiler equivalent to one theoretical plate, and a total condenser is in operation separating a benzene-toluene mixture containing 36 mol% benzene at 101 kPa. Under normal operating conditions, the reboiler generates 100 kmol of vapor per hour. A request has been made for very pure toluene, and it is proposed to operate this column as a stripper, introducing the feed on the top plate as a saturated liquid, employing the same boilup at the still, and returning no reflux to the column. Equilibrium data are given in Exercise 7.13.

(a) What is the minimum feed rate under the proposed conditions, and what is the corresponding composition of the liquid in the reboiler at the minimum feed?

(b) At a feed rate 25% above the minimum, what is the rate of production of toluene, and what are the compositions in mole percent of the product and distillate?