26.49 Stripping Tower and Direct Steam Injection. A liquid feed at the boiling point con- tains 3.3 mol % ethanol and 96.7 mol % water and enters the top tray of a stripping tower, Saturated steam is injected directly into the liquid in the bottom of the tower. The overhead vapor that is withdrawn contains 99% of the alcohol in the feed. Assume equimolar overflow for this problem. Equilibrium data for mole fraction of alcohol are as follows at 101.32 kPa abs pressure (1 atm abs): y 0 0 0.0296 0.033 0.250 0.270 0.0080 0.020 0.0750 0.175 (a) For an infinite number of theoretical steps, calculate the minimum moles of steam needed per mole of feed. (Note: Be sure to plot the q line.) (b) Using twice the minimum moles of steam, calculate the number of theo- retical steps needed, the composition of the overhead vapor, and the bot- toms composition. Ans. (a) 0.121 mol steam/mol feed: (b) 5.0 theoretical steps, xp = 0.135.x, = 0.00033