Appendix: Solutions to Chapter Exercises ◾  121
Exercise 4.3
Since the feed contains 60% light key component, the vapor
above the feed tray would be expected to be above 60%.
This would give 50% light key component below the feed
stage, so the MRT would be expected to be below the
feed stage.
Exercise 4.4
The vapor composition above the feed stage would be
expected to be above 3% light key component, so the
feed stage would be the closest to 50% in the vapor
phase. All of the other stages would be expected to be
lower in concentration of light key component.
Exercise 5.1
A scheme that uses a temperature controller to manipulate
the steam flow rate to the reboiler. There may not even
be any reflux flow to the column. The top vapor temperature may be the MRT (most responsive temperature)
point.
Exercise 5.2
A scheme that uses a constant steam flow rate to the
reboiler pot and temperature controller that manipulates
the distillate flow rate. The reboiler pot temperature may
change the most, but the pot temperature would be an
indicator of the distillate composition.