Question

11. Your company has a distillation column ready to install. The column has one feed, a
partial condenser and a partial reboiler. Vapor product is drawn directly from the condenser.
Find the number of degrees of freedom with this column. HINT there is no stream divider
after the condenser.
12. Using a total condenser with a reflux ratio of 2, the heat load on the condenser is
(a) Twice the heat of vaporization of the distillate.
(b) Equal to the heat of vaporization of the distillate.
(c) Three times the heat of vaporization of the distillate.
(d) Depends on the equilibrium between the vapor and liquid phases.
13. Vapor flowing up from a bubble cap tray number N
(a) Is in equilibrium with the liquid flowing down from the tray above (N+1).
(b) Is in equilibrium with the liquid flowing down from the same tray (N).
(c) Is at the dew point.
(d) Both (b) and (c).
3
14. The difference point on a Ponchon Savarit construction with one feed is found
(a) On a construction line vertically up from the distillate composition.
(b) On a construction line vertical down from the bottoms product composition.
(c) On a construction line vertical up from the feed composition.
(d) Both (a) and (b).
15. Tie lines on a Ponchon Savarit construction
(a) Represent material balances for each tray.
(b) Connect vapor and liquid compositions in equilibrium from the same tray.
(c) Connect points on the bubble and dew point curves .
(d) Both (b) and (c).

Answer 1

12. In a total condenser with a reflux ratio of 2, the heat load on the condenser depends on the equilibrium between liquid and vapour phases. This is because the reflux ratio depends on many factors like feed rate, feed and product compositions, reflux ratio, number of theoretical plates and latent heat of vaporisation.

13. Vapors flowing up the bubble cap tray number N is in equilibrium with the liquid flowing through the same tray N. And also, the vapors are at its dew point as on removal of even a very small amount of heat, the vapors get condensed.

11.