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CHAPTER 15 DISTILLATION SYSTEMS
1. Two basic tower designs include:
a. packed and tray
b. plate and packed
c. bubblecap and sieve
d. valve and packed
e. a & b
2. Overlap can be minimized by:
a. refluxing
b. increasing pressure
c. reboiling
d. a & c
3. High bottoms temperature in a distillation tower are controlled by :
a. increase over head flow and decrease bottoms flow
b. decrease overhead flow and increase bottoms flow
c. stop feed flow and cut bottom temperature
d. open side-streams
4. List and describe the three technology periods of distillation.
a.
b.
c.
5. Feed composition changes have very little impact on the energy balance but significant
impact on the material balance.
a. true
b. false
6. Calculate the total vapor pressure exerted by the mixture: 25% hexane 20.6 psia @
175F, 25% heptane 8.8 psia @ 175F, and 50% benzene 14.7 psia @ 176 F. Give answer
in psia.
a. 14.7 psia
b. 44.1 psia
c. 22.05 psia
d. 34.7 psig
7. Puking is most closely related to:
a. reduced partial pressure
b. excessive vapor pressure
c. low temperature
d. high temperature
8. The process of vaporizing liquids at lower temperatures by reducing pressure:
a. azeotropic distillation
b. fractional distillation
c. vacuum distillation
d. adsorption distillation
9. Tube shaped funnels that allow fluid transfer between plates in a tower:
a. riser
b. bubble-cap
c. downcomer
d. sieve
10. The temperature at which the heaviest component begins to boil:
a. IBP- initial boiling point
b. FBP- final boiling point
c. ABP- average boiling point
d. Dew point
11. Excessive liquid flowing down a tower that blocks vapor flow up the tower:
a. puking
b. flooding
c. surging
d. reflux
12. A binary mixture contains:
a. lighter hydrocarbons
b. is heavier than a ternary mixture
c. two or more components
d. three compounds in a mixture
13. Boil-up rate is defined as:
a. the temperature at which a liquid turns to vapor
b. the vapor-liquid balance returned to tower from the reboiler
c. the vapor-liquid reflux balance returned to tower from overhead accumulator.
d. the total amount of vapor moving up the column.
14. Draw a distillation tower system. Include (3) three control loops, preheater, condenser,
kettle reboiler, distillation column.
15. What is the composition of side stream #2z?
16. The sum of the products entering the column equals the sum leaving:
a. energy balance
b. fractional balance
c. material balance
d. total balance
17. Packed towers use specially designed packing materials to reduce surface area during
the distillation process:
a. true
b. false
18. Distillation columns have two major types of separation grids: plate and packing. Plate
towers have the following tray types:
a.
b.
c.
19. Packed towers have the following types of packing:
a.
b.
c.
20. Liquid distillate returned to the tower is called:
a. boil-up rate
b. reflux rate
c. total reflux
d. incomplete separation
Analyze the following process variables and decide if they are related to energy (E) or material
(M) balance.
21. steam loop on feed pre-heater. ____
22. feed flow rate. ____
23. overhead condenser. ____
24. reflux rate. ____
25. boil-up rate. ____
26. reboiler. ____
27. side stream flow. ____
28. bottoms flow. ____
29. overhead flow. ____
30. The temperature at which a liquid mixture turns to vapor:
a. boil-up rate
b. IBP
c. FBP
d. boiling point
e. dew point
31. What is the overhead composition?
32. The upper section of the tower is referred to as:
a. feed section
b. rectifying section
c. enriching section
d. stripping section
e. b & c
33. Condensed tower product that is pumped back into a tower to increase product purity and
control temperature:
a. overlap
b. reflux
c. side-stream
d. accumulation
34. The condensed gas taken from a distillation tower is called:
a. residuum
b. distillate
c. condensate
d. distillation
35. Distillation is best defined by the following statement:
a. the separation of components in a mixture by tower segregation
b. the fractional separation of a binary mixture by tray filtration
c. the azeotropic process designed to separate hydrocarbons by fractional boiling
points.
d. the separation of components in a mixture by boiling point
36. The lower section of the tower is referred to as:
a. feed section
b. rectifying section
c. enriching section
d. stripping section
e. b & c
37. The tray located below the inlet feed line is called the:
a. mid section tray
b. pumping section tray
c. feed tray
d. valve tray
38. Each tray in a distillation column has a different molecular structure.
a. true
b. false
39. The varying temperatures across the tower:
a. temperature gradient
b. temperature profile
c. temperature overlap
d. temperature delta
40. List three process variables that can be used to break a flood:
a.
b.
c.
41. List the critical steps used to start-up a distillation system. (DEXTER?)
a.
b.
c.
d.
e.
f.
g.
h.
i
j
k
l
m
n
o
p
q
r
s
t
u
v
w
x
y
z
42. Refer to Bottom VLE graphic: End of Exam
On a VLE chart the bottom curve is referred to as:_________________ .
43. A ternary mixture:
a. lighter hydrocarbons
b. is heavier than a ternary mixture
c. two or more components
d. three compounds in a mixture
44. When a heat exchanger is used to convert all of the overhead vapors to liquid, it is called:
a. normal overhead condenser
b. total reflux
c. total condenser
d. partial condenser
45. Refer to Bottom VLE graphic
On a VLE chart the top curve is referred to as:_________________ .
46 All of the following are principles of distillation except:
a. heat increases vapor pressure
b. pressure increases boiling point
c. vacuum decreases boiling point
d. forms and breaks molecular bonds
47. The larger the difference between partial pressures the harder it is to separate the
fractions by boiling point.
a. true
b. false
48. Using information from question 6, calculate the % component in vapor of hexane:
a. 20%
b. 25%
c. 30%
d. 35%
49. Vapor distillate returned to the tower is called:
a. boil-up rate
b. reflux rate
c. total reflux
d. incomplete separation
50. The vapor medium suspended above a boiling mixture is enriched with the components
that have the lowest boiling points.
a. true
b. false
51. Heat that cannot be sensed or measured:
a. latent
b. sensible
c. kinetic
d. potential energy
52. Incomplete separation of components in a mixture:
a. overlap
b. puking
c. temperature gradient
d. overloading
53. Refer to Bottom VLE graphic: End of Exam
The initial bubble point temperature for a butane mole fraction of 40%
is:_________________ .
54. The temperature at which a liquid boils and forms vapors is referred to as the:
a. boiling point
b. specific temperature
c. bubble point
d. dew point
55. The Vapor Liquid Equilibrium diagram is primarily used for :
a. a condition or state where the rate of evaporation (liquid changing to vapor)
equals the rate of condensation (vapor changing to a liquid).
b. A & C
c. visualizing a condition where a liquid and it’s vapor (gas phase) are in
equilibrium with each other.
d. components in a binary mixture exert partial pressures that are equal.
56. The Reflux Ratio is best defined as :
a. the amount of overhead product returned to the column as reflux in relation to the
amount of overhead taken off to storage.
b. careful control of column top temperature and product purity.
c. reflux rate divided by product rate
d. A & C
Answer Chapter 15 Distillation Systems
