Engineering Questions with Answers - Multiple Choice Questions
Distillation Design MCQ’s – Minimum Stages
1 - Question
The number of theoretical stages, depends on the
a) Stepping off the tray
b) Reflux ratio
c) Operating line
d) Flow rates
View Answer
Answer: b
Explanation: The number of theoretical stages depends on the reflux ratio R = L0/D, while the reflux ratio itself depends upon the operating line.
2 - Question
When R is infinite, the slope of this rectifying becomes
a) 0
b) 1
c) 0.5
d) Can’t be specifiedAnswer: b
Explanation: When R is infinity, the slope of this line becomes 1, while R is zero the slope of this line reaches infinity.
View Answer
Answer: b
Explanation: When R is infinity, the slope of this line becomes 1, while R is zero the slope of this line reaches infinity.
3 - Question
If x=0.4 and y =0.6633 and point xD (0.9, 0.9). Then estimate Rmin
a) 0.9
b) 0.4734
c) 0.4
d) 0.66
View Answer
Answer: a
Explanation: As Rmin/R+1 = (0.9-0.6633)/ (0.9/0.4) = 0.4734 then 0.4734/1-0.4734 = 0.9.
4 - Question
If distillate is 95%, and withdrawal is 4 and α=2.5. Estimate total number of tray?
a) 7.7
b) 10
c) 6.7
d) 5.7
View Answer
Answer: c
Explanation: Using Fenske’s equation and subsuming values we have 2.66/log 2.5= 6.7.
5 - Question
For non-ideal cases, to calculate number of stages we use
a) Point efficiency
b) Murphree efficiency
c) Tray efficiency
d) Overall efficiency
View Answer
Answer: b
Explanation: To calculate the number of stages in a non-ideal case, Murphree efficiency line is used instead of the ideal.
6 - Question
Minimum reflux ratio in a distillation column results in
a) Optimum no. of trays
b) Minimum reboiler size
c) Maximum condenser size
d) Minimum number of trays
View Answer
Answer: c
Explanation: Minimum reflux ratio in a distillation column results in maximum condenser size as inversely proportional.
7 - Question
In a tray column, Murphree efficiency
a) Exceed 100%
b) Equal to 100%
c) Can’t be specified
d) Depend upon cases given
View Answer
Answer: a
Explanation: In a non-ideal case, Murphree efficiency can exceed 100%, also it depends on the cases given and the feed type.
8 - Question
For value of m, the change in liquid concentration is independent of tray location if
a) L/V = 1
b) V/L =1
c) L/mV=1
d) Vm/L=1
View Answer
Answer: c
Explanation: At this condition slope of operating line equals to slope of equilibrium line, i.e. m = 1 this shows the steady state operation.
9 - Question
At minimum reflux, No. stages are
a) Unity
b) Infinite
c) Zero
d) Negative
View Answer
Answer: b
Explanation: Minimum reflux and stages are inversely proportional relation, while at maximum reflux the number of stages are zero.
10 - Question
Scaling up from pilot scale to industrial scale only increases
a) Feed rates
b) Reflux ratio
c) No. of stages
d) Composition
View Answer
Answer: a
Explanation: There will be no effect on internal property only feed rates are increased after scaling, Only dimensionless properties change like Re, Sc and Sh.