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

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
Explanation: When R is infinity, the slope of this line becomes 1, while R is zero the slope of this line reaches infinity.

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

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

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

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

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

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

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

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