Engineering Questions with Answers - Multiple Choice Questions

Distillation Design MCQ’s – Theoretical Stages

1 - Question

An ideal distillation stage is the one that
a) Operates at steady state
b) Operates at High temperature
c) Operates at Low pressure
d) Operates at high pressure

View Answer

Answer: a
Explanation: An ideal distillation stage operates at steady state has liquid product and vapor product, i.e. Liquid rate equals the gas flow rate.

2 - Question

When heat is supplied to bottom of liquid stage to vaporize a portion it is called
a) Condensing
b) Boil up
c) Cooling
d) Desalting

View Answer

Answer: b
Explanation: Such operations used in stripping section called as Boil up, the boiler is used as a heat exchanger to reheat the condensed liquid.

3 - Question

 When Cooling is applied to condense a part of overhead product it is called
a) Reflux
b) Dew point
c) Boil Up
d) Relative BP

View Answer

Answer: a
Explanation: Such operations is called as Rectifying stages and called Reflux, It is also called the ratio of distillate and liquid flow rate.

4 - Question

 When rectifying and stripping both are combined in single stage process this is
a) Differentiation
b) Fractionation
c) Recycle
d) Purging

View Answer

Answer: b
Explanation: Such is an operation is also called Fractional Distillation, The moles of the components reduce with respect to time in this operation.

5 - Question

Minimum number of trays can be calculated using
a) Bernoulli’s Eon
b) Henry’s Law
c) Fenske’s Equation
d) Homotomy Equation

View Answer

Answer: c
Explanation: Minimum number of trays can be easily calculated using Fenske’s equation with use of relative volatility.

6 - Question

The external reflux ratio can be defined as
a) L0/D
b) D/L
c) D0/L
d) V/L

View Answer

Answer: d
Explanation: The reflux ratio is defined as the ratio of liquid flow rate and distilled flow rate, also this is called as the slope of rectifying line.

7 - Question

The boil up ratio can be defined as ratio of
a) V/L
b) D/V
c) V/W
d) L/W

View Answer

Answer: c
Explanation: Boil up ratio is the ratio of vapor leaving the rebuilder to liquid at bottom product, also it is defined as the slope of stripping line.

8 - Question

Optimum reflux ratio ranges between
a) 2 to 5
b) 2 to 3
c) 1.0 to 1 .5
d) 1.0 to 2.5

View Answer

Answer: c
Explanation: Best optimum reflux is between ranges. 1.0<R<1.5, as it is very close to unity the optimum conditions are best condition to operate.

9 - Question

 If stages are fixed, then Reflux ratio
a) Decreases
b) Increases
c) Equates to 0
d) Approaches infinity.

View Answer

Answer: b
Explanation: The stages and the reflux ratio are directly proportional, while when it approaches to 0 the distillate is not withdrawn and if infinite all feed is withdrawn.

10 - Question

If reflux increases, then the cost of operation
a) First increases then decreases
b) Goes on increasing
c) Approaches infinity
d) First decreases then increases

View Answer

Answer: a
Explanation: The reflux ratio follows an exponential relation with cost, cost grows exponentially as the reflux increases and can cause increase in cost.

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