# Distillation Design Questions and Answers – Minimum Reflux

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This set of Distillation Design Multiple Choice Questions & Answers (MCQs) focuses on “Minimum Reflux”.

1. The underwood’s equation, implies of using trial and error for finding
a) Θ
b) α
c) β
d) Ω

Explanation: We find θ which must lie between relative volatilities of the keys, while α denotes the relative volatility of components.

2. The ratio of the key components is essentially equal to their ratio in liquid feed, was given by?
a) Underwood
b) Gilliland
c) Brown-Martin
d) Fenske

Explanation: This method was based on the observation that a feed pinch point, Fenske is based on feed compositions of the system.

3. Colburn Method can be used to calculate the _____ in a binary system.
a) Minimum Reflux
b) Maximum Reflux
c) Minimum Trays
d) Maximum Trays

Explanation: Minimum reflux can be calculated by the Colburn method, Fenske’s can be used for Minimum Trays.

4. Colburn method is based on the
a) Constant Molar Overflow and relative volatility
c) Reflux ratio
d) Maximum Trays

Explanation: The Colburn method is an elaborate method based on assumption that Constant Molar Overflow and relative volatility.

5. A non-key component may be distributed, if it has volatility
a) Very far to one from other keys
b) Same as that of non-key
c) Very close to that of one keys
d) Constant Molar Overflow

Explanation: Volatility that very close to that of one keys is not disturbed, as constant molar overflow resides for the column feed assumptions.

6. If the flow rates of liquid and distillate are 150 kmol/h and 100 kmol/h. Find reflux ratio?
a) 90
b) 50
c) 15
d) 30

Explanation: Reflux is given by L/D = 150/100 = 15.

7. If S=8.137 and α =1.956. Then No. of stages are?
a) 13
b) 14
c) 12
d) 16

Explanation: As N=S/ln α = 8.137/ln 1.956 = 12.

8. The ROSE Method involves the plot of
a) 1/R vs 1/N
b) 1/S vs 1/N
c) 1/S vs 1/R
d) 1/T vs 1/P

Explanation: Rose curve is not a straight line given by 1/R vs 1/N, while 1/S vs 1/N is defined as the inverse Rose curve method.

9. The Ratio of optimum feed stages to total number of stages is
a) Dependent on number of stages
b) Independent of number of stages
c) Independent of total stage
d) Inversely proportional.

Explanation: This is mathematically explained as Fenske’s equation, which also involves relative volatility of the components.

10. The K value of Methane at 205oF is?
a) 15
b) 28
c) 16
d) 1.65