Question

If reflux in a distillation column is 100 mol/hr and the overhead product rate is 50 mol/hr, the reflux ratio is

• A. 0.5
• B. 2
• C. 50
• D. 150

Hint:

The reflux ratio \( R = \frac{L}{D} \) in a distillation column affects separation efficiency; higher ratios improve separation but increase energy costs.

Answer 1

The Correct Option is B

Step 1: Define the reflux ratio in a distillation column.
In a distillation column, the reflux ratio (\( R \)) is the ratio of the reflux flow rate (\( L \)) to the overhead product (distillate) flow rate (\( D \)): \[ R = \frac{L}{D}, \] where:
\( L \): Reflux flow rate (mol/hr), the liquid returned to the column from the condenser,
\( D \): Overhead product rate (mol/hr), the distillate withdrawn as the top product.
Step 2: Identify the given values.
Reflux flow rate (\( L \)) = 100 mol/hr,
Overhead product rate (\( D \)) = 50 mol/hr.
Step 3: Calculate the reflux ratio.
\[ R = \frac{L}{D} = \frac{100}{50} = 2. \] Step 4: Evaluate the options.
(1) 0.5: Incorrect, as \( \frac{100}{50} \neq 0.5 \). Incorrect.
(2) 2: Correct, as calculated above. Correct.
(3) 50: Incorrect, as \( \frac{100}{50} \neq 50 \). Incorrect.
(4) 150: Incorrect, as \( \frac{100}{50} \neq 150 \). Incorrect.
Step 5: Select the correct answer.
The reflux ratio is 2, matching option (2).