1. What is External Reflux Ratio?

Definition: The External Reflux Ratio is the ratio of the liquid flowrate from the reflux drum back to the distillation column to the flowrate of distillate taken as product.

Purpose: It's a crucial parameter in distillation column design and operation, affecting both product purity and energy consumption.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( R \) — External Reflux Ratio (dimensionless)
• \( L_0 \) — External Reflux Flowrate to Distillation Column (mol/s)
• \( D \) — Distillate Flowrate from Distillation Column (mol/s)

Explanation: The reflux ratio determines how much liquid is returned to the column versus how much is taken as product.

3. Importance of Reflux Ratio

Details: Higher reflux ratios generally improve separation but increase energy costs. Optimal reflux ratio balances product purity with operating costs.

4. Using the Calculator

Tips: Enter both flowrates in moles per second. The reflux flowrate is typically greater than the distillate flowrate, resulting in ratios greater than 1.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical range for reflux ratios?
A: Common industrial values range from 1.2 to 5, depending on the separation difficulty.

Q2: How does reflux ratio affect column operation?
A: Higher ratios improve separation but require more energy (larger reboiler and condenser).

Q3: What's the difference between external and internal reflux ratios?
A: External ratio uses flows outside the column, while internal ratio uses flows inside the column.

Q4: Can the reflux ratio be less than 1?
A: Yes, but uncommon in practice as it indicates more product is taken than liquid returned.

Q5: How is this related to the minimum reflux ratio?
A: The minimum reflux ratio is the smallest value that can achieve the desired separation.