What is the purpose of external reflux?

• A. Reflux from the accumulator to cool top of tower
• B. Reflux from the accumulator to heat the top of tower
• C. To vent vapors
• D. To remove liquid from the tower

Answer: (A)

External reflux is the portion of condensed liquid from the condenser that is returned to the top of the distillation column as reflux. This cooled liquid flows down the column, providing a liquid phase that facilitates condensation of rising vapors on each tray, which enhances separation and stabilizes the top temperature. In short, it increases the number of effective stages and improves product quality by cooling and circulating liquid back into the column. It’s not about heating, venting vapors, or removing liquid.