In distillation, what is the process of condensing vapor and returning the condensate to the original system called?

• A. Boilup
• B. Reflux
• C. Distillate
• D. Feed

Answer: (B)

Reflux is the process of condensing vapor and returning the condensate to the original system. In a distillation column, the vapor rising from the reboiler condenses in the condenser, and part of that condensate is fed back down the column. This internal recycle creates liquid that flows countercurrently to the rising vapor, improving contact and separation between components. The amount returned relative to what’s withdrawn as product is the reflux ratio, which controls how sharp the separation becomes. Boilup is the vapor generated in the reboiler, distillate is the top product taken off, and feed is the material introduced to the column.