A distillation column containing N trays operates normally before being switched to total reflux mode, halting product withdrawal, bottoms discharge, and feed injection. What occurs at the new steady state ?
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Answer: D. The top and bottom compositions correspond to the maximum enrichment available
Explanation
Total reflux halts all product withdrawal while returning every drop of condensate back up. This extreme operational mode eliminates net product flow across the column boundaries. Compositions reach maximum possible enrichment between the top and bottom products. Distillation columns use reflux to provide internal liquid overflow for vapor contacting. Total reflux represents the limiting case used in Fenske equations for minimum trays. Steady state conditions under total reflux maximize separation efficiency per tray.
Operators use total reflux during column startup to establish equilibrium profiles quickly. Testing distillation column performance often involves measuring separation under total reflux. This operational mode requires zero feed injection and zero product collection. Vapor and liquid compositions vary continuously from tray to tray inside the column. Reboiler and condenser thermal loads are actually maximized under total reflux conditions. Option C is incorrect because top and bottom compositions change significantly at total reflux.
- Subject
- Engineering
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- Chemical Engineering
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- —
- Difficulty
- medium
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