GATE 2026 Chemical Engineering, Q47 · Distillation
The correct answer is D, 1470.
Question
A continuous distillation column separates an equimolar mixture of diethylamine (DEA) and methanol. Saturated liquid feed enters at 30 mol/s; distillate (92 mol% DEA) is withdrawn at 10 mol/s. Using the equilibrium curve shown and a reboiler latent heat of 35 kJ/mol, with constant molal overflow, which one of the following is the minimum reboiler heat duty (in kW)?
- A. 350
- B. 700
- C. 1120
- D. 1470
Official answer: 1470
Why
GATE 2026 official key: (D). Reading the minimum-reflux pinch off the equilibrium curve and applying the reboiler energy balance under constant molal overflow gives a minimum reboiler duty of about 1470 kW.
Explanation cross-checked for consistency. Final answer matches the official IIT answer key.