GATE 2024 Chemical Engineering, Q14 · Distillation
The correct answer is C, 5.
Question
A homogeneous azeotropic distillation process separates an azeotropic AB binary feed using a heavy entrainer, E, as shown in the figure. The loss of E in the two product streams is negligible so that E circulates around the process in a closed circuit. For a distillation column with fully specified feed(s), given operating pressure, a single distillate stream and a single bottoms stream, the steady-state degrees of freedom equals 2. For the process in the figure with a fully specified AB feed stream and given column operating pressures, the steady-state degrees of freedom equals
- A. 3
- B. 4
- C. 5
- D. 6
Official answer: 5
Why
GATE 2024 official key: (C). Combining the base 2 DOF per column across the two interconnected columns and accounting for the closed entrainer recycle loop (which removes one otherwise-free specification) gives a net steady-state DOF of 5.
Explanation cross-checked for consistency. Final answer matches the official IIT answer key.