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Mass Transfer
Mass Transfer Operations
GATE 2020
Hard

Equilibrium data for methanol-water at 1 bar passes through the point (x=0.5, y=0.78). A distillation column at 1.0 bar must produce 92 mol% methanol distillate from an equimolar saturated-liquid feed. The minimum reflux ratio is

  • A0.33
  • 0.50
  • C0.54
  • D1.17

Explanation

Saturated liquid feed (q=1) gives a vertical q-line at x=zF=0.5, intersecting the equilibrium curve at (0.5, 0.78). Rmin/(Rmin+1)=(xD−yq)/(xD−xq)=(0.92−0.78)/(0.92−0.5)=0.14/0.42=0.333. Rmin=0.333/0.667=0.50.

Source: GATE CH 2020 (2020)

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