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Mass Transfer
Mass Transfer Operations
GATE 2011
Hard

A binary equimolar feed (S,T) is distilled to give a distillate with 96mol% S. The q-line intersects the equilibrium line at x'=0.46, y'=0.66. Assume McCabe-Thiele applies with constant relative volatility. The MINIMUM reflux ratio is

  • A1.6
  • 1.5
  • C0.66
  • D0.6

Explanation

The minimum-reflux operating line runs from (xD,xD) to (x',y'): slope=Rmin/(Rmin+1)=(xD−y')/(xD−x')=(0.96−0.66)/(0.96−0.46)=0.30/0.50=0.6. Solving: Rmin=0.6(Rmin+1) ⟹ 0.4Rmin=0.6 ⟹ Rmin=1.5.

Source: GATE CH 2011 (2011)

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