Project ForgeMass Transfer
Mass Transfer Operations
GATE 2015
Hard
A binary feed (25 mol% liquid, 75% vapor) is separated by McCabe-Thiele. xD=0.95. Distillate=50% of feed. The q-line intersects the enriching operating line at (0.35, 0.5). The slope of the stripping section operating line, rounded to 1 decimal place, is
1.4(± 0.1 accepted)
Explanation
Enriching line slope=(0.95−0.5)/(0.95−0.35)=0.75=R/(R+1) ⟹ R=3. With D=0.5F, F=2D: L=3D, V=4D. L'=L+qF=3D+0.25(2D)=3.5D. V'=V−(1−q)F=4D−0.75(2D)=2.5D. Slope=L'/V'=3.5/2.5=1.4.
Source: GATE CH 2015 (2015)
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