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Mass Transfer Operations
GATE 2019
Hard
A fractionator recovers a 95 mol% n-propane distillate from an equimolar propane/butane feed. The condensate is a saturated liquid at 55°C. Antoine: ln(Psat[bar])=A−B/(T[K]+C). Propane: A=9.1058,B=1872.46,C=−25.16. Butane: A=9.0580,B=2154.90,C=−34.42. Assuming Raoult's law, the condenser pressure (bar) is (rounded off to one decimal place)
18 bar(± 0.5 accepted)
Explanation
At T=328.15K: ln(Psat,propane)=9.1058−1872.46/302.99=2.926, Psat=18.65bar. ln(Psat,butane)=9.058−2154.90/293.73=1.722, Psat=5.59bar. Bubble pressure P=0.95×18.65+0.05×5.59=18.0 bar.
Source: GATE CH 2019 (2019)
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