We are separating a mixture that is 10 mol% methanol, 20 mol% ethanol, 30 mol% n
ID: 702280 • Letter: W
Question
We are separating a mixture that is 10 mol% methanol, 20 mol% ethanol, 30 mol% n-propanol and 40 mol% n-butanol in a distillation column. The feed is a saturated liquid. We desire to recover 98% of the ethanol in the distillate and 97% of the n-propanol in the bottoms product. The column has a total condenser and a partial reboiler and a feed rate of 100 kmol/hour at 1 atm pressure. The external reflux ratio is 5. In the enriching (rectifying) section of the column:
the liquid flow rate > vapor flow rate
the liquid flow rate = vapor flow rate
the liquid flow rate < vapor flow rate
Explanation / Answer
Distillate product = ethanol = LK
Bottom product = propanol= HK
Methanol = LNK = distillate
butanol = HNK = bottom
Fractional recovery of ethanol in distillate FReD = 0.98
Fractional recovery of ethanol in bottom FReW = 0.02
Fractional recovery of propanol in distillate FRpD = 1-0.97
= 0.03
Fractional recovery of propanol in bottom FRpW = 0.97
Ethanol balance at distillate
DXD, E = FReD x F x zF, E
= 0.98 x 100 x 0.20
= 19.6 kmol/h
At bottom
BXB,E = FReB x F x zF, E
= 0.02 x 100 x 0.20
= 0.4 kmol/h
Similarly for propanol
At bottom
BXp,B = FRp,B x F x zF, p
= 0.97 x 100 x 0.30
= 29.1 kmol/h
At distillate
DXD,p = FRpD x F x zF, p
= 0.03 x 100 x 0.30
= 0.90 kmol/h
Methanol balance at distillate
DXD, M = F x zF, M = 100 x 0.10 = 10 kmol/h
At bottom
XB, M = 0
BXB, M = 0
Total distillate
D = 10 + 19.6 + 0.90 = 30.5 kmol/h
Reflux ratio R = L/D
L = 5 x 30.5 = 152.5 kmol/h
V = L + D = 152.5 + 30.5 = 183 kmol/h
Vapor flow rate (183)> Liquid flow rate (152.5)
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.