500675 Chemical and Equilibrium Separation Processes
Workshop Nine
Question
A simple bath still (one equilibrium stage) is used to separate acetone
from ethanol. The feed charge to the still pot is 3 kmol of a 60 mol%
acetone mixture. The final bottoms concentration of 10 mol% acetone is
desired. The pressure of the process is 1 atm. The equilibrium data for
acetone-ethanol system at 1 atm is provided in Figure 1.
Determine:
a) The final charge of material in the still pot, Wfinal.
b) The amount of distillate collected, Dtotal.
c) The average mole fraction of the distillate, xD,avg
Data:
Vapour-liquid equilibrium data of acetone-ethanol system is provided in
Figure 1 (see next page).
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Mole fratction of acetone in vapour, y
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Mole fraction of acetone in liquid, x
Figure 1. VLE data of the acetone-ethanol system at 1 atm.
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Additional Information for Workshop Nine:
W 
ln  final  =
 W0 
xD,avg =
x w,final

xw 0
dx
y−x
W0 x w0 − Wfinal x w,final
W0 − Wfinal
Dtotal = W0 − Wfinal
W 
x
1
ln  final  =
ln  
 W0  K − 1  x0 
W 
 x(1 − x0 ) 
 (1 − x0 ) 
1
ln  final  =
ln 
 + ln 

 (1 − x) 
 W0   − 1  x0 (1 − x) 
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