2) Batch distillation of a binary mixture methanol and water is carried out in a column with just one equilibrium stage above the still. The initial mixture in the still is characterised by, Wo= 100 kmol and xw = 0.2. The reflux ratio is initially R=3.0, and it doubles by the end of the process, during which the top product composition is kept constant at xa=0.8. For various values of R, the corresponding compositions read off from an x-y diagram are listed in the table below (operating lines for R=3.0 and R=6.0 are also shown on the xy-diagram). vapour) ym (molefraction of methanol 0.8 0.6 0.4 0.2 0 x-y diagram for methanol/water at 1 atm 0.2 0.4 Xm (molefraction of methanol in liquid) 0.6 0.8 1 R3456 R Xw 0.2 0.185 0.173 0.165 a) Calculate the total amount of distillate collected. b) Comment on the suitability of using this column, operated with constant top product composition, to perform this separation. Explain your answer. (again this one should be discussed in your group).

Introduction to Chemical Engineering Thermodynamics
8th Edition
ISBN:9781259696527
Author:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Publisher:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Chapter1: Introduction
Section: Chapter Questions
Problem 1.1P
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feedback to aid with ques - Q2a) We know the initial amount of liquid in the still and its initial and final composition. We also know the intended (constant) composition of the distillate stream. Therefore we can use total and component balances to find the amount of distillate collected. Note that the distillate collection vessel is initially empty.

ans Q2: D=5.51 kmol

 

2) Batch distillation of a binary mixture methanol and water is carried out in a column
with just one equilibrium stage above the still. The initial mixture in the still is
characterised by, Wo= 100 kmol and xw = 0.2. The reflux ratio is initially R=3.0, and it
doubles by the end of the process, during which the top product composition is kept
constant at xd=0.8. For various values of R, the corresponding compositions read off
from an x-y diagram are listed in the table below (operating lines for R=3.0 and R=6.0
are also shown on the xy-diagram).
ym (molefraction of methanol in vapour)
0.8
0.6
0.4
0.2
0
0
x-y diagram for methanol/water at 1 atm
0.2
0.6
0.4
Xm (molefraction of methanol in liquid)
0.8
R Xw
3
0.2
4
5
6
0.185
0.173
0.165
a) Calculate the total amount of distillate collected.
b) Comment on the suitability of using this column, operated with constant top
product composition, to perform this separation. Explain your answer. (again
this one should be discussed in your group).
Transcribed Image Text:2) Batch distillation of a binary mixture methanol and water is carried out in a column with just one equilibrium stage above the still. The initial mixture in the still is characterised by, Wo= 100 kmol and xw = 0.2. The reflux ratio is initially R=3.0, and it doubles by the end of the process, during which the top product composition is kept constant at xd=0.8. For various values of R, the corresponding compositions read off from an x-y diagram are listed in the table below (operating lines for R=3.0 and R=6.0 are also shown on the xy-diagram). ym (molefraction of methanol in vapour) 0.8 0.6 0.4 0.2 0 0 x-y diagram for methanol/water at 1 atm 0.2 0.6 0.4 Xm (molefraction of methanol in liquid) 0.8 R Xw 3 0.2 4 5 6 0.185 0.173 0.165 a) Calculate the total amount of distillate collected. b) Comment on the suitability of using this column, operated with constant top product composition, to perform this separation. Explain your answer. (again this one should be discussed in your group).
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