1. You have just started working for Azeotrope Separations Co. and you have been placed in a project designing a distillation column to separate mystery substances A and B. Your predecessor left you the following incomplete McCabe-Thiele diagram (next page). Use this diagram to answer the following questions. You may assume that the column operates at constant pressure. a) What are xD, Xw, and xF? What are the reflux and boil-up ratios? b) Your boss wants you to operate the column with a 100 kg mol/h feed. What are the flowrates of the bottoms and distillate? c) What is q? What does the slope of the q-line tell you about the feed quality? d) Complete the McCabe-Thiele diagram by stepping off stages. What are the theoretical number of stages? Where should the feed tray go? e) You find specifications left by your predecessor that say that the feed should be at stage 6. Assuming you have the same number of stages in part d, redraw the stages to account for this new feed location. Is the desired bottoms composition still achieved? f) You begin to suspect that your predecessor did not pay attention in CBE 371. You find a handwritten note that says "Increasing the reflux ratio (i) decreases the number of trays and (ii) increases distillate flow rate." Is this statement true? If so, which part(s)? Justify your answer. g) You find a draft of a McCabe-Thiele diagram where your predecessor was counting the number of stages when the reflux ratio was at Rmin. What will be the number of stages if the column is at Rmin? Explain your reasoning. (Are your suspicions about your predecessor confirmed?)

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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1. You have just started working for Azeotrope Separations Co. and you have been placed in a
project designing a distillation column to separate mystery substances A and B. Your predecessor
left you the following incomplete McCabe-Thiele diagram (next page). Use this diagram to
answer the following questions. You may assume that the column operates at constant pressure.
a) What are XD, XW, and xp? What are the reflux and boil-up ratios?
b) Your boss wants you to operate the column with a 100 kg mol/h feed. What are the flowrates
of the bottoms and distillate?
c) What is q? What does the slope of the q-line tell you about the feed quality?
d) Complete the McCabe-Thiele diagram by stepping off stages. What are the theoretical
number of stages? Where should the feed tray go?
e) You find specifications left by your predecessor that say that the feed should be at stage 6.
Assuming you have the same number of stages in part d, redraw the stages to account for this
new feed location. Is the desired bottoms composition still achieved?
f) You begin to suspect that your predecessor did not pay attention in CBE 371. You find a
handwritten note that says "Increasing the reflux ratio (i) decreases the number of trays and
(ii) increases distillate flow rate." Is this statement true? If so, which part(s)? Justify your
answer.
g) You find a draft of a McCabe-Thiele diagram where your predecessor was counting the
number of stages when the reflux ratio was at Rmin. What will be the number of stages if the
column is at Rmin? Explain your reasoning. (Are your suspicions about your predecessor
confirmed?)

y-x Diagram for Mystery Substance A
1
0.9
0.8
0.7
0.6
> 0.5
0.4
0.3
0.2
0.1
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
X

Expert Solution

Step 1

Distillation is a technique which is used to separate more volatile compounds from less volatile compounds by the partial vaporization of feed followed by condensation.

McCabe Thiele method is the graphical solution of the material balance equations and this method is used to determine the number of trays required for separation of binary mixture.

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