Microsoft PowerPoint - 0-lecture 28 EngrD 2190 2021.ppt - Compatibility ModeContext: Operating Lines for Distillation, cont’d. The McCabe-Thiele Method.
Defining Question: What is the range of valid liquid+vapor mixtures for a distillation feed stage?
Read pp. 289-301, Pure Component Phase Diagrams
EngrD 2190 – Lecture 28
Calculation Session this week TA Panel on Pre-enrollment for Spring 2022
Bring questions for the TAs.
Liber de arte Distillandi, by Hieronymus Brunschwig, 1527.
heater
Adjacent x-y pairs are on an operating line.
benzene toluene
Distillate – mostly benzene
Bottoms – mostly toluene
x-y pairs leaving an equilibrium stage are on the equilibrium line.
x-y pair on operating line and on xy line (the diagonal).
stripping section L > V operating line slope L/V > 1
rectifying section
96 mol% benzene; xB 0.96
96 mol% toluene; xB 0.04
Vapor-Liquid Diagram for Benzene+Toluene Mixtures at 1 atm
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
x benzene
y benzene
pure benzene
pure toluene
equilibrium line
L/V > 1
L/V < 1
feed stage: steps switch from stripping line to rectifying line
plotting pair at bottom of column
plotting pair at top
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 x ACN
x-y pair on operating line and on xy line: x y 0.98
50.0 30.0
10.0 10.0
5 3
run riseslope
pure ACN
pure MP
equilibrium line
xy line
x-y pair on operating line and on xy line: x y 0.02
30.0 50.0
10.0 10.0
3 5
run riseslope
1
2
3
4
yACN
reboiler
condenser
20°C 100. mol/min
rectifying section: L/V = 3/5
stripping section: L/V = 5/3
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 x ACN
pure ACN
pure MP
equilibrium line
70
80
90
100
110
120
130
140
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
te m
pe ra
tu re
liquid+vapor everywhere liquid+vapor in one region only Equilibrium everywhereEquilibrium on one line only
Need two streams to plot a point One stream defines a point Use tie linesUse operating lines
feed tie line
feed is liquid+vapor in this range
99°C
20°C 100. mol/min
rectifying section: L/V = 3/5
stripping section: L/V = 5/3
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 x ACN
x-y pair on operating line and on xy line: x y 0.98
50.0 30.0
10.0 10.0
5 3
run riseslope
pure ACN
pure MP
equilibrium line
xy line
x-y pair on operating line and on xy line: x y 0.02
30.0 50.0
10.0 10.0
3 5
run riseslope
1
2
3
4
L 60
V 100
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 x ACN
pure ACN
pure MP
equilibrium line
99°C
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 x ACN
equilibrium line
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 x ACN
pure ACN
pure MP
equilibrium line
99°C
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 x ACN
equilibrium line
vapor
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 x ACN
Adjacent x-y pairs are on an operating line.
x-y pairs leaving an equilibrium stage are on the equilibrium line.
yACN 0.50 xACN 0.22
equilibrium line pure ACN
1
2
yACN
heater
x-y pair on operating line and on xy line
stripping section: L > V
rectifying section: L < V
0 0.5 1 0
0.5
1
A
xA
yA
Decide if the operating lines and the steps are consistent with a distillation column with one feed stage and finite output from both the top and the bottom.
Valid
Exercise 4.60 Solution is posted.
Decide if the operating lines and the steps are consistent with a distillation column with one feed stage and finite output from both the top and the bottom.
1
0.5
0
yA
x-y pair on operating line and on xy line
stripping section: L > V
rectifying section: L < V
operating line slope L/V < 1
Exercise 4.60 Solution is posted.
Decide if the operating lines and the steps are consistent with a distillation column with one feed stage and finite output from both the top and the bottom.
1
0.5
0
yA
Azeotrope!
Not valid
x-y pair on operating line and on xy line
stripping section: L > V
rectifying section: L < V
operating line slope L/V < 1
Exercise 4.60 Solution is posted.
Decide if the operating lines and the steps are consistent with a distillation column with one feed stage and finite output from both the top and the bottom.
D
x-y pair on operating line and on xy line
stripping section: L > V
rectifying section: L < V
operating line slope L/V < 1
Exercise 4.60 Solution is posted.
Decide if the operating lines and the steps are consistent with a distillation column with one feed stage and finite output from both the top and the bottom.
E
x-y pair on operating line and on xy line
stripping section: L > V
rectifying section: L < V
operating line slope L/V < 1
Exercise 4.60 Solution is posted.
Decide if the operating lines and the steps are consistent with a distillation column with one feed stage and finite output from both the top and the bottom.
F
x-y pair on operating line and on xy line
stripping section: L > V
rectifying section: L < V
operating line slope L/V < 1
Exercise 4.60 Solution is posted.
Decide if the operating lines and the steps are consistent with a distillation column with one feed stage and finite output from both the top and the bottom.
G
1
0.5
0
yA
x-y pair on operating line and on xy line
stripping section: L > V
rectifying section: L < V
operating line slope L/V < 1
Exercise 4.60 Solution is posted.
Decide if the operating lines and the steps are consistent with a distillation column with one feed stage and finite output from both the top and the bottom.
H
1
0.5
0
yA
x-y pair on operating line and on xy line
stripping section: L > V
rectifying section: L < V