Distillation Column
By Jesse Reeves
Outline
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Where we are, where we want to be.
How to get there.
What we used and what we got.
The trouble.
The model.
What we have
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12 tray bubble-cap distillation column
Isoproply alcohol water separation
What we want
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Same distillation column
Ethanol water separation
How to get there
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Operate column at total reflux
Determine stage efficiency
Model the column in Aspen
Compare Aspen model to real IPA separation
results
Apply the Aspen model to an Ethanol
separation
Theory to get there
Equilibrium curve
 1, 2 x1
y1 
1  x1 ( 1, 2  1)
Rectifying operating line
Ln
D
y n1 
xn 
xD
Vn1
Vn1
Stripping operating line
y m 1
L
B
 x m  xb
V
V
Murphree-vapor efficiency
E mv 
y i , n 1  y i , n
y i , n 1  y i*, n
Theory in a graph
Generic Equilibrium Curve
mole fraction of the light key
component in vapor
1
0.8
0.6
0.4
0.2
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
mole fraction of the light component in liqu
0.9
1
Total
Condenser
The Column
Stage
2
Stage
3
Distillation
Collumn
Stage
4
Stage
5
Stage
6
Stage
7
Stage
8
Stage
9
Stage
10
Stage
11
Stage
12
Reboiler
Feed
Tank
Pump
The Data
Calibration
Stage
State
2
Liquid
3
Method
Mass%IPA
Error
y* Mass% Ave
Error
Emv eq
Error
Pycnometer
83.2014
2.7145
85.0
2.5
Liquid
Pycnometer
81.4879
2.9938
84.0
2.5
68.2106
192.6003
4
Liquid
Pycnometer
78.4166
2.6494
83.0
2.5
67.0089
102.1962
5
Liquid
Pycnometer
81.6113
2.7021
84.0
2.5
-133.7437
-259.9631
6
Liquid
Pycnometer
77.0589
2.5954
82.0
2.5
92.1339
101.3146
7
Liquid
Pycnometer
54.8630
2.1294
79.0
2.5
91.9579
18.7079
8
Liquid
Pycnometer
53.5125
2.1461
79.0
2.5
5.2986
11.8814
9
Liquid
Pycnometer
23.9760
1.6605
75.0
2.5
57.8874
6.3146
10
Liquid
RI
4.8889
0.5748
55.0
2.5
38.0896
4.0122
11
Liquid
RI
1.7778
0.5691
35.0
2.5
9.3645
2.5398
12
Liquid
RI
5.5556
0.5752
60.0
2.5
-6.9388
-1.5218
The Trouble
120
S
2
2
2
2
2
100
S
2
2
2
2
2
2
S
2
2
2
2
2
80
60
S
2
2
2
2
2
40
20
0
16:19:12
16:33:36
16:48:00
17:02:24
17:16:48
17:31:12
17:45:36
S
2
2
2
2
2
2
S
2
2
2
The IPA separation
1
Y-x for WATER/ETHAN-01
0.2
Vapor Massfrac ETHAN-01
0.4
0.6
0.8
12.696 psi
0
0.2
0.4
0.6
Liquid Massfrac ETHAN-01
0.8
1
The ETOH separation
1
Y-x for WATER/ETHAN-01
0.2
Vapor Massfrac ETHAN-01
0.4
0.6
0.8
12.696 psi
0
0.2
0.4
0.6
Liquid Massfrac ETHAN-01
0.8
1
The model
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The IPA Aspen model
-4.7% at the top
+8.4% at the bottom
The three important stages 7, 9, and 10 Murphreevapor efficiencies were 91.9+18.7%, 57.9+6.3%,
38.4+4.0%
Overall column efficiency 8.3%
Stage efficiency did not matter
The Aspen model for ETOH
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Max flow rate: 2.13 GPM
Steam flow rate: 1.67 kg/min
Condenser heat duty: -1739 kJ/min
Feed composition: 2.5 wt% ETOH
Distillate composition: 40 wt% ETOH
ETOH recovery: 99.4%
Recomendations
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Replace the automatic control valve for the
steam flow to the reboiler.
Replace the leaky manual steam valve.
Refine the ETOH model with steady state
data.
Special thanks to team-J
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Jaron Stanley: Team Leader
James Gardner: Operator
Jesse Reeves: Team player
References
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Seader, J. D., Henley, Ernest J., Separation
Process Principles, John Wiley & Sons, Inc.
pp. 44, 301, 358-397 (1998).
Distillation Column Manual, unpublished
printed notes, Univ. of Utah, Salt Lake City,
Utah 1997.
Questions
?