1 EFCE Working Party on Fluid Separations, Bergen, 23-24 May 2012 New results for divided-wall columns Deeptanshu Dwivedi (PhD Candidate, NTNU) Ivar Halvorsen (Senior Scientist, SINTEF) Sigurd Skogestad * (Professor, Department of Chemical Engineering, NTNU, Trondheim)
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1 EFCE Working Party on Fluid Separations, Bergen, 23-24 May 2012 New results for divided-wall columns Deeptanshu Dwivedi (PhD Candidate, NTNU) Ivar Halvorsen.
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1
EFCE Working Party on Fluid Separations, Bergen, 23-24 May 2012
New results for divided-wall columns
Deeptanshu Dwivedi (PhD Candidate, NTNU)Ivar Halvorsen (Senior Scientist, SINTEF)Sigurd Skogestad * (Professor, Department of Chemical
Engineering, NTNU, Trondheim)
2
Trondheim
Oslo
UK
NORWAY
DENMARK
GERMANY
North Sea
SWEDEN
Arctic circle
3
EFCE Working Party on Fluid Separations, Bergen, 23-24 May 2012
• Introduction: Divided wall columns for 3- and 4-product separations• Structures
4-product extended Kaibel column up to ~30 % energy savings
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EFCE Working Party on Fluid Separations, Bergen, 23-24 May 2012
Vmin diagram for four components
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EFCE Working Party on Fluid Separations, Bergen, 23-24 May 2012
Experimental Set up
• 4 products• Packed Column • Magnetic funnel-liquid
split & Product valves• Number of theoretical
stages (experimentally determined): – Prefractionator: 13– Main column : 21
Feed
ABCD
A
(Methanol)
B
(Ethanol)
C
(Propanol)
D
(Butanol)
8m
13
EFCE Working Party on Fluid Separations, Bergen, 23-24 May 2012
Experimental Set up (Labview Interface)…
14
EFCE Working Party on Fluid Separations, Bergen, 23-24 May 2012
Control Structure (As used in experiments)
• Boilup V=constant• 4 control degrees of freedom:
• Liquid split ratio RL1, • Reflux ratio RL2 (top) • Reflux ratio RL3 (middle)• Reflux ratio RL4 (bottom)
• Decentralized Control with 4 PI Temperature Controllers:
•T2s is adjusted to get large temperature change in the prefractionator•T3s, T5s, T7s is adjusted to get the temperature of product stages close to the boiling points of their main components
14
5
6
7
3
F
D
S1
S2
B
T5
T3
T7
TC
Rl2
Rl1
Rl3
Rl4
TC T3S
TC T5S
TC T7S
T2
2
T2S
V
15
EFCE Working Party on Fluid Separations, Bergen, 23-24 May 2012
Start-up
40 60 80 100 120 14080
85
90
T [
0 C]
T2 (measured)
T2 (setpoint)
40 60 80 100 120 1400.25
0.3
0.35
0.4
0.45
Out
put
Loop 1 controller output
40 60 80 100 120 14068
68.5
69
69.5
T [
0 C]
T3 (measured)
T3 (setpoint)
40 60 80 100 120 1400.8
1
1.2
1.4
1.6
Out
put
Loop 2 controller output
40 60 80 100 120 14080
85
90
T [0
C]
T5 (measured)
T5 (setpoint)
40 60 80 100 120 1400.7
0.8
0.9
1
Out
put
Loop 3 controller output
40 60 80 100 120 140100
105
110
115
time, min
T [0
C]
T7 (measured)
T7 (setpoint)
40 60 80 100 120 1400
0.5
1
Out
put
time, min
Loop 4 controller output
•T2s is adjusted to get large temperature change in the prefractionator
•T3s, T5s, T7s is adjusted to get the temperature of product stages close to the boiling points of their main components
Temperatures Reflux ratios
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EFCE Working Party on Fluid Separations, Bergen, 23-24 May 2012
Steady Profiles with 4 temperature loops
0 50 10080
81T
, C
0 50 100
0.4
0.45
0 50 10068
69
70
T,
C
0 50 1000.85
0.90.95
0 50 10086
87
88
T,
C
0 50 1000.8
0.9
1
0 50 100
110
111
time, min
T,
C
0 50 100
0.70.8
time, min
R/l Loop
D/l Loop
S1 Loop
S2 Loop
Output
TEMPERATURES Reflux ratios
14
5
6
7
3
F
D
S1
S2
B
T5
T3
T7
TC
Rl2
Rl1
Rl3
Rl4
TC T3S
TC T5S
TC T7S
T2
2
T2S
V
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EFCE Working Party on Fluid Separations, Bergen, 23-24 May 2012
Liquid Split Loop -2 C
Steady Profiles with 4 temperature loops..
0 10 20 30 4080
85T
,C
0 10 20 30 40
0.350.4
0.45
0 10 20 30 4068.5
69
69.5
T,C
0 10 20 30 400.9
0.95
1
0 10 20 30 4086
87
88
T,C
0 10 20 30 40
0.70.80.9
0 10 20 30 40111
112
113
time, min
T,C
0 10 20 30 400
0.5
1
time, min
R/l Loop
D/l Loop
S1 Loop
S2 Loop
Output
TEMPERATURES Reflux ratios
14
5
6
7
3
F
D
S1
S2
B
T5
T3
T7
TC
Rl2
Rl1
Rl3
Rl4
TC T3S
TC T5S
TC T7S
T2
2
T2S
V
19
EFCE Working Party on Fluid Separations, Bergen, 23-24 May 2012
Distillate Loop ±1 C
Steady Profiles with 4 temperature loops..
0 10 20 30 4081
82
83T
,C
0 10 20 30 40
0.350.4
0.45
0 10 20 30 4068
70
72
T,C
0 10 20 30 40
0.70.80.9
0 10 20 30 4086
87
88
T,C
0 10 20 30 40
0.70.80.9
0 10 20 30 40111
112
113
time, min
T,C
0 10 20 30 400
0.5
1
time, min
R/l Loop
D/l Loop
S1 Loop
S2 Loop
Output
TEMPERATURES Reflux ratios
14
5
6
7
3
F
D
S1
S2
B
T5
T3
T7
TC
Rl2
Rl1
Rl3
Rl4
TC T3S
TC T5S
TC T7S
T2
2
T2S
V
20
EFCE Working Party on Fluid Separations, Bergen, 23-24 May 2012
0 10 20 3081.5
82
82.5T
,C
0 10 20 300.36
0.38
0.4
0 10 20 3068.5
69
69.5
T ,
C
0 10 20 300.9
0.95
1
0 10 20 3086
88
90
T ,
C
0 10 20 30
0.70.80.9
0 10 20 30111.5
112
112.5
time, min
T,C
0 10 20 300.5
0.6
0.7
time, min
R/l Loop
D/l Loop
S1 Loop
S2 Loop
Output
S1 Loop ± 1 C
Steady Profiles with 4 temperature loops..
TEMPERATURES Reflux ratios
14
5
6
7
3
F
D
S1
S2
B
T5
T3
T7
TC
Rl2
Rl1
Rl3
Rl4
TC T3S
TC T5S
TC T7S
T2
2
T2S
V
21
EFCE Working Party on Fluid Separations, Bergen, 23-24 May 2012
Steady Profiles with 4 temperature loops..
S2 Loop ± 1 C
0 10 20 3081.5
82
82.5T
,C
0 10 20 300.38
0.4
0.42
0 10 20 3068.5
69
69.5
T ,
C
0 10 20 300.9
0.95
1
0 10 20 3086.5
87
87.5
T ,
C
0 10 20 300.8
0.9
1
0 10 20 30111
112
113
time, min
T ,
C
0 10 20 300
0.5
1
time, min
R/l Loop
D/l Loop
S1 Loop
S2 Loop
Output
TEMPERATURES Reflux ratios
14
5
6
7
3
F
D
S1
S2
B
T5
T3
T7
TC
Rl2
Rl1
Rl3
Rl4
TC T3S
TC T5S
TC T7S
T2
2
T2S
V
22
EFCE Working Party on Fluid Separations, Bergen, 23-24 May 2012
Steady Profiles with 4 temperature loops..
0 10 20 30 4080
82
84T
,C
0 10 20 30 40
0.350.4
0.45
0 10 20 30 4068
70
72
T ,
C
0 10 20 30 400.60.8
1
0 10 20 30 4086
88
90
T ,
C
0 10 20 30 40
0.70.80.9
0 10 20 30 40110
112
114
time, min
T ,
C
0 10 20 30 400
0.5
1
time, min
R/l Loop
D/l Loop
S1 Loop
S2 Loop
Output
All Loops ± 1 C
TEMPERATURES Reflux ratios
14
5
6
7
3
F
D
S1
S2
B
T5
T3
T7
TC
Rl2
Rl1
Rl3
Rl4
TC T3S
TC T5S
TC T7S
T2
2
T2S
V
23
EFCE Working Party on Fluid Separations, Bergen, 23-24 May 2012