operation of energy-efficient divided wall (petlyuk) column
DESCRIPTION
Operation of Energy-Efficient Divided Wall (Petlyuk) Column. Speaker : Ambari Khanam Course : Specialization Project-tkp4550 Department of Chemical Engineering Date : December 17 th , 2012 Project-Supervisor : Sigurd Skogestad. Outline. Introduction to Divided Wall Column (DWC) - PowerPoint PPT PresentationTRANSCRIPT
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Operation of Energy-Efficient Operation of Energy-Efficient Divided Wall (Petlyuk) ColumnDivided Wall (Petlyuk) Column
Speaker : Ambari Khanam
Course : Specialization Project-tkp4550
Department of Chemical Engineering
Date : December 17th, 2012
Project-Supervisor : Sigurd Skogestad
2
Introduction to Divided Wall Column (DWC)− Background and description
The project work is related to most likely situations in industrial practice.
- The column is designed for optimal operation
- Optimal Energy/close to Vmin for the given product specifications
- Actual avialable energy less (therefore non-optimal RV)
- Effect on product purities in all three streams
- Minimize the impurities (the objective function)
Conclusion and further work
3
• DWC (Dividing-Wall column) was introduced by Wright in 1949.
• However, lack of reliable design method and concerns about the operation and control of DWC have prevented the widespread application.
• People started to pay much attention to DWC after the Energy Crisis (1980).
• In 1985, BASF built the first commercial DWC.
• There are now more than 100 columns installed worldwide.
• Energy consumption in distillation and greenhouse gas emissions are strongly related
• Three products Petlyuk Arrangement can save upto 20-30% energy and 30% capital cost.
4
(a) Implementation with three separate columns (b) DWC implementation with a side-productFigure. Thermodynamically equivalent implementations of three-product Petlyuk column
5
Side-drawsectionprefractionator
6
2
( )F v D S B
F D S B v
v
J p F p V p D p S p B
p F p D p S p B p V
k p V
( )D S S BB A C BJ x D x x S x B
Fixed specifications
7
0 5 10 15 20 25 30 35 400
0.2
0.4
0.6
0.8
Number of stages
Com
posi
tions
Prefractionator Composition Profile
0 10 20 30 40 50 60 70 800
0.2
0.4
0.6
0.8
1
Number of stages
Com
posi
tions
Main Column Composition profile
ABC
ABC
8
List of Tasks
9
0 10 20 30 40 50 60 70 80 900
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
X: 41Y: 0.8234
No. of stages
Mol
e fr
actio
n of
com
pone
nts
Composition profiles of A, B and C at 80% Enegry
X: 1Y: 0.9763
X: 82Y: 0.9985mole fraction of A in top distillate
mole fraction of B in side stream
mole fraction of C in Bottomproduct
0 10 20 30 40 50 60 70 80 900
0.2
0.4
0.6
0.8
1X: 1Y: 0.9964
X: 41Y: 0.9903
No. of stages
mol
efra
ctio
n of
com
pone
nts
Compositions profiles of A, B and C at 100% Energy
X: 82Y: 0.9992
mole fraction of A in top distillatemole fraction of B in side stream mole fraction of C in bottom
product
The Composition Profiles for Given energy with Variable RV,RL,L and S
10
,% of V0
LE-01
RLE-01
RVE-01
SE-01
XBD
E-03
XAS
E-03
XCS
E-03
XBB
E-03-J
E-03100% 9.985 3.107 5.704 3.351 3.56 2.40 7.32 0.81 4.7198% 9.716 3.173 5.807 3.359 4.54 2.62 11.62 1.86 6.9296% 9.452 3.078 5.835 3.404 4.25 3.13 23.94 1.99 11.2895% 9.320 3.096 5.866 3.429 5.59 4.33 30.97 2.22 14.6994% 9.172 3.099 5.907 3.447 9.72 4.50 39.84 1.99 19.1892% 8.904 3.428 6.155 3.521 9.54 3.57 60.63 1.93 26.4190% 8.632 3.453 6.260 3.585 10.8 3.33 78.17 1.43 33.2885% 7.973 3.241 6.404 3.758 10.54 4.59 11.89 1.30 50.3482% 7.622 4.323 7.142 3.928 3.19 10.56 145.99 3.27 63.4780% 7.302 4.196 6.963 3.947 23.70 14.44 162.16 1.46 78.05
% of V0
LE-01
RLE-01
RVE-01
SE-01
XBD
E-03
XAS
E-03
XCS
E-03
XBB
E-03-J
E-03100% 9.985 3.107 5.705 3.351 3.56 2.40 7.32 0.81 4.71398% 9.736 3.097 5.705 3.384 3.46 7.27 12.25 1.19 8.14796% 9.479 2.944 5.705 3.437 2.20 8.66 25.18 1.67 12.90695% 9.355 2.860 5.705 3.474 0.221 9.46 32.99 1.85 15.41894% 9.237 2.900 5.705 3.494 1.37 14.80 37.09 5.04 20.20692% 9.021 3.084 5.705 3.592 3.75 30.43 52.65 8.62 33.7990% 8.810 3.148 5.705 3.752 0.41 41.16 73.60 3.40 44.23585% 8.126 2.436 5.705 3.878 1.78 36.24 110.20 5.95 59.09982% 7.833 2.714 5.705 4.107 0.79 59.44 131.44 2.83 79.42781% 7.615 1.9871 5.705 4.058 1.68 40.07 141.50 2.44 74.893
Variable RV
Fixed RV
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% of VL
E-01RL
E-01RV
E-01S
E-01
XBD
E-03
XAS
E-03
XCS
E-03
XBB
E-03-J
E-03100% 9.991 3.141 5.715 3.3589 2.04 2.758 7.24 0.373 4.16198% 9.722 3.188 5.828 3.275 2.17 2.113 7.89 24.73 12.3896% 9.454 3.333 6.068 3.124 1.28 0.668 9.33 66.67 27.1995% 9.276 3.474 6.188 3.111 14.27 0.548 9.45 58.46 28.4594% 9.126 3.394 6.062 2.954 21.18 2.94 7.06 92.21 43.8092% 8.922 3.469 6.237 0.630 0.752 2.15 7.85 44.86 271.690% 8.388 3.871 6.550 2.611 74.81 0.57 9.42 12.64 77.4585% 7.986 3.898 6.733 1.9057 3.26 3.23 6.77 30.19 146.682% 7.497 4.264 7.121 1.9638 28.42 1.92 8.07 28.59 144.581% 7.396 4.802 7.297 1.464 22.13 9.62 0.38 35.17 189.8
Variable RV and fixed side stream purity
% of VL
E-01RL
E-01RV
E-01S
E-01
XBD
E-03
XAS
E-03
XCS
E-03
XBB
E-03J
E-03100% 9.985 6.837 4.295 3.3473 5.00 3.947 6.053 0.852 5.29898% 9.711 6.739 4.127 3.303 5.00 1.752 8.248 13.801 9.60296% 9.441 6.576 3.821 3.107 5.00 0.384 9.616 67.727 28.78195% 9.309 6.573 3.857 3.142 5.00 0.726 9.274 58.549 25.36594% 9.176 6.593 3.8647 3.049 5.00 1.171 8.829 82.565 34.479
Variable RV and fixed Top and side stream purities
12 The composition profiles for given energy with fixed RV and variable RL,L and S
0 10 20 30 40 50 60 70 80 900
0.2
0.4
0.6
0.8
1X: 1Y: 0.9964
X: 41Y: 0.9903
No. of stages
mol
efra
ctio
n of
com
pone
nts
Compositions profiles of A, B and C at 100% Energy
X: 82Y: 0.9992
mole fraction of A in top distillatemole fraction of B in side stream mole fraction of C in bottom
product
0 10 20 30 40 50 60 70 80 900
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1X: 1Y: 0.9995
No. of stages
mol
e fr
actio
n of
com
pone
nts
Compositions profiles of A, B and C at 81.5% energy
X: 41Y: 0.7988
X: 82Y: 0.999
mole fraction of A in top distillate
mole fraction of B in side stream
mole fraction of C in bottomproduct
13Compositions Profiles at 80% Energy for Variable RV and Fixed RV Respectively
0 10 20 30 40 50 60 70 80 900
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
X: 41Y: 0.8234
No. of stages
Mol
e fr
actio
n of
com
pone
nts
Composition profiles of A, B and C at 80% Enegry
X: 1Y: 0.9763
X: 82Y: 0.9985mole fraction of A in top distillate
mole fraction of B in side stream
mole fraction of C in Bottomproduct
0 10 20 30 40 50 60 70 80 900
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1X: 1Y: 0.9995
No. of stages
mol
e fr
actio
n of
com
pone
nts
Compositions profiles of A, B and C at 81.5% energy
X: 41Y: 0.7988
X: 82Y: 0.999
mole fraction of A in top distillate
mole fraction of B in side stream
mole fraction of C in bottomproduct
14
0.75
0.8
0.85
0.9
0.95
1
1.05
100 98 96 95 94 92 90 87 85 84 82 81.5 81
Puri
ty o
f pr
oduc
ts s
trea
m A
, B a
nd C
(fr
acti
onal
)
% of minimum energy (V0)
XAD
XBSXCB
Variable RV Fixed RV
15
Variable RV fixed side stream purity
Variable RV fixed side stream and top purities
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• Product specifications can not be maintained at energy lower than optimal because of non-optimal RV.
• The optimal in terms of minimizing the impurities sum of all three products tends to increase the impurity in the side stream.
• The results obtained are useful when product specifications are not given and one gets paid for the purity in products.
• The other case could be that the side stream has no value and one get paid for the purity in both top product and bottom product.
• When side stream purity is fixed then bottom product tends to be least pure.
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The results can be further verified by doing the simulations for following cases:– Change in feed composition
– Change in relative volatility of components.
A simple and robust control structure can be designed for operation at lower energy when the product is valuable based upon its purity.
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19
0.84
0.88
0.92
0.96
1
100 98 96 95 90 85 80 75 70
Pur
ity
of p
rodu
cts
stre
am A
and
B (
frac
tion
al)
% of minimum energy (V0)
XAD
XBB
Products purities versus energy for fixed D/F
0 0,D BD A A B B Bp p x p p x
0 0D B
F v A A B BJ p F p V p x D p x B
Cost function for Binary Product Column
20
0.75
0.79
0.83
0.87
0.91
0.95
0.99
100 98 96 95 90 85 80 75 70
Puri
ty o
f pr
oduc
ts s
trea
m A
and
B (
frac
tion
al)
% of minimum energy (V0)
XAD
XBB
Bottom product purity versus energy for fixed top product purity
0.75
0.79
0.83
0.87
0.91
0.95
0.99
100 98 96 95 90 85 80 75 70
Puri
ty o
f pro
duct
s st
ream
A a
nd B
(fra
ctio
nal)
% of minimum energy (V0)
XAD
XBB
Top product purity versus energy for fixed bottom product purity
21
• By operating the column at lower energy than minimum energy we can no longer stick to product specifications
• When D/F is fixed then both products tend to be equally impure with decreasing energy.
• when one of the products is valuable and the other one has no value then the column can be operated at lower value of energy. and will still get one desired product at specifications.