Title: Dividingwall column review and Design comparisons
1Dividing-wall column reviewandDesign comparisons
2Outline
- Introduction of DWC
- background
- Remixing effect and Petlyuk column
- Whether to use DWC or not
- Industry review
- Academic groups
- Design methods
- Design comparisons
3Background
Introduction of DWC /
- DWC (Dividing-Wall column) is 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.
4Remixing effect
Introduction of DWC / Remixing effect and Petlyuk
column/
- Remixing effect leads to a thermal inefficiency
Composition profile of the middle component In
the columns of the direct sequence.
Schultz, M. A., D. G. Stewart, et al. (2002).
"Reduce costs with dividing-wall columns."
Chemical Engineering Progress 98(5) 64-71.
5Petlyuk column
Introduction of DWC / Remixing effect and Petlyuk
column/
- Eliminate the remixing effect
6DWC
Introduction of DWC / Remixing effect and Petlyuk
column/
Adiabatic wall
Thermodynamically equivalent
Side-draw section
prefractionator
Dividing-Wall Column, DWC
Petlyuk column 1965
7Introduction of DWC / Remixing effect and Petlyuk
column / DWC
Component B mole fraction
8Whether to use DWC or not
Introduction of DWC /
- DWC might be suitable
- High product purity
- When high-purity middle product is desired, DWC
should be considered. - Middle product in excess
- DWC is most advantageous with the feed
composition - 60-70 B and A ?C
- Uniform relative volatility
- When B is a significant portion of the feed, DWC
can be more - advantageous as long as the split between A/B is
as difficult as B/C.
A typical rule of thumb
Schultz, M. A., D. G. Stewart, et al. (2002).
"Reduce costs with dividing-wall columns."
Chemical Engineering Progress 98(5) 64-71.
9Introduction of DWC / Whether to use DWC or not
- DWC might not be suitable
- High pressure difference
- There is a high pressure difference between the
columns in the - conventional tow-column sequence
- Utilities at different T
- The conventional sequence requires utilities at
different temperatures for - Each column (refrigeration and cooling water)
As with any guidelines, there are exceptions, but
these can be useful during the screening process.
10Industry review
Introduction of DWC /
- Germany
- BASF
- In 1985, BASF constructed the first commercial
DWC. BASF is also believed to be the leader in
the total number of such columns in existence.
(28 DWCs) - Uhde GmbH
- Linde AD
- Linde AG have built the tallest DWC (100m 5.2m
diameter) for Sasol. - British
- Kellogg
- Kellogg has designed a DWCs for BP, which
increases 50 purity of middle component. - U.S.
- UOP LLC
- Japan
DWCs are being used to separate a range of
products, including various hydrocarbon streams,
esters, alcohols, aldehydes, ketones and amines.
11Academic groups
Introduction of DWC /
- R. Smith (UMIST,UK)
- Triantafyllou, C. and R. Smith (1992)
- Lestak F., Smith R and Dhole VR. (1994)
- Abdul Mutalib, M. I. and R. Smith (1998)
- Amminudin, K.A. and R. Smith (2001)
- They proposed a design model to confirm potential
energy savings comparing with the conventional
arrangement, and set up pilot-scale columns to
study controllability and operability.
12Introduction of DWC / Academic groups
- S. Skogestad (Norwegian Univ Sci Technol,
Norway) - Wolff, E.A. and S. Skogestad (1995)
- Ivar J. Halvorsen and S. Skogestad
(1999,2003,2004) - They have done the extended researches about
Petlyuk arrangement, and have done a series
researches about steady state behavior, dynamic
behavior, and control strategy. - Prof. Y. H. Kim (Dong-A University, Korea)
- He has proposed some rigorous design of fully
thermally coupled distillation column
13Design methods
Introduction of DWC /
- Proprietary software
- Aspen Plus HYSYS
- R. Smith
- Short-cut method (Fenske-Underwood-Gilliland)
1992 - Use Fenske equation to find the minimum number of
trays Nmin at the total reflux conditions. - Use Underwoods equations to find the minimum
reflux ratio Rmin. - Use the values in the Gilliland correlation and
estimate the required number of theoretical trays
for an given operating reflux ratio Rmin.
14Introduction of DWC / Design methods / R. Smith
- Equilibrium stage composition
- concept 2001
Amminudin, K. A., R. Smith, et al. (2001).
"Design and optimization of fully thermally
coupled distillation columns part 1 Preliminary
design and optimization methodology." Chemical
Engineering Research Design 79(A7) 701-715.
15Introduction of DWC / Design methods /
- Prof. Y. H. Kim
- The design is based on the minimum tray structure
to give high thermodynamic efficiency by making
liquid composition profile similar to the residue
curves of equilibrium distillation. - Sotudeh
- Improved short-cut method 2007
- The method is based on Underwood equation only.
- Determine the minimum vapor flow Vmin and minimum
reflux ratio Rmin. - Choose an operating reflux ratio in the range of
1.2-1.5 Rmin. - Calculate the total number of trays in the tower
and the side stream location.
16Design comparisons
SR side-rectifier SS side-stripper FC fully
thermally coupled DSLV direct split
(modified) ISLV indirect split (modified)
Agrawal, R. and Z. T. Fidkowski (1998). "Are
thermally coupled distillation columns always
thermodynamically more efficient for ternary
distillations?" Industrial Engineering
Chemistry Research 37(8) 3444-3454.
17Efficiency
Design comparisons /
- Efficiency
- aA relative volatility of A with respect to C
- aB relative volatility of B with respect to C
- aAB relative volatility of A with respect to B
- ESI (ease of separation index)
18Equimolar mixture
Design comparisons /
The most efficient configuration to distill an
equimolar mixture as a fuction of aA and aB
ZAZBZC
For aA and aB lt 11
DSLV
ISLV
19A-rich, B-rich and C-rich feed
Design comparisons /
C-rich feed 0.05 0.05 0.9
B-rich feed 0.05 0.9 0.05
A-rich feed 0.9 0.05 0.05
DSLV is almost the most efficient
20ESI 1
Design comparisons /
aAB is kept equal to aBC
1.21/ 1.10/ 1
4 / 2/ 1
25/ 5/ 1
Separation is relatively difficult
Separation is relatively easy
DS zone ? ISLV zone ? FC zone ?
DSLV is almost the most efficient
FC is most efficient close to equimolar feed
SS SR small ZB DSLV small ZC ISLV small ZA
FC prefers lower ZB !?
21ESI gt 1
Design comparisons /
ESI 1.36 1.65/ 1.10/ 1
ESI 1.5 6/ 2/ 1
ESI 1 4/ 2/ 1
As ESI ? DSLV zone ? SR zone ?
When ESI gt 1.5 ,SR is almost always the most
efficient in C-rich feed
22ESI lt 1
Design comparisons /
ESI 0.51 2.05/ 2.0/ 1
ESI 0.65 2.6/ 2.1/ 1
ESI 1 4/ 2/ 1
As ESI decreases, the SR zone become
disappeared ISLV and SS zone occupy the most
space For A-rich feed, DSLV and SS are most
efficient For C-rich feed, ISLV and SS are most
efficient For highly B-rich feed (ZB gt 0.9), DSLV
is most efficient
23The 2nd most efficient configuration
Design comparisons /
ESI 1 4/ 2/ 1
ESI 1 4/ 2/ 1
As expected, the 2nd most efficient
configurations are those obtained by
interchanging the most efficient configurations
across the boundary in the figure above.
When ESI ?1 and two most efficient configurations
are considered, the FC has larger composition
space (not valid when ESI is much different from
1)
The second most efficient configuration at each
composition
24Reference
- Schultz, M. A., D. G. Stewart, et al. (2002).
"Reduce costs with dividing-wall columns."
Chemical Engineering Progress 98(5) 64-71. - Amminudin, K. A., R. Smith, et al. (2001).
"Design and optimization of fully thermally
coupled distillation columns part 1 Preliminary
design and optimization methodology." Chemical
Engineering Research Design 79(A7) 701-715. - Sotudeh, N. and B. H. Shahraki (2007). "A method
for the design of divided wall columns." Chemical
Engineering Technology 30(9) 1284-1291. - Agrawal, R. and Z. T. Fidkowski (1998). "Are
thermally coupled distillation columns always
thermodynamically more efficient for ternary
distillations?" Industrial Engineering
Chemistry Research 37(8) 3444-3454.