International Journal of Applied Engineering Research ISSN 0973-4562 Volume 11, Number 12 (2016) pp 7772-7775
© Research India Publications. http://www.ripublication.com
Separation of Acetone-chloroform maximum boiling azeotrope using
Dimethyl sulfoxide
Manish Pokhrel, Asante Daniel Owusu, and Jung Ho Cho*
Department of Chemical Engineering, Kongju National University 592, Shindangdong,
Cheonan, Chungnam 331-280 , South Korea.
Department of Chemical Engineering, Kongju National University, Buiding No 9, Room 1017,
Cheonan-si, Chungnam, 31080, South Korea.
Abstract
In this study, an effort has been made to design an extractive
distillation for separating maximum boiling azeotrope of
acetone-chloroform system. PRO/II 8.2 has been used to
simulate the overall process. The simulations have been
optimized through the regression of VLE data adopted from
Dortmund data bank and performance of different case studies.
Dimethyl sulfoxide (DMSO) has been used as a solvent.
Thermodynamic feasibility analysis is done through the
understanding of ternary map diagrams. Two different
thermodynamic models, NRTL and UNIQUAC were explored
for the study of overall process.
INTRODUCTION:
The distillation process is based on the difference in the
volatility of the components to be separated. However, for
mixtures where azeotropes are present, conventional
distillation have shown to be unable to affect the separation
desired (de Figueirêdo et al. 2011).
Acetone-chloroform mixture is a typical example of a system
with a pronounced negative deviation from ideal solution
behavior. This mixture presents a negative azeotrope with a
boiling point of 64.48°C and an acetone mole fraction
approximately equal to 0.3393 at 1 atm. For the mixture
having close boiling points or forming azeotrope,
conventional distillation cannot be used. Instead special types
of distillation processes should be applied. For instance in
azeotropic distillation a third component E is added to the
feed. A or B components become either a stable or unstable
node on the residue curve in the relevant distillation region,
thus being removable as product by either an indirect or a
direct split, respectively (Shen et al. 2015).
The basis of ED is the increase of relative volatility between
the close-boiling components caused by introducing a
selective solvent, which has stronger affinity with one type of
the components in the mixture (F.-M. Lee 2000). In this study,
we have controlled and optimized the distillation of acetonechloroform system using DMSO. Extractive distillation can be
more energy efficient than azeotropic separation, where a
liquid phase split is used to overcome distillation boundaries
(Lei, Li, and Chen 2003, 121-213). This is especially true
when thermally integrated sequences are used (Knapp and
Doherty 1990, 969-984). It has been reported that pressure
swing distillation is unattractive for the separation of acetonechloroform system since its composition is not sensitive to
pressure changes (Luyben 2008).
Problem Design and Specification
In extractive distillation, the added component (solvent)
modifies the relative volatility of the original components and
causes the azeotropic point to disappear. In this study, the
heavy boiling entrainers were used, thus have the highest
boiling point amongst all other components thereby coming
out from the bottom of the solvent recovery column. By
intuition ‘A well-designed system’ implies the lowest energy
consumption for the system as well as least loss of the solvent
taking into consideration the constraints imposed on the
process. The process can be called as a ‘well-designed system’
only if the functions like tray number, feed plates of binary
azeotropes and solvent, reflux ratio and the solvent flow rate
have been optimized. The operating conditions for the process
optimization have been listed in Table 1.
Table 1: Operating conditions for the process optimization
Specifications
Feed flow rate
Distillate flow rate
(kmol/hr)
Column pressure (atm)
Feed temperature
Main feed composition
XA, mole fraction
XB mole fraction
Entrainer composition
XE, mole fraction
No of columns
Controlled variables
constraint
Top product
Bottom product
Extractive
column
100
50
Regeneration
column
1.1
320
1.1
320
50
0.5
0.5
1
15-50
10-60
≥0.995 acetone ≥0.995 chloroform
≤0.001 acetone ≥0.9999 entrainer
Thermodynamic Modeling
Non-random two-liquid model (NRTL) and UNIQUAC
models have been used for the simulation process. The VLE
experimental data for acetone-chloroform (Rosanoff M.A.
1909), acetone-DMSO (Sassa et al. 1974) chloroform-DMSO
(Philippe et al. 1973) have been obtained from Dortmund data
bank and have been regressed and optimized to obtain a new
set of binary interaction parameters as shown in Tables 2 and
3. The fitting of experimental data with NRTL and Uniquac
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International Journal of Applied Engineering Research ISSN 0973-4562 Volume 11, Number 12 (2016) pp 7772-7775
© Research India Publications. http://www.ripublication.com
models have been shown in Figures 1 and 2.
The ternary map in Figure 3 is divided into two regions by
the distillation curve. From figure 3, the stream feed to the
recovery column is slightly outside the region in which
distillate D2 and bottom B2 points lie. However, due to the
curve nature of the distillation boundary the distillation is
physically possible.
Figure 4 describes the process flow diagram for the
separation of acetone-chloroform-entrainer system in which
the azeotropic mixture and the solvent are fed to the 1st
column wherein the acetone (lowest boiling point component)
goes towards the stripping section while chloroform along
with the entrainer comes towards the rectifying section.
(Langston et al. 2005) The bottom stream is then fed to the 2nd
column recover the solvent from the bottom while chloroform
comes out from the top. A small amount of make-up stream is
fed to the system to make-up the solvent loss.
Figure 3: Ternary diagram for Acetone-Chloroform-DMSO
system using NRTL method obtained from Aspen plus.
Figure 1: Fitting of experimental data in T-XY plot for
acetone-chloroform
Figure 4: Process flow diagram for the extractive distillation
of acetone-chloroform-DMSO/Benzene/ EG
Table 2: UNIQUAC binary interaction parameters for
acetone-chloroform-DMSO system
Ci
Cj
aij
bij
Acetone
chloroform
-122.8
59.071
Acetone
DMSO
84.136
-5.041
Chloroform
DMSO
-208
-299.3
Table 3: NRTL binary interaction parameters for acetonechloroform-DMSO system
Figure 2: Fitting of experimental data in XY plot for acetonechloroform system using NRTL and UNIQUAC models.
Ci
Cj
aij
bij
aji
bji
cij
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Acetone
chloroform
-8.848
2529
9.972
-3126
0.105
Acetone
DMSO
1.756
365.2
0.209
30.47
0.872
Chloroform
DMSO
0.333
42.16
0.904
-191.9
0.434
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 11, Number 12 (2016) pp 7772-7775
© Research India Publications. http://www.ripublication.com
OPTIMIZATION
Various case studies have been performed to obtain the
minimum re-boiler heat duty. Minimum reflux ratio and
minimum solvent flow rate have been determined to obtain
the minimum re-boiler heat duty. The effect of solvent flow
rate at constant reflux ratio and the combined effect of solvent
flow rate and reflux ratio on the amount of chloroform on the
distillate stream for acetone-chloroform-DMSO system have
been shown in Figures 5 and 6. NRTL and UNIQUAC
thermodynamic models have been used to study their effects
on the overall process. The results have been summarized in
the Table 4.
For all the processes, the cooling water and steam
consumption was also evaluated. The cooling water was
supplied at 32oC and withdrawn at 40oC while steam was
supplied at 145oC. The consumption of cooling water and
steam by the overall process has been illustrated in Table 6.
Table 3: Optimized variables for the overall process
Reflux
ratio
Solven Condenser Re-boiler Feed Entrai Feed
t flow heat duty heat duty tray ner tray
rate (M*kcal/hr (M*kcal/hr locati tray locati
(kmol/
)
)
on locatio on to
hr)
n
2nd
colu
mn
1st 2nd
1st 2nd 1st 2nd
colu colu
colu colu colu colu
mn mn
mn mn mn mn
0.92 0.8 77.47 0.32 0.28 0.99 0.79 12
4
6
Table 4: Stream property table for acetone-chloroformDMSO
Stream
Name
Phase
Tem
perature
Pressure
Flowrate
Com
position
ACETONE
CHCL3
DMSO
ACETONE BOTTOM CHCL3
C
ATM
KGMOL/HR
ENTFEED MAKERECYCLE
UP
Stream Description
Vapor
Liquid Vapor
59.156
118.882 64.198
Liquid
194.423
Liquid Liquid
50.000 50.000
1.100
50.000
1.100
127.461
1.100
50.000
1.100
77.461
1.100 1.100
100.000 0.001
0.995
0.005
0.000
0.002
0.390
0.608
0.005
0.995
0.000
0.000
0.000
1.000
0.500
0.500
0.000
0.000
0.000
1.000
Table 5 Consumption of cooling water and steam
Cooling water (Kg/hr)
Steam (Kmol/hr)
Figure 5: Effect of solvent flow rate on the re-boiler heat duty
at constant reflux ratio for the acetone-chloroform-dmso
system
Figure 6: Effect of solvent flow rate and reflux ratio on the
amount of chloroform on the distillate stream
1st column
40469
114.5
2nd column
35050
75.35
RESULT AND DISCUSSION
A study for the separation of the acetone-chloroform system
has been made using DMSO as a solvent. In our study, the
optimum solvent flow rate as depicted by (Luyben 2013)
which was 164.4 Kmol/hr has been reduced to 135.286
Kmol/hr using UNIQUAC model and 77.47 Kmol/hr using
NRTL model suggesting NRTL a better thermodynamic
model for the system. Therefore, the total re-boiler heat duty
of 2.259M*kcal/hr (2.62MW)as illustrated by (Luyben 2008)
has been reduced to1.7756 M*kcal/hr thereby minimizing the
re-boiler heat duty by about 78%. During the optimization
process, it was observed that there was a non-monotonic
effect on each manipulated variable as acknowledged by
many authors (Shen et al. 2015) and (Lei et al. 2003). To
illustrate, the reflux ratio and solvent flow rate are affected by
the feed stages. Higher solvent flow rate leads to higher
acetone purity as shown is Figure 9 but minJ declines since
Qr increases.
CONCLUSION:
In this study, we proposed a systematic process for an
extractive distillation for the separation of acetone-chloroform
(maximum boiling) azeotrope using DMSO as solvent. The
conceptual design using ternary diagram was illustrated for
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International Journal of Applied Engineering Research ISSN 0973-4562 Volume 11, Number 12 (2016) pp 7772-7775
© Research India Publications. http://www.ripublication.com
acetone-chloroform-DMSO system. For the given set of given
VLE data, our system was inclined towards NRTL model
rather than UNIQUAC. The VLE data upon regression were
used for the simulation process. From the above discussion,
one can conclude that DMSO is a promising solvent that can
be used for the separation of acetone-chloroform system.
NOTATION
VLE-vapour liquid equilibrium
NRTL-nonrandom two liquid
UNIQUAC-universal quasichemical
DMSO-Dimethyl sulfoxide
EG-ethylene glycol
Qr-total energy consumption
D-Distillate
[13]
[14]
[15]
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