 Open Access
 Total Downloads : 544
 Authors : Vikas Dinkar Gosavi, Mohini Premmurari Dubey
 Paper ID : IJERTV2IS101136
 Volume & Issue : Volume 02, Issue 10 (October 2013)
 Published (First Online): 25102013
 ISSN (Online) : 22780181
 Publisher Name : IJERT
 License: This work is licensed under a Creative Commons Attribution 4.0 International License
Study on Redressing the Thermodynamic Property Package forProcess Simulator
Vikas Dinkar Gosavi 1*, Mohini Premmurari Dubey 1
1Department of Chemical Engineering, Institute of Technology, Nirma University, Ahmedabad 382481, Gujarat, India
Abstract
This paper describes the importance of redression of binary interaction parameter for selected thermodynamic property package in process simulator. The work has been made in this paper to redress the binary interaction parameter for nonideal or complex binary systems of 2ethoxyethanol + dinpropyl ether, 1propanol + 2ethoxyethanol, 1propanol + din propyl ether. In this study, redressed value of the binary interaction parameters for UNIQUAC model fitted in CHEMCAD simulation software for comparing the bubble point pressure from experimental data and simulator data to increase the accuracy of simulation result.
Keywords: Activity coefficient, Binary interaction parameter, Redression, Regression, 2ethoxyethanol, 1 propanol.

Introduction
Dinpropyl ether (DPE) can be manufactured from reaction of 1propanol (PA) with H2SO4, and complete separation of dinpropyl ether can be archived with the help of 2ethoxyethanol (trade name is Cellosolve) as solvent. Cellosolve mainly used as a solvent in industries or laboratory practices to dissolve resin, waxes, lacquers, grease, oils and nitrocellulose. Extractive distillation operation is used for separation of a DPE + PA. Cellosolve form a complex or non ideal mixture with 1propanol and dinpropyl ether [1]. For designing of a distillation system vapor liquid equilibrium (VLE) data play vital role in it [2]. Process simulator like CHEMCAD simulation software can be used for design of such distillation system.
Process simulator is an outstanding tool for analyzing, designing, rating and optimizing the process plants, refineries, chemical plants. In process simulator, various kind of thermodynamic property packages are used such as equation of state (EOS), activity models, vapor pressure models, chao seader and grayson streed
models, other special models etc. Mainly thermodynamic activity models are used for non standard or complex system. Binary interaction parameter (BIP) is the heart of the activity model and its value calculated with the help of the data regression analysis from experimental vapor liquid equilibrium (VLE) data. However, no one of activity model is accurate and often some adjustment must be done before their applications. Researchers have already provided BIP data for various mixtures in databank of process simulator. Before actual simulation, must check the accuracy and validity of thermodynamic property package. Convergence of flowsheet in process simulator does not give the guaranty of correct results [3]. Use of improper redressed binary interaction parameter (BIP) in process simulator which generates the result which deviates from reality. Prior to their application of process simulator with thermodynamic property package redressing of the binary interaction parameter with checking the converged result and its accuracy within allowable range, if not then thermodynamic property package should be redressed to enhance its accuracy [4]. This redressing can be done by VLE calculation such as dew point, bubble point or flash calculation and comparing the result with experimental data. Experimental VLE data for 2 ethoxyethanol + DPE (Table 1) [5], PA + 2
ethoxyethanol (Table 2) [6], PA + DPE (Table 3) [7] system has taken from literature and simulated VLE data is generated from CHEMCAD V6.0, using UNIQUAC thermodynamic activity model.

Theory

UNIQAC Activity Model
UNIQUAC equation is equipped with two parts; a combinatorial part of UNIQUAC equation is describing the entropic contribution and residual part stand for the intermolecular forces. The combinatorial part requires only pure component data like sizes and shapes of molecules. The two binary interaction parameters arise only in the residual part of UNIQUAC equation [8].
GE
The UNIQUAC equation, substituting = G , is
RT
Table 1: Experimental vaporliquid equilibrium data for the binary system of 2ethoxyethanol (1) + din
given by 2 2 2 propyl ether (2) at 333.15K [5]
G = GC(combinatori2al) + GR(residual) (1)
C
2 2 2
2 21 2 12
P (N/m2) X
G =[x1ln
X
R
+ x ln
X2
+ (q1x1ln
+ q x ln )J
2
1
37092 0.0000
G = q1x1ln(01 + 0 r21) q x ln(0 + 01r12)]
Where,
i
i
8 = Area fraction of component i = Xiqi
Xjqj
i
i
= Volume fraction of component i = Xiri
j j
j j
X r
qi = Surface area parameter of component i ri = Volume parameter of component i
rij= Area Parameter
(uijujj)
36634 0.0395
35738 0.0895
34283 0.1778
32637 0.2878
30856 0.4081
28594 0.5361
26455 0.6310
23462 0.7311
21037 0.7923
17717 0.8573
ij
ij
= exp [A
RT
+ Cijln(T) + Dij T]
14328 0.9072
11746 0.9414
T = Temperature in degrees Kelvin
Z = 10 (coordination number)
The UNIQUAC BIPs of Aij, (UijUjj), and (UjiUii) are in cal/gmol. The binary interaction parameters Cij and Dij are optional. When regressing BIPs for UNIQUAC model, calculates only (U U ), and (U U ) with
9057 0.9655
7471 0.9817
6787 0.9864
5874 0.9947
5486 0.9981
5278 1.0000
ij jj ji ii
considering Aij and Aji are set to zero.
2.2 Effect of BIP on prediction of bubble point pressure
Bubble point pressure is defined as the pressure point at which the first bubble of gas comes out of the solution. At constant temperature bubble point pressure data with their corresponding liquid composition data arise
Table 2: Experimental vaporliquid equilibrium data for the binary system of npropyl alcohol (1) + 2 ethoxyethanol (2) at 313.15K [6]
P (N/m2) X1
1865 0.0000
from VLE experiment. According to the research
2224
0.0606
studies, BIP value shows inherent temperature
2452
0.1001
dependency [9,10]. The degree of temperature
2732
0.1500
dependency of BIP is closely related to complexity in
3005
0.1997
thermodynamic model. Those complexities increase the
3282
0.2503
temperature dependency of BIP which lead to decrease
3550
0.2997
the property prediction ability [11]. BIP is an empirical
3813
0.3497
from VLE experiment. According to the research
2224
0.0606
studies, BIP value shows inherent temperature
2452
0.1001
dependency [9,10]. The degree of temperature
2732
0.1500
dependency of BIP is closely related to complexity in
3005
0.1997
thermodynamic model. Those complexities increase the
3282
0.2503
temperature dependency of BIP which lead to decrease
3550
0.2997
the property prediction ability [11]. BIP is an empirical
3813
0.3497
2046 0.0298
value and it has no theoretical explanation. Binary interaction parameters are calculated from data regression analysis. In data regression analysis,
4070 0.3997
4326 0.4498
4578 0.4998
minimise the objective function to find out the accurate
4829
0.5499
binary interaction parameter for thermodynamic model
5072
0.5999
[12,13]. UNIQAUC model were capable of precisely 5309
0.6499
correlating the highly nonideal or complex binary and
5554
0.7000
ternary systems [14]. For redressing the BIP, try to
5785
0.7498
simulate the same condition with UNIQAUC model in
6022
0.7998
CHEMCAD simulator as the condition at which
6249
0.8496
experimental data were obtained, and observed how 6477
0.8998
accurately the model can match them. Then find out the 6662
0.9401
6785
0.9701
minimise the objective function to find out the accurate
4829
0.5499
binary interaction parameter for thermodynamic model
5072
0.5999
[12,13]. UNIQAUC model were capable of precisely 5309
0.6499
correlating the highly nonideal or complex binary and
5554
0.7000
ternary systems [14]. For redressing the BIP, try to
5785
0.7498
simulate the same condition with UNIQAUC model in
6022
0.7998
CHEMCAD simulator as the condition at which
6249
0.8496
experimental data were obtained, and observed how 6477
0.8998
accurately the model can match them. Then find out the 6662
0.9401
6785
0.9701
4825 0.5498
absolute relative deviation (ARD) from simulated result and experimental value.
1
1
% ARD = N Pexp – Psim Ã— 100
N i Pexp
6939 1.0000
Step to analyze the effect of BIP on prediction of bubble point pressure:

Find out the BIPs (UijUii and UjiUjj) for UNIQUAC model from data regression with help of experimental VLE data.

Compared the experimental values with result generated from process simulator with default value of BIPs as well as redressed value of BIPs.

Calculate the average relative deviation (ARD) between experimental values and CHEMCAD simulator generated result.

Redresses the BIP to minimize the %ARD till simulated result match with experimental
table 4. Compare the simulator generated results of bubble point pressure for binary mixtures of PA (i) + 2 ethoxyethanol (j) and PA (i) + DPE (j) with their corresponding experimental data and that comparison graphically demonstrates in figure 2 and 3 respectively. Reductions in average relative deviation (ARD) for binary mixtures of PA (i) + 2ethoxyethanol (j) and PA
(i) + DPE (j) are tabulated in table 5.
value.
Table 3: Experimental vaporliquid equilibrium data for the binary system of npropyl alcohol (1) + din propyl ether (2) at 333.15K [7]
P (N/m2) X1
26566
0.0842
26772
26923
0.1105
0.1462
10000
27019
0.1759
27116
0.2037
27026
0.2854
0
26379
0.4165
0
0.2
0.4
0.6
0.8 1
25521
0.5314
Mole % of 2ethoxyethanol
25093
0.5821
23070
0.7128
22891
0.7226
Figure 1: Effect of BIP on B.P.P. of 2ethoxyethanol +
20953
0.8075
DPE at 333.15K
16117
0.9337
26566
0.0842
26772
26923
0.1105
0.1462
10000
27019
0.1759
27116
0.2037
27026
0.2854
0
26379
0.4165
0
0.2
0.4
0.6
0.8 1
25521
0.5314
Mole % of 2ethoxyethanol
25093
0.5821
23070
0.7128
22891
0.7226
Figure 1: Effect of BIP on B.P.P. of 2ethoxyethanol +
20953
0.8075
DPE at 333.15K
16117
0.9337
25145 0.0000
40000
Bubble point pressure (N/m2)
Bubble point pressure (N/m2)
30000
20000
Redressed value of BIP
Experimental Data
Default value of BIP in CHEMCAD
12238 1.0000



Result and Discussion
The effects of BIP (UijUii / UjiUjj) on bubble point pressure for mixture 2ethoxyethanol (i) + DPE (j) at 333.15K for a 2ethoxyethanol in liquid phase were forecasted using UNIQUAC in CHEMCAD V 6.0. Initially, the default value of the BIP in the databank of CHEMCAD UijUii = 0 and UjiUjj = 0 was used. The simulator generator result compared with experimental data and average relative deviation (ARD) for nineteen data point to be 20.347%. Redressed value of BIPs Uij Uii = 249.89 and UjiUjj = 629.102 was predicted with the help of data regression analysis of experimental value with UNIQUAC model. That redressed value of BIPs was reducing the 20.347% ARD to 3.483% ARD. The effects of BIP on bubble point pressure graphically represented in fig 1. That figure 1 clearly shows that the importance of redression of BIP for improving the accuracy of simulation result. Redression is substantial and accuracy of simulation much more improved. Similar improvements are observed for binary mixtures of PA (i) + 2ethoxyethanol (j) and PA (i) + DPE (j) at 313.15K and 323.15K respectively, the default value of BIP in databank of CHEMCAD for both binary mixtures are UijUii = 0 and UjiUjj = 0 and redressed value of BIP for binary mixtures of PA (i) + 2 ethoxyethanol (j) and PA (i) + DPE (j) are tabulated in
Table 4: BIP for binary mixture
Binar mixture
Default value of BIP in CHEMCAD
Redressed value of BIP
2ethoxyethanol
(i) + DPE (j)
UijUii = 0
UjiUjj = 0
UijUii = 249.89
UjiUjj = 629.102
PA (i) + 2
ethoxyethanol (j)
UijUii = 0
UjiUjj = 0
UijUii = 69.3672
UjiUjj = 116.633
PA (i) + DPE (j)
UijUii = 0
UjiUjj = 0
UijUii = 240.7538
UjiUjj = 703.182
Redressed values of BIP in UNIQUAC model has been shown remarkable improvement in the simulation result. Table 5 clearly shows that the importance of binary interaction parameters in UNIQUAC for enhancing the predictability of process simulator. Remarkable improvement is observed in % ARD for binary systems of 2ethoxyethanol + DPE, PA + 2 ethoxyethanol, PA + DPE. Property prediction of the binary and ternary systems or behaviour of the system with other process variable is greatly predicted with the help of redressed value of BIP in model.
Bubble point pressure (N/m2)
Bubble point pressure (N/m2)
8000
6000
4000
2000
0
Experimental Data Default value of BIP
in CHEMCAD
Redressed value of BIP
0 0.2 0.4 0.6 0.8 1
Mole % of 1propanol

Conclusion
This paper demonstrate that the binary interaction parameters of an UNIQUAC model can be redressed to enhance the accuracy of process simulator considerably and also provide a step wise procedure for redression of the binary interaction parameter for thermodynamic model in process simulator. In this work, current discrepancies between default value of BIP in CHEMCAD simulation software and redressed value of BIP were analysed and study the impact of redression of binary interaction parameter for prediction of bubble point pressure for given system. These studies are clearly shows that the necessities of validation of the accuracy of thermodynamic models prior to performing simulation work. While accurately redressed value of BIPs for thermodynamic model in process simulator which has ensures that the simulator generated result as
Figure 2: Effect of BIP on B.P.P. of PA + 2
ethoxyethanol at 313.15K
good as experimental value.

Acknowledgements
Bubble point pressure (N/m2)
Bubble point pressure (N/m2)
40000
30000
20000
10000
0
Default value of BIP in CHEMCAD
Experimental Data
Redressed value of BIP
0 0.2 0.4 0.6 0.8 1
Mole % of 1propanol
The authors would like to acknowledge from beneath of the heart to the Department of Chemical Engineering, Nirma University for providing congenial environment for completing this study.

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