MODELING AND SIMULATION OF A BENZENE RECOVERY PROCESS BY EXTRACTIVE
               DISTILLATION

Brondani, L. B.; Flores, G. B.; Soares, R. P.

doi:10.1590/0104-6632.20150321s00002825

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Brazilian Journal of Chemical Engineering

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THERMODYNAMICS • Braz. J. Chem. Eng. 32 (1) • Jan-Mar 2015 • https://doi.org/10.1590/0104-6632.20150321s00002825 copy

MODELING AND SIMULATION OF A BENZENE RECOVERY PROCESS BY EXTRACTIVE DISTILLATION

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Extractive distillation processes with N-formylmorpholine (NFM) are used industrially to separate benzene from six carbon non-aromatics. In the process studied in this work, the stream of interest consists of nearly 20 different hydrocarbons. A new set of NRTL parameters was correlated based on literature experimental data. Both vapor-liquid equilibrium as well as infinite dilution activity coefficient data were taken into account; missing parameters were estimated with the UNIFAC group contribution model. The extractive distillation process was simulated using ASPEN Plus®. Very good agreement with plant data was obtained. The influences of the main operational parameters, solvent to feed ratio and solvent temperature, were studied. Theoretical optimum operating values were obtained and can be implemented to improve the industrial process. Extreme static sensitivity with respect to reboiler heat was observed, indicating that this can be the source of instabilities.

Extractive distillation; N-formylmorpholine; NFM; Process simulation; Benzene

Component / NFM	Liquid-liquid equilibrium	Vapor-liquid equilibrium	Inf. Dil. Activity Coef.
CP	*Ko et al,* 2003**Ko, M., Na, S., Lee, S. and Kim, H., Liquid-liquid equilibria for the binary systems of N-formylmorpholine with cycloalkanes. J. Chem. Eng. Data, 48, p. 249-252 (2003).		DDBST
n-HX	*Cincotti et al,* 1999**Cincotti, A., Murru, M., Cao, G., Marongiu, B., Masia, F. and Sannia, M., Liquid-liquid equilibria of hydrocarbons with N-formylmorpholine, J. Chem. Eng. Data, 44, p. 480-483 (1999). ;		DDBST; Krummen & Gmehling, 2004Krummen, M. and Gmehling, J., Measurement of activity coefficients at infinite dilution in Nmethyl-2-pyrrolidone and N-formylmorpholine and their mixtures with water using the dilutor technique. Fluid Phase Equilibria, 215, p. 283-294 (2004).
	*Ko et al,* 2002 (b)**Ko, M., Lee, S., Cho, J. and Kim, H., Liquid-liquid equilibria for binary systems containing N-formylmorpholine. J. Chem. Eng. Data, 47, p. 923-926 (2002)b.
MCP	*Ko et al,* 2003**Ko, M., Na, S., Lee, S. and Kim, H., Liquid-liquid equilibria for the binary systems of N-formylmorpholine with cycloalkanes. J. Chem. Eng. Data, 48, p. 249-252 (2003).		*Knoop et al.,* 1989**Knoop, C., Tiegs, D. and Gmehling, J., Activity coefficients at infinite dilution (NFM - Methylcyclopentane). J. Chem. Eng. Data, 34(2), p. 240-247 (1989). and
			*Weidlich et al.,* 1987**Weidlich, U., Roehm, H. and Gmehling, J., Activity coefficients at infinite dilution (NFM - Methylcyclopentane). J. Chem. Eng. Data, 32(4), p. 450-453 (1987).
BZ		DDBST and Yin, 2010Yin, W., Ding, S., Xia, S., Ma, P., Huang, X. and Zhu, Z., Cosolvent selection for benzene-cyclohexane separation in extractive distillation. J. Chem Eng. Data, 55, p. 3274-3277 (2010).	DDBST
CH	*Ko et al,* 2003**Ko, M., Na, S., Lee, S. and Kim, H., Liquid-liquid equilibria for the binary systems of N-formylmorpholine with cycloalkanes. J. Chem. Eng. Data, 48, p. 249-252 (2003).		DDBST
n-HP	*Cincotti et al,* 1999**Cincotti, A., Murru, M., Cao, G., Marongiu, B., Masia, F. and Sannia, M., Liquid-liquid equilibria of hydrocarbons with N-formylmorpholine, J. Chem. Eng. Data, 44, p. 480-483 (1999). ;		DDBST; Krummen & Gmehling, 2004Krummen, M. and Gmehling, J., Measurement of activity coefficients at infinite dilution in Nmethyl-2-pyrrolidone and N-formylmorpholine and their mixtures with water using the dilutor technique. Fluid Phase Equilibria, 215, p. 283-294 (2004).
	*Qattan et al,* 1995**Qattan, M., Al-Sahhaf, T. and Fahim, M., Liquidliquid equilibria in some binary and ternary mixtures with N-formylmorpholine. J. Chem. Eng. Data, 40, p. 88-90 (1995). ;
MCH	*Ko et al,* 2003**Ko, M., Na, S., Lee, S. and Kim, H., Liquid-liquid equilibria for the binary systems of N-formylmorpholine with cycloalkanes. J. Chem. Eng. Data, 48, p. 249-252 (2003).	DDBST	DDBST

Component/NFM	VLE and/ or LLE regression	IDAC regression	*Ko et al.,* 2002 (a)**Ko, M., Na, S., Cho, J. and Kim, H., Simulation of the recovery process by extractive distillation. Korean J. Chem. Eng., 19(6), p. 996-1000 (2002)a.	*Zhu et al.,* 2008**Zhu, H., Shi, X. and Zhou, W., Process Simulation and parameter optimization of separating aromatics and non-aromatics by extractive distillation with N-formylmorpholine. Journal of East China University of Science and Technology (Natural Science Edition), 34, p. 309-314 (2008).
CP	X	X	X	X
n-HX	X	X	X	X
MCP	X	X		X
BZ	X	X	X	X
CH	X	X	X	X
n-HP	X	X	X	X
MCH	X	X		X

Comp. i	CP	n-HX	MCP	BZ	CH	n-HP	MCH
Comp. j	NFM	NFM	NFM	NFM	NFM	NFM	NFM
a_ij	0.791	0.16	0.543	17.09	0.827	0.069	0.501
a_ji	-1.51	-2.13	-1.35	-12.3	-2.29	-2.39	-2.32
b_ij	891.5	1006	937.0	-1000	847.9	1036	922.8
b_ji	863.3	1380	932.1	952.7	1235	1563	1350
c_ij	0.300	0.300	0.300	0.300	0.300	0.300	0.300

Comp. i	2,3DMB	2MP	3MP	2,4DMP	2MH	2,3DMP	1,1DMCP	3MH	c1,3DMCP	t1,3DMCP	t1,2DMCP
Comp. j	NFM	NFM	NFM	NFM	NFM	NFM	NFM	NFM	NFM	NFM	NFM
b_ij	1101	1101	1101	1070	1070	1070	1101	1070	1109	1109	1109
b_ji	520	521	521	639	640	639	522	640	507	507	507
c_ij	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3

Configuration	Number of stages	71
	Condenser	Total
	Reboiler	Thermosiphon
	Valid phases	VLL
	Convergence	Strongly non-ideal liquid
Streams	Solvent Feed	Above-stage 14 Above-stage 38
Pressure (bar_g)	Top stage pressure	1.05
	2-13 section AP	0.02
	14-37 section AP	0.04
	38-70 section AP	0.13
	Bottom stage	1.24
	pressure
Condenser (°C)	Both reflux and liquid distillate are sub cooled	51.5
Reboiler (°C)	Temperature change	32

Components	Feed mass composition in % (plant = model)	Top mass composition (%) - plant	Top mass composition (%) - model	Top composition absolute error (%)	Bottom mass fraction - model
Cyclopentene	0.11	0.41	0.37	0.03	0.00
2,3-dimethylbutane	0.14	0.44	0.49	-0.05	0.00
2-methylpentane	1.84	6.31	6.33	0.02	0.00
3-methylpentane	1.36	4.66	4.66	0.00	0.00
n-hexane	4.41	15.28	15.13	0.16	0.00
Methylcyclopentane	13.26	45.34	45.51	-0.17	0.00
2,4-dimethylpentane	0.10	0.33	0.33	0.01	0.00
Benzene	71.87	3.50	3.49	0.01	10.54
Cyclohexane	3.12	10.62	10.71	-0.08	0.00
2-methylhexane	0.58	2.05	1.99	0.06	0.00
2,3-dimethylpentane	0.05	0.18	0.18	0.00	0.00
1,1 -dimethylcyclopentane	0.24	0.83	0.82	0.01	0.00
3-methylhexane	0.47	1.66	1.63	0.04	0.00
cis-1,3-dimethylcyclopentane	0.66	2.29	2.27	0.02	0.00
trans-1,3-dimethylcyclopentane	0.47	1.63	1.61	0.01	0.00
trans-1,2-dimethylcyclopentane	0.65	2.24	2.23	0.01	0.00
n-heptane	0.54	1.91	1.85	0.06	0.00
methylcyclohexane	0.12	0.40	0.41	-0.01	0.00
NFM	0.00	0.00	0.00	0.00	89.46

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