Modeling and Optimization of Fixed-Bed Fischer-Tropsch Synthesis Using Genetic Algorithm

Document Type: paper

Authors

1 Department of Chemical and Petroleum Engineering, Sharif University of Technology, Tehran, Iran

2 Department of Energy Engineering, Sharif University of Technology, Tehran, Iran

Abstract

  In this paper, modeling and optimization of Fischer-Tropsch Synthesis is considered in a fixed-bed catalytic reactor using an industrial Fe-Cu-K catalyst. A one dimensional pseudo-homogenous plug flow model without axial dispersion is developed for converting syngas to heavy hydrocarbons. The effects of temperature, pressure, H2 to CO ratio in feed stream, and CO molar flow on the mass flow rate of the desired product (C5+) are investigated. Since the Fischer-Tropsch synthesis produces a wide range of hydrocarbon products, it is important to optimize the reactor operating parameters and feed conditions to maximize yield of reactor. Genetic algorithm was used as the optimization algorithm in this study. The processing variables are defined in the following ranges: Temperature: 493-542 K, Pressure: 10.9-30.9 bar, CO molar flow: 0.0815-0.3074 gmole/s and the H2/CO feed ratio: 0.98-2.99. A reactor model was developed and along with appropriate reaction kinetics, the performance of the reactor was investigated. Model results were in good agreement with experimental data. After validating the model, the production of C5+ was optimized. The results indicated that the production of C5+ increased with increasing pressure while it decreased with increasing temperature, H2/CO ratio, and CO molar flow rate in the feed stream.

Keywords


[1] Wang, Y. N., Xu, Y. Y., Li, Y. W., Zhao, Y. L. and Zhang, B. J. (2003). “Heterogeneous modeling for fixed bed reactor for Fischer-Tropsch synthesis: Reactor model and its applications.” Chemical Engineering Science, Vol. 58, PP. 867-875.

[2] Anastai, J. L. (1980). “SASOL: South Africa’s oil from coal story - background for environmental assessment.” U.S. EPA report 600/8-80-002.

[3] Sie, S. T. and Krishna, R. (1999). “Fundamentals and selection of advanced Fischer–Tropsch reactors.” Applied Catalysis A: General, Vol. 186, PP. 55-70.

[4] Jess, A. and Kern, C. (2009). “Modeling of multi-tubular reactors for Fischer-Tropsch synthesis.” Chemical Engineering Technology, Vol. 32, PP. 1164-1175.

[5] Rafiq, M. H., Jakobsen, H. A., Schmid, R. and Hustad, J. E. (2011). “Experimental studies and modeling of a fixed bed reactor for Fischer-Tropsch synthesis using biosyngas.” Fuel Processing Technology, Vol. 92, PP. 893-907.

[6] Fernandes, F. A. N. and Teles, U. M. (2007). “Modeling and optimization of Fischer–Tropsch products hydrocracking.” Fuel Processing Technology, Vol. 88, PP. 207-214.

[7] Fernandes, F. A. N. (2005). “Polymerization kinetics of Fischer-Tropsch reaction on iron-based catalyst and product grade optimization.” Chemical Engineering Technology, Vol. 28, PP. 930-938.

[8] Wang, Y., Fan, W., Liu, Y., Zeng, Z., Hao, X., Changa, M., Zhang, C., Xu, Y., Xiang, H. and Li, Y. (2008). “Modeling of the Fischer–Tropsch synthesis in slurry bubble column reactors.” Chemical Engineering and Processing, Vol. 47, PP. 222–228.

[9] Schweitzer, J. M. and Viguié, J. C. (2009). “Reactor modeling of a slurry bubble column for Fischer-Tropsch synthesis.” Oil & Gas Science and Technology, Vol. 64, PP. 63-77.

[10] Fernandes, F. A. N. (2006). “Modeling and product grade optimization of Fischer-Tropsch synthesis in a slurry reactor.” Industrial Engineering & Chemistry Research, Vol. 45, PP. 1047-1057.

[11] Sehabiague, L., Lemoine, R., Behkish, A., Heintz, Y. J., Sanoja, M., Oukaci, R. and Morsi, B. I. (2008). “Modeling and optimization of a large-scale slurry bubble column reactor for producing 10,000 bbl/day of Fischer-Tropsch liquid hydrocarbons.” Journal of the Chinese Institute of Chemical Engineers, Vol. 39, PP. 169-179.

[12] Wang, Y. N., Ma, W. P., Lu, Y. J., Yang, J., Xu, Y. Y., Xiang, H. W., Li, Y. W., Zhao, Y. L. and Zhang, B. J. (2003). “Kinetics modelling of Fischer-Tropsch synthesis over an industrial Fe-Cu-K catalyst.” Fuel, Vol. 82, PP. 195-213.

[13] Froment, G. F. and Bischoff, K. B. (1979). Chemical reactor analysis and design. 1st Ed. John Wiley & Sons, New Jersey, USA.

[14] Steynberg, A. P. and Dry, M. E. (2004). In Studies in Surface Science and Catalysis: Fischer-Tropsch Technology. 1st Ed. Elsevier, Amsterdam, Netherlands.

[15] Holman, J. P. (1997). Heat transfer. 8th Ed. McGraw Hill, USA.

[16] Megyesy, E. F. (2001). Pressure Vessel Handbook. 12th Ed. Pressure Vessel Publishing, Tulsa, Oklahoma, USA.

[17] Ludwig, E. E. (1990). Applied process design for chemical and petrochemical plants. Vol 3, 3rd Ed. Gulf Professional Publishing, Oxford, United Kingdom.

[18] Holland, J. H. (1975). Adaptation in natural and artificial systems. 1st Ed. University of Michigan Press, Ann Arbor, USA.

[19] Goldberg, D. E. (1989). Genetic algorithms in search, optimization and machine learning. 1st Ed. Addison Wesley, Boston, USA.

[20] Hwang, S. and He, R. (2006). “A hybrid real-parameter genetic algorithm for function optimization.” Advanced Engineering Informatics, Vol. 20, PP. 7-21.

[21] Haupt, R. L. and Haupt, S. E. (2004). Practical genetic algorithms. 2nd Ed. John-Wiley & Sons, New Jersey, USA.