Effect of Inlet Downcomer on the Hydrodynamic Parameters of Sieve Trays Using CFD Analysis


Shahid Nikbakht,s Faculty of Engineering, Department of Chemical Engineering, University of Sistan and Baluchestan


Nowadays distillation is recognized as one of the economical and the most trustable separation methods in chemical, petroleum, gas and petrochemical industries. It is almost used as a first and the most applicable choice in separation methods. In this article the effect of inlet downcomer on the hydrodynamics of industrial sieve tray has been elaborated. The study was carried out by using a 3-D Computational Fluid Dynamics (CFD) method and was confirmed with experimental data. Commercial Ansys CFX 11 package software was used for the CFD analysis. Liquid velocity distribution on the tray was in better agreement with experimental data in comparison with simulation results without including inlet downcomer effect. Hydrodynamic parameters of clear liquid height, froth height and average liquid volume fraction in froth were predicted and compared with two available correlations. It was concluded that for having a better simulation model and hence having a deeper insight into tray performance, the downcomer effect on the mass transfer and hydraulic should be considered with CFD analysis.


[1] Lockett, M.J. (1986). Distillation tray fundamentals, Cambridge University Press, Cambridge.
[2] Alexandrov, LA. and Vybornov, V.G. (1971). “Investigation of the hydrodynamic pattern of liquid flow on crossflow trays.” Tear. Osnovy Kim. Tekn., Vol. 5, 339.
[3] Bell, R.L. (1972). “Experimental determination of residence time on commercial scale distillation trays using fiber optic technique,” AIChE J., Vol. 18, PP. 491-497.
[4] Porter, K.E., Lockett, M.J. and Lim, C.T. (1972). “The effect of liquid channeling on distillation plate efficiency,” Trans. Inst. Chem. Engrs., Vol. 50, PP. 91-101.
[5] Bruin, S. and Freije, A.D. (1974). “A simple mixing model for distillation plates with stagnant zones.” Trans. Inst. Chem. Engrs., Vol. 52, PP. 75-79.
[6] Bell, R.L. and Solari, R.B. (1974). “Effect of nonuniform velocity fields on distillation tray efficiency,” AIChE J., Vol. 20, PP. 688-695.
[7] Lockett, M.J. and Safekourdi, A. (1976). “The effect of the liquid flow pattern on distillation plate efficiency.” Chem. Eng. J., Vol. 11, PP. 111-121.
[8] Sohlo, J. and Kinnunen, S. (1977). “Dispersion and flow phenomena on a sieve plate.” Trans. Inst. Chem. Engrs., Vol. 55, PP. 71-73.
[9] Solari, R.B., Saez, A.E., Apollo, I. D. and Bellet, A. (1982). “Velocity distribution and liquid flow patterns on industrial sieve trays." Chem. Eng. Commun., Vol. 13, PP. 369-384.
[10] Lockett, M.J. and Ahmed, I.S. (1983). “Tray and point efficiencies from a 0.6 m diameter distillation column.” Chem. Eng. Res. Des. , Vol. 6, PP. 110-118.
[11] Solari, R.B. and Bell, R.L., (1986). “Fluid flow patterns and velocity distribution on commercial-scale sieve trays.” AIChE J., Vol. 32, PP. 640-649.
[12] Arreaza, G. (1986). M. Sc. Thesis, Universidad Simon Bolivar.
[13] Mehta, B., Chuang, K.T. and Nandakumar, K. (1998). “Model for liquid phase flow on sieve trays.” Chem. Eng. Res. Des., Trans.IChemE, Vol. 76, PP. 843-848.
[14] Fischer, C.H. and Quarini, J.L. (1998). “Three-dimensional heterogeneous modeling of distillation tray hydraulics." AIChE Meeting, Miami Beach, FL.
[15] Yu, K.T., Yuan, X.G., You, X.G. and Liu, C.T. (1999). “Computational fluid-dynamics and experimental verification of two-phase two-dimensional flow on a sieve column tray.” Trans. Inst. Chem. Eng., Part A., Vol. 77, PP. 554-560.
[16] Liu, C.J., Yuan, X.G., Yu, K.T. and Zhu, X.J. (1999). “A fluid dynamic model for flow fattern on a distillation tray." Chem. Eng. Sci., Vol. 55, PP. 2287-2294.
[17] Krishna, R., Van Baten, J.M., Ellenberger, J., Higler, A.P. and Taylor, R. (1999). “CFD simulations of sieve tray hydrodynamics.” Trans.IChemE, Vol. 77, PP. 639-646.
[18] J Van Baten, J.M. and Krishna, R. (2000). “Modeling sieve tray hydraulics using computational fluid dynamics." Chem.Eng.J., Vol. 77, PP. 143-151.
[19] Krishna, R. and Van Baten, J.M. (2003). “Modeling sieve tray hydraulics using computational fluid dynamics." Trans.IChemE., Vol. 81, PP. 27-38.
[20] Bennett, D.L., Rakesh Agrawal and Cook, P.J. (1983). “New pressure drop correlation for sieve tray distillation columns.” AIChE J., Vol. 29, PP. 434-442.
[21] Gesit, G., Nandakumar, K. and Chuang, K.T. (2003). “CFD modeling of flow patterns and hydraulics of commercial-scale sieve trays.” AIChE J., Vol. 49, PP. 910-924.
[22] Wang, X. L., Liu, C. J., Yuan X. G. and Yu, K. T. (2004). “Computational fluid dynamic simulation of three-dimensional liquid flow and mass transfer on distillation column trays." Ind.Eng.Chem.Res., Vol. 43, PP. 2556-2567.
[23] Rahimi, R., Rahimi, M.R., Shahraki, F. and Zivdar, M. (2006). “Efficiencies of sieve tray distillation columns by CFD simulations.” Chem. Eng and Technol, Vol. 29, No. 3, PP. 326-335.
[24] Krishna, R., Urseanu, M.I., van Baten, J.M. and Ellenberger, J. (1999). “Rise velocity of a swarm of large gas bubbles in liquids." Chem. Eng. Sci., Vol. 54, PP. 171-183.
[25] CFX User Manual, ANSYS, Inc. Modeling, CFX 11.0: Solver.
[26] Zarei, T., Rahimi, R. and Zivdar, M. (2009). “Computational fluid dynamic simulation of MVG tray hydraulics.” Korean J. Chem. Eng., Vol. 26, PP. 1213-1219.
[27] Zarei, A. (2010). Investigation of weeping and entrainment effects on the distillation tray by CFD, M. Sc. Thesis, University of Sistan and Baluchestan, Zahedan, Iran.
[28] Colwell, C.J. (1981). “Clear liquid height and froth density on sieve trays.” Ind. Eng. Chem. Proc. Des. Dev., Vol. 20, PP. 298-306.