CFD Modeling of TiO2 Nano-Agglomerates Hydrodynamics in a Conical Fluidized Bed Unit with Experimental Validation

Document Type: Research Article


Faculty of Chemical Engineering, Amirkabir University of Technology, Tehran, I.R. IRAN


In the computational fluid dynamics (CFD) modeling of gas-solids two phase flow, the effect of boundary conditions play an important role in predicting the hydrodynamic characteristics of fluidized beds. In this work, the hydrodynamics of conical fluidized bed containing dried TiO2 nano-agglomerates were studied both experimentally and computationally. The pressure drop was obtained by pressure measurements and mean solid velocity in the different axial and radial positionsand their experimental values were measured by a parallel 3-fiber optical probe. The Eulerian-Eulerian multiphase model and granular kinetic theory with using Gidaspow (1994) drag function were applied in simulations. The effect of three different types of boundary conditions (BC) including no-slip/friction, free-slip/no-friction and high-slip/small-friction which were developed by Schaeffer (1987) and Johnson and Jackson (1987) were investigated. The results of the model were compared with the experimental data. The numerical simulation using free-slip/no-friction BC agreed reasonably well with the experimental pressure drop measurements. The pressure drops predicted by the simulations were in agreement with the experimental data at superficial gas velocities higher than the minimum fluidization velocity, Umf. The results for simulated mean axial solid velocity showed that the free-slip/no-friction BC was in better agreement with the experimental data compared with other boundary conditions.  


Main Subjects

[1] Tanfara H., Pugsley T., Winters C.C., Effect of Particle Size Distribution on Local Voidage in a Bench-Scale Conical Fluidized Bed Dryer, Drying Technology, 20, p. 1237 (2002)

[2] Wang T., Wang J., Yang W., Jin. Y., Experimental Study on Bubble Behavior in Gas-Liquid-Solid Three-Phase Circulating Fluidized Beds., Powder Technology, 137, p. 83 (2003).

[3] Chen Y., Wu R., Mori S., Development of a New Type of Thermogravimetric Analyzer with a Mini- Tapered Fluidized Bed. Effect of Fluidization of Particles on the Stability of the System, Chem. Energy. J., 68, p. 7 (1997).

[4] Shi Y.-F., Yu, Y.S., Fan L.T., Incipient Fluidization Condition for a Tapered Fluidized Bed, Ind. Chem. Fundam., 23, p. 484 (1984).

[5] Mathur K.B., Epstein N., "Spouted beds", Academic Press, Inc LTD., New York, 304 pp. (1974).

[6] Epstein N., Grace J.R., "Spouting of particulate solids", In: Fayed, M.E., Otten, L. (EDs.), “Handbook of power Sci. & Technol.”, (Chap.10) second ed. Chapman& Hall,New York (1997)

[7] Kwauk, M., “Fluidization- Idealized and bubbleless with applications, “Science Press and Ellis”. Horwood, Beijing, 91 (1992)

[8] Yates J.G., Newton D., Fine Particle Effects in a Fluidized Bed Reactor, Chem. Eng. Sci., 41, p. 801 (1986)

[9] Grace J.R., Sun G., Influence of Particle Size Distribution on the Performance of Fluidized Bed Reactors, Can J. Chem. Eng., 69, p. 1126 (1991).

[10] Khoe G.K., Ip T.l., Grace J.R., Rheological and Fluidization Behavior of Powders of Different Particle Size Distribution, Powder Technology, 66, p. 127 (1990)

[11] Olazar M., San Jose M.J., Lamosas R., Alvarez S., Bilbao J., Study of Local Properties in Conical Spouted Beds Using an Optical Fiber Probe, Ind. Eng. Chem. Research, 34, p. 4033 (1995).

[12] He Y.L., Qin S.Z., Lim C.J., Grace J.R., Particle  Velocity Profiles and Solid Flow Patterns in Spouted Beds, Can. J. Chem. Eng., 72, p. 561 (1994b).

[13] Olazar M., San Jose M.J., Izquierdo M.A., Ortiz de Salazar A., Bilbao J., Effect of Operating Conditions on Solid Velocity in the Spout, Annulus and Fountain of Spouted Beds, Chem. Eng. Sci., 56, p. 3585 (2001).

[14] Link J., Zeilstra C., Deen N., Kuipers H., Validation of a Discrete Particle Model in a 2D Spouted-Fluid Bed Using Non-Intrusive Optical Measuring Techniques, Can. Chem. Eng., 82, p. 30 (2004).

[15] Darelius A., Lennartsson E., Rasmuson A., Niklasson Bjorn I., Folestad S., Measurements of the Velocity Field and Frictional Properties of Wet Masses in a High Shear Mixer, Chem. Eng. Sci., 62, p. 2366 (2007a).

[16] Valverde J.M., Quintanilla M.A.S., Castellanos A., Lepek D., Quevedo J., Dave R.N., Pfeffer R., Fluidization of Fine and Ultrafine Particles Using Nitrogen and Neon as Fluidizing Jases, AIChE J., 54, p. 86 (2008).

[17] Patankar V., “Numerical heat transfer and fluid flow”, Hemisphere publishing company, (1980).

[18] Wilcox D.C., “Turbulence Modeling for CFD”, (Third ed), Hardcover, Nov. 1, (2006).

[19] Marschall K.J., Mleczko L., CFD Modeling of an Internally Circulating Fluidized Bed Reactor, Chem. Eng. Sci., 64, p. 2085 (1999).

[20] Goldschmidt M.J.V., Kuipers J.A.M., Van Swaaij W.P.N., Hydrodynamic Modeling of Dense Gas-Fluidized Beds Using the Kinetic Theory of Granular Flow: Effect of Coefficient of Restitution on Bed Dynamics, Chem. Eng. Sci., 56, p. 571 (2001).

[21] Huilin L., Yurong H., Wentie L., Ding J., Gidaspow D., Bouillard J., Computer Simulations of Gas-Solid Flow in Spouted Bed Using Kinetic-Frictional Stress Model of Granular flow, Chem. Eng. Sci., 59, p. 865 (2004).

[22] Du W., Bao X., Xu J., Wei W., "Computational Fluid Dynamics (CFD) Modeling of Spouted Bed: Influence of Frictional Stress, Maximum Packing Limit and Coefficient of Restitution of Particles". Chem. Eng. Sci., 61, p. 4558 (2006).

[23] Gidaspow D., “Multiphase Flow and Fluidization”, Academic Press,Boston, (1994).

[24] Wang S.Y., He Y.R., Lu H.L., Zheng J.X., Liu G.D., Ding Y.L., Numerical Simulations of Flow Behavior of Agglomerates of Nano-Size Particles in Bubbling and Spouted Beds with an Agglomerate-Based Approach, Trans IChemE, Part C, 85, (2007).

[25] DuarteC.R., Olazar M., Murata V.V., Barrozo M.A.S., Numerical Simulation and Experimental Study of Fluid-Particle Flows in a Spouted Bed, Powder Technol., Available Online 3 May (2008).

[26] Darelius A., Rasmuson VanWachem B., Bjorn I.N., Folestad S., CFD Simulation of the High Shear Mixing Process Using Kinetic Theory of Granular Flow and Frictional Stress Models, Chem. Eng. Sci., 63, 2188 (2008).

[27] Fan R., O. Fox R.O., Segregation in Polydisperse Fluidized Beds: Validation of a Multi-Fluid Model, Chem. Eng. Sci., 63, p. 272 (2008).

[28] Ergun S., Fluid Flow Through Packed Columns, Chem. Eng. Progress, 48, p. 89 (1952).

[29] Wen C.Y., Yu Y.H., Mechanics of Fluidization, Chem. Eng. Sci. Prog., 62, p. 100 (1966).

[30] Du W., Bao X., Xu J., Wei W., Computational Fluid Dynamics (CFD) Modeling of Spouted Bed: Assessment of Drag Coefficient Correlations, Chem. Eng. Sci., 61, p. 1401 (2006)

[31] Schaeffer D.G., Instability in the Evolution Equations Describing Incompressible Granular Flow, J. Diff. Eq. 66, p. 19 (1987).

[32] Johnson P.C., Jackson R., Frictional-Collisional Constitutive Relations for Granular Materials, with Application to Plane Shearing, J. Fluid Mech., 176, p. 67 (1987).

[33] Kalbasi M., Bahramian A., Khorshidi J., Prediction of Minimum Spout Velocity and Moisture Distribution of Amonim Perchlorate Particles in a Spouted Bed Dryer, Iranian, J. Chem. & Chem. Eng., 26, p. 113 (2007).

[34] Kalbasi M., Bahramian A., Proceeding of International Workshop and Symposium on Industrial Drying-, 20-23rd December,Mumbai,India. (2004)

[35] Taghipour F., Ellis N., Wong C., Experimental and Computational Study of Gas-Solid Fluidized Bed Hydrodynamics, Chem. Eng. Sci., 60, 6857 (2005).

[36] McKeen T., Pugsley T., Simulation and Experimental Validation of a Freely Bubbling Bed of FCC Catalyst, Powder Technol., 129, P.139 (2003).

[37] Kmiec A., Hydrodynamics of Flow and Heat Transfer in Spouted Beds, Chem. Eng. J., 19, p. 189 (1980).