Segregation patterns of an equidensity TiO2 ternary mixture in a conical fluidized bed: CFD and experimental study

Document Type: Full article

Author

Department of Chemical Engineering, Hamedan University of Technology, P.O. Box, 65155 Hamedan, Iran.

Abstract

In this study, an Eulerian-Eulerian multi-fluid model (MFM) was used to simulate the segregation pattern of a conical fluidized bed containing ternary mixtures of equidensity TiO2‌ particles. Experimental 'freeze–sieving' method was employed to determine the axial mass fraction profiles of the different-sized particles, and validate the simulation results. The profiles of mass fraction for large, medium and small sized particles along the bed height during the simulation time indicated that the particles’ segregation can be predicted by CFD model. Effect of superficial gas velocity on segregation pattern was also investigated. It was shown that for U0=1.2Umf, partial segregation of large particles occurred, while for U0=1.6Umf, small and medium size particles also segregated and full segregation was achieved. By increasing U0 to 2Umf, mixing of different sized particles was increased and particles segregation was reduced. Therefore, it can be concluded that there was a critical velocity below which particles would segregate while above which their mixing increased.

Keywords

Main Subjects


[1]      Dahl, S. R. and Hrenya, C. M., “Size segregation in gas-solid fluidized beds with continuous size distributions”, Chem. Eng. Sci., 60, 6658 (2005).

[2]      Rasteh, M., Farhadi, F. and Bahramian, A., “Hydrodynamic characteristics of gas-solid tapered fluidized beds: Experimental studies and empirical models”, Powder Technol., 283, 355 (2015),(DOI:10.1016/j.powtec.2015.06.002).

[3]      Chew, J. W., Wolz, J. R. and Hrenya, C. M., “Axial segregation in bubbling gas-fluidized beds with Gaussian and lognormal distributions of Geldart Group B particles”, AIChE J., 56, 3049 (2010).

[4]      Joseph, G. G., Leboreiro, J., Hrenya, C. M. and Stevens, A. R., “Experimental segregation profiles in bubbling gas-fluidized beds”, AIChE J., 53, 2804 (2007).

[5]      Wu, S. Y. and Baeyens, J., “Segregation by size difference in gas fluidized beds”, Powder Technol., 98, 139 (1998).

[6]      Rasul, M. G., Rudolph, V. and Carsky, M., “Segregation potential in binary gas fluidized beds”, Powder Technol., 103, 175 (1999).

[7]      Van Wachem, B. G. M., Schouten, J. C., Van den Bleek, C. M., Krishna, R. and Sinclair, J. L., “CFD modeling of gas-fluidized beds with a bimodal particle mixture”, AIChE J., 47, 1292 (2001).

[8]      Olivieri, G., Marzocchella, A. and Salatino, P., “A fluid-bed continuous classifier of polydisperse granular solids”, J. Taiwan Inst. Chem. Eng., 40, 638 (2009).

[9]      Muzzio, F. J., Shinbrot, T. and Glasser, B. J., “Powder technology in the pharmaceutical industry: The need to catch up fast”, Powder Technol., 124, 1 (2002).

[10]  Zhang, Y., Jin, B. and Zhong, W., “Experimental investigation on mixing and segregation behavior of biomass particle in fluidized bed”, Chem. Eng. Process. Process Intensif., 48, 745 (2009).

[11]  Zhang, Y., Zhao, Y., Lu, L., Ge, W., Wang, J. and Duan, C., “Assessment of polydisperse drag models for the size segregation in a bubbling fluidized bed using discrete particle method”, Chem. Eng. Sci., 160, 106 (2017).

[12]  Chen, X. and Wang, J., “A comparison of two-fluid model, dense discrete particle model and CFD-DEM method for modeling impinging gas–solid flows”, Powder Technol., 254, 94 (2014).

[13]  Herzog, N., Schreiber, M., Egbers, C. and Krautz, H. J., “A comparative study of different CFD-codes for numerical simulation of gas–solid fluidized bed hydrodynamics”, Comput. Chem. Eng., 39, 41 (2012).

[14]  Huilin, L., Yurong, H., Gidaspow, D., Lidan, Y. and Yukun, Q., “Size segregation of binary mixture of solids in bubbling fluidized beds”, Powder Technol., 134, 86 (2003).

[15]  Gidaspow, D., Multiphase flow and fluidization: Continuu and kinetic theory descriptions, Academic Press, (1994).

[16]  Cooper, S. and Coronella, C. J., “CFD simulations of particle mixing in a binary fluidized bed”, Powder Technol., 151, 27 (2005).

[17]  Huilin, L., Yunhua, Z., Ding, J., Gidaspow, D. and Wei, L., “Investigation of mixing/segregation of mixture particles in gas–solid fluidized beds”, Chem. Eng. Sci., 62, 301 (2007).

[18]  Azizi, S., Hosseini, S. H., Ahmadi, G. and Moraveji, M., “Numerical simulation of particle segregation in bubbling gas-fluidized beds”, Chem. Eng. Technol., 33, 421 (2010).

[19]  Chao, Z., Wang, Y., Jakobsen, J. P., Fernandino, M. and Jakobsen, H. A., “Multi-fluid modeling of density segregation in a dense binary fluidized bed”, Particuology, 10, 62 (2012).

[20]  Formisani, B., Girimonte, R. and Longo, T., “The fluidization pattern of density-segregating binary mixtures”, Chem. Eng. Res. Des., 86, 344 (2008).

[21]  Geng, S., Jia, Z., Zhan, J., Liu, X. and Xu, G., “CFD modeling the hydrodynamics of binary particle mixture in pseudo-2D bubbling fluidized bed: Effect of model parameters”, Powder Technol., 302, 384 (2016).

[22]  Feng, Y. Q., Xu, B. H., Zhang, S. J., Yu, A. B. and Zulli, P., “Discrete particle simulation of gas fluidization of particle mixtures”, AIChE J., 50, 1713 (2004).

[23]  Norouzi, H. R., Mostoufi, N. and Sotudeh-Gharebagh, R., “Effect of fines on segregation of binary mixtures in gas–solid fluidized beds”, Powder Technol., 225, 7 (2012).

[24]  Schaafsma, S. H., Marx, T. and Hoffmann, A. C, “Investigation of the particle flowpattern and segregation in tapered fluidized bed granulators”, Chem. Eng. Sci., 61, 4467 (2006).

[25]  Zhang, Y., Zhong, W., Jin, B. and Xiao, R., “Mixing and segregation behavior in a spout-fluid bed: Effect of particle size”, Ind. Eng. Chem. Res., 51, 14247 (2012).

[26]  Santos, K. G., Francisquetti, M. C. C., Malagoni, R. A. and Barrozo, M. A. S., “Fluid dynamic behavior in a spouted bed with binary mixtures differing in size”, Dry. Technol., 33, 1746 (2015).

[27]  Johnson, P. C. and Jackson, R., “Frictional–collisional constitutive relations for granular materials, with application to plane shearing”, J. Fluid Mech., 176, 67 (1987).

[28]  Li, T., Grace, J. and Bi, X., “Study of wall boundary condition in numerical simulations of bubbling fluidized beds”, Powder Technol., 203, 447 (2010).

[29]  Bahramian, A., Olazar, M. and Ahmadi, G., “Effect of slip boundary conditions on the simulation of microparticle velocity fields in a conical fluidized bed”, AIChE J., 59, 4502 (2013).

[30]  Zhang, Y., Zhao, Y., Lu, L., Ge, W., Wang, J. and Duan, C., “Assessment of polydisperse drag models for the size segregation in a bubbling fluidized bed using discrete particle method”, Chem. Eng. Sci., 160, 106 (2017).

[31]  Lun, C. K. K., Savage, S. B., Jeffrey, D. J. and Chepurniy, N., “Kinetic theories for granular flow: Inelastic particles in Couette flow and slightly inelastic particles in a general flowfield”, J. Fluid Mech., 140, 223 (1984).

[32]  Schaeffer, D. G., “Instability in the evolution equations describing incompressible granular flow”, J. Differ. Equ., 66, 19 (1987).