Effect of Particle Size on Flow Behavior in Fluidized Beds

Effect of Particle Size on Flow Behavior in Fluidized Beds

Ramesh Timsina Rajan K. Thapa Britt M.E. Moldestad Marianne S. Eikeland

Department of Process, Energy and Environmental Technology, University of South-Eastern Norway, Kjølnes Ring 56, 3901, Porsgrunn, Norway

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The fluidization behaviour depends on particle properties such as particle size, sphericity, density and the properties of the fluidizing agent. In this study, the effects of different particle sizes on fluidization behaviour were investigated. Experiments were done by mixing sand particles of mean diameter 293µm (small particle) and 750 µm (large particle). The experiment with 20% small particles and 80% large particles gave a reduction in minimum fluidization velocity of 60.8% compared to the minimum fluidization velocity with only large particles. CPFD simulations were performed using the commercial software barracuda®. There is a good agreement between the results from the experiments and the simulations. The minimum fluidization velocity is also calculated using different theoretical equations based on the average particle size for the mixture. The obtained experimental results were compared with the minimum fluidization velocity calculated using different equations available in the literature. There are significant differences in minimum fluidization velocities obtained from the different empirical equations. The pressure drop profiles for large and small particles follow the trends presented in the literature. The experimental minimum fluidization velocities were found to be 0.46 and 0.092 m/s for the large and small particles respectively.


bubbling fluidized bed, fluidization, particle size


[1] Bandara, J.C., Moldestad, B.M. & Eikeland, M.S., Analysing the effect of temperature for steam fluidized-bed gasification of biomass with MP-PIC simulation. Journal homepage: www. IJEE. IEEFoundation. org, 9(6), pp. 529–542, 2018.

[2] Franco, C., Pinto, F., Gulyurtlu, I. & Cabrita, I., The study of reactions influencing the biomass steam gasification process☆. Fuel, 82(7), pp. 835–842, 2003. https://doi.org/10.1016/s0016-2361(02)00313-7

[3] Rowe, P. & Nienow, A.W., Minimum fluidisation velocity of multi-component particle mixtures. Chemical Engineering Science, 30(11), pp. 1365–1369, 1975. https://doi.org/10.1016/0009-2509(75)85066-4

[4] Noda, K., Uchida, S., Makino, T. & Kamo, H., Minimum fluidization velocity of binary mixture of particles with large size ratio. Powder Technology, 46(2–3), pp. 149–154. https://doi.org/10.1016/0032-5910(86)80021-3

[5] Jayarathna, C. & Halvorsen, B., Experimental and computational study of particle minimum fluidization velocity and bed expansion in a bubbling fluidized bed. in SIMS. 2009.

[6] Huilin, L., Yunhua, Z., Ding, J., Gidaspow, D. & Wei, L., Investigation of mixing/segregation of mixture particles in gas–solid fluidized beds. Chemical Engineering Science, 62(1–2), p. 301–317, 2007. https://doi.org/10.1016/j.ces.2006.08.031

[7] Oliveira, T., Cardoso, C. & Ataíde, C., Bubbling fluidization of biomass and sand binary mixtures: Minimum fluidization velocity and particle segregation. Chemical Engineering and Processing: Process Intensification, 72, pp. 113–121, 2013. https://doi.org/10.1016/j.cep.2013.06.010

[8] Pérez, N.P., Pedroso, D.T., Machin, E.B., Antunes, J.S., Ramos, R.A.V. & Silveira, J.L., Fluid dynamic study of mixtures of sugarcane bagasse and sand particles: Minimum fluidization velocity. Biomass and Bioenergy, 107, pp. 135–149, 2017. https://doi.org/10.1016/j.biombioe.2017.08.015

[9] Ramakers, B.J., De Ridder, R. & Kerkhof, P.J., Fluidization behavior of wood/sand mixtures. Maderas. Ciencia y tecnologia, 6(2), pp. 145–153, 2004. https://doi.org/10.4067/s0718221x2004000200005

[10] Paudel, B. & Feng, Z.G., Prediction of minimum fluidization velocity for binary mixtures of biomass and inert particles. Powder Technology, 237, pp. 134–140, 2013. https://doi.org/10.1016/j.powtec.2013.01.031

[11] Kunii, D. & Levenspiel, O., High-Velocity Fluidization. Fluidization Engineering, 193–210, Elsevier, 2013. https://doi.org/10.1016/b978-0-08-050664-7.50014-7

[12] Kunii, D. & Levenspiel, O., Circulating fluidized-bed reactors. Chemical Engineering Science, 52(15), pp. 2471–2482, 1997. https://doi.org/10.1016/s0009-2509(97)00066-3

[13] Cocco, R., Karri, S.R. & Knowlton, T., Introduction to fluidization. Chem. Eng. Prog, 110(11), pp. 21–29, 2014.

[14] Niven, R.K., Physical insight into the Ergun and Wen & Yu equations for fluid flow in packed and fluidised beds. Chemical Engineering Science, 57(3), pp. 527–534, 2002. https://doi.org/10.1016/s0009-2509(01)00371-2

[15] Wen, C. & Yu, Y., A generalized method for predicting the minimum fluidization velocity. AIChE Journal, 12(3), pp. 610–612, 1966. https://doi.org/10.1002/aic.690120343

[16] Richardson, J. & M.d.S. Jerónimo, Velocity-voidage relations for sedimentation and fluidisation. Chemical Engineering Science, 34(12), pp. 1419–1422, 1979. https://doi.org/10.1016/0009-2509(79)85167-2

[17] Doichev, K. & Akhmakov, N., Fluidisation of polydisperse systems. Chemical Engineering Science, 34(11), pp. 1357–1359, 1979. https://doi.org/10.1016/0009-2509(79)80032-9

[18] Lin, C.L., Wey, M.Y. & You, S.D., The effect of particle size distribution on minimum fluidization velocity at high temperature. Powder Technology, 126(3), pp. 297–301, 2002. https://doi.org/10.1016/s0032-5910(02)00074-8

[19] Ku, X., Li, T. & Løvås, T., CFD–DEM simulation of biomass gasification with steam in a fluidized bed reactor. Chemical Engineering Science, 122, pp. 270–283, 2015. https://doi.org/10.1016/j.ces.2014.08.045