(53a) Eulerian Simulations of the Bubbling Dynamics of Binary Mixtures in Pseudo-2D and 3D Gas-Solid Fluidized Beds | AIChE

(53a) Eulerian Simulations of the Bubbling Dynamics of Binary Mixtures in Pseudo-2D and 3D Gas-Solid Fluidized Beds


Bates, R. B. - Presenter, Massachusetts Institute of Technology
Altantzis, C., National Energy Technology Laboratory
Ghoniem, A., Massachusetts Institute of Technology

Fluidized bed reactors are utilized in a variety of industrial processes including fluid catalytic cracking (FCC), coal/biomass gasification and combustion, and chemical looping combustion (CLC).  Most existing experimental and modeling studies of the bubbling behavior of gas solid fludized beds deal with monodispersed particles; however, in industrial practice cases this is rarely the case.  During the fluidization of poly or bidisperse powders with size and/or density differences, mixing induced by bubble motion counteracts the segregation of lighter, smaller particles (flotsam) above the heavier, larger particles (jetsam). Thus the size, velocity and distribution of bubbles within the bed are crucial to achieving satisfactory gas-solid and solid-solid mixing1.  While several experimental works from the literature examine the effect of bidispersity on global hydrodynamic characteristics3 and mixing/segregation4, few have analyzed the effect of bidispersity on the bubble behavior. 

In this work, 2D and 3D Eulerian simulations of the fluidization of bidisperse powder mixtures was performed. Powder mixtures of varying size, density, and composition were simulated at a range of inlet superficial gas velocities.  Subsequently, digital image analysis (DIA) techniques were then used to extract relevant bubble statistics. These statistics are compared with a systematic experimental study of bidisperse powder bubble dynamics by Busciglio et al. 20055.  By performing both 2D and 3D fine grid simulations, the effect of the walls on the bubble coalescence and splitting is clearly identified.

Sources cited:

1. Shen, L., Zhang, M. & Xu, Y. Solids mixing in fluidized beds. Powder Technol. 84,207–212 (1995).

2. Rao, T. & Bheemarasetti, J. . Minimum fluidization velocities of mixtures of biomass and sands. Energy 26,633–644 (2001).

3. Noda, K., Uchida, S., Makino, T. & Kamo, H. Minimum fluidization velocity of binary mixture of particles with large size ratio. Powder Technol. 46,149–154 (1986).

4. Goldschmidt, M. J. V., Link, J. M., Mellema, S. & Kuipers, J. A. M. Digital image analysis measurements of bed expansion and segregation dynamics in dense gas-fluidised beds. Powder Technol. 138,135–159 (2003).

5. Busciglio, A., Vella, G. & Micale, G. On the bubbling dynamics of binary mixtures of powders in 2D gas-solid fluidized beds. Powder Technol. 231, 21–34 (2012).