Fluidized bed dynamics

Understanding basic hydrodynamics of a fluidized bed system is a key factor for the design and optimization of fluidized bed reactors. One of the main research topics of the ISE group is to study fluidized bed dynamics. To that aim, the group employes two fronts, experiments and simulations.

Regarding the experimental characterization of fluidized bed systems, the group uses lab scale facilities of 2D and 3D fluidized beds. On the one hand, 2D or pseudo-2D beds, typically have a transparent wall, in order to allow optical access to the system, and possess a small thickness to ensure that the visualization is representative of the whole system, so that, visual inspection or image acquisition can be performed from the front view of the bed to study its behaviour. Therefore, Digital Image Analysis (DIA) or Particle Image Velocimetry (PIV) can be applied to that images. On the other hand, the ISE research group posses several cylindrical 3D units prepared to work under hot or cold conditions.

Numerical modelling of fluidized beds has advance significantly over the last decades due to the significant enhancement and development of computational systems. Four main approaches can be found in the literature for the simulation of fluidized beds depending on the level of detail and resolution required.

  • The most detailed approach is the direct numerical simulation (DNS) of the fluid flow surrounding solid particles and the interaction between them.

  • Particle or discrete element modelling (DEM) is based on a Lagrangian simulation of each particle trajectory coupled with the Eulerian simulation of the bulk gas flow.

  • In the Euler-Euler of two-fluid model (TFM) approach, the gas phase and the particles or solids phase are treated as two interpenetrating and continuum media in an Eulerian framework using the conservation equations of fluids.

  • Finally, in the discrete bubble models (DBM) and phenomenological methods only the most relevant macroscopic characteristics of the bed are reproduced.

  • ISE research group basically employes TFM and DEM simulations of fluidized bed systems due its compromise between level of detail of the solution and computational cost. Or even, combining them to model the different solids phases either as continuum or discrete.

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