DEM Simulations of Fluidized Bed Using a Scaled Particle Approach

Fluidized beds are widely used in chemical process and refining industry due to various advantages they offer over fixed bed reactors. Nonetheless, their design is a difficult task and modeling is increasingly deployed to understand and scale-up these equipment. This paper reports the results for large-scale parallel simulations of fluidized bed using Discrete Element Method (DEM) fully coupled with fluid flow model using STAR-CCM+ software developed by CD-adapco. The simulation model uses the geometry and set-up as described in reference [1] and the simulation results are being compared with corresponding experimental results from the same reference.  In the numerical model, the particle's drag depends on local solid fraction with Ergun equation based drag used for dense regions and Wen-Yu drag model otherwise. A novel approach of scaling up the DEM particle's size with simultaneous scaling of drag coefficient is introduced and used. For each particle size scaling factor the drag scaling factor is obtained through parametric study by reproducing the fluidization conditions obtained in experiment. The scaling of drag law as a function of particle size scaling is discussed as well as the effect of scaling approach on simulation time and accuracy of numerical model.  Authors believe that this approach will be able to achieve a right balance between accuracy (a feature of DEM methods) and speed (a feature of computation particle approaches) to enable practical design and scale-up workflow.

[1]	J. X. Bouillard, R. W. Lyczkowski and D. Gidaspow, "Porosity Distributions in a Fluidized Bed with an Immersed Obstacle," AIChE Journal, vol. 35, no. 6, pp. 908-921, 1989.