Investigation of flat bottomed spouted bed with multiple jets using DEM–CFD framework

• Critical analysis of flat bottomed spouted bed with varying jets has been performed
• Important bed characteristics have been validated with in-house experiments
• Mixing and solid circulation in the bed have been investigated using a new method
• The results aim at improving the design and operation of spouted beds

Discrete Element Modeling (DEM) coupled with Computational Fluid Dynamics (CFD) has been used in the present study to simulate flat bottomed rectangular spouted bed with two-dimensional jets. Particle diameter of 550 μm has been investigated with single, double and triple jets, respectively, at superficial velocities of 1.6 and 3.0 times the minimum fluidization velocity. The results are validated with experimental measurements of time-averaged void fraction distribution, expanded bed height, and pressure drop. The general trends compare well with the experiments showing the potential of particle scale modeling in predicting jet dynamics and the interaction of multiple jets. Bed properties such as time averaged particle velocities, and granular temperatures are analyzed in detail. The particle velocity vectors show two distinct counter rotating vortical structures in the bed which aid mixing. In a single jet configuration, the granular temperature is highest in the jet core, whereas it is higher in the annular region for multiple jets as a result of the stronger vortices. Different measures of mixing are evaluated based on the solid horizontal flux entrained into the jet, the bed-averaged counter-current model and bed-averaged solid convection and diffusion. While solid velocity vectors and the horizontal fluxes indicate better mixing with multiple jet configurations, the counter-current model and the convection-diffusion model indicate superior overall mixing with a single central jet.

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