CFD-DEM modelling of circulation frequencies and residence times in a prismatic spouted bed
Coupled CFD-DEM simulations of a three-dimensional prismatic spouted bed with liquid injection were performed. Spouting stability is investigated by means of pressure drop fluctuation analysis and high speed camera recording.
To determine the influence of flow stability on coating quality, droplets are injected in a post-processing step and deposited on colliding solid parcels.
In order to estimate liquid holdup in the bed, heat transfer and subsequent evaporation of the surface liquid film were modelled. The coating quality of different process conditions is compared for a simulation time of 10 s and found to be broader distributed in the dense stable spouting operating regime. The analysis of particle circulation frequencies shows slower circulation under stable spouting conditions, resulting in a slower coating progress.
This explains the inhomogeneous coating quality in the first 10 s for these cases. Nevertheless, the frequencies are less broadly distributed compared to the instable regime, which is advantageous for obtaining a homogeneous layer in real-time coating processes.
Keywords: Three-dimensional spouted bed, Liquid injection, Surface coverage, Circulation frequencies