Experimental and numerical study of fluidization and pressure drop of spherical and non-spherical particles in a model scale fluidized bed

A laboratory scale fluidized bed was examined experimentally and numerically involving differently sized wooden Geldart-D particle shapes. Simulations were performed with a coupled DEM-CFD approach, which involves a drag force model that realizes for the particle shape and orientation. To validate the drag force model and to learn more about the fluidization behavior of non-spherical particles the pressure drop, particle height and orientation distributions were analyzed. To gain comparable data from the experiments, a PTV-MATLAB script was developed to detect particles and determine their orientations and heights. Experimental and numerical results are in good agreement for most particle types; differences in the pressure drop can be allocated to mismatching particle heights or orientations. Differences in the particle height distribution are a result of particles that stack up in corners or close to the vessel walls. It was found that despite these local deviations the DEM-CFD can accurately reproduce the orientation behavior of elongated particles, which with increasing velocity align themselves with the flow. For elongated particles below a certain elongation ratio this behavior could not be observed, which was confirmed by both experiments and simulations. (C) 2015 Published by Elsevier B.V.