(407h) Small Particles Caught Between a Rough Spot and a Sticky Situation

Particles belonging to Geldart Groups A and C behave differently than their larger-sized counterparts.  These differences, including fluidization quality, minimum fluidization velocity, and bed expansion, are well known to be linked to the non-negligible contribution of van der Waals forces.  Nonetheless, model predictions for these flows have been lacking in their quantitative ability when compared to existing experimental data.  In this work, we use AFM and SEM to image particle surfaces.  The surfaces are characterized by a range of roughness levels spanning a full order of magnitude.  These roughness measurements are used as input to a variety of cohesive models.  These cohesion models are sequentially incorporated into DEM simulations of a fluidized bed, and compared directly to fluidization measurements of the same particles.  The results illustrate the large sensitivity of a given model to roughness levels as well as model-to-model differences, and also points to the need for detailed surface measurements (microscopic) when reporting fluidization data (macroscopic) involving cohesive particles.