(65a) Extraction of Parameters for a Square-Force Cohesion Model from Defluidization Experiments

Authors: 
Liu, P. - Presenter, University of Colorado at Boulder
LaMarche, C. Q., Particulate Solid Research, Inc.
Kellogg, K. M., University of Colorado at Boulder
Hrenya, C. M., University of Colorado at Boulder
Interparticle cohesion originating from van der Waals force and capillary force significantly impacts the flow behavior of particulate and multiphase systems. Though commonly seen in nature and industry, cohesive particles remain poorly understood, triggering continued interest from physicists and engineers. An accurate inter-particle cohesion model is key for improved understanding, though the development and validation of such models remains largely elusive. A key obstacle is the extreme sensitivity of the cohesive force to separation distance, and thus surface roughness. The precise measurement of surface roughness is time-consuming, requires specialized training, and involves expensive equipment such as atomic force microscopes (AFM). Such model development is often not conducive to applying to a wide range of materials and/or in an industrial setting. In previous work [LaMarche et al., Towards a universal description of cohesive-particle flows. (submitted)], we have shown that the behavior of cohesive-particle systems can be collapsed for either a dimensionless cohesive force or energy, depending on particle concentration. Accordingly, we propose a simplified cohesion model, the “square force” model, with only two parameters that capture both cohesive force and energy of more rigorous treatments. Perhaps most importantly, these two particle-particle (micro) parameters can be extracted directly from bulk (macro) measurements, namely defluidization curves. Specifically the incorporation of the extracted parameters into DEM simulations reproduces the results based on more rigorous cohesion models applied to both riser (gas-solid, dynamic and dilute) and hopper (granular, quasi-static and dense) systems. Access to such a practical method for developing reliable particle-particle cohesion models is a key step in bridging microscopic models to their continuum counterparts – e.g., population balances.