462464 Effect of Friction and Restitution Coefficient on Defluidization and Riser Flows of Cohesive Particles

Monday, November 14, 2016: 1:57 PM
Peninsula (Hotel Nikko San Francisco)
Peiyuan Liu, Casey Q. LaMarche, Kevin M. Kellogg and Christine M. Hrenya, Chemical and Biological Engineering, University of Colorado at Boulder, Boulder, CO

Fluidized beds and risers are typical systems for dense and dilute gas-solid flows with broad industrial application. Friction and restitution coefficient, as two major sources of energy dissipation, have significant impact on gas-solid flows of non-cohesive particles. The interplay of friction and restitution coefficient with particle cohesion, however, requires further investigation. In this work, we focus on behavior of cohesive particles in terms of defluidization curves in fluidized beds and agglomerate properties in riser flows. Based on the DEM-CFD simulations, a reverse dependence on sliding friction and restitution coefficient was identified: defluidization curves were more influenced by sliding friction while agglomerates in risers were governed by restitution coefficient. By analyzing bed porosity and particle velocities, the reverse sensitivity is understood by the switch of primary particle interactions from lasting contacts to binary collisions between the two systems. A non-monotonic response of increasing sliding friction on defluidization curves was observed, which can be explained by the competing effects of increased slipping and enhanced particle spin on bed porosity. The results suggest the complexity of the continuum modeling for gas-solid flows can be tuned provided the leading factor in the system of interest is properly incorporated. The data provided in this work can also be used in validating continuum model predictions.

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