2020 Virtual AIChE Annual Meeting

(84e) Comparing Dynamic and Quasi-Static Powder Flow Testing Methods

Authors

Lumay, G. - Presenter, University of Liege
Shi, H., Multi Scale Mechanics (MSM), Faculty of Engineering Technology (ET), MESA+, University of Twente
Luding, S., University of Twente
Granular materials are ubiquitous in our daily life. A special class of them is cohesive powders consisting of fine particles that may flow when shaken or tilted, but could cake when left at rest or being compressed during storage.

In order to measure the complex flow properties of these powders, a variety of characterization techniques have been proposed: the angle of repose, the tapped density, the dynamic rotating drum, rotating blade systems or shear testing procedure. These techniques are based on different geometries with very different flow fields under different confining stresses, and make the cross link between them non-trivial. In this study, we attempt to bridge the gap between the static angle of repose test (GranuHeap), the dynamic rotating drum measurement (GranuDrum), the quasi-static packing dynamics measurement (GranuPack) [1] and the quasi-static ring shear test (RST-01) using both free flowing and cohesive limestone powders. Starting from the dynamic flowing angle in the rotating drum and going slower, one can extrapolate to the limit of zero rotation rate and compare it with the repose angle. Moreover, when stretching the ring shear test to its lowest confining stress limit, the bulk friction angle coincides with the drum flowing angle in the zero rotation rate limit [2]. Moreover, the analysis of packing dynamics gives additional insight on the powder behaviour.

This connection between different tests opens new perspectives in the field of powder flow characterization for measurement interpretation and also for a better link with powder behaviour in industrial process lines.

[1] Measuring the flowing properties of powders and grains, Powder Technology 224, 19–27 (2012)

[2] Stretching the limits of dynamic and quasi-static flow testing on cohesive limestone powders, H. Shi, G. Lumay, & Stefan Luding, Powder Technology 367, 183–191 (2020)