(303e) Single Blade Experiments On Granular Flow and Mixing

Authors: 
Radl, S. - Presenter, Graz University of Technology
Brandl, D. - Presenter, Graz University of Technology
Heimburg, H. - Presenter, Graz University of Technology
Khinast, J. - Presenter, Research Center Pharmaceutical Engineering GmbH
Glasser, B. - Presenter, Rutgers University


Granular flow, mixing and segregation in bladed mixer has been studied by various researchers for free flowing and cohesive materials [1]. However, there has been no detailed study on the isolated effect of a single blade on granular flow and mixing. We present a new two-dimensional experimental setup to investigate granular flow as well as particle mixing over a single blade. Different blade angles, bed heights and blade positions were studied. Instantaneous velocity fields were recorded using granular particle image velocimetry. Time-averaged as well as fluctuating velocity fields were calculated from the data. The mixing process was analyzed by using colored particles and diffusive mixing was quantified using the color intensity distribution over the bed height. The particles used were spherical glass beads with a size ranging from 0.5 mm to 4 mm. Wet and dry granular matter was studied. The bulk solids where characterized via measurements of the friction coefficient, the normal coefficient of restitution as well as the bulk rheology. The results revealed new flow features in the cross section of bladed mixers that have not been shown in our previous work [2]. For example, the thickness of the shear layer in front of the blade (see Figure) was quantified. Also, we could detect clear differences in the flow and mixing behavior depending on moisture content and bed height. This is essential for the rational design or optimization of granular mixing instruments. References [1] Radl, S., Kalvoda, E., Glasser, B.J., Khinast, J.G., 2010. Mixing Characteristics of Wet Granular Matter in a Bladed Mixer. Powder Technology 200, 171-189. [2] Lekhal, A., Conway, S.L., Glasser,B.J., Khinast,J.G, 2006. Characterization of granular flow of wet solids in a bladed mixer. AIChE Journal 52, 2757 - 2766.