Particle Engineering Research Center

PI: Kerry Johanson

Our current research addresses key problems of cohesive powder flows. Pharmaceutical, food, and nutraceutical industries must produce consistent products which are often a mixture of cohesive and non-cohesive materials of varying particle size. Blending is a primary unit operation. However, blender scale-up is currently impossible. Scale-up requires separating the influence of material properties from that of blender geometry and operation mode. The key to predictive capability is to determine the influence of material properties on local velocity profiles, and the relationship between velocity profile and blender residence time distribution functions. Current research focuses on unraveling these relationships.

Pharmaceuticals and foods tend to gain cohesive strength when stored, resulting in extensive flow problems during handling. These problems cause significant unscheduled process/plant downtimes. Current research includes determining key relationships between cohesive powder behavior and particle scale events such as caking (growth of crystalline structures between particles) or cohesive strength caused by capillary and van der Waal's forces between particles.

Our research scope extends to determining the coherence length of bulk solid materials as they shear. This work examines how the structure of bulk mixtures may affect bulk properties. The goal is to build a link between bulk behavior, powder structure, and the inter-particle forces that can be controlled by modifying surface characteristics.

Selected Publication

1. Encapsulated and Powdered Foods, by Kerry Johanson, Taylor and Francis, Edited by Charles Onwulata, Chapter 13, Edited by Charles Onwulata, 331- 364 (2005).
2. "Qualitative measurement of particle segregation mechanisms", by Kerry Johanson, Chris Eckert, Dev Ghose, Millorad Djomlija, and Mario Hubert, Powder Technology (to appear, 2005).
3. "Rathole Stability Analysis for Aerated Powder Materials, Kerry Johanson, Powder Technology, Vol. 141/1-2, 161-170, (2004)
4. "Stress Homogeneity in Powder Specimens Tested in the Jenike Shear Cell: Myth or Fact?", by E. Bilgili, J. Yepes, L. Stephenson, Kerry Johanson, and Brian Scarlett, Part. Part. Syst. Charact., Vol. 21, 293 – 302 (2004)
5. "Measurement of k-values in diamondback hoppers using pressure sensitive pads", by Kerry Johanson, and Ray Bucklin, Powder Technology, Vol. 140 /1-2, 122-130 (2004).
6. "The Influence of Air Counter-Flow Through Powder Materials as a Means of Reducing Cohesive Flow Problems", by Kerry Johanson and Diego Barletta, Part. Part. Syst. Charact., Vol. 21, 316 – 325 (2004).
7. "Relationship Between Capillary Force and Bulk Unconfined Yield Strength", by K. Johanson, Y. Rabinovich, B. Moudgil, K. Breece, H. Taylor, Powder Technology, Vol. 138, 13-17 (2003).