Selection of Flow Aids: Model-based Prediction of Flow Properties Enhancements

Publication Reference: 
Author Last Name: 
Rajesh N. Davé
Report Type: 
ARR - Annual Report
Research Area: 
Powder Flow
Publication Year: 
United States

This annual report presents key advances made during year 2 of which, a major component is a concise treatise on our key advances in model-guided dry coating-based enhancements of poor flow and packing of fine cohesive powders, included in Appendix A. The report also includes a review of the available particle contact models for both smooth and rough particles and presents a database of industry relevant materials and their key properties. In terms of IFPRI Member interactions, we have held regular update meetings and worked with a member company on their powder characterization device. We plan to prepare a manuscript on that and include that in the report next year.

Major accomplishments include a review of the existing van der Waals force-based particle contact models to elucidate the main mechanism of flow enhancement through silica dry coating. Our multi-asperity model explains the effect of the amount of silica, insufficient flowability enhancements through conventional blending, and the predominant effect of particle surface roughness on cohesion reduction. Models are presented for the determination of the amount and type of guest particles, and estimation of the granular Bond number, used for cohesion nondimensionalization, based on particle size, particle density, asperity size, surface

area coverage, and dispersive surface energy. Selection of the processing conditions for LabRAM, a benchmarking device, is presented followed by key examples of enhancements of flow, packing, agglomeration, and dissolution through the dry coating. Powder agglomeration is shown as a screening indicator of powder flowability (Appendix B). The mixing synergy is identified as a cause for enhanced blend flowability with a minor dry coated constituent at silica <0.01%. The analysis and outcomes presented in this paper are intended to demonstrate the importance of dry coating as an essential tool for industry practitioners.