(310d) Granular Segregation In Rotating Cylinders

Segregation is a phenomenon that has long been recognized as the cause of several problems in materials handling and processing industries. The segregation of particles during the handling of bulk solids can have a detrimental effect on the quality of products in industrial processes. Rotating cylinders are commonly used in the chemical and process industries as kilns, mixers, dryers, reactors, and granulators to process granular materials. Good cross-sectional mixing in the cylinders is important for product quality and efficient operation in terms of energy usage for continuous flow systems. Granular mixtures of particles with different properties (e.g., size, density or both) tend to spontaneously demix and form segregated regions. Neither the experiments nor the models have yet proved universal enough to describe all the mechanisms that cause segregation in shear flow. The flow of granular materials in most industrial situations is very complicated. There is a great need for experiments, simulation and mathematical modeling that give quantitative results of the evolution of segregation. The dynamics of granular segregation are not well understood yet, hence the basis of design of solid mixers is in ad hoc. Experimental technique and results of granular segregation for binary mixtures will be discussed. A mathematical model for segregation will be presented. Results of granular segregation for ternary mixtures will be discussed.