(663e) Mixing and Segregation in Multi Components Granular Mixtures in Rotating Cylinders

Powder mixtures are widely used in process industries such as cement, fertilizers, chemicals, pharmaceuticals and agriculture. Blending, heating, and granulation of these materials are commonly carried out in rotating cylinders. However, when mixtures of different types of particles are rotated in a cylinder they tend to spontaneously separate into regions rich in one or other species of the mixture. We carry out an experimental study of the equilibrium segregation of multi components granular mixtures in a rotating cylinder. The cylinder is half-full of the granular mixture and rotational speed used ensures operation in the rolling regime of flow. Mixtures of spherical particles differing only in size and of spherical particles differing in size and density are considered, using steel balls and glass beads of different sizes. Volume fraction profiles of the components are measured by means of sampling. Results for mixtures differing only in size of the components indicate that the segregation process is controlled by the size of the smallest particles and is nearly independent of the sizes of the large and middle size particles. In the case of mixtures with different size and density components, the segregation patterns depend on the direction of the resultant driving force. We also study mixing and segregation in rotating cylinders for binary mixtures of particles of different size and density. When small particles in the mixture are denser then complete segregation and radial streaks are noticed. For same size ratio mixtures, streak formation depends on the size of the small particles.