(238e) Rate-Based Separation In Collisional Particle Flows

Separation of particles is extremely important in a number of industries involved in the handling of solids. Rate-based separation processes hold promise as both more environmentally benign as well as less energy intensive as convention particle separations technologies. This approach is based on differences in the kinetic properties of the components of a mixture, such as the velocity of migration in a medium or diffusivity. In this work, two examples of novel rate-based separation devices will be demonstrated. The first example will analyze a ratchet mechanism where a directed current of particles can be produced in a direction perpendicular to the direction of energy input. In this setup, a vibrating saw-toothed base is employed to induce different mobility for different types of particles. The effect of different operating conditions and design parameters on the separation efficiency will be discussed. The second rate-based separation example will involve the study of the dynamics of gravity-driven particles through an inclined chute fitted with an ordered array of obstacles normal to the chute surface. Dissipative collisions (both with the particles themselves and with the obstacles) give rise to a diffusive motion of particles perpendicular to the flow direction. The extent of separation (i.e., how far one type of particle is removed from another) depends on the different distances traversed by the two types of particles and equals <v₂> t - <v₁> t, where t is the time allowed for migration. Thus the extent of separation is directly proportional to the time of migration in the gravity field (i.e., time-dependent), a feature that distinguishes such separations from other separation techniques.