Fluidized Segregation of a Bidisperse Particulate Mixture in a Nonuniform Annular Geometry

An apparatus is designed and fabricated for conducting experiments concerning fluidized segregation to verify a proposed design concept for a more efficient comminution machine. Previous studies have found that the fines distribute the intended crushing load imposed by the machine on the particle bed; thus, the load that must be applied to crush the larger particles increases. By removing the fines as they are produced, smaller loads may be applied to achieve crushing. The proposed design incorporates size-dependent material transport and comminution into a single, continuous process. This integration can provide increased comminution efficiency by removing the fines as soon as they are produced. To effect removal of the fines, fluidization will be employed. An upward water jet will carry away only particles that are smaller than a threshold size, which is controlled by the velocity of the fluid. In order to implement the above concepts, a machine design has been proposed. The design features a nonuniform annular gap, which is the space between two cylinders. The inner cylinder revolves around its own axis, which in turn revolves about the axis of the outer cylinder. The resulting geometry is a gap that appears to converge and diverge in time, when viewed from any fixed point on the cylinder. The converging-diverging motion of the walls will provide the motion necessary for comminution, and the cylindrical implementation will allow a the machine to operate continuously. An apparatus has been designed and constructed to conduct experiments that will determine the efficacy of fluidized segregation in the nonuniform annular geometry under simulated crushing conditions. The device simulates the kinematic behavior of the proposed concept and provides facilities for observation and data acquisition. In addition, a set of experiments has been designed to explore the operating space of the apparatus. Data acquired from the apparatus is to be captured on SVHS videotape, from which it is post-digitized and analyzed with computer image analysis tools. Thesis Supervisor: Carl R. Peterson Title: Professor of Mechanical Engineering