Effect of particle shape on settling characteristics

Abstract

Settling is the process by which particulates settle to the bottom of a liquid and form sediment. This process is used in various industries i.e.; mining, waste water treatment, removal of slurry, catalytic reactors, food processing, particle mechanics. The settling velocity is dependent upon particle size, the shape (roundness and sphericity) and density of the particles, as well as to the viscosity and density of the fluid. To observe the effect of particle shape on settling velocity experiments are carried out with particles of same density with different shapes (cubic, spherical, cuboid, triangular, and trapezoidal). Water, paraffin oil and kerosene are used as the medium. Settling velocities are also estimated in free and hindered settling environments. From the experiment it is observed that the settling velocity depends on the shape factor of the particle. Settling velocity of the particle increases nonlinearly with time. The rate of settling depends on the settling medium and also the mode of settling. Settling velocities against time are plotted for individual shape and observed that in each case the slope and intercept are changing. In other words it implies that settlings velocity is a strong function of their respective shapes.