Dry pelletization of kaolin

Abstract

Nominally dry kaolin powder was pelletized without the addition of seeds in a laboratory-scale batch granulation drum. The effects of relative humidity, drum speed and size of nuclei precursors, formed by sieving the clay through screens of different mesh openings, were studied. The pellets grew in size primarily by abrasion transfer of clay particles and clusters from one granule to another as they rolled past each other in the rotating charge, with perhaps some contribution also from the crushing and layering mechanism of growth. The rate of growth of the pellets was retarded significantly when the powder was equilibrated and pelletized in high relative humidity. With faster drum speeds as well as with larger size of the nuclei precursors, the rate of growth was observed to increase. Size distributions of the granules were log-normal, in conformity with a simple stochastic model of the kinetics of dry pelletization.