Effect of fatty acid additives on the material flow properties of dry grinding

The effect of six fatty acid derivatives on dry grinding of calcite was investigated, for four additive concentrations and four grinding times under specified milling conditions, to follow their influence on the grinding process. Particle size distribution, bulk density, packed bulk density, compressibility and tensile strength of a powder bed of the ground product were measured to investigate their influence in enhancing the grinding process. The presence of a fatty acid additive increases the fineness, bulk density and packed bulk density of the ground product while decreasing the compressibility and tensile strength of a powder bed of the ground product. It is concluded that the alterations in these flow properties of the mill content in presence of an additive can be the reason for their enhancing effect in increasing the ultimate fineness of the ground product. In other words, adsorption of the long chain fatty acid molecules over the particle surfaces decreases the frictional forces and cohesive interactions between them and thereby alters the flow properties of the mill content during grinding, which in turn enhances the overall grinding process. © 1993.