EFFECTS OF PULPSTONE GRITS IN WOOD GRINDING .3. 2-SIZE GRIT MIXTURE (VARIOUS SIZES)

Pulpstones with a two-size grit mixture (constant proportions of large and small grits) are compared. The aim is to study how varying the amplitude of grinding frequency affects the specific energy requirement and properties of the groundwood pulps produced. Four concrete pulpstones with 30% large and 70% small aluminium oxide grits were manufactured. The sizes of the large and small grits were varied. A 60 mesh concrete pulpstone with normal grit distribution, a concrete pulpstone with 30% 36 mesh and 70% 60 mesh grits and a regular 60 mesh ceramic pulpstone were used as references. The grinding experiments were performed in a laboratory pressure grinder. The results show that energy is utilized more efficiently when the pulpstones consist of two-size grit mixtures. A smaller grit size results in a higher production rate, lower specific energy requirement and better optical properties, while a larger grit size produces larger long fibre fractions, better sheet densities and better strength properties.