When forces are involved that are statical or are present as a consequence of
movements (dynamic forces), handling of cooled pellets causes attrition. Static forces
for example may occur during bin storage while dynamic forces are present during
screw or pneumatic transportation or during the filling of a bin. Attrition of feed pellets
comprises two phenomena, fragmentation and abrasion, both of which have consequences
for its particle size distribution (Fig. 2) and bulk density.
Fragmentation involves the fracture of pellets into smaller particles and fines at the
fracture area. Fragmentation causes a small shift in the particle size distribution but will
cause only a limited increase in bulk density or specific surface (de Jong, 1993). The
stresses required to overcome the cohesive and adhesive forces in the cracktip and the
amount of energy necessary, is dependent on the direction of the applied stresses, length