Interaction of energy input and bead abrasion during comminution of alumina in attrition mills

The quality of milling product is determined by size distribution and contaminations, resulting from particle-bead contact (mass and size of bead abrasion) and particle - wall contact. Increase of energy in bead mills will decrease the milling time but increase the bead attrition. This interaction was investigated by comminution of an aqueous alumina suspension (d90 = 4.5 µm) in a laboratory attrition mill (AHM90, Hosokawa Alpine AG) under different conditions. Based on preliminary tests with zirconia beads (0.2 / 0.5 / 1 mm) the technological parameter range for an experimental plan (DoE) was selected: - volume flux (0.75 - 1.5 l/min) - volume ratio of bead (60 - 80 vol%) - rotation speed of milling discs (1600 - 3000 rpm). The results indicate the large influence of bead diameter on milling kinetics and on bead abrasion. With constant specific energy input of about 0.75 kWh/kg particle sizes of about d90 = 2.6 µm were realized. The first analysis of DoE-results demonstrates, that especially contamination sensitive hard material require optimized balance between energy input and bead related abrasion.