Dry grinding of armutçuk coal in a pin-type vertical stirred mill and the effect of bead size on product fineness

In this study, dry grinding of Armutçuk coal (d50∼1 mm) was investigated in a laboratory-scale, pin-type vertical stirred mill. Grinding experiments were carried out with various diameter steel beads (6.5, 5.5, 4.5, 3.5 mm) at various grinding times (2.5, 5, 10, 20, 40, 60, 120, 240 s). Then, the results were plotted to see the effect of grinding time and bead size on the product fineness. The results showed that the median sizes (d 50) of the products became finer (19, 18, 16, 11 μm) as the bead sizes decreased (6.5, 5.5,4.5, 3.5 mm) in 60 s grinding time. The efficiency of the stirred mill reduced dramatically after the 60 s grinding time and the fine particles were hardly ground after the 120 s grinding time.