The grate ball mill is usually used in the first segment of the two stages to discharge the rough ore. The grate ball mill is roughly consist of the cylinder, cylinder liner,big gear ring, discharging grate, and ore feeding device. There is a discharging grate plate installed at the discharging end. In the head cover of the hollow shaft of the discharging end, it has bearing inner cover and discharging grate installed and the later is made from central liner, grate liner and dustpan liner etc. There are eight radial rib casted on the inner wall of the head cover, which divide the head cover into 8 fan rooms. Each room is installed dustpan liner, with the bolt fixed on the end cover. The grate liner can be divided into two kinds of structure: one is formed by two pcs, pressed by the wedge block, which get fixed tightly on head cover with the bolt getting through the rib. The central part are supported by the central liner to prevent them from declining and dropping off. The other kind gets two pcs into one block, fixing with bolt directly. The central liner is star shape, formed by two block, tightened on the rib with the bolt.

The hole on the grate liner depends on inclining direction. The width of the hole is gradually getting bigger to the discharging end, which can prevent the slurry from regorging and rough granularity from blocking. The slurry flow into the fan shape room through the hole on the grate plate from the lower part of the discharging end, and get up to the upper part along the cylinder rotating and discharged off the hole path. The hollow shaft neck has the grinding proof inner cover, with one end made of trumpet shape blade to lead the slurry to flow out of the mill.
   
In this kind of mill the slurry is discharged through the grate plate, it is called the grate ball mill.

grate ball mill Characteristics and advantages
1. Fast discharging speed
2.high production capacity
3.High production capacity
4.Powers saving
5.Less overgrinding phenomena--discharging at the lower horizontal level
6.Less slurry stored inside -- easy to discharge the grinded fine particles in time
7.Much ball loading