Ball Grinding Mill
Six classified ways of ball mill.
1.Classification according to the impact
2.Classification according to the length
(1)Short mill: It is called short mill or ball mill when the L/D is under 2. A common mill with a single chamber is used in coarse grinding or primary grinding. Furthermore, two to three ball mills can be used in tandem.
(2)Medium mill: It can be called medium mill when the L/D is about 3.
(3)Long mill: It is called long mill or tube mill when the L/D id above 4. The inside of the medium mill or long mill is pided into two to four chambers, which is widely used in the cement plant.
3.Classification according to the shape of the grinding medium
(1)Ball mill: The grinding mediums are mainly steel balls and steel segment, this type of mill is most commonly used.
(2)Rod mill: The grinding medium put into the mill is the steel bar whose diameter is between 50mm and 110mm. The L/D of the rod mill is generally between 1.5mm and 2mm.
(3)Ball rod mill: This kind of mill usually has two to four chambers, the first chamber is installed cylindrical steel bars as grinding medium, the others are installed with steel balls or steel segment.
The L/D of this mill should be five, the ratio of the length of the bar chamber and the effective diameter of the mill ought to be between 1.2 to 1.5, the bar length is 100mm shorter than the bar chamber beneficial to parallel arrangement and to avoid crossover and disorderly stick.
(4)Gravel grinding mill: The grinding medium inside the mill are gravel, pebbles and ceramic balls. It uses granite and ceramic materials as the liner. It is applied in the production of the white or color cement and ceram.
4.Classification according to discharging methods
(1)Tail discharge type: grinding materials are fed from one end of the mill then discharged from the other end.
(2)Middle discharge type: grinding materials are fed from the two ends and then discharged from the middle. This kind of mill equals to two ball mills used in parallel, which enables equipment to be more compact and simplifies the process.
(3)Head discharge type: According to discharging methods, it can be pided into numerous types like grate mill, overflow discharging mill, peripheral discharging mill as well as wind discharging mill.
5.Classification according to transmission
(1)Center drive mill: The motor drives the mill to rotate by driving the hollow shaft of the mill discharging end through the reducer. The shaft extension of the reducer and the centre line of the mill are in the same straight line.
(2)Edge drive mill: The motor drives the mill’s cylinder to rotate through driving the big gear fixed in the discharge cylinder by the reducer.
According to the craft, it can be pided into dry mill, wet mill, intermittent mill and continuous mill as well. Compared with the intermittent mill, the continuous one is of high yield, the current consumption per unit weight of product is low, the mechanization degree is high and the number of the operators is small. However, the investment cost of the infrastructure is big and the operation and maintenance are complicated. At present, the intermittent mill is rarely used but often applied in lab test grinding.