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Ball mill is a key mineral processing equipment that used for grinding after the crushing stage. According to the different modes of ore discharging, the ball mill can be divided into grid type ball mill and overflow type ball mill. But do you know what are the similarities and differences between these two kinds of ball mill?
Let's take a look .
The structure of the grid type ball mill and overflow type ball mill is basically same, which is mainly composed of the cylindrical shell, feeding part, discharging part, bearing part, transmission part and lubrication system.
When the grid type ball mill and overflow type ball mill are working, the cylinder rotates around the horizontal axis at the specified speed. And the material falls down under the effects of the centrifugal force and friction force of grinding medium, then the grinding stage is finished, the grinding product is discharged through the ore discharging part.
Although the grid ball mill and overflow ball mill have the similar structure and grinding process, their ore discharging parts are totally different.
Grid type ball mill is equipped with grid lining board on the side of ore discharging (this is why it is named as the grid type ball mill) and an extra grid board at the discharging end, where a lot of discharging holes are on that. After the grinding stage, the pulp is lifted to the level higher than the ore discharge through the fan-shaped chamber leading to the ore discharging port, so that the pulp is discharged from the ball mill.
Overflow type ball mill is equipped with grid lining board on the side of ore discharging, but spiral blade that rotates opposite the rotating direction of ball mill, which is to prevent the water polo or coarse material ore from discharging with the pulp. The discharging mode of overflow type ball mill is self-overflow, namely the pulp is above the bottom edge of the journal bush of hollow shaft (that is why it is named as the overflow type ball mill).
The particle size of grid type ball mill is generally 0.2 ~ 0.3mm, so it is often used in the first stage of grinding, and often used as a closed loop with spiral classifier.
The particle size of overflow type ball mill is generally less than 0.2mm, which is suitable for concentrate re-grinding operation and easy to obtain qualified fine products.
The discharging mode of grid type ball mill is through the screen plate.
The discharging mode of overflow type ball mill is automatic overflow. When the material level is higher than the outlet, the overflow type ball mill discharges automatically.
The working characteristics of grid ball mill are forced discharge and high production capacity. It can used in the first stage of grinding operation and obtain higher processing capacity, but its product size is coarser than the overflow type ball mill.
Grid type ball mill is equipped with unique grid board and lift pot inside the fan room, which achieves low-level forced discharging. The qualified ore particles can be discharged timely, so the overgrinding phenomenon is greatly reduced.
Overflow type ball mill is non-forced high level discharging, so the discharging speed is slow and the material stays a long time on the overflow type ball mill, so its overgrinding phenomenon is serious than grid type ball mill.
In contrast, the overflow type ball mill is featured with simple structure and convenient maintenance,
While the grid type ball mill is complicated to repair because its grid board is easy to be blocked.
The above is the comparison between grid type ball mill and overflow type ball mill . Grid type ball mill and overflow type ball mill have their own characteristics in application and performance. When choosing the most suitable grinding equipment, please make clear your production requirements (such as rough or fine grinding) and output requirements.We recommend consulting the manufacturer to select the ball mill, choose the reasonable equipment suitable for the processing process, and ensure the production efficiency and economy of the processing plant.