Seven Differences Between Grid Type Ball Mill and Overflow Type Ball Mill Teach You How to Choose?

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 differences between these two kinds of ball mill? And which one should you choose?

Common:

1. Similar structure

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.

2. Similar working process

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.

Difference

1. Structure of ore discharging part

Although the grid type ball mill and overflow type ball mill have the similar structure and grinding process, their structure of the ore discharging is 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).

2. Discharge size

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.

3. Discharging mode

The discharging mode of grid type ball mill is through the screen plate, and 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.

4. Production capacity

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.

5. Grinding effect

There are various sizes of steel ball inside the grid type ball mill. When the steel ball is lifted to a certain height, the steel ball has a large falling height relatively while the pulp surface is lower. Therefore, the steel ball has a large impact on the material, and the grinding effect is better.

6. Overgrinding

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.

7. Maintenance degree

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.

Summary

Grid type ball mill

Advantages:

● Fast ore discharging speed, less overgrinding phenomena, large output per unit volume, higher output than verflow type ball mill;

Disadvantages:

● Complex structure, easy to block grid board when discharging, difficult to repair, relatively low operation rate.

Overflow type ball mill

Advantages:

● Simple structure, easy to maintain, large pieces of ore and steel ball is not easy to discharge because the discharging pipe is casted with left-hand thread;

Disadvantages:

● Low production capacity per unit volume, serious over-crushing phenomenon.

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.