There are many types of ball mills, which can be dry and wet. According to the discharging method, we can be divided into two types: overflow type and grid type.
Next, I will introduce these two ball mills from the following aspects. I hope I can help you.

1. Use of two ball mill
The main purpose of the ball mill is to regrind the crushed materials, which is also called the crushing operation. It can be divided into dry ball mill or wet ball mill. Under normal circumstances, the feed particle size of wet ball mill is generally 5-25mm, and the output particle size is 0.075-0.4mm; while dry mill has a fineness of 0.038mm.
2. Two-ball mill structure
The two types of ball mills are basically composed of five parts: feeding device, supporting device, rotating part, unloading device and transmission device. The main components are cylinder, lining board, and compartment board.

The difference between the two lies in the structure of the unloading device:
There is a grid plate at the discharge end of the lattice ball mill. There are several fan-shaped orifice plates on the grid plate. The width of the grates on the orifice plate is 7mm-20mm. On one side of the mine end, a mine lifting device is installed, which is a radial rib. The rib divides the grid plate and the end cover into several fan-shaped chambers leading to the hollow journal. When the mill rotates, the radial ribs play the role of lifting the slurry, lifting the slurry discharged from the small holes on the grid plate to the hollow shaft journal of the mine, and then discharged from the mill through the hollow shaft journal.
The overflow type ball mill does not have a grid plate to promote the discharge. Because the hollow shaft diameter at the discharge end is slightly larger than the hollow shaft diameter at the feeding end, the slurry in the mill faces the discharge end to a certain degree. When the surface is higher than the lower limit bus level of the inner diameter of the discharge pipe, the ground material can be discharged from the discharge pipe. On the other hand, the inner surface of the hollow journal bushing is equipped with reverse spiral blades, which can overflow the ore slurry. The pellets and coarse ore lumps from the flow pattern are returned to the mill.

3. Working principle of two ball mill
The material is fed in from the feeding end of the cylinder. The material in the cylinder and the grinding medium steel ball continue to strike and advance along with the rotation of the cylinder. Under the action of extrusion, impact force and grinding and stripping force, the material can be ground and crushed. Move to the discharge port. Due to the continuous forced feeding of materials, under the action of pressure, the materials slowly approach the discharge port, and finally the material silo body with the finished particle size is discharged from the discharge end. In wet grinding, the material is discharged in the form of mineral slurry, and in dry grinding, the material is mixed and discharged in the airflow.
4. Two-ball mill discharging method
In the case of continuous feeding and continuous discharging, the material of the grid type ball mill is forced to discharge ore through the discharge grid under pressure, which is active discharge. The overflow type mill overflows from the discharge pipe when the pulp page in the cylinder reaches a certain height, which is a passive discharge.

5. Discharge granularity of two ball mill
Because the lattice type ball mill is forced to discharge ore, the grinding time of the material in the cylinder is relatively short, and the output particle size is relatively coarse, generally 0.2-0.3mm, which is suitable for the primary grinding stage.

The overflow type ball mill is passively discharging ore. The grinding time of the material in the cylinder is relatively long, so it is prone to over-grinding. The discharge particle size is relatively small, generally less than 0.2mm, suitable for fine-grained ore grinding, and is commonly used in concentrates. The regrind stage.

6. Capacity of two ball mill
It is precisely because the two discharging methods are different that the capacity of the ball mill of the same model is different. The lattice type mill is forced to discharge the ore, the grinding time is short, the material can be processed in a certain period of time, the capacity is larger, and the overflow ball mill is the opposite.

7. Post-maintenance of two ball mill
In contrast, the overflow type ball mill has a simple structure and no grid plate at the discharge end, which is convenient for maintenance. However, the grid center vent, grate and partition board gaps of the grid type ball mill discharge section are easily blocked by the slurry, which is necessary for maintenance operations. Increased difficulty and inconvenient maintenance.