What are the Differences Between Dry and Wet Type Ball Mill?
The ball mill is a kind of grinding machine, which is the key milling machine used after the material has been crushed, and it also has a mixing effect. This type of grinding machine has a cylindrical body with spherical grinding mediums and materials.
The centrifugal force and friction generated by the rotation of the fuselage bring the material and the grinding medium to a certain height and then fall. Impact and friction grind the material into fine powders.
It is widely used in cement, silicate, new construction material, refractory material, chemical fertilizer, ferrous metal and non-ferrous as well as ceramics, and widely applied to dry or wet grinding for ores and grindable materials. The wet type is often equipped with a classifier, and the dry type is configured with a suction and separation device.
Both of the dry and wet ball mills are composed of feeding port, discharging port, turning part, and transmission parts such as retarder, small transmission gear, motor, electronic control. The wet grinding can be widely used, because most of the minerals can be wet milled.
The dry grinding is used on a smaller scale, but some materials can only be dry milled. So what are the differences between them?
The difference in structure
1. Dry type
The ball mill is equipped with a cylindrical rotating device and two bins, which can rotate by gears. The discharge port is straight, and there are also air intake devices, dust exhaust pipes, and dust collectors.
2. Wet type
The structure of the ball mill is simple. The discharge port is horn-shaped, and there is a screw device in it, which is convenient for discharging materials.
The difference in working principle
1. Dry grinding
Dry grinding means that when the ore is ground into the size we need, the powder will be brought out from the ball mill by the airflow.
The material from the feeding device is uniformly fed into the first bin of the mill by the hollow shaft spiral. This bin has stepped lining or corrugated lining, which is filled with steel balls of different specifications.
The rotation of the cylinder generates centrifugal force to bring the steel ball to a certain height, and then fall, which will hit and grind the material. After the material is coarse grinding in the first bin, it will enter the second bin through the single-layer partition plate.
This bin is embedded with a flat liner, and the steel balls inside will further grind the material, then the powder is discharged through the discharge grate to complete the grinding. We can't add water or other liquids during the grinding process.
It is required that the materials must be dry, so it is called dry grinding. The dry grinding plays an important role in the grinding of various minerals.
2. Wet grinding
Wet grinding means that after the ore entering the mill, it will complete the grinding under the interaction of the grinding medium and the ore, and meet the needs of users.
The material needs to be added water or anhydrous ethanol during the grinding process. We must control the grinding concentration, otherwise, it will affect the grinding efficiency. The amount of water depends on the use of the mud, the amount of clay in the formula, and the water absorption of the clay.
It will be gradually pulverized under the action of impact and grinding. The movement of the ore needs to be driven by the water. The bulk material will be cracked under the impact and grinding of the grinding medium, with the crack gradually increasing and deepening, the final material will be separated from the crack to achieve the effect of bulk material being ground.
The grinding ore will be discharge through the discharge port, and then the discharged mineral will be classified into the qualified product in a spiral classifier, with the coarse sand being returned to the ball mill through the combined feeder to continue grinding.
The feeder feeds material continuously and evenly, the ground material will be continuously discharged from the ball mill. The wet ball mill can be divided into three types according to the motion characteristics: a simple swing type wet ball mill, a complex swing type wet ball mill, and a hybrid swing type wet ball mill.
1. Dry type
The dry grinding is suitable for materials that can react with water, which may not be used for wet grinding such as cement, marble and other building materials. Some products which require storage and sale in powder form is suitable for dry grinding, and in some other arid areas, because of the lack of water resources, dry grinding can also be used to save water.
2. Wet type
Wet grinding is suitable for most materials, such as all kinds of metal ore, non-metallic ore. As long as it is water-repellent and will not affect the quality of the finished product, the material can be used for wet grinding.
Common ore includes copper ore, iron ore, molybdenum ore, phosphate rock, feldspar mine, fluorite ore, etc. The proportion of steel balls, materials, and water in wet grinding is 4:2:1. The detailed proportion can be determined by grinding experiments.
At the same time, the size of the alumina grinding balls is also required. If the ratio is good, then the ball milling efficiency will be greatly improved. Generally, there are large, medium and small balls, and the better ratio between them can also be obtained through experiments.
Their advantages and disadvantages
1. Dry ball mill
- 1 The dry ball mill adopts the slab-type grinding tail discharge, the discharging speed is fast and the process is unhindered, which will not be bloating. The cylinder does not need to be cooled with the service life is long.
- 2 The dry ball mill has many auxiliary types of equipment, which changes the structure of the original mill and make the engine body and the underframe integrated. It can be one - time hoisting on the foundation plane during installation, and the spindle is subjected to double row radial spherical roller bearings, which can reduce energy consumption by 30%.
- 1 Dry grinding is inefficient. During the grinding process, when large deposits show small cracks, and the crack will become smaller and smaller during the kneading process because there is no material blocking in the cracks, which will result in low grinding efficiency and slower material separation.
- 2 In addition, there may be dead angles in the mill. Once the material enters a dead angle, then it cannot be driven without water, which will result in not being ground.
2. Wet ball mill
- 1 Wet grinding is efficient, and it can process the ore with high moisture and high mud content. Because water and surface active substances will be dissolved in water, it will penetrate into the cracks of the material, and the effect of blocking will increase the cracks, which will grind the bulk material and make the material fine.
- Therefore, the wet grinding production capacity is higher than dry grinding with low power consumption. In addition, the material is easy to flow and the water can wash away the fine particles in time to avoid the phenomenon of over-grinding in the grinding process.
- 2 In addition to high efficiency, it also has other advantages such as low noise, fine and uniform grinding grain size, and low environmental pollution.
- 3 Wet ball mill has a simple transportation device with less auxiliary equipment, so the investment is about 5%-10% lower than that of dry ball mill.
- 4 The grinding particle size is fine and uniform, and the wet ball milling can not only grind agglomerate into fine particles, but also mix the lean material and the plastic material well.
- 1 The consumption of mill balls is high.
- 2 The process of dehydration and drying increases the cost.
How do we choose the right ball mill?
1. According to the requirements of material
The dry milling process may be used when the particle size of the powder is not required to be very fine or when the ball milled product is to be stored or sold in powder form. For example, in the production of cement, it is necessary to choose dry grinding instead of wet grinding, otherwise, it will be difficult to meet our needs.
2. According to the overall economic perspective of ball mill grinding
Wet grinding is generally used in mineral processing, because the wet ball mill has the advantages of strong materials adaptability, continuous production, large grinding ratio, easy to adjust the fineness of the milled products, and it is widely used at present.
Most of the ball mills sold on the market are wet ball mills, which have high grinding fineness and good beneficiation effect.
Since the dry and wet ball mill equipment has its own advantages, we must find out the suitable grinding type that the material is suitable for so that we can ensure quality and efficiency. Welcome to consult Fote company, where our professionals will give you a satisfactory answer based on your needs.