How to Choose Between Dry and Wet Grinding in Ball Mills ？

A ball mill is a key piece of equipment used for further crushing and grinding materials after they have been broken down. It is suitable for industries such as cement, silicate products, new building materials, refractory materials, fertilizers, non-ferrous metal beneficiation, and glass ceramics. It can perform dry or wet grinding on various ores and other grindable materials. So, how should we choose between dry and wet grinding when selecting a ball mill for grinding materials? Let’s analyze this from the following aspects: Dry and Wet Grinding in Ball Mills.

What is Dry Grinding and Wet Grinding in Ball Mills?

Dry Grinding

Dry grinding refers to a process where, after a certain amount of crushing inside the ball mill, the material is carried out of the mill by airflow when it reaches the required size. The ball mill used in dry grinding is called a dry-type ball mill. This process does not involve adding water, and the material must be dry, hence the term “dry grinding.” The equipment is cylindrical in shape and is equipped with a fan device, dust removal pipeline, and a dust collector. It plays a crucial “grinding” role in mineral processing operations.

Wet Grinding

Wet grinding means that when ore enters the mill, the grinding medium and the ore itself interact to grind it to a certain extent, thereby meeting the user’s grinding needs. Moreover, water flow also participates in this process: specifically, it drives the movement of the ore. As for the equipment, the wet ball mill is the ball mill used in the wet grinding process. Finally, based on movement characteristics, people divide it into three types: simple swing type wet ball mill, complex swing type wet ball mill and mixed swing type wet ball mill.

What is the Difference Between Dry Grinding and Wet Grinding in Ball Mills?

Equipment Structure

The basic structure of both types consists of key parts: the feeding part, the discharging part, the rotating part, and the transmission part, which includes the reducer, small transmission gear, motor, and electronic control.

The main difference lies in the discharge ports. The dry ball mill has a straight-cylinder-shaped discharge port. It also includes a draft device to remove dust. On the other hand, the wet ball mill has a trumpet-shaped discharge port. It is equipped with a built-in spiral device to help discharge materials. Additionally, most wet ball mills on the market offer high grinding fineness and effective mineral processing.

How it Works

The dry ball mill is a cylindrical rotating device with an outer gear transmission and a two-bin, grid-type structure. The feeding device evenly feeds the material into the first bin through the hollow shaft. Inside the bin, stepped or corrugated linings hold steel balls of various sizes. The rotating cylinder generates centrifugal force, lifting the steel balls to a certain height. The balls then fall, creating a heavy impact and grinding effect on the material. Once the material reaches coarse grinding in the first bin, it passes through a single-layer partition plate into the second bin. This bin contains a flat lining plate and more steel balls to further grind the material. The discharge grate plate then expels the powder, completing the grinding process.

The working principle of the wet ball mill is similar to that of dry grinding. However, the process requires the addition of a liquid medium. Proper control of the grinding concentration is crucial. The amount of water added depends on the purpose of the mud material, the clay content in the formula, and the clay’s water absorption value. The material is gradually crushed through impact and grinding. The crushed ore exits the cylinder through the discharge part. After classification in the spiral classifier, the system separates the qualified minerals. Coarse sand returns to the ball mill for further grinding via the combined feeder. The feeder ensures a continuous and even flow of material into the ball mill. The ground material is then discharged continuously from the ball mill.

Applicable Conditions

During dry grinding, the design of the cylinder sometimes creates dead corners, where some materials cannot be milled. However, wet grinding also has a drawback compared to dry grinding. After wet grinding, the powder must be dried to remove moisture or other liquid media. As a result, energy consumption and costs increase. Cement cannot undergo wet grinding. Therefore, each method has its own characteristics. When grinding materials, choose the appropriate method based on your needs.

Respective Advantages

Advantages of Dry Ball Mill:

The dry ball mill uses a grate discharge system, ensuring smooth discharge without clogging or over-grinding. The cylinder doesn’t need cooling, resulting in a long service life and low failure rate.

The dry ball mill has many auxiliary devices that improve the original mill structure. The body and frame are integrated, and installation can be done by simply lifting it into place. The main bearing uses double-row spherical roller bearings, which can reduce energy consumption by 30%.

Advantages of Wet Ball Mill:

The wet ball mill offers superior performance and higher grinding efficiency. It requires a lower moisture content in the ore and can handle ores with high moisture or mud content.

The wet ball mill has fewer auxiliary devices, and the material transportation system is simpler. As a result, the investment cost is 5%-10% lower than that of a dry ball mill.

Wet grinding not only reduces agglomerates into fine particles (mostly round shapes, with few fractured particles) but also forces non-plastic materials to mix evenly with plastic ones.

How to Choose Dry Grinding and Wet Grinding in Ball Mills ?

Correctly Choosing Dry or Wet Grinding Feed Method

First, the choice between dry and wet feeding depends entirely on the ball mill’s subsequent processes and product nature. Some materials need dry grinding. Why? Because they undergo physical or chemical changes when mixed with water. Additionally, during fine grinding in the ball mill, dry grinding reduces wear on liners and grinding media. It also increases the proportion of fine particles in the product. In some cases, this makes dry grinding the preferred option. Selecting the right grinding method for the material ensures the ball mill operates efficiently and with high quality. Both types of mills have their advantages. So, you should choose the feed method based on specific situations.

Wet Grinding is More Economical and Commonly Used

Second, from an overall economic perspective, mineral processing generally prefers wet grinding. Wet ball mills adapt well to materials. They support continuous production, have high crushing ratios, and can adjust the fineness of the ground product. These advantages make wet ball mills the most widely used. The wet ball mill has a trumpet-shaped discharge port. It also has a built-in spiral device, which makes discharge easy. Most ball mills on the market are wet ball mills. They provide higher grinding fineness and better mineral processing results.

Key Considerations When Choosing Dry or Wet Grinding

Third, dry grinding works in specific scenarios. For example, it suits materials that don’t need extremely fine particle sizes. It also fits when the product needs to be stored or sold as powder—like glaze or pigment grinding. Besides, it’s ideal for manufacturing products such as tiles that need pressing into shape. Take cement production: it always uses dry grinding, as wet grinding can’t meet its requirements.​

People generally use dry grinding for materials that don’t react in liquid media. If a reaction occurs, grinding will form other substances. This makes the ball milling process ineffective.​

In dry grinding, the ball mill cylinder’s design may create dead corners. These dead corners hold unground material. So, you need to pay close attention to this during operation.

Epic Powder

Epic Powder understands that choosing between dry and wet grinding is crucial for optimal material processing. We leverage the insights into their differences, applicable conditions, and advantages to select the right ball mill grinding method. This ensures we deliver high-quality, precisely ground powders tailored to diverse industry needs, from cement to glass ceramics.