FMQY Series Wet Overflow Ball Mill for Fine and Ultrafine Grinding

The FMQY Series Wet Overflow Ball Mill is a core grinding equipment widely used in mineral processing, non-metallic mineral beneficiation, chemical processing, and new material industries where fine and ultrafine grinding is required. With its mature design, stable structure, and proven process performance, this type of ball mill has become a standard solution in modern concentrators and wet grinding plants.

The mill operates based on the impact, abrasion, and grinding action generated by steel grinding media inside a rotating cylindrical shell. During operation, water is introduced into the mill to form a slurry with the feed material. As the cylinder rotates at a speed lower than the critical speed, the grinding media are lifted and dropped repeatedly, efficiently reducing the material particle size through continuous impact and grinding. Under typical operating conditions, the product size can reach −0.074 mm or finer, meeting the requirements of fine liberation in most beneficiation processes.

Unlike grate discharge ball mills, the FMQY Series adopts an overflow discharge design. When the slurry level inside the mill exceeds the height of the discharge trunnion, finely ground material with good fluidity naturally overflows from the discharge end, while coarse particles settle and remain in the mill for further grinding. This inherent classification characteristic makes the wet overflow ball mill particularly suitable for fine grinding stages and closed-circuit grinding systems.

Cylindrical Shell

The shell is a large rotating cylinder fabricated from high-quality steel plates by rolling and welding. The length-to-diameter ratio (L/D) is typically equal to or greater than 1.5, providing sufficient residence time for fine grinding. The inner surface of the shell is lined with high-manganese steel liners or rubber liners, which protect the shell from wear while enhancing grinding efficiency by lifting the grinding media.

Feeding Section

The feeding section consists of a feeder and a hollow feed trunnion. It ensures stable and continuous feeding of material, often including cyclone underflow (circulating load), together with process water. The feeding design supports smooth slurry flow into the mill without blockage.

Discharge Section (Overflow Discharge)

The overflow discharge section is the key structural feature distinguishing this mill from grate-type ball mills. There is no discharge grate. Instead, a trumpet-shaped overflow liner is installed at the discharge end. When the slurry reaches the designed level, qualified fine particles overflow automatically, while coarse particles remain in the grinding zone. This simple and reliable structure significantly reduces the risk of blockage and excessive wear.

Main Bearings

The mill is supported by large-capacity bearings, which can be either sliding bearings or rolling bearings depending on project requirements. The bearing system is designed to support the heavy rotating mass of the mill with stable and reliable performance under continuous operation.

Drive System

The drive system typically includes a high-power electric motor, a reduction gearbox, and a girth gear with pinion. The system drives the mill to rotate at the optimal operating speed, ensuring sufficient grinding efficiency while avoiding excessive wear and energy loss.

Grinding Media (Steel Balls)

Grinding media are selected and proportioned according to feed size, material hardness, and target product fineness. Multiple ball sizes (such as Ø100 mm, Ø60 mm, Ø40 mm) are commonly used in a reasonable ratio to achieve effective impact and grinding.

Metal Ore Processing

In flotation plants, the FMQY Wet Overflow Ball Mill is widely used as a secondary grinding or regrinding mill to achieve adequate mineral liberation. In gold and silver cyanidation plants, it is used to grind ore to very fine sizes, increasing leaching efficiency. It is also applied in magnetic separation and gravity separation circuits where fine grinding is required.

Non-Metallic Mineral Processing

The mill is suitable for wet grinding of quartz, feldspar, kaolin, calcium carbonate, and other non-metallic minerals, producing fine or ultrafine products for filler and coating applications.

Chemical and New Material Industries

It is commonly used for wet grinding of chemical raw materials, ceramic glazes, and precursor materials for batteries and advanced materials, where particle size control and uniformity are critical.

Environmental and Metallurgical Applications

The equipment can be applied in wet grinding processes prior to hydrometallurgical leaching, as well as in the resource recovery treatment of industrial solid waste through wet grinding methods.

Applicable Materials

The FMQY Series Wet Overflow Ball Mill is suitable for most ores, rocks, and industrial materials that can be processed by wet grinding. It is not recommended for materials that react with water or processes that strictly require dry grinding.

Excellent Fine and Ultrafine Grinding Capability

The overflow discharge design enhances fine grinding performance, making the mill particularly effective for producing products finer than 200 mesh (0.074 mm), a range that is difficult for grate-type ball mills to achieve efficiently.

Simple Structure and High Reliability

With no discharge grate or complex lifting components, the discharge structure is simple and robust, reducing potential failure points, wear parts, and maintenance requirements.

Uniform Product Size Distribution

The natural overflow mechanism retains coarse particles inside the mill, resulting in finer and more uniform product size with fewer oversized particles in the discharge.

Ideal for Closed-Circuit Grinding Systems

The overflow slurry can be smoothly connected to hydrocyclone classification systems, forming an efficient and stable closed-circuit grinding process that is widely adopted in modern concentrators.

Controlled Overgrinding in Closed Circuit Operation

When combined with an efficient classification system, qualified fine particles are promptly removed from the mill, reducing residence time and minimizing the risk of excessive grinding.