Ball Mill

Ball mill is widely used in cement, silicate, new construction material, refractory material, chemical fertilizer, ferrous metal, non-ferrous metal and ceramics. It is widely applied to wet and dry grinding for grindable materials. Wet grinding is often equipped with a classifier, and dry grinding is configured with a suction and separation device.

Both dry and wet ball mills are composed of feed inlet, discharge outlet, rotary part, reducer, small transmission gear, motor, electric control and other transmission parts. Wet milling is widely used because most minerals can be wet milled. Dry grinding is used on a small scale, but some materials can only be dry ground.

Difference between wet and dry grinding

1. Difference in (ball mill) structure

• Dry grinding: A dry ball mill is equipped with a cylindrical rotating device and two bins, which can rotate by gears. The discharge port is straight. There are also air intake devices, dust exhaust pipes, and dust collectors.
• Wet grinding: The structure of wet ball mill is simple. The discharge port is horn-shaped. There is a screw device in it, which is convenient for discharging materials.

2. Difference in working principle

Dry grinding

Dry grinding means that when the ore is ground into required particle size, the powder will be brought out from the dry ball mill by airflow.

Dry grinding process:

1. The material from the feeding device is evenly fed into the first bin of ball mill by the hollow shaft spiral. This bin has stepped lining or corrugated lining, which is filled with steel balls of different specifications.
2. The rotation of cylinder generates centrifugal force to bring thesteel grinding ballto a certain height, and then fall. After the material is coarsely ground in the first bin, it will enter the second bin through the single-layer partition plate.
3. This bin is embedded with a flat liner. The grinding steel balls inside will further grind the material, then the powder is discharged through the discharge grate to complete the grinding.

Please notice that dry grinding needs dry materials, so we can’t add water or other liquids during the dry milling process.

Wet grinding

Wet grinding means that after the ore entered the mill, it will complete the wet grinding under the interaction of grinding medium and ore.

Wet ball mill types: (According to the motion characteristics)

• Simple swing type wet ball mill
• Complex swing type wet ball mill
• Hybrid swing type wet ball mill

Wet grinding process:

1. Wet grinding requires that water or anhydrous ethanol must be added to the material.
2. The movement of ore is driven by water. The bulk material will be cracked under the impact and grinding of the grinding medium. As the crack gradually increases and deepens, the final material will be separated from the crack to achieve the effect of bulk material being ground.
3. The grinding ore will be discharged through the discharge port. Then the discharged mineral is classified into the qualified product in a spiral classifier. While the coarse sand returns to the ball mill through the combined feeder for continuous grinding.

Please control the grinding concentration, as it can affect the grinding efficiency. The amount of water depends on the use of mud, the amount of clay in the formula, and the water absorption of clay.

 

3. Difference in applicable materials

Dry grinding

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 that require storage and sale in powder form are suitable for dry grinding. And in some arid areas, dry grinding can be used to save water.

Wet grinding

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 alumina grinding balls is also required. If theball ratiois good, then the ball milling efficiency will be greatly improved. Generally, there are large, medium and small balls, and a better ratio between them can also be obtained through experiments.

Types: Mining ball mills are divided into two categories, Overflow ball mills: center discharge ball mills; Lattice type ball mills: Peripheral row ore type ball mill.
Batch small ball mill: control the particle size of the material by adjusting the grinding time.

4. Working Principle Of Ball Mill

The material is fed into the barrel of the ball mill through the hollow shaft. The cylinder of the ball mill is driven by the motor to rotate, and the materials and media in the cylinder rotate at a certain speed to move, and the forces included include gravity, centrifugal force and friction. When the grinding medium reaches a certain height with the cylinder, when the self-weight is greater than the centrifugal force, it will break away from the inner wall of the cylinder and fall or roll down. As the gravitational potential energy is converted into kinetic energy when falling, the steel ball will eventually collide with the ore at a certain final speed, and the ore will be crushed by the impact force. The crushed and qualified materials are discharged through the ore discharge port.

Main Parts: The mill includes motor, reducer, slow drive, power distribution control cabinet, feeding device, main bearing, rotary part, discharging device, transmission part, lubrication system (mainly including high-pressure pump station and low-pressure thin oil station) and other parts. The main working part of the ball mill is a rotary cylinder mounted on two large bearings and placed horizontally. The cylinder body is divided into several compartments by a partition plate, and a certain shape and size of grinding body is installed in each compartment. The grinding bodies are generally steel balls, steel forgings, steel rods, pebbles, gravel and porcelain balls. In order to prevent the barrel from being worn, a liner is installed on the wall of the barrel. The length of a cylindrical shell is usually 1–1.5 times the diameter of the shell.

5. Technical Data:

Model	Shell rotation speed (r/min)	Ball load (t)	Feeding size (mm)	Discharging size (mm)	Capacity (t/h)	Motor power (kw)	Weight (t)
Ø 900*1800	36-38	1.5	< =20	0.075-0.89	0.65-2	18.5	4.6
Ø 900*3000	36	2.7	< =20	0.075-0.89	1.1-3.5	22	5.6
Ø 1200*2400	36	3	< =25	0.075-0.6	1.5-4.8	30	12
Ø 1200*3000	36	3.5	< =25	0.074-0.4	1.6-5	37	12.8
Ø 1200*4500	32.4	5	< =25	0.074-0.4	1.6-5.8	55	13.8
Ø 1500*3000	29.7	7.5	< =25	0.074-0.4	2.0-5.0	75	15.6
Ø 1500*4500	27	11	< =25	0.074-0.4	3.0-5.0	110	21
Ø 1500*5700	28	12	< =25	0.074-0.4	3.5-6	130	24.7
Ø 1830*3000	25.4	11	< =25	0.074-0.4	4.0-10.0	130	28
Ø 1830*4500	25.4	15	< =25	0.074-0.4	4.5-12	155	32
Ø 1830*6400	24.1	21	< =25	0.074-0.4	6.5-15	210	34
Ø 1830*7000	24.1	23	< =25	0.074-0.4	7.5-17	245	36
Ø 2100*3000	23.7	15	< =25	0.074-0.4	6.5-36	155	34
Ø 2100*4500	23.7	24	< =25	0.074-0.4	8-43	245	42
Ø 2100*7000	23.7	26	< =25	0.074-0.4	8-48	280	50
Ø 2200*4500	21.5	27	< =25	0.074-0.4	9-45	280	48.5
Ø 2200*6500	21.7	35	< =25	0.074-0.4	14-26	380	52.8
Ø 2200*7000	21.7	35	< =25	0.074-0.4	15-28	380	54
Ø 2200*7500	21.7	35	< =25	0.074-0.4	15-30	380	56
Ø 2400*3000	21	23	< =25	0.074-0.4	7-50	245	54
Ø 2400*4500	21	30	< =25	0.074-0.4	8.5-60	320	65
Ø 2700*4000	20.7	40	< =25	0.074-0.4	12-80	400	94
Ø 2700*4500	20.7	48	< =25	0.074-0.4	12-90	430	102
Ø 3200*4500	18	65	< =25	0.074-0.4	—–	800	137

Note: Capacity May Vary with Different Materials and Feed Sizes.

Material Application

cobblestone	Limestone	Dolomite	Quartz	Weather fossil
Granite	Coal gangue	Iron ore	Copper ore	Lead-zinc mine