Ball Mill

What is a ball mill?

A ball mill is an ore grinding mill that can crush and grind various types of ores to liberate the closely associated minerals from each other. Ball mills are widely used in cement making and ore beneficiation plant.

Normally the ore will be crushed before it enters the ball mill, and then it would be fed into the ball mill either wet or dry.

Working principle of ball mill

It runs steadily and smoothly

The main parts of a ball mill are a motor, gearbox, drum, liner, grinding media. Three-phase motor to drive the ball mill, the motor connects with the gearbox which can reduce the shaft speed.

When the ball mills begin to rotate, grinding balls will slide up the side and be held in place by centrifugal force. As the ball rotates to the upside of the rotating drum, the weight of the balls overcomes the centrifugal force which is causing them to cling to the inside of the liner. When the balls move to the top side of the drum, they'll tumble back down roughly.

During the process, the ore is rubbing against itself and the balls are rubbing against the ore to realize the material size reduction.

The oversized pieces that don't make it through the grate are going to remain within the ball mill, and they'll be reduced in size further until they can exit the ball mill.

Different types of ball mills

4 Most common types of ball mills divided by grinding media

The most common grinding media used by ball mills are four types: steel balls, pebbles, ceramic balls, and grinding cylpebs. Although ball mills are similar with each other, they are different in grinding media, working capacity, application fields.

1. 1Steel ball mills: The ball is manufactured by low-carbon alloy, high manganese steel or high carbon and high manganese alloy steel. It is often used in primary grinding and has strong abrasive wear resistance while maintaining good toughness.
2. 2Pebble mills: Its grinding media are usually pebbles, rocks or other high density grinding media which should be tough, hard, heavy and resistant to any chemical action. The pebble mill is much lighter than other ball mills because of reduced load and low horsepower requirement.
3. It is applied on area where iron contamination is detrimental. For example, when grinding Feldspar for making porcelain, certain clays, and glass sand, you must use pebble mills.
4. 3Ceramic ball mills: its grinding media are usually alumina ceramic balls, and it is smaller than other ball milling machines. It is suitable for mixing and milling of the general and special material in chemical industry.
5. 4Ball mill machines with grinding cylpebs: With advantages of stable quality, high productivity and strong wear resistant, this machine types especially suits for cement making plant.

2 Types of ball mills divided by different working ways

According to different working methods, ball mills can be divided into two types: dry ball mill and wet ball mill.

1.Dry-grinding ball mill:

Dry means little water and moisture in the grinding process. Tpically the ball mill maybe charged with 30% to 45% of balls. With the rotating drum, the ore is rubbing against itself and the moving balls, and the process is going to continue from the inlet to the discharge port.

2. Wet-grinding ball mill:

Wet grinding is mainly used in ore  beneficiation

Wet means that we add water and form a slurry, and that slurry is going to occupy 50% of the ball mill volume. In a wet ball mil, approximately 15% water may form slurry which is a mixture between water and the crushed ore, sometimes also referred to as pulp.

As the balls drop down onto this slurry, and some of the slurry is also taken up with the balls, the balls are going to impact and grind the slurry(ore and water) so that you can get the ore size reduction.

Continuous ball mill design

Various liner materials

• White iron liner is most serviceable for the smaller mills which does not use large grinding media.
• Manganese liners cost lower than white iron liners, and they contain 12% to 14% manganese.
• Ceramic or rubber linings are designed for continuous operation, and both can be used in wet or dry grinding.
• With ceramic liners, grinding media can be furnished as either flint pebbles or high-density ceramic balls.

Bearings of a ball mill

• Cylindrical roller bearings suit for smaller ball mills.
• Trunnion bearings which are hydrostatic bearings are often installed on the large ball milling machine, that means you have an oil pump to supply the oil for the bearings. The oil will form the boundary between the bearing itself and the shaft.

The critical speed of ball mill

The optimal speed is usually set to 65%-80% of the critical speed. Ball and pebble mills usually rotate at 70—85 % of critical speed. For dry grinding, the speed is usually much lower.

Ball mill drum and armor

• A ball mill drum itself may usually be manufactured from steel.
• The armor itself is made of an abrasive, resistant material, and this is often manganese alloy steel, chrome steel alloy or manganese steel alloy.

What is a ball mill used for?

Grinding Metal ore

Preparation of non-metallic ores such as coal-water slurry

The preparation of coal water slurry is mainly divided into two solutions:

The roller crusher, a large crushing equipment, can compensate for the insufficient capacity of the ball mill when working with ball mill together, and double the production capacity of the ball mill;

Powder concentrator can control the particle size and adjust the load distribution of the roller press and the ball mill, so as to realize the large-scale single-machine process system.

The advantages of the two processes:

• The new technological processes can reduce the space occupied and the number of equipment and auxiliary facilities. Finally, it can cut down investment by more than 10%.
• The new process adopts a large-scale, single-machine system to simplify the parallel control system and instrumentation, and reduces operating personnel.
• Reduce energy consumption per ton of pulp by 30-50%.
• Reduce wear medium consumption by 30-100%.
• Improve the adjustment and control of the process.

Ball mill is widely used in building materials and chemical industry

Perfect final material ground by ball mill

The ball mill can process about 200 kinds of ore materials, and the common materials in our lives can basically be ground with the ball mill.

Below we list the grinding effects of seven materials:

Gravel material

Mineral materials

Outstanding advantages of ball mill

Save energy: Fully hydraulic operation helps to realize automatic operation, greatly improving reliability and longevity of the machine;

The flexible design of the discharge port: The discharge port is designed reasonably, and customers can choose the iron remover according to their needs;

Turning part: The cylinder, lining, medium, compartment board and discharge raft of the turning part are all made up of high-quality original parts;

Large feeding unit: Reasonable feeding port design greatly increases feed volume;

High grinding efficiency and good quality of the liner: The lining and grinding body are made of alumina ceramic, quartz, SILEX or special materials, and it is designed with no iron pollution when crushing hard materials;

Closed system to reduce dust: Ultra-fine ball mill and classifier form a closed system with advantages of negative pressure delivery, low dust, reducing damage to the human body; Besides, the ball mill has higher product quality and cheaper operating prices.

Customer case - ball mill sold in India and Indonesia

Cement ball mill working in India

Fote ball mills sold in India

India is a populous country in the world and one of the "BRICS" countries. It has good cooperation and win-win relationship with China. For machinery processing enterprises of China, the business opportunities contained in India are limitless, and mining equipment from China is entering deeply in India market.

With the gradual recovery of the mining market, the market position of mineral processing equipment is more stable with the increasing position. The cement ball mill produced by Fote is more prosperous in the Indian market.

So what is a cement ball mill?

The cement ball mill is mainly used in the grinding of finished products and raw materials of cement plants for open-flow grinding, and also for circulating circulation grinding with the powder separator.

ball material is chrome steel alloy or manganese steel alloy

It has the characteristics of strong adaptability to materials, continuous production, large crushing ratio, and easy to adjust the fineness of the milled product. The cement ball mill can be produced either dry or wet, or both at the same time as grinding and drying.

In February 2018, an Indian customer contacted us and hoped to purchase a large ball mill equipment for his ore dressing line. Because our company has a large number of ball mills exported to India, the customer finally chose us to provide with a little investigation.

According to the information provided by the customer, Fote engineers recommended a ball mill suitable for him, the specific data is as follows:

• Use location: India
• Capacity: 100T/H
• Material name: cement
• Raw material hardness: soft
• Feeding size: ≤25 mm
• Production line type: fixed
• Specific model: Ф4000×5000

Iron ore grinding in Indonesia

The large-scale ball mill grinding line

The concentrator of the client in Indonesia is an old factory with a long history, and one of the main raw material bases in the area.

The mining of high-quality iron fine powder with grade of 67.50% is gradually advancing to the deep mines, and the annual output of the main mining area has dropped from the original 10 million t/a to 6 million t/a.

The ore in the mining area has fine grain size and complex mineral composition. It is a difficult to grind ores, which has caused large fluctuations in the quality of concentrate in recent years, and a decline in concentrate output.

The company commissioned the Fote Group to study the grindability, selectivity, iron mineral composition and degree of mineral liberation in the mining area.

After repeated research with experts, the company chose a solution with low investment and fast efficiency based on the actual situation, that is, the design of adding a one-stage grinding and dressing process. They transformed the original two-stage grinding and dressing process into a three-stage process, so that the ore is fully finely ground to achieve monomer dissociation. That design ensured the quality of the concentrate while maximizing the metal recovery rate.

Economic benefit analysis after transformation

1 The three-stage grinding and dressing process makes the grinding process operate stably and effectively.

2 Compared with the general separation before the transformation, the metal recovery rate has increased by 6.73%, and the annual processing of 2 million tons of transition type ore increases the production of iron concentrate by 35,200 tons.

3 It also helped to release original ball mill feeding capacity. Compared with the original Φ3600 mm×6000 mm and Φ2700mm×3600 mm ball mill before the transformation, the new process increased the average processing capacity increased by 7.58t/h and 0.82t/h respectively.

4 It raised concentrate production by 4.83 Million tons and 83,500 tons of prolific concentrate in total.

5 Based on the current price of iron concentrate, the successful operation of this project can increase the sales revenue by 5.94 million $/a, and it can create an additional profit of 1.92 million $/a.

Why FTM ball mill?

High-quality parts minimize maintenance cost

The ball mill produced by Fote Machinery shows good casting process performance, high mechanical properties and good heat treatment performance to minimize the wear during materials impacting.

The grinding balls are mainly made of high manganese steel: it makes ball mill balls good toughness, good manufacturability with low price. Its main feature is that under the action of greater impact or contact stress, the surface layer will become harden quickly. Its work-hardening index is 5-7 times higher than other materials, and the wear resistance is greatly improved.

Ball mill accessories include big gear, pinion, hollow shaft, ring gear, big ring gear, steel ball, compartment board, transmission, bearing, end lining and so on.

Big gear is an important part of ball mill, so the choice of big gear is a crucial process when produce a ball mill. According to the working conditions of the big gears, they are usually manufactured as follows:

• Medium carbon structural steel
• Medium carbon alloy steel
• Carburized steel
• Nitrided steel

The structure of the ball mill big gear has various shapes due to different requirements, but from the technical point of view, the gear can be regarded as composed of two parts: a ring gear and a wheel body.

According to the distribution form of the teeth on the ring gear, it can be divided into straight teeth, helical teeth, herringbone teeth and the like.

Reasonable prices

• Usage/Application: Industrial
• Rotational Speed of Chamber: 36 R/ Min
• Type: Grinder
• Voltage: 380 V
• Weight: 50 T
• Power: 710 kW

Fote ball mill manufacturer has 40 years of producing experience. Due to the continuous improvement of machine itself and production capacity, it has won the recognition of customers at home and abroad.

Compared with other merchants, our more reasonable prices are also an important reason for many old customers to purchase products for the second time.

Fast delivery speed

Even during the Covid-19, according to different national policies, as long as countries where conditions permit, we will always deliver the products to customers in the fastest way and put them into production on schedule.

The following is the fastest shipping method and approximate delivery time according to the actual situation of different countries. (Only some customer countries/regions are listed)

Fote Machinery has set up a strong after-sales service to maintain on-site production and provide users with 24-hour online service.

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10 Purchasing tips of ball mill

1 Guarantee the production capacity of the ball mill: The selected ball mill should realize the specified output while ensuring the required fineness of grinding.

2 The production capacity should be higher than design: The designs should take the change of hardness and fineness of the ore into account. Generally, while the deep ore of the ore deposit becomes hard or thin, the selected grinding machine should be able to adapt and ensure that the initial operation runs well.

3 Grinding test is a must: When there is no actual data in the designs, the grinding test must be required. Especially for large-scale mines, the grinding machine selection calculation and proportional enlargement should be carried out from the basic data obtained.

4 Due consideration of large-scale equipment: The large-scale equipment is the trend since the 21st century because of its advantages of light in total equipment, small in area, few in operators and auxiliary systems, and correspondingly low in investment and production costs.

5 Select equipment with high operating rate: There are also good and bad points in the same type of equipment. Rod mills and self-grinding machines sometimes have lower operating rates but are still suitable under certain conditions.

6 Understand the hardness, grade and other properties of minerals and try to choose energy-saving ball mill.

7 Know about the fineness required for mineral grinding, and select the aperture and bin position of the closed plate according to the fineness required by the mineral.

8 According to the requirements of production, choose the suitable diameter and length of the ball mill.

9 Choose a new updated ball mill, preferably choose the professional ball mill manufacturer corresponding to your minerals.

10 Select the modulus of the large teeth and small teeth of the ball mill. According to the price of the ball mill, customize the material of the liner and the thickness of the steel plate.

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