Rod Mill

Rod mills are very similar to ball mills except for the use of steel rods as grinding media. In the rod mill, steel rods grind the ore by rolling and rotating. The feeding of rod mill is 50 mm, and its output particle size is -4 to 35 mesh.

Rod mill produced by FTM Machinery

Application fields of rod mill

Applications of rod mill

Rod mills are widely used for ores, cement, silicate products, steel slag, building materials, refractory materials, fertilizers, glass, ceramics and other materials.

1. Used for grinding rare metal ore

In the gravity separation or magnetic separation plant of tungsten tin ore and other rare metal ores, rod mills are often used in order to prevent over-crushing.

2. In the first grinding stage

If the rod mill is used for the first stage grinding equipment to grind materials from 6–20 mm to 1–3 mm in the two-stage grinding process, the production capacity will be larger and the efficiency will be higher.

3. It can replace the cone crusher for fine crushing

In some cases, it can replace the short-head cone crusher for fine crushing. When processing soft ores (especially viscous ores) from 19–25 mm (or even 32 mm) to 6–10 mesh, using rod mills is simpler and cheaper than a closed circuit formed by the short-head cone crusher and the sieve.

For hard ores, it may be more economical to use a short-head cone crusher and a sieve to form a closed circuit. Whether to choose a ball mill or a rod mill must be determined according to the specific conditions.

Advantages of rod mill

Saving power

The rods have a screening effect on the materials during movement, which can make the large particle material be lifted to the high position of each layer and concentrated to the place with strong crushing ability. Therefore, the working efficiency of the rod mill is high and the power consumption is low.

Few over-crushing

When the ore is ground by the steel rod, it is first crushed into coarse particles and then ground into smaller ones, thereby reducing the risk of over-crushing.

Advantages of FTM Machinery rod mill

More uniform discharge size

Rod mill changes the surface contact of traditional ball mill to line contact.

When the rod rotates and rises along with the liner, the coarse particles are sandwiched between them, allowing the fine particles to pass through the gap of rods, which is conducive to crushing coarse particles, so the coarse particles are concentrated in the place where the grinding medium hits.

Therefore, the rod mill product is more uniform, and the over-crushing is lighter. It is suitable for ores with different hardness (Mohs hardness 5.5–2).

Adjustable discharge fineness

The particle size of the material produced by the rod mill can be adjusted according to the needs of users, because there are a fineness control device and a screening device for discharging inside the rod mill. These two devices work at the same time.

Smaller mineral particles can be obtained by adjusting their size, so the size of the ground particles can be effectively guaranteed.

Structure of rod mill

The rod mill adopts a reducer drive mode and central discharge. It mainly consists of the following parts:

Feeding device

The feeding device is a shoe-shaped hopper, and the upper flange is connected with the feeding equipment to receive the fed material. There is an inspection door on the back wall of the hopper, forming a round tube and extending into the spiral barrel mounted on the hollow shaft, through which the material enters the mill.

Structure of rod mill

Rotary part

The rotating part is a cylinder rolled and welded by steel plates. A liner is arranged inside the cylinder, which not only protects the cylinder but also lifts the steel rod to a suitable height to improve the efficiency of sand making. There is an acid and alkali resistant rubber pad between the steel liner and the simplified end cover to reduce noise and vibration.

Large and small gears

The large and small gears are driven by helical gears with balanced work, small impact and long life. It adopts spray lubrication and regular oil injection, which reduces the labor intensity of workers, has a good lubrication effect and reduces the consumption of lubricating oil.

Main bearing

The main bearing supports all the weight of the rotating part, steel bars, materials, etc. The bearing bush is supported on the spherical seat, which can play a self-defense function to adapt to manufacturing and installation errors.

After the long-term work of the main bearing, the bearing bush will wear and tear, resulting in the sinking of the hollow shaft. The sealing bracket can be adjusted downward to ensure that the seals and the hollow shaft are in good contact.

Rod mill features

Rod mill on working site

1. 1 The rod mill usually uses a steel rod with a diameter of 50–100 mm as a grinding medium. The length of the steel rod is 25-50 mm shorter than that of the cylinder, and is usually made of high carbon steel containing 0.8%–% carbon.
2. 2 The loading amount of the rod is about 35%–45% of the effective volume of the rod mill. When observed, the horizontal plane of the rod is about 100-200 mm below the centerline of the cylinder.
3. 3 The ratio of the length of the rod mill to the diameter is generally 1.5–2.0, and the inner surface of the liner on the end cap should be a vertical plane. The purpose is to prevent and reduce the chaotic movement, bending and breaking of the steel rod in the cylinder to ensure that the steel rod moves regularly.
4. 4 The rod mill does not use grid plate for mine discharge, but uses overflow type and open type discharge; the diameter of the hollow journal of the discharge end is generally larger than that of the same size ball mill.
5. 5 The rotation speed of the rod mill should be lower than the working speed of the ball mill of the same specification, so that the medium inside is in the sloping state.

Rod mill working principle

Working principle of rod mill

Rod mill makes tube run with the help of the reduction gears drove by dynamo or the low-speed synchronization electrical machine. There are steel rods in the tube which are thrown at a certain high speed by centrifugal and friction force and then fall.

The ground material enters into the tube continuously and is crushed by the moving steel balls. After that, they are discharged from the machine naturally and will start the following working process next.

How to choose steel bars for different industries?

The diameter of the steel bar should be selected appropriately so that there is enough weight to crush the bulk material, and enough point contact and line contact to grind the small material.

A steel bar with a smaller diameter has a smaller surface area and less wear on the liner.

However, the small diameter steel rod has a short life, and will soon be worn to the abandoned size of 25–40 mm, which is easy to bend and break.

Different industries use different steel rods with different diameters. Here are some classic industries for example:

Customer case-steel slag processing production line of South Africa

The rod mill produced by FTM Machinery integrates research and development, production, processing and matching. We have rich experiences, and the products are exported to the United States, India, Russia, Indonesia, South Africa and other countries and regions, with a good market reputation.

Therefore, customers said that they can work for a long-term mutual benefit and win-win future together with us. For example, in October 2018, a large new building materials company in South Africa directly found FTM Machinery through recommendation and hoped that we could equip a steel slag processing production line for them.

For details, please refer to the following customer cases.

Feedback from South Africa customers

In October 2018, the steel slag treatment production line deployed by FTM Machinery for a large new building materials company in South Africa was officially put into operation.

In the process of preparing new steel materials, the steel slag treatment rate reached 99%, and the quality of new building materials was superior. The comprehensive energy consumption is reduced significantly.

Due to the high degree of automation of the steel slag rod mill, the original operation line has a capacity of 40 people, and has been reduced to 15 laborers, which has truly simplified the operation mode of the assembly line.

More than a year later, due to the super-level performance of the MBS steel slag rod mill, the company's production line revenue increased steadily, while reducing the secondary pollution of waste slag gas, the economic income generated at the same time solved the environmental pollution problem of the production line.

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