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The ball mill is to be high-efficient and high-efficient, and the driving device needs to give the force! Analysis of the characteristic of common driving mode

Date:2019-07-09 11:23 Source:未知Views:

As the driving part of the mill, the operation characteristics and cost of the transmission system directly affect the stability and benefit of the mill. With the development of large-scale mill, the transmission system of mill also presents a diversified development trend. according to the characteristics and requirements of ball mill, this paper analyzes several common driving forms of ball mill, which provides a reference for users to realize better driving mode.

01. Division of driving mode


Because the ball mill is a kind of equipment with low speed, heavy load and constant speed, its transmission is a kind of high power transmission with large speed ratio. The choice of transmission form of mill is not only related to power, but also related to equipment investment, maintenance and installation location. Usually:

The mill power is less than 10,000kw, which is driven by single motor;

The power of the mill is between 10000-20000kw and is driven by double motors.

The power of the mill is more than 20000kw. it is driven by gear free.

02, several common driving modes of mill

 

2.1 single drive synchronous motor form


This driving mode occupies a large share in the domestic mining market and takes a long time to use, and its layout is shown in figure 2.

The drive system is equipped with synchronous motor, pneumatic clutch, pinion shaft group and large gear. The big gear is installed on the cylinder by high strength bolt, and the rotating motion of the mill cylinder is driven by the rotation of the big gear.

The synchronous motor is divided into a brush motor and a brushless motor. The carbon brush with brush motor is easy to wear and needs to be replaced on a regular basis, but the efficiency of the brushless motor is less than that of the brush motor in a certain current range.

2.2 single drive asynchronous motor form


Single drive asynchronous motor is widely used in chemical industry in China, and it is also used in earlier metal mines, but the mill specification is generally small.

The drive system is equipped with asynchronous motor, reducer, pinion shaft group and large gear. The big gear is installed on the cylinder by high strength bolt, and the rotating motion of the mill cylinder is driven by the rotation of the big gear.

The asynchronous motor is divided into a winding type asynchronous motor and a squirrel-cage asynchronous motor.

The winding type asynchronous motor has advantages in starting performance, and can be connected with an external resistor in a rotor circuit to perform step-down starting. In the grinding system, a water-adding resistor is commonly used, so that the starting and speed-regulating performance of the motor can be improved, the starting current is small, and the starting torque is large; the defect is that the structure is complex, the maintenance is more troublesome, and the running reliability is poor.

Squirrel cage asynchronous motor has the advantages of simple structure, convenient manufacture, low price, wide application of frequency converter speed regulation, convenient use, installation and maintenance, etc. Its disadvantages are small starting torque, lagging power factor and low light load power factor.

Mine mill usually needs to meet low speed and full load of large torque start, so winding asynchronous motor is often used. However, in the special explosion-proof working environment and poor power grid conditions, it is necessary to select squirrel cage asynchronous motor with high protection level.

2.3 Double-drive synchronous motor form.


When the power of the mill is large and the single motor, pneumatic clutch and gear shaft can not meet the requirements, bilateral drive should be selected. The synchronous arrangement of dual-drive motor is shown in figure 4. Two sets of transmission systems are symmetrically arranged on both sides of the large gear, each system includes synchronous motor, pneumatic clutch, pinion shaft group and large gear.

2.4 dual drive asynchronous motor form


Equipped with two sets of transmission systems symmetrically arranged on both sides of the large gear, each system includes asynchronous motor, high-speed coupling, reducer, low-speed coupling and pinion shaft.

The technical difficulty of bilateral drive is synchronization. At present, double hydropower resistance starter is used to control start-up, and mechanical self-balance is used to adjust it after start-up.

03, technical characteristics of driving mode

 

3.1 Single-drive gear transmission

 

3.1.1 single drive synchronous motor


1)The whole transmission system is installed on the same side, with compact structure, simple and small floor area.

2) in the starting mode, first of all, the motor starts without load, and after reaching the normal speed, the pneumatic clutch inflates and holds the brake and drives the gear shaft to run.

3) when the mill stops, open the gas source directly, remove the clutch, and the mill can stop.

4) when the mill stops, the motor does not need to stop, there is no intermediate link, and the transmission efficiency is high.

5) the whole process is simple, convenient and fast.

And 6) under the condition of overload, the safety of the system can be ensured by the slipping of the clutch friction plate.

7) under normal working conditions, the worn friction plate needs to be replaced regularly, and the maintenance cost is low. However, because the high-power clutch is an imported brand, the price is more expensive, the initial investment cost is higher, and the price of spare parts is also more expensive.

8) in the domestic market, synchronous driving mode accounts for more than 90% of the market share.

3.1.2 Single-drive asynchronous motor


1)The transmission system is connected by multiple couplings and decelerated through the reducer.

2) in the starting mode, first start the lubricating station of the reducer to ensure good lubrication. The motor starts under pressure through the liquid water resistance of the outer string and drives the gear shaft directly.

3) when the mill stops, the motor needs to stop. Because of the multi-stage mechanical transmission, the efficiency will be reduced.

4) the whole operation process is relatively complex.

5) under the condition of overload, the mill can only be monitored by the operation of the motor and stopped by the stop of the motor.

6) In normal operation, regular maintenance of rolling bearings and gears is required, and the overhaul and disassembly workload is large. Since the speed reducer has a large number of brands, the price is lower than that of the clutch, so the initial investment cost is low.

7) in the foreign market, this kind of driving mode occupies the dominant position.

Considering comprehensively, the direct drive mode of low speed synchronous motor has the advantages of simple structure, low maintenance cost and good applicability, so it has been widely recognized by users and is in the mainstream position in China at present.

The transmission mode of winding asynchronous motor+reduction gearbox, although the gearbox system is added to reduce the transmission efficiency, but the investment cost of the project is low, the maintenance volume is small, and there is no complicated electrical control equipment, which can better adapt to the harsh operation environment of the mill and the production demand of long-term stable operation, and has a high market share abroad.

3.2 double drive gear drive

 

3.2.1 synchronous dual drive system


1) each side of the system is installed on the same axis, and the arrangement is the same as that of synchronous single drive.

2) when starting, the motor starts without load first, and after reaching the normal speed, the pneumatic clutch inflates and holds the brake and drives the gear shaft to run.

3) when the mill stops, open the gas source directly, remove the clutch, and the mill can stop.

4) when the mill stops, the motor should not stop, there is no intermediate link, and the transmission efficiency is high.

5) the system belongs to high quality and long life operation structure.

6) the key technology lies in the adjustment of load balance.

3.2.2 Asynchronous dual-drive system


The one-sided arrangement is the same as the asynchronous single drive. The system adopts a transverse slip-ring motor, and the key technology for controlling the load balance is to rely on the double liquid resistance starter to start.

The size of asynchronous dual-drive motor is generally large, the structure is complex, the requirements for operators are also high, the overall market share is very small, there are no domestic use cases.

Selecting the appropriate transmission system is an important condition for optimizing the structure of the whole machine and ensuring the normal operation of the equipment, and is of great importance to the improvement of the production efficiency and energy saving and consumption reduction of the mining equipment. Through the analysis and comparison of several driving modes, the reasonable driving device is selected, which can ensure the safe and stable operation of the equipment and realize the expected economic benefit.

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