Solutions

Solutions

Application of Megmeet frequency converter in cement industry

To reduce the power consumption of industries such as cement, glass, and electrolytic aluminum, we must find a breakthrough in technological and industrial progress. Inverter, as a major industry for energy saving and consumption reduction, has mature technology, stable products, increasingly lower prices, and increased use and maintenance levels of customers, which provide conditions for the mass use of inverters in the building materials industry. Megmeet frequency converters have been successfully applied in the above-mentioned industries, which has contributed to the application of energy saving and consumption reduction in China.


Energy-saving principle of frequency converter speed regulation

About 60% of the world's electricity consumption is consumed by electric motors.

The load of the motor in the production machinery varies greatly. According to the general classification rule, the load can be divided into square load, constant torque load, constant power load, etc. The relationship between these three loads and energy consumption is as follows (P stands for power, M stands for torque, n stands for speed):

Load type

Constant torque M = C

Square torque M∝n2

Constant power P = C

M=f(n)

p=f(n)

 

image.png

image.png

image.png

Device

Conveyor belt, lifting machinery

Various fans and pumps

Coiling machine, rolling mill

Relationship between power and speed

P∝n

P∝n3

P=C

Purpose of using inverter

Meet process requirements and increase efficiency

Energy-saving

Meet process requirements, improve product quality and efficiency

Power saving effect

Ordinary

Notable

no

From the perspective of energy saving, we mainly analyze the square load, which consumes more than 70% of the energy in the building materials industry. So why is there energy-saving control for such loads?

1、 Consider the design margin. When designing a building material project, the long running time of the project must be considered, and the process difference between the early and late stages is large, and sufficient margin must be left. For example, the blower and induced draft fan design stipulates that the air volume should reach a margin of 5-10%. Therefore, the maximum air volume and air pressure margin are used as the basis for the selection design, and the fan series is limited. The model can only be moved up. This is more common when the motor selection power is 20-30% larger than the actual power required.

2、 In the actual production operation, for the fan load that is throttled by the valve baffle, etc., they increase the damping coefficient of the system pipeline, resulting in a waste of electrical energy. If you choose a frequency converter, you can adjust the flow accurately according to the actual production needs.


Theoretical analysis of energy saving by frequency conversion speed regulation

For various fan and pump loads, due to P ∝n3, the theoretical power consumption and speed are cubic relations, so after applying the inverter, the power saving effect is significant. The following table shows the fan and pump loads after applying the inverter. The power saving rate when different flow Q *, speed n *, shaft power P * (relative value percentage of rated value) at a certain frequency value.

Flow Q*(%)

100

90

80

70

60

50

40

Speed n*(%)

100

90

80

70

60

50

40

Frequency value(Hz)

50

45

40

35

30

25

20

Shaft power P*(%)

100

73

51

34

22

13

6.5

Power saving rate N

0

27

49

66

78

87

9

It can be seen that when the flow rate is reduced, the motor speed can be reduced to achieve a high power saving rate.


Cement plant inverter application 

1、Application of frequency converter in vertical kiln Roots fan

Most of the cement plants below 2KT / D in China are equipped with 160 ~ 220KW Roots fans on the vertical kiln (the larger the production line, the larger the power of the fans used on the vertical kiln). The traditional method of air volume control is to rely on the vent valve Adjust. Because the air volume of the Roots fan is relatively constant, the air volume needs to be adjusted at any time according to the conditions in the kiln during calcination. When the air volume needs to be reduced in the kiln, the excess air volume is released through the air release valve, causing serious energy waste.

Among the electric energy consumed by the cement clinker calcination clinker, the electric energy consumption of the Roots blower accounts for about 60%. With the adjustment of the electricity price (the overall upward trend), the proportion of electricity cost in the production cost of cement production will increase. The higher. Therefore, reducing the energy consumption of the blower becomes an important link to improve the economic efficiency of the enterprise.

The cement production process requires the air volume to be adjusted according to the conditions in the kiln, the blower volume of the fan is adjusted, and the power supply frequency of the fan can be changed by the inverter to adjust the air volume steplessly to adjust the air volume, leaving the application and energy saving of the inverter Larger space. In practice, it is proved that this is true: after installing the MG300 frequency converter on the 132KW Roots fan of a 2KT / D cement plant, the power saving rate was as high as 60%, and the power consumption per ton of clinker decreased from 15 degrees before the frequency converter was installed. 6 degrees after installation; when a 1KT / D cement plant installed an inverter on the 55KW Roots blower of the fluidized system of the cement clinker rotary kiln production line, the power saving rate was as high as 70%, and the daily power consumption decreased from the original 600 degrees to 180 degrees after installation, 420 degrees of power saving per day.

A comparison table of the power consumption of Red Star Cement Plant before and after the inverter is applied to the fan:

Device name

power

Average current

Power consumption

energy saving effect

Economic Analysis

KW

before use

After use

before use

After use

10,000 degrees / year

Ten thousand yuan / year

One- chamber fan

45

58.3

39.0

34.2

17.6

13.8

9.6

Two-chamber fan

75

71.2

30.2

41.6

18.1

18.0

12.6

Three-chamber fan

75

85.6

45.1

50.6

26.8

18.3

12.8

Three-chamber fan

75

85.0

52.4

49.7

25.8

18.5

13.0

Coal blower

132

142.6

56.8

82.1

33.0

38.6

27.0

Castor cooling fan

30

26.4

8.2

13.0

5.1

6.0

4.2

Exhaust fan

90

121.6

50.0

72.0

29.1

33.7

23.6

       2、 Application of centrifugal fan and water pump equipment In addition to Roots blowers, there are a large number of places where centrifugal fans are used to supply air in cement plants. The air volume of this kind of cement kiln is adjusted by the opening of the air door. For centrifugal fans, the frequency conversion of the water pump also has huge energy-saving potential. The flow of centrifugal fan pump equipment is proportional to the speed. Therefore, when adjusting the air volume or flow rate, if the flow rate or air volume is reduced by 20%, the power consumption will be reduced by nearly 50%, but the speed is squared with the pressure. When the speed drops by 20%, the pressure will drop by 36%, which is related to the Roots fan In different places, you need to consider when you transform.

After the water supply pump uses the inverter, a closed-loop automatic control loop is formed by the pressure sensor installed at the outlet of the pipe network and the pressure set inside the inverter, so that the entire system automatically controls the flow to keep the pressure constant, so that the water supply pump is in the best energy-saving state Compared with the traditional water supply equipment with storage tank, it saves the construction area and has an ideal power saving effect. At the same time, it also has the advantages of water saving and noise reduction, improved reliability, and no secondary pollution.

3、 Energy saving application on air compressor The air compressor's constant pressure air supply uses a frequency converter and pressure to form a closed-loop control system, which reduces pressure fluctuations to less than 1%. In addition, it also reduces noise and vibration, ensuring long-term stable operation of equipment, thereby reducing equipment maintenance and extending equipment use life. Before the frequency conversion speed regulation transformation, the pressure fluctuation was relatively large, and the air compressor could not be started with pressure. Now the inverter can be started at will under any pressure, and the starting current is greatly reduced. Through the practical application of frequency converters, the power saving rate of most compressors is above 25%. However, the motor power of the compressor is relatively large, from tens of kilowatts to hundreds of kilowatts. The application of the frequency converter greatly improves the quality of control, and the economic benefits are also very obvious.

4、 Application on unloader / powder separator Vertical kiln unloaders generally use 18.5-30KW slip speed control motor, the speed is usually controlled at 300-1000RPM (technically required). The characteristics of slip motors are that the lower the speed, the lower the efficiency, and the characteristics are very soft. Inverter speed regulation was used to replace the original slip speed regulation. After several application results, the average energy saving was proved to be about 40%.

The powder separator equipment was originally driven by a 75KW slip motor. The equipment is simple and the price is low. However, the motor body has high noise, large vibration, high energy consumption, high reactive power loss, and high bearing failures. The slip controller is installed next to the dusty motor, and there are many failures such as speed adjustment, sudden stall, and on-site maintenance. Large, affecting the safe operation of the entire system. The system design controls the motor to run at 594RPM, the electrical parameters of the field test are input voltage 385V, input current 72A, power factor 0.82, input power 40KW. After frequency conversion speed regulation transformation, the field measurement parameters are input voltage 387V and input current 18A. The power factor is 0.92, and the input power is 11KW (the inverter is equipped with a DC reactor as standard). Therefore, after the speed adjustment of the slip motor is changed to frequency conversion, the energy saving effect of the equipment is obvious, and the maintenance amount is greatly reduced.

5、Application in pre-adding water into ball system At present, the pre-adding water into the ball process technology has been very common in the shaft kiln. This process has achieved obvious results in improving the quality of pelletizing, improving the calcination operating conditions, and increasing the output and quality of shaft kiln clinker. Using the good system integration of the inverter itself, it communicates with the host computer through the field bus PROFIBUS-DP, and uses centralized control to achieve dual-loop adjustment, which can realize automatic tracking adjustment of the water-material ratio. The pre-watering system can truly play the role of humidification and pelletization, improve the pelletization quality, and create conditions for the shaft kiln to produce high-quality and high-yield clinker.


The potential market analysis of the cement industry inverter

The application of the inverter in the cement plant is not only in the above aspects, but also in rotary kilns, ball mills, unloaders, disc feeders, double-tube reamers, speed control belt scales for group plate feeders, feeding reamers , Castor cooler, etc. need to exchange speed regulation part. As the country continues to introduce environmental protection systems, the requirements for environmental protection will also increase. Cyclone dust removal, bag-type dust collector and other products will be more obvious in the application of energy-saving transformation projects.


Summary 

It can be seen from the above theory combined with the actual application situation that the use of frequency converters in cement plants has the following outstanding advantages:

1、To meet the technological requirements, the speed regulation range of the MV300G vector control inverter reaches 100: 1, and the speed regulation range in the cement process can meet the technological requirements within the range of 10: 1.

2、The use of frequency converter facilitates centralized control and improves the automation level of the factory. Megmeet MV300G not only comes standard with RS485 communication interface, supports MODBUS protocol, but also supports PROFIBUS-DP, CANOPEN and other field buses. Through the built-in dedicated communication card, seamless integration with DCS system or PLC system enables centralized monitoring of the equipment It becomes possible to greatly reduce personnel maintenance costs and improve equipment reliability.

3、 The smooth speed regulation characteristics of inverter products and precise speed control greatly improve product quality. Megmeet Inverter itself has been targeted to adapt to the harsh power grid environment, on-site environment, etc., such as special anti-grid impact circuit, instantaneous stop function, and circuit / heat dissipation design, three anti-paint Both methods of treatment not only improve the reliability of the inverter, but also ensure the stable operation of the equipment. At the same time, the soft start characteristics of the inverter also reduce the wear of current impact and mechanical impact.

4、 The frequency converter can realize energy saving, reduce cost consumption, and obtain considerable economic benefits.