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[Keywords]: raw material mill circulator blower, kiln exhaust fan, kiln exhaust fan, coal mill exhaust fan high voltage inverter, energy saving I. Project Overview Yu Sheng Cement was founded in 1985 and was transformed into a limited liability company in 1998. (Sichuan Emeishan Cement Co., Ltd.), changed to a joint stock company (Sichuan Yusheng Cement Co., Ltd.) in September 2007. It now has assets of 4 billion yuan and more than 2,800 employees. There are 7 new dry process cement production lines, and the total output of cement is 11.20 million tons. We have used multiple frequency converters of our company. In 2010, a new energy-saving project was completed, namely, the frequency conversion renovation project of 4 sets of high-pressure and high-energy-consuming equipment such as the raw material mill circulating fan, the kiln head and the kiln exhaust fan, and the coal mill exhaust fan in the second factory. This is a further application of the three-phase 5000t/d production line in Jiuli Manufacturing Plant after completion of high-voltage frequency conversion.
The implementation of the project will be coordinated by the plant's technical center, the equipment management department and the Jiuli Manufacture No. 2 plant. After pre-construction of electric room construction and cable take-off and other preparatory work in advance, the inverter will be quickly installed on the 23rd of October when the inverter arrives at the factory. In the wiring, only 4 days, all the work such as the installation and commissioning of the raw material mill circulating fan, the kiln head and the kiln exhaust fan, and the coal mill exhaust fan were successfully completed, and they were officially put into operation on October 26th. According to preliminary monitoring, the electricity consumption per ton of clinker on the line has dropped by 3.5 kWh, the cost has decreased by 2.2 yuan, and the annual electricity bill can save more than 3 million yuan.
Second, raw material mill circulation fan, kiln head and kiln exhaust fan, coal mill exhaust fan to change the necessity of frequency drag The production line of four wind turbines produced by Lanzhou Motor Co., Ltd. rotor winding asynchronous motor drag, the original operation The method is to drive the hydraulic coupler at the full speed of the motor, and adjust the size of the air volume by adjusting the opening of the fluid coupling and the wind deflector. Due to the limited capacity of the power grid, the motor is not allowed to start the band operation directly. Only the fluid coupling can be driven first, and then the opening of the fluid coupling can be gradually increased to start the fan. Then, the air volume can be adjusted by adjusting the opening of the damper. This operation has the following disadvantages:
1. The speed range is limited, unable to start the hydro-pneumatic coupler, the speed regulation is an inefficient speed control mode, the speed range is limited, high-speed discarding is about 5% -10%, the low-speed slip loss is large, because the efficiency is proportional to the speed , Low efficiency at low speed, low accuracy, poor linearity, slow response, large starting current, large device, must be installed between the equipment and the motor, not suitable for transformation; unable to soft start, coupler failure, can not switch operation The maintenance is complicated and the cost is too large to meet the needs of improving the overall automation level of the device.
2. Throttle adjustment reaction lags behind, adjustment speed is slow, adjustment accuracy is not high Reliance on the damper adjustment actuator to adjust the throttle opening, the mechanical part limits the adjustment speed is limited, the adjustment accuracy is also affected, often on-site air volume control is not in place, and, With the increase of the service life, deviations in the baffle opening indications have occurred, resulting in an increase in the adjustment error and failing to meet the requirements of the on-site process.
3. Throttle adjustment wastes energy, unscientific, not economic When the cement plant was initially built, considering the possibility of subsequent expansion and operation and safety and wear over time, the surplus of motor and fan was selected to be larger, and the rated current of the motor was 90A. The actual operating current of the motor is only about 75A on average. The throttle adjustment is used to artificially change the resistance curve of the air duct, and a large amount of energy is wasted on the damper.
4. The motor has been tested at full speed, and the maintenance cycle is short. Because the motor runs at full speed, the mechanical parts such as motor bearings and fans wear faster, and the bearing temperature rises higher. The carbon brushes on the rotor slip ring wear very seriously and the replacement cycle is short.
Third, the choice of speed mode At present, the main high-speed high-voltage asynchronous motor speed control methods are the following: Cascade speed control, internal feedback cascade speed control, hydraulic coupling speed control and frequency control. The high-voltage frequency conversion speed regulation has the following unmatched advantages over other speed control methods:
1. The inverter uses a liquid crystal display digital interface, adjusts the touch panel, can display the voltage, current, frequency, motor speed at any time, and can display the real-time status of the motor at any time.
2. Accurate frequency resolution and high speed accuracy can fully meet the needs of various production process conditions.
3. The high-voltage frequency converter has an international external interface, which can be connected with various instruments such as programmable controllers (PLC) and industrial control computers, and can be connected with the original equipment control loop to form part of the closed-loop system, such as with the original DCS system. Implement data exchange and interlock control.
4. With power electronic protection and industrial electrical protection, to ensure that the inverter and motor are safe and reliable during normal operation and failure.
5. The motor can achieve soft start and soft braking; the starting current is small and less than the rated current of the motor; the motor start time can be continuously adjusted, reducing the impact on the power grid.
6. Local and remote operation functions, and remote monitoring through the Internet.
7. Reduce the loss of accessories, prolong the service life of equipment, and increase labor productivity.
Fourth, the transformation of the specific implementation of the program and process According to the actual situation at the scene, the bypass cabinet using a drag and a manual program. This structure is a typical manual bypass program, the principle is composed of three high-voltage isolation switches QS1, QS2 and QS3 (Figure, where QF is the original circuit breaker in the high-voltage switchgear). It is required that QS2 and QS3 cannot be closed at the same time, and interlocking is achieved mechanically. When the inverter is running, QS1 and QS2 are closed and QS3 is open. When the power is running, QS3 is closed and QS1 and QS2 are disconnected. 
Disadvantages: When the high-voltage frequency converter fails, it cannot be automatically converted from the frequency conversion to the industrial frequency.
Because the vertical mill circulation fan motor power is relatively large (4000KW), the motor cannot be directly started by the power frequency. Therefore, the motor is used to start the motor with the water resistance device. The rotor slip ring is automatically shorted after the start of the motor, and the motor is adjusted after the full speed operation. The force coupler regulates the fan airflow. The power of the other three fans is small, and the motor is started directly at the power frequency, and then the fluid coupling is adjusted to adjust the fan airflow. Because the user takes into consideration the problem of frequent frequency start-up of inverter damage, the existing hydraulic coupler and water resistance device are retained on the site, and the high-voltage frequency converter is combined with the original secondary circuit of water resistance, and the frequency conversion of the high-voltage frequency converter is taken. Status signal sent to DCS, DCS to the star receiver, send a closing command, directly short circuited motor slip ring, remove the water resistance device, the high voltage inverter to the motor to achieve a soft start; take the high frequency inverter frequency bypass signal To DCS, DCS breaks the star switch cabinet and restores the string resistance function of the high voltage motor.
The field device nameplate parameters are as follows: 
In the above table, the method for calculating the average motor power before retrofitting is:
38×1.732×6×0.8=526 KW
75×1.732×6×0.8=1039KW
88×1.732×6×0.8=1219KW
280×1.732×6×0.8=3880KW
After the transformation, the average power of the motor is calculated as:
26×1.732×6×0.95=428KW
46×1.732×6×0.95=757KW
56×1.732×6×0.95=921KW
216×1.732×6×0.95=3554KW
Note: In frequency conversion operation, the input power factor of the frequency conversion is 0.95; when the power frequency is running, the power factor is the motor power factor 0.80.
The equipment is overhauled once a year. The overhaul time is 30 days. The rest of the time is running. We run for 300 days a year. The actual electricity charge is calculated at 0.5 yuan per unit. 1. (526-428) × 300 × 24 × 0.5 = 353,000 2. (1039-757)×300×24×0.5=101.5 million yuan 3. (1219-921)×300×24×0.5=107.3 million yuan 4. (3880-3554)×300×24×0.5=117.4 million Yuan saves electricity costs for the year: 35.3+101.5+107.3+117.4=361.5 million yuan. The improvement process will now list the on-site conditions before and after the renovation as follows: 
Referring to the above table, you can see:
The indirect effect of the frequency conversion of the cement production line fan is also very obvious. When the inverter is running at low frequency, the rotation speed of the motor and the fan is reduced, the shaft temperature of the motor and the fan is reduced, the mechanical noise is reduced, and the overall maintenance cycle is extended; The frequency resolution is accurate to 0.01 Hz, the adjustment is timely, and the adjustment accuracy is high. The operating personnel can conveniently adjust the operating frequency of the motor through the monitoring interface on the DCS side.
VI. Conclusion At present, many blowers and large horsepower trolleys in cement plants are serious. The air volume adjustment method of the fan is basically adjusted by a baffle plate, which consumes large energy, has poor economic efficiency, and has severe equipment damage. It is urgent to adopt advanced high-voltage frequency conversion speed control for technological transformation to reduce the power consumption of the cement plant and improve the economic efficiency of the enterprise. Practice has proved that the use of high-voltage variable frequency speed control technology for turbines in the cement industry is necessary and feasible, and the economic benefits are significant.
HARSVERT series high-voltage frequency inverters have high reliability, good input and output waveform quality, and vector control technology. They are suitable for frequency conversion transformation of cement plant fans, successfully solve the problem of load fluctuations caused by collapsed materials in cement production, and greatly improve the operation of equipment. Reliability, save a lot of energy, bring greater economic and social benefits for cement plants, has a high promotion value.
The Application of Leader Huafu High-voltage Frequency Converter in 5000t/d Production Line of No.2 Factory of Jiusheng Cement
ã€Abstract】 This article describes the frequency conversion retrofit of four high-pressure and high-energy-consuming equipment such as the raw material mill circulating fan, the kiln head and the kiln exhaust fan, and the coal mill exhaust fan in the first plant of Jiusheng Cement Jiuli Manufacturing Plant. This is a further application of the three-phase 5000t/d production line in Jiuli Manufacturing Plant after completion of high-voltage frequency conversion. Advantages: When overhauling the high-voltage frequency converter, there are obvious points of power failure, which can ensure personal safety. At the same time, the load can be manually put into the operation of the power frequency grid. Fifth, the transformation effect 1. Energy-saving effect is quite obvious, significant economic benefits Yu Sheng cement 5000t / d production line after the frequency conversion transformation, achieved significant energy-saving effect, before the transformation of the fan damper is often open about 70%, the motor runs at full speed; frequency After the transformation, the fan was running at a variable speed and the damper was fully open. Because the on-site operating conditions are not changed greatly, the frequency conversion speed control system often operates at about 42Hz, and the power consumption when adjusting the baffle is greatly reduced. The power saving effect and economic efficiency are significant. Before and after the frequency conversion, the operating data of the motor is shown in the following table. :