I. Introduction of sintering in Jinan Steel
Jigang's existing sintering machine 5:
Three 120m2 sintering machines, corresponding to 1#, 2#1750m3 blast furnaces and one 320m2 sintering machine, corresponding to 3#1750m3 blast furnace and one 400m2 sintering machine, corresponding to one 3200m3 blast furnace and 120m2 sintering machine, three main pumping motors 4000kW, and a damper opening of 100 %, there is no advantage to using a
Frequency Converter.
320m2 sintering machine main exhaust fan supporting 2 sets of 5600kW motor, completed in July 2010 frequency conversion.
The main suction fan of 400m2 sintering machine is equipped with 2 sets of 7500kW motors. In 2008, the design used high-voltage frequency conversion and was operated in August 2009. It is the first domestic application of domestic 8000kW high-power frequency converter.
Second, the suction sintering process
III. Case Introduction Jinan Iron & Steel 400m2 Sintering Main Exhaust Fan 7500kW/10kV Synchronous Motor Inverter Application 3.1 Project Background The main exhaust fan is the main process equipment for sintering production. The changes in air pressure and air volume are directly related to the output and quality of the sinter. , And its power consumption generally accounts for about 50% of the entire production line.
The main suction fan of large-scale sintering machines in China, taking into account the safety of production and the unstable air leakage rate of the sintering system (generally about 30%), is appropriately enlarged (generally enlarged by 10%) in the aspects of design, type selection and manufacturing, resulting in widespread fan Large.
Because of the large motor power, in 2008, the industry basically used a step-down or frequency conversion start-up, after the start of the end, the motor was switched to industrial frequency operation. This method starts stable and reduces the impact on the power grid. The disadvantage is that the air volume needed by the sintering machine is adjusted by adjusting the damper baffle during operation. In general, the damper opening is between 45% and 65%, and the power loss and waste are obvious. .
If it is controlled by a frequency converter, the damper can be fully opened. By adjusting the frequency of the frequency converter, the required air volume for the sintering machine can be obtained, which can save energy by more than 20%.
400m2 sintering machine main pumping design high voltage frequency converter, based on the following understanding:
1) The experience of using frequency conversion with dust-removing fan and the energy-saving benefit 2) The successful operation experience of the finished product dust blower with 320m21500KW.
3) Energy-saving measurement of the main pumping frequency conversion, conservative estimation of energy saving rate of 20%, annual efficiency of nearly 10 million yuan 4) Sintering main pumping frequency is the development trend, Jinan Iron and Steel is willing to eat crabs, willing to try the corresponding risk 3.2 equipment parameters
When designing the 400m2 sintering machine at Jigang, considering the economy, one of the two flue ducts of the sintering machine is designed as a desulfurization flue, and the other is a non-desulfurizing flue, which is ready for future flue-gas desulfurization. The flue gas with high sulfur content in the head and tail section enters the desulfurization flue, and the flue gas with low sulfur content in the middle enters the non-desulfurization flue.
400m2 sintering machine main process parameters:
Large flue negative pressure: -8--13kPa
Fan inlet temperature: 130°C
Material thickness: 800mm
Fan parameters:
1) Manufacturer: Shenyang Blower Co., Ltd. (Application of Domestic Large Fan)
2) Fan Type: Double Intake Centrifugal 3) Fan Model: SJ20000-14T
4) Treatment of smoke volume: 20000m3/min, full pressure 17000Pa
5) Fan shaft power: 6462kW (130°C)
6) Fan shaft power: 6994kW (80°C)
7) Quantity: 2 sets 8) Manufacturers supporting 2 sets of 7500kW motors and brushed excitation devices Motor Parameters:
1) Manufacturer: Shanghai Motor Factory 2) Model: T7500-6/1730 Synchronous Motor 3) Rated Power: 7500kW
4) Stator rated voltage/current: 10kV/494A
5) Rated rotor voltage/current: 300V/380A
6) Rated speed: 1000r/min
7) Power factor (cosφ): 0.98
3.3 Technical solutions
2 sets of main exhaust fans adopt 2 sets of high-voltage frequency converters for speed control. No frequency-frequency soft-starting devices are provided, and direct starting of power frequency is not allowed.
Based on the above operating conditions, Leadwards provided a two-to-two alternative solution consisting of two high-voltage inverters, fourteen high-voltage circuit breakers, two magnetizing inrush current suppression + reactor cabinets, and two sets of air-water cooling systems. , a coordinated control cabinet composition.
The main technical features:
uUsing dual-rectifier transformers for the first time u Coordinated control of two-to-two operation, variable frequency non-disturbance synchronous switching and coaster startup u Synchronous start u Fully sealed air-water cooled u Simple one-button operation 1) First use of double rectifier transformer 2) Coordinated control One of the examples shows that the TF1 inverter control device has failed.
The coordinated control of the two sets of inverters is achieved by an independent coordinated control cabinet.
The entire switching process 3-5 minutes to meet the needs of the process does not stop!
3) Control logic
4) Workmanship, frequency conversion and non-disturbance synchronous switching and coaster start The same frequency converter can be operated by variable frequency operation, with no disturbance to the power frequency operation, the same frequency converter can be in the power frequency running state, and the non-disturbance is switched to the variable frequency operation key technology: The voltage, frequency, and phase of both sides of the input and output of the inverter are calculated by the software during the same period, that is, the phase lock is enabled, and the frequency conversion and the power frequency are switched after the lock is synchronized to achieve no disturbance.
The frequency converter can start by coaster under the condition of motor rotation, and can find the frequency corresponding to the rotation speed automatically. 5) Synchronous start When the excitation cabinet is started and controlled by the inverter, the inverter first controls the excitation cabinet, and the rotor excitation converter of the synchronous motor is based on excitation feedback. Starting at 0Hz, gradually increasing the frequency, the motor starts slowly; 6) The fully sealed air-water-cooled sealed design ensures that the inverter indoor does not generate air flow with the outside of the room, effectively keeping the interior clean.
2 sets of water cooling system consumes 270 cubic meters of water per hour.
7) Simple one-button operation
3.4 Energy-saving of equipment operation The project started to install and debug the equipment in June 2009, and it was successfully put into use in August. During the trial production, the output of the sintering machine is limited to the production stage due to the impact of the blast furnace, the utilization factor is 0.65-0.83, and the electricity consumption per ton of the sintered ore is 31-36 degrees (excluding the power consumption of the raw material area).
1. After the main suction fan is put into operation after the main suction fan is put into operation, the normal production damper opening is 95%, and it is generally not adjusted any more. According to different sintering production processes, the frequency converter frequency is adjusted to 30-45Hz, and the rotation speed corresponds to 600rpm-900rpm.
2. Energy-Saving Effect Jinan Iron & Steel 400m2 sintering machine main pumping high-voltage frequency conversion system has been put into operation since August 2009. The equipment has been running steadily, the energy-saving rate has exceeded 20%, and the annual electricity saving totals more than 10 million yuan.
3.5 Application of Frequency Conversion for Main Smelting Blower of Jinan Steel Production Line Name Voltage Capacity Quantity Load High Voltage Inverter Model Date of Order 400m210kV7500kW2 Synchronous Machine Sintering Main Exhaust Fan HARVEST-S10/550 2008 320m210kV5600kW2 Synchronous Machine Sintering Main Exhaust Fan HARVEST-S10/410 2010 IV. Surge analysis 4.1 Surge phenomenon In the cold state of the two fans, the vibration of the rotor is all normal and meets the design requirements, but the fan rotor surpasses the standard during the heat load test. In addition, fan 1# is 50~100A larger than 2# fan in cold state and working state, and current fluctuation is much larger than 2# fan.
In order to maintain the normal production of the sintering machine, production is maintained by restricting the speed of the main extractor of No. 1 and restricting the opening of the inlet damper. The speed of 1# fan is controlled below 750rpm, the damper is at 90%, and the fan of 2# is opened to 60%. The speed is within the range of 900rpm, avoiding the surge area of 1#. In this way, as much as possible to 2 # fan large air volume, speed, and less to 1 # fan load, in order to meet the 400m2 sintering machine initial production equipment operating efficiency temporarily underloaded production status.
The following data are the operational data for September 4-6, 2009:
This kind of production severely restricts the efficient operation of the sintering machine, inconveniences the production, and also has a great influence on the life of the fan. Therefore, the solution to the surge problem of the 1# main exhaust fan is urgently needed.
4.2 Analysis of the problem There are many reasons that cause fan surge:
(1) Coupling installation skew or impeller production problems;
(2) The rotor dynamic balance is not good;
(3) The problem of unequal distribution of air flow to the two main exhaust fans due to stripping S.
After analysis and research, problem 1 can be eliminated. If there is a coupling problem, the fan can be found when it is running in a cold state; it can eliminate the 1# fan impeller production problem, and at the same time, it can determine two fans based on the cold running test data. The performance is consistent.
When the fan 1# is running in the hot state, severe surge occurs within a certain operating range, but when it is cold, it runs normally, so it can also eliminate the vibration caused by the imbalance caused by the heat stress of the fan rotor when it is released and deformed. It is also possible to exclude the possibility of reason 2 at this time.
So there may be reason 3.
4.3 Preliminarily solving the problem By conducting the 1# main pump fan surge area test under a variety of operating conditions, we actively seek out the wind volume, negative pressure, fan speed, and the fan inlet damper opening range of the fan where the surge occurs, and at the same time carry out process rectification:
A: Add partitions to the three-way pipe at the inlet of the two fans to redistribute the air volume of the two fans to minimize the surge of the #2 fan and cause the surge of the #1 fan.
B: The round steel support is added to the inlet ducts of the two fans. The purpose is to enhance the system rigidity and reduce the vibration.
C: The air outlet is connected with the air inlet. The butterfly valve is installed in the middle. If necessary, open the butterfly valve to supplement the air volume of the air inlet.
After the above transformation, the problem has improved slightly, but it has still not been completely resolved.
4.4 The problem is analyzed again
We also analyzed the design performance curve of the 1# fan provided by the fan manufacturers.
The fan has a rotational speed of 823 rpm, a negative pressure of 11.5 kPa, an inlet flue gas density of 0.717 kg/m3, and an efficiency of 86%. The flue gas volume is about 16,000 m3/min.
Actual measured on-site 1 # fan speed 750rpm, negative pressure 11kPa, efficiency 86%, the actual amount of flue gas treatment is only about 8000m3/min, and the design of the processing of flue gas from the gap.
At the same time, the 2# fan has a speed of 1000rpm, a negative pressure of 11.5kPa, and an efficiency of 86%. In the case where the damper opening is less than half of the 1# fan, the air volume is about 15000m3/min, which is basically consistent with the designed value.
4.5 The final solution to the problem We judge from this that the cause of surge is that the flue setting does not match the actual operating conditions. In mid-November 2010, we completely separated the flue and realized the uniform configuration of the two fans of the flue. The main pumping and surge problem of No. 1 was completely solved.
Fifth, the highlight of the application of high-voltage frequency converter in the main suction fan taking into account the impact of the descaler pump motor power, frequent fluctuations in load torque characteristics, according to the motor and load inertia moment parameters, motor and load nT curve, acceleration and deceleration time The requirements of the Leader high voltage inverters are as follows:
1. The first example of energy-saving repayment (EMC) project was implemented at Jinan Iron & Steel 2. The largest domestic frequency converter was used for the first time in similar equipment 3. Automatic adjustment of synchronous motor excitation current 4. Successful application of synchronous switching technology , To achieve frequency - frequency uninterrupted switching.
5, to achieve the two inverters are mutually standby 6, the use of more humane system coordination control technology, the use of touch screen and operating switch double insurance operation design, increase the reliability of the system control.
7. The successful use of high-voltage frequency converters avoids the problem that blower surges seriously affect production.
If the original design is a soft-start method, the 400 sintering machine will not be able to produce due to the unsolved problem of No. 1 fan surge. It is precisely because the technicians of the ironworks insist on using high-voltage inverters to avoid this serious consequence. .
VI. Conclusion The main suction fan is one of the key equipments of the sintering machine system. Its smooth operation is related to the stable operation of the sintering machine and its potential. The entire project belongs to the turnkey project (including equipment body, civil engineering, cooling, control and other design and construction). Through the close cooperation of engineers from Jinan Iron and Steel and Leader Huafu, it has broken the former main fan of large-scale sintering machine must use the imported fan. The myth, as long as the correct understanding of the sintering machine operating conditions, domestic fan + high voltage variable frequency speed control technology can meet the requirements.
At the same time, frequency conversion is adopted to greatly increase the degree of automation of the system, realize the soft start of the motor, extend the life of the motor, achieve the purpose of saving energy and reducing the electricity consumption rate of the plant, and reduce the baffles and pipelines caused by adjusting the baffle. The wear and the economic losses caused by frequent downtimes and maintenance have greatly reduced maintenance.
