Application of the hottest high voltage and high p

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The application of high-voltage and high-power frequency converter in the production of top blowing converter

I. background

the plant of the second Department of Fushun Xinfu Steel Making Co., Ltd. (i.e. the new second refining) was founded in 85 and officially put into production in 89. It has three 15 ton nominal oxygen top blowing converters (now expanded to 20 tons), with an annual output of 710000 tons of steel in 2001, an estimated output of 1million tons of lag loss in 2002, and an annual output of 1.7 million tons of steel in 2003

during the converter blowing process, a large amount of brownish red flue gas will be discharged from the furnace mouth. The flue gas is high in temperature and contains flammable gases and metal particles. According to the comprehensive emission standard of air pollutants (GB16297-1996) issued by China in 1996, the flue gas must be cooled and purified, and then discharged to the chimney by the induced draft fan or transported to the gas recovery system for standby. The new secondary refining production adopts the "three blowing and three" mode, and each converter is equipped with a set of dust removal system. The dust removal system adopts the two-stage venturi flue dust purification mode, and the flue diameter Φ 1.6m, flue gas transmission pipeline 820mm, fan model D700, motor power 440kw/6kv. Due to the periodic intermittent oxygen blowing of the converter, in order to meet the requirements of energy conservation and environmental protection, the fan is required to operate at a variable speed during the whole steelmaking working cycle, with high speed when blowing oxygen and low speed when not blowing oxygen. Originally, hydraulic coupling was used for speed regulation, with high speed of 2700r/min (designed to be 2900r/min) and low speed of 800r/min. Due to the limitations of hydraulic coupling technology:

· the speed regulation range is between 30% and 90%, and the speed is unstable; Moreover, the low speed of 800r/min is still high, resulting in a waste of energy. When running at high speed, the hydraulic coupling sometimes loses rotation, and the converter mouth smokes

· after more than 10 years of use, the hydraulic coupling has been seriously aged, and the bearings need to be replaced frequently, resulting in the shutdown of the converter, which can not meet the needs of continuous production

· the efficiency of the motor is low and the loss is large, especially at low speed

· low adjustment accuracy, poor linearity and slow response

· the starting current is still relatively large, affecting the electrical stability

· when the hydraulic coupler fails, it cannot be switched to the power frequency bypass operation, and it must be shut down for maintenance

· serious oil leakage, great environmental pollution, and serious oil erosion on the ground

in view of the above-mentioned problems in the hydraulic coupling, it has become a top priority to transform it

at the end of 2001, the Second Steelmaking began to expand and transform. In order to improve the operation efficiency of the fan and solve many problems caused by the use of hydraulic coupling, Xinfu Steel decided to carry out frequency conversion transformation

II. Converter transformation scheme

· the converter is required to have high reliability and long-term operation without fault

· the frequency converter is required to have a bypass function, which can switch the motor to power frequency operation in case of failure

· the speed regulation range should be large and the efficiency should be high

· it has logic control ability and can automatically increase and decrease the speed according to the oxygen blowing cycle

· there is a resonance point jump setting, which can make the motor run away from the resonance point and prevent the fan from panting

after investigation and comparison in many ways, Xinfu iron and Steel Co., Ltd. cooperated with Beijing Lide Huafu Electric Technology Co., Ltd. to jointly formulate a frequency conversion transformation scheme for the dust removal fan of No. 1 converter. The transformation scheme is as follows:

1 Equipment configuration

km: high voltage true powered by frequency converter Subramanian Sundaram, a graduate student in electrical engineering and computer science at MIT, said: "If people want to add some printed electronic components air circuit breakers

kg1, kg2, kG3: vacuum contactors

bpq:harsvert-a06/080 frequency converter

dj:440kw/6kv asynchronous motor.

km is the original high-voltage switch, kg1, kg2 when choosing electronic universal testing machine, kG3.

dj is the original asynchronous motor. If the capacity is expanded to 630kw/6kv ordinary three-phase asynchronous motor in the future, the frequency converter must have driving ability.

When the fan is running at high speed, if the frequency converter has serious failure, the motor should be automatically switched to power frequency operation. After the current blowing cycle, kG3 will be automatically disconnected and the frequency converter will be repaired. After the frequency converter is repaired, it will automatically return to the original frequency conversion speed regulation state through the reset button. If running at low speed, disconnect kG3 immediately and start maintenance. In this way, in case of serious failure of the frequency converter, the system can automatically switch to the power frequency power, and the load does not need to be shut down, so as to meet the requirements that the site cannot be shut down

2、 Motor and fan parameters

motor parameters: fan parameters:

model: JK model: d

rated power: 440kw intake volume flow: 700m3/min (mixed gas)

rated voltage: 6kV pressure added value: 2600mmh2o

rated frequency: 50Hz inlet temperature: 35 ℃

rated current: 50A spindle speed: 2975rpm

rated power factor: 0.89 shaft power: 370kW

rated efficiency: 92.5%

rated speed: 2970rpm

3. Dust removal fan process requirements

1) converting process cycle

A to B is iron mixing and scrap.Time

b to C are the fan speed-up time, which can be adjusted

c to D are the oxygen blowing time

d point fan starts to decelerate

d to e are the sampling time for furnace temperature measurement

e to f are tapping time

f to G are slag splashing time

the whole blowing process cycle is about 21 minutes, of which the high-speed time (C to d) is 12 minutes. The high speed is set at 45Hz, which can be adjusted; The low speed is set as 5Hz, which can be adjusted

2) the frequency converter and the field interface

are at point B, and a pair of closed nodes (nitrogen and oxygen conversion points) are provided by the field. The frequency converter starts from low speed to high speed. At point C, after the frequency converter reaches the high-speed, a pair of closed nodes (high-speed status nodes) are provided to the site for the on-site operators to work on the oxygen lance. At point D, another pair of closed nodes (fan deceleration point) are provided to the frequency converter on site. The frequency converter starts to reduce the speed, and the speed reduction time is not specified. However, if the speed needs to be increased during the speed reduction process, the frequency converter should meet the speed increase requirements

the fan speed, nitrogen and oxygen switching node and oxygen gun position node meet the following relationship:

the two pairs of nodes (nitrogen and oxygen conversion point, fan deceleration point) provided to the frequency converter on site and the high-speed status nodes provided by the frequency converter to the site are passive nodes, with a capacity of 2a/30vdc or 0.8a/230vac

3) technical indicators of frequency converter

input voltage three-phase AC effective value 6.3kV ± 10%

input frequency 50 ± 5Hz

output voltage three-phase sine wave voltage kV

output frequency Hz

frequency resolution 0.01Hz

acceleration time can be set according to process requirements

deceleration time can be set according to process requirements

frequency setting mode high and low speed, It can adjust

fault diagnosis and detection within the Hz range. Automatic detection, automatic positioning

side power factor 0.95 (at high speed)

overload protection 120% l minute (every 10 minutes), 150% immediate protection

protection grade IP20

ambient temperature ℃

ambient humidity 90%, no condensation

altitude below 1000 meters

III Equipment operation

at the end of 2001, our company ordered a high-voltage frequency converter from Beijing Lide Huafu Electric Technology Co., Ltd., with the model of harsvert-a06/080. The frequency converter was officially put into use on March 14, 2002. We believe that the production, installation and commissioning cycle of the frequency converter is very short, with a total of only more than 3 months, which provides a strong guarantee for the timely production of No. 1 converter

1. Compared with the original hydraulic coupler, the high-voltage inverter produced by Beijing Lide Huafu Electric Technology Co., Ltd. has the following advantages: stable operation, safety and reliability. In the past, the bearings had to be replaced after using the hydraulic coupling for about 40 days, and the boiler had to be shut down for about half a day each time, resulting in huge economic losses. HARSVERT-A frequency converter is maintenance free. It only needs to replace the ventilation filter on the cabinet door regularly without stopping the machine, which ensures the continuity of production

2. Significant energy saving effect, greatly reducing the power consumption per ton of steel

3. The motor realizes real soft start and soft stop. The sine wave current provided by the frequency converter to the motor without harmonic interference reduces the number of motor faults. At the same time, the frequency converter sets the jumping frequency of the resonance point, which avoids the long-term operation of the fan at the resonance point, makes the fan work smoothly, reduces the wear of the fan bearings, prolongs the service life and maintenance cycle of the motor and fan, and improves the utilization rate of the fan

4. The protection function of the frequency converter is perfect. Compared with the original relay protection, the protection function is more and more sensitive, which greatly strengthens the protection of the motor. During the commissioning of the frequency converter, the frequency converter automatically protects and reports the motor overcurrent. After inspection, it was found that one phase line nose of the motor was broken, and the motor ran without phase, resulting in overcurrent. We carried out maintenance in time to avoid the expansion of the accident

5. The frequency converter has a seamless interface with the field signal to meet the needs of production. The frequency converter has a built-in PLC, and the on-site signal access is flexible. The converter provides a pair of high-speed and low-speed nodes for the frequency converter, and the frequency converter automatically operates back and forth at high speed and low speed according to the status of the nodes; Connect the flue gas flow and flue gas temperature signals of the converter in the previous instrument cabinet to the frequency converter, and dismantle the instrument cabinet, which greatly saves the site. The frequency converter has its own speed measurement, and the speed detector originally connected to the motor has also been canceled. The frequency converter directly provides the motor speed indication for the site.

6. It has strong ability to adapt to the fluctuation of electric voltage. Sometimes the electric voltage is as high as 6.9kv, and the frequency converter can still operate normally

7. Compared with the hydraulic coupling, the noise is greatly reduced during acceleration and the noise pollution is weakened. Since the bearings do not need to be removed and replaced regularly, the pollution of engine oil to the environment is reduced, and the on-site environment of the fan room has been greatly improved

IV. energy saving analysis

before the transformation, the working conditions of 1 # 2 # 3 converter are the same. After the transformation, 1 converter can be compared with 2 # and 3 # converters, and finally the energy-saving data can be analyzed by the power consumption of dust removal per ton of steel

compared with hydraulic coupling, the power consumption of dust removal per ton of steel is reduced by 2.76 degrees/ton on average

1 the annual steel output of converter is expected to be 350000 tons this year, and the electricity price is 0.44 yuan/kwh

total annual power saving: 350000 tons × two point seven six × 0.44 = 425040 yuan, and the power saving rate is 39.2%

at the same time, due to the reliability of HARSVERT-A frequency converter, the iron throwing of blast furnace caused by converter shutdown when the original hydraulic coupling fails is avoided, and its economic and social benefits are also huge

v. conclusion

from the operation of several months, the harsvert-a06/080 high-voltage high-power frequency converter produced by Beijing Lide Huafu Electric Technology Co., Ltd. has good performance, high reliability and obvious energy-saving effect, which meets the requirements of continuous production for the speed regulation system. Our company decided to continue to use it in the transformation of 2 # and 3 # converters. At present, the frequency converters supporting 2 # and 3 # converters have arrived at the site and are being installed and debugged

Author: Liaoning Xinfu Steel Co., Ltd. (end)

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