Yuxi Xinxing Iron and Steel Co., Ltd. is a steel conglomerate that Kunshan Iron and Steel Group has implemented in the province’s multiplication plan and made full use of the resource advantages of Yuxi to expand in Hongta District.
I. Overview
Yuxi Xinxing Iron and Steel Co., Ltd. is a steel conglomerate that Kunshan Iron and Steel Group has implemented in the province’s multiplication plan and made full use of the resource advantages of Yuxi to expand in Hongta District. The company was completed and put into production on March 15, 2005. The main products are: rectangular continuous casting billet, slab, hot-rolled ribbed steel bar, medium and wide band, etc. The products sell well in Yunnan, Sichuan, Chongqing, Guangdong and other markets. Under the excellent situation of continuous improvement of the market economy system, acceleration of reform and opening up, and development of the western region, Yugang seizes opportunities to accelerate development, widely absorbs the successful experience of domestic and foreign excellent steel companies, optimizes the process structure, and vigorously promotes technological progress and energy conservation The work of reducing consumption and cleaner production has made the structure of steel products more reasonable, and the market competitiveness has been significantly enhanced. A qualitative leap has been achieved in the modernization, intensive and efficient industrial process. Energy conservation and environmental protection and economic development have made greater contributions.
2. Production process
The medium and wide-band operation area adopts a three-section beam heating furnace. The air supply volume is adjusted by the air inlet valve. The blower is designed for one use and one standby. It operates 24 hours.
In normal production, when the heating cold steel is damaged, the blower inlet valve opening is 70~80%, and the supply air pressure is maintained at about 4.5kPa to ensure the furnace heating temperature.
When the heating hot steel is damaged, the blower inlet valve opening is 50~60%, and the supply air pressure is maintained at about 4.5kPa. When the heating furnace is insulated, the supply air demand is less, and the inlet valve opening is reduced accordingly. The wind pressure is kept at about 4.2kPa.
Gas exhaust and air exhaust air volume are regulated by air inlet valve. In normal production, when the heating cold steel is damaged, the gas exhaust fan air exhaust inlet valve opening is 70-85%. In normal production, the heating steel is damaged, the gas exhaust fan air exhaust fan inlet valve opening is 50~60%, when the heating furnace keeps heat, the opening of the inlet valve of the two fans is 30%.
The air inlet valve of the air exhaust fan is adjusted according to the steel rolling speed to ensure the uniform temperature in the furnace. The exhaust temperature of the two is controlled within 100 ℃, and the alarm is over 180 ℃. The heating furnace fan process is simple The picture is as follows:
Three, transformation plan
The three-section beam heating furnace blower, gas induced draft fan, and air induced draft fan, because the selection of the motor and fan is based on the maximum production capacity of the heating furnace, because the actual production capacity has not reached the maximum production capacity, the adjustment gate, The method of increasing the fluid resistance of the pipe network to achieve the flow control, so the system has low efficiency, large power consumption, and serious waste of electrical energy.
Due to the continuous and stable air supply required during normal production, the air volume and air pressure do not change much. At this time, the throttling loss can be eliminated by the adjustment of the fan speed by the frequency converter, and at the same time, the operating efficiency of the fan can be improved, although due to the load rate of the motor The drop will reduce its operating efficiency, but due to the large decrease in the operating power of the fan, the loss of the motor is also reduced, and ultimately the operating power of the motor is greatly reduced, thereby achieving the purpose of saving electricity.
1 Variable speed principle:
According to the basic principles of electromechanics, the speed principle of the motor satisfies the following relationship:
n=(1-s)60f/p
In the formula: P-motor pole pair number
F-motor operating frequency
S-slip
It can be seen from the formula that the synchronous speed N1 of the motor is proportional to the operating frequency N of the motor. Since the slip S is generally smaller than 0.05, the actual speed N of the motor is approximately equal to the synchronous speed N1 of the motor, so the power supply of the motor is adjusted Frequency F can change the actual speed of the motor.
And changing the frequency must change the supply voltage, the electromagnetic relationship produced by the AC motor:
E=4.44fw?
In the formula: E-motor electromotive force
f-stator frequency
w-winding coefficient
?-Air gap main flux
When adjusting the speed of different frequency motors, we hope that the main magnetic flux ? is constant, and the u/f curve is kept constant. Therefore, when the frequency is changed, the power supply voltage also changes.
2 Principle of power saving by fan speed regulation:
Due to the complexity of the fluid inside the fan, theory alone cannot accurately calculate their performance. The operating conditions of the fan can only be calculated by means of experiments and simulations by relying on similar theories in fluid mechanics. When the similar law is applied to the same fan running at different speeds, the following formula can be obtained:
從上式可以看出，流量與轉(zhuǎn)速成正比，壓力與轉(zhuǎn)速的平方成正比，軸功率與轉(zhuǎn)速的立方成正比，所以降低轉(zhuǎn)速可以大幅度減少耗電量。風(fēng)機(jī)的節(jié)電原理就是用調(diào)速裝置來代替風(fēng)門調(diào)節(jié)流量，減少節(jié)流損失，節(jié)約電能。風(fēng)機(jī)是用來傳送氣體的機(jī)械設(shè)備，風(fēng)機(jī)是把電動機(jī)的軸功率轉(zhuǎn)變?yōu)闄C(jī)械能的一種機(jī)械，它們的啟動力矩都較小，負(fù)載輕，具有很大節(jié)能潛力。
3 改造方案：
加熱爐鼓風(fēng)機(jī)目前的控制方式主要根據(jù)加熱爐助燃風(fēng)量的需求，空氣引風(fēng)機(jī)、煤氣引風(fēng)機(jī)主要根據(jù)引風(fēng)溫度和爐膛溫度通過調(diào)整閥門開度來實現(xiàn)。由于助燃鼓風(fēng)機(jī)和引風(fēng)機(jī)工藝較為簡單，沒有必要做閉環(huán)控制，改造方案考慮在采用變頻器后保持進(jìn)風(fēng)閥全開，根據(jù)生產(chǎn)需要人工操作調(diào)節(jié)風(fēng)機(jī)轉(zhuǎn)速。系統(tǒng)可隨時隨意改變引風(fēng)量，以適應(yīng)的變化，保持風(fēng)機(jī)的正常經(jīng)濟(jì)運行，達(dá)到穩(wěn)定控制、方便操作、節(jié)約能源的目的。
此外，為了保證系統(tǒng)的可靠性，鼓風(fēng)機(jī)引風(fēng)機(jī)現(xiàn)有的控制設(shè)備和運行方式仍將保留，控制回路上設(shè)計工頻/變頻運行切換選擇，工/變頻選擇由人工切換操作，實現(xiàn)助燃離心風(fēng)機(jī)在工頻或變頻運行。因加熱爐鼓風(fēng)機(jī)為一用一備，變頻改造采用一拖二變頻控制方式，設(shè)置1#、2#風(fēng)機(jī)手動切換功能。
Main circuit diagram
In order to reduce the labor intensity of the on-duty workers, after the transformation, the start/stop, combustion/transition switching, and speed control of the combustion air blower and induced draft fan are both centralized and remote. The existing PLC computer control system is used, and the existing PLC is used. The standby point of the module increases the speed control operation function of the blower and the induced draft fan and the display function of the output frequency and output current of the inverter by modifying the program in the fuel control computer control system.
4. Analysis of running power saving effect
Take gas induced draft fan as an example
Figure: Inverter in operation
5. Other effects produced by the application of frequency converter
1 Reduced maintenance
Regardless of the process conditions after frequency conversion speed regulation, the system can be operated at any time by adjusting the rotation speed at any time. Due to the slow start and the reduction in rotation speed, the life of many parts is correspondingly extended, and the pipeline is greatly reduced. Impact, saving a lot of maintenance costs.
2 Reduced impact on the grid
After the inverter is used, the system achieves soft start. The starting current of the motor is much less than the rated current. The start time is correspondingly extended. There is no impact on the power grid, which reduces the mechanical damage of the starting machine torque to the motor and effectively extends the service life of the motor.
3 Improved working environment
Under full production process requirements, by reducing the speed of the fan, the fan's dry noise is reduced, especially when the furnace is commutated, the sudden load change causes huge dry noise, and the inverter's current limiting function reduces the fan's sudden load. The speed, the fan noise reduction is quite obvious. Greatly improved the working environment of employees.