Electric arc furnace is a kind of power-frequency electric furnace that uses electric arc energy to smelt metal. Electric arc furnaces used in industry can be divided into three categories: the first type is a direct heating type. The arc occurs between the special electrode rod and the smelted charge, and the charge is directly exposed to the arc heat. It was mainly used for steelmaking, and secondarily used for smelting iron, copper, refractory materials, refined molten steel, etc.
The second type is indirect heating. The arc occurs between two special electrode rods. The charge is only radiated by the arc and is used for smelting copper and copper alloys.
The third type is called submerged arc furnace, which uses ore with high resistivity as raw material, and the lower part of the electrode is generally buried in the charge during operation. The heating principle is that not only the heat flux generated by the resistance of the charge when the current passes through the charge, but also the heat generated by the arc between the electrode and the charge is used. Submerged arc furnace is a kind of electric arc furnace.
Ⅰ. properties:
1. Electric arc furnace: an electric furnace that uses the high temperature generated by the electrode arc to smelt ores and metals.
Industrial furnaces in which electric arc furnaces generate electric arc heating by metal electrodes or non-metal electrodes are called electric arc furnaces. Electric arc furnaces can be divided into three-phase electric arc furnaces, consumable electric arc furnaces, single-phase electric arc furnaces and resistance electric arc furnaces according to the arc form. The furnace body of the electric arc steelmaking furnace is composed of a furnace cover, a furnace door, a tapping trough and a furnace body, and the furnace bottom and furnace walls are built with alkaline refractory materials or acid refractory materials.
Electric arc steelmaking furnaces are divided into ordinary power electric arc furnaces, high power electric arc furnaces and ultra-high power electric arc furnaces according to the transformer capacity per ton of furnace capacity. Electric arc furnace steelmaking is to input electric energy into the electric arc steelmaking furnace through graphite electrodes, and use the arc generated between the electrode end and the charge as the heat source for steelmaking. The electric arc furnace uses electric energy as the heat source, and the atmosphere in the furnace can be adjusted, which is extremely beneficial to the smelting of steels that contain more oxidizable elements. After the invention of electric arc furnace steelmaking, it was used to smelt alloy steel and has been greatly developed.
With the improvement of electric arc furnace equipment and the improvement of smelting technology, the development of electric power industry, the cost of electric arc furnace steelmaking continues to decline. Now electric arc furnace steelmaking is used not only to produce alloy steel, but also to produce ordinary carbon steel. The proportion of output in the total steel output of major industrial countries continues to rise.
2. Submerged arc furnace: also known as electric arc furnace or resistance electric furnace. It is an industrial electric furnace with huge power consumption.
According to the structural and working characteristics of the submerged arc furnace, 70% of the system reactance of the submerged arc furnace is generated by the short network system, and the short network is a high-current working system, the maximum current can reach tens of thousands of amperes, so the short network The performance of the submerged arc furnace determines the performance of the submerged arc furnace. For this reason, the natural power factor of the submerged arc furnace is difficult to reach above 0.85. The natural power factor of most furnaces is between 0.7 and 0.8, which is relatively low. The power factor not only reduces the efficiency of the transformer, but also consumes a lot of useless work, and is charged with additional power fines by the power department. At the same time, due to the manual control of the electrodes and the stacking process, the power imbalance between the three phases increases, and the highest imbalance is The power can reach more than 20%, which leads to low smelting efficiency and higher electricity bills.
Therefore, increasing the power factor of the short network and reducing the imbalance of the grid has become an effective means to reduce energy consumption and improve smelting efficiency. If appropriate measures are taken to improve the short-network power factor, the power consumption can be reduced by 5-20%, and the output can be increased by 5%-10%.
This will bring good economic benefits to the enterprise, and the investment in transformation costs will be recovered in the short-term and in the short term.
In general, in order to solve the problem of low natural power factor of submerged arc furnaces, China mostly adopts the method of reactive power compensation on the high-voltage side to solve the problem. High-voltage compensation only improves the power factor of the high-voltage side, but due to the short-circuit system of the low-voltage side, the reactive power generated by the huge inductive reactance still flows in the short network system, and the three-phase imbalance is due to the strong phase of the short network (the short network is shorter, so the inductive reactance is smaller, so the loss is smaller, and the output is larger. Namely strong phase) and weak phase.
Therefore, high-voltage compensation cannot solve the problem of three-phase balance, nor can it offset the reactive power of the short-circuit system and improve the power factor of the low-voltage end. Because the inductive reactance of the short-network accounts for the inductive reactance of the entire system. Therefore, it cannot reduce the loss of the low-voltage side and increase the output of the transformer, but it can avoid fines, which is only meaningful for the power supply department.
Compared with high-voltage compensation, the advantages of low-voltage compensation are mainly reflected in the following aspects in addition to improving the power factor:
1) Improve the utilization of transformers and high-current lines, and increase the effective input power of smelting.
For arc smelting, the generation of reactive power is mainly caused by the arc current. Move the compensation point forward to the short network to compensate the large amount of reactive power consumption of the short network on site, increase the power supply input voltage, increase the output of the transformer, and increase the smelting effective input power.
The melting power of the material is a function of the electrode voltage and the specific resistance of the material, which can be simply expressed as P=U2/Z material. As the load capacity of the transformer is improved, the power input from the transformer to the furnace is increased, which can increase production and reduce consumption.
2) Unbalance compensation, improve the strong and weak phase conditions of the three-phase.
Because the three-phase short network layout and furnace body, charge and so on are always unbalanced, the three-phase different voltage drop and different power lead to the formation of strong phase and weak phase phenomenon. The reactive power compensation is carried out by single-phase parallel connection, the compensation capacity of each phase is adjusted comprehensively, the power density of furnace core and the uniformity of crucible are improved, the effective working voltage of three-phase electrode is consistent, the electrode voltage is balanced, the feeding of three-phase is balanced, the strong and weak phase conditions of three-phase are improved, and the purpose of increasing production and reducing consumption is achieved.
1. Electric arc furnace: an electric furnace that uses the high temperature generated by the electrode arc to smelt ores and metals.
Industrial furnaces in which electric arc furnaces generate electric arc heating by metal electrodes or non-metal electrodes are called electric arc furnaces. Electric arc furnaces can be divided into three-phase electric arc furnaces, consumable electric arc furnaces, single-phase electric arc furnaces and resistance electric arc furnaces according to the arc form. The furnace body of the electric arc steelmaking furnace is composed of a furnace cover, a furnace door, a tapping trough and a furnace body, and the furnace bottom and furnace walls are built with alkaline refractory materials or acid refractory materials.
Electric arc steelmaking furnaces are divided into ordinary power electric arc furnaces, high power electric arc furnaces and ultra-high power electric arc furnaces according to the transformer capacity per ton of furnace capacity. Electric arc furnace steelmaking is to input electric energy into the electric arc steelmaking furnace through graphite electrodes, and use the arc generated between the electrode end and the charge as the heat source for steelmaking. The electric arc furnace uses electric energy as the heat source, and the atmosphere in the furnace can be adjusted, which is extremely beneficial to the smelting of steels that contain more oxidizable elements. After the invention of electric arc furnace steelmaking, it was used to smelt alloy steel and has been greatly developed.
With the improvement of electric arc furnace equipment and the improvement of smelting technology, the development of electric power industry, the cost of electric arc furnace steelmaking continues to decline. Now electric arc furnace steelmaking is used not only to produce alloy steel, but also to produce ordinary carbon steel. The proportion of output in the total steel output of major industrial countries continues to rise.
2. Submerged arc furnace: also known as electric arc furnace or resistance electric furnace. It is an industrial electric furnace with huge power consumption.
According to the structural and working characteristics of the submerged arc furnace, 70% of the system reactance of the submerged arc furnace is generated by the short network system, and the short network is a high-current working system, the maximum current can reach tens of thousands of amperes, so the short network The performance of the submerged arc furnace determines the performance of the submerged arc furnace. For this reason, the natural power factor of the submerged arc furnace is difficult to reach above 0.85. The natural power factor of most furnaces is between 0.7 and 0.8, which is relatively low. The power factor not only reduces the efficiency of the transformer, but also consumes a lot of useless work, and is charged with additional power fines by the power department. At the same time, due to the manual control of the electrodes and the stacking process, the power imbalance between the three phases increases, and the highest imbalance is The power can reach more than 20%, which leads to low smelting efficiency and higher electricity bills.
Therefore, increasing the power factor of the short network and reducing the imbalance of the grid has become an effective means to reduce energy consumption and improve smelting efficiency. If appropriate measures are taken to improve the short-network power factor, the power consumption can be reduced by 5-20%, and the output can be increased by 5%-10%.
This will bring good economic benefits to the enterprise, and the investment in transformation costs will be recovered in the short-term and in the short term.
In general, in order to solve the problem of low natural power factor of submerged arc furnaces, China mostly adopts the method of reactive power compensation on the high-voltage side to solve the problem. High-voltage compensation only improves the power factor of the high-voltage side, but due to the short-circuit system of the low-voltage side, the reactive power generated by the huge inductive reactance still flows in the short network system, and the three-phase imbalance is due to the strong phase of the short network (the short network is shorter, so the inductive reactance is smaller, so the loss is smaller, and the output is larger. Namely strong phase) and weak phase.
Therefore, high-voltage compensation cannot solve the problem of three-phase balance, nor can it offset the reactive power of the short-circuit system and improve the power factor of the low-voltage end. Because the inductive reactance of the short-network accounts for the inductive reactance of the entire system. Therefore, it cannot reduce the loss of the low-voltage side and increase the output of the transformer, but it can avoid fines, which is only meaningful for the power supply department.
Compared with high-voltage compensation, the advantages of low-voltage compensation are mainly reflected in the following aspects in addition to improving the power factor:
1) Improve the utilization of transformers and high-current lines, and increase the effective input power of smelting.
For arc smelting, the generation of reactive power is mainly caused by the arc current. Move the compensation point forward to the short network to compensate the large amount of reactive power consumption of the short network on site, increase the power supply input voltage, increase the output of the transformer, and increase the smelting effective input power.
The melting power of the material is a function of the electrode voltage and the specific resistance of the material, which can be simply expressed as P=U2/Z material. As the load capacity of the transformer is improved, the power input from the transformer to the furnace is increased, which can increase production and reduce consumption.
2) Unbalance compensation, improve the strong and weak phase conditions of the three-phase.
Because the three-phase short network layout and furnace body, charge and so on are always unbalanced, the three-phase different voltage drop and different power lead to the formation of strong phase and weak phase phenomenon. The reactive power compensation is carried out by single-phase parallel connection, the compensation capacity of each phase is adjusted comprehensively, the power density of furnace core and the uniformity of crucible are improved, the effective working voltage of three-phase electrode is consistent, the electrode voltage is balanced, the feeding of three-phase is balanced, the strong and weak phase conditions of three-phase are improved, and the purpose of increasing production and reducing consumption is achieved.
At the same time, the three-phase unbalance phenomenon is improved, the working environment of furnace is improved, and the service life of furnace is prolonged.
3) Reduce high-order harmonics, reduce the harm of harmonics to the entire power supply equipment, and reduce additional losses of transformers and networks.
4) Improved power quality, improved system electrical parameters, and improved product quality. The figure below reflects the flow direction of reactive power during high-pressure compensation and low-pressure compensation. It can be clearly seen from the figure that the high voltage compensation cannot reduce the loss and increase the output of the transformer.
However, due to a large number of switching switches with traditional compensation switching technology (such as the use of AC contactor switching), the cost is high, and the service life is greatly affected due to the harsh working environment. According to survey statistics, the existing ones use traditional The low-voltage compensation service life of the switching method is difficult to exceed one year, so it brings a large amount of maintenance to the enterprise, and the investment recovery period is prolonged. Due to the high follow-up maintenance cost, the overall benefit is not good.
BWKN-3500 reactive power compensation controller (special type for submerged arc furnace short network), a reactive power compensation controller specially developed and designed for submerged arc furnace system (submerged arc furnace short network) to adapt to the working characteristics of submerged arc furnace Special type), the controller has the ideal function of improving power quality, mainly has the functions of improving the power factor of the submerged arc furnace, saving energy, providing voltage support, and reducing flicker. The controller has the following salient features:
▲Compensation for the three phases separately to reduce the three-phase imbalance and effectively increase production and reduce consumption.
▲ Greatly improve voltage sag and flicker.
▲Achieve free switching at any time.
▲High reliability, maintenance-free and unattended.
▲Multiple protection design avoids damage to capacitors and electronic switches to the greatest extent. (Developed according to different customers)
▲Significantly improve the utilization rate of the power supply system.
▲Main technical parameters: the main basis of the controller
Design specification: DL/T597-1996; rated voltage: 220V; fundamental frequency: 50Hz; controlled physical quantity: reactive power Q; power factor COSΦ; reactive power compensation capacity single channel setting value: 0---9999K VAR working system: Continuous work; Ambient temperature: -5℃～+70℃; Relative humidity: daily average not more than 95%, monthly average not more than 90% (indoors), non-condensing; compensation method: phase separation and grading compensation. (Can be customized according to customer needs)
▲Performance characteristics can be divided into phases, grades, cycles, electronic switch switching; phase separation and graded compensation can be used. Equipped with complete protection functions; automatic control of switching, device operation without manual intervention, safe and efficient.
Ⅱ. Features:
1. Electric arc furnace: The electric arc furnace is more flexible than other steelmaking furnaces. It can effectively remove impurities such as sulfur and phosphorus. The furnace temperature is easy to control, and the equipment occupies a small area. It is suitable for melting high-quality alloy steel.
2. Submerged arc furnace: Its working feature is to use carbonaceous or magnesia refractory materials as the furnace lining and self-cultivation electrodes. The electrode is inserted into the furnace charge for submerged arc operation. It uses the energy and current of the electric arc to pass through the charge. The energy is generated by the charge resistance to smelt the metal. It is an industrial electric furnace with continuous feeding and intermittent tapping of iron slag.
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3) Reduce high-order harmonics, reduce the harm of harmonics to the entire power supply equipment, and reduce additional losses of transformers and networks.
4) Improved power quality, improved system electrical parameters, and improved product quality. The figure below reflects the flow direction of reactive power during high-pressure compensation and low-pressure compensation. It can be clearly seen from the figure that the high voltage compensation cannot reduce the loss and increase the output of the transformer.
However, due to a large number of switching switches with traditional compensation switching technology (such as the use of AC contactor switching), the cost is high, and the service life is greatly affected due to the harsh working environment. According to survey statistics, the existing ones use traditional The low-voltage compensation service life of the switching method is difficult to exceed one year, so it brings a large amount of maintenance to the enterprise, and the investment recovery period is prolonged. Due to the high follow-up maintenance cost, the overall benefit is not good.
BWKN-3500 reactive power compensation controller (special type for submerged arc furnace short network), a reactive power compensation controller specially developed and designed for submerged arc furnace system (submerged arc furnace short network) to adapt to the working characteristics of submerged arc furnace Special type), the controller has the ideal function of improving power quality, mainly has the functions of improving the power factor of the submerged arc furnace, saving energy, providing voltage support, and reducing flicker. The controller has the following salient features:
▲Compensation for the three phases separately to reduce the three-phase imbalance and effectively increase production and reduce consumption.
▲ Greatly improve voltage sag and flicker.
▲Achieve free switching at any time.
▲High reliability, maintenance-free and unattended.
▲Multiple protection design avoids damage to capacitors and electronic switches to the greatest extent. (Developed according to different customers)
▲Significantly improve the utilization rate of the power supply system.
▲Main technical parameters: the main basis of the controller
Design specification: DL/T597-1996; rated voltage: 220V; fundamental frequency: 50Hz; controlled physical quantity: reactive power Q; power factor COSΦ; reactive power compensation capacity single channel setting value: 0---9999K VAR working system: Continuous work; Ambient temperature: -5℃～+70℃; Relative humidity: daily average not more than 95%, monthly average not more than 90% (indoors), non-condensing; compensation method: phase separation and grading compensation. (Can be customized according to customer needs)
▲Performance characteristics can be divided into phases, grades, cycles, electronic switch switching; phase separation and graded compensation can be used. Equipped with complete protection functions; automatic control of switching, device operation without manual intervention, safe and efficient.
Ⅱ. Features:
1. Electric arc furnace: The electric arc furnace is more flexible than other steelmaking furnaces. It can effectively remove impurities such as sulfur and phosphorus. The furnace temperature is easy to control, and the equipment occupies a small area. It is suitable for melting high-quality alloy steel.
2. Submerged arc furnace: Its working feature is to use carbonaceous or magnesia refractory materials as the furnace lining and self-cultivation electrodes. The electrode is inserted into the furnace charge for submerged arc operation. It uses the energy and current of the electric arc to pass through the charge. The energy is generated by the charge resistance to smelt the metal. It is an industrial electric furnace with continuous feeding and intermittent tapping of iron slag.
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