Submerged arc furnace is also called electric arc furnace or resistance electric furnace.
It is mainly used to reduce raw materials such as smelting ores, carbonaceous reducing agents and solvents. It mainly produces ferrosilicon, ferromanganese, ferrochromium, tungsten, silicomanganese and other ferroalloys, which are important industrial raw materials in the metallurgical industry and calcium carbide and other chemical raw materials.
Its working characteristic is to use carbonaceous or magnesia refractory materials as 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. 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.
Submerged arc furnace is a kind of industrial electric furnace that consumes huge power. Mainly consists of furnace shell, furnace cover, furnace lining, short net, water cooling system, smoke exhaust system, dust removal system, electrode shell, electrode pressure release and lifting system, loading and unloading system, controller, burning through device, hydraulic system, submerged arc furnace Transformers and various electrical equipment, etc.
According to the structural characteristics 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, 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 maximum 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 have become effective means to reduce energy consumption and improve smelting efficiency. If appropriate measures are taken to improve the short-network power factor, the following effects can be achieved:
(1) Reduce power consumption by 5-20%
(2) Increase output 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.
The loss of the submerged arc furnace system is shown in the figure below. The loss of the short network accounts for more than 70% of the loss of the system itself. The short network is a system that works with high current. The maximum current can reach tens of thousands of amperes. Therefore, the performance of the short network is very good. To a large extent determines the performance of submerged arc furnace
If appropriate measures are taken to increase the power factor of the short network and improve the electrode imbalance, the following effects will be achieved:
A. Reduce production power consumption Reduce production power consumption Reduce production power consumption Reduce production power consumption 3%～～～～6%;
B. Increasing product output, increasing product output, increasing product output, increasing product output by 5%～～～15%.
So as to bring good economic benefits to the enterprise, and the investment in transformation costs can be recovered in the short-term and the comprehensive benefits created. In general, in order to solve the problem of the low natural power factor of submerged arc furnaces, my country mostly adopts the method of reactive power compensation at the high-voltage side to solve the problem. 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, and it also fails to 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-circuit accounts for the inductive reactance of the entire system Therefore, the loss of the low-voltage side cannot be reduced, nor can the output of the transformer be increased, but fines can be avoided, 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. Regarding arc smelting, the generation of reactive power is mainly caused by 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 input voltage of the power supply, 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, and the output is increased and the consumption is reduced. 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, etc. are always unbalanced, the different voltage drops and different powers of the three phases lead to the formation of strong and weak phase phenomena. Single-phase parallel connection is adopted for reactive power compensation, the compensation capacity of each phase is comprehensively adjusted, the power density of the furnace core and the uniformity of the crucible are improved, the effective working voltage of the three-phase electrode is consistent, the electrode voltage is balanced, the three-phase feed is balanced, and the three The strong and weak phases of the phases achieve the purpose of increasing production and reducing consumption. At the same time, the three-phase imbalance phenomenon is improved, the working environment of the furnace is improved, and the service life of the furnace is prolonged. 3) Reduce the high-order harmonics, reduce the harm of harmonics to the entire power supply equipment, and reduce the additional losses of the transformer and the network. 4). Improved power quality, improved system electrical parameters, and improved product quality. The following figure 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 the 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 way switching is difficult to exceed one year, so it brings a large amount of maintenance to the enterprise, and the investment recovery cycle 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), specially developed and designed to adapt to the working characteristics of submerged arc furnace Special type), the controller has the ideal function of improving the power quality, mainly has the functions of improving the power factor of the submerged arc furnace, saving energy, providing voltage support, reducing flicker and so on. The controller has the following salient features:
▲Compensation for three-phase separately, reduces the three-phase unbalance degree, effectively increases production and reduces consumption.
▲Greatly improve voltage drop and flicker.
▲Achieve free switching at any time.
▲High reliability, maintenance-free and unattended.
▲Multiple protection design avoids the damage of 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; Control physical quantity: reactive power Q; power factor COSΦ; single set value of reactive power compensation capacity: 0—9999KVAR 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 It can be divided into phases, graded, cycled, and switched on and off by electronic switches; it can be divided into phases and graded compensation. Equipped with complete protection functions; automatic control of switching, device operation without manual intervention, safe and efficient.