Submerged Arc Furnace Working Principle

The submerged arc furnace is also called an electric arc furnace or resistance furnace. But what is the submerged arc furnace working principle? It is mainly used for reducing and smelting ores, carbonaceous reducing agents, solvents, and other raw materials. It mainly produces ferrosilicon, ferromanganese, ferrochrome, ferrotungsten, silicomanganese, and other ferroalloys, which are important industrial raw materials in the metallurgical industry and chemical raw materials such as calcium carbide.

The submerged arc furnace working principle is to use carbon or magnesia refractory materials as furnace lining and self-training electrodes. The electrode is inserted into the furnace charge for submerged arc operation. It is an industrial electric furnace that uses the energy and current of the electric arc to pass through the furnace charge and generates energy due to the resistance of the furnace charge to smelt metal, successively charges, intermittently discharges iron slag, and continuously operates.

A load of a submerged arc furnace transformer is continuous and stable, the impedance voltage is low, the number of voltage regulating levels is large, and the level difference is small, and the overload capacity is strong. It can be divided into on-load and off-excitation voltage regulation. Generally, the first several stages have constant capacity output and the last several stages have constant current output.

1. Structural Characteristics

The submerged arc furnace is a kind of industrial electric furnace with huge power consumption. It is mainly composed of a furnace shell, furnace cover, furnace lining, short net, water cooling system, smoke exhaust system, dust removal system, electrode shell, electrode pressure discharge and lifting system, feeding and unloading system, controller, burn through device, hydraulic system, submerged arc furnace transformer and various electrical equipment.

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, which is a large current working system, and the maximum current can reach tens of thousands of amperes. Therefore, the performance of the short network determines the performance of the submerged arc furnace. For this reason, the natural power factor of the submerged arc furnace is difficult to reach more than 0.85, and the natural power factor of most furnaces is between 0.7 and 0.8, The low power factor not only reduces the efficiency of the transformer and consumes a lot of useless work, but also imposes additional power fines by the power department. At the same time, due to the manual control of electrodes and the stacking process, the power imbalance between the three phases increases, and the maximum imbalance can reach more than 20%, which leads to low smelting efficiency and higher electricity charges. Therefore, improving the power factor of the short network and reducing the imbalance of the power grid becomes to reduce energy consumption, Effective means to improve smelting efficiency. If proper 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 more than 5%~10%.

2. Submerged Arc Furnace Working Principle

In general, in order to solve the problem of the low power factor of submerged arc furnaces, our country generally adopts the way of capacitance compensation. Usually, reactive power compensation is carried out at the high-voltage end. However, because the high-voltage end compensation cannot solve the problem of three-phase balance, and because the inductive reactance of the short network accounts for more than 70% of the inductive reactance of the whole system, the high-voltage end compensation does not achieve the goal of reducing the inductive reactance of the short network system and improving the power factor of the short network. The purpose of increasing transformer output is only meaningful to the power supply department.

Therefore, some units have also taken the measures of reactive power compensation at the same time for high and low voltage on new furnaces to solve the above problems. Compensation at the short network end can greatly improve the power factor at the short network end and reduce power consumption. In view of a large amount of reactive power consumption and imbalance of the short network at the low voltage side of the furnace transformer, and taking into account the effective improvement of the power factor, the local reactive power compensation technology transformation is technically reliable and mature, Economically speaking, input and output are in direct proportion.

The reactive power local compensation on the low-voltage side of the submerged arc furnace for the three-phase imbalance caused by the inconsistency between the reactive power consumption of the short network and its layout length has incomparable advantages in terms of improving power factor, absorbing harmonics, increasing production and reducing consumption. However, due to the high cost and the harsh working environment, service life is greatly affected. At the same time, reactive power compensation at the low voltage end of the short network also brings about an increase in harmonics. Therefore, measures must be taken to suppress the third to seventh harmonics, so as to increase investment, prolong the investment recovery period, and at the same time, the follow-up maintenance costs are high, resulting in poor comprehensive benefits. Generally, it is only applicable to new furnaces.

3. Development Trend

(1) The submerged arc furnace is developing towards high power and large scale. In order to improve thermal efficiency, improve the productivity and meet the process requirements of power centralized smelting;

(2) Low-frequency (0.3-3Hz) smelting can save and improve product quality.

(3) Smoke exhaust, dust removal, and energy recovery devices are set.

(4) The hollow electrode system is developed. Small particles of fine material can be added from the hollow electrode to save energy, save electrode consumption and stabilize the molten pool.

(5) The furnace body rotating structure is adopted.

(6) Develop a computer process software system suitable for various submerged arc furnace process requirements to guide smelting and make smelting reach the best state, so as to improve product quality, reduce energy consumption and increase output.