Submerged Arc Melting Furnace Principle

 

Submerged Arc Melting Furnace Principle

A submerged arc melting furnace is also called an electric arc furnace or electric resistance furnace. 

Submerged arc melting furnaces are mainly used for reducing smelting ores, carbonaceous reducing agents and solvents, and other raw materials. 

It mainly produces ferrosilicon, ferromanganese, ferrochromium, ferrotungsten, silicon-manganese alloy, and other ferroalloys, which are important industrial raw materials in the metallurgical industry and chemical raw materials such as calcium carbide. 

The submerged arc melting furnace working principle is to use carbonaceous or magnesia refractory material as furnace lining and use self-cultivation electrodes. 

The electrode is inserted into the charge for submerged arc operation, using the energy and current of the arc to pass through the charge, and generating energy due to the resistance of the charge to smelt metal, feeding continuously, intermittently tapping iron slag, an industrial electric furnace with continuous action.

Submerged Arc Melting Furnace Principle & Application

Category	Main raw materials	Manufactured products	Reflect temperature 0℃	Power consumption  KW*h/t
Ferroalloy Ferrosilicon Furnace (45%)Ferrosilicate	Scrap iron, coke, ferrosilicon	Ferrosilicon	1550-1770	2100-5500
Ferroalloy Ferrosilicon Furnace (75%)Ferrosilicate	Scrap iron, coke, ferrosilicon	Ferrosilicon	1550-1770	8000-11000
Ferromanganese furnace	Manganese ore, waste iron, coke, lime	Ferromanganese	1500-1400	2400-4000
Ferro-chromium furnace	Chromium ore, silica, coke	Ferric chromium	1600-1750	3200-6000
Ferrous Tungsten Furnace	Tungsten crystal ore, coke	Ferro-Tungsten	2400-2900	3000-5000
Silicon chromium furnace	Ferric chromium, silica, coke	Silicon chromium alloy	1600-1750	3500-6500
Silicon Manganese Furnace	Manganese ore, silica, scrap iron, coke	Silicon-Manganese Alloy	1350-1400	3500-4000
Steel-making electric furnace iron	Ores, coke	Pig iron	1500-1600	1800-2500
Calcium carbide furnace	Limestone, coke	Calcium	1900-2000	1900-3000
Boron Carbide Furnace	Boron oxide, coke	Boron carbide	1800-2500	11000-20000

   

Industrial waste heat refers to a large amount of waste heat generated in industrial production lines of steel, petrochemical, building materials, and non-ferrous metals. 

Waste heat power generation technology refers to the technology that uses the high-grade heat of the enterprise to recover and converts it into electricity for the enterprise's own use. my country has always regarded the use of waste heat power generation as one of the important measures to save energy and reduce consumption and achieve cyclic development and has given strong support. 

At present, the application field of waste heat power generation technology in my country continues to expand, but in the field of ferroalloy and calcium carbide, flue gas waste heat and other comprehensive waste heat recovery power generation technology are still relatively lacking.

A few days ago, a seminar on waste heat recovery and utilization of submerged arc furnace power generation technology was held in Beijing. Leaders and experts from the National Energy Office, General Iron and Steel Research Institute, National Development and Reform Commission, and various industry associations discussed the development of Xi'an Rich Energy Engineering Technology Co., Ltd., Waste heat power generation technology for ferroalloy, calcium carbide, and other fields. 

The waste heat recovery power generation in the fields of ferroalloy and calcium carbide has not been paid much attention because of its large volume and wide range. This technology fills this gap, improves the waste heat recovery rate, and reduces the cost.

At present, energy conservation and emission reduction have become a basic national policy in my country, and the ferroalloy industry is a typical high-energy-consuming industry. The promotion of waste heat recovery power generation technology in this industry is conducive to reducing corporate energy consumption and improving energy utilization efficiency. 

Not long ago, the three ministries and commissions of the state issued a document to cancel the preferential electricity price for high-energy-consuming enterprises, and the preferential electricity price for the ferroalloy industry has been canceled since October 20, 2007. 

With the increase in electricity cost, the investment recovery period of waste heat recovery power generation projects of ferroalloy enterprises will be further shortened, and this technology will have better development prospects.

Hani is the one-stop supplier able to design, manufacture, install and commission your melt shop and hot rolling mill plant from A to Z.

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Explain Submerged Arc Furnace's Furnace Refractory Requirements and Selection

Explain Submerged Arc Furnace's Furnace Refractory Requirements and Selection

The submerged arc furnace is used for the reduction and smelting of metal oxide ore, so it is also called the submerged arc reduction electric furnace.

When the submerged arc furnace is used to produce ferroalloy, it is called a ferroalloy furnace: when it is used to produce calcium carbide, it is called a calcium carbide furnace: when it is used to produce yellow phosphorus, it is called a yellow phosphorus furnace: when it is used to produce matte, it is called matte furnace: it is used for ferroalloy refining It is called submerged thermal refining furnace: when it is used to melt the pre-reduced charge and separate the metal from the slag, it is called a melting furnace.

For the submerged arc furnace, the refractory masonry is the furnace lining. Because the molten pool of the submerged arc furnace not only withstands strong high-temperature action but also is eroded and mechanically scoured by the charge, high-temperature furnace gas, molten iron,, and high-temperature slag, specific refractory materials must be selected.

Requirements for refractory materials: high refractoriness, large changes in shape and volume at high temperature, high-temperature strength, good slag resistance, and good chemical stability at high temperature, various refractory materials should keep their appearance clean and complete in structure, the corner corrugation has no defects, and the surface has no cracks

In the masonry of the submerged arc furnace, the refractory materials for the submerged arc furnace are mainly made of refractory bricks, and the refractory castables are the auxiliary masonry configuration. The choice of material is as follows:

1. Carbon brick

Carbon brick is a kind of carbon material. It is made with crushed coke and anthracite. Its specifications are: section 400mm×400mm (the allowable error is ±30mm), length is 800~1600mm (the allowable error is ±5mm);

The advantages of carbon bricks are high refractoriness, strong thermal shock resistance, high compressive strength; good stability, especially volume stability, and good slag resistance. However, it is easy to be oxidized at high temperatures, and the oxidation speed will increase with the increase in temperature.

Therefore, the carbon material cannot come into contact with gases such as air and water vapor at high temperatures. Carbon materials have high thermal conductivity and poor thermal insulation performance. In the submerged arc furnace, carbon bricks can be used as the lining material for all varieties that are not afraid of carburizing in smelting, and self-baking carbon bricks are used in the submerged arc furnace.

2. Magnesia brick for submerged arc furnace

The main component of magnesia brick is magnesia, its refractoriness is above 2273K, and its alkali resistance is very strong; but its softening point under load is low, and its thermal shock resistance is poor. Most of the refining furnaces are smelted in an alkaline environment, and alkaline refractory materials that resist alkaline corrosion should be selected, such as magnesia bricks as linings.

3. Clay bricks

Clay bricks are weakly acidic refractory materials, which can resist the erosion of acid slag, and refractory clay bricks cannot be used at high temperatures.

In summary, the selection of refractory materials for submerged arc furnaces should be professionally configured according to the actual smelting environment and smelting raw materials. High-alumina bricks can also be used to replace clay bricks in the molten pool of submerged arc furnaces. In terms of performance, high-alumina bricks have more advantages. Among the unshaped refractories, cold ramming pastes and high-alumina castables are the main ones.

Hani is the one-stop supplier able to design, manufacture, install and commission your melt shop and hot rolling mill plant from A to Z.

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Transformers for Electric Arc Furnaces (Metal Furnaces)

Transformers for Electric Arc Furnaces (Metal Furnaces)

In this chapter, we will discuss a special application of transformers, which are used in furnaces and whose purpose is to create arcs in alternating current.

An electric arc furnace (metal furnace) melts the metal in the furnace by creating an electric arc between the feed plates of the furnace directly through the material we want to melt. The enormous heat generated caused the entire contents of the oven to melt. These furnaces are characterized by very high currents, ranging from 100 kA to 300 kA, and relatively low voltages of 150 to 2,500 volts. Due to the high power required for furnaces from 10MVA to 100MVA and even higher, and the nature of the load, transformers are fed from high voltage networks or high voltages very close to 1000MV to ensure that disturbances in the network during use remain acceptable according to the standard Level.

Furnace duty cycles vary widely depending on furnace size and job requirements, with typical duty cycles in the 3-8 hour range. The first step in the process is the melting process. During this process, the metal enters the furnace in a solid state, so it takes a lot of energy to melt it and turn it into a liquid. The second part of the process is called the distillation step. During this phase, the temperature in the oven remains constant and the energy provided is only used to compensate for heat loss in the oven. The melting stage is characterized by large current fluctuations caused by the instability of the arc due to the movement of the material in the furnace and its properties, and this stage continues until all materials in the furnace are homogeneously melted. During the distillation stage, the current fluctuations are much smaller because all the material is melted. Current fluctuations in the melting phase are controlled to some extent by furnace design, transformer, and load type. For example, finely shredded scrap produces much less vibration than larger, non-uniform scrap.

In order to characterize the transformer, it is necessary to understand how the furnace works and its operating cycle. The effect of peak loads during the melting phase must be carefully considered when selecting a suitable transformer, assuming that the load will be significantly reduced during the refining phase. At the beginning of a melting cycle, the load on the transformer can be as high as twice its normal and continuous load.

Because the low-voltage side windings of transformers designed for furnaces require high currents, engineering problems caused by the rapidly changing nature of the load must be overcome. The cross-sectional area of ​​the winding on the medium and low voltage sides of the transformer should be large, and the number of windings required should be small. In most cases, the coils on the secondary side are delta-connected to reduce phase currents and achieve good electromagnetic balance and high mechanical strength. Low-voltage coils are usually constructed of pairs of parallel disks mounted outside the transformer to help cool them. Since these types of transformers generate enormous amounts of heat, the cooling method for these transformers is OFWF, which means circulating the oil and cooling it using a water-injected heat exchanger.

A high-impedance transformer design helps limit the power of the current surge and minimize its impact on the supply network, but too high a value will reduce the short-circuit power of the furnace, thereby increasing the cycle time of the melt. However, the transformer coils are repeatedly subjected to severe mechanical shocks during melting, thus requiring particularly durable mechanical reinforcement of the coil structure. Care must be taken to maintain the space between the coils and the support points and secure them securely to ensure that constant shock to them does not cause them to loosen or move.

Radial support for the coils is provided by insulating paper holding the conductors, and the coils themselves are made of a silver-copper alloy designed to provide maximum strength and stiffness. The transformer tank must also be reinforced to provide maximum stiffness and withstand the electrical power generated in the transformer.

Another furnace characteristic that transformer designers must be aware of is the widely varying voltage drop during the melting phase. In order to maintain an active arc that does not subside during the melting stage, a voltage much greater than that required for the refining stage is required. Achieving balance requires precise control of the furnace current. Therefore, it is important to control the voltage carefully.

Another problem faced by transformer designers is that in order to produce good current control on the low voltage side, a step change is required on the high voltage side of the transformer, so the transformer must include a step change in the load that involves a large number of steps.

The specification of step converters for transformers for electric arc furnaces are particularly demanding in terms of current, the number of steps, the large number of operations, and response speed. Therefore, the tap-changer must have very high reliability to ensure a fast response in variable load or overload situations. Shifters require a lot of maintenance and frequent maintenance to ensure their integrity for long working hours in these tough working conditions.

Hani is the one-stop supplier able to design, manufacture, install and commission your melt shop and hot rolling mill plant from A to Z.

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