How Does a Submerged Arc Furnace Work ？

How does a submerged arc furnace work ?

First of all, we should understand the submerged arc furnace.

Submerged arc furnaces is a kind of complex electro-metallurgical equipment, which consists of electric furnace body, furnace transformer, high current conductor (short network), electrode system, SAF charging system, cooling system, high and low voltage power distribution system, monitoring and automation It is composed of system, iron tapping and slag tapping system, smoke exhaust and dust removal system.

The basic principle of submerged arc furnace production is based on the thermodynamics of selective redox reaction, the essence of which is that the oxides of the desired elements react with the reducing agent to form the oxides of the desired elements and the main elements in the reducing agent. The varieties of products smelted in submerged arc furnaces are very complex, and the smelting methods are also relatively diverse. But fundamentally, SAF smelting is a redox process in which the desired element is reduced from the ore containing the desired element oxide within a certain temperature range by using an appropriate reducing agent.

The high-voltage electric energy provided by the power grid is converted into low-voltage and high-current through the special transformer used in the submerged arc furnaces, and the current is sent to the electrode through the high-current conductor, and is input into the furnace through the carbon electrode, generating resistance heat and heat between the charges around the electrode. The arc heat generated at the end of the electrode converts the electrical energy into thermal energy, thereby forming a high temperature reaction zone in the furnace body to carry out the reduction reaction of the metal oxide ore.

Usually, carbonaceous reducing agents such as coke are used to continuously add coke and reduced metal oxide ore raw materials into the furnace. The reduction reaction in the reaction zone is continuously carried out, and the obtained liquid products are accumulated in the molten pool. It is released, and the molten metal is poured and refined to obtain an alloy product, and the slag is water-quenched or poured for reuse.

Structural Characteristics of Submerged Arc Furnace

When producing ferroalloys in submerged arc furnaces, most of them use coke as a reducing agent, and use different raw materials according to different production varieties. and other series of ferroalloy products.

When the submerged arc furnace produces calcium carbide, coke is still used as the reducing agent, calcium oxide (lime) is used as the raw material, and calcium carbide (the main component is calcium carbide) is obtained through smelting in the furnace. The SAF uses vanadium titano-magnetite as raw material, and when coal is used as the reducing agent, the titanium slag is obtained through the furnace smelting, and the vanadium-containing molten iron and other products are obtained.

Therefore, submerged arc furnace is a smelting equipment covering ferroalloys, chemical industry, ferrous metals, non-ferrous metals and other industries.

How does a submerged arc furnace work ?

When smelting in submerged arc furnaces: after the qualified silica, reducing agent and steel scrap are proportioned by electronic scale, the weighed charge is poured into the hopper → sent by belt or inclined bridge material truck

Into the furnace top silo → According to the demand of the charge, the charge can be directly added to the furnace from the material pipe connected under the silo (or added to the furnace with a feeder), and the small furnace usually sends the charge to the operation platform, Manually added to the furnace.

The material surface of the furnace mouth should maintain a certain shape, the electrodes should be in the shape of a wide and flat cone, and the height of the cone should be 200-300mm. In order to adapt to the characteristics of concentrated heat and fast chemical materials in this area.

Feeding can be done with less work addition or batch concentrated feeding, and the deviation of feed should be corrected in time.

In order to maintain good air permeability in the furnace, it is necessary to carry out dazzling and pounding in time. It should be dazzled with round steel in areas with poor air permeability (weak fire, hard material surface), and areas with severe "stab fire" (furnace gas is ejected from around the electrode with great pressure), or according to furnace conditions. The blackened area or "stab fire" area of ​​the face and the lower part of the cone is stoked. Dazzling to be diligent, according to furnace conditions.

Small pounding furnace can be carried out according to furnace conditions. The large pounding furnace is generally carried out after the iron is tapped.

When the molten iron in the furnace accumulates to a certain amount, preparations for tapping should be made.

Before tapping, tools and mud balls for opening and blocking furnace eyes should be prepared, and the ladle should be checked.

When tapping, first use round steel to remove the residual flooding, residual iron and mud balls around the furnace hole with round steel, and then use round steel to open the furnace hole at the top of the center line of the furnace hole. When the tapping hole is difficult to open, it can be used The round steel is connected to the burn-through device and boiled.

The furnace eye should be large on the outside and small on the inside, in a round shape. After the tap hole is opened, the size of the iron flow should be controlled to be appropriate, and the tap time should be controlled within 15 minutes.

After tapping, clean the tap hole, and use plugging material to block the tap hole.

After the iron is cast, it should be poured immediately to avoid cooling. When ferrosilicon is condensed, silicon crystallizes first, and it floats up because of its low density, and iron silicide with high density sinks.

In order to reduce segregation, the pouring temperature of molten iron can be reduced, the thickness of the iron ingot can be reduced, and the cooling rate of the iron ingot can be accelerated. Usually, a shallow ingot mold with a depth of less than 100mm is used when pouring FeSi75. After pouring, when the alloy ingot is condensed into cherry red, the alloy is lifted from the ingot mold with a crane and placed on a cooling table to cool. The cooled alloy ingots are broken, the residues are removed, and the ingots are packaged and stored.

The above is the general content of " How Does a Submerged Arc Furnace Work ". To learn more about submerged arc furnaces, electric arc furnaces, ladle refining furnaces, melting furnaces, etc., please continue to follow my blog.

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