Production Methods of Ferroalloys
There are many production methods of ferroalloys, most of which are produced by pyrometallurgy.
The production methods of ferroalloys are mainly divided into the following according to the smelting equipment, operation methods, and heat sources used:
I. Classification by Production Equipment
According to production equipment, it can be divided into blast furnace method, electric furnace method, out-of-furnace method, converter method, and vacuum resistance furnace method.
1. Electric Furnace Method.
The electric furnace is the main method to produce ferroalloys, and its output accounts for about 80% of all ferroalloys.
2. Blast Furnace Method.
The main equipment used in the blast furnace method is the blast furnace. The blast furnace method is the earliest ferroalloy production method. The blast furnace process has the advantages of high labor productivity and low cost. However, in view of the limitation of the temperature of the blast furnace hearth and the fact that the metal is fully saturated with carbon during the smelting process of the blast furnace, the blast furnace method is generally only used to produce ferroalloys with reducing elements and low-grade ferroalloys.
3. Off-furnace Method (Metal Thermal Method).
The out-of-furnace method uses silicon, aluminum, or aluminum-magnesium alloy as a reducing agents and relies on chemical heat generated by reduction reaction to smelt. The main equipment used is the cylindrical furnace. Raw materials used include concentrate, reducing agent, flux, heating agent, steel chips, iron ore, etc.
4. Oxygen Converter Method.
The main equipment used in the oxygen converter method is the converter. According to the oxygen supply mode, there are top-bottom, side-blowing, and top-bottom composite blowing methods. The raw materials used are liquid high-carbon ferroalloy, pure oxygen, coolant and slag-making materials, etc. The liquid high-carbon ferroalloy is added to the converter, and the high-pressure oxygen is blown into the furnace through the oxygen gun. The production is carried out intermittently depending on the heat from the oxidation reaction.
5. Vacuum Resistance Furnace Method.
Vacuum resistance furnace is used to produce micro-carbon ferrochromium, ferrochromium nitride, and ferromanganese nitride products with very low carbon content. The main equipment is vacuum resistance furnace.
II. Classification by Heat Source
According to different heat sources, it can be divided into carbon thermal method, electrothermal method, electro-silicon thermal method, and metal thermal method.
1. Carbon Thermal Method.
The heat source of the carbothermal smelting process is mainly the combustion heat of coke. Coke is used as reducing agent to reduce oxides in ores. The production by this method is carried out continuously in the blast furnace.
2. Electrothermal Method.
Electric energy is the main heat source in the electrothermal smelting process. The oxides in ores are reduced with carbon reducing agent and the continuous operation process is adopted in the reduction furnace.
3. Electro-silicothermal Method.
Electric energy is the main heat source in the smelting process of electro-silicon thermal process, while the rest is the heat released when silicon is oxidized. Silicon (ferrosilicon, manganese-silicon alloy and silicon-chromium alloy), as reducing agent, is used to reduce oxides in ores. Production is an intermittent operation in a refining furnace.
4. Metal Thermal Method.
The heat source of the metallurgical process is mainly the heat emitted by metal reducing agents such as silicon and aluminium when reducing oxides in concentrates. The production is carried out in a tubular furnace in an intermittent manner.
III. Classification by Operation Method and Process
According to the characteristics of production and operation process, it can be divided into flux method, solvent-free method, slag-free method, slag-free method and continuous and intermittent smelting method.
1. Flux Method.
Ferrous alloy smelting by flux method uses carbon material, silicon or other metal as reducing agent. Slag-making material should be added to adjust composition and properties of slag during production. If alkaline slag is used, high carbon ferromanganese can be produced.
2. Flux-free Method.
In general, carbon material is used as reducing agent in the production of ferroalloys without flux. Slag composition and properties are not regulated by adding slag-making material in the production. If high quality manganese ore is used, acid slag is used to produce high carbon ferromanganese and low phosphorus and rich manganese slag is obtained.
3. Sludge-free Process.
Sludge-free smelting of ferrous alloys is a continuous smelting process in a reduction furnace using carbon reducing agent, silica or remanufactured alloys as raw materials. The products include ferrosilicon, industrial silicon, silicon-chromium alloys, etc.
4. Sludge Method.
Slag smelting of ferroalloys is to produce ferroalloys in reducing or refining electric furnaces by selecting reasonable slag type system and alkalinity. The slag-iron ratio is affected by different varieties and corresponding raw material conditions. Products include high carbon ferromanganese, manganese silicon alloy, high carbon ferrochromium, etc.
5. Continuous Smelting.
Continuous smelting method is to continuously charge the furnace according to the falling charge level at the furnace mouth, while the alloy and slag accumulated in the furnace pool are discharged regularly. With submerged arc reduction smelting, the operating power is almost equalized and stable.
6. Intermittent Smelting.
Intermittent smelting is a process in which charge is concentrated or batched into the furnace. It is generally divided into two stages: melting and refining, in which the electrode is buried in the furnace charge.
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