Main methods of ferroalloy production:
Blast furnace method – use the high temperature and reducing atmosphere of the blast furnace to reduce the alloy ore to produce ferroalloy. Such as high carbon ferromanganese.
Electrothermal process – the main method of ferroalloy production. The disadvantage of using carbon as reducing agent is that many metals are easy to form carbides with carbon and cannot produce low-carbon ferroalloys.
Metallothermic method: the chemical heat generated by the reduction reaction is used to heat the alloy and slag, so that the reaction can be carried out automatically. Common reductants include aluminum, ferrosilicon, aluminum magnesium alloy, etc., to produce very low carbon alloy.
Converter process – decarburization of high carbon alloy by blowing oxygen to produce medium and low carbon alloy.
1. Blast furnace method
The main equipment used in the blast furnace method is the blast furnace. The blast furnace process is the earliest ferroalloy production method. At present, it mainly produces high carbon ferromanganese for blast furnace. The main raw materials for blast furnace ferromanganese production are manganese ore, coke, flux, combustion supporting air or oxygen enriched air. The raw materials are loaded into the furnace from the top of the furnace. High temperature air or oxygen enriched air is blown into the furnace through the tuyere to enable coke combustion to obtain high temperature and the reducing gas to carry out reduction reaction on the ore. The melted slag and metal are accumulated at the bottom of the furnace, and slag and iron are regularly discharged through the slag hole and tap hole. With the melting, reaction and discharge of furnace charge, new furnace charge is continuously added, and the production is continuous.
The blast furnace method has the advantages of high labor productivity and low cost. However, in view of the limitations of the hearth temperature of the blast furnace. And the metal under the blast furnace bar is fully saturated with carbon. Therefore, the blast furnace method is generally only used to produce iron alloys with easily reducible elements and low-grade iron alloys, such as high carbon ferromanganese, low silicon iron, low silicon manganese, nickel iron and manganese rich slag.
2. Electric furnace method
The electric furnace method is the main method to produce ferroalloy. Its output accounts for about 4/5 of the total ferroalloy output. The main equipment used is the electric furnace.
Electric furnace is mainly divided into reduction electric furnace (submerged arc furnace) and refining furnace:
(1) Reduction electric furnace (submerged arc furnace) method. The reduction electric furnace process uses carbon as a reducing agent to reduce ores to produce ferroalloys. The furnace charge is added into the furnace and the electrode is inserted into the furnace charge, and the resistance arc heat generated by the electric arc and current passing through the furnace charge is used for arc management reduction smelting operation. The molten metal and slag gather at the bottom of the furnace and are regularly cast through the tap hole. The production process is continuous. The varieties produced by this method mainly include ferrosilicon, silicon calcium alloy, industrial silicon, high carbon ferromanganese, silicon manganese alloy, high carbon ferrochrome, silicon chromium alloy, etc.
(2) Refining furnace (electric arc furnace) method. The refining furnace process uses silicon (siliceous alloy) alloy products and relies on arc heat and silicon oxygen reaction heat for smelting. The furnace charge is fed into the furnace from the furnace top or door. The whole smelting process is divided into five processes, including arc striking, feeding, melting, refining and tapping. The production is carried out intermittently. The main products are: medium and low carbon ferromanganese, medium, low and micro carbon ferrochrome and ferrovanadium.
3. Out of furnace method (metal thermal method)
The out of furnace method uses silicon, aluminum or aluminum magnesium alloy as reducing agent and relies on the chemical heat generated by the reduction reaction to smelt. The main equipment used is the barrel furnace.
The raw materials used include concentrate, reducing agent, flux, heating agent, steel chips, iron ore, etc.
The main products are ferromolybdenum, ferrotitanium, ferroboron, energetic iron, ferrotungsten, high vanadium iron and chromium metal.
4. Oxygen converter method
The main equipment used in the oxygen converter method is the converter. According to its oxygen supply mode, there are top, bottom, side blowing and top bottom combined blowing methods. The raw materials used are liquid high carbon ferroalloy, pure oxygen, coolant and slagging materials. The liquid high carbon ferroalloy is put into the converter, and the high-pressure oxygen is blown into the converter through the oxygen gun. Decarbonization is carried out intermittently by the heat released from the oxidation reaction. The main products are medium and low carbon ferrochrome, medium and low carbon ferromanganese, etc.