1. Iron ore ingredients.
The iron content of iron ore is different, so is the impurity content. If the material is changed, it will cause the instability of the blast furnace smelting system, affect the output and even cause accidents. Therefore, iron ores of different origins and grades are evenly mixed in proportion to ensure the stability of iron ore composition.
At the same time, lime and pulverized coal are added for sintering. Note that lime is added at this time, not the blast furnace side or limestone.
2. Sintering.
The unsintered fine iron ore cannot directly enter the blast furnace. The pulverized coal in the mixed iron ore is ignited by the gas spray gun on the sintering machine. After the pulverized coal is burnt out, not only the iron ore can be caked by heat, but also a large number of holes will be produced in the sintered ore, which will increase the contact surface and improve the reduction reaction speed.
3. Blast furnace reduction.
Sinter, coke and pellets are added into the blast furnace in proportion. Preheated hot air (800- 1000℃) is sent to the tuyere below the blast furnace, and carbon monoxide and hydrogen generated by the reaction of coke and hot air at high temperature will reduce iron ore to iron at high temperature. Iron absorbs carbon to form pig iron with low melting point, and finally molten iron is discharged from the taphole.
In order to save coke, some blast furnaces also inject auxiliary fuels such as pulverized coal, heavy oil and natural gas.
People who know the structure of blast furnace will not talk about it, but there is a little leakage. That is, the furnace shell is made of steel plate, equipped with steel water cooling wall, and the inner layer is knotted and lined with refractory.
4. Mixed iron.
The composition of molten iron varies from furnace to furnace, and it is put into a mixer to make the composition uniform.
5. Steelmaking.
Hot metal has high carbon content, and it is blown by converter to remove carbon and other impurities through oxidation.
6. refining.
The molten steel is refined to further remove impurities, and then high-purity iron blocks are obtained by casting.
If adjusting components such as alloy and carbon are added, molten steel can be obtained, and steel can be obtained after casting.