Here's an explanation of the process:
Iron Smelting Process:
1. Iron Ore Preparation: Iron ores, such as hematite (Fe2O3) or magnetite (Fe3O4), are mined and crushed into smaller pieces.
2. Blast Furnace: The crushed iron ore is mixed with coke (a carbon-rich fuel) and limestone and fed into a large vertical cylindrical furnace called a blast furnace.
3. Coke Combustion: Hot air is blown into the furnace from the bottom, causing the coke to burn and generate intense heat.
4. Reduction of Iron Ore: The carbon monoxide gas produced during coke combustion rises through the furnace and reacts with the iron oxide in the ore, reducing it to metallic iron.
5. Formation of Slag: Limestone (calcium carbonate, CaCO3) plays a crucial role in the smelting process. It reacts with impurities present in the iron ore, such as silica (SiO2) and alumina (Al2O3), to form a molten mixture called slag.
6. Slag Removal: The slag floats on top of the molten iron due to its lower density. It is periodically tapped off from the furnace.
By removing these impurities as slag, limestone helps to purify the molten iron and produce pig iron, which contains around 92-94% iron along with some impurities like carbon, silicon, and manganese.
Further purification processes are required to obtain high-grade steel from pig iron.
