1. Iron Ore Reduction (Blast Furnace):
This is the primary step where iron ore (mainly hematite, Fe₂O₃) is reduced to iron metal.
Overall Reaction:
Fe₂O₃(s) + 3CO(g) → 2Fe(l) + 3CO₂(g)
Step-by-step Reactions:
* Reduction of Hematite to Magnetite:
Fe₂O₃(s) + CO(g) → Fe₃O₄(s) + CO₂(g)
* Reduction of Magnetite to Wüstite:
Fe₃O₄(s) + CO(g) → 3FeO(s) + CO₂(g)
* Reduction of Wüstite to Iron:
FeO(s) + CO(g) → Fe(l) + CO₂(g)
2. Slag Formation:
Impurities in the iron ore, like silica (SiO₂), react with limestone (CaCO₃) to form slag, which is a molten mixture of calcium silicate (CaSiO₃).
Reaction:
CaCO₃(s) → CaO(s) + CO₂(g)
CaO(s) + SiO₂(s) → CaSiO₃(l)
3. Pig Iron to Steel:
Pig iron, the product of the blast furnace, contains impurities like carbon, sulfur, phosphorus, and silicon. These impurities are removed in a process called steelmaking.
Basic Oxygen Furnace (BOF) Process:
Oxygen is blown into the molten pig iron, oxidizing the impurities.
Reactions:
C(s) + O₂(g) → CO₂(g)
S(s) + O₂(g) → SO₂(g)
4P(s) + 5O₂(g) → 2P₂O₅(s)
Si(s) + O₂(g) → SiO₂(s)
Electric Arc Furnace (EAF) Process:
Scrap metal is melted and refined using electric arcs, which also remove impurities through oxidation.
Reactions:
Similar to BOF process, but with different energy input.
4. Alloying:
To produce specific steel grades with desired properties, various elements like carbon, manganese, chromium, nickel, and others are added to the molten steel.
Reactions:
These reactions are complex and vary depending on the specific alloying elements.
Note: These equations represent the main reactions involved in iron refining. There are many other reactions and sub-reactions happening in the processes.
