4. Why do we fill the blast furnace with limestone and quartz?
Answers
Answer:
Limestone is also used to remove impurities from the blast furnace when making iron. The impurities are mostly silicon dioxide (also known as sand). The calcium carbonate in thelimestone reacts with the silicon dioxide to form calcium silicate (also known as slag).
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Metallurgy of Iron is done in Blast Furnace.
Iron ore is Haematite = Fe₂O₃
Usually Smelting process is used in Extraction of Iron from its ore .
Smelting is a Pyrochemical process where ore is mixed with flux and fuel and strongly heated.
- Flux is a substance added to ore to remove the gangue particles from it by reacting with ore.
- The gangue particles present in Iron ore is generally SiO₂ which is acidic in nature and non fusible.
- So Lime stone - Calcium carbonate which is basic in nature is used for the following process:
- To provide a source of CaO
CaCO₃------> Cao + CO₂
2. To remove gangue particles and form fusible Material called as Slag[ calcium silicate ]
CaO+ SiO2 ---> CaSiO3
3. Decomposition of lime supplies carbon dioxide which is useful for maintaining excess of CO so that the conversion of Fe3O4 to Fe2O3 is prevented.