What is the flux used in the extraction of cast iron from hamatite ore?

1 Answer
Feb 21, 2018

The flux is limestone (calcium carbonate).

Explanation:

The limestone decomposes at about 1000 °C to form "CaO"CaO and "CO"_2CO2.

"CaCO"_3 → "CaO + CO"_2CaCO3CaO + CO2

"CaO"CaO is a basic oxide, so it reacts with the acidic oxides in the ore (mainly "SiO"_2SiO2) to form slag, which is mainly calcium silicate.

underbrace("CaO")_color(red)("basic oxide") + underbrace("SiO"_2)_color(red)("acidic oxide") → underbrace("CaSiO"_3)_color(red)("a salt")

The slag melts and floats over the denser molten iron, and openings in the side of the furnace allow them to run off separately.

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