After the iron is separated, what is the role of limestone?

After the iron is separated, what is the role of limestone?

• A. Limestone is added which acts as a flux to remove impurities
• B. Water is used to wash away impurities
• C. Impurities are left in the iron
• D. The ore is re-oxidized to remove impurities

Answer: (A)

Limestone acts as a flux to remove impurities. In the high heat of the furnace, limestone (calcium carbonate) breaks down to calcium oxide, which then reacts with acidic impurities such as silica to form a molten slag like calcium silicate. This slag floats on top of the molten iron and can be tapped off, carrying the impurities away from the metal. This process not only helps remove impurities but also lowers their reactivity, keeping the iron purer as it forms. Water washing, re-oxidizing, or leaving impurities in the iron aren’t how this stage works; impurities are removed by forming slag that separates from the molten metal.

Limestone acts as a flux to remove impurities. In the high heat of the furnace, limestone (calcium carbonate) breaks down to calcium oxide, which then reacts with acidic impurities such as silica to form a molten slag like calcium silicate. This slag floats on top of the molten iron and can be tapped off, carrying the impurities away from the metal. This process not only helps remove impurities but also lowers their reactivity, keeping the iron purer as it forms. Water washing, re-oxidizing, or leaving impurities in the iron aren’t how this stage works; impurities are removed by forming slag that separates from the molten metal.