Q1: The main charge in blast furnace is usually

ANS:C - limestone, coke & iron ore.

Limestone, coke, and iron ore are the main components used in the blast furnace for the production of iron. Here's a brief explanation of each component's role:

1. Iron Ore: Iron ore is the primary raw material used in the blast furnace. It typically consists of iron oxides such as hematite (Fe2O3) or magnetite (Fe3O4). The iron ore is reduced to iron in the blast furnace through a chemical reaction with carbon monoxide, which is generated by the combustion of coke. The iron produced from the iron ore serves as the main product of the blast furnace process.
2. Coke: Coke is a form of carbon derived from coal that is used as a fuel and reducing agent in the blast furnace. It is essential for providing the high temperatures required for the reduction of iron ore to metallic iron. Coke undergoes combustion with air in the blast furnace, producing carbon monoxide (CO), which reacts with the iron ore to form molten iron. Coke also helps in maintaining the permeability of the furnace burden and provides structural support.
3. Limestone: Limestone (calcium carbonate, CaCO3) is added to the blast furnace as a fluxing agent. It serves multiple purposes, including:
   • Fluxing: Limestone reacts with impurities present in the iron ore, such as silica (SiO2) and alumina (Al2O3), forming slag. This slag floats on top of the molten iron and helps in the removal of impurities by forming a separate layer.
   • Thermal insulation: Limestone decomposes into lime (calcium oxide, CaO) and carbon dioxide (CO2) upon heating in the blast furnace. The decomposition reaction absorbs heat, contributing to maintaining the high temperatures required for iron reduction.
   • Slag formation: The calcium oxide produced from limestone combines with silica and other impurities to form calcium silicate-based slag, which is later removed from the furnace.