3. Answer the following

ii. Name different zones in the Blast furnace. Write the reactions taking place in them.


A blast furnace is a high-temperature furnace used in the production of iron and steel. It consists of several different zones, each with specific functions and reactions taking place. The main zones in a blast furnace are:

  1. Charging Zone (or Stockhouse):

    • This is the uppermost part of the blast furnace where raw materials are loaded. These raw materials typically include iron ore (usually in the form of iron oxides like hematite or magnetite), coke (carbonized coal), and limestone (a fluxing agent).
  2. Drying and Preheating Zone:

    • Below the charging zone, there is a region where the raw materials are dried and preheated by hot gases that are being generated in the lower parts of the furnace.
    • The reactions in this zone involve the removal of moisture from the raw materials.
  3. Reduction Zone (or Combustion Zone):

    • The reduction zone is where the main chemical reactions responsible for the production of iron occur.
    • The primary reactions in this zone involve the reduction of iron ore (Fe2O3 or Fe3O4) to iron (Fe) by the carbon monoxide (CO) produced from the combustion of coke:
      • Fe2O3 + 3CO → 2Fe + 3CO2
      • Fe3O4 + 4CO → 3Fe + 4CO2
  4. Melting Zone (or Fusion Zone):

    • In this zone, the iron formed in the reduction zone melts and collects at the bottom of the furnace.
    • The temperatures here are high enough to keep the iron in a molten state.
  5. Slag Formation Zone (or Slag Bath):

    • Just above the molten iron, there is a layer of slag formed by the reaction between impurities in the iron ore and the fluxing agent (usually limestone):
      • CaCO3 → CaO + CO2
      • CaO + SiO2 → CaSiO3 (slag)
    • The slag is less dense than the molten iron and floats on top, protecting the molten iron from contact with atmospheric oxygen.
  6. Tuyere Zone:

    • At the bottom of the furnace, there are openings called tuyeres through which hot air or oxygen-enriched air is injected into the furnace.
    • This zone provides the oxygen necessary for the combustion of coke and the generation of carbon monoxide (CO).
  7. Bosh Zone:

    • The bosh is the area in the middle of the blast furnace, where the furnace widens. It plays a crucial role in ensuring efficient gas-solid contact, allowing for better heat exchange and chemical reactions.
  8. Stack or Hearth Zone:

    • This is the lowermost part of the blast furnace, where molten iron and slag collect and are periodically tapped off.

These zones work together in a blast furnace to produce molten iron and slag. The iron is then further processed to obtain various grades of steel. The specific conditions and reactions in each zone are carefully controlled to optimize the efficiency of the iron production process.