3. Injection coal

Most blast furnaces inject pulverized coal into the tuyeres, partially replacing coke. The motivations are economic, the cost differential between coal and coke, and technical, notably the possibility of operating with high wind temperatures, which lead to lower consumption of reducing agents and reduced CO ₂ emissions, and with, wind overoxygenation, favorable to productivity.

The coal is finely ground and dried before being injected into the nozzles. Crushed coal generally has a particle size such that 50% is below 60 µm (figure 15 ). Ultra-fine coals are prohibited, as they are detrimental to the pneumatic transport of coal to the injection nozzles. As coals are naturally moist (5-8%), they...