Numerical analysis of flow and combustion behavior in tuyere and raceway of blast furnace fueled with pulverized coal and recycled top gas

The simultaneous injection of pulverized coal (PC) and CO2-stripped blast furnace top gas (BFG) into the raceway of a blast furnace is an effective means of reducing carbon dioxide emissions in the ironmaking process. The BFG can be used as the cooling gas flowing through the annulus of coaxial lance. To stabilize the operation in the lower zone of blast furnace, the combustion characteristics of PC with/without BFG cooling gas within the blowpipe-tuyere-raceway region of a blast furnace are numerically investigated. The simulations focus on the effects of the lance configuration, the cooling gas type, and the cooling gas flow rate. The results show that a significant flow-induced pressure drop occurs at the blowpipe and tuyere part because of the gaseous combustion of the oxygen within the blast and the BFG injected via the lance. Moreover, the burnout of injected coal is significantly decreased with an increasing BFG cooling flow rates due to the additional oxygen consumption by the BFG. Finally, it is shown that a stronger swirling flow was formed when the lance configuration with bigger diameter was employed. Overall, the current numerical results provide a useful basis for improving the blast furnace performance in the future.