Numerical analysis on blast furnace performance under operation with top gas recycling and carbon composite agglomerates charging

The blast furnace operations with top gas recycling, carbon composite agglomerates (CCB) charging, cold oxygen blast and waste plastics injection are numerically evaluated by means of multi-fluid blast furnace model on the premise of constant raceway conditions and hot metal temperature. These evaluations are in comparison with conventional operation. Simulation results reveal that CCB charging and/or cold oxygen blast lead to low temperature level in the shaft region, which retards the reduction of CCB. On the other hand, injection of waste plastics enriches hydrogen gas in the furnace. And top gas (after CO₂ removal) recycling tremendously enhances the concentrations of H₂ and CO in the whole furnace, which greatly promote the indirect reduction of sinter in shaft despite lower temperature. Under the innovative operations, the efficiency of blast furnace shows evident improvement, especially in the case with simultaneous injections of treated top gas through shaft and tuyere. The model computations predicted that total heat input decreases while the productivity increases under the operation with top gas recycling. Additionally, top gas recycling and waste plastics injection also contribute to considerably reduce carbon dioxide emission. It is expectable to develop high efficiency blast furnace with improved productivity and lowered environment load through exploiting the processes presented in this study. If scrubbing and fixing of CO₂ and manufacturing of process oxygen are commercially available, these innovative processes will possess broad applying potential.