Particle-scale study of coke combustion in the raceway of an ironmaking blast furnace

The raceway is a zone of considerable significance in a blast furnace (BF) because it supplies energy and reducing agents that ensure successful and stable BF operation. Recently, experimental and numerical studies of BF have been widely conducted to examine the inner multiphase flow transport phenomena; however, the study of reacting flows at the particle level in BF is limited. In this study, a multiscale method that couples computational fluid dynamics (CFD) with discrete element method (DEM) is employed to examine the dynamic evolution of the raceway and inner thermo-chemical behaviours in a BF. Raceway evolution and formation, microscale characteristics, and coke temperature and combustion are comprehensively explored and analysed under various operating conditions. The predicted results show that the distributions of coke temperature, carbon loss, and diameter variation are consistent. More burning coke particles occurs in the vicinity of the region next to the tuyere, where there is a stronger high-temperature circular gas flow than in other regions. The increase in oxygen concentration indirectly increased the carbon monoxide concentration, but changes in the inlet gas temperature and flow rate yielded no effect on the carbon monoxide level in the studied ranges. These new perceptions of the complicated reacting flows inside the raceway area are beneficial for the fundamental understanding of energy utilisation and process optimisation.