Comprehensive numerical modeling of raceways in blast furnaces

A numerical investigation of dynamic raceway formation in an industrial-scale blast furnace is performed using Computational Fluid Dynamics (CFD) coupled with a Discrete Element Method (DEM). The industrial-scale simulations are made feasible by incorporating the Flamelet Generated Manifold (FGM) method and a coarse-graining method to reduce the computational cost while ensuring effective modeling of gas phase combustion and a large number of solid particles, respectively. The model considers the interactions between pulverized coal (PC) and coke, as well as their interaction with gas. The simulations reveal a different size and shape of the physical and chemical raceway, indicating that not all crucial reactions occur within the physical raceway. According to the model, the physical raceway formation is primarily determined by the blast air momentum, and the PC combustion has a negligible effect on its dimensions. The chemical raceway formation heavily depends on the oxidation rate of coke. The utilization of PC is quantified in terms of burnout. Smaller PC particles are found to undergo a higher degree of burnout due to faster convective heating and oxidation rates. Modifying the angle of the PC injection lance in current configuration is found to be inconsequential to PC burnout. The presented results highlight the significance of enhancing PC-blast mixing to improve PC utilization and provide new insights into optimizing blast furnace operations.