Effects of particle shape, breakage properties, and operating parameters on blast furnace raceway size through CFD-DEM simulations and cold-model experiments

Abstract

During ironmaking, high-speed air injected laterally from a tuyere forms a raceway cavity in a coke bed, and this cavity affects gas transport and efficiency. This study created a quasi-two-dimensional apparatus and a computational fluid dynamics (CFD)–discrete element method (DEM) model to investigate the effects of particle geometry and properties on the raceway's size and shape. The parameters of a DEM contact model were obtained through calibration experiments, and the established CFD–DEM model was validated through raceway experiments conducted in a fluidized bed setup. Rigid BB bullets and crushable sorghum seeds were used to simulate coke particles in the raceway experiments, and hysteresis in raceway size was discovered with changing inlet gas velocity. Spherical DEM particles were used to simulate the motion of BB bullets, and spherical, multi-sphere, and polyhedral particles were used to simulate the motion of sorghum particles. The use of nonspherical DEM particles with a shape closely resembling that of sorghum resulted in the simulated raceway size being within approximately 15 % of the experimental raceway size. Furthermore, the Tavares model was incorporated into the developed model to capture particle breakage effects, and the results indicated that particle fragmentation increases the pressure gradients in the raceway. Overall, the results revealed that the developed CFD–DEM model can accurately predict the raceway behavior of nonspherical or breakable particles under gas injection, thus providing insights for efficient blast furnace operations.