Numerical simulation of reduction behavior in shaft furnace based on DEM and CFD

Abstract Reasonable gas flow distribution can greatly enhance the reduction performance of the shaft furnace. Key parameters such as burden voidage, pellet size, gas inlet diameter, and gas inlet angle directly govern gas-solid contact and reactant uniformity. In this work, the voidage inside the shaft furnace with different pellet sizes was calculated by DEM method, and the effects of operating parameters and conditions such as pellet size, gas inlet diameter and gas inlet angle on the reduction performance of the shaft furnace were analyzed by CFD method. It was shown that the voidage increase with the increase of pellet size and shaft furnace height, and the range of voidage for 9–15 mm particles increased from 0.20–0.42 to 0.29–0.48. Smaller pellets (9 mm) achieved superior reduction efficiency, yielding a maximum Fe mass fraction of 82.9 % at the solid outlet, whereas larger pellets (15 mm) suffered from internal diffusion limitations (Fe mass fraction: 60.4 %). Enlarging the gas inlet diameter significantly enhanced reduction reaction, with Fe mass fraction rising from 70.8 % (0.2 m) to 90.8 % (0.4 m). In contrast, gas inlet angle variations exhibited negligible influence (<2 % change in component distributions). This work provides a theoretical basis for optimizing the operating parameters of the shaft furnace and improving the reduction efficiency.