Numerical Study on the Effects of Key Operating Parameters on the Ammonia-Based Direct Reduction of Iron
摘要
This study numerically investigates ammonia as a low-carbon reducing agent in a direct reduction shaft furnace. A two-dimensional CFD model was developed, treating iron ore pellets as porous media with a three-step reduction mechanism (Fe2O3 → Fe3O4 → FeO → Fe). The effects of reduction time, gas temperature, flow rate, and material temperature on the temperature field, composition distribution, and metallization rate were analyzed. Results indicate that a reduction time of 110 min achieves temperature uniformity, complete Fe2O3 conversion, and over 95% bottom metallization. Gas temperature exhibits an optimum at 1173 K, promoting the highest FeO → Fe rate and metallization; higher temperatures lower the reduction rate and cause agglomeration, while lower temperatures lead to incomplete reduction. Increasing gas flow accelerates the reaction but reduces thermal efficiency. Material temperature shows nonlinear impact, with sintering and reoxidation at 700 K decreasing metallization to 40%. Optimal conditions—gas temperature 1173 K, flow rate 1400 m3/t, and material temperature 300 K—yield > 95% bottom metallization after 110 min. This work provides numerical insights for parameter optimization and energy assessment in ammonia-based direct reduction ironmaking.