Partial Substitution of Coke Breeze with Natural Gas in Iron Ore Sintering

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Confronting the urgent need for decarbonization in iron ore sintering under global warming, this study develops an innovative strategy employing natural gas injection to obtain partial replacement of coke breeze. Under constant total heat input, natural gas is introduced between 5 and 20 min into the sintering process, achieving thermal substitution rates ranging from 15 to 30%. The results demonstrate that increasing the natural gas substitution ratio improves granulation performance and enhances bed permeability. At the optimal substitution level of 15%, notable enhancements are observed relative to the baseline with no substitution. Specifically, sintering speed increases by 1.63 mm per minute, yield improves by 3.11%, the tumbler index rises by 5.68%, productivity increases by 0.14 t·(m 2 h) −1 , and solid fuel consumption decreases by 12.87 kg t −1 . Mineralogical analysis indicates a 2.08% increase in calcium ferrite content and a 0.55% reduction in silicate phases at the 15% substitution level. Metallurgical properties are also significantly improved, the RDI +3.15 index increases by 2.72%, the reducibility index increases by 5.70%, and better melting and dripping characteristics are achieved. Further optimization of injection parameters is expected to support the contribution of this technology to decarbonizing the steel industry.