Patterns of Coke Adaptability and Evaluation Mechanisms Under Different Blast Furnace Atmospheres

To optimize the configuration of low-carbon blast furnace raw materials and fuels, this study systematically evaluated the reaction initiation temperature, solution loss degradation, ferrous burden softening-melting behavior, and gas permeability of different reactive cokes under four simulated atmospheres: a traditional blast furnace (TBF), a hydrogen-rich traditional blast furnace (TBF-H₂), an oxygen blast furnace (OBF), and a hydrogen-rich oxygen blast furnace (OBF-H₂). The results show that with increasing coke reactivity, enhanced early reduction leads to a decrease in the softening initiation temperature, dropping from 1089 to 1074 °C under the traditional blast furnace atmosphere. In hydrogen-rich atmospheres, high concentrations of H₂O significantly reduce the proportion of optically anisotropic structure-which characterizes coke strength-from 61.0% to 41.7%, indicating intensified degradation and fragmentation of the load-bearing coke structure. Process adaptability evaluations reveal that under the TBF atmosphere, burden-column permeability is highly sensitive to coke reactivity, with Coke 3 causing the maximum pressure drop (ΔPmax) to increase to 35.7 kPa, indicating the need for high-quality coke. Conversely, under OBF and OBF-H₂ processes, the high reduction potential compresses the melting zone to a narrow range of 10-30 °C, maintaining both ΔPmax (11.5-14.0 kPa) and the cohesive-zone permeability index S (<150 kPa·°C) at consistently low levels. Within the present laboratory apparatus and the three-coke dataset, the oxygen-blast-furnace atmospheres reduced the sensitivity of cohesive-zone permeability to coke reactivity. This result suggests a potentially broader coke-quality window, but pilot-scale validation, process simulation, and economic assessment are required before industrial application or cost advantages can be established.