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.