Softening and melting behaviors of ferrous burden in hydrogen-rich blast furnace cohesive zone

The changes in the softening and melting behaviors of ferrous burden in the cohesive zone and the characteristics of the slag–iron–coke interface in a blast furnace were investigated by simulating an actual blast furnace under hydrogen-rich conditions. According to the variation in the transient shrinkage of the burden under different atmospheres, the shrinkage start temperature of the sinter was higher than that of the pellets. The negative shrinkage rate of the pellets was greater than that of the sinter. Additionally, the softening start temperature in the blast furnace decreased under hydrogen-rich conditions, giving the blast furnace a broader range of softening zones. The softening start temperatures of the pellets and sinter decreased from 1102 to 949 °C and 1152 to 1080 °C, respectively. The hydrogen-rich traditional blast furnace conditions narrowed the melting zone temperature range and shifted it toward the high-temperature zone, significantly improving the burden layer permeability. However, under the hydrogen-rich oxygen blast furnace conditions, there were a decrease in the melting start temperature, a shift of the melting zone location to the low-temperature zone, and an increase in the burden layer permeability and pressure difference. A comparison of the slag–iron–coke interface characteristics under different atmospheric conditions showed that the carbon content in metallic iron decreased under hydrogen-rich traditional blast furnace conditions compared with traditional blast furnace conditions. Contrastingly, under hydrogen-rich oxygen blast furnace conditions, the carbon content in metallic iron increased compared with oxygen blast furnace conditions. These findings provide guidance for the development of low-carbon ironmaking processes in blast furnaces.