Effect of hydrogen enrichment for reduction and softening-melting behaviors of different types of lump iron ores

Abstract

To explore smelting behavior of lump ores under hydrogen-rich conditions and guide optimization of burden structure of blast furnace after hydrogen injection, this study investigates the reduction and softening-melting behavior of lump ores. The results indicated that, compared to a pure CO atmosphere, the reduction properties of lump ore were significantly improved under a pure H₂ atmosphere, with the endpoint reduction degree reaching as high as 99%. The volume shrinkage of most lump ores increased after hydrogen enrichment. Notably, the shrinkage ratio of limonite before softening was considerably higher than that of hematite under both CO-N₂ and CO-H₂ -N₂ atmospheres. This suggests that the high-temperature compressive strength of limonite is lower than that of hematite. Hydrogen enrichment also led to a decrease in the softening beginning temperature of the lump ores, resulting in a broader softening range that shifted to a lower temperature range. The softening beginning and finishing temperatures of limonite were lower than those of hematite. Furthermore, hydrogen enrichment increased the melting beginning temperature, narrowed the melting range, and shifted it to a higher temperature region, thereby significantly improving the gas permeability of the burden column. After hydrogen enrichment, both the maximum pressure drop and permeability index of the lump ore decreased, which facilitated the reduction of the lump ore and the carburization of solid iron, ultimately increasing the mass of the dripping. These findings suggest that hydrogen enrichment can enhance the gas permeability of the burden column, thereby benefiting advanced smelting processes.