Reduction and Carburization Behaviors of Iron Oxide Composite with Iron Carbide and Free Carbon

The blast furnace ironmaking process relies heavily on fossil fuels, posing challenges to achieving carbon neutrality. New methods, like hydrogen reduction ironmaking, face limitations such as the need for high-grade iron ore and issues with DRI melting. To address these, biomass char has been explored as a carbon-neutral carburizing agent, yet practical application is difficult due to biomass supply limitations in East Asia. Thus, Carbon Capture and Utilization, CCU becomes essential. Examples include iACRES and carbon recycling blast furnaces, which recycle CO2 for reducing agents but have limited scope. Direct carburization with solid carbon is significantly faster than gas carburization, suggesting solid carbon recovery from CO2 is preferable. However, issues for fine carbon powder handling necessitate a new process: Carbon Recycling Ironmaking Process using Deposited Carbon-Iron Composite (CRIP-D). This process reforms exhaust gases into CO-rich gas, depositing carbon into porous iron whiskers, which can produce hot metal carbon-neutrally. The composites using hematite and deposited carbon reduced at lower temperatures and exhibited more extensive melting and coalescence at 1 300 degrees C compared to those with less the carbon. The presence of cementite was crucial for promoting carburization and melting. CRIP-D aims to integrate carbon recycling into steel production, utilizing high-porosity iron whiskers and recovered carbon to achieve carbon-neutral steelmaking. The findings show the importance of co-existing of free carbon and iron carbides in enhancing the efficiency of the reduction and melting of carbon-iron oxide composite.