Reduction and Melting Behaviors of Iron Oxide Composite with Carbon Deposited Using CO-CO₂-H₂ Mixed Gas

Abstract

The ironmaking industry consumes significant fossil fuel-derived carbon as a heat source, reducing agent for iron ores, and carburizing agent for reduced iron. Despite the demand for reduction of carbon dioxide emission, carbon is essential for smelting molten iron. A carbon recycling ironmaking process using circulating CO has been proposed to achieve carbon neutrality. However, this process does not consider molten hot metal production because CO does not dissolve sufficient carbon in iron to be melt. Our group has suggested a new carbon recycling ironmaking process capable of producing hot metal. This process utilizes free carbon and iron carbides produced via carbon deposition reactions using metallic iron as a catalyst. CO gas produces only Fe₃C, whereas adding H₂ gas also produces Fe₅C₂. The composite, agglomerated with these carbonaceous materials and fine iron ore (Deposited Carbon-Iron Oxide Composite: DCIC), is reduced and melted in a furnace. This study focuses on the effects of iron carbides and free carbon on the melting behavior of DCIC.

Fe₃C, Fe₅C₂, and free carbon were produced by vapor deposition using porous iron whiskers and CO-CO₂-H₂ gas. These were agglomerated with hematite reagent to prepare DCIC samples. The samples were heated to 1300°C. The DCIC containing fine iron carbides particles was completely melted. This was a behavior that is not observed in the composite with carbon deposited by pure CO gas. These results suggest that using a CO-CO₂-H₂ mixed gas for carbon deposition in the CRIP-D process can enhance the reduction and melting of the composites.