SynopsisThe iron and steelmaking industry must focus on neutralizing CO 2 emissions. One solution involves using hydrogen as a reducing agent for iron ore. However, carbon is an essential element as primary steel is produced by refining molten carbon-saturated iron (hot metal). Ironmaking processes applying CO 2 capture and utilization have been suggested; however, they are limited to the reduction process. To satisfy the demand for primary steel production with net-zero CO 2 emissions, a new carbon recycling ironmaking process capable of producing hot metal must be considered. This study proposes a carbon recycling ironmaking process using deposited carbon-iron ore composite (CRIP-D). In the CRIP-D process, hot metal is produced by using the solid carbon recovered by reforming exhaust gas as reducing and carburizing agents. Moreover, using the recovered solid carbon, iron oxides are reduced more rapidly, and reduced iron is melted at a lower temperature than that using fossil fuel-derived carbon. This means carbon-neutral steel can be produced more efficiently than conventional ironmaking processes. Using proven technologies, following hot metal production, primary steel can be produced while minimizing the burden on the steel mills for converting equipment. Thus, true carbon-neutral primary steel is feasible using the proposed CRIP-D process. Keywords; Carbon neutrality, Carbon dioxide capture and utilization, Carbon-iron ore composite, Carbon deposition, Hot metal 1.Introduction At approximately 1.9 billion tons worth of production per year, steel is the third most abundant material on earth, after cement and timber. Its high strength, ease of processing, and relatively low cost render its complete substitution less likely in the foreseeable future. Approximately 70% of global crude steel is produced within a blast furnace-basic oxygen furnace (BF-BOF). The remainder is produced within an electric arc furnace (EAF) 1 . The BF process consumes considerable amounts of coking coal, which is equivalent to approximately 16% of the global demand for coal. Consequently, the high dependence on coal has resulted in the iron and steelmaking sector accounting for 2.6 gigatonnes of CO 2 emissions annually, which is 7% of the global total 1 . With the recent strong demand for achieving a carbon-neutral society, net-zero CO 2 emission in the iron and steelmaking industry has been an important issue.Steel is an alloy of iron and carbon. Thus, the use of carbon is inevitable in the process of steelmaking. Carbon performs three important chemical roles in the BF process. First, it functions as a heat source. Second, it is used as a reducing agent for iron ores. Third, it functions as a carburizing agent for reduced metallic iron. The melting point of pure iron (1537 ℃) is decreased to 1150 ℃ by dissolving carbon at a saturated concentration (4.3 mass%). Molten carbon-saturated iron (hot metal) can be separated from molten impurities such as sulfur, phosphorus, and silicon based on the difference in densities. Consequently, the...