Ironmaking Plant ~ Trial for Production of High-quality Steel from Recycled Iron Aiming at Reduction of CO₂ Emission

Abstract

Toward the realization of carbon neutrality in society, many industries have started to make very elaborate efforts. On the basis of COP (Conference of Parties) -FCCC (Framework Convention on Climate Change) indication, Japan is expected to reduce CO₂ emission by 46% until 2030 which target was declared by the prime minister Kishida in COP26. To attain this target, one of most effective ways is to reduce the CO₂ emission of ironmaking and steelmaking industries which are rather responsible due to the fact of their having 14% emission of total domestic CO₂ in all the industries, transportation, civil use and so on. The secondary iron resource, namely, steel scrap should like to be increasingly utilized since the reduction process of iron ore inevitably generating CO₂ can be avoided and only melting process of recycled steel should be managed. In this process, tramp elements such as copper are problematic, because copper induces surface cracks called copper embrittlement for instance. In this article, suppression of this drawback is extensively intended by the investigation of refinement of austenite grain size by cooling process and additional element as well as fine precipitation of copper sulfide. In addition, primary iron resource, namely, virgin steel is reconsidered toward realization of zero-carbon ironmaking process by smelting reduction by CO gas, which reducing gas is recovered from CO₂ produced in iron ore reduction process by zero-carbon energy such as renewable and nuclear power. Attempt by GXI project being implemented in the laboratory of zero-carbon energy in Tokyo Insite of Technology is also briefly introduced.