Preface to the Special Issue on “Green Energy Ironmaking and Steelmaking –Production of Green Energy and Its Use in Ironmaking and Steelmaking–”

The use of green energy (hydrogen) in the steel industry is becoming important for decreasing CO2 emission. The development of a proper method for green hydrogen production that can reduce the consumption of fossil fuels to a minimum using waste heat and COG from steel plants, biomass, and/or nuclear energy will be an important contribution. In addition, the use of green hydrogen in the ironmaking and steelmaking processes is essential. However, problems arising from the positive use of hydrogen must be clarified and resolved. To realize the use of green energy in ironmaking and steelmaking, research on the two main subjects below, which are illustrated in Fig. 1, will be necessary: (a) Production of green energy (hydrogen) (i) Waste heat (ii) Nuclear energy (ii) COG (ii) Biomass (b) Use of green energy (i) Conventional process (blast furnace and converter processes) (ii) Future ironmaking and steelmaking processes (hydrogen furnace) For the production of green hydrogen, it is important to secure the energy needed for production and raw hydrogencontaining materials. The energy needed for hydrogen production is considered to come from waste heat in steel plants1) and nuclear energy. The use of waste heat will be limited, particularly under an increased demand. Nuclear energy from a VHTR-IS (very high temperature gas-cooled reactor – iodine-sulfur) process will therefore be important for the future mass production of hydrogen, although the current climate for promoting nuclear energy policies is quite gloomy following the Fukushima disaster on March 11th, 2011. COG and biomass are probable sources of raw hydrogencontaining materials for the decrease of CO2 emission. However, these materials may be limited when the demand for hydrogen increases. As another source, natural gas is the most realistic raw material for hydrogen production, but as a form of fossil fuel, it is accompanied by a certain amount of CO2 emission. Ideally, a process involving a combination of water and nuclear energy (VHTR-IS process) would have the lowest amount of CO2 emissions. Simultaneously, the method for using green hydrogen is a key subject. If fuel cells for automobile and cogeneration systems become popularized, the demand for hydrogen will increase rapidly. However, it currently takes time to propagate. On the other hand, if the use of hydrogen in the ironmaking and steelmaking processes is successful, the production of hydrogen will increase drastically. In Fig. 1, the use of green hydrogen is classified into two categories. One is the use in conventional ironmaking and steelmaking processes. The other is the use in hydrogen furnace (HF) aiming to 2050. This special issue marks the first attempt at realizing the HF concept, in which not only the reduction of iron ore with hydrogen, but also the simultaneous melting of metallic iron, is described. The process of HF leads to the concept of “direct steelmaking.” In direct steelmaking, pure iron without carbon and inclusions can be produced directly, and many of the processes used in conventional ironmaking and steelmaking, such as dephosphorization, desulfurization, desiliconization, and decarburization, can be eliminated. Based on this background, the research group “Green Energy Ironmaking and Steelmaking” was established by ISIJ in 2008. Twenty researchers from universities, national institutions, and companies joined this group for studying the above subjects. Various achievements have been obtained during the four-year research period. To summarize the activities of this research project, a special issue on “Green Energy Ironmaking and Steelmaking –Production of Green Energy and Its Use in Ironmaking and Steelmaking–” was prepared for publication. Actually, since green energy ironmaking and steelmaking are related to a wide range of research, beyond the uses mentioned above, we welcomed the submission of papers from researchers not involved with our research group. A large number of papers submitted by international researchers confirmed the significant interest in the reduction of CO2 emission through the ironmaking and steelmaking processes. We sincerely hope that this issue will contribute to the realization of green energy ironmaking and steelmaking as well as to the reduction of CO2 emission. Finally, on behalf of the editors of this special issue, I am grateful to all the authors for their contributions.