Process flow sheet evaluation of a nuclear hydrogen steelmaking plant applying very high temperature reactors for efficient steel production with less CO2 emissions

•CO2 emissions from a nuclear hydrogen steelmaking system was 13–21% of that from a blast furnace steelmaking system.•Heat input to shaft furnace in hydrogen steelmaking was large with much H2 consumption in the part.•Though hydrogen production thermal efficiency had influence on total heat input to hydrogen steelmaking, the effect on the CO2 emissions was small.•Steelmaking scale of a nuclear hydrogen steelamking plant with 2 VHTRs was a little smaller than that of the largest Midrex® steelmaking plants.

Recently, CO2 reduction is an important problem for steelmaking. Substitution of coal, presently used as a reducing agent of iron ore in blast furnaces, to hydrogen produced by non-fossil energy is a way to reduce CO2 emissions. In this study, the idea of nuclear hydrogen steelmaking (NHS) system was investigated using very high temperature reactor (VHTR) and thermochemical hydrogen production iodine–sulfur (IS) process. Heat input and CO2 emissions including material production, material transportation, and electricity generation were evaluation criteria. Results of the NHS system were compared with those of a conventional blast furnace steelmaking (BFS) system. Influence of heat input options to the steelmaking process and hydrogen production thermal efficiency of IS process were investigated for the NHS system. Though heat input to the NHS system was 130–142% of that to the BFS system, CO2 emissions of the system were 13–21%. Pre-heating of hydrogen by coal combustion before blowing to a shaft furnace was effective to decrease heat input, although CO2 emissions increased. Direct pre-heating by nuclear heat was also effective without increase of CO2 emissions if close location of the nuclear reactor to the steelmaking plant was publicly accepted. Hydrogen production thermal efficiency had a significant influence on the heat input. Conceptual design of a plant unit of the NHS system producing steel of 1.47 × 106 t/y with 2 VHTRs of 600 MW heat and a shaft furnace and an electric arc furnace was proposed. The steelmaking scale was a little smaller than those of the recent largest Midrex® plants.