Hydrogen ironmaking: kinetics and modeling of the iron ore reduction

As a major consumer of fossil carbon, the steel industry must make efforts to reduce its contribution to global warming, currently 7% of anthropogenic CO2 emissions. One breakthrough evolution, which is the subject of much R&D news, is to use hydrogen for the reduction of iron ore. The alternative route of direct reduction by green H2 produced by water electrolysis with decarbonised electricity followed by electric steelmaking is the most promising, likely to reduce steelmaking CO2 emissions by 90%. Our team at the Institut Jean Lamour, Nancy, France, has been interested in direct H2 reduction since the 2000s. I present here an overview of our work on the subject. Firstly, the experimental study of the reduction of industrial pellets in thermobalance shows that the kinetics are complex, influenced by the chemical and morphological transformations at the scale of the pellet grains. For example, there are slowdowns at the end of the reaction at temperatures of 700 and 950°C. However, the reduction is complete, with 100% metallisation. Secondly, we have built a sophisticated kinetic model of the transformation of a single pellet that accounts for the experimental results. Finally, we have developed a multi-particle reactor model, REDUCTOR, which simulates the behaviour of a direct reduction shaft furnace. If the furnace is operated under pure H2, the kinetics being faster than with H2-CO-CH4 mixtures, one can envisage more compact reactors and a simpler H2 process than the current direct reduction processes.

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