La réduction du minerai de fer par l’hydrogène : étude cinétique, phénomène de collage et modélisation

摘要

In context of a reduction in CO2 emissions of the steel industry, we studied the direct reduction of iron ore by pure H2, whose environmental merit is to release H2O instead of CO2. The reduction kinetics of different types of industrial pellets was measured by thermogravimetry. The effects of temperature, particle diameter and gas composition were analyzed. It was shown that the three reduction stages (Fe2O3> Fe3O4> FeO> Fe) take place in mixed kinetic regimes, firstly controlled by the chemical reactions, then by intergranular gas diffusion, as well as by solid-phase diffusion through the dense iron layer produced. At the stage of wustite, the grains break up into crystallites which are reduced to iron in a topochemical way. From 900 to 950 °C, the reaction slows down due to the formation of Fe-γ instead of Fe-α. Above 900 °C, pellets may stick together during the reduction; we proposed an explanation for this phenomenon. Based on these results, we then developed a kinetic model to describe the reduction of a single pellet. The comparison between the model and experimental results is satisfactory except at higher temperatures. Finally, this kinetic model was integrated in a multiparticle reactor model, called REDUCTOR, which simulates the reduction of pellets in an industrial shaft furnace. Simulations were carried out by testing the influence of key operating parameters to determine the best operating conditions and make recommendations for a future industrial implementation of this process.