Hydrogen‐Based Reduction of Hematitic Iron Ore in a Fluidized Bed Kinetic Reactor at Elevated Pressures

Abstract

Hydrogen-based direct reduction of iron ore is a key technology for reducing CO2 emissions in the iron and steel industry. A novel pressurized fluidized bed kinetic reaction unit is used to investigate the reduction behavior of two international iron ores, including synthetically produced hematite from magnetite oxidation. The reduction takes place at various temperatures (650, 700, and 750°C), various hydrogen partial pressures (30, 55, and 80 vol% H₂), and 3 bar, using particle sizes of 125–500 µm. Results show that hydrogen partial pressure and temperature primarily affect the reduction kinetics. Higher H₂ concentrations significantly increase the reduction rate, while lower H₂ concentrations result in slower kinetics and overall conversion. Natural hematite shows higher reduction kinetics than synthetic hematite. At 750°C, significantly higher reduction rates are achieved. The limiting steps are the H₂/H₂O equilibrium in the second kinetic phase and, potentially, solid-state diffusion due to the formation of a dense iron layer in the final phase. Moreover, both iron ores display a potential temperature minimum effect, leading to reduced reduction rates, particularly at advanced stages. Overall, the study highlights the key roles of hydrogen partial pressure and temperature in hematite reduction kinetics.