Performance of magnetite fines for continuous hydrogen production

Journal article, 2025

Hydrogen production from biogenic fuels in fluidized beds may provide the steel industry with a path to decarbonization and negative emissions. Magnetite fines (MAF), a common intermediate product in the European iron and steel industry, was utilized as an oxygen carrier for continuous hydrogen production. Performance was evaluated in a fluidized bed reactor, demonstrating that MAF effectively converts low-grade gaseous biofuels and subsequently generates high-purity hydrogen through water splitting. A kinetic model accounting for thermodynamic limitations was developed to assess MAF's reactivity towards reduction with CO and H2, and oxidation with H2O. The activation energy as a function of the mass conversion degree ranged from 32.7 to 70.5 kJ/mol for reduction with CO, and from 22.6 to 67.4 kJ/mol for H2: for oxidation with H2O, it ranged from 51.2 to 121.3 kJ/mol. Significant variations in the apparent activation energy were observed, which can be linked to changes in the rate-controlling mechanisms, highlighting the influence of microstructural evolution on reactivity. The findings provide valuable insights into the apparent kinetics of MAF and suitable operating conditions for optimizing hydrogen production, with the highest hydrogen production rate of 0.37 mmol g⁻¹ min⁻¹ achieved at 800 °C.