Hydrogen direct reduction and melting behaviour: pellets vs. briquettes

High-grade iron ores pellets and briquettes were reduced in a hydrogen atmosphere at the temperatures of 760 and 950 °C. The agglomerate's structural evolution was analysed using X-ray tomography before and after each single direct reduction experiment in order to map, characterize and quantify microstructure changes during the hydrogen reduction reactions. A previously developed image-analysis-based tool to estimate agglomerate porosity was used. Given the observed microstructural evolution and the thermo-gravimetric results, a comparative kinetic analysis conducted at two temperatures of the iron ores in different agglomeration states was revealed. A single reduced agglomerate for each different type was melted in the electric arc furnace to underline the temperature during melting and the hydrogen emission. This showed that the emission of hydrogen during the melting depends on the agglomerate's size.