Comparative Study on Reduction in Oolitic High-Phosphorus Iron-Ore Lumps and Pellets Under H2 Atmosphere

High-phosphorus iron ore can be utilized using a technical route of hydrogen-based shaft furnace reduction, followed by electric arc furnace (EAF) melting separation. In shaft furnace reduction, both pellet and lump ore could serve as feedstock. To optimize the charge pattern in the H2-based shaft furnace, an investigation of the reduction behavior of high-phosphorus iron ore lumps and pellets under H2 atmosphere was conducted. Results revealed distinct differences between the lumps and the pellets in terms of physicochemical characteristics, maximum reduction fractions, microstructure evolution, and reduction kinetics characteristics. The lumps exhibited a notable presence of oolitic structures with 60.08 wt.% total iron, 11.69 wt.%. Fe2+ ion, and 0.80 wt.% phosphorus. Under H2 atmosphere, the lumps achieved a maximum reduction fraction of 0.80. During the reduction, fayalite formed in the early stage, and glassy phases appeared in the later stage. The rate-controlling steps included internal gas diffusion, interfacial chemical reaction, and solid-state diffusion of ions. In contrast, the oolitic structures were completely disrupted in the pellets. The pellets contained 56.01 wt.% total iron, 0.86 wt.% Fe2+ ions, and 0.73 wt.% phosphorus. The pellets reached a full reduction under H2 atmosphere with negligible formation of fayalite and glassy phases. The rate-controlling steps included internal gas diffusion and interfacial chemical reaction.