Effect of Hydrogen-Based Mineral Phase Transformation on the Grinding Characteristics of Hematite: Particle Size Distribution, Grinding Kinetics, and Microscopic Characteristics

Hematite, an important iron mineral, has poor grindability that limits the efficient use of low-grade ores. This study first investigated the impact of hydrogen-based mineral phase transformation (HMPT) on hematite’s grinding characteristics using laboratory-scale pretreatment and grinding tests with three different particle sizes. The results show that HMPT improved hematite’s grindability. Under the same grinding conditions, d10, d50, and d90 decreased by 30% to 70% after the same grinding time. The PBM analysis shows that, after HMPT treatment, the selection function for the same particle size increased by about 1.5 times, while the breakage function significantly decreased. This indicates that the particle properties changed, increasing the likelihood of the particles being ground. In addition, the uniformity coefficient n increased by 18% to 25%, while the fractal dimension D decreased by 0.10 to 0.34. This led to an optimized particle size distribution and a reduction in overgrinding and undergrinding. SEM results show that HMPT causes hematite to form porous cracks, reducing particle hardness and improving grindability. This study supports HMPT as a green, efficient pre-treatment method for grindability and promotes sustainable iron processing.