Growth Behavior of Iron Grains During Reduction Roasting of Fayalite

Copper slag containing fayalite as the main mineral is normally pretreated by reduction roasting for iron extraction through magnetic separation, and the particle size of iron grain affects iron recovery. The growth kinetics of iron grains in fayalite during reduction roasting were systematically studied in this work. Results showed that the iron grains increased with roasting temperature and reaction time. When the roasting time was 20‒80 min, the growth kinetic parameters of iron grains, namely, mean growth index, pre-exponential factor, and apparent activation energy, were 5.135, 7.66 × 10⁹, and 263.79 kJ.mol⁻¹, respectively. These values changed to 8.228, 1.41 × 10¹⁷, and 426.62 kJ.mol⁻¹, respectively. When the roasting time was 90‒210 min. Fayalite could be decomposed into metallic iron and silica during reduction roasting, but the mean iron grain size was lower than 6 μm after roasting at 1573 K for 210 min. This result was attributed to the presence of silica, which restrained the growth of iron grain. This research has guiding significance for regulating iron grain growth in reduced products of copper slag.