Reduction Behavior and Mechanism of Biomass‐Derived Carbon Magnetite Pellets for Clean Ironmaking

Reducing iron ore pellets with renewable carbon offers a promising route to lower‐carbon ironmaking, yet the stage‐dependent kinetics and controlling mechanisms of magnetite pellets reduced by biomass‐derived chars under different C/O ratios and temperatures remain insufficiently quantified. This work systematically investigates the isothermal reduction behavior of magnetite pellets using bamboo charcoal, wood charcoal, and coke powder over various carbon‐to‐oxygen (C/O) ratios at 800, 900, 1000, and 1100°C. The reaction process was divided into three stages (phases 1–3). The results showed that at 1000°C and C/O = 0.9, the pellet reduced with wood charcoal achieved a reduction conversion rate of 84.52%. Classical kinetic models were applied for segmented fitting, and the Ginstling Brounshtein diffusion model provided the best performance (R 2 > 0.91) under most conditions, especially at higher temperatures. Heatmap analysis of stage‐wise R 2 further indicates a transition from chemical‐reaction control to diffusion control. Apparent activation energies calculated from fitted rate constants show that coke exhibits the highest value, consistent with its denser structure and lower gas reactivity, whereas bamboo and wood charcoals yield lower activation energies and higher reactivity. Overall, biomass‐derived carbon is a promising renewable reductant for magnetite pellet reduction and offers potential for cleaner ironmaking.