High‐Temperature Reduction of Metallurgical Dust Briquettes by Biochar: Reduction Thermodynamics, Kinetics, and Mechanism

Metallurgical dust contains valuable Fe, Pb, and Zn, enabling resource recovery. Biochar, a carbon‐neutral reductant with low ash and high reactivity, is used to reduce metallurgical dust briquettes. Thermodynamic reactions are calculated with FactSage, followed by nonisothermal tests to clarify reduction mechanisms and isothermal tests at selected temperatures to track phase evolution. Kinetic models provide activation energies. The reduction proceeds in five stages. With increasing temperature, biochar gasifies to CO, which reduces metal oxides. PbO and ZnO are reduced by C/CO and volatilize as metallic vapors, while Fe particles grow, coalesce, and densify. The apparent activation energies are 126.29, 126.54, 74.08, and 109.83 kJ mol −1 for Stages II–V, indicating that the principal reduction of metal oxides in metallurgical sludge occurs predominantly in the final stage.