Kinetic Study of Biomass Co-Disposal of Zinc-Bearing Dust and Chromium-Bearing Sludge

Zinc-bearing dust and chromium-bearing sludge are typical solid wastes generated during the steelmaking process, with significant annual output. Pyrometallurgical processes relying on traditional carbon sources have notable drawbacks in terms of carbon emissions and high energy consumption. To address these issues, biomass was employed for the disposal of metallurgical solid waste to examine the reduction kinetics through non-isothermal thermogravimetric analysis. The results indicate that as the temperature increases the reaction during the co-disposal of zinc-bearing dust and chromium-bearing sludge can be divided into four stages: the evaporation of crystalline water, reduction of zinc ferrate and iron oxide, reduction of iron, chromium, and other oxides, and formation of the alloy phase. Using biomass as a reductant, the average activation energies for the second, third, and fourth stages of the reduction process were 115.70, 220.33, and 176.52 kJ·mol⁻¹, respectively, which are lower than those for traditional carbon. Therefore, this approach provides a more efficient and ecologically beneficial solution for the co-disposal of zinc-bearing dust and chromium-bearing sludge. The mechanism functions for each stage were determined using the Coats–Redfern method, with the second, third, and fourth stages corresponding to the two-dimensional diffusion model, three-dimensional diffusion model, and exponential nucleation mechanism model, respectively.