A new approach to collaborative resource utilization of biological sludge and zinc-bearing dust : Reduction characteristics and mechanisms

This paper proposes an innovative approach for co-processing zinc-bearing dust with biological sludge, using the organic matter in the sludge as a reducing agent to replace traditional fossil fuels (coal/coke). The results show that the reduction process of biological sludge-zinc-bearing dust pellets (BZP) is divided into two stages. In the first stage (25–620 °C), the breakdown of C = C, C-O-C, and C-O bonds present in biological sludge produced carbon oxide (CO) and hydrogen (H₂), facilitating the conversion of zinc ferrite (ZnFe₂O₄) to magnetite (Fe₃O₄). The second stage (620–1300 ℃), the cleavage of C = C, C–C and C–H bonds and carbon gasification generate more CO and H₂, further reducing magnetite (Fe₃O₄) to metallic iron (Fe) and zinc oxide (ZnO) to zinc monomers (Zn). The activation energy of BZP in the two stages was 32.86 kJ·mol⁻¹ and 73.88 kJ·mol⁻¹, respectively. The metallization rate and the zinc removal rate of BZP achieved 58.47 % and 86.74 %, respectively, indicating the effectiveness and feasibility of the propose of approach. This approach provides a clean and comprehensive utilization way out for zinc-bearing dust and biological sludge. © 2024 Elsevier B.V.