Characterization and analysis of typical metallurgical dust for rotary hearth furnace and its mechanism for microwave reduction roasting

The rotary hearth furnace is currently the mainstream technology for treating iron and steel metallurgical dust, yet its practical operation still faces challenges such as poor reduction homogeneity of pellets, difficulty in deep dezincification, and challenges in the synergistic optimization of key performance indicators. This study first systematically analyzed the raw material properties of typical metallurgical dust for rotary hearth furnace processing and investigates its effectiveness during microwave reduction roasting. Subsequently, Maps statistical analysis was employed to visualize and quantify the reduction homogeneity and pore structure characteristics of the pellets. Finally, a stepwise EDS（energy dispersive spectroscopy） analysis method was adopted to conduct a systematic investigation into the zinc phase evolution and dezincification mechanism, from the macroscopic to the microscopic scale. The results indicate that the iron phases in the metallurgical dust primarily include Fe_xO, Fe, Fe₂O₃, and Fe₃O₄, while the zinc phases consist of ZnS, ZnFe₂O₄, and ZnO. All raw materials exhibit excellent heating characteristics within the microwave field. Compared to conventional roasting, microwave roasting can increase the metallization rate of metallized pellets by approximately 15 percentage points, raise the dezincification rate by about 20 percentage points, and enhance the compressive strength by roughly 1 kN. Microwave roasting synchronously improves the reduction degree, structural compactness, and dezincification effectiveness across different internal zones of the metallized pellets, while also enhancing the uniformity of radial reduction and longitudinal dezincification, demonstrating advantages in low carbon emissions and high efficiency. Furthermore, a typical negative correlation exists between the distribution characteristics of the metallization rate and the residual Zn content within the pellets, providing an effective basis for indirectly inferring the distribution features of residual zinc and facilitating simple, intuitive analysis of its distribution patterns. Concurrently, sulfur present in the metallurgical dust is difficult to remove effectively during the reduction roasting process and tends to capture zinc as ZnS or （Zn,Fe）S solid solutions, leading to suboptimal dezincification. Microwave roasting can mitigate this capture and fixation of zinc. Through the characterization of typical metallurgical dust for rotary hearth furnaces, combined with Maps statistical analysis and stepwise EDS analysis, this study systematically elucidates the mechanism of microwave roasting, reveals its significant effects and operative mechanisms, and provides theoretical foundation and technical guidance for the low-carbon and high-efficiency resource utilization of metallurgical dust.