Chlorine transformation during iron ore sintering co-processing of MSWI fly ash: Phase evolution, metal coupling, and...

Co-thermal treatment of municipal solid waste incineration fly ash (IFA) with iron ore fines offers a route for hazardous waste disposal and resource recovery in existing metallurgical processes. However, the coupled migration of chlorine and metals and its effects on environmental risks and sintering performance remain unclear. This study combined multiscale characterization and thermodynamic calculations to clarify chlorine evolution, migration, and enrichment during IFA co-sintering, while evaluating metal leaching, sinter quality, and dioxin emissions. Chlorine followed a fluxing-chlorination-trapping pathway. Above 600 °C, PbCl₂(g) and ZnCl₂(g) were the main gaseous carriers, while IFA-derived chlorides promoted early eutectic liquid formation, ion diffusion, and interfacial reactions. Above 1000 °C, Fe-Ca-Si-Al melts formed, which transformed into composite calcium ferrite or glass phases during cooling and solidification. This promoted the retention of part of the residual Cl as matrix-bound species with lower mobility. When the IFA content was 1 wt%, the volatilization of chlorine in IFA increased by 29.72%, and the volatilization rates of Pb and Zn increased by 17.04% and 35.36%, respectively. The degradation efficiency of dioxins in IFA reached 99.85%. These results clarify the co-migration mechanism and define a feasible operating range for integrating IFA co-processing into existing ironmaking infrastructure.