Co-treating MSWI fly ash in iron ore sintering process: Influence of water-washing and roll forming pretreatment on dioxins emission

Abstract

Co-treating municipal solid waste incineration fly ash (MSWI-FA) in high-temperature iron ore sintering process is winning great concern. Most of the previous studies were about the co-treatment of raw MSWI-FA (without water washing) in sintering process. Although the content of dioxins in MSWI-FA was reduced, the high chlorine content promoted the secondary synthesis of dioxins and had a negative impact on the quality of sinter. This investigation focused on the emission characteristics and regulation approach of dioxins as co-treating MSWI-FA. The results showed that when MSWI-FA was added without pretreatment, the emission concentration of dioxins in sintering flue gas reached 4.28 ng I-TEQ/Nm³ . After water-washing pretreatment, the chlorine in MSWI-FA was significantly reduced, which inhibited the synthesis of dioxins via de novo reaction. The dioxins decreased significantly to 1.44 ng I-TEQ/Nm³ . Based on the washing pretreatment, the MSWI-FA was further prepared into lumps, which inhibited the dispersion of Cl-containing MSWI-FA particles in mixtures and reduced the active sites of dioxins synthesis, thereby hindering the dioxin synthesis path. The emission concentration of dioxins in sintering flue gas was further reduced from 1.44 ng I-TEQ/Nm³ to 1.15 ng I-TEQ/Nm³ . Adding 0.5% water-washed fly ash lumps had little effect on sintering indexes and dioxins concentration in flue gas. The research results laid a certain foundation for the large-scaly recycling of MSWI-FA.