Digestion of Solid Waste During Sintering-Pelletizing Process

Abstract

Municipal waste incineration fly ash (referred to as fly ash) is a significant solid by-product that requires safe treatment and resource utilization. We propose using fly ash instead of lime as part of the flux in the sinter process, owing to its alkaline composition. Through thermodynamic calculations and experimental verification, we found that CaO from fly ash can form complex calcium ferrite with Fe₂O₃, which can effectively replace lime to form the binder phase. The Al₂O₃ impurities present in fly ash promote the formation of acicular calcium ferrite, which improves the reducibility and mechanical strength of the sintered ore. However, an Al₂O₃ content greater than 2% can deteriorate the metallurgical properties of the sintered ore. Alkaline metal chlorides in fly ash can improve the dissolution of Al₂O₃ and SiO₂ in silicate, but most are volatilized, with little effect on the binder phase. The best metallurgical properties were obtained when fly ash replaced 25% lime as the sintering alkaline flux. Replacing lime with fly ash during sintering has promising application prospects.