Metal Behavior during Vitrification of Municipal Solid Waste Incinerator Fly Ash

This study described the mass distribution of metals and the crystalline characteristics of slag during the vitrification of incinerator fly ash. The fly ash, mainly composed of Ca (180,000 mg/kg), Si (25,500 mg/kg), Pb (19900 mg/kg), and Zn (14,400 mg/kg), was vitrified with cullet at a basicity of 0.921 in an electric heating furnace. After vitrification, metals with low boiling points (Cd, Pb, and Zn) vaporized into flue gas as particulate phase. High levels of Pb (315,000 mg/kg) and Zn (226,000 mg/kg) made the particulate phase worth reclaiming. No ingot formed due to lack of ingot forming metals, and thus metals with high boiling points mainly stayed in the slag. After being identified by X-ray diffractometer (XRD) analysis, the major crystalline phases of the slag were found to be Ca2SiO4 and CaSiO3, which coincided with the results of scanning electron microscopy (SEM). The results of the toxicity characteristics leaching procedure (TCLP) suggest that recycling the slag could be taken into consideration. The overall results indicate that vitrification is a promising technology that is able to transform incinerator fly ash into stable slag, reduce secondary environmental pollution, and transform valuable metals (Pb and Zn) in a recoverable form.