Abstract
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.
Highlights
Due to the rapid growth of economic development, a large amount of municipal solid wastes (MSW) are generated in human activities
In the air pollution control processes of a incineration plant, a Ca(OH)2 slurry is commonly injected into semidry scrubbers to remove acid gaseous pollutants. (Ca(OH)2 may be used to reduce the formation of PCDD/Fs (Wang et al, 2012).) This injection of Ca(OH)2 slurry into semidry scrubbers usually produces basic fly ash with high level of Ca (~150,000 mg/kg or even higher) (Jung et al, 2005)
The toxicity characteristics leaching procedure (TCLP) result suggested that the slag was not a hazardous material (TEPA, 2006) and the leaching of metals would not cause secondary pollution
Summary
Due to the rapid growth of economic development, a large amount of municipal solid wastes (MSW) are generated in human activities. According to 2011 Taiwan Environmental Protection Administration (TEPA) report for the collection and transportation for MSW, there were 7,750,000 tons of MSW generated in Taiwan last year. The flue gas was controlled stringently by regulated emission standard for decades (TEPA, 2006a), but the disposal of the ashes was relatively ignored. During the MSW incineration process, 1,210,000 tons of ashes (fly ash + bottom ash) were generated last year (TEPA, 2011). The level of persistent organic pollutants in the fly ash collected from baghouse filters was much higher than that in other ashes (Wang et al, 2010b). Neither recycling nor cement can destroy the organic toxicity, and the recycling or solidification/landfill may cause secondary pollution
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
