Sintering characteristics of CaO-rich municipal solid waste incineration fly ash through the addition of Si/Al-rich ash residues
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Thermal treatment is a promising technology for the fast disposal of hazardous municipal solid waste incineration (MSWI) fly ash in China. However, fly ash produced in grate incinerator (GFA) is rich in CaO and chlorides, which promote the formation of toxic hexavalent chromium [Cr(VI)] and ash agglomeration during the thermal process, inhibiting the thermal disposal of GFA. In this study, sintering characteristics of CaO-rich GFA were improved by adding Si/Al-rich MSWI ash residues. According to the results, ash agglomeration was well suppressed during thermal treatment of the mixed ash. Si/Al/Fe-compounds competed with un-oxidized Cr-compounds to react with CaO and suppressed Cr(VI) formation. Meanwhile, chlorides in GFA facilitated heavy metal volatilization from added ashes to the secondary fly ash, favoring the recovery of these metals. Ca-aluminosilicates was found as the main mineral phase in the thermally treated mixed ash, which has attractive potential for applications. The formation of the aluminosilicates made the heavy metals that remained in the treated mixed ash more stable than the thermally treated single ash.
KeywordsMSWI fly ash Sintering characteristics Ash mixing Heavy metals Agglomeration
This work was carried out by financial support of Key Project of Chinese National Programs for Fundamental Research and Development (973 program, 2011CB201505) and National Natural Science Foundation of China (Grants,51161140330, 51076053). The Analytical and Testing Center of Huazhong University of Science and Technology is acknowledged for the experimental measurements.
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