title: Removal of toxic and alkali/alkaline earth metals during co-thermal treatment of two types of MSWI fly ashes in China.
abstract: This study aims to vaporize heavy metals and alkali/alkaline earth metals from two different types of fly ashes by thermal treatment method. Fly ash from a fluidized bed incinerator (HK fly ash) was mixed with one from a grate incinerator (HS fly ash) in various proportions and thermally treated under different temperatures. The melting of HS fly ash was avoided when treated with HK fly ash. Alkali/alkaline earth metals in HS fly ash served as Cl-donors to promote the vaporization of heavy metals during thermal treatment. With temperature increasing from 800 to 900°C, significant amounts of Cl, Na and K were vaporized. Up to 1000°C in air, less than 3% of Cl and Na and less than 5% of K were retained in ash. Under all conditions, Cd can be vaporized effectively. The vaporization of Pb was mildly improved when treated with HS fly ash, while the effect became less pronounced above 900°C. Alkali/alkaline earth metals can promote Cu vaporization by forming copper chlorides. Comparatively, Zn vaporization was low and only slightly improved by HS fly ash. The low vaporization of Zn could be caused by the formation of Zn2SiO4, ZnFe2O4 and ZnAl2O4. Under all conditions, less than 20% of Cr was vaporized. In a reductive atmosphere, the vaporization of Cd and Pb were as high as that in oxidative atmosphere. However, the vaporization of Zn was accelerated and that of Cu was hindered because the formation of Zn2SiO4, ZnFe2O4 and ZnAl2O4 and copper chloride was depressed in reductive atmosphere.
authors: State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, 430074 Wuhan, Hubei, China.
authors: Jie
authors: J
authors: Yu
authors: State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, 430074 Wuhan, Hubei, China. Electronic address: yuqiao@hust.edu.cn.
authors: Yu
authors: Y
authors: Qiao
authors: State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, 430074 Wuhan, Hubei, China.
authors: Limei
authors: L
authors: Jin
authors: State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, 430074 Wuhan, Hubei, China.
authors: Chuan
authors: C
authors: Ma
authors: Department of Chemical Engineering, Imperial College London, London SW7 2AZ, United Kingdom.
authors: Nigel
authors: N
authors: Paterson
authors: State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, 430074 Wuhan, Hubei, China.
authors: Lushi
authors: L
authors: Sun
mesh_terms: D000468:Alkalies / Q000032:analysis*; D060729:Coal Ash / Q000737:chemistry*; D017745:Incineration; D008673:Metals, Alkaline Earth / Q000032:analysis*; D019216:Metals, Heavy / Q000737:chemistry*; D062611:Solid Waste / Q000032:analysis*; D013696:Temperature; D014835:Volatilization
chemical_list: D000468:Alkalies; D060729:Coal Ash; D008673:Metals, Alkaline Earth; D019216:Metals, Heavy; D062611:Solid Waste
keywords: Alkali/alkaline earth metal; Fly ash; Heavy metal; Municipal solid waste; Thermal treatment