Characterization of zinc vapor condensation in fly ash particles using synchrotron X-ray absorption spectroscopy

Abstract

Heavy metals released from municipal solid waste incinerators have become a major environmental concern. A comprehensive knowledge of metal vapor condensation in fly ash particles during incineration is essential for alleviating heavy metal toxicity, and for optimizing incineration process parameters and flue-gas cleaning systems. In this paper, the condensation of zinc vapor during flue-gas cooling in a 200 t/d fluidized bed incinerator and a 150 t/d moving grate incinerator was characterized and comparatively studied using high resolution synchrotron X-ray absorption spectroscopy (XAS). Principal component analysis, target transformation, and linear combination fitting were employed to identify zinc species directly from size fractionated fly ash particles. The chemical reaction behaviors of different zinc species were described by thermodynamic equilibrium simulations. Consistent with previous theoretical analysis and laboratory scale tests, the condensation behavior of zinc in an industrial incineration system is mainly affected by the sulfur/chlorine ratio and the inorganic particulates. It is found that zinc chloride is the major zinc species in a moving grate incinerator but willemite dominates in the fluidized bed incinerator. The high sulfur and silica/alumina particle concentration in the fluidized bed system changes the condensation propensity of vapors of Zn compounds. Adjusting the concentrations of SO 2 in flue-gas can inhibit the formation of zinc chlorides. Silica, alumina, aluminosilicates, and calcium-based compounds are potential sorbents for transforming zinc to less harmful species. To prevent toxic zinc species contained in fine particles from escaping into the atmosphere, wet scrubbers are more suitable for cleaning flue-gases in moving grate incineration systems, while improving the efficiency of dust removal is more important for fluidized bed incineration systems.

Identification and Quantification of Chemical Forms of Cu and Zn in MSWI Ashes Using XANES

“…ZnO and/or Zn(OH 2 ), hydrozincite (Zn 5 (CO 3 ) 2 (OH) 6 ), and ZnCl 2 were also commonly found in both BA and FA. Apart from the presence of Zn 4 Si 2 O 7 (OH) 2 • H 2 O (and absence of willemite), the Zn forms detected in FA were similar to those reported by Cai and co-workers 40 in FA from the incineration of municipal waste in China. There were also similarities with the Zn speciation reported by Takaoka and co-authors, 18 with the exception of ZnS, which is unlikely to be stable in FA (see later discussion).…”

“…A high content of ZnCl 2 has been reported in several previous studies of FA from waste incineration. 18,20,40 Table 4. Results of Zn Speciation from LCF of Reference Spectra to XANES Spectra of Ash Samples The presence of hemimorphite has rarely been reported in the literature but occurred in all ashes in this study.…”

“…A high content of ZnCl 2 has been reported in several previous studies of FA from waste incineration. ,, Kitamura and co-authors interpreted the co-location of Zn and Cl in FA as either ZnCl 2 or K 2 ZnCl 4 adsorbed to the particle surfaces. In the Supporting Information, modeled XANES spectra of ZnCl 2 and K 2 ZnCl 4 are presented, showing clear resemblances.…”

Chromium and Zinc Speciation in Airborne Particulate Matter Collected in Ulaanbaatar, Mongolia, by X-Ray Absorption Near-edge Structure Spectroscopy

“…Nevertheless, Zn chloride (along with Zn silicate) was found as significant component of Zn in fly ash particles sampled directly from the stack of coal and municipal solid waste (Cai et al, 2015, Yu et al, 2009. Origins and formulation of this compound in atmospheric particles can be related to anthropogenic sources.…”

Removal of the Homolog Tellurium of Polonium by SiO2 Nanofiber Filter for Lead Alloy-Cooled Reactors

“…Nanofibers with small pore size, high throughput, and high filtration accuracy are regarded as candidate filtration materials in the field of nuclear waste treatment [26][27][28]. According to the literature, the whole process of evaporating and capturing volatile materials involves sub-processes of volatilization, condensation, and solidification [29][30][31], which are also applicable for the current study. Polonium-containing vapors migrate from liquid leadbismuth pools to the cover gas at high temperatures.…”