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Abstract:In this study, eight fly ash samples and three bottom ash samples from different areas are collected for analysis of their physicochemical properties and emission content of dioxin precursors and metals. Their surface characteristics, their effects on dioxin precursors, and important aspects of the compositions of residual ash (fly ash and bottom ash) are investigated. Poly-chlorobenzenes (PCBzs) in the fly ash of a fluidized bed incinerator (FBI) are 7.35 to 357.94 µg/kg, and in that of a fire grate incinerator (FGI) are 6.74 to 96.52 µg/kg. The concentrations in bottom ash are the same (i.e., 2.23 to 2.99 µg/kg) regardless of the furnace type. The concentrations of polycyclic aromatic hydrocarbons (PAHs) in FGI fly ash samples (0.293 to 1.783 mg/kg) are less than these in samples from FBIs (1.820 to 38.012 mg/kg). Low boiling point PAHs (mainly 2-and 3-ringed PAHs) and high boiling point PCBzs (mainly H x CB and P e CBz) are the major constituents of residual ash. Different distributions of PCBzs and PAHs are mainly dictated by the incineration characteristics of FBI and FGI. Al and Fe, as non-toxic "light metals" are the major constituents of the residual ash, and Ni and Zn as non-toxic heavy metals play important roles in the total heavy metal. Cu, Pb, and Cr are the three major toxic heavy metals. The correlation of the metals and the dioxin precursors is discussed and distinguished.

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A mechanical mixture of lignite-based activated carbon (AC) and V 2 O 5 -TiO 2 -catalyst (CAT) is applied to destroy gasphase polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) at high concentration (9.8 ng I-TEQ Nm 23 ). Even at low temperature (160 C), the mix of AC/CAT shows high removal efficiency (RE) and destruction efficiency (DE). Varying the proportions of catalyst to AC has slight effect only on the DE-value, but the RE-value augments with rising ratio of AC, benefiting from enhanced adsorption on AC. When temperature is 160 C and the proportion of AC and CAT is 3:2, with oxygen concentration rising from 0 to 20%, the DE-value even amplifies from 27 to 82%, by conversion of V 41 O X into higher oxides. In the presence of ozone, PCDD/Fs are further broken down and the DE-values of high-chlorinated congeners surge. In the presence of ozone, AC breaks down to black brown flock, which contains more than 50 wt % carbons. Both reducing the content of AC and increasing the reaction temperature restrain the production of flock. The best condition occurred at 200 C in the presence of ozone with the DE of 98%, when the proportion of AC and CAT is 1:1.