Application of microwave energy in the destruction of dioxins in the froth product after flotation of hospital solid waste incinerator fly ash

et al. 2017

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Our previous study demonstrated flotation to be effective in removing carbonaceous matter and dioxins from fresh fly ash in medical waste incinerators (MWIs). However, flotation of weathered fly ash seems to be difficult because of the oxidation of the ash surface and the presence of hydrophilic unburned carbon. Three types of surfactants namely nonionic Tween 80, anionic sodium dodecyl sulfate (SDS) and cationic CTAB were employed at different doses to improve flotation performance. Results indicated that Tween 80 exhibited superior decarburization performance compared with SDS and CTAB. The effect of surfactants on dioxin removal was found to correspond to the carbon removal from MWI fly ash. The optimal removal yields (90.6% of carbonaceous matter and 88.6% of dioxins) were obtained when 5% (w/w) Tween 80 was added. However, an excessive dose might cause the dissolution of dioxins.

Section: Introductionmentioning

confidence: 99%

Effects of Surfactants on the Removal of Carbonaceous Matter and Dioxins from Weathered Incineration Fly Ash

et al. 2017

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“…2). This indicates that the acid soluble fraction is very high for these heavy metals, which bound to the speciation of the carbonate (Wei et al, 2016b). The oxides and hydroxides would be dissolved at a low pH value.…”

Section: Results Of Acid Leachingmentioning

confidence: 99%

Two-Step Flotation Treatment for Removal of Toxic Matter from Hospital Solid Waste Incinerator Fly Ash

et al. 2017

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Application of two-step flotation for removing dioxins and heavy metals from hospital solid waste incinerator (HSWI) fly ash was studied. In the first step, decarburization flotation was executed to remove dioxins from raw fly ash. The second step of precipitation flotation was carried out to recycle the toxic metals in the residual slurry. Finally, an acid leachingsulphide precipitation-flotation method was proposed. The results showed that carbon removal rate was 90.7%, and the dioxin removal percentage was 91.0% during decarburization flotation. And Zn, Pb and Cu in residual slurry were acidleached with the removal efficiencies being 91.3%, 79.2% and 85.6%, respectively. The optimum sulphidation condition of heavy metals in the residual slurry were Na 2 S molar ratio of 1.4 and sulphidation time of 30 min. Subsequently, precipitation flotation could recover 49.9% of Zn, 42.0% of Pb and 48.7% of Cu from the raw fly ash. After the two-step flotation, the toxicity of the tailings reduced considerably, and the tailings could be disposed in landfill. Therefore, this twostep flotation treatment of HSWI fly ash may result in both detoxification and potential resource recovery.

“…The concentrations of 17 toxic PCDD/Fs congeners (2,3,7,8-substituted) were analyzed using isotope dilution high-resolution gas chromatographymass spectrometry. Our PCDD/F analysis method was described in a previous study (Wei et al, 2016a). The destruction efficiency of PCDD/Fs were calculated for both gaseous PCDD/Fs vaporized or desorbed from the samples during reburning treatment and adsorbed by XAD-2 resin, and for solid-phase PCDD/Fs remained on the fired product.…”

Section: Methodsmentioning

confidence: 99%

“…In facilities that use rotary kilns, the primary and secondary combustion chambers are operated at temperatures of 800°C and 1200°C, respectively (Gao et al, 2009). At the end of the incinerator, a large amount of powder activated carbon (PAC) is injected into the exhaust gas to ensure that the concentration of PCDD/Fs in the flue gas remains lower than that specified by the new Chinese emission standards [0.1 toxicity equivalent quantity (TEQ) in ng m ] Wei et al, 2016a). Thus, PCDD/Fs and other organic pollutants such as PAHs, CBs, CPs and PCBs, in the flue gas are transferred to HSWI fly ash (Lee et al, 2004;Wang et al, 2006a;Cheruiyot et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Reburning Treatment of the Froths Obtained after the Flotation of Incinerator Fly Ash

Liu²,

et al. 2017

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Flotation has been proven to successfully remove most polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) and carbon constituents from hospital solid waste incinerator (HSWI) fly ash. The resultant froths contain large quantities of carbon constituents that can reburn in the incinerator. In this paper, the reburning behavior of froths at temperatures from 800°C to 1200°C was compared with that of HSWI fly ash. Results showed that the destruction efficiency of PCDD/Fs was higher in the froths than in the fly ash at the same reburning temperature. The destruction efficiencies of PCDD/Fs in the froths exceeded 98% at temperatures higher than 1000°C. The volatilization ratio of Pb, Zn, and Cu was lower in the froths than in the fly ash. Furthermore, reburning of the froths can achieve energy recovery of the carbon constituents. Therefore, flotation followed by reburning treatment in a combustion chamber could be a suitable process for the detoxification and reutilization of HSWI fly ash.