磷酸洗涤对垃圾焚烧飞灰热稳定性和重金属固定的影响

为抑制垃圾焚烧飞灰中重金属的溶出,研究了磷酸洗涤对重金属固定和飞灰热稳定性的影响。进行了水洗、磷酸洗涤、重金属的化学结合形态分析和焚烧飞灰的热分析试验。结果表明:水洗虽能有效去除焚烧飞灰中大部分可溶性氯盐,但会导致水洗液中Pb、Zn的浓度超标;磷酸洗涤后Zn的溶出率由水洗时的112.65mg/kg降低至2mg/kg左右,Pb的溶出浓度未检出,固留在灰样中重金属的残留态和有机态的比例都有不同程度的提高。结论是:磷酸洗涤不但能有效抑制重金属的溶出,还有助于改善重金属的化学稳定性和飞焚烧灰的热稳定性。

Effects of phosphoric acid washing on thermal stability and chemical stability of heavy metals of MSWI fly ash

The effectiveness of phosphoric acid washing of municipal solid waste was studied to reduce the effect of the high dissoluble chloride content and high alkalinity of incineration fly ash.The results show that the washing pretreatment eliminates most of the dissoluble chloride in the fly ash.When the fly ash is pretreated with de-ionized water washing,the Pb and Zn concentrations in the washing liquid exceed the waste water standards.The leaching of Zn was reduced to 2 mg/kg after phosphoric acid washing compared with de-ionized water washing with no Pb detected in the washing solution.The residual and organic bonds of the remaining heavy metals in the fly ash and the thermal stability of treated fly ash are both improved by phosphoric acid washing.Therefore,the chemical stability of the heavy metals in fly ash are both improved which significantly reduced the leachability of heavy metals.