城市生活垃圾焚烧飞灰水泥固化技术研究

Study on technoloy of solidification of municipal solid wastes incineration( MSWI) fly ash by cement

用硫铝酸盐水泥对城市垃圾焚烧飞灰(简称飞灰)进行固化实验,研究了飞灰重金属浸出特性,分析了飞灰掺量、浸提剂p H值对重金属浸出特性以及飞灰掺量对不同龄期(3、7、28 d)飞灰固化体抗压强度的影响,并对飞灰及其固化体进行XRD分析。结果表明,在HJ/T 299-2007和HJ/T 300-2007两种不同浸出体系下,飞灰中Cu、Zn、Cd、Pb、Cr和Mn等重金属浸出浓度差别较大,建议应根据评价目标合理选择重金属浸出测量方法。其中,飞灰中Pb的浸出浓度超过《危险废物鉴别标准浸出毒性鉴别》(GB 5085.3-2007)限值的3.35倍,因此被列为危险废物,应妥善处理。除飞灰掺量小于40%时的固化体Cd符合标准,其余飞灰固化体Pb和Cd的浸出浓度仍超过《生活垃圾填埋场污染控制标准》(GB 16889-2008)限值,故达不到卫生填埋的要求。固化体抗压强度随飞灰掺量增大而降低,重金属浸出浓度与之相反。飞灰掺量为40%时,固化体中重金属浸出浓度随浸提剂p H值降低而增大,但p H值大于5时,未测出重金属浸出。XRD结果表明:飞灰中可溶性盐参与水泥水化反应,重金属Cr以CrO_2-4的形式固化于钙矾石中。

Incinerated municipal solid waste（ MSWI）,fly ash,was solidified by using sulfoaluminate cement in this study. The leaching of heavy metals from the MSWI fly ash was studied. Experiments were conducted to investigate the effect of the ratio of the MSWI fly ash to the solidified waste forms on the leaching properties and the compressive strength of solidified waste forms cured for 3,7 and 28 d. The relationship between the p H of the leaching agent and the leaching of heavy metals was also evaluated. The phases of the fly ash and its solidified waste forms were analyzed by X-ray diffraction（ XRD）. The results showed that the selection of the methods for leaching heavy metals by purposeful evaluation was mandatory given that the concentrations of leached heavy metals such as Mn,Zn,Cr,Cd,Pb,and Cu in the fly ash differed based on HJ / T 299-2007 and HJ / T 300-2007. Fly ash is classified as hazardous waste and should be treated properly considering that the concentration of leached Cd was 3. 35 times higher than that specified by the National Hazardous Waste Identification Standard（ GB 5085. 3-2007）. The concentration of Cd leached from all solidified waste forms,except those in which the fly ash content was less than 40%,and the concentration of Pb leached from all solidified waste forms still exceeded the Control Standard for Pollution in Landfills（ GB 16889-2008）. Therefore,the leaching toxicity of fly ash did not meet the requirements of the landfill standard. The compressive strength of the solidified waste forms decreased with increasing fly ash content,and the concentration of leached heavy metals showed the opposite trend.The leachate concentration increased when the p H of the leaching agent was lower,but no leaching of heavy metals was observed when the p H of the leaching agent was higher than 5. The XRD analysis suggested that the soluble salts in the fly ash reacted with the hydration products of SAC. Chromium was incorporated into ettringite in the form of CrO_2-4.