固化飞灰形状及填埋方式对重金属浸出的影响

Effects of solidified Fly Ash Shape and Landfill Method on Leaching of Heavy Metals

为探究成型形状和填埋方式对生活垃圾焚烧飞灰固化体中重金属浸出的影响,设置固化体尺寸分别为10×10×10cm、10×10×2.5cm、DN=3cm(球),同时设置码放、散乱堆放2种填埋方式进行动态浸出试验.结果表明,在固化体开裂前,球状与长方体、整齐码放与散乱堆放的浸出液pH值存在显著差异;单位质量固化体重金属Pb、Zn、Cr累积浸出量随固液接触面积、堆填散乱度、液固比的增大而增加,固化稳定化飞灰中重金属的浸出符合缩芯模型且主要由扩散过程控制,试验前段Pb、Zn、Cr的2种速率常数与固化体成型比表面积、堆填散乱度、液固比正相关.因此,要减少生活垃圾焚烧厂原灰中重金属的浸出,提高生活垃圾填埋场共处置飞灰固化稳定化产物的安全性,固化体成型时应尽量缩小比表面积同时避免散乱填埋.

In order to explore the effects of molding shape and landfill method on the leaching of heavy metals in the solidified fly ash of municipal solid waste incineration,the size of solidified body was set to 10×10×10cm,10×10×2.5cm and DN=3cm(sphere)respectively,and at the same time set two landfill methods—orderly stacking and scattered stacking-for dynamic leaching test.The results showed that the leachate pH between spherical shape and cuboid shape,orderly stacking and scattered stacking were significantly different before the solidified body cracked;The cumulative leaching amounts of Pb,Zn and Cr per unit mass of solidified body increased with the increase of solid-liquid contact area,scattered degree of landfill and liquid-solid ratio.The leaching of solidified and stabilized fly ash conformed to the shrinking core model and was mainly controlled by the diffusion process.The two kinds of rate constants of Pb,Zn and Cr were positively related to solid-liquid contact area,scattered degree of landfill and liquid-solid ratio.Therefore,it is necessary to reduce the leaching of heavy metals from the raw ash of municipal solid waste incineration plants and improve the security of co-disposal of solidified and stabilized fly ash in the landfill sites.The surface area of solidified body should be minimized.And the solidified body should avoid being buried by using a scattered landfill method.