生活垃圾焚烧飞灰固化体力学及重金属浸出特性

MECHANICS AND LEACHING CHARACTERISTICS OF HEAVY METALS IN STABILIZED MSWI FLY ASH

以苏州七子山生活垃圾焚烧厂产生的飞灰为研究对象,采用水泥作为固化剂,研究水泥飞灰固化体的应力应变特征及重金属浸出特性,并探讨了水泥飞灰配合比、养护时间等关键性因素对这些特性的影响。实验结果表明:较养护3 d的样品,其余养护时间的样品强度平均增长了约96.2%,而其破坏应变平均减小了56%。随着水泥含量和养护时间的增加,飞灰固化体的强度上升,而其破坏应变减小,该趋势主要归因于钙矾石(AFt)的形成促进了飞灰固化体强度的发展。较飞灰原样,飞灰固化体的重金属浸出浓度随着水泥含量、养护时间的增加而降低了38%~99%,重金属的迁移被限制,主要归因于水化硅酸钙(C—S—H)和钙矾石(AFt)的形成,以及飞灰和水泥水化反应创造的强碱性环境。

Taking the fly ash from Suzhou Qizi Mountain Municipal Solid Waste Incineration（ MSWI） Plant as the research object,the solidification/stabilization by ordinary portland cement as the binder was carried out. And influence of key factors like fly ash/cement proportion and curing time on strength and leaching of the solidified objects was evaluated. According to the test results,both cement/fly ash ratio and curing time had significant effects on the compressive strength,failure strain and leaching behavior. Compared with the specimens under 3 days＇ curing,the compressive strength of the samples after other curing time increased by around 96. 2%,and the failure strain decreased by about 56%. The increase of the cement content and curing time dominated the enhance of compressive strength of the solidified matrices,and the decrease of the failure strain,which was due to the formation of ettringite（ AFt）. Compared with the original fly ash,the concentration of heavy metals leached from the solidified matrices decreased by 38% ~ 99%,which were resulted from the restriction on the migration of heavy metals ions by many aspects,such as C-S-H gel,fomation of ettringte（ AFt）,and alkalic condition created by the reaction of fly ash and cement.