【作者】 罗春晖；

【导师】 刘振鸿；

【作者基本信息】 东华大学 ， 环境工程， 2004， 硕士

【摘要】 生活垃圾焚烧飞灰是全世界公认的危险废物，由于飞灰中含有大量能被水浸出的重金属、盐类，另外飞灰中的有机污染物质也是不可忽视的问题，因此我国规定飞灰须经适当处理达到危险废物填埋场的进场要求后进入危险废物填埋场。如果采用简单的水泥固化或者药剂固化等处理后进入危险废物填埋场，一是会带来巨额的处理费用，仅上海的飞灰的年处理费用将达到亿元；二是飞灰当中的重金属将存在成千上万年，但填埋场的寿命却只有100多年，因此，寻求合适的飞灰的处置方法对于解决生活垃圾焚烧厂的运行和推广意义重大。本课题提出复合式水洗-稳定化处理工艺处理生活垃圾焚烧飞灰，并进行了一系列的试验研究，探讨并分析了水洗-稳定化处理生活垃圾焚烧飞灰的可行性工艺条件和机理研究。 本课题针对飞灰复合式水洗-稳定化处理方面进行了大量的研究。试验采用的飞灰为上海御桥生活垃圾焚烧厂的飞灰。试验对飞灰进行了元素组成分析，重金属形态分析，X射线衍射测试，分别对飞灰直接稳定化和复合式水洗-稳定化进行了对比试验分析。实验结果的评价指标主要是浸出毒性，重金属的去除效率，另外重量和pH值的变化也是评价的指标之一。 实验结果表明，上海御桥生活垃圾焚烧厂的飞灰具有浸出毒性，其中Pb的浸出毒性(15.6mg／L)超过国家限定标准(3mg／L)。Pb、Cd、Zn和Cr是飞灰中重金属污染的主要来源。飞灰中的Pb和Zn主要以铁-锰相和残余相的形式存在。因此，飞灰中的重金属大部分是以水溶态的形式存在。飞灰经过水洗-稳定化后可以达到国家危险废物浸出毒性鉴别标准。 飞灰复合式水洗-稳定化的实验结果表明(1)上海浦东御桥垃圾焚烧厂飞灰的最佳水洗条件为2#实验方案，即：110(次／min)搅拌速度下，水／飞灰(重量比)为25，每次浸出时间为15min，并经过循环水洗2次；(2)确定水洗处理后，水泥固化处理的最佳原料配比为(飞灰-水洗污泥):水泥=4:1；(3)2#飞灰经过10min水洗处理后的水洗废液在pH6.5—7.5范围内能达到排放标准。 本课题提出的复合式水洗-稳定化处理的优点主要有：(1)对上海浦东御桥垃圾焚烧厂的水洗飞灰—污泥来说，与原始飞灰直接水泥固化处理的最佳原料配比为飞灰:水泥=2:1相比，经过水洗后处理的飞灰所消耗水泥的量减少50％，因此，复合式水洗-稳定化处理减少了稳定化过程消耗的水泥，并且在节省费用的同时更好地实现了飞灰的减容化、减重化；(2)经过水洗-稳定化后的飞灰经过浸出东华大学硕士学位论文生活垃圾焚烧飞灰水洗一稳定化试验研究毒性测试，能达到国家危险废物浸出毒性鉴别标准。 飞灰水洗溶液中各重金属含量均未超出国家污水排放标准，不需要进行特别处理后就能回用或直接排放;而水洗污泥中Cd、Zn两种重金属含量偏高，需要进行进一步处理后才能回用或填埋。考虑到水洗污泥的量相对较少，因此本课题提出将水洗污泥与水洗飞灰混合一块进行后续的稳定化处理，减少了处理工艺。 相比未经过水洗处理的飞灰稳定化过程，经过水洗处理后的飞灰更易子达到稳定化的效果，其原因可能是由于水洗提高了重金属水溶态化合物的组分，并转化了大部分重金属化合物为惰性成分，使重金属稳定化过程更容易实现;同时，水洗过程还洗去了大量无机盐组分(氯盐、磷酸盐等)，相对未进行水洗处理的稳定化处理而言，水洗过程使重金属组分转化为了更容易进行水泥稳定化反应的形式。更多还原

【Abstract】 Disposal of MSWI fly ash into ordinary landfill sites poses serious environmental problems, principally because this material contains high concentrations of leachable heavy metals. Thus, as a by-product, MSWI fly ash colleted by the baghouse or electrostatic precipitator is considered hazardous and should be properly treated. Traditionally, fly ash is sent to a hazardous landfill, after preliminarily solidified by cement or stabilized by chemical agents. Consequently, the cost for the treatment of MSWI fly ash is quite high. On the other hand, the life of heavy metals in the solidified products of fly ash may exist for a long time, but the life of hazardous landfill may be much shorter. Hence, it is necessary to seek for alternatives for fly ash treatment other than landfill or high temperature vitrification. The objective of this research was to investigate the feasibility of a combined washing-immobilisation process as a means of optimising the disposal of fly ash resulting from municipal solid waste incineration (MSWI) in cementitious matrices.The type of MSWI fly ash used in this study was collected from the baghouse of Shanghai Yuqiao incineration plants. Characterization involved chemical and physical analyses, observation under Environmental Scanning Electron Microscope (ESEM), X-ray Diffraction (XRD), Atomic Absorption Spectrometry (AAS) and Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) analyses. Toxicity Characteristic Leaching Procedure (TCLP) tests were performed on this research to assess the likehood of heavy metals being released into the environment. The benefits of water-immobilisation treatment of MSWI fly ash are twofold: namely, the cost savings stemming from reduction in the cement used, and the ecological advantage of ensuring a final destination for the ash.The experiment results indicate: The leaching toxicity for Shanghai Yu Nong MSWI fly ash is tested and found that Pb content in the leaching solution (15.6mg/L) exceed the toxicity standard set by the China regulations (3mg/L); The main pollution of fly ash comes from Pb, Cd, Zn and Cr. The leaching toxicity for fly ash samples after water-immobilisation treatment can meet the Chinese Identification standard for hazardous wastes. A two-stage washing pre-treatment with water (ambient temperature, water/solid (w/s) weight ratio=25, mixing time=15min, for each stage of treatment) is enough to maximize the incorporation of fly ash into cementitious matrices. Furthermore, an ash+sludge/cement ratio of 4.0 on a solid basis is enough to immobilize the fly ash. Besides, a wastewater produced by washing pre-treatment of flyash meets the requirements of China wastewater discharge regulations under pH condition between 6.5 and 7.5.Setting and leaching tests on cementitious mixes prove that the hazardous sludge produced from wastewater treatment can be completely mixed with washed fly ash and this mixture can be incorporated into cementitious matrices to a great extent without the risks of an unacceptable delay of cement setting and excessive heavy metals leachability from solidified products.The better performance of combined washing-immobilisation process as compared with immobilisation process of unwashed fly ash may be ascribed primarily to the ability of the washing step in promoting the formation of hydrate phases that incorporate and/or convert heavy metal compounds into less reactive forms and, secondarily, to its ability of removing significant amounts of alkali chlorides and sulphates from fly ash. As a result, MSWI fly ash is transformed into a material that adversely affects cement hydration to a much lower extent than unwashed fly ash.LUO Chunhui (Environmental Engineering) Supervised by: Associate Prof. LIU Zhenghong更多还原