分段水热法稳定城市生活垃圾焚烧飞灰中重金属的实验研究

发布时间：2018-02-07 14:18

  本文关键词： 分段水热法 碱溶预处理 城市生活垃圾焚烧飞灰 重金属　出处：《华中科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：焚烧法因其工艺简单可靠、减容量大和能源回收等显著优点逐渐成为处理城市生活垃圾的主要方法之一。然而垃圾焚烧产生的飞灰由于含有较高浓度重金属及二VA英等污染物而被公认为危险废物需要进一步处理。针对目前新兴的水热法处理垃圾焚烧飞灰过程中产生含有较高浓度铅、锌等重金属的残液需要处理并且在合成过程中会产生再吸附等问题,本文以流化床垃圾焚烧炉产生的飞灰为研究对象,通过添加碱溶预处理步骤,实现了分段水热处理垃圾焚烧飞灰工艺,以期更好的稳定其中的重金属。1.研究了四种固体废物浸出方法对城市生活垃圾焚烧飞灰重金属浸出结果的影响。结果表明:采用醋酸缓冲液作为浸提剂的HJ/T 300方法和TCLP方法,铅和锌的浸出量较高;由于垃圾焚烧飞灰自身具有高碱性,采用硫酸/硝酸混合液作为浸提剂的HJ/T 299方法因不具备缓冲能力,铅和锌的浸出量最低,反而采用中性去离子水作为浸提剂的HJ 577方法较HJ/T 299方法铅和锌的浸出量还要略高。2.开展了水热法处理垃圾焚烧飞灰的主要影响因素的实验研究,结果表明:垃圾焚烧飞灰在一定的NaOH浓度和反应温度条件下经过水热反应生成了诸如加藤石(Katoite)、雪硅钙石(Tobermorite)和方纳石(Sodalite)等类沸石矿物,同时使得合成产物的浸出毒性有效降低,但当NaOH浓度超过3 mol/L时仅有方纳石(Sodalite)生成,说明过量的碱度反而会阻碍水热反应的结晶过程,当反应温度140℃时,合成产物的浸出毒性反而会上升,说明过高的反应温度会使水热合成产物稳定重金属的效果降低。最终确定最优的反应条件为NaOH浓度1 mol/L、反应温度120℃。3.通过碱溶预处理步骤的添加,改进了水热法稳定垃圾焚烧飞灰的处理工艺。探讨了碱溶预处理过程溶出铅、锌的最优条件为反应温度为70℃、反应时间为50分钟、碱浓度为4 mol/L。并对合成产物进行浸出毒性分析,结果表明:分段水热法能更加有效的稳定垃圾焚烧飞灰中重金属,并减少合成产物及残液的二次污染风险。
[Abstract]:The incineration process is simple and reliable. Large capacity reduction and energy recovery have gradually become one of the main methods for the treatment of municipal solid waste. However, fly ash from incineration is recognized as dangerous because of its high concentration of heavy metals and other pollutants such as diVA. Hazardous wastes need further treatment. High concentrations of lead are produced during the treatment of waste incineration fly ash by new and emerging hydrothermal processes, Zinc and other heavy metal residues need to be treated and readsorbed in the process of synthesis. In this paper, fly ash produced by fluidized bed incinerator is taken as the research object. The process of incineration fly ash by subsection hydrothermal treatment is realized. The effects of four solid waste leaching methods on the heavy metal leaching of municipal solid waste incineration fly ash were studied. The results showed that the HJ/T 300 and TCLP methods were used as extractant to extract the heavy metals from municipal solid waste incineration fly ash. The leaching amount of lead and zinc is high, and the leaching amount of lead and zinc is the lowest because the HJ/T 299 method which uses sulfuric acid / nitric acid mixture as extractant has no buffer capacity, because of the high alkalinity of waste incineration fly ash. On the contrary, HJ577, which uses neutral deionized water as extractant, is slightly higher than HJ/T 299 in the leaching of lead and zinc. The experimental study on the main factors affecting the treatment of waste incineration fly ash by hydrothermal method is carried out. The results show that under certain NaOH concentration and reaction temperature, waste incineration fly ash produces zeolite-like minerals such as Katoite, Tobermorite and Sodalite, which can effectively reduce the leaching toxicity of the synthesized products. However, when the concentration of NaOH is more than 3 mol/L, only mononalite is formed, which indicates that excessive alkalinity will hinder the crystallization process of hydrothermal reaction, and the leaching toxicity of the synthesized product will increase when the reaction temperature is 140 鈩，

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