硅铝调控与晶种添加对水热法稳定垃圾焚烧飞灰中重金属的影响研究

发布时间：2018-03-01 07:04

  本文关键词： 水热法 活垃圾 飞灰 重金属 雪硅钙石 晶种　出处：《重庆大学》2016年硕士论文　论文类型：学位论文

【摘要】：近年来我国生活垃圾焚烧处理量快速增长,垃圾焚烧过程中产生了大量焚烧飞灰。飞灰因含有重金属、二VA英等污染物,被国家列为危险废弃物,需要进行无害化处理。近年来国内外学者对飞灰中重金属的稳定化进行了大量的研究。但是目前的重金属稳定化方法存在二次污染高、设备昂贵、能耗高等问题。针对这些问题,本文依托重庆市前沿与应用基础研究项目(CSTC2014jcyjA20015),开展了针对垃圾焚烧飞灰中重金属稳定化的实验和理论研究。本研究的主要内容及结论如下:(1)针对炉排炉飞灰硅铝含量较低的特点,采用粉煤灰、膨润土、高岭土为硅铝调理剂,开展了硅铝添加下水热稳定生活垃圾焚烧飞灰重金属的研究。结果表明,在飞灰水热处理中添加粉煤灰、膨润土、高岭土均合成了雪硅钙石等对重金属具有稳定效果的沸石类晶体。水热条件下分别添加三种硅铝调理剂使飞灰水热产物重金属浸出毒性显著降低,远远低于危废鉴别标准,并可以抑制水热反应过程中Pb、Zn向液相中的转移,但三种调理剂在水热条件下稳定飞灰中重金属的效果没有显著差异。同时发现高温有利于雪硅钙石的合成,但会导致Pb、Zn等重金属向水热反应液相中的转移量增大。此外修正的BCR多步连续提取的实验结果表明,水热产物中重金属Pb向更稳定的形态转化。(2)采用水热法合成雪硅钙石晶体并对其重金属吸附能力进行了表征。结果表明:采用二氧化硅,氢氧化铝,碳酸钙,氢氧化钠,去离子水为原料,在150℃下成功合成了雪硅钙石晶体,且反应时间为8d时雪硅石晶体纯度较高。雪硅钙石晶体对Pb2+、Zn2+、Cu2+、Cd2+、Cr3+吸附量分别达到了141.41mg/g、59.75 mg/g、43.09mg/g、46.08mg/g、20.10mg/g,同时浸出毒性测试结果表明被吸附后的重金属具有很好的稳定性。但当重金属溶液中含有多种重金属时,雪硅钙石对Cd2+吸附量显著下降。(3)进一步开展了硅铝添加及晶种诱导下水热稳定飞灰重金属的研究。结果表明:在飞灰水热处理中混合添加15%粉煤灰和15%硅藻土作为硅铝调理剂,200℃下雪硅钙石的生成量明显高于单一添加30%的粉煤灰,并且明显抑制了水钙铝榴石的生成,这表明混合添加粉煤灰和硅藻土时反应体系中的元素组成更适合雪硅钙石的生成;在反应体系中加入3%的雪硅钙石晶种后,200℃下雪硅钙石的出峰时间提前6个小时;150℃下添加3%雪硅钙石晶种成功诱导合成了雪硅钙石,并抑制了水铝钙石的生成,这表明晶种添加可以加速雪硅钙石的生成,并能提高对原料的适应性,还可以抑制杂晶的生成。晶种的添加显著降低了水热产物中重金属Pb和Zn的浸出浓度,并可以显著加速飞灰中Pb和Zn的稳定。总之,在水热法稳定飞灰重金属的过程中,采用硅铝添加和晶种诱导可以显著提高飞灰重金属的稳定效果,降低反应温度,缩短反应时间,达到了提高稳定效果、降低能耗的目的,具有工业化应用的前景。
[Abstract]:In recent years, the incineration capacity of domestic solid waste (MSW) in China has increased rapidly, and a large number of fly ash has been produced in the process of MSW incineration. The fly ash has been classified as hazardous waste by the country because of its heavy metal, diVA and other pollutants. In recent years, scholars at home and abroad have done a lot of research on the stabilization of heavy metals in fly ash. However, the current methods of heavy metal stabilization have high secondary pollution and expensive equipment. Problems such as high energy consumption. Based on CSTC2014jcyjA2001515, an experimental and theoretical study on the stabilization of heavy metals in fly ash from MSW incineration was carried out in this paper. The main contents and conclusions of this study are as follows: 1) aiming at the low content of Si-Al in fly ash of grate furnace. Using fly ash, bentonite and kaolin as silane and aluminum conditioning agent, the heavy metal in fly ash of solid waste incineration was studied by adding silica and aluminum into water heat treatment. The results showed that the addition of fly ash and bentonite in hydrothermal treatment of fly ash, bentonite, etc. Zeolites with stable effect on heavy metals have been synthesized from kaolinite. Under hydrothermal conditions, the leaching toxicity of heavy metals in hydrothermal products of fly ash is significantly reduced by adding three kinds of silicon-aluminum conditioning agents, which is far lower than the identification standard for hazardous wastes. It also inhibited the transfer of PBN Zn to liquid phase during hydrothermal reaction, but there was no significant difference between the three conditioners in stabilizing heavy metals in fly ash under hydrothermal conditions. At the same time, it was found that high temperature was beneficial to the synthesis of snow silicalite. However, the transfer amount of heavy metals such as Pb, Zn and other heavy metals into the hydrothermal reaction liquid phase will be increased. In addition, the experimental results of modified multi-step continuous extraction of BCR show that, The heavy metal Pb in hydrothermal products was transformed into a more stable form. The crystal was synthesized by hydrothermal method and its adsorption capacity of heavy metals was characterized. The results showed that silica, aluminum hydroxide, calcium carbonate, sodium hydroxide were used. The silica crystals were successfully synthesized from deionized water at 150 鈩，

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