垃圾焚烧过程中半挥发性重金属排放特性及控制研究

发布时间：2018-08-20 11:23

【摘要】：垃圾焚烧因具有减容化、无害化、资源化等优点,成为很多国家主要的垃圾处理方式。但垃圾焚烧会引起有毒重金属污染,严重制约了垃圾焚烧技术的发展和应用。本文采用理论与实验相结合的方法,深入研究了垃圾焚烧过程中重金属Pb、Cd的排放特性及控制方法。首先,在管式炉上考察了无机氯(NaCl)、有机氯(PVC)、不同形态的硫(S、Na2S、 Na2SO4)以及吸附剂对重金属Pb、Cd挥发特性的影响。实验表明,无机氯(NaCl)、有机氯(PVC)均能有效地促进Pb、Cd的挥发；无机氯(NaCl)、有机氯(PVC)中氯释放特性不同导致其对Pb、Cd影响机理不同。不同形态S对重金属Pb、Cd挥发特性影响不同,低温下S、Na2S、Na2SO4对Pb、Cd挥发具有抑制作用；而高温下S、Na2SO4会促进Pb、Cd的挥发,Na2S会促进Pb的挥发,但对Cd表现出相反的作用。高岭土、沸石对重金属Pb、Cd具有一定的吸附作用,并且既存在物理吸附又存在化学吸附,而石灰石无明显吸附作用。其次,在小型流化床焚烧炉上对重金属Pb、Cd在PM10中的分布特性进行了研究,将在管式炉上表现出较好吸附效果的高岭土在小型流化床上进行吸附性能测试,并利用SEM/EDS/XRD等分析方法分析其吸附剂机理。实验结果表明,PM10中亚微米Pb、 Cd所占比例分别达到90%、85%；添加高岭土能够有效控制亚微米Pb、Cd排放,对亚微米Pb、Cd的最高捕集效率分别达83%、51%；高温下高岭土与重金属Pb、Cd蒸气反应并产生共晶融化,其产物为PbO·Al2O3·2SiO2、CdO·Al2O3·2SiO2;随温度升高,高岭土与重金属的共晶融化量增加,其共融物可促进高岭土对重金属蒸气的捕集,但温度过高会导致过量共晶融化,使高岭土的孔隙结构坍塌,捕集效率反而降低；Pb、Cd共存时,Pb会促进高岭土与Cd的反应,Cd能够抑制Pb与高岭土的过量共晶融化,1000℃时Pb、Cd产生相互促进作用。最后,基于吉布斯自由能最小法原理,利用热力学平衡计算法考察了温度、氯、硫和吸附剂等对Pb、Cd的挥发特性影响。计算结果表明,焚烧过程中氯易于与重金属Pb、Cd反应生成易挥发的氯化物,促进Pb、Cd的挥发；低温段硫会抑制重金属Pb、 Cd的挥发,而高温段影响不大。垃圾中的Na与C1、S的亲和性远强于Pb,使得Na在一定程度上抑制了S、Cl对Pb作用。CaO对Pb、Cd的吸附效果较差,Si02能够有效地吸附Pb、Cd,而A1203仅对Cd有一定的吸附效果。
[Abstract]:MSW incineration has become the main waste disposal method in many countries because of its advantages of reducing capacity, innocuity and resources. However, garbage incineration can cause toxic heavy metal pollution, which seriously restricts the development and application of MSW incineration technology. In this paper, the emission characteristics and control methods of heavy metal Pb / CD in MSW incineration were studied by combining theory with experiment. Firstly, the effects of inorganic chlorinated (NaCl), organochlorine (PVC), (Na2SO4) and adsorbent on the volatilization characteristics of heavy metal PBH CD were investigated in a tubular furnace. The results show that inorganic chlorinated (NaCl), organochlorine (PVC) can effectively promote the volatilization of PBN CD, and the different chlorine release characteristics in inorganic chlorine (NaCl), organochlorine (PVC) lead to different mechanism of its influence on PBN CD. Different forms of S have different effects on the volatilization characteristics of heavy metal Pb ~ (2 +) CD, and the volatilization of Pb ~ (2 +) CD can be inhibited by SbNa _ 2SO _ 4 at low temperature, while the volatilization of Pb ~ (2 +) by Na _ (2) so _ (4) can promote the volatilization of Pb under high temperature, but it has the opposite effect on CD. Kaolin and zeolites have a certain adsorption effect on heavy metal Pb ~ (2 +) CD, and there is both physical and chemical adsorption, but limestone has no obvious adsorption. Secondly, the distribution of heavy metal Pb, CD in PM10 was studied in a small fluidized bed incinerator. The adsorption performance of kaolin, which showed good adsorption effect on a tubular furnace, was tested on a small fluidized bed. The mechanism of the adsorbent was analyzed by SEM/EDS/XRD and other analytical methods. The results show that the proportions of Pb and CD in sub-micron Pb10 are 90% and 850.The addition of kaolinite can effectively control the emission of Pb ~ (2 +) CD in sub-micron, and the highest capture efficiency of Pb ~ (2 +) CD in sub-micron is 833% ~ (51)%, respectively. At high temperature, kaolin reacts with heavy metal Pb ~ (2 +) CD vapor and produces eutectic melting, which is produced by PbO Al2O3 _ 2SiO _ 2-CdO Al2O3 _ 2SiO _ 2. With the increase of temperature, the eutectic melting amount of kaolin and heavy metal increases, and its inclusion can promote the capture of heavy metal vapor by kaolin. However, excessive temperature will lead to excessive eutectic melting, resulting in the collapse of the pore structure of kaolin, and the reduction of the trapping efficiency. In the presence of Pb, Pb can promote the reaction between kaolin and CD. CD can inhibit the interaction between Pb and CD at 1000 鈩，

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