垃圾焚烧中Cd、Pb、Zn挥发行为的研究

VOLATILIZATION OF Cd, Pb AND Zn DUMNG INCINERATION OFMUNICIPAL SOLID WASTE

焚烧处理是目前处置数量急剧增长的城市生活垃圾 (MSW)的一个重要手段之一。该文在流化床(FB)试验装置 上进行城市垃圾焚烧试验,采用电感耦合等离子体发射光谱(ICP—OES)在线测量烟气中的重金属浓度,研究镉、铅、锌3种重金属的挥发释放特性,考察不同因素对重金属挥发行为的影响。结果表明:重金属的挥发行为受到焚烧温度、气体组分以及烟气中的氯成分等因素的影响。在流化床垃圾焚烧过程中,具有较大表面积的床料砂能够促进稳定成分如CdO·SiO2、ZnO·Al2O3的生成,从而抑制重金属的挥发。和Cd、Pb相比,Zn的释放程度较低。随着烟气中氧浓度的提高,氯化反应受到阻碍,重金属的挥发释放受到抑制。

Incineration has been considered as a more effective approach to handle growing municipal solid waste (MSW) quantities. Incineration experiments with MSW, which had been impregnated with heavy metals, were presented in this paper to obtain information on the volatilization behavior of the elements cadmium (Cd), lead (Pb), and zinc (Zn) under different conditions. Experiments were carried out in a bubbling fluid bed system connected to a customized Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) for analyzing metals in the flue gas. The results indicated that the combustion temperature, the gas atmosphere, and the chlorine content in the flue gas could affect the volatilization behavior of heavy metals. In the fluidized bed combustion, a large surface area was provided by the bed sand particles, and they would act as absorbents for the gaseous ash-forming compound. Comparer with the metals Cd and Pb, the vaporization of Zn was low. The formation of stable compounds such as CdO·SiO2 and ZnO·Al2O3 could greatly decrease the metals volatilization. The presence of chlorine would enhance the volatilization of heavy metals by increasing the formation of metal chlorides. However, when the oxygen content was high, the chlorinating reaction was kinetically hindered, which heavy metals release would be delayed.