State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, 430074, Wuhan, Hubei, China.
Environ Sci Pollut Res Int. 2016 Jan;23(1):253-65. doi: 10.1007/s11356-015-5644-7. Epub 2015 Nov 4.
Laboratory experiments were conducted to investigate the volatilization behavior of heavy metals during pyrolysis and combustion of municipal solid waste (MSW) components at different heating rates and temperatures. The waste fractions comprised waste paper (Paper), disposable chopstick (DC), garbage bag (GB), PVC plastic (PVC), and waste tire (Tire). Generally, the release trend of heavy metals from all MSW fractions in rapid-heating combustion was superior to that in low-heating combustion. Due to the different characteristics of MSW fractions, the behavior of heavy metals varied. Cd exhibited higher volatility than the rest of heavy metals. For Paper, DC, and PVC, the vaporization of Cd can reach as high as 75% at 500 °C in the rapid-heating combustion due to violent combustion, whereas a gradual increase was observed for Tire and GB. Zn and Pb showed a moderate volatilization in rapid-heating combustion, but their volatilities were depressed in slow-heating combustion. During thermal treatment, the additives such as kaolin and calcium can react or adsorb Pb and Zn forming stable metal compounds, thus decreasing their volatilities. The formation of stable compounds can be strengthened in slow-heating combustion. The volatility of Cu was comparatively low in both high and slow-heating combustion partially due to the existence of Al, Si, or Fe in residuals. Generally, in the reducing atmosphere, the volatility of Cd, Pb, and Zn was accelerated for Paper, DC, GB, and Tire due to the formation of elemental metal vapor. TG analysis also showed the reduction of metal oxides by chars forming elemental metal vapor. Cu2S was the dominant Cu species in reducing atmosphere below 900 °C, which was responsible for the low volatility of Cu. The addition of PVC in wastes may enhance the release of heavy metals, while GB and Tire may play an opposite effect. In controlling heavy metal emission, aluminosilicate- and calcium-based sorbents can be co-treated with fuels. Moreover, pyrolysis can be a better choice for treatment of solid waster in terms of controlling heavy metals. PVC and Tire should be separated and treated individually due to high possibility of heavy metal emission. This information may then serve as a guideline for the design of the subsequent gas cleaning plant, necessary to reduce the final emissions to the atmosphere to an acceptable level.
进行了实验室实验，以研究在不同加热速率和温度下，城市固体废物（MSW）成分在热解和燃烧过程中重金属的挥发行为。废物成分包括废纸（Paper）、一次性筷子（DC）、垃圾袋（GB）、聚氯乙烯塑料（PVC）和废轮胎（Tire）。一般来说，在快速加热燃烧中，所有 MSW 成分中重金属的释放趋势都优于在低加热燃烧中。由于 MSW 成分的不同特性，重金属的行为也有所不同。Cd 的挥发性高于其他重金属。对于 Paper、DC 和 PVC，由于剧烈燃烧，在 500°C 的快速加热燃烧中，Cd 的蒸发率可高达 75%，而对于 Tire 和 GB，则观察到逐渐增加。Zn 和 Pb 在快速加热燃烧中表现出中等的挥发性，但在缓慢加热燃烧中其挥发性受到抑制。在热处理过程中，高岭土和钙等添加剂可以与 Pb 和 Zn 反应或吸附，形成稳定的金属化合物，从而降低其挥发性。在缓慢加热燃烧中，可以增强稳定化合物的形成。由于残留中存在 Al、Si 或 Fe，Cu 的挥发性在高低加热燃烧中都比较低。一般来说，在还原气氛中，由于形成元素金属蒸气，Paper、DC、GB 和 Tire 中的 Cd、Pb 和 Zn 的挥发性加速。TG 分析还表明，在形成元素金属蒸气的情况下，炭还原金属氧化物。在低于 900°C 的还原气氛中，Cu2S 是主要的 Cu 物种，这导致 Cu 的挥发性较低。废物中添加 PVC 可能会增加重金属的释放，而 GB 和 Tire 可能会产生相反的效果。在控制重金属排放方面，可以将含铝硅酸盐和钙的吸附剂与燃料一起进行共处理。此外，就控制重金属而言，热解可能是处理固体废物的更好选择。由于重金属排放的可能性较高，应将 PVC 和轮胎分开处理。这些信息可以作为设计后续气体净化装置的指南，以将最终排放到大气中的重金属减少到可接受的水平。
