Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084, PR China.
Waste Manag. 2012 Dec;32(12):2278-86. doi: 10.1016/j.wasman.2012.07.007. Epub 2012 Aug 11.
A thermodynamic calculation was carried out to predict the behavior and speciation of heavy metals (HMs), Pb, Zn, Cu, and Cd, during municipal solid waste (MSW) incineration with the different moisture levels. The calculation was based on the minimization of the total Gibbs free energy of the multi-components and multi-phases closed system reaching chemical equilibrium. The calculation also indicated the reaction directions and tendencies of HMs components. The impacts of chlorine additives (No PVC, 1%PVC, and 5%PVC) and moisture on the behavior of HMs were investigated at different temperature levels in the system (750 °C, 950 °C, and 1150 °C). Furthermore, because the incineration temperature falls down with the increase in moisture in waste, the co-influence of moisture and temperature in combusting MSW on the HMs was also studied with the given chlorine (as 1%PVC+0.5%NaCl). The results showed that in the non-chlorine system, the impact of the moisture on Pb, Zn, and Cu was not significant, and the ratio of compound transformation was less than 10%, except the Cd compounds at 950 °C and 1150 °C. In the system with low chlorine (as 1%PVC) at constant temperature, the chlorides of HMs (Cd, Pb, Zn, and Cu) transferred to oxides, and when the content of chlorine rose up (as 5%PVC), the ratio of the chlorides of HMs (Cd, Pb, Zn, and Cu) transferring to oxides fell down noticeably. When the moisture varied together with the temperature, the Zn and Cu compounds transferred from chlorides to oxides with increase in moisture as well as decrease in temperature. At the temperature of 700-1000 °C, the impact of temperature on Pb and Cd was little and the moisture was the main factor; while at the temperature of 1000-1200 °C, the impact of increase in moisture and decrease in temperature on Pb and Cd was almost equal and reversed.
进行了热力学计算，以预测在不同水分水平下城市固体废物（MSW）焚烧过程中重金属（HM）、Pb、Zn、Cu 和 Cd 的行为和形态。该计算基于多组分和多相封闭系统的总吉布斯自由能最小化，达到化学平衡。该计算还表明了 HM 成分的反应方向和趋势。在系统中不同温度水平（750°C、950°C 和 1150°C）下，研究了氯添加剂（无 PVC、1%PVC 和 5%PVC）和水分对 HM 行为的影响。此外，由于废物中水分的增加导致焚烧温度下降，因此还研究了给定氯（如 1%PVC+0.5%NaCl）下燃烧 MSW 中的水分和温度对 HM 的共同影响。结果表明，在非氯系统中，水分对 Pb、Zn 和 Cu 的影响不显著，化合物转化的比例小于 10%，除了 950°C 和 1150°C 下的 Cd 化合物。在恒定温度的低氯系统（如 1%PVC）中，HM 的氯化物（Cd、Pb、Zn 和 Cu）转化为氧化物，而当氯含量升高（如 5%PVC）时，HM 的氯化物（Cd、Pb、Zn 和 Cu）转化为氧化物的比例明显下降。当水分与温度一起变化时，随着水分的增加和温度的降低，Zn 和 Cu 化合物从氯化物转化为氧化物。在 700-1000°C 的温度下，温度对 Pb 和 Cd 的影响较小，水分是主要因素；而在 1000-1200°C 的温度下，水分增加和温度降低对 Pb 和 Cd 的影响几乎相等且相反。
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