Wang Xinye, Xie Hao, Du Rong, Liu Yuying, Lin Pingfang, Zhang Jubing, Bu Changsheng, Huang Yaji, Zhang Wen
Jiangsu Provincial Key Laboratory of Materials Cycling and Pollution Control, School of Energy and Mechanical Engineering, Nanjing Normal University Nanjing 210042 Jiangsu China
Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University Nanjing 210096 Jiangsu China
RSC Adv. 2018 Oct 8;8(60):34449-34458. doi: 10.1039/c8ra06255b. eCollection 2018 Oct 4.
Municipal solid-waste incineration leads to emission of lead (Pb) and cadmium (Cd), which vaporize in furnace and condense in flue. NaCl in waste has been proven to enhance volatilization of Pb and Cd at high temperatures chlorination of oxides to chlorides; however, this process was not well-understood so far due to its complexity. This study decoupled the indirect chlorination process and direct chlorination process so that these two processes were investigated separately. A horizontal tube furnace was used to heat the mixtures of NaCl and Si/Al matrix for indirect chlorination and the mixtures of NaCl, PbO/CdO and Si/Al matrix for direct chlorination. A set of dynamic sampling devices was designed and used to obtain dynamic data during temperature rising. The indirect chlorination process was initiated above 800 °C in O + HO atmosphere and O atmosphere and above 1000 °C in N atmosphere. AlO exhibited higher activity than SiO to react with NaCl, releasing HCl or Cl. In the Cl release reaction, NaCl was in the gas phase. The direct chlorination process was initiated at 650-700 °C when the Si/Al matrix contained SiO only and at around 800 °C when the Si/Al matrix contained AlO only or both SiO and AlO. SiO exhibited higher activity than AlO in direct chlorination. The pre-reaction between PbO/CdO and Si/Al matrices was considered as the necessary condition for direct chlorination. During chlorination in O + HO atmosphere, indirect chlorination and direct chlorination occurred simultaneously, and the latter dominated the volatilization of Pb and Cd.
城市固体废弃物焚烧会导致铅（Pb）和镉（Cd）排放，它们在炉内汽化并在烟道中冷凝。已证实废弃物中的氯化钠（NaCl）能在高温下增强铅和镉的挥发——氧化物氯化生成氯化物；然而，由于该过程的复杂性，目前对其了解尚不充分。本研究将间接氯化过程和直接氯化过程解耦，以便分别对这两个过程进行研究。使用卧式管式炉加热氯化钠与硅/铝基体的混合物进行间接氯化，加热氯化钠、氧化铅/氧化镉与硅/铝基体的混合物进行直接氯化。设计并使用了一套动态采样装置来获取升温过程中的动态数据。间接氯化过程在氧气 + 水蒸气气氛和氧气气氛中于800℃以上启动，在氮气气氛中于1000℃以上启动。氧化铝比二氧化硅表现出更高的与氯化钠反应的活性，释放出氯化氢或氯气。在氯释放反应中，氯化钠处于气相。当硅/铝基体仅含二氧化硅时，直接氯化过程在650 - 700℃启动；当硅/铝基体仅含氧化铝或同时含有二氧化硅和氧化铝时，直接氯化过程在约800℃启动。在直接氯化中，二氧化硅比氧化铝表现出更高的活性。氧化铅/氧化镉与硅/铝基体之间的预反应被认为是直接氯化的必要条件。在氧气 + 水蒸气气氛中氯化时，间接氯化和直接氯化同时发生，且后者主导了铅和镉的挥发。
