School of Energy and Power Engineering, Key Laboratory of Renewable Energy Electric-Technology of Hunan Province, Changsha University of Science and Technology, Changsha 410114, China.
School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
Waste Manag. 2024 Dec 1;189:1-10. doi: 10.1016/j.wasman.2024.08.002. Epub 2024 Aug 12.
The nitrogen transformation during sludge pyrolysis is affected by the dewater conditioner. However, the comparative analysis of the conditioner under identical pyrolysis conditions has been previously absent. In this study, Ca-, Fe- and Al-based conditioners were selected as the representatives. A comprehensive evaluation considering the cost of the conditioners and the product characteristics was conducted. Additionally, the in-situ fixation mechanism of the conditioner on nitrogen-containing gas was concurrently revealed. Among the six conditioners, CaO and AlCl were identified as the top performers, ranking first and second, respectively. Furthermore, Fe/Ca-based conditioners reduced NH and HCN release by 1.5 ∼ 5.53 % and 0 ∼ 1.55 %, respectively, by facilitating the conversion of amine-N to a more stable form in condensable fraction. Fe promoted volatile amine-N cyclization, while Ca encouraged its dehydrogenation. Both Fe/Ca-based conditioners increased 7.5 ∼ 14.8 % nitrogen retention in char, by inhibiting the decomposition of protein-N. Al-based conditioners had little effect on NH and HCN, but contributed to 2.3 ∼ 2.8 % production of stabilized nitrogen in char. The introduction of Cl in Fe/Ca/Al chloride conditioners would promote the decomposition of inorganic ammonium salts to produce NH at 30 ∼ 185 °C. And Cl also reacted with volatiles through electrophilic substitution reaction, leading to the formation of halogenated hydrocarbons in condensable fraction and the release of more NH, HCN, and HNCO at 30 ∼ 465 °C. The findings of this study provide a detailed comparative analysis of various conditioners under uniform conditions and reveal the in-situ fixation mechanism of nitrogen-containing gas. This will provide guidance for the sludge conditioning-dewatering-drying integrated treatment and disposal.
在污泥热解过程中，氮的转化受脱水调质剂的影响。然而，以前缺乏在相同热解条件下对调质剂进行比较分析的研究。在这项研究中，选择了 Ca、Fe 和 Al 基调质剂作为代表。综合考虑调质剂的成本和产品特性进行了全面评价。此外，还揭示了调质剂对含氮气体的原位固定机制。在这 6 种调质剂中，CaO 和 AlCl3 被确定为表现最好的调质剂，分别排名第一和第二。此外，Fe/Ca 基调质剂通过促进胺-N 转化为更稳定的形式，减少了 NH 和 HCN 的释放，分别减少了 1.5%∼5.53%和 0%∼1.55%。Fe 促进了挥发性胺-N 的环化，而 Ca 促进了其脱氢。Fe/Ca 基调质剂均通过抑制蛋白-N 的分解，增加了 7.5%∼14.8%的氮在焦中的保留。Al 基调质剂对 NH 和 HCN 几乎没有影响，但有助于在焦中形成 2.3%∼2.8%的稳定氮。Fe/Ca/Al 氯化物调质剂中 Cl 的引入会促进无机铵盐分解，在 30∼185°C 下产生 NH。Cl 还通过亲电取代反应与挥发物反应，导致可冷凝部分形成卤代烃，并在 30∼465°C 下释放更多的 NH、HCN 和 HNCO。这项研究的结果提供了在均匀条件下对各种调质剂的详细比较分析，并揭示了含氮气体的原位固定机制。这将为污泥调质-脱水-干燥集成处理和处置提供指导。
