铁矿石烧结过程二恶英的低毒性定向诱导和阻滞钝化机制

Inhibition of dioxin formation is to fulfill the basic requirements of the Stockholm Convention and the national dioxin control policy. Two major pathways of dioxin formation in combustion process have been proposed: the de novo synthesis and the precursor pathway. The former one that is based on waste incineration process has been proved to be the more major pathway. However, current understanding of dioxin formation in iron ore sintering process is mostly adapted from waste incineration, but there are great differences in raw materials between the two processes. In addition, larger amount of components promoting dioxin formation in the fuel, and different temperatures and atmospheres in different sinter layers also affect the dioxin formation. Furthermore, dioxin heterogeneous catalysis formation pathway and the key elements of the coupling mechanism are still unknown. This research aims at investigating the coupling associated with effects of the metal and carbon, dioxin heterogeneous catalysis formation pathway and competitive mechanism of sulfide with dioxin, in order to explore how metal speciation transformation affect dioxins formation in the sintering process, what the low toxic induce pathway of dioxin is. Then propose dioxin inhibition mechanism and build a model of dioxin formation in sintering process, providing the theoretical basis for dioxin inhibition technologies during sintering process.

铁矿石烧结过程二恶英的生成抑制是我国控制二恶英排放增长、履行斯德哥尔摩公约的重要问题。目前，烧结过程的二恶英生成机理大多沿用废物焚烧系统的相关理论，但二者二恶英合成环境存在很大差异，包括来自烧结原料及燃料中影响二恶英合成的碳源、氯源、催化剂等要素和烧结料区不同层带的温度、气氛等条件使合成机理异于焚烧；烧结过程的二恶英合成异相催化反应机制、关键要素耦合诱导作用等问题依然不明。本课题拟研究铁矿石烧结过程二恶英de novo合成主要要素的影响及其对二恶英的诱导反应效应，探索烧结过程二恶英生成反应的金属及其化合物与碳源的耦合关联效应、二恶英异相催化生成路径、硫化物与二恶英生成的竞争机理等问题，旨在揭示烧结过程金属形态变化、碳结构变迁对二恶英生成的作用机制，提出二恶英的低毒性定向诱导途径以及阻滞钝化机理，构建基于烧结过程的二恶英生成模型，为铁矿石烧结过程二恶英的生成抑制及减排技术的选择提供理论依据。

二恶英类物质对人体健康和环境具有极大的危害，铁矿石烧结过程是二恶英的最主要来源。本项目主要研究了铁矿石烧结过程中的二恶英生成机理，分析了二恶英de novo合成中温度、碳源、金属催化剂、硫化物等关键要素及其耦合关联作用对二恶英指纹特征的诱导反应效应，探讨了铁、铜和其他微量元素及其协同诱导作用，揭示了硫化物对二恶英前驱体的阻滞钝化机制，构建了铁矿石烧结过程的二恶英生成模型。.得出的部分重要结论有：①二恶英前驱体最适的两个合成温度为350ºC和450ºC；②碳含量为5wt.%时CBzs和PCBs的生成量均达到最大值，而碳含量继续升高时，二恶英类物质生成量反而降低；③CuCl2对二恶英前驱体的生成量具有显著的催化作用；④硫脲等含硫化合物对二恶英前驱体表现出明显的抑制效果，抑制效率可达90%以上；⑤铁、铜对二恶英前驱体的生成具有协同作用，且当Cu：Fe=10:1时协同效应最大。.本项目实验结果对于探明铁矿石烧结过程中二恶英生成和阻滞机理，分析温度、碳源、金属催化剂、硫化物等关键要素对二恶英及二恶英前驱体的生成影响，揭示二恶英低毒性定向诱导途径具有重要的科学意义，为铁矿石烧结过程二恶英的生成抑制及减排技术的选择提供理论了依据。