燃煤电厂烟气汞及典型重金属排放和脱除机理研究

Due to the strong neurotoxicity of mercury and other heavy metals (e.g. Cd, Cr, Pb, Se, As etc.), their emission from coal combustion may do great harm to the health of human and eco-system. Based on the characteristics of formation and emission of various species of mercury and other heavy metals, this research will be conducted in various aspects including: the mechanism of oxidation enhancement and adsorption of mercury by adding oxidant/adsorbent in the flue gas; the oxidation mechanism of mercury across commercial SCR catalysts; the principles of preparation of modified SCR catalysts which can simultaneously oxidize mercury and reduce NO; the synergy mechanism of mercury oxidation and NO reduction across modified SCR catalysts in complex flue gas; the mechanism of formation and emission control of toxic heavy metals via adding adsorbents in the furnace chamber. The objectives of this project are to clarify the in-depth mechanism of adsorption and oxidation enhancement of mercury by adding oxidant/adsorbent in the flue gas, to develop novel cost-effective SCR catalyst with good performance of mercury oxidation and NO reduction, to establish theory of the heterogeneous mercury oxidation on the reactive sites on the surface of the SCR catalysts, and to achieve the dual targets of mercury oxidation and NOx reduction. A detailed adsorption model of multiple volatile elements on adsorbent in furnace will be developed by quantitative analysis of species and concentrations of toxic heavy metals in the ultra fine particulates. And finally, a theoretical basis for effective removal of mercury and heavy metals in coal-fired flue gas will be established.

汞及典型有毒重金属具有极强的神经毒性，燃煤汞及重金属的排放对人类健康造成了极大危害，对生态系统产生了重大影响。本项目基于燃煤烟气汞及重金属的生成与排放特点，通过开展添加氧化剂/吸附剂对烟气中汞吸附、强化氧化的影响和脱除机理；商用SCR催化剂对烟气中汞氧化的机理；改性SCR催化剂制备及同时氧化烟气中的汞、还原NO的机制；复杂烟气条件下改性SCR催化剂协同增强Hg氧化和NO还原的机理；炉内添加吸附剂对有毒重金属和超细颗粒物生成与控制机理等方面的深层次基础研究，揭示氧化剂/吸附剂对烟气中汞吸附、强化氧化的影响和脱除机理，开发高效、价廉的改性商用SCR催化剂，构建比较完整的汞在SCR催化剂活性组分表面多相氧化的理论，实现汞氧化的同时还原NOx的双重目标，通过定量分析超细颗粒物中有毒重金属的种类及含量，构建炉内吸附剂对多气化元素的综合吸附模型，为燃煤烟气汞及重金属高效脱除奠定理论基础。

煤燃烧是汞及典型有毒重金属的主要排放源之一，这些典型的重金属具有极强的神经毒性，对人类健康造成了极大危害，对生态系统产生了重大影响。本项目基于燃煤烟气汞及重金属的生成与排放特点，重点做了以下研究工作：.通过低温等离子技术对碳基吸附剂进行修饰改性，在活性炭表面修饰特定的含氧官能团以及含氯官能团等，提高碳基吸附剂的活性、稳定性，从而降低活性炭吸附剂使用的成本；通过淀粉和卤素对矿物质吸附剂进行改性，提升了传统卤素改性矿物吸附剂的活性与稳定性，增强了单质汞的吸附与氧化；同样制备了溴化生物质灰等，得到高效经济的强化氧化吸附剂，并对其浸出特性进行了研究。.对商用SCR催化剂（V2O5基）协同脱汞过程进行了研究，重点研究了MoO3作为助剂的SCR催化剂的脱汞活性以及Mo在其中所起到的作用；另外，利用新方法对失活的SCR催化剂进行再生，并探究了再生催化剂的脱汞机理。.针对现有的钒基商业SCR催化剂的弊端提出了发展低温SCR催化剂的思路，制备了不同的含锰低温SCR催化剂，包括锰基钙钛矿型催化剂、锰掺杂铈锆固溶体催化剂、碳纳米管负载的锰钼催化剂等，探究了其活性与机理。另外针对性的设计了钒-铁-银-沸石催化吸附剂，该吸附剂在低温下性能较好，且可以实现NO和Hg0的协同脱除，并可以回收。.燃煤烟气组分是影响催化剂协同增强Hg氧化和NO还原的重要影响因素，重点研究了酸性气体如HCl、SO2、NO等的作用，并探究了其影响机理。除此之外研究了水蒸气、以及脱硝还原剂NH3的影响机理。.最后通过研究了富氧燃烧条件下，对有毒重金属和超细颗粒物生成与控制的机理，重点研究了SO2和水蒸气对As、Pb、Cr以及Cd的迁移转化、控制机理以及超细颗粒物的生成与控制的影响。