光/热耦合激发制取卤-羟基自由基同步烟气多污染物一体化脱除的过程调控与机理研究

Aimed at the important subject of simultaneous removal of SO2, NOx and Hg0 from flue gas, and based on our previous works of gas phase oxidation resulting from the thermal excitation for cooperative control multi-pollutants in flue gas, and in consideration of the significant promotional effect of the combination of halogen radical and hydroxyl radical (halogen-hydroxyl radicals) on the removal of Hg0 and NO, the study concerning the non-electrical generation of gas phase halogen-hydroxyl radicals has not been well documented however. This project is going to develop a generator of light/thermal coupling excitation to produce halogen-hydroxyl radicals, to screen and optimize the combination of the precursors of oxidants and additives and control the parameters of coupling excitation process, studying the generation mechanism of halogen-hydroxyl radicals and their behaviors on NO/Hg0 oxidations as well as simultaneous removal of SO2, NO and Hg0, to make clear the influence law of various reaction conditions on the simultaneous removal process, exploring the interaction mechanism of multi-components in flue gas. With a lot of analysis methods, to demonstrate the key reaction intermediates and the compositions of removal products, revealing the reaction mechanism of the simultaneous removal process. The aim of this project is to solve some key basic problems related to the method of gas phase oxidation for simultaneous removal of SO2, NO and Hg0 maybe encountered in the practical application, the expected research results are of great significance for the development of the technologies of simultaneous removal of SO2, NO and Hg0.

围绕烟气中SO2、NO和零价汞的一体化脱除这一重要课题，本项目基于前期热激发型气相氧化法烟气多污染物协同控制的研究基础，并考虑到卤自由基与羟基自由基的组合（卤-羟基自由基）在脱硝脱汞方面具有显著促进作用而关于非电激发模式制取高浓度气相卤-羟基自由基的研究尚未取得突破性进展这一现实难题：(1)拟研发一种新型光/热耦合激发型气相卤-羟基自由基发生器，优选复配氧化剂/添加剂前体物并调控耦合激发过程参数；(2)研究卤-羟基自由基的生成机理及其在氧化NO/零价汞和一体化脱硫脱硝脱汞过程中的反应行为，厘清多种反应条件对多污染物协同脱除过程的影响规律，探究烟气多组分间的交互作用机制；(3)借助多种分析测试手段，明确关键反应中间体和产物组成，揭示一体化脱除反应机理。本项目旨在解决束缚气相氧化一体化脱硫脱硝脱汞方法走向应用的若干关键基础难题，对烟气一体化脱硫脱硝脱汞技术的发展具有重要意义。

现有烟气分级处理工艺存在系统复杂、占地面积大、运行成本高等问题，发展烟气一体化脱硫脱硝脱汞新技术有望降低烟气治理成本和简化烟气治理工艺，为此本项目开发了基于高级氧化原理的烟气多污染物协同控制技术，构建了适用于烟气治理的光/热协同催化气相自由基发生体系，制取了具有强脱硝脱汞活性的卤自由基和羟基自由基复合物，明确了卤-羟基自由基的最佳制取条件，揭示了卤-羟基自由基的生成机理及其脱硫脱硝脱汞反应行为，厘清了各种工况条件对脱硫脱硝脱汞的影响规律，借助多种分析测试手段明确了关键反应中间体和解析了反应终产物物质构成，最终提出卤-羟基自由基一体化脱硫脱硝脱汞反应机理。重要结果和关键数据阐述如下：制得了具有高脱汞活性的卤-羟基自由基ClOH•-/BrOH•-和二卤自由基Cl2•-/Br2•-，这是首次利用一步合成法制取的次生卤自由基，跳过了Cl•/Br•生成步骤，利用HO•和卤-羟基自由基的组合，实现了脱硝脱汞效率83.7%/82.8%和99.2%/98.8%；利用UV辐照NaClO2制得了ClO•，还发现碱化NaClO2可提高ClO•产率并抑制ClO2生成，NH4OH的加入可以大幅抑制ClO2和NO2的产率，最佳脱硫脱硝效率达到98.7%和99.1%；阐明了热催化下S2O82-与ClO2-之间的协同机制，发现ClO2-在热催化和S2O82-酸活化下产生了HO•/ClO2， S2O82-则在热催化和ClO2-碱活化下产生了SO4•-/HO•，以此一步合成三种自由基；明晰了UV/NaClO2、UV/NaClO、UV/Na2S2O8、UV/KHSO5和UV/H2O2五种典型UV-AOP体系的脱硝脱汞反应活性及成本效益，发现UV/NaClO2的脱硝脱汞性能最好、成本效益最高，高出其他体系2-5个数量级。构建了若干高级氧化耦合湿法吸收的烟气脱硫脱硝脱汞工艺范式：包括光/热协同催化H2O2耦合氨法双循环吸收体系、热催化H2O2/Na2S2O8耦合钠法双循环吸收体系、ClO2氧化耦合亚硫酸铵吸收的三区控制体系，探明了反应边界条件，建立了最优参数体系，最佳脱硫脱硝脱汞效率分别达到99%以上、93%以上和92%以上。综上，申请人围绕高级氧化法烟气多污染物协同控制理论与技术研发进行了系统而深入的探索，研究成果为高级氧化法烟气多污染物协同控制技术应用奠定了一定理论基础。