可磁分离非均相光助类Fenton 与吸附协同一体化燃煤烟气脱硫、脱硝、脱汞的基础研究

At present, most of current mature purification technologies of coal-fired flue gas are usually the simple series of multiple independent systems, which have some disadvantages, such as large area occupied, complicated technology, higher capital and operation cost. This situation will seriously affect the implementation of newly promulgated Emission Standard of Air Pollutants for Thermal Power Plants and the accomplishment of atmospheric environmental administration's goal determined in Twelfth Five-Year Plan. Therefore, simultaneous removal of SO2, NOx, and Hg from coal-fired flue gas has become one of the most challenging research topics in the field of energy and environment. The fundamental theory on simultaneous removal of SO2, NOx, and Hg from flue gas by combination of heterogeneous photo-Fenton-like reaction with magnetically separable ferrite/activated carbon catalyst and adsorption will be studied thoughtfully in this project. The effects of active element ratio and preparation method on removal of SO2, NOx, and Hg under heterogeneous photo-Fenton-like reaction with cooperative adsorption will be discussed.Moreover, the removal mechanism and relation between competition and cooperation in the simultaneous removal process of SO2, NO, and Hg will be also researched. The roles of adsorption reaction, free radical oxidation reaction, and catalytic reaction in the removal process of SO2, NO, and Hg will be discussed, and the main reaction of this process will be also explored. Meanwhile, the performance of catalyst's magnetic separation and recycling will be investigated. The reaction kinetic of heterogeneous photo-Fenton-like reaction for removal of SO2, NOx, and Hg will be established and analyzed. Through the above research, scientific basis for new purification technology of multiple contaminants from coal-fired flue gas can be provided.

目前国内外较成熟的烟气净化技术往往是多个独立系统的简单串联，存在着占地面积大、工艺复杂、投资和运行成本高等缺点，将严重影响新颁布《火电厂大气污染物排放标准》的实施和"十二五"大气环境治理目标的完成。燃煤烟气中SO2/NO/Hg 的联合脱除已成为能源与环境领域最具挑战性的研究课题之一。本项目拟深入开展可磁分离铁氧体/活性炭为催化剂光助类Fenton 与吸附协同一体化催化氧化烟气中SO2/NO/Hg 的基础研究。拟研究光助类Fenton 与吸附协同下磁性催化剂组分、制备方法对SO2/NO/Hg 一体化脱除率的影响；研究协同脱除过程中SO2/NO/Hg 的竞争/协同脱除机制；探究吸附反应、自由基反应和催化反应在一体化脱除中的作用和同时脱除的主要反应；研究催化剂的磁分离和循环再利用性能；建立非均相体系的反应动力学模型。研究将为燃煤烟气多种污染物一体化脱除新技术提供可借鉴的科学依据。

本项目采用化学共沉淀法制备了三种非均相类Fenton催化剂Fe3-xTixO4、Fe3-xCoxO4和Fe3-xCuxO4，利用X-射线衍射（XRD）、扫描电镜（SEM）和比表面积及孔径分析（BET）等测试手段对催化剂的物理化学性质进行了表征。在鼓泡床实验台架上进行模拟烟气中Hg0的脱除研究，重点考察了H2O2添加浓度、溶液pH、催化剂用量和反应温度对汞脱除效率的影响。研究发现随着Ti和Cu含量的增加，Hg0的脱除效率有所提高。在一定范围内随着H2O2浓度增加，Hg0的脱除效率增加较快，继续增加H2O2浓度，Hg0的脱除效率不再增加。催化剂在中性和偏弱酸溶液条件下的催化活性较高；催化剂最佳用量为0.6 g/L；最佳反应温度为50°C。SO2对Fe3-xTixO4的脱汞效率影响不大，对Fe3-xCoxO4和Fe3-xCuxO4有明显拟制作用；NO对三种催化剂的脱汞均有明显的促进作用。通过对催化剂的稳定性研究发现，Fe3-xTixO4和Fe3-xCuxO4催化剂稳定性能较差。两种催化剂在连续三次循环脱汞利用时，Hg0的脱除效率均有所下降。在Fe3-xTixO4和Fe3-xCuxO4研究的基础上同时向Fe3O4结构中引入Ti和Cu元素，研究其非均相类Fenton脱汞能力，同时试图改善催化剂的稳定性和可循环利用性。Ti、Cu同时掺杂增大了非均相类Fenton反应的pH窗口，提高了催化剂的抗酸能力。Cu0.3Fe2.7-xTixO4催化剂连续3 h反应的脱汞效率可稳定在96%以上，具有良好的稳定性，经磁分离后的催化剂不受影响，重复使用基本可以达到新鲜催化剂的脱汞效果。模拟烟气中SO2、NO和Hg0的联合脱除实验显示SO2的脱除效率接近100%，Hg0的脱除效率稳定在93%，NO的脱除效率在70%左右。电子顺磁共振（EPR）分析证实了催化剂反应过程中•OH自由基的产生。为揭示反应机理，本项目采用密度泛函理论研究了Fe3O4/H2O2体系中Hg0和H2O2同时在催化剂表面以及Hg0在H2O2预吸附表面的氧化反应特性，深入探讨了•OH自由基的生成规律和Hg0的氧化机理。