【作者】 徐莉莉；

【导师】 杜谦； 高继慧；

【作者基本信息】 哈尔滨工业大学 ， 热能工程， 2009， 硕士

【摘要】 燃煤电站排出的NOx中约有90%为NO,由于钙基吸收剂在烟气净化技术中被普遍采用,所以基于钙基吸收剂的污染物协同脱除技术研究具有重要价值。而钙基吸收剂对NO难以吸收,为提高NOx脱除效率,需将NO首先氧化为NO2,再用钙基吸收剂吸收,这是实现钙基吸收剂同时脱硫脱硝的重要途径。本文旨在寻找有效催化剂,研究其制备条件和模拟烟气环境对催化活性的影响,为基于同时脱硫脱硝的NO催化氧化技术开发奠定基础。本文搭建了常压固定床实验台,考察了人造沸石分别负载四种过渡金属氧化物催化剂在不同温度条件下的催化活性。研究发现:烟气温度对过渡金属氧化物催化剂的催化活性有较大影响。250℃~350℃范围内,过渡金属氧化物催化剂对NO的催化活性顺序为MnO_x>CoOx>CuOx>FeOx,烟温低于200℃时,这四种催化剂催化活性均较低。选择MnO_x作为基础催化剂活性物质,分析了助催剂及添加剂对MnO_x/沸石催化剂催化活性的影响,发现Co3O4、CeO2、CuO作为助催剂的加入在一定程度上提高了Mn基催化剂的活性,Fe2O3的加入对催化剂的活性有抑制作用,在300℃条件下,Mn-Ce/沸石催化剂的NO转化率与Mn/沸石相比提高了12%。选择5种多孔介质作为催化剂载体,考察了载体对催化剂催化活性的影响。研究表明:MnO_x作为催化剂活性物质时,使用不同载体制作的催化剂有不同的催化活性。考虑到经济性和易得性,本文选择稻壳灰作为催化剂载体,并对MnO_x/RHA制备条件进行了优化研究,得出的最佳制备条件是:催化剂载体RHA烧制温度800℃、活性物质MnO_x含量25wt.%、催化剂焙烧温度350℃、催化剂焙烧时间10h。本文最后在模拟烟气的反应环境下,对经优选的MnO_x/RHA催化剂进行了性能评价研究。发现随着NO入口浓度的升高,NO转化率呈下降趋势,NO浓度高于某一值时,出现催化剂性能迅速下降的拐点;O2含量对NO转化率的影响呈现迅速上升而后趋于平缓的趋势;H2O含量在0%~20%间波动时,NO转化率变化不大,表明MnO_x/RHA具有良好的抗水性;随着SO2的加入,NO转化率明显下降,表明SO2的对催化剂活性有显著的负面影响,需在后续工作中进行深入研究。更多还原

【Abstract】 Over 90% of NOx in flue gas of coal-fired power plant is NO that is difficult to be absorbed by calcium-based absorbents. The simultaneous desulfurization and denitrification technology based on calcium-based absorbents has been significant as a research direction of combined removal, which has important value. To enhance the denitration efficiency by calcium-based absorbents and achieve the aim of simultaneous desulfurization and denitrification technology, NO must to be turned into NO2 first. The research contents of this paper is to find effective catalyst, study the best preparation condition of it and test the influence of the flue gas composition on catalytic oxidation of NO, to realize the simultaneous desulfurization and denitrification technology.Investigations of NO catalytic oxidation over supported metal oxides were conducted by fixed-bed. The influence of temperature on catalytic oxidation of NO was tested and the results show that the catalytic activity of Mn/Zeolite, Co/Zeolite, Cu/Zeolite, Fe/Zeolite is rather low when the temperature is lower than 250℃while the relative order of the catalytic activity are MnO_x>CoOx>CuOx>FeOx when the temperature is between 250℃and 350℃. Tests were conducted to analyze the influence of promoter and additive on catalytic oxidation of NO by MnO_x-based catalyst. The results show that the activity is higher by adding Co3O4, CeO2 and CuO, while the activity is lower by adding Fe2O3. The conversion on the surface of Mn-Ce/Zeolite is 12% higher than Mn/Zeolite when the temperature is 300℃.Tests were conducted to research the influence of carrier on catalytic activity. The results show that it has great influence on activity of catalytic. The activity and stability of MnO_x/RHA is preferably, and the RHA is so cheap, thus RHA is better choice of new type catalysts’ carrier. The influence of catalyst’s preparation conditions was studied. The results show that the best preparation conditions are: calcining temperature is 350℃, length of calcining time is between 6~10h, ashing temperature is 800℃, loading of MnO_x is 25wt.%Based the above study, tests were conducted to research the influence of the flue gas composition on catalytic oxidation of NO. The results show that NO conversion keeps enhancing with O2 content increasing and when NO concentration increasing, NO conversion will reduce. SO2 in gas will lead to catalyst poisoning of MnO_x/RHA and reducing of NO conversion. Water resistance of MnO_x/RHA is good. Fluctuation of NO conversion is little when steam content is between 0%~20%.更多还原