铈钛SCR催化剂脱硝脱汞一体化的研究

发布时间：2018-03-31 10:37

本文选题：铈钛催化剂　切入点：脱硝　出处：《华中科技大学》2015年硕士论文

【摘要】：能源与环境是目前人类发展所面临的最重大的两个问题。众所周知,煤是中国最主要的能源。煤炭的燃烧利用不仅向环境中排放了粉尘、SO2以及NOx等污染物,还会造成汞污染。汞是一种有毒重金属,对人体有极大的危害,因此燃煤烟气中汞的排放及控制近年来受到了极大的关注。随着燃煤电厂逐步配备脱硫及脱硝设备,利用常规污染物控制设备限制汞的排放成为了一种有前景的汞排放控制方法。大量研究表明SCR(Selective Catalytic Reduction)催化剂可以有效地捕获并促进汞的氧化。本文首先采用溶胶凝胶法制备了不同配比的铈钛催化剂(CeO2-TiO2),并通过X射线衍射仪(XRD),扫描电镜(SEM)等手段对其进行了表征;在固定床反应器上对催化剂的脱硝性能进行了测试,考察了温度、配比以及烟气组分的影响。在高效脱硝的前提下,又进行了单质汞脱除实验,考察了烟气组分的影响。实验结果表明,在200-500℃范围内,溶胶凝胶法制备的CeTi催化剂的脱硝性能要优于超声波浸渍法制备的CeTi(u)催化剂,且其效率随着温度的升高出现先升高后下降的趋势;在400℃温度下,质量配比为CeO2/Ti O2=0.5的铈钛催化剂取得了最高的脱硝效率(91.58%);在0-4%范围内,O2浓度的提高对脱硝效率有着明显的促进作用;氨氮比(NH3/NO)的升高会在一定程度上促进NO的转化;SO2和H2O均对铈钛催化剂的脱硝反应有着明显的抑制作用;脱汞实验中,CeO2含量的增加有助于脱汞效率的提高;而O2作为氧化剂会吸附在CeTi催化剂表面,进而与气相单质汞发生反应;HCl对脱汞效果的促进十分明显,但前提是有O2存在;由于NH3会与Hg0竞争消耗催化剂上的活性氧,SCR反应的存在会明显抑制脱汞反应;为提升CeTi催化剂的性能,向催化剂中添加了Cu,结果发现在低温区间脱硝性能和脱汞性能均有明显提升;但在高温区间脱硝性能会急剧下降,而H2O有助于缓解这一现象;与CeTi催化剂不同,SO2的存在会促进单质汞的脱除;最后,通过CeTi催化表面Hg0和O2的吸附实验确定了在400℃时,CeTi催化剂表面的单质汞催化氧化反应遵循Eley-Rideal机制,并建立了反应动力学模型。
[Abstract]:Energy and environment are two of the most important current human development faced. As everyone knows, coal is the main energy Chinese. The combustion of coal dust emissions using not only to the environment, SO2, NOx and other pollutants, will cause pollution of mercury. Mercury is a toxic heavy metal, there is great harm to the human body, so the control of mercury in coal-fired flue gas emissions in recent years has attracted great attention. Gradually equipped with the coal-fired power plant desulfurization and denitrification equipment, the use of conventional pollutant control equipment to limit mercury emissions has become a promising method for mercury emission control. A large number of studies show that SCR (Selective Catalytic Reduction) can effectively capture the oxidation catalyst and to promote mercury. Firstly by sol-gel method of cerium titanium catalyst prepared by different ratio (CeO2-TiO2), and by X ray diffraction (XRD), scanning electron microscopy (SEM) and other means It was characterized in a fixed bed reactor; denitrification performance of catalyst was tested, the effects of temperature, ratio and the influence of flue gas components. In the premise of efficient denitrification, and the mercury removal experiments, the effects of flue gas components. The experimental results show that in the 200-500 the temperature range of CeTi, the catalyst prepared by sol gel denitration performance is better than ultrasonic impregnation of CeTi (U) catalyst, and the efficiency with the increase of temperature increased first and then decreased slowly; in 400 degrees temperature, mass ratio of cerium and titanium catalyst CeO2/ O2=0.5 Ti achieved denitration efficiency the highest (91.58%); in the range of 0-4%, the increase of the concentration of O2 has a significant role in promoting the efficiency of denitrification; ammonia nitrogen ratio (NH3/NO) increased conversion will promote NO to a certain extent; the SO2 and H2O of cerium titanium catalyst denitration reaction with Ming Significant inhibition; mercury removal experiment, the increase of the content of CeO2 is helpful to improve the efficiency of mercury removal; and O2 as oxidant can be adsorbed on the surface of CeTi catalyst, then react with gas phase mercury; HCl for mercury removal effect is very obvious, but the premise is the existence of O2 by NH3; can compete with Hg0 consumption of reactive oxygen species on the catalyst, SCR reaction can significantly inhibit the mercury removal reaction; to improve the performance of CeTi catalyst, adding Cu to the catalyst, the denitrification performance and mercury removal performance have improved significantly in the low temperature range; but in the high temperature region between the denitrification performance will drop drastically. H2O helps alleviate this phenomenon; unlike the CeTi catalyst, the presence of SO2 could promote the removal of elemental mercury; finally, through adsorption experiments catalyzed by CeTi and Hg0 on the surface of O2 was determined at 400 DEG C, the mercury oxidation reaction of CeTi on the surface of the catalyst based on Eley-R The ideal mechanism and the kinetic model of the reaction have been established.

【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X773;O643.36

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