新型复合改性活性炭脱除燃煤烟气中Hg~0的实验研究

发布时间：2018-06-19 06:27

  本文选题：模拟烟气 + 单质汞　； 参考：《湖南大学》2014年硕士论文

【摘要】：汞是一种对人类健康和生态系统有剧毒的污染物。无论是发达国家还是发展中国家，都面临着严重的汞污染问题，其中煤燃烧是大气汞污染最主要的来源之一。我国是全球最大的汞排放国，而燃煤电厂是我国最重要的汞排放源，因此，开发行之有效的方法来降低燃煤电厂的汞排放量显得尤为迫切。当前，活性炭喷射技术(ACI)被认为是最有效的燃煤电厂汞排放控制技术。然而，活性炭作为汞吸附剂的应用受到以下两个方面的限制：一方面，ACI技术需要消耗大量的活性炭导致高成本；另一方面，活性炭吸附剂的应用存在潜在的二次污染问题。这样不仅浪费了资源还带来了新的环境问题，因此，开发高效的、无二次污染的吸附剂对于ACI技术来讲非常关键。本文制备了一系列的改性活性炭，对其汞脱除性能进行了评估，，并深入探讨了改性活性炭的汞脱除机理，以期获得高效稳定的汞吸附剂。 首先考察了多种原始活性炭对模拟烟气中气态汞的吸附性能，并详细考察了活性炭颗粒大小和反应温度等因素对活性炭吸附性能的影响。实验结果表明，木质活性炭对气态汞具有较好的脱除效果，反应温度越低越有利于反应的进行。适宜的活性炭颗粒大小(0.15d0.25mm)能达到最佳的除汞效果，过大或者过小的粒径都对反应不利。 然后对活性炭进行Na2S、CeCl3浸渍改性以及高温渗硫改性，复合改性活性炭是先通过Na2S或CeCl3溶液浸渍活性炭再通过高温渗硫制得。运用比表面积, X射线衍射，扫描电子显微镜和X射线光电子能谱对样品的物理化学性质进行表征。对Na2S改性活性炭中负载量的研究结果表明，Na2S/AC的最佳负载量为5%。此外，研究了高温渗硫过程中渗硫温度以及硫炭比对S改性活性炭脱汞性能的影响，结果显示600℃渗硫活性炭表现出了最佳的脱汞性能；硫炭比从2:1降至1:2时，渗硫活性炭的硫含量以及脱汞性能只微弱下降。复合硫化改性活性炭Na2S-S/AC的汞饱和吸附量最大，为3282μg-Hg/g-C，约是单质硫改性活性炭的1.5倍。实验考察了不同烟气组分对Na2S-S/AC的影响，结果显示，当氧气含量提高至9%时，使Na2S-S/AC的脱汞效率提高了25%，NO和SO2对脱汞效率无显著影响，而H2O(8%)的存在，导致Na2S-S/AC脱汞效率降低了24%。将复合改性活性炭CeCl3-S/AC与CeCl3/AC对Hg0以及总汞的脱除性能做对比，结果表明CeCl3-S/AC对Hg0以及Hg2+的吸附性能均好于CeCl3/AC。
[Abstract]:Mercury is a highly toxic pollutant to human health and ecosystem. Both developed and developing countries are faced with serious mercury pollution, among which coal combustion is one of the most important sources of atmospheric mercury pollution. China is the largest emitter of mercury in the world, and coal-fired power plant is the most important source of mercury emission in China. Therefore, it is urgent to develop effective methods to reduce mercury emissions from coal-fired power plants. At present, activated carbon injection technology (ACI) is considered to be the most effective mercury emission control technology in coal-fired power plants. However, the application of activated carbon as a mercury adsorbent is limited by the following two aspects: on the one hand, ACI technology needs to consume a large amount of activated carbon, which leads to high cost; on the other hand, the application of activated carbon adsorbent has potential secondary pollution problem. This not only wastes resources, but also brings new environmental problems. Therefore, the development of efficient, non-secondary pollution-free adsorbent is very important for ACI technology. In this paper, a series of modified activated carbon were prepared, their mercury removal properties were evaluated, and the mercury removal mechanism of modified activated carbon was discussed in order to obtain high efficient and stable mercury adsorbent. The adsorption properties of gaseous mercury in simulated flue gas by various kinds of raw activated carbon were investigated, and the effects of particle size and reaction temperature on the adsorption properties of activated carbon were investigated in detail. The experimental results show that wood activated carbon has a better removal effect on gaseous mercury, and the lower the reaction temperature is, the more favorable the reaction is. The optimum particle size of activated carbon is 0.15d0.25mm), and too large or too small particle size is unfavorable to the reaction. Then the activated carbon was modified by Na2S- CeCl3 impregnation and high temperature sulphurizing. The composite modified activated carbon was prepared by impregnating activated carbon with Na2S or CeCl3 solution and then by sulfurizing at high temperature. The physical and chemical properties of the samples were characterized by specific surface area, X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. The results of study on the loading amount of Na2S modified activated carbon show that the optimum loading amount of Na2S / AC is 5%. In addition, the effects of sulfurizing temperature and the ratio of sulfur to carbon on the removal of mercury from S modified activated carbon during high temperature sulphurizing were studied. The results showed that the desulfurized activated carbon at 600 鈩

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