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活性炭选择性催化NOx的研究_热能与动力工程.rar

资料分类:工业大学 高级会员(sana0722)提供原创论文资料更新时间:2016-06-09
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摘 要:大气污染是工业污染中最突出的问题。工业污染物中的S02,NOx(90%为NO),CO,CO2等对人类生存环境造成了极大程度的威胁,其中NOx不仅会形成酸雨、化学烟雾,还是温室气体中的一种,NOx的污染会导致人类多种疾病。如何能够经济、高效、节能、环保的去除NOx一直是全球相关科学家致力于的难题。

   目前,NH3选择性催化还原(SCR)工艺脱除烟气中NOx的技术以用于工业化生产,但是NH3易泄漏,与烟气中的SO3可形成硫酸铵, 从而引起空预器、除尘器后续设备的严重积垢, 甚至未反应的氨沾染飞灰,同时其设备投资大、操作难度高,从而限制它的工业应用。因此,寻求更高效、更经济的烟气脱硝技术成为必然。本文在借鉴前人脱硝方法的基础上,利用活性炭对烟气脱硝进行了相关研究,得到了一定结果。活性炭是一种具有高度发达的孔隙结构和巨大的比表面积的材料,因而具有很强的吸附性,加之活性炭表面含有多元含氧官能团,为作为催化剂高效脱硝提供了有利条件。本文的研究工作如下:

   论述研究控制NOx排放技术的意义;综述控制NOx排放技术的发展与现状;在模拟烟气气氛下,利用固定床反应器对煤质活性炭进行NOx脱除性能的实验考查。

   研究结果标明:

   1)活性炭作为催化剂,在还原剂NH3和O2共存下NO的转化率可达到50%左右,且催化效果相对稳定。

   2)200℃为活性炭催化效率的转折点,200℃之前NO转化率随温度升高逐渐降低,在35℃平均转化率能达到88.5%。

   H2O的存在会阻碍活性炭表面的催化反应的进行,但随温度的上升其负面影响会减小。

   SO2浓度不高于900ppm时活性炭为催化剂的SCR脱硝效率较大,浓度高于900ppm,SO2的存在将抑制NO的催化反应。

   对于煤质活性炭而言,在一定范围内,比表面积越大,其催化还原NO的效率越高。

   比较SEM图发现,表面积大并拥有发达的孔径结构(特别是大中孔)的活性炭催化效果较优。

   之后,在模拟烟气气氛下,利用固定床反应器对使用其他活性炭进行相同实验,对比实验结果。并利用比表面积和孔容测定(BET)、扫面电镜(SEM)等分析手段对活性炭进行评价。

关键词:烟气脱硝;活性炭;氮氧化物

 

Abstract:The high-speed development of economy brings about serious environment pollution, such as atmosphere pollution which is the most prominent one. Industrial gaseous emission such as S02, NOx(NO accouts for 90%),CO and CO2 threatened people's living conditions, among which NOx is not only the cause of acid rain and photochemical smog but also a main kind of green-house gas. To remove NOx economically with efficiency without hurting the environment becomes a tough task that world-wide scientist should committed to. In this paper, we focus the main research on the NOx removal. 

   Selective catalytic reduction of NOx with NH3 (SCR) technique has been widely put into use, but problems still remain because of the leakage of NH3 which will result in pipe jam. Besides, high cost of equipment and hard operation conditions also restrict its use. Therefore, finding a better method of removing NOx become inevitable. Based on the previous research, we do research on dinitrification by active coke and get some good result. Active coke is a kind of material who has highly developed porous structure and plenty of hydrogen and oxygen functional groups on its surface, which provides better conditions as the catalyst of NOx removal. The main tasks of the paper are as followed: 

   With AC as catalyst, the NO conversion rate could reach 50% in the coexistence of NH3 and O2, and the effect is relatively stable.

   200℃ is the turning point for the efficiency of AC as catalyst. The NO conversion rate decreases with the increasing temperature, which reached 88.5% at 35℃.

   The existence of H2O will hinder the efficiency of AC as catalyst, but the rising temperature reduces the negative effects.

   When the flue gas has SO2 in it, the dinitrification efficiency would be quite different. When the concentration of SO2 is no more than 900ppm, the conversion rate is pleasant. Otherwise, the negative effect becomes greater.

   For AC, within a certain range, the greater the specific surface area, the higher efficiency of catalytic reduction of NO.

   According to the SEM graph, the larger surface area and pore structure, the better performance of AC as catalyst.

   Discuss about the significance of scientific research about controlling NOx emissions technology; review the development and the status of NOx emissions control technology.

   Using fixed bed reactor for experimental test to evaluate the performance of AC removing NOx in simulated flue gas atmosphere. The result indicate:

   Afterwards, do the same experiment with another kind of AC as compared experiment.

   Evaluate AC by scanning electron microscopy surface and other methods.

Keywords: flue gas denitrification; actived carbon(AC); nitrogen oxides

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