脱除燃煤烟气中单质汞的铁基氧化物设计

发布时间：2018-07-08 20:08

  本文选题：密度泛函理论 + α-Fe_2O_3　； 参考：《大连理工大学》2015年硕士论文

【摘要】：目前,煤燃烧释放的汞污染物是全球大气汞污染物的主要来源之一。为了清洁有效利用煤资源,各个国家和地区先后推出了一系列相应的法律法规对各类燃煤污染物进行了严格的限排。但基于我国的基本国情,尚未开发及设计出适合于我国燃煤电站现有污染物排放控制设备的燃煤烟气中汞的脱除技术及吸附剂。本文从计算和实验两方面出发进行铁基氧化物的设计和研究,旨在设计出高效廉价的可应用于脱除燃煤烟气中单质汞的铁锰氧化物类吸附剂。本文首先对氧化铁在汞脱除方面的应用进行理论计算和设计。利用量子化学密度泛函理论计算了不同形态汞在a-Fe2O3(001)表面上的吸附情况。计算结果显示,单质汞在a-Fe2O3(001)表面的吸附较弱,为物理吸附,Hg0垂直吸附在与Fetop成键的Otop位时,吸附能最大；而HgO在其表面的吸附却是化学吸附,垂直于吸附剂表面吸附在Fetop位上能够得到两种稳定平衡结构,即Hg先吸附在Fe原子上和O先吸附在Fe原子上的两种吸附模型。基于理论计算结果分析,设计制备了铁锰氧化物吸附剂,并将其用于燃煤烟气中的汞的脱除实验。为制备出高效脱汞吸附剂,探讨了制备条件的影响。结果表明：铁锰摩尔比为1：1,焙烧温度为400℃条件下制备的样品具有高稳定性和高效脱除单质汞的性能。进一步考察了反应温度和模拟烟气组分对单质汞的脱除影响,发现100,200,300,400℃条件下反应的脱汞性能相差不大,单质汞脱除效率都能达到98%以上,但相对而言低温条件更有利于单质汞的脱除；烟气组分中O2和C02都能够促进单质汞的脱除,且02浓度的变化不能改变氧化物的脱除汞能力,推断脱汞反应机理是晶格氧机理。另外,当吸附剂混合石英砂时,可大大提高氧化物利用率。考察吸附剂的再生性时发现,吸附产物经高温脱附,再次应用于模拟烟气中单质汞脱除试验,虽然较新鲜样品脱汞能力有所下降,单质汞脱除率仍能达到94%的。
[Abstract]:At present, mercury released from coal combustion is one of the main sources of atmospheric mercury pollutants in the world. In order to make clean and effective use of coal resources, various countries and regions have introduced a series of corresponding laws and regulations to strictly limit the emission of all kinds of coal pollutants. However, based on the basic conditions of our country, the removal technology and adsorbent of mercury from coal-fired flue gas suitable for the existing pollutant emission control equipment of coal-fired power stations in China have not been developed and designed. In this paper, the iron based oxides were designed and studied from two aspects of calculation and experiment. The purpose of this paper is to design an efficient and cheap iron manganese oxide adsorbent which can be used to remove elemental mercury from coal-fired flue gas. In this paper, the application of ferric oxide in mercury removal is theoretically calculated and designed. The adsorption of different forms of mercury on a-Fe _ 2O _ 3 (001) surface has been calculated by using the density functional theory of quantum chemistry. The results show that the adsorption of elemental mercury on the surface of a-Fe _ 2O _ 3 (001) is weak, and the adsorption energy of Hg _ 0 is the largest when it is perpendicular to the site of Otop bonded with feed, while the adsorption of HgO on the surface is chemisorption. Two stable equilibrium structures can be obtained when adsorbed perpendicular to the surface of the adsorbent at the Fetop site, that is, two adsorption models of Hg adsorbing on Fe atom and O adsorbing on Fe atom first. Based on the analysis of theoretical calculation results, the iron and manganese oxide adsorbents were designed and prepared and used in the removal of mercury from coal-fired flue gas. In order to prepare high-efficiency mercury removal adsorbent, the influence of preparation conditions was discussed. The results show that the samples prepared under the conditions of iron-manganese molar ratio of 1: 1 and calcination temperature of 400 鈩，

本文编号：2108606