粉煤灰脱除燃煤烟气中单质汞的研究
文献类型：学位论文
| 作者 | 匡俊艳 |
| 学位类别 | 硕士 |
| 答辩日期 | 2011-05-20 |
| 授予单位 | 中国科学院研究生院 |
| 导师 | 朱廷钰 |
| 关键词 | 粉煤灰 改性 吸附 氧化 汞 |
| 其他题名 | Element Mercury Removal from Coal-fired Flue Gas by Fly Ash |
| 学位专业 | 环境工程 |
| 中文摘要 | 汞具有持久性、易迁移性和高度生物富集性等特点，是一种全球性污染物，其污染控制技术已成为全球关注的热点，而煤的燃烧是其最主要的人为排放源之一，因此燃煤汞排放控制刻不容缓。其中单质汞具有较高的挥发性与较低的水溶性，是最难控制的汞形态。活性炭吸附剂具有很好的汞吸附性能，但活性炭喷入技术运行费用昂贵，成为其推广应用的瓶颈。寻找高效廉价的单质汞吸附剂对汞排放控制十分必要。本论文基于粉煤灰吸附剂的研究进展和燃煤烟气中汞排放的特点，选取三种不同来源的粉煤灰，在自行搭建的固定床实验台上考察其汞吸附性能，采用X射线荧光光谱仪、X射线光电子能谱仪等手段对粉煤灰进行表征，探讨了物化性质对汞吸附性能的影响。在此基础上，采用Cl、Fe、Cu盐对粉煤灰进行改性，考察改性粉煤灰的汞吸附性能，及O2、SO2共存气体对吸附性能的影响，获得如下成果：（1）筛选了用于燃煤烟气中单质汞脱除的粉煤灰吸附剂，阐明了粉煤灰脱汞性能的影响因素。粉煤灰原灰对汞的吸附包括物理吸附和化学吸附过程；粉煤灰中未燃尽碳是影响粉煤灰汞吸附性能的重要因素之一，其中粉煤灰表面C元素与Ti、Si等元素(M)相互作用形成的“C-M”化学键能够促进单质汞的氧化，同时粉煤灰中含有的无机化合物Fe2O3等对吸附性能有一定的影响；另外，增大粉煤灰样品的比表面积和减小样品孔径，及选择适中的颗粒粒径均有利于提高样品的汞吸附性能；（2）分析了反应气氛对汞吸附性能的影响。模拟烟气中O2能够促进原灰对汞的吸附，而SO2在反应初期与Hg0形成竞争吸附不利于汞的脱除，但到反应后期，SO2能促进汞氧化反应的进行从而有助于汞的吸附。（3）开发了系列改性粉煤灰吸附剂，提高其汞吸附性能。FeCl3、CuCl2、CuBr2改性粉煤灰均有较好的汞吸附性能，主要是因为它们能够与Hg0发生化学反应从而增强了化学吸附，模拟烟气中O2的存在能够促进改性粉煤灰的汞吸附性能，而SO2具有竞争吸附和促进化学吸附的双重作用。本论文的研究工作为粉煤灰改性利用提供了实验依据，为低成本燃煤烟气汞吸附剂的开发提供了技术储备。 |
| 英文摘要 | Mercury pollution has been received considerable attentions from environmental researchers due to its high volatility, long persistence, and strong bioaccumulation properties. Since coal-fired boilers represent a significant fraction of the anthropogenic emissions of mercury into the atmosphere, the speciation and control of mercury in coal-fired boiler flue gas is currently an active topic of research. Research on the control of Hg0 emission should be put in the first position because of its high volatilization and low soluble. Activated carbon as a representative adsorbent has been frequently applied to an injection chamber, but cannot give a promising result due to its high price. Developing high-efficiency and low-cost sorbents is necessary for control of mercury. In this work, fly ash collected from three different factories and the samples modified by salts were tested for mercury adsorption using a fixed-bed with simulated gas.The effect of physicochemical properties on the mercury adsorption performance of three fly ash samples has been investigated. X-ray fluorescence spectroscopy, X-ray photoelectron spectroscopy, laser particle size analyzer, scanning electron microscopy and other methods were used to characterize the samples. Furthermore, fly ash is modified by different salts to improve their adsorption capacity, and the effect of O2 and SO2 on the adsorption performance is investigated. The following results are obtained: (1) The capture and oxidation of Hg0 by the samples under simulated gas conditions were investigated and the impact factors on adsorption efficiency were clarified. The results indicate that mercury adsorption on fly ash via both physisorption and chemisorption. Uncompleted burned carbon is an important factor for the improvement of mercury removal efficiency, especially, the C-M bond may improve the catalytic oxidation of mercury, which formed via the reaction of C and Ti、Si and other elements. Meanwhile inorganic compound such as Fe2O3 in the fly ash influences the mercury removal efficiency. The higher specific surface areas, smaller pore diameter, and moderate particle diameter are all beneficial for the high mercury removal efficiency. (2) The influence of O2 and SO2 in the flue gas on adsorption properties of mercury was investigated. It has been shown that the presence of O2 plays a positive role on Hg adsorption and oxidation over carbon in fly ash. On the contrary, SO2 inhibited mercury capture at the beginning, but a later stage. (3) Series of modified fly ash are developed and adsorption characteristics for mercury have been investigated. The results indicate that significant improvement of removal efficiencies with FeCl3、CuCl2 and CuBr2 impregnation onto fly ash. Therefore, the chemical reactions may further enhance their mercury capture performance. In addition, the presence of O2 plays a positive role on Hg adsorption of modified fly ash, while SO2 has double role of inhibition because of competitive adsorption and promotion to chemisorption. The basic data in this study are significant for further utilization of fly ash, as well as the technique support for the removal of Hg from coal fired flue gas. |
| 语种 | 中文 |
| 公开日期 | 2013-09-24 |
| 页码 | 69 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1742]  |
| 专题 | 过程工程研究所_研究所（批量导入） |
| 推荐引用方式 GB/T 7714 | 匡俊艳. 粉煤灰脱除燃煤烟气中单质汞的研究[D]. 中国科学院研究生院. 2011. |
入库方式： OAI收割
来源：过程工程研究所
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