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活性炭脱除烟气多污染物反应机制研究
林玉婷
Subtype硕士
Thesis Advisor李玉然
2018-07
Degree Grantor中国科学院研究生院
Degree Name硕士
Degree Discipline环境工程
Keyword活性炭,脱硝,硫化氢,官能团,Scr反应
Abstract

当前,我国大气污染形式依然严峻,特别是京津冀及周边地区成为大气环境质量改善的重点和难点。活性炭烟气多污染物协同控制技术可同时脱除SO2、NOx、H2S等多种污染物,不消耗水、无二次污染,目前已应用于燃煤电厂和烧结机的烟气净化,但是其脱硝效率有待提高。焦化行业焦炉烟气低硫高氮、多污染物共存的排放特征,对活性炭的脱硝效率及多污染物脱除效果提出了更高要求。本文针对焦炉烟气中的NOx含量高的特征,研究了活性炭改性对提高脱硝效率的作用机制,探索了影响脱硝效率的活性炭理化性质参数,并进一步揭示了活性炭的脱硝反应机理。针对焦炉烟气中存在H2S的特点,研究了H2S的吸附脱除机理和氧化产物分布,阐明了其与活性炭官能团的作用机制。采用四种含氮添加剂改性活性炭,实验结果表明改性降低了活性炭的比表面积和总孔溶剂,明显提高了活性炭的脱硝效率,主要原因在于,活性炭的石墨微晶结构的无序度增加了吸附活性位点,同时吡啶、吡咯、季胺等含氮官能团有不同程度的提高。对于活性炭在脱硝反应前后的官能团进行表征,发现NO与NH3发生SCR反应后,酚羟基的含量降低而醌羰基含量增加,吡啶、吡咯和季胺官能团减少而吡啶-N-氧化物含量显著增加。根据暂态响应实验分析,在110℃时反应遵循Langmuir-Hinshelwood机理;在150℃时有两条路线:吸附态的NH3与吸附态的NO反应,即L-H机理,或者是气态的NO直接参与反应,即Eley-Rideal机理。吡啶、吡咯和季胺基团可以吸附气态的NO,而酚羟基可以作为NH3的吸附位点生成醌类物质和N2,进而完成SCR反应。研究活性炭在复杂气氛中对H2S的脱除效果,实验结果表明在单一氧化性气氛中,氧化作用的强弱顺序为SO2>O2>NO,当还原性气体NH3存在时,H2S的脱除效率有所降低。与无氧气氛相比,在有氧气氛中H2S的氧化更容易发生,脱除效率更高。在无氧气氛,H2S吸附在活性炭表面被含氧官能团氧化,在活性炭上形成固态硫的氧化物。在有氧气氛,H2S和气态的O2吸附在活性炭的表面活性位,发生氧化反应生成单质硫,单质硫进一步与气氛中的O2反应生成SO2,导致气态的SO2溢出。;At present, the situation of air pollution in China is still severe, especially in Beijing, Tianjin, Hebei and its surrounding areas, which has become the key and difficult point in improving the quality of the atmosphere. The co-control technology of activated carbon method can simultaneously remove many pollutants such as SO2, NOx, H2S, which is no water consumption, no secondary pollution. It has been used in the flue gas purification of coal-fired power plants and sintering machines. Although the co-control technology of multi pollutants on activated carbon has many advantages, there are also problems of low denitrification efficiency. In view of the emission characteristics of low sulfur, high nitrogen and multiple pollutants coexisting in coke oven flue gas, the activated carbon method put forward higher requirements for the efficiency of denitrification and the effect of adsorption and removal of multiple pollutants in the engineering application. Based on the characteristics of the flue gas in the coking industry, this paper explores the effect of modification on the denitrification efficiency of activated carbon, points out physical and chemical properties of activated carbon affecting the efficiency of denitrification, and further describes the SCR reaction mechanism of activated carbon. Meanwhile, in view of the characteristics of H2S in coke oven flue gas, the removal mechanism and oxidation products of H2S are studied, and the interaction mechanism between pollutants and functional groups of activated carbon is clarified. The modified activated carbon was modified with four kinds of nitrogen containing additives. The results showed that the specific surface area and total pore volume of activated carbon were reduced, and the denitrification efficiency of activated carbon was obviously improved. The main reason is that the disorder of graphite microcrystalline structure of activated carbon increases the adsorption site, while pyridine, pyrrole, quaternary amine and other nitrogen containing officials are increased. The functional groups of activated carbon were characterized before and after the denitrification reaction. It was found that the content of phenol hydroxyl was reduced and the content of quinone carbonyl increased, and pyridine, pyrrole and quaternary amine functional groups decreased and the pyridine -N- oxide content of pyridine increased significantly after NO and NH3 had SCR reaction on activated carbon. According to the transient response test, the reaction follows the Langmuir-Hinshelwood mechanism at 110℃, and there are two routes at 150℃: The adsorbed NH3 react with the adsorbed NO (Langmuir-Hinshelwood mechanism), or the NO of the gas state directly involved in the reaction (Eley-Rideal mechanism). Pyridine, pyrrole and quaternary amine groups can adsorb gaseous NO, while phenolic hydroxyl groups can be used as the adsorption sites of NH3 to produce quinones and N2, thus completing the SCR reaction.The characteristics of the pore structure and the type and number of functional groups of activated carbon after H2S adsorbed under different atmospheres have been investigated. It is found that in a single oxidizing gas atmosphere, oxidation is strongly related to SO2>O2>NO. When the reducing gas NH3 is present, the removal efficiency of H2S decreases significantly. Compared with anaerobic atmospheres, the oxidation of H2S is more prone to occur in aerobic atmospheres and the removal efficiency is higher. In an anoxic atmosphere, H2S adsorbed on the surface of activated carbon oxidized by oxygen-containing functional groups, and then formed solid sulfur and sulfur oxides on the activated carbon. In the oxygen atmosphere, the H2S and the gaseous O2 adsorbed the active sites on the surface of the activated carbon, and the oxidation reaction produces the elemental sulfur. The elemental sulfur further reacts with the O2 in the atmosphere to produce SO2, resulting in the SO2 spillover of the gaseous state. 

Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/26871
Collection中国科学院过程工程研究所
研究所(批量导入)
Recommended Citation
GB/T 7714
林玉婷. 活性炭脱除烟气多污染物反应机制研究[D]. 中国科学院研究生院,2018.
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