燃煤电站飞灰吸附汞的动态特性研究
发布时间：2018-08-04 16:52
【摘要】：在我国的能源格局中,火力发电发挥着一个重要的作用,每年煤炭的燃烧向环境中排放了大量的有毒物质—汞。据统计燃煤电站汞排放占人为汞排放量的1/3,严重威胁到了人类的生存和生态环境的平衡,燃煤电站汞污染问题已经越来越受到人们的关注。根据国内外汞污染研究现状发现,燃煤电站飞灰对烟气中的汞具有一定的吸附特性,是一种潜在的脱汞吸附剂,具有非常好的市场应用前景。故本文选取A、B两种飞灰作为研究对象,研究不同燃煤电站飞灰的汞吸附特性,并对其进行化学改性,以期提高其飞灰脱汞能力,并且针对改性飞灰进行了一系列研究,探索改性飞灰与烟气中汞的反应机理。为了研究飞灰在流动状态下的汞吸附特性,本文自主开发了一套携带床脱汞实验平台,并对实验平台的各组成部件进行准确性研究,确保所得数据真实有效。在该实验平台上,研究了不同飞灰、不同试剂改性、不同浓度试剂改性、不同温度、不同停留时间、不同烟气成分等因素对飞灰吸附汞效果的影响,并且采取了飞灰脱汞效率和吸附速率两种评价方法,从最终效果和反应速率两个方面,较为全面的评价了飞灰的脱汞性能,以期可以探索出一条实用的燃煤电站脱汞技术。首先本文针对A、B两种燃煤电站的煤粉进行了工业分析,测量了两种飞灰中的汞含量和未燃尽碳含量。使用HBr和NH4Br两种化学试剂对A、B飞灰进行化学改性,并对改性前后的飞灰比表面积、孔容和孔径进行分析,研究了不同浓度试剂改性飞灰中溴含量和飞灰表面结构的变化规律,得到了不同样品的重要表征信息。研究发现,不同电站的飞灰,其飞灰捕捉汞的能力有很大的不同。相同情况下,A飞灰的汞捕捉能力要强于B飞灰。飞灰的未燃尽碳含量越高,比表面积越大,孔径越小,飞灰的汞捕捉能力越强。对飞灰原样进行HBr和NH4Br改性,可以大大提高其飞灰汞捕捉能力,并且HBr改性飞灰的脱汞能力要好于NH4Br改性飞灰。增加改性飞灰的进料量或者烟气中的初始汞浓度,可以增加改性飞灰与烟气中汞的接触几率,从而提高其飞灰脱汞能力。改性飞灰对汞的吸附,包括物理吸附和化学吸附,反应器温度的提高,可以促进改性飞灰的化学吸附,却在一定程度上削弱了改性飞灰的物理吸附。研究发现,改性飞灰的脱汞能力随烟气温度的提高而提高,并且温度对NH4Br改性飞灰的影响要高于HBr改性飞灰。停留时间对改性飞灰吸附汞效果的影响,受时间和流场的双重作用：随着停留时间的增加,改性飞灰与汞反应的时间增加,但是反应器的进气量在逐渐减小,改性飞灰与烟气的混合效果逐渐变差。实验结果显示,HBr改性飞灰脱汞效率随停留时间的增加而减小,而MH4、Br改性飞灰则呈先上升后下降的趋势。但是,随着停留时间的增加,两种改性飞灰的吸附速率却在一直增加。反应器内烟气的成分和含量也会对改性飞灰吸附汞效果造成影响。烟气中的NO、NO2、HCl和O2气体本身具有极强的氧化性,会与改性飞灰中溴发生协同作用,从而促进改性飞灰对汞的吸附。而S02气体对改性飞灰吸附汞的影响较为复杂,在较低含量时,SO2气体会抑制改性飞灰对汞的捕捉,而在较高含量时,SO2气体又会促进改性飞灰对汞的捕捉。对携带床脱汞实验平台不同位置收集到的飞灰进行分析后发现,烟气中的汞主要富集在极细颗粒表面,比表面积越大,飞灰所捕捉的汞越多。
[Abstract]:In the energy pattern of China, thermal power plays an important role. Every year, the combustion of coal discharged a large number of toxic substances - mercury. According to the statistics, the mercury emission from coal-fired power plants accounts for 1/3 of human mercury emissions, which seriously threatens the balance of human survival and ecological environment. The problem of mercury pollution in coal-fired power stations has become more and more serious. According to the research status of mercury pollution at home and abroad, it is found that the fly ash of coal-fired power station has a certain adsorption characteristic on the mercury in the flue gas. It is a potential demercuric adsorbent and has a very good market prospect. Therefore, this paper selects the two kinds of fly ash of A and B as the research image, and studies the mercury adsorption characteristics of different coal-fired power plant fly ash. In order to study the reaction mechanism of the modified fly ash and the mercury in the flue gas, in order to study the mercury adsorption characteristics of the fly ash in the flow state, a set of experimental platform for the removal of mercury in the carrying bed was developed, and the experimental platform was developed. On the experimental platform, the effects of different kinds of fly ash, different reagent modification, different concentration reagents, different temperature, different residence time and different smoke components on the effect of mercury adsorption on fly ash were studied on the experimental platform, and two kinds of fly ash dehg efficiency and adsorption rate were adopted. The method of evaluating the dehhg performance of fly ash from two aspects, such as the final effect and the reaction rate, in order to explore a practical mercury removal technology for coal-fired power plants. Firstly, the industrial analysis of the pulverized coal in the two kinds of coal-fired power plants of A, two kinds of coal-fired power plants was analyzed, and the mercury content and the unburned carbon content in the two kinds of fly ashes were measured. The use of HB Two chemical reagents of R and NH4Br were chemically modified for A, B fly ash, and the specific surface area of fly ash, Kong Rong and the pore size of the modified fly ash were analyzed. The change law of the bromine content and the surface structure of fly ash in the fly ash of different concentration reagents was studied, and the important characterization information of different samples was obtained. The ability of ash to capture mercury is very different. In the same case, the mercury capture ability of A fly ash is stronger than that of B fly ash. The higher the unburned carbon in the fly ash, the greater the surface area, the smaller the pore size, the stronger the mercury capture ability of the fly ash. The HBr and NH4Br modification of the fly ash can greatly improve the captures of the fly ash mercury, and the HBr modified fly ash. The ability of dehydration is better than that of NH4Br modified fly ash. Increasing the feed amount of modified fly ash or the initial mercury concentration in the flue gas can increase the contact probability of the modified fly ash with the mercury in the flue gas, and thus improve the mercury removal ability of the fly ash. The modified fly ash is adsorbed on mercury, including physical adsorption and chemical adsorption, and the increase of the reactor temperature can promote the modification. The chemical adsorption of sex fly ash weakens the physical adsorption of modified fly ash to a certain extent. It is found that the dehydration ability of modified fly ash increases with the increase of flue gas temperature, and the effect of temperature on NH4Br modified fly ash is higher than that of HBr modified fly ash. The effect of residence time on the adsorption of mercury on modified fly ash is affected by the time and flow field Reacting: with the increase of residence time, the reaction time of modified fly ash and mercury is increased, but the intake of the reactor decreases gradually and the mixing effect of modified fly ash and flue gas gradually decreases. The experimental results show that the dehydration efficiency of HBr modified fly ash decreases with the increase of residence time, while MH4, Br modified fly ash will rise first and then decrease. However, with the increase of the residence time, the adsorption rate of the two kinds of modified fly ashes has been increasing. The composition and content of the flue gas in the reactor will also affect the effect of the modified fly ash on the adsorption of mercury. The NO, NO2, HCl and O2 gases in the flue gas have very strong oxidation, which will be synergistic with the bromine in the modified fly ash, thus promoting the synergistic effect of the bromine in the modified fly ash. The effect of S02 gas on the adsorption of mercury on modified fly ash is more complex. At a lower content, SO2 gas will inhibit the capture of mercury in the modified fly ash, while at a higher content, SO2 gas will promote the capture of mercury in the modified fly ash. It was found that Mercury in flue gas was mainly concentrated on the surface of very fine particles. The larger the specific surface area, the more mercury was captured by fly ash.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X773
本文编号：2164501
[Abstract]:In the energy pattern of China, thermal power plays an important role. Every year, the combustion of coal discharged a large number of toxic substances - mercury. According to the statistics, the mercury emission from coal-fired power plants accounts for 1/3 of human mercury emissions, which seriously threatens the balance of human survival and ecological environment. The problem of mercury pollution in coal-fired power stations has become more and more serious. According to the research status of mercury pollution at home and abroad, it is found that the fly ash of coal-fired power station has a certain adsorption characteristic on the mercury in the flue gas. It is a potential demercuric adsorbent and has a very good market prospect. Therefore, this paper selects the two kinds of fly ash of A and B as the research image, and studies the mercury adsorption characteristics of different coal-fired power plant fly ash. In order to study the reaction mechanism of the modified fly ash and the mercury in the flue gas, in order to study the mercury adsorption characteristics of the fly ash in the flow state, a set of experimental platform for the removal of mercury in the carrying bed was developed, and the experimental platform was developed. On the experimental platform, the effects of different kinds of fly ash, different reagent modification, different concentration reagents, different temperature, different residence time and different smoke components on the effect of mercury adsorption on fly ash were studied on the experimental platform, and two kinds of fly ash dehg efficiency and adsorption rate were adopted. The method of evaluating the dehhg performance of fly ash from two aspects, such as the final effect and the reaction rate, in order to explore a practical mercury removal technology for coal-fired power plants. Firstly, the industrial analysis of the pulverized coal in the two kinds of coal-fired power plants of A, two kinds of coal-fired power plants was analyzed, and the mercury content and the unburned carbon content in the two kinds of fly ashes were measured. The use of HB Two chemical reagents of R and NH4Br were chemically modified for A, B fly ash, and the specific surface area of fly ash, Kong Rong and the pore size of the modified fly ash were analyzed. The change law of the bromine content and the surface structure of fly ash in the fly ash of different concentration reagents was studied, and the important characterization information of different samples was obtained. The ability of ash to capture mercury is very different. In the same case, the mercury capture ability of A fly ash is stronger than that of B fly ash. The higher the unburned carbon in the fly ash, the greater the surface area, the smaller the pore size, the stronger the mercury capture ability of the fly ash. The HBr and NH4Br modification of the fly ash can greatly improve the captures of the fly ash mercury, and the HBr modified fly ash. The ability of dehydration is better than that of NH4Br modified fly ash. Increasing the feed amount of modified fly ash or the initial mercury concentration in the flue gas can increase the contact probability of the modified fly ash with the mercury in the flue gas, and thus improve the mercury removal ability of the fly ash. The modified fly ash is adsorbed on mercury, including physical adsorption and chemical adsorption, and the increase of the reactor temperature can promote the modification. The chemical adsorption of sex fly ash weakens the physical adsorption of modified fly ash to a certain extent. It is found that the dehydration ability of modified fly ash increases with the increase of flue gas temperature, and the effect of temperature on NH4Br modified fly ash is higher than that of HBr modified fly ash. The effect of residence time on the adsorption of mercury on modified fly ash is affected by the time and flow field Reacting: with the increase of residence time, the reaction time of modified fly ash and mercury is increased, but the intake of the reactor decreases gradually and the mixing effect of modified fly ash and flue gas gradually decreases. The experimental results show that the dehydration efficiency of HBr modified fly ash decreases with the increase of residence time, while MH4, Br modified fly ash will rise first and then decrease. However, with the increase of the residence time, the adsorption rate of the two kinds of modified fly ashes has been increasing. The composition and content of the flue gas in the reactor will also affect the effect of the modified fly ash on the adsorption of mercury. The NO, NO2, HCl and O2 gases in the flue gas have very strong oxidation, which will be synergistic with the bromine in the modified fly ash, thus promoting the synergistic effect of the bromine in the modified fly ash. The effect of S02 gas on the adsorption of mercury on modified fly ash is more complex. At a lower content, SO2 gas will inhibit the capture of mercury in the modified fly ash, while at a higher content, SO2 gas will promote the capture of mercury in the modified fly ash. It was found that Mercury in flue gas was mainly concentrated on the surface of very fine particles. The larger the specific surface area, the more mercury was captured by fly ash.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X773
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