發(fā)布時間：2018-08-04 16:52

【摘要】：在我國的能源格局中,火力發(fā)電發(fā)揮著一個重要的作用,每年煤炭的燃燒向環(huán)境中排放了大量的有毒物質(zhì)—汞。據(jù)統(tǒng)計燃煤電站汞排放占人為汞排放量的1/3,嚴重威脅到了人類的生存和生態(tài)環(huán)境的平衡,燃煤電站汞污染問題已經(jīng)越來越受到人們的關注。根據(jù)國內(nèi)外汞污染研究現(xiàn)狀發(fā)現(xiàn),燃煤電站飛灰對煙氣中的汞具有一定的吸附特性,是一種潛在的脫汞吸附劑,具有非常好的市場應用前景。故本文選取A、B兩種飛灰作為研究對象,研究不同燃煤電站飛灰的汞吸附特性,并對其進行化學改性,以期提高其飛灰脫汞能力,并且針對改性飛灰進行了一系列研究,探索改性飛灰與煙氣中汞的反應機理。為了研究飛灰在流動狀態(tài)下的汞吸附特性,本文自主開發(fā)了一套攜帶床脫汞實驗平臺,并對實驗平臺的各組成部件進行準確性研究,確保所得數(shù)據(jù)真實有效。在該實驗平臺上,研究了不同飛灰、不同試劑改性、不同濃度試劑改性、不同溫度、不同停留時間、不同煙氣成分等因素對飛灰吸附汞效果的影響,并且采取了飛灰脫汞效率和吸附速率兩種評價方法,從最終效果和反應速率兩個方面,較為全面的評價了飛灰的脫汞性能,以期可以探索出一條實用的燃煤電站脫汞技術。首先本文針對A、B兩種燃煤電站的煤粉進行了工業(yè)分析,測量了兩種飛灰中的汞含量和未燃盡碳含量。使用HBr和NH4Br兩種化學試劑對A、B飛灰進行化學改性,并對改性前后的飛灰比表面積、孔容和孔徑進行分析,研究了不同濃度試劑改性飛灰中溴含量和飛灰表面結構的變化規(guī)律,得到了不同樣品的重要表征信息。研究發(fā)現(xiàn),不同電站的飛灰,其飛灰捕捉汞的能力有很大的不同。相同情況下,A飛灰的汞捕捉能力要強于B飛灰。飛灰的未燃盡碳含量越高,比表面積越大,孔徑越小,飛灰的汞捕捉能力越強。對飛灰原樣進行HBr和NH4Br改性,可以大大提高其飛灰汞捕捉能力,并且HBr改性飛灰的脫汞能力要好于NH4Br改性飛灰。增加改性飛灰的進料量或者煙氣中的初始汞濃度,可以增加改性飛灰與煙氣中汞的接觸幾率,從而提高其飛灰脫汞能力。改性飛灰對汞的吸附,包括物理吸附和化學吸附,反應器溫度的提高,可以促進改性飛灰的化學吸附,卻在一定程度上削弱了改性飛灰的物理吸附。研究發(fā)現(xiàn),改性飛灰的脫汞能力隨煙氣溫度的提高而提高,并且溫度對NH4Br改性飛灰的影響要高于HBr改性飛灰。停留時間對改性飛灰吸附汞效果的影響,受時間和流場的雙重作用：隨著停留時間的增加,改性飛灰與汞反應的時間增加,但是反應器的進氣量在逐漸減小,改性飛灰與煙氣的混合效果逐漸變差。實驗結果顯示,HBr改性飛灰脫汞效率隨停留時間的增加而減小,而MH4、Br改性飛灰則呈先上升后下降的趨勢。但是,隨著停留時間的增加,兩種改性飛灰的吸附速率卻在一直增加。反應器內(nèi)煙氣的成分和含量也會對改性飛灰吸附汞效果造成影響。煙氣中的NO、NO2、HCl和O2氣體本身具有極強的氧化性,會與改性飛灰中溴發(fā)生協(xié)同作用,從而促進改性飛灰對汞的吸附。而S02氣體對改性飛灰吸附汞的影響較為復雜,在較低含量時,SO2氣體會抑制改性飛灰對汞的捕捉,而在較高含量時,SO2氣體又會促進改性飛灰對汞的捕捉。對攜帶床脫汞實驗平臺不同位置收集到的飛灰進行分析后發(fā)現(xiàn),煙氣中的汞主要富集在極細顆粒表面,比表面積越大,飛灰所捕捉的汞越多。
[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.
【學位授予單位】：華北電力大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：X773

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本文編號：2164501