【摘要】：燃煤電站是人為汞污染排放的主要來源,對人類的健康、生態(tài)環(huán)境等都造成了很大危害。首先本文簡述了汞污染對人體及環(huán)境的危害,并介紹目前汞污染的主要來源及排放現(xiàn)狀。本文詳述了國內(nèi)外現(xiàn)有的汞排放控制技術(shù),活性炭噴射技術(shù)是有效的汞吸附劑,然而由于其大規(guī)模應用的成本與燃煤副產(chǎn)物飛灰的的重復利用問題,使其應用受到阻礙。目前,大量的研究指向飛灰基汞吸附劑的發(fā)開,粉煤灰脫汞技術(shù)已經(jīng)成為現(xiàn)在學者廣泛研究的方面。本文總結(jié)了飛灰作為吸附劑對燃煤煙氣中汞吸附的理論研究成果與進展。本文參考了已有的研究,決定采用溴化氫溶液浸漬方法改性飛灰,開發(fā)固體吸附劑。所開發(fā)的吸附劑在固定床吸附裝置上進行汞的吸附實驗,考察其在室溫條件下對汞的吸附能力,旨在開發(fā)可以代替活性炭的廉價高效的汞吸附劑；用程序升溫熱解析系統(tǒng)對飛灰原樣中的汞及溴化氫改性飛灰經(jīng)吸附實驗所吸附的汞形態(tài)進行研究,以進一步考察汞在鍋爐煙道中轉(zhuǎn)化的過程和改性飛灰對汞的氧化吸附機理。本文實驗中共用到五種燃煤飛灰,其中包括煤粉爐的煙煤飛灰三種和兩種循環(huán)流化床爐的煙煤飛灰,用磨煤機對飛灰進行預處理,使其盡可能均勻,篩分出粒徑小于200目的飛灰用浸漬法進行溴化氫溶液的改性實驗。對飛灰樣品進行掃描電鏡-X射線能譜分析(SEM/EDS).比表面積分析、離子色譜分析和熱重分析等以考察其微觀結(jié)構(gòu)和穩(wěn)定性的變化。固定床吸附裝置上對五種飛灰原樣及其改性樣品的元素汞吸附容量進行了分析,發(fā)現(xiàn)飛灰原樣FA0009和FA0008的汞吸附容量較高,飛灰的汞吸附性能與其中的未燃盡炭含量有明顯的相關(guān)性。同一種飛灰不同濃度的改性樣品的汞吸附容量飛灰改性濃度基本成正相關(guān),但不完全成線性關(guān)系。FA0008和FA0011改性飛灰汞吸附性能明顯提高,其中FA0008在幾種改性飛灰中汞吸附能力突出,最高汞吸附容量為104497ng/g,是原樣飛灰的近100倍,是潛在的活性炭吸附劑的替代品。飛灰原樣中汞的存在形式接近HgCl2、HgS和HgO三種,部分粉煤灰只含有其中的兩種形態(tài)。進行汞吸附實驗后的HBr改性飛灰所吸附的汞的形態(tài)會因所用飛灰的爐型不同而不同：PC爐HBr改性飛灰所吸附的汞形態(tài)主要表現(xiàn)為HgBr2和HgO,含量比接近2：1,汞在改性飛灰上的吸附主要遵循Langmuir-Hinshelwood和Eley-Rideal反應機理。CFB爐改性飛灰所吸附的汞形態(tài)主要表現(xiàn)為HgS和HgO,并沒有HgBr2,汞的吸附主要遵循類似Mars-Maessen的晶格氧化理論。
[Abstract]:Coal-fired power station is the main source of anthropogenic mercury pollution, which is harmful to human health and ecological environment. Firstly, the harm of mercury pollution to human body and environment is briefly introduced, and the main sources and emission status of mercury pollution are introduced. In this paper, the existing mercury emission control technologies at home and abroad are described. Activated carbon injection technology is an effective mercury adsorbent. However, its application is hindered because of the cost of large-scale application and the reuse of fly ash, a by-product of coal combustion. At present, a great deal of research has been focused on the development of fly ash based mercury adsorbent, and fly ash mercury removal technology has been widely studied by scholars. In this paper, the theoretical research results and progress of fly ash as adsorbent for mercury adsorption in coal-fired flue gas are summarized. In this paper, the solid adsorbent was developed by using hydrogen bromide solution impregnation method to modify fly ash. In order to develop a cheap and efficient mercury adsorbent instead of activated carbon, the adsorbent was tested on a fixed bed adsorption device to study the adsorption capacity of mercury at room temperature. The mercury species in fly ash and modified fly ash modified by hydrogen bromide were studied by temperature programmed thermal analysis system in order to investigate the process of mercury conversion in boiler flue and the mechanism of oxidation and adsorption of mercury by modified fly ash. In this paper, there are five kinds of fly ash, including three kinds of bituminous coal fly ash of pulverized coal furnace and two kinds of bituminous coal fly ash of circulating fluidized bed furnace. The fly ash is pretreated with a coal mill to make it as uniform as possible. The modification experiment of hydrogen bromide solution was carried out by impregnation of fly ash with particle size less than 200. The fly ash samples were analyzed by scanning electron microscopy (SEM) and X ray energy dispersive spectroscopy (SEM/EDS). Specific surface area analysis, ion chromatography and thermogravimetric analysis were used to investigate the changes of microstructure and stability. The elemental mercury adsorption capacities of five fly ash samples and their modified samples were analyzed on a fixed bed adsorption device. It was found that the mercury adsorption capacities of fly ash raw samples FA0009 and FA0008 were high. The mercury adsorption performance of fly ash has a significant correlation with the unburned carbon content. The mercury adsorption capacity of the modified samples with different concentrations of fly ash has a positive correlation, but not a linear relationship. The adsorption of mercury in fly ash modified by FA0008 and FA0011 can be improved obviously. The mercury adsorption capacity of FA0008 in the modified fly ash is 104497 ng / g, which is 100 times of that of the original fly ash, and is a potential substitute for activated carbon adsorbent. The forms of mercury in fly ash are close to those of HgCl2,HgS and HgO, and only two of them are found in fly ash. The form of mercury adsorbed by HBr modified fly ash after mercury adsorption experiment will be different according to the furnace type of fly ash used. The main forms of mercury adsorbed by HBr modified fly ash in PC furnace are HgBr2 and HgO, content ratio is close to 2: 1, The adsorption of mercury on modified fly ash mainly follows the reaction mechanism of Langmuir-Hinshelwood and Eley-Rideal. The main forms of mercury adsorbed by CFB furnace modified fly ash are HgS and HgO, and the adsorption of HgBr2, mercury mainly follows the lattice oxidation theory similar to Mars-Maessen.
【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：2394974