HBr改性飞灰对元素汞吸附特性与机理的研究
发布时间：2018-12-29 14:48
【摘要】：燃煤电站是人为汞污染排放的主要来源,对人类的健康、生态环境等都造成了很大危害。首先本文简述了汞污染对人体及环境的危害,并介绍目前汞污染的主要来源及排放现状。本文详述了国内外现有的汞排放控制技术,活性炭喷射技术是有效的汞吸附剂,然而由于其大规模应用的成本与燃煤副产物飞灰的的重复利用问题,使其应用受到阻碍。目前,大量的研究指向飞灰基汞吸附剂的发开,粉煤灰脱汞技术已经成为现在学者广泛研究的方面。本文总结了飞灰作为吸附剂对燃煤烟气中汞吸附的理论研究成果与进展。本文参考了已有的研究,决定采用溴化氢溶液浸渍方法改性飞灰,开发固体吸附剂。所开发的吸附剂在固定床吸附装置上进行汞的吸附实验,考察其在室温条件下对汞的吸附能力,旨在开发可以代替活性炭的廉价高效的汞吸附剂；用程序升温热解析系统对飞灰原样中的汞及溴化氢改性飞灰经吸附实验所吸附的汞形态进行研究,以进一步考察汞在锅炉烟道中转化的过程和改性飞灰对汞的氧化吸附机理。本文实验中共用到五种燃煤飞灰,其中包括煤粉炉的烟煤飞灰三种和两种循环流化床炉的烟煤飞灰,用磨煤机对飞灰进行预处理,使其尽可能均匀,筛分出粒径小于200目的飞灰用浸渍法进行溴化氢溶液的改性实验。对飞灰样品进行扫描电镜-X射线能谱分析(SEM/EDS).比表面积分析、离子色谱分析和热重分析等以考察其微观结构和稳定性的变化。固定床吸附装置上对五种飞灰原样及其改性样品的元素汞吸附容量进行了分析,发现飞灰原样FA0009和FA0008的汞吸附容量较高,飞灰的汞吸附性能与其中的未燃尽炭含量有明显的相关性。同一种飞灰不同浓度的改性样品的汞吸附容量飞灰改性浓度基本成正相关,但不完全成线性关系。FA0008和FA0011改性飞灰汞吸附性能明显提高,其中FA0008在几种改性飞灰中汞吸附能力突出,最高汞吸附容量为104497ng/g,是原样飞灰的近100倍,是潜在的活性炭吸附剂的替代品。飞灰原样中汞的存在形式接近HgCl2、HgS和HgO三种,部分粉煤灰只含有其中的两种形态。进行汞吸附实验后的HBr改性飞灰所吸附的汞的形态会因所用飞灰的炉型不同而不同：PC炉HBr改性飞灰所吸附的汞形态主要表现为HgBr2和HgO,含量比接近2：1,汞在改性飞灰上的吸附主要遵循Langmuir-Hinshelwood和Eley-Rideal反应机理。CFB炉改性飞灰所吸附的汞形态主要表现为HgS和HgO,并没有HgBr2,汞的吸附主要遵循类似Mars-Maessen的晶格氧化理论。
[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.
【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：2394974
[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.
【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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