共查询到19条相似文献,搜索用时 171 毫秒
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由于在吸附剂中引入卤族元素可以极大地促进其对燃煤烟气中Hg~0的脱除,考虑到海水中含有丰富的氯元素,因此采用海水改性来提高吸附剂脱除Hg~0的效率。在氧气体积分数为6%的氮氧(94%N_2+6%O_2)基本气氛下进行了改性吸附剂脱除Hg~0的活性测试。研究表明:经海水改性后提高了吸附剂的脱汞效率且改性吸附剂对Hg~0主要以化学吸附的方式脱除;改性吸附剂的最高脱汞效率达到90%,相比于Na(13X)分子筛原样的脱汞效率提升了约40%,表明通过海水改性来提高吸附剂脱汞效率是可行的。 相似文献
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采用机械力耦合NaBr的方法对燃煤飞灰进行机械化学改性。在固定床反应装置上研究了NaBr质量浓度及吸附温度对改性飞灰脱汞性能的影响。结果表明:改性飞灰的脱汞效率受NaBr溶液质量浓度和吸附温度的影响较为明显,脱汞效率随NaBr溶液质量浓度的增加而增加,同时吸附温度越高汞吸附性能越好;在350 ℃的吸附温度下,机械力耦合0.5%浓度的NaBr对汞几乎完全吸附;在机械力与NaBr的协同改性过程中,随着NaBr溶液质量浓度的增加,原始飞灰中粒径占比发生改变,飞灰表面破碎程度增大,飞灰部分表面官能团发生改变,产生了活性位点与新的活性官能团,从而增强了对汞的吸附性能,促进了对汞的吸附脱除。 相似文献
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在固定床吸附机理研究实验台上,利用汞在线分析仪研究了超声波辅助沉淀法制备的氧化铁吸附剂在N2和模拟煤气气氛下对单质汞的吸附作用,分析煤气中气体成分对氧化铁吸附剂脱汞性能的影响.实验结果表明:氧化铁吸附剂在纯N2气氛下的脱汞效率较低;H2S可以促进氧化铁吸附剂对汞的吸附脱除,脱汞效率能够长时间维持在90%以上;在吸附床温度为150℃条件下,模拟煤气中的还原性气体CO和H2对氧化铁吸附剂的脱汞性能影响不大;模拟煤气中水蒸气抑制了氧化铁吸附剂对单质汞的吸附脱除;随着吸附床温度的升高,氧化铁吸附剂的脱汞效率先增高,而后逐渐降低. 相似文献
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《能源学会志》2020,93(4):1615-1623
In order to get a cost effective and recyclable sorbent for mercury removal, a series of magnetic iron-carbon (Fe–C-x) sorbents was developed by co-precipitation. The physical and chemical properties of obtained sorbents were evaluated through various characterization methods. According to the results, Fe3O4 precipitate on carbon weakens the surface properties, but mercury removal performance in simulated flue gas is excellent. For flue gas components, HCl promotes mercury oxidation and adsorption on sorbents, O2 has limited effect on mercury removal and SO2 plays an inhibitive role. NO could enhance mercury oxidation with O2 existence because of the generation of NO2, which could react with Hg0 through heterogeneous reaction over iron-carbon surface. Besides, effects of temperature and regeneration performance were further researched under simulated flue gas. Apart from higher temperature will decompose mercury compounds and cause the removal efficiency decrease, Fe–C-3 sorbent shows excellent Hg0 removal performance at the temperature window of 100–200 °C. Exceptional regeneration performance on Hg0 removal indicates that spent sorbent could be regenerated. 相似文献
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A review on the utilization of fly ash 总被引:5,自引:0,他引:5
Fly ash, generated during the combustion of coal for energy production, is an industrial by-product which is recognized as an environmental pollutant. Because of the environmental problems presented by the fly ash, considerable research has been undertaken on the subject worldwide. In this paper, the utilization of fly ash in construction, as a low-cost adsorbent for the removal of organic compounds, flue gas and metals, light weight aggregate, mine back fill, road sub-base, and zeolite synthesis is discussed. A considerable amount of research has been conducted using fly ash for adsorption of NOx, SOx, organic compounds, and mercury in air, dyes and other organic compounds in waters. It is found that fly ash is a promising adsorbent for the removal of various pollutants. The adsorption capacity of fly ash may be increased after chemical and physical activation. It was also found that fly ash has good potential for use in the construction industry. The conversion of fly ash into zeolites has many applications such as ion exchange, molecular sieves, and adsorbents. Converting fly ash into zeolites not only alleviates the disposal problem but also converts a waste material into a marketable commodity. Investigations also revealed that the unburned carbon component in fly ash plays an important role in its adsorption capacity. Future research in these areas is also discussed. 相似文献
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Li JIA Baoguo FAN Xianrong ZHENG Xiaolei QIAO Yuxing YAO Rui ZHAO Jinrong GUO Yan JIN 《Frontiers in Energy》2021,15(1):112-123
The mercury emission was obtained by measuring the mercury contents in flue gas and solid samples in pulverized coal (PC) and circulating fluidized bed (CFB) utility boilers. The relationship was obtained between the mercury emission and adsorption characteristics of fly ash. The parameters included unburned carbon content, particle size, and pore structure of fly ash. The results showed that the majority of mercury released to the atmosphere with the flue gas in PC boiler, while the mercury was enriched in fly ash and captured by the precipitator in CFB boiler. The coal factor was proposed to characterize the impact of coal property on mercury emissions in this paper. As the coal factor increased, the mercury emission to the atmosphere decreased. It was also found that the mercury content of fly ash in the CFB boiler was ten times higher than that in the PC boiler. As the unburned carbon content increased, the mercury adsorbed increased. The capacity of adsorbing mercury by fly ash was directly related to the particle size. The particle size corresponding to the highest content of mercury, which was about 560 ng/g, appeared in the range from 77.5 to 106 µm. The content of mesoporous (4–6 nm) of the fly ash in the particle size of 77.5–106 µm was the highest, which was beneficial to adsorbing the mercury. The specific surface area played a more significant role than specific pore volume in the mercury adsorption process. 相似文献
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Mercury, as a global pollutant, has raised worldwide concern due to its high toxicity, long-distance transport, persistence, and bioaccumulation in the environment. Coal-fired power plants (CFPPs) are considered as the major anthropogenic mercury emission source to the atmosphere, especially for China, India, and the US. Studies on mercury in coal combustion process have been carried out for decades, which include content and occurrence forms of mercury in coal, mercury transformation during coal combustion, sampling, co-removal and emission of mercury in CFPPs, mercury removal technologies for CFPPs. This current review summarizes the knowledge and research developments concerning these mercury-related issues, and hopes to provide a comprehensive understanding of mercury in coal combustion process and guidance for future mercury research directions.The average mercury content in the coal from China, the US, and South Africa is 0.20, 0.17, and 0.20 mg/kg, respectively, which is higher than the world's coal average value of 0.1 mg/kg. In general, mercury in coal is in the forms of sulfide-bound mercury (mainly pyritic mercury, dominant), clay-bound mercury, and organic matter-bound mercury, which are influenced by diagenetic, coalification, and post-diagenetic conditions, etc. Mercury transformation in coal combustion includes homogeneous (without fly ash) and heterogeneous (with fly ash) reaction. The transformation is affected by the coal types, flue gas components, flue gas temperature, combustion atmosphere, coal ash properties, etc. The effects of chlorine, NOx, SO2, H2O, O2 NH3 on elemental mercury (Hg0) homogeneous oxidation and the influence of physical structure properties, unburned carbon, and metal oxides in fly ash as well as flue gas components on Hg0 heterogeneous transformation are systematically reviewed in detail. For the mercury transformation in oxy-coal combustion, O2 promotes Hg0 oxidation with Cl2 while NO and CO2 inhibit or do not favor that reaction. CO2 increases Hg0 oxidation in the atmosphere of NO and N2. SO2 will limit Hg0 oxidation, while HCl has a higher oxidation effect on Hg0 than that in air-coal combustion atmosphere. Fly ash plays an important role in Hg0 oxidation. SO3 inhibits mercury retention by fly ash while H2O promotes the oxidation.The sampling or analysis principle, sampling requirements, and advantages and disadvantages of the commonly used on-site mercury sampling methods, namely, Ontarion Hydro Method (OHM), US EPA Method 30B, and Hg-CEMS, are compared. The air pollution control devices (APCDs) in CFPPs also have the mercury co-removal ability besides the conventional pollutants, such as NOx, particulate matter (PM), SO2, and fine PM. Selective catalytic reduction (SCR) equipment, electrostatic precipitator (ESP) or fabric filter (FF), and wet flue gas desulfurization (WFGD) device are good at Hg0 oxidation, particulate mercury (Hgp) removal, and oxidized mercury (Hg2+) capture, respectively. The Hg0 oxidation rate for SCR equipment, and the total mercury (Hgt, Hgt = Hg0 + Hg2+ + Hgp) removal rate for ESP, FF, and WFGD device is 6.5–79.9%, 11.5–90.4%, 28.5–90%, and 3.9–72%, respectively. Wet electrostatic precipitator (WESP) can capture Hg0, Hg2+, and Hgp simultaneously. The mercury transformation process in SCR, ESP, FF, WFGD, and WESP is also discussed. Hgt removal in ESP+WFGD, SCR+ESP+WFGD, SCR+ESP+FF+WFGD, and SCR+ESP+WFGD+WESP is 35.5–84%, 43.8–94.9%, 58.78–73.32%, and 56.59–89.07%, respectively. The mercury emission concentration in the reviewed CFPPs of China, South Korea, Poland, the Netherlands, and the US is 0.29–16.3 µg/m3. Mercury in some fly ash and gypsum, and in most WFGD and WESP wastewater, is higher than the relevant limits, which needs to be paid attention to during their processing.Mercury removal technologies for CFPPs can be divided into pre-combustion (including coal washing technology and mild pyrolysis method), in-combustion (including low-NOx combustion technology, circulating fluidized bed combustion technology, and halogens addition into coal), and post-combustion (including existing commercial SCR catalyst improvement, inhibiting Hg0 re-emission in WFGD, mercury oxidizing catalysts, injecting oxidizing chemicals, carbon-based adsorbents, fly ash, calcium-based adsorbents, and mineral adsorbents) based on the mercury removal position. The mercury removal effects, mercury removal mechanism, and/or influencing factors are summarized in detail. One of the regenerable mercury removal adsorbents, the magnetic adsorbent modified by metal oxides or the metal halides, is the most promising sorbent for mercury removal from CFPPs. It has advantages of high mercury removal efficiency, low investment, easy separation from fly ash, and mercury recovery, etc. Lastly, further works about mercury transformation in coal combustion atmosphere, mercury co-removal by APCDs, the emission in CFPPs, and mercury removal technologies for CFPPs are noted. 相似文献
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《能源学会志》2020,93(2):666-678
Coal-fired power plant is the largest anthropogenic mercury source. Active carbon injection technique has been widely used to control the mercury emissions. However, high operation cost limits its development and it is necessary to find other potential mercury sorbents. In this study, raw semi-coke and a series of novel cerium (Ce) modified semi-cokes were synthesized and utilized for removing elemental mercury (Hg0) from simulated flue gas. It is noteworthy that the efficiencies were tested without hydrogen chloride (HCl) in order to evaluate the sorbents efficacy for low-chlorine (Cl) coal. The results show that the modified sorbents exhibited the best performance at 150 °C. The performance of sorbent could be reinforced due to the existence of oxygen (O2), nitric oxide (NO) and HCl. The adverse effect caused by sulfur dioxide (SO2) reduced dramatically after Ce modification. The negative impact of ammonia (NH3) on Hg0 removal in this study could be neglected owing to the tiny concentration of NH3. Raw semi-coke provided sufficient carbon content, which is favorable to mercury adsorption. As Ce loading increased, the carbon structure changed and the crystal of cerium oxide was formed in the modified semi-coke. The mass fraction of cerium oxide on the sorbent was over 4.4% when the concentration of Ce modification solution was higher than 0.2 mol L−1. The redox reaction activity and the oxygen storage ability of Ce3+/Ce4+ gave a huge boost to the performance of modified semi-coke. The addition of Ce also had an impact on the proportion of oxygen species. 相似文献
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脱硫废水富含氯离子,是燃煤电厂难以处置的污染物之一。使用荷电喷雾干燥的方法,将富氯脱硫废水返喷除尘器前,研究了其干燥迁移规律和对烟气成分的影响,证实了将其有害成分固定到飞灰颗粒物中脱除实现零排放的可行性;同时研究了荷电喷雾过程对超细粉尘的凝并作用,可以有效的提高常规除尘器对超细粉尘的脱除效率。富含氯离子的脱硫废水对烟气中的元素态汞具有促进氧化脱除的作用,为脱硫废水零排放同时促进多种污染物联合脱除提出了一条新思路。 相似文献
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氯和灰分对大型燃煤锅炉烟气中汞形态的影响 总被引:1,自引:0,他引:1
采用安大略标准燃煤烟气汞采样分析方法,对大型燃煤锅炉出口烟气中汞形态的形成及分布机理进行了研究.分析了煤中Cl、灰分及采样位置对锅炉出口烟气中汞形态分布的影响.结果表明:烟气中的飞灰能够直接影响颗粒汞与气态汞之间的平衡比例;煤中灰分含量越多,锅炉出口烟气中颗粒汞所占比例越大;煤中Cl对气态汞中Hg0向Hg2 形态转变有促进作用;较高的烟气温度和较短的停留时间会严重阻碍飞灰对汞的吸附,影响颗粒汞的形成,同时也会阻碍Cl元素对Hg0的氧化作用. 相似文献