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硫元素对烟气中汞的形态和分布的影响 总被引:8,自引:0,他引:8
采用化学热力平衡分析方法研究了在煤燃烧和气化过程中产生的烟气里痕量元素汞的形态及分布。在0.1MPa下,400—2000K温度范围里,研究了汞—煤系统、汞—煤—硫系统和汞—煤领—氯系统中汞在还原性气氛和氧化性气氛的烟气中的化学形态和分布,着重探讨了煤中的硫元素对汞在烟气中的形态和分布的影响。化学热力平衡分析结果表明,在煤燃烧和气化的最高温度区域里,单质汞是汞的主要形式;在气化的还原性气氛烟气中,汞的主要形式是单质汞,在氧化性气氛的燃煤烟气中,随着烟气温度的降低,单质汞将发生化学反应而生成二价汞的化合物;硫元素的存在可以促进汞元素以固相硫酸汞(HgSO4)的形式沉积,但烟气中高硫含量会抑制汞元素蒸气的氧化以及氮化汞的形成。 相似文献
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烟气汞形态分布及其受氯化物添加剂影响的研究 总被引:2,自引:1,他引:1
在自行设计的一维煤粉燃烧试验台上,研究了烟气汞形态的分布特征,并分析了NaCl作为添加剂与煤混烧对汞形态分布的影响.结果表明:在试验煤种烟气中,气态汞是烟气汞最主要的排放形式,二价汞是气态汞的主要形式,飞灰中的汞含量比底渣中的汞舍量高;NaCl的添加使气态二价汞和单质汞占总汞的百分比都有不同程度的下降,而颗粒态汞的比例相应增加,但随着NaCl添加量的增加,颗粒态汞的增加量逐渐趋于平缓,单质汞的减少量也相应降低,趋势趋于平缓. 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
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860MW煤粉锅炉汞排放及其形态分布的研究 总被引:1,自引:0,他引:1
采用 Ontario-Hydro method(OHM)、汞连续测量仪(Hg-SCEM)和 EPA 固体吸附剂法(Appendix K)测量了860 MW 燃煤电站锅炉烟气中汞排放及其形态分布,并基于煤、黄铁矿、底灰、飞灰、脱硫浆液和烟气中的汞含量,分析了汞在燃烧产物中的质量平衡.结果表明:OHM 和Hg-SCEM 汞测量方法可以用于监测燃煤电站的汞排放,其相对测量偏差小于20%;烟气中总汞的排放浓度随着入炉燃料中汞含量的变化而变化;对于高褐煤掺烧比例的电站锅炉,烟气中元素态汞占总汞比例为48.6%~77.7%,湿法烟气脱硫装置可以脱除90%以上的氧化态汞,电除尘器和湿法烟气脱硫装置的汞脱除效率分别约为15%和34%. 相似文献
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《动力工程学报》2020,(5)
在CFB锅炉燃烧温度下研究了低品质燃料(高碱煤)与生物质燃料(污泥)协同燃烧中重金属元素Pb、Ni和As的迁移特性。结果表明:燃烧温度对重金属元素热力学平衡分布起到重要的作用,温度越高,Pb、Ni和As在气相中的摩尔分数越高;当温度超过1 300℃时,Pb将全部以单质形态迁移至气相中,在CFB锅炉燃烧温度区间里大部分以PbCl2(g)、少量以PbCl的形态固集于飞灰颗粒上;当温度高于1 800℃时,系统中主要成分为Ni(g);在整个燃烧温度区间,As以单质的形态存在于系统中,其摩尔分数随着温度的升高而上升;碱金属Na主要竞争燃料中的Cl和O元素,实现重金属化合物形态的转化;与Na相比,K的竞争是微弱的,在700℃时K竞争Ni化合物中的CrO_4~(2-),导致NiO摩尔分数下降,而在850℃时,K与Ni竞争系统中的O元素,这与700℃的反应过程不同。 相似文献
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针对一台采用尽早配风方式的29MW链条炉进行分区段烟气再循环对锅炉运行及NOx排放特性影响的工业试验。在挥发分析出及燃烧区段煤层下的一次风室混入再循环烟气将有效强化该区段煤层燃烧,降低该区段煤层以上燃烧空间的氧浓度,控制及消减挥发分N向NOx的转化,同时降低了穿过该区段煤层一次风的氧浓度,抑制焦炭N向NOx转化,NO消减效果最高达到25%。在焦炭燃烧区段煤层下的一次风室混入再循环烟气,能够降低穿过床层气流的氧浓度,抑制焦炭氮向NO的转化过程,该区段烟气再循环低氮效果有限,最大降幅9%。再循环烟气可以替代部分一次风,以维持足够的风室风压,进而降低穿过煤层气流的O2浓度,从而强化链条炉区段燃烧特性的低氮特征,实现链条炉的NOx减排。随着工业锅炉NOx排放指标的不断提高,烟气再循环作为一项有效的前置低氮环节,能有效降低整个低氮系统的投资,进而取得较好的经济性。 相似文献
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Kiran K. Sathyanarayanarao Subbarao Camilo C. M. Rindt Anton A. van Steenhoven 《传热工程》2013,34(8-9):733-743
The flue gases emanating from the combustion of fuels or gasification process invariably comprise particulate matter and many chemical species in vapor form. The temperature of the flue gases gradually reduces when passing through different sections of heat exchanger, such as the superheater, evaporator, and so on. If the temperatures of the heat exchanger tube surface and the gas phase are favorable for condensation, the chemical species in the vapor form will condense on the particles and on the tube surface. The particle deposition behavior under these conditions is drastically different from the one observed in dry particulate fouling. In order to model the particle deposition under such circumstances, it is important to evaluate the criteria for particle adhesion to the surface. Impaction experiments of particles impacting a surface coated with a thin liquid film and particles that are coated with a liquid film impacting over a dry surface are performed to evaluate the limiting parameters under which a particle sticks to the surface without rebounding. The effects of liquid viscosity, liquid film thickness, and interacting material properties are evaluated. The experimental results are compared to the results of existing models and a suitable model for fouling is proposed. Controlled fouling experiments are performed for varying liquid films coated over a deposition tube under various process conditions to mimic the condensation effects on fouling. The results are compared with detailed impaction experiments. 相似文献
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Krystal M. Lee 《Energy》1985,10(7):785-791
Low temperature corrosion from flue gases is a common problem in energy recovery systems. We present a simple computation procedure to estimate the dewpoint of combustion gases, which is the limiting design temperature to prevent corrosion. If the composition of fuel oil and the percentage of CO2 or O2 in the flue gases are known, the air ratio, percentage of H2O, p.p.m. of SO3 in the flue gas, and the dewpoint can be estimated with an error of 1.9%. The results indicate that the dewpoint is high because the combustion conditions are not appropriately adjusted, even if low sulfur fuel oil is used. We conclude that both the fuel quality and the combustion conditions are controlling variables in the design and operation of energy recovery systems. 相似文献
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Witold ?ukowski 《Combustion and Flame》2003,134(4):399-409
The combustion of premixed natural gas and air has been studied in a bubbling fluidized bed of inert particles. The temperature of the solids was carefully monitored, using 8 thermocouples, immersed in the bed at different heights. The observed temperature profiles were used to find the height above the distributor at which most of the combustion occurred and on this basis a clear distinction could be made between combustion above the bed and inside the bed. The region where most of the heat of combustion is evolved depends on the average bed temperature. If this temperature is low, the gases burn above the bed or just under its upper surface, but at higher temperatures the process is located close to the distributor. Rapid fluctuations in the measured temperature and pressure indicate that the process inside the bed is not a steady one. The model developed here assumes that combustion takes place inside bubbles of premixed gases, as they move through the bed. A detailed chemical kinetic model was used to calculate the induction period for ignition. The model can predict the height above the distributor at which bubbles should ignite and explode. Comparison of the experimental results with the modeling calculations indicates that the course taken by the process depends on temperature. At the lowest temperatures, the gases burn above the bed. In the high temperature range, where the bubbles ignite is determined by the induction period. At intermediate temperatures the location of the reaction is determined by the depth of the bed and bubble size, with ignition spreading from above the bed to bubbles, which are about to leave, but are still in the bed. That bubbles explode at different heights up the bed is reflected in the acoustic signals registered above and below the bed. The associated changes in the composition of the flue gases are also very characteristic. 相似文献
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设计了一套用于大型燃煤锅炉炉内测温、烟气分析及颗粒取样研究的设备,它包括水冷枪抽气热电偶、飞灰等速取样仪和烟气多功能测量分析仪。利用它对某电厂300MW的W型火焰锅炉沿炉膛高度进行了测温、烟气分析及颗粒采样综合测试试验,并测量了颗粒样品含碳量和粒径分布。结果表明:炉内温度和煤粉细度都是影响煤粉燃尽率的重要因素,当锅炉负荷大于260MW时则煤粉细度成为主导因素;该炉磨煤机出力裕度不大,煤质变差时高负荷下煤粉急剧变粗,机械不完全损失和化学不完全损失都增加.是燃尽率低的主要原因。研究结果为掌握该炉燃烧特性和进行相关技术调整提供了有意义的参考信息。 相似文献