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随着我国对大气污染物排放监管力度的日益严格,NOx控制技术已广泛应用于工业生产的各个领域。作为一种直接、简便的NOx排放控制技术,富氧空气燃烧技术已经出现在燃气锅炉和内燃发动机等行业,然而在燃煤锅炉行业中却鲜有应用。为了验证富氧空气燃烧技术在煤粉工业锅炉中的NOx减排效果,笔者以神府烟煤作为燃料,利用两段式滴管炉试验系统模拟煤粉在锅炉内燃烧的实际情况,采用热态试验方法,研究了烟煤富氧空气分级燃烧的NOx排放特性,并与单级供风、空气分级燃烧2种燃烧方式下的NOx排放情况进行对比。考察了主燃区温度、二次风配比(以主燃区过量氧气系数表示)、二次风氧浓度等关键因素对NOx排放的影响。结果表明:富氧空气分级燃烧的NOx排放显著低于单级供风燃烧,同时也低于空气分级燃烧的NOx排放。主燃区温度为1 300~1 500℃时,富氧空气分级燃烧的NOx排放减少比例比分级配风燃烧提高了6~12个百分点;富氧空气分级燃烧条件下,随主燃区温度升高,煤粉燃烧更加充分,燃料中N元素分解成NHi、HCN等大量中间产物,使主燃区气氛的还原性增强,被还原的NOx比例增加。因此,NOx排放降低且NOx排放减少比例呈现上升趋势;富氧空气分级燃烧的二次风配比对NOx排放具有显著影响,随着主燃区过量氧气系数的升高,NOx排放均呈现先降低后升高的趋势。因此存在最佳二次风配比,使NOx排放浓度最低。主燃区温度为1 300℃时,最佳主燃区过量氧气系数约为0.58;主燃区温度为1 500℃时,最佳主燃区过量氧气系数约为0.55;在主燃区过量空气系数给定的条件下,提高二次风氧浓度可以延长煤粉颗粒在主燃区的停留时间,并在煤粉颗粒表面形成局部富氧环境,促进煤粉充分燃烧,从而增强主燃区气氛的还原性,降低NOx的生成。因此,当二次风氧浓度为21%~31%时,NOx排放随二次风氧含量的升高而降低。随着二次风氧浓度的逐渐升高,NOx排放的降低趋势逐渐放缓。 相似文献
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半焦是低阶煤经低温热解后的产物,其中半焦粉与煤粉工业锅炉常用煤种烟煤相比价格低廉。若能将半焦粉用作煤粉工业锅炉的燃料,既可拓宽煤粉工业锅炉的适用燃料范围,又可增强煤粉工业锅炉的市场竞争力。由于半焦挥发分低、固定碳高,实现其着火和稳定燃烧需要更高的温度,同时,降低NOx初始排放也是一个技术难题。为了实现半焦在煤粉工业锅炉中的稳定燃烧及NOx排放的降低,采用两段式滴管炉开展半焦空气分级燃烧NOx排放规律研究。笔者对半焦空气不分级燃烧NOx排放规律进行了研究,主要探究了主燃区温度(1 000~1 400℃)及过量空气系数的影响,为后续空气分级燃烧降低NOx的效果提供对比依据。半焦空气分级燃烧试验主要研究了主燃区温度(1 000~1 400℃)及二次风比例(0.4~0.8)的影响,并从燃尽率、NOx减少比例、灰样微观孔隙和形貌等方面进行论证,试验结果表明,在空气不分级燃烧条件下,即燃尽风配风比例为0时,随着主燃区温度升高,NOx排放浓度随之迅速升高;随着过量空气系数增加,NOx浓度先迅速增加,过量空气系数大于1.15时,NOx浓度增速变缓;在空气分级燃烧中,相同主燃区温度条件下,二次风比例由高到低变化时,NOx排放呈先迅速下降后缓慢回升的变化趋势,燃尽率先快速升高而后趋于平缓。二次风比例为0.56时(即燃尽风率为0.39),燃尽率达90%,NOx排放浓度降至最低,为120 mg/m^3以下,此时是试验条件下的最佳二次风比例。 相似文献
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焦炭气化反应对空气深度分级工况下燃烧及污染物的生成具有重要影响。笔者采用滴管炉试验与数值计算相结合的方法,研究了主燃区过量空气系数SR1在1.2→0.6变化过程中,焦炭气化对空气深度分级工况下煤粉燃烧和NOx排放特性的影响规律。通过对比滴管炉试验数据与传统模型和改进模型(考虑焦炭气化)结果可知,传统模型对空气分级燃烧的还原性气氛预测存在一定缺陷,改进模型与试验结果较吻合。滴管炉试验及改进模型计算结果表明,空气深度分级工况下,主燃区极度缺氧,燃烧过程由最初的挥发分着火(R1和R2)和焦炭不完全氧化(R4)过渡到以焦炭气化反应(R5和R6)为主导的燃烧状态,大量CO生成,高浓度CO2逐渐被消耗,直至还原区段结束,随着燃尽风加入,O2含量增加,CO被迅速消耗(以R2为主),CO2生成。空气分级工况下NOx排放特性表现为:燃烧器附近NOx浓度高,伴随还原性气氛的形成,出现一定程度的下降后保持较低的NOx水平,随着燃尽风的加入,出现一定程度的"反弹",这是因为还原区结束时,一部分未完全被还原的氮中间体在燃尽风加入后被迅速氧化造成的。 相似文献
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构建骨料烘干煤粉燃烧器内煤粉燃烧行为的控制模型,以污染物含量为评价标准,研究了骨料烘干煤粉燃烧过程中煤粉粒径对排放特性的影响规律. 结果表明,随煤粉粒径增大,煤粉在燃烧器内燃烧不充分,CO排放量增加,CO2排放量逐渐减少,SO2排放量增加,NO排放量在煤粉粒径为100 um时最小. 相似文献
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Super fine pulverized coal combustion is a new pulverized coal combustion technology which has better stability, higher combustion efficiency and lower NOx and SO2 emission than that using conventional particle sizes. In this paper we applied fractal analysis based on power spectral density (PSD) and slit island method (SIM), three-dimensional (3D) surface roughness measurement and surface-topography observations from AFM to form a proper investigative tool which may give a relatively full picture of surface morphology of super fine pulverized coal particles for the first time. The final results indicate that both fractal dimensions calculated by SIM and PSD and roughness of coal particle size increase with the increase of the coal particle size. Besides, the grey relational analysis was used to study the degree of relative importance of the influential factors about the microroughness of coal particle surfaces. The results show that the influence of the coal particle size is the greatest compared with the coal qualities and fractal dimensions.This work provides some reference for a relatively full picture of surface morphology of super fine pulverized coal particles. The findings from this work will be helpful to form the basis and provide guidance for further studies on the chemical and combustion characteristics of super fine pulverized coal particles. 相似文献
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Physical structures and combustion properties of super fine pulverized coal particles of eight Chinese coals, Heshan subbituminous coals and Jincheng lean coals from two areas of China, have been investigated using accelerated surface area and porosimetry, thermobalance (TGA), and Fourier transform infrared spectrometer. Results showed that the particle specific surface area and pore volume increased greatly when the coal particle size was reduced. The higher the carbon content on a dry ash-free basis is, the larger the particle specific surface area and pore volume are. When the coal particle size decreases, the combustion process can be largely improved, ignition temperature is reduced, and SO2 emission from coal combustion is also lower. 相似文献
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煤炭储量丰富,尽管新能源和可再生能源快速发展,煤炭资源在未来几十年仍将作为我国一次能源重要组成部分。同时煤炭利用带来很多环境污染问题,因此未来煤炭资源的利用逐渐向高效、低碳、低污染物排放利用方式转变。随着光学技术的不断发展,涌现出多种适用于煤粉燃烧诊断的原位非接触式光学诊断技术,极大地促进了燃烧学的发展,为煤炭清洁高效利用提供了更多试验手段。介绍了国内外煤粉着火、不同方式下燃烧特性的光学诊断研究进展,对煤粉单颗粒和煤粉颗粒流的着火燃烧过程的光学诊断研究进行总结。目前常用的煤粉燃烧光学诊断技术主要包括全光谱成像、CH*/C2*化学发光成像、平面激光诱导荧光(PLIF)、双色/三色高温计、米氏散射、激光诱导白炽光、相干反斯托克斯-拉曼光谱、激光诱导击穿光谱等多种先进的光学诊断技术,可对煤粉单颗粒、颗粒流的着火延迟、脱挥发分、挥发分燃烧、着火模式、环境因素(环境温度、氧浓度、气氛)、富氧燃烧、水-氧燃烧、煤中碱金属释放等多方面关键问题进行光学诊断研究,为煤炭清洁高效利用提供了理论和试验基础。采用OH-PLIF和三色高温计对热解半焦和神华烟煤混合燃料共燃的着火和燃烧特性进行研究。综合考虑着火延迟和混合物的燃尽率,热解半焦的最佳掺混比为20%,为热解半焦的实际工业应用提供了参考。同时采用500 Hz、5 k Hz高时间、空间分辨率的OH-PLIF技术探究煤粉颗粒流中单颗粒挥发分燃烧的发展过程和挥发分着火的时序演变过程,通过二者的结合获得煤粉颗粒流从着火到挥发分燃烧的时间特性。采用OH-PLIF技术对烟煤和褐煤煤粉颗粒流燃烧火焰的脱挥发分和挥发分燃烧行为进行探究,提出采用OH信号径向分布的相对标准偏差探究火焰稳定性的方法。相同燃烧条件下,烟煤煤粉颗粒流燃烧的稳定性高于褐煤。基于OH-PLIF和CH*化学发光诊断技术,提出一种用于探究煤粉颗粒流中颗粒挥发分燃烧振荡特性分析方法——动态模态分解方法(DMD)。随着氧浓度的增加,挥发分火焰振荡增强。颗粒的聚集可能导致煤粉挥发分燃烧的低频振荡。相反,单独或分离的颗粒燃烧会产生较大的振荡频率。但目前取得的成果还不够完善,需要继续深入开展煤粉燃烧的光学诊断试验研究,对污染物NOx的生成及排放、新型水氧燃烧技术中水蒸气作用机理等方面深入探索,开发出新型清洁煤燃烧技术,为我国煤炭资源清洁高效利用做出贡献。 相似文献
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High temperature air was adopted by combustion in high excess air ratio in a circulating fluidized bed. Experiments on pulverized coal combustion in high temperature air from the circulating fluidized bed were carried out in a down-fired combustor with the diameter of 220 mm and the height of 3000 mm. The NO emission decreases with increasing the residence time of pulverized coal in the reducing zone, and the NO emission increases with excess air ratio, furnace temperature, coal mean size and oxygen concentration in high temperature air. The results also revealed that the co-existing of air-staging combustion with high temperature air is very effective to reduce nitrogen oxide emission for pulverized coal combustion in the down-fired combustor. 相似文献
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Three coal sources, two high-ash coals from South Africa and one bituminous coal from Australia, were evaluated at a pulverized coal combustion test furnace. These combustion trials were carried out on different blending ratios with the two South African coal sources. The NOx emission characteristics of these high-ash coals are similar with those of bituminous coals. The combustion efficiencies on the high-ash coals are lower than those of bituminous coals. The high-ash coals do not affect bituminous coal combustion on the blending combustion. 相似文献
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燃煤过程中颗粒物的形成机理研究进展 总被引:15,自引:2,他引:15
介绍了煤粉燃烧过程中颗粒物的形成机理,包括亚微米飞灰和残灰颗粒的主要形成途径.亚微米颗粒主要来自无机物的气化-凝结过程,在高温条件下无机矿物首先以氧化物、次氧化物或原子的形式气化,当温度降低时,无机蒸气通过均相成核、异相冷凝、凝并、团聚等过程形成细微颗粒.残灰由残留在焦炭颗粒中的矿物转化而成,焦炭破碎和表面灰的聚合是决定残灰最终粒径分布的主要过程,除此之外,对于含外来矿物较多的煤种,矿物破碎对残灰颗粒的形成也有十分重要的影响.最后对燃煤过程中颗粒物的形成机理研究提出了建议. 相似文献
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Tryasunov B. G. Afanas’ev Yu. O. Bogomolov A. R. Dadonov P. V. 《Theoretical Foundations of Chemical Engineering》2011,45(4):537-541
The results of an experimental study of the combustion of pulverized fuel mixtures in a high-temperature cyclone reactor,
a new type of furnace device, are presented. The temperature profiles in the reactor and the composition of the ash residue
are shown. Thermograms of the thermolysis of pulverized coal and sawdust, as well as mixtures thereof, are displayed. It was
demonstrated that in contrast to the combustion of pulverized coal alone, the combustion of a coal-sawdust mixture yields
not only fine ash, but also slag. 相似文献
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Fine particle and trace element emissions from an anthracite coal-fired power plant equipped with a bag-house in China 总被引:5,自引:0,他引:5
Fine particle and trace element emissions from energy production are associated with significant adverse human health effects. In this investigation, the fine particles and trace elements emitted from the combustion of pulverized anthracite coal at a 220 MW power plant were determined experimentally in the size range from 30 nm to 10 μm with 12 channels. The particulate size distributions and morphological characteristics before and after the bag-house were evaluated. The uncontrolled and controlled emission factors of particles are compared with the calculated values from the US Environment Protection Agency, AP-42. Size-classified relative enrichment factors of As, Hg, Se, Cd, Cr, Cu, Al, V, Zn, Mn, Fe were obtained. Relative distributions of trace elements between bottom ash, fly ash and flue gas are determined by mass balance method. The bag-house collection efficiencies of particles and trace elements in the particulate phase are obtained. Finally, the controlled and uncontrolled emission factors of elements of different particulate size fractions are obtained, which will provide useful information for PM2.5 and PM10 emission inventory development, toxic and hazardous pollutant emission estimates and emission standards established for metal-based pollutants from a pulverized coal-fired boiler. 相似文献