共查询到19条相似文献,搜索用时 140 毫秒
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贫煤焦催化还原NO的实验研究 总被引:5,自引:0,他引:5
本文通过实验研究了在贫氧条件下贫煤焦对NO的还原作用,并与添加催化剂的贫煤焦对NO的还原进行了比较.研究结果表明,原始贫煤焦对NO的还原能力很弱,添加催化剂后NO还原率明显提高,说明催化剂对贫煤焦还原NO具有很好的催化作用.在贫氧条件下催化剂可以降低贫煤焦与NO反应的活化能。提高反应速率.反应区氧气浓度和温度对NO的还原也有重要的影响. 相似文献
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超细煤粉分级燃烧中NOx还原规律的研究 总被引:1,自引:0,他引:1
煤粉再燃技术脱氮效率高而运行费用低,是最行之有效的低NOx燃烧技术之一.通过模拟计算与试验方法,对一维热态煤粉炉内超细煤粉分级燃烧NOx的还原规律进行了研究.研究结果表明再燃燃料越细,对NOx的还原作用越强,最佳再燃燃料粒度为20μm;在相同NOx还原率的情况下,随着再燃燃料粒度的减小,需要的再燃燃料比例减小,再燃区停留时间缩短.以超细煤粉作为再燃燃料不仅使燃烧效率提高,而且对NOx的还原效率也相应提高,达70%左右. 相似文献
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以包含两种低挥发份贫煤在内的四种煤作为主燃料,在一维炉和一台93 kW卧式单角炉上对气体燃料再燃过程及煤粉和再燃燃料的燃尽特性进行了详细实验研究,同时对炉膛内NO_x浓度分布等进行了测量和分析.实验发现,再燃过程除了要采用合适再燃区停留时间外,气体再燃燃料还应选择在炉膛内NO_x浓度较大区域内喷入,以提高再燃脱硝效率.实验结果表明,即使采用低挥发份煤作为主燃料,当再燃区停留时间达到约0.7~0.9 s,气体再燃燃料比例达到10%~15%时,气体燃料再燃过程就能在保证煤粉颗粒燃尽率不明显降低前提下,获得50%以上的再燃脱硝效率. 相似文献
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《工程热物理学报》2016,(12)
为了考察高浓度CO_2对煤焦与NO还原所带来的影响,本文在悬浮床反应器上开展了。N_2和CO_2气氛下煤焦与NO的还原实验。结果表明:在无煤焦或矿物组分催化下CO不与NO发生反应;900℃N_2气氛下,在煤焦与NO反应初期NO还原率保持不变,而在整个反应过程中碳比反应率和CO_2生成比例则持续增大;N_2气氛下,煤焦与NO反应的含碳产物在700℃时以CO_2为主,而随着温度升高CO的生成比例增大,900℃时CO的生成占主导地位;高浓度的CO_2对煤焦-NO还原反应有明显的抑制作用,且温度越高抑制作用越显著,这可能是因CO_2气化抢占碳活性位所致。 相似文献
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船形体煤粉燃烧器NO_x生成特性的研究 总被引:1,自引:0,他引:1
船形体煤粉燃烧器NO_x生成特性的研究钟北京,徐旭常(清华大学煤的高效低污染燃烧国家重点实验室北京100084)关键词煤粉燃烧器,“三高区”原理,NO_x1前言我国电力工业的发展主要依赖于以煤为主要燃料,采用粉状燃烧方式的火力发电。1992年我国年产煤... 相似文献
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在国内某台燃用褐煤的600 MW机组锅炉上进行了煤粉再燃技术示范并进行了工业试验.机组在600 MW负荷下运行时,NOx排放可控制在274 mg/m3(烟气中氧量折算到6%,下同)的水平,比改造前下降了65.36%,同时燃烧效率没有降低.进行了常规通风、空气分级和煤粉再燃三个工况下的试验,结果表明,煤粉再燃对NOx的控制效果最好,其次为空气分级.再燃煤粉比例对NOx排放也有明显的影响,在试验条件下,随着再燃燃料比例的增加,NOx排放呈降低趋势. 相似文献
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《Proceedings of the Combustion Institute》2023,39(4):4409-4418
An insight into the interaction between NO and Na-loaded char is essential to improve the catalytic ability of Na to NO reduction, which will be useful to lower NO emissions during thermal utilization of sodium-containing fuels. Here, the intrinsic kinetics mechanisms for the catalytic reduction of NO by Na-loaded char were discussed in details. Using density functional theory (DFT) calculations, possible reaction pathways were first obtained, followed by evaluation of the rate coefficients through transition state theory (TST) calculations. On this basis, the analyses of both sensitivity and rate of products (ROP) were performed to illustrate the intrinsic kinetic mechanism for the NO reduction by Na-loaded char in a certain combustion condition, with an emphasis on the effects of temperature and NO-to-CO stoichiometric ratio. Results indicated that the catalytic active center –ONa plays an important role in the catalytic reduction of NO by Na-loaded char. Specifically, in most cases, the interaction of NO with Na-loaded char largely depends on the elementary reaction of CNO-Na+NO+CO→21-IM3+CO2. As the stoichiometric ratio of NO to CO increases, the CO-Na+2NO→8-IM4+N2 becomes increasingly dominant. Moreover, higher temperature causes the CNO-Na+NO→20-P + N2O as the dominant reaction. Nonetheless, one thing that these reactions have in common is that they are all related to the catalytic active center –ONa. Therefore, the NO reduction Na-loaded char largely depends on the interaction of NO with the carbonaceous surface containing –ONa. Inspired by this, a conceptual approach was proposed to improve the catalytic performance of Na on NO reduction, and it has been shown to be theoretically feasible. To summarize, the combination of DFT, TST and kinetic calculations is useful to clarify the interaction between NO with Na-loaded char, and it gives a basis for the development of micro-kinetic model. 相似文献
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High-concentration H2S formed in the reduction zone of pulverized coal air-staged combustion can result into the high temperature corrosion of water wall tube of boiler, so it is of great importance to accurately predict H2S concentration for the safe operation of boilers and burners. H2S formation and evolution depends on two steps: the sulfur release from coal conversion and gas-phase reactions of sulfur species. In this study, the sulfur release characteristics from the pyrolysis of 17 coals, including 5 lignite, 9 bituminous coals and 3 anthracites, are investigated in a drop tube furnace (DTF). Sulfur release model is developed to describe the relationship between sulfur release and coal types. A global gas-phase reaction mechanism of sulfur species composed of ten reactions is used to calculate and predict the formation and evolution of H2S, COS and SO2 in the reduction zone of pulverized coal air-staged combustion. A wide range of air-staged combustion experiments of 17 coals are conducted in the DTF at different temperatures and stoichiometric ratios to validate the developed model. The results show that the prediction errors of sulfur species, including SO2, H2S and COS, are within ± 30%, which indicates that the developed prediction model of sulfur species is of great assistance for CFD modeling of actual engineering application. 相似文献
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A.V. Sepman V.M. van Essen A.V. Mokhov H.B. Levinsky 《Applied physics. B, Lasers and optics》2003,77(1):109-117
Quantitative aspects of using cavity ring-down absorption spectroscopy near 226 nm for measurements of NO mole fractions in premixed atmospheric-pressure flames are discussed. Measurements in methane–air flames showed strong broadband absorption near 226 nm by hot CO2 molecules, precluding using the cavity ring-down method in these flames at atmospheric pressure. In hydrogen–air flames, the broadband absorption at this wavelength was substantially lower. Absorption cross sections derived from non-seeded cavity ring-down spectra suggest that absorption by water is the major contribution to the background in these flames. The detectability limit for NO by cavity ring-down measurements in hydrogen–air flames using the current setup is estimated to be 10 ppm. Effects of the cold boundary layer on the measured NO mole fraction were accounted for by measuring the radial distributions of temperature and NO mole fraction using coherent anti-Stokes Raman scattering and laser-induced fluorescence (LIF), respectively. Measurements performed in seeded stoichiometric and lean hydrogen–air flames showed no reburning at temperatures above 1750 K, demonstrating the adequacy of using these flames for calibration of LIF measurements. At lower temperatures, the mole fraction of NO in the hot gases was up to 30% lower than that expected from the degree of seeding in the cold gases. PACS 42.62.Fi; 42.68.Ca; 82.33.Vx 相似文献
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循环流化床炉内石灰石脱硫对NOx排放产生影响,包括对挥发分氮氧化的催化作用以及对CO-NO还原的催化作用。利用固定床反应器对不同条件下CaO颗粒表面NO+CO的催化反应特性进行了探究。实验表明,无氧条件下,CaO能够显著催化CO还原NO,NO转化率与反应温度和CO浓度正相关,与NO浓度负相关.基于Langmuir-Hinshelwood机理建立了CaO催化NO+CO反应动力学模型,模型考虑了颗粒内、外扩散的影响.该模型适用于氧气浓度很低、CO浓度较高条件下。而在有氧气氛中,该反应受到明显抑制,且O2浓度越高,抑制作用越明显;当CaO周围氧气浓度远大于CO时,可忽略CaO对NO的催化还原作用。 相似文献
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Shaozeng Sun Huali Cao Hao Chen Xiaoyu Wang Juan Qian Terry Wall 《Proceedings of the Combustion Institute》2011,33(2):1731-1738
Coal combustion in O2/CO2 environment was examined with a bituminous coal in which the gas-phase and char combustion stages were considered separately. The effects of temperature (1000–1300 °C) and the excess oxygen ratio λ (0.6–1.4) on the conversion of volatile-N and char-N to NOx were studied. Also, the reduction of recycle NOx by fuel-N was investigated under various conditions. The results show that fuel-N conversion to NO in O2/CO2 is lower than that in O2/N2. In O2/CO2 atmosphere, the volatile-N conversion ratios vary from 1–7% to 15–24% under fuel-rich and fuel-lean conditions, respectively. The char-N conversion ratios are 11–28% and 30–50% under fuel-rich and fuel-lean conditions, respectively. The influences of temperature on the conversion of volatile-N to NO under fuel-rich and fuel-lean conditions are contrary. A significant difference for char-N conversion in fuel-rich and fuel-lean conditions is observed. The experimental data of recycle NO reduction indicate that the reduction of recycle NO by gas-phase reaction can be enhanced by volatile-N addition in fuel-lean condition at high temperature, while in fuel-rich condition, the volatile-N influence cancelled out and the overall impact is small. NO/char reaction competes with the conversion of fuel-N to NO at higher temperatures. 相似文献