煤焦再燃过程中催化剂对NO还原的影响

以小龙潭褐煤、富拉尔基褐煤和大同烟煤等制成的三种煤焦为再燃燃料 ,研究了它们在再燃区内对NO的还原过程 ,分析了煤灰中金属氧化物对NO还原的影响。为了研究碱金属氧化物对NO还原的催化作用 ,本文特别研究了烟煤焦经过浸泡催化剂处理后对NO的再燃过程及对NO还原率的影响。实验是在NO初始浓度为 10 0 0× 10 -6,反应温度分别为 90 0℃和 110 0℃条件下完成的。实验结果表明 ,煤灰中金属氧化物在再燃区中对NO还原有很强的催化作用 ,原来对NO还原效果很差的烟煤焦 ,添加廉价催化剂后对NO的异相还原有很大的影响 ,在合适的反应温度和化学当量比(SR)条件下 ,煤焦中的催化剂能降低NO还原反应的活化能 ,加快NO还原反应进行的速度 ,从而提高NO的还原率。     

气体燃料再燃对NOx还原的影响

气体燃料再燃是研究较多的降低烟气中ＮＯｘ含量最有效的方法之一。本文以典型的一次燃烧区烟气成分为模拟烟气,研究了不同的气体燃料（ＣＨ４,Ｃ２Ｈ２和Ｃ２Ｈ４）作为再为燃烧料时,再燃区燃烧工况（空气过量系数和再燃温度）对ＮＯｘ再燃过程和ＮＯｘ还原率的影响。通过计算发现,不同组分的气体燃料、再燃区空气过量系数及再燃区对ＮＯｘ的再燃过程和ＮＯｘ还原率都有重要的影响。     

天然气再燃脱硝的原理和技术

就天然气再燃脱硝的机理 ,天然气再燃脱硝技术中的一些关键影响参数对脱硝效率的影响进行了综述 ,最后比较几种再燃燃料对脱硝效果的影响。结果表明 :为了达到较好的脱硝效果 ,再燃区的温度、再燃区的过量空气系数、再燃区的停留时间和再燃燃料的喷入位置应该选择在适当的数值和位置 ,在天然气中增加适当的HCN、NH3 或者热解气对脱硝是有利的。由于这些参数是相互影响的 ,对具体情况应该进行优化     

废轮胎的能源资源化新思路--用于再燃脱硝的探讨

废轮胎的产量日益增加,此类固体废弃物的管理是一个难题。研究如何对其资源化利用对于保护环境和节约资源都是非常有意义的。在对目前有关废轮胎回收利用技术简要回顾之后,提出了以废轮胎为燃料,通过再燃技术用于燃煤锅炉NOx排放的治理,对其可行性进行了讨论。利用国内生产技术以废旧轮胎大规模生产胶粉用于燃煤锅炉的再燃脱硝,能够很好地解决我国目前越来越多的废轮胎的生产现状,并把它们能源资源化利用,而且在利用过程中避免了再生胶、热能、热解利用等过程的二次污染问题。研究已证明．基于废轮胎的燃料不但具有比煤更高的热值,而且具有再燃脱硝燃料的优良性能,用于燃煤锅炉的再燃脱硝过程既可以达到脱除NOx污染排放的目的,同时可以大量地减少宝贵的煤及天然气等化石燃料的消耗。     

再燃烧条件下煤粉热解过程中C、H、N释放特性

在携带流反应装置中研究了再燃条件下煤粉的热解特性,测量了煤粉在高温烟气环境中热解时的质量损失和煤中C、H、N等主要元素的释放份额,分析了煤种、热解温度、热解气氛和煤粉粒径等因素对煤中主要元素释放的影响。结果表明,在实验条件下,煤中H析出份额远大于C、N和煤的质量损失份额,C、N析出份额与煤的质量损失份额基本相同,随煤挥发分含量增加、热解环境温度升高和煤粉颗粒粒径减小,C、H、N释放份额增加,煤焦中H,C值下降。     

Experimental study on nitric oxide reduction through calcium propionate reburning

Performances of calcium propionate (CP) on nitric oxide (NO) reduction are experimentally investigated on a drop tube furnace system from basic reburning (BR), Thermal De-NO_x and advanced reburning (AR) and it is demonstrated to be feasible of using CP as reburning fuel. BR could supply about 80% efficiency with reburning fuel fraction (Rff) and residence time (τ) kept 20-25% and 0.7 s, respectively. Also, oxygen concentration is required to be less than 4%. However, initial NO concentration is not important to reduction. Characteristics of Thermal De-NO_x are also studied. The maximum efficiency of 85.34% could be achieved at 1273 K with mole ratio of ammonia to nitric oxide (β) equaling to 1.75. The corresponding “temperature window” is 1215-1341 K. From 2% to 6% of oxygen concentration, the efficiency of Thermal De-NO_x is constantly depressed by 16.17%. The performances of advanced reburning are greatly optimized and higher efficiency could be achieved using less calcium propionate and ammonia. At 1273 K, efficiency of 93.37% is supplied by AR with Rff = 19.83% and β = 0.8. Also, the corresponding “temperature window” is broadened to 1195-1355 K which is 1.27 times of the one in Thermal De-NO_x at β = 1.75. Meanwhile, the impact of oxygen concentration on NO reduction is weakened in AR.     

10kV电抗器投切引发网络故障浅析

针对一起220 kV变电站10 kV电抗器投切引发的网络故障,分析故障的原因及过程,提出了防范措施。     

Investigation of fuel lean reburning process in a 1.5 MW boiler

This paper examines a detailed study of fuel lean reburning process applied to a 1.5 MW gas-fired boiler. Experimental and numerical studies were carried out to investigate the effect of the fuel lean reburning process on the NO_X reduction and CO emission. Natural gas (CH₄) was used as the reburn as well as the main fuel. The amount of the reburn fuel, injection location and thermal load of boiler were considered as experimental parameters. The flue gas data revealed that the fuel lean reburning process led to NO_X reduction up to 43%, while CO emission was limited to less than 30 ppm for the 100% thermal load condition. The commercial computational fluid dynamics code FLUENT 6.3, which included turbulence, chemical reaction, radiation and NO modeling, was used to predict the fluid flow and heat transfer characteristics under various operational conditions in the boiler. Subsequently, predicted results were validated with available measured data such as gas temperature distributions and local mean NO_X concentrations. The detailed numerical results showed that the recirculation flow developed inside the boiler was found to play an important role in improving the effectiveness of fuel lean reburning process.     

飞灰复燃对炉内颗粒沉积状况的影响分析

实际工程表明,采用飞灰复燃技术对锅炉进行改造,可以减少飞灰所带走的燃料损失,提高锅炉效率,但飞灰回收复燃给壁面颗粒沉积状况也带来了影响.采用FLUENT模拟了SZL15-1.25-AⅡ型双筒链条蒸汽锅炉炉内燃烧,对比分析了采用飞灰复燃技术前后炉内壁面颗粒沉积状况.模拟结果表明,飞灰复燃对锅炉顶墙、前墙及后墙的颗粒沉积速率影响较大,其中飞灰复燃提高了顶墙和前墙的颗粒沉积速率,降低了后墙颗粒沉积速率,而对锅炉前后拱的影响很小可以忽略.减小飞灰入射质量流量或调整飞灰入射角度为水平偏下,均可以降低颗粒在水冷壁的沉积速率,有利于炉膛与水冷壁间的传热.     

褐煤再燃/先进再燃脱硝特性

利用多功能脱硝实验台,研究了典型再燃参数对褐煤再燃脱硝的影响规律,并考察了氨基还原剂和Na2CO3添加剂对褐煤再燃脱硝的促进作用。研究结果表明：褐煤再燃能够取得较高的再燃脱硝效率,在1 323 K再燃温度下,再燃比25%褐煤再燃脱硝效率为76.5%;褐煤再燃存在合适的再燃比、再燃停留时间、再燃区过量空气系数和再燃温度,其值分别为20%～25%、0.81 s、0.6～0.8和1 273～1 323 K;在再燃区中喷入一定量的氨水能提高褐煤再燃脱硝效率,褐煤先进再燃脱硝效率随再燃温度升高先增加后降低,在1 323 K再燃温度下,褐煤先进再燃能获得82.2%的脱硝效率;Na2CO3添加剂使得褐煤氨基先进再燃脱硝效率进一步升高,在1 323 K再燃温度下,喷入473 mg/m3 Na2CO3添加剂后,褐煤先进再燃脱硝效率由82.2%增至85.9%。