【作者】 王顶辉；

【导师】 孙保民；

【作者基本信息】 华北电力大学 ， 热能工程， 2014， 博士

【摘要】 火电厂是大气污染物烟尘、SO2和NOx的主要排放源之一。随着《火电厂大气污染物排放标准》(GB13223-2011)的实施,燃煤电厂如何达到排放标准成为克不容缓的问题,其中尤其以氮氧化物的排放标准最为严格。为了满足这一严格的排放标准,大多电站锅炉均采用炉内降低氮氧化物燃烧结合烟气脱硝技术来实现减排。本论文以燃烧神华煤的两个大容量锅炉为研究对象,分别进行了超临界直流锅炉、亚临界控制循环锅炉的低氮燃烧改造研究,利用数值模拟对旋流燃烧器墙式对冲锅炉和四角切圆锅炉的低氮改造方案进行优化,并通过实验研究进行验证与分析。首先论文以俄制800MW超临界直流锅炉为研究对象,针对旋流燃烧器两侧墙对冲燃烧的T型直流锅炉进行燃烧及NOx排放的数值模拟研究,分析数值模拟结果并结合锅炉实际运行状况,提出了针对这一特殊形式锅炉的低氮燃烧器加空气分级的改造技术方案。利用数值模拟对改造方案的燃尽风率、燃尽风喷口标高及主燃烧器标高进行优化,综合比较安全性和经济性推荐了改造方案。对800MW超临界直流锅炉的数值模拟研究中,着重分析了氮氧化物反应速率这一关键参数,分析了氧浓度、温度、焦炭反应速率与之的关系,揭示了炉膛内氮氧化物生成与还原的规律,找到了主燃区与燃尽区氮氧化物生成的控制因素,主燃区氧浓度是氮氧化物生成的控制因素,燃尽区温度是氮氧化物生成的控制因素。其次论文以某600MW亚临界控制循环锅炉为研究对象,针对燃用易结渣神华煤的四角切圆锅炉进行燃烧及低NOx排放的数值模拟研究。分析锅炉实际运行状况并结合数值计算结果,提出沿炉膛高度垂直方向空气分级和主燃烧区域水平方向空气分级的复合空气分级改造方案。对复合空气分级技术方案的数值模拟研究中,引入等势特征面分析法,着重分析氮氧化物生成速率这一关键参数,利用主燃区与燃尽区氮氧化物生成的控制因素不同的研究结果,进行复合空气分级技术方案的优化。论文同时分析了复合空气分级低NOx改造方案对四角切圆炉膛出口速度偏差及温度偏差的影响,以及对炉膛出口温度、煤粉燃尽程度的影响。上述600MW亚临界控制循环锅炉按照推荐的最佳改造方案进行了复合空气分级低NOx燃烧的改造,最后本文对改造后锅炉燃烧及NOx排放进行实验研究。实验比较改造前后炉膛出口NOx的排放值,同时实验研究了炉膛温度、锅炉效率、近壁区CO/H2S的含量,分析复合空气分级改造后炉膛内的燃烧特性及NOx减排效果,讨论复合空气分级改造对炉膛渣及高温腐蚀的影响。上述实验结果表明,推荐的最佳改造方案有效降低NOx排放的同时,合理配风,充分发挥宽调节比摆动式燃烧器的优势,使得锅炉煤粉燃尽程度虽稍有降低,但锅炉效率并没有降低。更多还原

【Abstract】 Coal-fired utility boiler is one of major sources of dust, SO2and NOx in china. In order to meet the less and less NOx emission limit of<Emission Standard of Air Pollutants for Thermal Power Plants>(GB13223-2011), effective NOx control technology would be applied to the pulverized coal boiler. Lower NOx combustion in the furnace and post-combustion removal process such as SCR system have been widely used to control NOx emission for most power plants. In this paper two the utility boilers burning Shenhua coal have been studied on lower-NOx combustion technology. Opposed firing boiler which is supercritical once-through boiler has been numerically simulated to propose air staging modification. And numerical simulation and experiment have been done to present and finish lower-NOx combustion modification for tangential firing boiler which is subcritical controlled circulation boiler.Firstly combustion and NOx emission of Russian-made800MWe supercritical once-through boiler have been numerically simulated. It’s a T type opposed firing boiler. Based on actural performance, analysing simulating results, lower-NOx combustion technology of air staging have been proposed. Over-fire air rate, over-fire air nozzle elevation and main burner nozzle elevation have been optimized by numerical simulations. And then lower-NOx combustion solution has been recommended for the special kind of boiler.Key parameter of rate of NOx, which directly reveal law of NOx generation and reduction in the furnace, has been analyzed particularly, connected with O2concentration, temperature distribution and char burnout rate. Controlling factors have been found in different combustion zones for NOx formation. O2concentration is major control factor in main combustion zone and temperature is key factor in burnout zone.Secondly combustion and NOx emission of600MWe subcritical controlled circulation boiler has been numerically studied. Shenhua coal is main fuel. Based on real operating condition, Analyzed slagging character, compound air staging technology solution has been proposed to control NOx emission. The solution is expected to decrease NOx formation by vertical air staging along furnace height and horizontal air staging in main combustion zone.In the numerical simulating research of compound air staging, iso characteristics surface has been introduced to analysis important parameters such as rate of NOx etc. Compound air staging technology solution has been optimized considering on the result that O2concentration is major control factor in main combustion zone and temperature is key factor in burnout zone by numerical simulating. Velocity deviation and the temperature deviation at furnace outlet have been discussed for the tangential coal fired boiler before and after modification. Outlet temperature and burnout of pulverized coal have also studied.Lastly600MWe subcritical controlled circulation boiler have been transformed with the above compound air staging. Experimental research has been done after modification of lower NOx combustion technology. NOx emission has been measured before and after modification to evaluate NOx reduction. Temperature distribution, boiler efficiency and CO/H2S content nearing water wall have been analyzed to evaluate combustion characteristics, slagging in the furnace and high-temperature corrosion. Experimental data showed compound air staging technology recommended in last chapter decreased NOx emission greatly. After modification burning efficiency of boiler decreased slightly but the boiler thermal efficiency increased.更多还原