O2/CO2气氛不同粒径煤粉燃烧相互作用机理及对NOx生成影响

The combustion of pulverized coal in O2/CO2 atmosphere is on of the promising new technologies which can both reduce the emission of CO2 and NOx. In spite of the great attention paid to it by relevant scholars and researchers both at home and abroad, many essential issues remain to be addressed for this technology. For example, the high CO2 concentration gives rise to increased specific heat，enhanced gas radiation, and lowered flame temperature, which in turn result in poor combustion stability, lower propagation and burning rate. This proposed project focuses on the key problems of pulverized coal combustion under O2/CO2 atmosphere, aims to improve the coal combustion stability and at the same time, lower the NOx emission. According to the fact that the pulverized coal NOx emission is mainly fuel-NOx under O2/CO2 atmosphere, and the fine pulverized coal has some advanced combustion characteristics such as easier to ignite, high burning rate and lower NOx emission. Theoretical analysis, experimental study, and numerical simulation will be carried out to investigate the interaction mechanism and the effect on NOx formation for for coal with different particle sizes burning during coal ignition and burning process. This study will get a better understanding of the pulverized coal combustion interaction during ignition and burning process and provide a theoretical support for pulverized coal combustion with higher combustion stability, lower NOx emission and economic operation in O2/CO2 atmosphere.

O2/CO2 燃烧技术被认为是既能回收CO2又能抑制NOx生成的具有广阔发展前景的新型燃烧技术，近年来已引起国内外学术界的高度重视。但该技术还有许多关键问题未得到解决，如由于CO2 气体浓度高造成比热增加、气体辐射能力增强、火焰温度低等从而出现煤粉着火延迟、火焰传播速率慢、稳定性较差、燃烧率低等。本项目紧紧围绕O2/CO2气氛下煤粉燃烧存在的主要问题，以同时提高煤粉着火燃烧和降低NOx生成为目标，以不同粒径煤粉燃烧为研究对象，利用细粒径煤粉易于着火燃烧的特性以及煤粉燃烧NOx生成主要为燃料型NOx的特点，从燃烧理论、实验研究以及数值模拟等方面深入分析O2/CO2气氛下，煤粉颗粒间着火燃烧相互影响机理以及对NOx生成的影响，进一步丰富煤粉燃烧着火稳定特性以及NOx生成的知识，为O2/CO2气氛下低NOx煤粉燃烧技术的应用提供理论支撑。

围绕O2/CO2气氛下煤粉燃烧NOx生成机理为研究目标，针对超细煤粉与大粒径煤粉着火与燃烧特性的较大差别，以二者混合制作为不同比例的混合粒径煤粉为研究对象，采用实验和数值模拟方法对燃烧过程NOX生成特性进行研究，深入分析煤粉在O2/CO2气氛下燃烧特性以及NOx生成规律。本项目主要开展了下面几个方面的研究：运用长管火焰爆炸仪进行了系列实验，得到了O2/CO2气氛下煤粉火焰传播速度和长度随混合比的影响规律；在沉降炉内对不同炉温、不同气氛下煤粉燃烧NOx生成特性进行分析，研究了煤粉快速着火条件下不同粒径混合比下NOx生成规律；运用傅里叶红外光谱分析、SEM以及孔分布测试，获得了煤粉粒径比对O2/CO2气氛下煤焦表面官能团的演变、孔隙率以及表面形貌变化；采用数值模拟对O2/CO2气氛下煤粉燃烧NOx生成特性进行了研究，分析了不同粒径煤粉对NOx生成过程的相互作用；建立单颗粒煤粉燃烧的数学模型，得到了煤粉间距对煤粉着火以及燃烧过程的影响；研究了不同粒径分布的煤粉颗粒在层流气体中的燃烧机制及污染物NO生成特性，深入分析了不同粒径燃烧特性对污染物生成的影响。本项目的研究结果揭示了O2/CO2气氛下混合煤粉燃烧相互作用以及NO的生成特性，为提高煤粉着火及燃烧性能降低NOx生成提供理论依据。