O2/CO2气氛下燃煤过程中NOx排放特性实验研究

利用沉降炉在O2/CO2和O2/N2气氛下对煤粉燃烧过程中NOx排放特性进行实验,研究了不同停留时间、燃料/氧化学当量比、温度等因素对燃煤过程中NOx的排放特性的影响,并对2种燃烧方式下NOx的排放特性进行对比.结果表明:在O2/CO2气氛下NOx的生成量远远低于空气气氛下NOx的生成量,其主要原因是在O2/CO2气氛中高CO2质量浓度导致气氛中生成较高含量的CO,从而在未燃烧碳表面发生NO/CO/Char的反应,促进了NO还原为N2;O2/CO2气氛中没有N2,避免了热力型NOx和快速型NOx的生成;约80%的再循环烟气致使NOx的停留时间大为增加,即延长了NOx的还原反应时间,从而降低了NOx的排放.

Experimental study on NOx emission from coal combustion under O2/CO2 atmosphere

The NOx emission characteristics during the pulverized coal combustion process were tested in the one-dimension drop tube under O2/CO2 and O2/N2 atmospheres. The effects of residence time, fuel/oxygen stoichometric ratio and temperature on NOx emission were investigated. The NOx emission characteristics under two atmospheres were compared. The results show that the released NOx is much lower in O2/CO2 atmosphere than in air. The main reason is that high CO2 concentration results in producing abundant CO that promotes the reduction of NO on char surface through the NO/CO/Char reaction. There is no NOx formation via molecular nitrogen because of no any N2 under O2/CO2 atmosphere. About 80% flue gas recycled prolongs NOx residence time and increases deoxidization reaction time, thus reduces NOx emission.