摘要
采用实验研究了煤粉再燃过程中停留时间与氧浓度影响脱硝效率的依赖关系,发现最佳停留时间与煤粉着火状态有直接关联。在再燃温度及氧浓度较低时,煤粉尚未着火,同相脱硝作用在整个脱硝反应中占优,最佳停留时间与烟气中碳氢化合物的消耗速率有关。随着再燃区氧浓度进一步上升,挥发分着火,大量挥发分被燃烧反应消耗掉,最佳停留时间与挥发分着火时间基本吻合,过多延长停留时间对脱硝没有实际意义。氧浓度更高时煤焦被挥发分的燃烧热引燃,颗粒大幅升温,煤焦的异相脱硝作用在总体脱硝作用中开始占优,并随停留时间延长持续上升,此时最佳停留时间的确定应与煤粉燃尽一起来考虑。
The dependency relationship between the influence of residence time on denitration efficiency and that of oxygen concentration during pulverized coal reburning was investigated by experiment, and a direct correlation between the optimal residence time and the ignition status of coal was found. At lower temperature and lower oxygen concentration in reburning zone, the coal is not ignited yet, the homogeneous reducing reactions dominate the whole denitration process, and the optimal residence time is related to the consumption rates of hydrocarbons in fuel gas. As the oxygen concentration further increases, the volatiles are ignited, lots ofvolatiles are consumed by combustion reactions, the optimal residence time coincides with the ignition time ofvolatiles, and excess residence time is useless for denitration. At higher oxygen concentration, the char is ignited by the volatile combustion, its temperature rises greatly, the heterogeneous reducing reactions begin to dominate the whole denitration process, the denitration efficiency of that increases with prolonging residence time, and the determination of optimal residence time should be considered together with the burnout of pulverized coal.
出处
《工业加热》
CAS
2009年第3期8-12,共5页
Industrial Heating
基金
国家自然科学基金资助项目(50476018)
国家重点基础研究发展规划(973)资助项目(2006CB200303)
关键词
煤粉再燃
最佳停留时间
着火时间
同相
异相
pulverized coal reburning
optimal residence time
igniton time
homogeneous
heterogeneous
