煤掺氨燃烧过程中NO生成特性和氨氮转化行为研究

Study on NO formation characteristics and ammonia-nitrogen conversion behavior during ammonia-coal co-firing

在实验室小型沉降炉上开展了氨、煤单独燃烧以及掺混燃烧实验,并结合数值模拟探究了氨煤掺烧的NO生成特性、中间反应过程及氨氮转化行为。结果表明,氨煤掺烧工况下的NO生成浓度远高于氨、煤单烧工况,且高于氨、煤单烧工况总和。掺氨比例为45%(热量比值,下同)时,氨煤掺烧NO排放比氨、煤单烧之和提高70.17%;而掺氨比例不变、燃料质量变为2倍后则提高79.36%,说明煤粉与氨掺烧后会导致NO排放升高。模拟结果表明,掺氨后反应器内NO浓度有一个快速增大阶段,此时氨开始氧化生成NO。氨氧化反应与氨还原反应同时发生,由于氨氧化速率始终高于氨还原速率,导致NO浓度升高。氨煤掺烧后,氨燃烧相关反应平均反应速率峰值增大,峰值出现位置提前,促进了氨氮向NO转化。

Experiments were conducted on a laboratory drop tube furnace for the single-firing of ammonia and coal,as well as co-firing,combined with numerical simulations to investigate the NO formation characteristics,intermediate reaction processes and ammonia-nitrogen conversion behavior in ammonia-coal co-firing.The results showed that the NO concentration generated under ammonia-coal co-firing conditions was much higher than that of ammonia and coal combustion alone,and higher than the sum of ammonia and coal combustion alone.With an ammonia co-firing ratio of 45%(by heat value,the same below),the NO emission of ammonia-coal co-firing was 70.17%higher than the sum of ammonia and coal combustion alone.When the co-firing ratio remained the same and the fuel mass doubled,NO emission increased by 79.36%,indicating that co-firing of coal and ammonia led to an increase in NO emissions.The simulation results showed that the concentration of NO in the reactor increased rapidly after ammonia co-firing,and ammonia began to oxidize and generate NO.Ammonia oxidation reaction and ammonia reduction reaction occurred simultaneously,and since the ammonia oxidation rate was always higher than the ammonia reduction rate,the NO concentration increased.After ammonia-coal co-firing,the peak value of the average reaction rate of ammonia-related reactions increased,and the peak value appeared earlier,which promoted the conversion of ammonia-nitrogen to NO.