高浓度煤粉燃烧低NO_x排放特性的试验研究

Experimental Study on Characteristics of Low NO_x Emission During the Dense Phase Pulverized Coal Combustion

为了探讨高浓度煤粉燃烧对NOx排放特性影响的内在机理,在一维火焰炉试验台上,对3种典型煤在不同煤粉浓度燃烧下的NOx前驱物HCN与NH3在主燃区进行了测试,对气相催化还原剂CO及沿炉膛轴向的NOx释放特性进行了分析。试验结果表明:与常规浓度相比,高浓度煤粉燃烧条件下的NOx排放量最大可降低2．2倍。对于不同煤种,最大限度抑制NOx排放的最佳煤粉浓度控制在过量空气系数0．7左右,煤粉燃烧过程中的NOx主要在着火区距炉膛入口0．2～0．4m处产生。在高煤粉浓度下,燃料氮向HCN与NH3的转化率均远远低于常规浓度,同时燃烧过程中产生的大量CO对NOx还原分解的加速是高浓度煤粉燃烧低NOx排放的关键所在。

in order to discuss the mechanism of NOx emission during the dense phase pulverized coal combustion, HCN and NH3 produced the primary combustion zone were investigated for three typical pulverized coals under the different concentration by the one-dimensional flame furnace, the catalytic reductant CO for gas phase and the performance of NOx emission along the axial direction of the one-dimensional furnace were analyzed. The results show that the emission of NOx is reduced 2.2 times to a great degree from conventional concentration to dense phase pulverized coal. For the different pulverized coal, the excess air ratio is about 0.7 for the optimal pulverized coal concentration to control the emission of NOx, NOx is produced mainly on the ignition zone 0.2～0.4 meters away from the furnace entrance during the combustion. Under the condition of dense phase pulverized coal, the conversion rates both from fuel-N to HCN and NH3 are far lower than that of conventional concentration. Moreover, a great amount of CO produced during the combustion accelerates the reduction and decomposition of NOx, which is the key of low NOx emission under the dense phase pulverized coal combustion.