ABSTRACT
In order to achieve thermal treatment of coal slime and depth control of NOx, a 75 t/h circulating fluidized bed (CFB) boiler arranging post-combustion air is constructed. In the experiment, the combustion atmosphere and the ratio of primary air and secondary air are adjusted to decrease the NOx emissions below 50 mg/m3 (dry basis at 6% O2). Compared with conventional CFB combustion, the post-combustion technology decreases the NOx emissions from 92.9 to 65.4 mg/m3 by adjusting the combustion atmosphere. Then, the primary air volume is adjusted to decrease the NOx emissions further. On the one hand, decreasing primary air volume contributes to inhibiting the NOx generation in the dense phase. On the other hand, it is proved that the combination of the cyclone and a post-combustion chamber plays a crucial role in the de-NOx process of post-combustion technology. More char particles are brought to the cyclone as the primary air volume decreases. The NOx reduction in the cyclone and the post-combustion chamber is promoted. Finally, the NOx emissions are decreased to 42.6 mg/m3 when the ratio of primary air and secondary air is 50.0%. In addition, the SO2 emissions and the combustion efficiency during the ultra-low NOx condition are 23.2 mg/m3 and 98.3%, respectively.
