Bai Hao, Zhang Zhongxiao, Li Zixiang, Wu Xiaojiang, Guo Xinwei, Zhang Jian, Bi Degui
School of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai 200093, China.
School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
ACS Omega. 2022 Mar 31;7(14):11853-11861. doi: 10.1021/acsomega.1c07276. eCollection 2022 Apr 12.
The effects of various factors on NO reduction by urea solution injection in the fuel-rich zone (UIFR) under a reducing atmosphere at high temperature were experimentally investigated in a 330 MW tangentially pulverized coal-fired boiler. The experimental results indicated that the NO emission of the boiler could be effectively reduced by using the UIFR method, and the NO reduction efficiency was mostly affected by the operating load of the boiler, the air distribution condition, and the boiler operating oxygen content (BOOC). The higher the load was, the larger the optimal normalized stoichiometric ratio (NSR) and the lower the NO reduction efficiency became. As compared with the condition of conventional air distribution mode, the reducing atmosphere in the combustion zone could be enhanced under the condition of limiting air distribution (LAD) mode, which thus increased the NO reduction efficiency of UIFR and reduced the optimal NSR value. A low BOOC could further increase the NO reduction efficiency of UIFR. When the BOOC was, respectively, reduced to 1.71 and 1.85 vol % under 210 and 240 MW loads, the corresponding NO reduction efficiencies of UIFR reached 45.3 and 41.3% in the LAD mode, respectively. However, the low BOOC increased the CO emission concentration, which could be avoided by the combined use of UIFR and high-velocity over-fire air. These experimental results can provide guidance for the ultra-low NO emission of coal-fired boilers.
在一台330MW切圆燃烧煤粉锅炉中，对高温还原气氛下富燃料区尿素溶液喷射（UIFR）脱除NO的各种影响因素进行了实验研究。实验结果表明，采用UIFR方法可有效降低锅炉的NO排放，NO脱除效率主要受锅炉运行负荷、配风条件和锅炉运行氧量（BOOC）的影响。负荷越高，最佳归一化化学计量比（NSR）越大，NO脱除效率越低。与传统配风方式相比，限制配风（LAD）方式下燃烧区的还原气氛增强，从而提高了UIFR的NO脱除效率，降低了最佳NSR值。低BOOC可进一步提高UIFR的NO脱除效率。在210MW和240MW负荷下，当BOOC分别降至1.71%和1.85%（体积分数）时，LAD方式下UIFR相应的NO脱除效率分别达到45.3%和41.3%。然而，低BOOC会增加CO排放浓度，通过联合使用UIFR和高位燃尽风可避免这一情况。这些实验结果可为燃煤锅炉超低NO排放提供指导。
