为降低烟气参数的不均匀分布对选择性非催化还原（SNCR）脱硝的影响，对220MW燃煤锅炉烟气状态分布特征及其对脱硝效果的影响进行数值研究，同时探讨了还原剂雾化粒径和喷入量的优化方案。研究表明，为保证还原剂在温度窗口内具有充足的反应时间，液滴的最佳平均粒径随高度而改变；此外，由于还原剂喷入区域烟气存在旋流作用，还原剂随烟气向炉膛局部“富集”，导致出口NH3/NO分布不均匀。据此，提出了喷枪雾化参数的优化策略：①对不同高度处液滴的平均雾化粒径进行分层优化；②在固定氨氮摩尔比下，根据旋流特征调整不同区域喷枪的流量分配。模拟结果显示，氨氮摩尔比保持1.2时，相比电站基准工况，优化方案能够将脱硝率从36.8%提高到42.1%，漏氨量降低49%；此外，随着氨氮摩尔比的增大，优化方案体现出更好的脱硝效果，但是优化程度略有降低。%To reduce the effect of unevenly-distributed fume parameters on the selective non-catalytic reduction(SNCR),the state distribution of fume and its effect on the NOx removal efficiency of a 220 MW coal fired boiler were numerically studied. Meanwhile,the optimization methods for atomization diameter and spray flux of reductant were discussed. It is found that the most suitable average diameter of spray drops varies at different heights to guarantee the sufficient reaction time of SNCR process in the temperature window. Furthermore,a whirl flow remains in the SNCR area,along with which reductants are enriched to partial furnace,thus causing an uneven distribution of NH3/NO at the outlet. Accordingly,optimization strategies of atomization parameters are proposed:①Optimizing the average diameter of spray drops at different heights by layer;②Adjusting the distribution of spray flux in different regions according to the whirlwind characters under certain fixed molar ratio of NH3/NO. The simulation results indicate that the optimization plan can promote NOx removal efficiency to 42.1% from 36.8% and reduce NH3 slip by 49% compared to those of fiducial injection condition at the power plant under a NH3/NO molar ratio of 1.2. In addition,the optimization method gains preferred denitration results under higher NH3/NO molar ratios,while the effects of optimization slightly descend simultaneously.
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