State Key Laboratory of Clean Energy Utilization, Zhejiang University , Hangzhou 310027, P. R. China.
Environ Sci Technol. 2014 Oct 21;48(20):12419-26. doi: 10.1021/es503477q. Epub 2014 Oct 3.
A 600 MW(e) down-fired pulverized-coal supercritical boiler, which was equipped with a deep-air-staging combustion system for reducing the particularly high NOx emissions, suffered from the well-accepted contradiction between low NOx emissions and high carbon in fly ash, in addition to excessively high gas temperatures in the hopper that jeopardized the boiler's safe operations. Previous results uncovered that under low-NOx conditions, strengthening the staged-air effect by decreasing the staged-air angle and simultaneously increasing the staged-air damper opening alleviated the aforementioned problems to some extent. To establish low-NOx and high-burnout circumstances and control the aforementioned hopper temperatures, a further staged-air retrofit with horizontally redirecting staged air through an enlarged staged-air slot area was performed to greatly strengthen the staged-air effect. Full-load industrial-size measurements were performed to confirm the availability of this retrofit. The present data were compared with those published results before the retrofit. High NOx emissions, low carbon in fly ah, and high hopper temperatures (i.e., levels of 1036 mg/m(3) at 6% O2, 3.72%, and about 1300 °C, respectively) appeared under the original conditions with the staged-air angle of 45° and without overfire air (OFA) application. Applying OFA and reducing the angle to 20° achieved an apparent NOx reduction and a moderate hopper temperature decrease while a sharp increase in carbon in fly ash (i.e., levels of 878 mg/m(3) at 6% O2, about 1200 °C, and 9.81%, respectively). Fortunately, the present staged-air retrofit was confirmed to be applicable in regulating low-NOx, high-burnout, and low hopper temperature circumstances (i.e., levels of 867 mg/m(3) at 6% O2, 5.40%, and about 1100 °C, respectively).
一台 600 兆瓦（e）的下燃式煤粉超临界锅炉，配备了深度空气分级燃烧系统，以降低特别高的氮氧化物排放，除了料斗中过高的气体温度对锅炉的安全运行构成威胁外，还存在着降低氮氧化物排放和飞灰含碳量之间公认的矛盾。以前的研究结果表明，在低氮氧化物条件下，通过减小分级空气角和同时增加分级空气挡板开度来加强分级空气效果，在一定程度上缓解了上述问题。为了建立低氮氧化物和高燃尽的情况，并控制上述料斗温度，进行了进一步的分级空气改造，通过扩大分级空气槽区域，水平引导分级空气，从而大大加强了分级空气效果。进行了满负荷工业规模的测量，以确认这种改造的有效性。将当前的数据与改造前公布的结果进行了比较。在原始条件下，分级空气角为 45°，没有应用过燃空气（OFA）时，出现了高氮氧化物排放、低飞灰含碳量和高料斗温度（即，6% O2 时分别为 1036mg/m3、3.72%和约 1300°C）。应用 OFA 并将角度降低到 20°，实现了明显的氮氧化物减排和适度的料斗温度降低，同时飞灰含碳量急剧增加（即，6% O2 时分别为 878mg/m3、约 1200°C 和 9.81%）。幸运的是，目前的分级空气改造被证实适用于调节低氮氧化物、高燃尽和低料斗温度的情况（即，6% O2 时分别为 867mg/m3、5.40%和约 1100°C）。
