LNB改造后燃烧器烧损及NO_x排放高原因分析

Cause Analysis on Burner Burnout and High NO_x Emissions after Low-NO_x Combustion Retrofit for Pulverized Coal Boilers

以某电厂为例,一期1、2号锅炉在低氮燃烧器(low-NOxburner,LNB)改造后,燃烧器设备先后出现烧损问题,且1号炉NOx排放较2号炉高约100 mg/m3,危及锅炉运行安全及脱硝设备正常投运。针对上述问题,从改造方案、设备制造及运行方式等方面分析了原因。发现:(1)2号炉改造设计没有考虑煤种变化,采用了常规稳燃措施,同时运行期间周界风开度小,导致燃烧器区域出现局部高温,燃烧器防磨陶瓷脱落引起煤粉堆积,并在一次风室内燃烧导致燃烧器烧损;(2)1号炉燃烧器制造过程中各喷口间空隙未按设计要求封堵,煤粉被负压回流带入燃烧器隔板堆积燃烧,导致燃烧器烧损。同时,喷口间隙未封堵造成燃烧器二次风漏风严重,降低了空气分级效果,导致NOx偏高。在原因分析的基础上,采取了相应改进措施。结果表明,改进措施有效解决了1、2号炉出现的问题,可为其他电厂类似问题的解决提供参考。

Taking a coal-fired power plant as an example, after low-NOx combustion retrofit in Boilers 1 and 2, the problem of burner burnout in the two boilers arises and the NO,. emissions from Boiler 1 are about 100 mg/Nm^3 more than those from Boiler 2, which endangers the secure operation of the boilel.＇s and the normal commissioning of the denitration equipments. Therefore, the cause analysis on these problems is made from the aspects of retrofit design, equipment manufacturing and operation modes. The analysis figures out that： （1） in the low-NO, combustion retrofit design for Boiler 2, coal type changes are not taken into account, only the routine measures tot combustion stabilization are taken and the surrounding air damper opening degree is small, which leads to local high temperatures in the burner zone and coal powder accumulation and combustion in the primary air pipes caused by burner anti-wear ceramic shedding. （2） during the burner manufacturing of Boiler l, the sealing plates between the burner nozzles are not welded following the design ivquirements. The coal powder is brought back to the burner separators by negative pressure reflux and burned on the separators, which resuhs in burner burnout. Meanwhile, the gaps between the burner nozzles are not sealed, causing serious auxiliary air leakage and reducing the effects of air staged combustion, which leads to high NO, emissions. Based on the above analysis, the improvement is carried out, thus the problems existing in Boilers 1 and 2 are solved effectively. The improvement can provide guidance on solving similar problems for other power plants.