低NOx改造方案中煤粉再燃风喷口位置的选择

针对国内某热电公司410 t/h四角切圆燃烧锅炉，基于CFD软件平台，采用常规煤粉做再燃燃料，在额定负荷下分别对原有方案和4种不同再燃风喷口位置的改造方案的炉内燃烧及污染物生成进行数值模拟，选择出最优方案实施改造。结果表明，再燃改造燃烧器区间增大，燃烧器区域容积热负荷qv降低，可以有效降低炉膛最高温度，从而抑制热力型NOx的生成。主燃区低氧燃烧可以抑制NOx的生成，使得进入再燃区具有较低的NOx浓度，还原效果更好。再燃风喷口位置越低，受主燃区的干扰越大，还原效果差；再燃风喷口位置越高，停留时间短，还原效果也差，同时炉膛出口烟温越高，飞灰含碳量也越高；选择合适的再燃风喷口位置，可以取得较好的还原效果。通过采用主燃区低氧燃烧，选择合适的再燃风喷口位置，以及燃尽风的作用，使得改造脱硝率达到47.66%，而且锅炉各参数运行稳定，同时锅炉热效率也略有增加，因此对于灰分较低的易燃尽烟煤来说，实施常规煤粉再燃改造可以获得比较满意的效果。工程实践表明，数值计算结果与实际运行数据吻合良好。

Selection of Position of Pulverized Coal Reburning Injector in Low NOx Retrofit Schemes

Numerical simulation was performed on the combustion and contamination generation process under the original scheme and four retrofit schemes with different positions of coal reburning injector using conventional pulverized coal as reburning fuel with the rated load in a 410 t/h tangentially fired furnace in a domestic thermal power plant with CFD software platform. Results show that thermal NOx can be restrained since the highest temperature decreases when the volume heat load qv of burner zone decreases due to extending the burner zone in the reburning retrofit. The better NOx reduction can be achieved since the lower NOx concentration from the main combustion zone where the low oxygen combustion can restrain the NOx. The lower position of reburning injector, the less NOx reduction can be achieved due to the disturbance effect from main combustion zone. On the other hand, the higher position of reburning injector, the less NOx reduction, the higher temperature of the outlet of furnace and the higher unburned carbon of fly ash can also be achieved due to the shorter settle time of reburning coal, but the better NOx reduction can be achieved through choosing an appropriate position of reburning injector. The NOx reduction of 47.66% can be achieved by using low oxygen primary combustion zone, appropriate position of reburning injector, and OFA. Further more, all parameters of the boiler run well and thermal efficiency of the boiler is increased slightly. Therefore, the satisfied NOx reduction can be achieved using conventional pulverized coal as reburning fuel for the low ash content and flammable bituminous coals. Engineering testing shows that the results from numerical simulation are in conformity with real operation condition.