1000MW双切圆锅炉低氮同轴燃烧系统的模拟分析

Simulation and Analysis of the Low Nitrogen Coaxial Combustion System of a 1000 MW dual-tangentially-fired Boiler

以某电厂1 000 MW单炉膛双切圆锅炉为例,分析了炉膛内低氮同轴燃烧系统的流场特性。得到了单炉膛双切圆炉膛内温度、速度等物理量分布,得到了CFS(偏置风)、SOFA(分离燃尽风)对锅炉结渣性、烟温偏差、NO排放等的影响。结果表明:双切圆燃烧方式的烟速偏差小于单切圆燃烧方式;炉膛按温度分热角和冷角;受冷角布置的影响,适中的CFS风速才能形成"风包煤"特性,防止结渣;SOFA反切使受热面热偏差减小,火焰中心上移,NO浓度逐渐增大;SOFA摆角位置应根据受热面安全性、煤质特性、NO排放综合考虑。

With a 1 000 MW single furnace and dual-tangentially-fired boiler in a power plant serving as an example,a numerical simulation method was used to analyze the characteristics of the flow field in its low nitrogen coaxial combustion system in the furnace. In this process,the distribution of physical variables such as the temperature and speed etc.in the single furnace dual-tangentially-fired boiler was obtained with the influence of the horizontally offset overfire air and separated overfire air( SOFA) on the slagging,flue gas temperature deviation and NO emissions etc. being identified. It has been found that the deviation of the flue gas speed of the dual-tangentially-fired combustion mode is less than that of the single-tangentially-fired combustion mode. The corners of a furnace are divided into hot corners and cold ones. Influenced by the distribution of the cold corners,only a moderate air speed of the horizontally offset overfire air can lead to the 'coal-surrounded-by-air'characteristics and prevent from slagging. The reverse tangential supply of the separated overfire air can force the thermal deviation of the heating surfaces to decrease,the center of the flame to move upwards and NO concentration to gradually increase. In such a case,the setting of the SOFA swaying angle should be taken into consideration in a comprehensive way depending on the safety of the heat-ing surfaces,coal characteristics and NO emissions.