为了研究不同种类气体再燃和再燃喷口下倾角度对燃煤锅炉燃烧特性的影响，基于FLUENT软件，选取某超超临界660 MW锅炉为研究对象，搭建再燃气体耦合燃煤燃烧模型对锅炉进行改造，在主燃烧区上部增设再燃区，研究不同种类气体再燃和不同再燃喷口下倾角度对锅炉温度场，CO、CO2、O2组分场以及NOx排放量的影响。结果表明：再燃气体的加入会使锅炉主燃烧区炉膛温度降低，但会引起再燃区和燃尽区烟气温度升高，且随着再燃气体的加入，炉膛火焰中心上移，出口烟气温度上升；再燃导致炉膛出口CO体积分数升高，而O2和CO2体积分数降低，NOx排放量明显下降；与纯煤工况相比，秸秆气、甲烷和沼气掺烧时的NOx排放量分别下降了20.1%、26.2%和25.2%。再燃喷口适当向下倾斜可以改善炉内流场强度，增强锅炉燃烧效果，同时增加再燃燃料在再燃区的停留时间，有效降低炉膛出口NOx排放量。当向下倾角为15°时，减排效果最好，秸秆气、甲烷和沼气再燃时的NOx排放量分别下降了31.73%、35.66%和33.85%。本研究为燃煤锅炉气体再燃装置的设计及运行提供参考。

In order to investigate the effects of different types of gas and re-burning nozzle downward inclination angle on the combustion process of boiler,based on the FLUENT software,an ultra-supercritical 660 MW boiler was selected as the research object，and the re-burning gas coupled coal-fired combustion model has been built to  transform the boiler. A reburning zone was added at the upper part of the main combustion zone. The effects of different kinds of gas reburning and different reburning nozzle downdip angles on boiler temperature field,CO,CO2,O2 components and NOx emissions were studied. The results show that,the re-burning gas will make the main combustion zone temperature lower,and the flue gas temperature in the re-burning zone and the burnout zone increase. With the addition of re-burning gas,the center of the furnace flame moves up,and the temperature of the outlet flue gas also increases. The re-burning results in the increase of CO concentration at the furnace outlet,but the decrease of the concentration of O2 and CO2 and the significant decline of NOx emissions. Compared with the pure coal condition,the NOx emission reductions of straw gas,methane and biogas are 20.1%,26.2% and 25.2% respectively. The proper downward slope of the re-burning nozzle can improve the intensity of the flow field in the furnace,enhance the combustion effect of the boiler,and increase the residence time of the re-burning fuel in the re-burning area,and effectively reducing the NOx emission at the furnace outlet. When the downward inclination angle is 15°,the emission reduction effect is the best. The NOx emissions during re-burning of straw gas,methane and biogas are decreased by 31.73%,35.66% and 33.85%,respectively. The research methods and conclusions of this paper have certain realistic reference significance for the research and application of biomass gas and coal blending utilization in large coal-fired boilers.

0 引言

1 试验

   1.1 燃煤锅炉结构及再燃改造

   1.2 燃料特性

   1.3 数学模拟与计算方法

   1.4 燃煤锅炉气体再燃降低污染物排放原理

2 结果分析

   2.1 模型验证

   2.2 耦合燃烧对温度及烟气组分模拟结果分析

3 结论