【作者】 张佳；

【导师】 朱群益； 李争起；

【作者基本信息】 哈尔滨工业大学 ， 热能工程， 2011， 硕士

【摘要】 我国丰富的无烟煤储量导致燃用无烟煤电站容量剧增。W火焰锅炉因具有着火条件好、火焰行程长、煤粉燃尽率高等特点,是目前燃用无烟煤的主要炉型。国内W火焰锅炉实际运行中存在燃烧差和NOx排放高等急需解决的问题,近年来国内学者用诸多实验方法对W火焰锅炉展开研究,由于实验研究多方面的局限性,“计算机数值模拟”方法得到推广使用。本文采用流体力学计算软件FLUENT对某电厂采用旋流燃烧器300MWeW火焰锅炉炉内燃烧进行全面数值模拟。计算在锅炉全负荷时,不同二次风与分级风风量比、不同内外二次风叶片角度下炉内燃烧过程,对比炉膛截面的流场分布、温度场分布、各组分浓度分布以及NOx分布情况,并比较沿炉膛高度方向上温度、组分浓度变化规律以及炉膛出口NOx排放量和飞灰含碳量大小,进而分析该型锅炉炉内燃烧特性。选取该电厂实际运行参数下热态工业试验得到的测点温度分布和组分浓度分布与相同参数设置下数值模拟计算得到的对应测点数据进行对比,模拟与试验误差在20%以内,验证模型选取和模拟方法正确。数值模拟结果显示:二次风与分级风风量比增大对煤粉着火影响很小,二次风风量增大,下炉膛高温区温度水平提高、火焰中心下移,但变化幅度均较小,同时分级风风量减少导致分级燃烧效果变差。内外二次风叶片角度变化对炉内燃烧过程影响规律基本一致,但外二次风叶片角度的影响幅度要大于内二次叶片角度,且仅外二次风叶片角度很大时燃烧器出口出现中心回流区;内外二次风叶片角度增大,煤粉着火提前,下炉膛高温区温度水平提高、火焰中心上移,分级燃烧效果变差。综合考虑燃尽效果、炉内结渣风险及NOx排放,建议该电站锅炉最优运行参数选择:二次风与分级风风量比为6:1到7:1之间,内二次风叶片角度为45°左右,外二次风叶片角度为25°到35°之间。更多还原

【Abstract】 In China, the abundant anthracite reserves led to a capacity explosion in power plant. Down-fired boiler is the main furnace burning anthracite, owing to good fire conditions, longer flame journeys, fuel and air classification. At present, so many urgent problems such as poor combustion and high NOx emissions needed to be solved in power plant. In recent years, chinese scholars study the boiler by various experimental methods, and owing to the limitations of experiment, a novel research technique "computer simulation" is widely used.In this paper, the comprehensive numerical simulation of combustion process in a 300MWe down-fired boiler with swirling burner in a power plant was studied by the CFD software—FLUENT. I calculated the combustion process with different ratio of secondary air quantity and tertiary air quantity, different vane angle of the outer and inner secondary air in boiler under full load operation, comtrasted the flow field, temperature, the distribution of gas ingredients and pollution in furnace, compared the temperature, the component concentration variation , NOx emissions and the size of carbon of fly ash along the furnace height direction,then analysed the combustion characteristics in furnace.Comparing the data from thermal industrial test under actual operation parameters with the result from simulation under the same parameter settings, the error bewteen simulation and experiment is within 20%, validate the model selection and simulation method. According to the numerical simulation results, it can be obtained that the ratio of secondary air and staged air has no effect on the ignition, increasing the air ratio appropriately contribute to higher furnace temperature and lower flame center, but the changes are small, the amount reducing of staged air cause the bad combustion. The impact about vane angle of the outer and inner secondary air to the combustion process is consistent, but the degree of the outer secondary air is more bigger. Increasing the vane angle appropriatly contribute to advance ignition and flame expansion, it contribute to higher furnace temperature and higher flame center, the effect of staged combustion is bad.Considering combustion state, slagging risk, NOx emissions, carbon content of fly ash and other factors, I recommend the parameters of the power station boiler in actual operations: the ratio of secondary air and staged air is between 6:1 and 7:1, the vane angle of inner secondary air is about 45°, the vane angle of outer secondary air is between 25°and 35°.更多还原