空气分级与偏转二次风联用对炉膛燃烧特性的影响
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摘要
运用CFD软件对某210 MW煤粉锅炉的燃烧过程进行三维数值模拟,采用空气分级燃烧技术,研究不同空气分级深度及偏转二次风对锅炉的燃烧情况及NOx排放的影响,同时引入"敏感性指数",分析了不同空气分级深度下联用偏转二次风前后对锅炉运行的影响程度。结果表明:单独采用空气分级和偏转二次风均能降低NOx排放,二者联用时空气分级起主导作用,NOx排放降低25%~28%;在不同空气分级深度下联用偏二次风措施对炉内燃烧前后影响程度不同,温度场与组分场出现较为相同的影响规律,在一定燃尽风率区间,存在对应(温度、组分)敏感性系数最大的燃尽风率,敏感性指数随燃尽风率的增加呈先增加后减小的变化趋势,即影响程度先增强后减弱;联用偏转二次风改善炉内结渣和高温腐蚀的效果随燃尽风率先增强后减弱,燃尽风率在18%~25%时效果较好,但导致飞灰含碳率显著增加。
By using the CFD software,numerical simulation was taken on a 210 MW tangentially fired boiler.Air staging and deflected secondary air was taken on the combustion process.The furnace combustion characteristic and NOx emission wsa investigated under different OFA rate and deflected secondary air,sensitivity exponent was introduced to analyze the effect of boiler operation under different OFA rate before and after combining with the method of deflected secondary air.Results show that air staging and deflected secondary air method can respectively NOxemission,but air staging plays the leading role,the NOxemission decreased almost 25% to 28%;The effect degree to the combustion is distinct before and after combining with deflected secondary air under different OFA rate.The change of temperature and species field show a similar law,with the increase of OFA rate,the sensitivity exponent firstly increase and then decline;when combine with deflected secondary air,the improved degree of slagging and high temperature corrosion in the furnace are first strengthen and then weaken along with the increasing OFA rate;We can get better relief at the OFA rate of 18%~25%,whereas the mechanical incomplete efficiency increased.
By using the CFD software,numerical simulation was taken on a 210 MW tangentially fired boiler.Air staging and deflected secondary air was taken on the combustion process.The furnace combustion characteristic and NOx emission wsa investigated under different OFA rate and deflected secondary air,sensitivity exponent was introduced to analyze the effect of boiler operation under different OFA rate before and after combining with the method of deflected secondary air.Results show that air staging and deflected secondary air method can respectively NOxemission,but air staging plays the leading role,the NOxemission decreased almost 25% to 28%;The effect degree to the combustion is distinct before and after combining with deflected secondary air under different OFA rate.The change of temperature and species field show a similar law,with the increase of OFA rate,the sensitivity exponent firstly increase and then decline;when combine with deflected secondary air,the improved degree of slagging and high temperature corrosion in the furnace are first strengthen and then weaken along with the increasing OFA rate;We can get better relief at the OFA rate of 18%~25%,whereas the mechanical incomplete efficiency increased.
引文
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[2]高正阳,崔伟春,杨毅栋,等.负荷与燃尽风对NO影响的数值模拟[J].热能与动力工程,2009,24(3).
[3]方庆艳,汪华剑,陈刚,等.燃尽风对超超临界锅炉燃烧特性影响的数值模拟[J].华中科技大学学报,2010,38(11).
[4]王顶辉,王晓天,郭永红,等.燃尽风喷口位置对NOx排放的影响[J].动力工程学报,2012,32(7).
[5]张晓辉,孙锐,孙绍增,等.燃尽风与水平浓淡燃烧联用对NOx生成的影响[J].中国电机工程学报,2007,27(29).
[6]张超,张冰,鲁光武,等.300 MW机组锅炉空气分级燃烧改造[J].热力发电,2014,43(2).
[7]周昊,孙平,池作和,等.600 MW偏转二次风系统锅炉炉内结渣特性的数值模拟[J].燃料科学与技术,2002,8(4).
[8]周昊,童汇源,孙平,等.600 MW锅炉偏转二次风系统炉内流动和NOx排放特性[J].中国电机工程学报,2000,20(11).
[9]陈刚,丘纪华,郑楚光.偏转二次风对炉内结渣的影响[J].动力工程学报,2004,24(1).
[10]周昊,孙平,岑可法.偏转二次风系统600 MW燃煤锅炉NOx排放特性及数值模拟[J].环境科学学报,2001,21(2).
[11]范维澄,万跃鹏.流动与燃烧的模型与计算[M].合肥:中国科技大学出版社,1992.
[12]赵坚行.燃烧的数值模拟[M].北京:科学出版社,2002.
[13]岑可法,姚强,洛仲泱,等.燃烧理论与污染控制[M].北京:机械工业出版社,2004.
[14]RYOICHI K,HISAO M,AKIRA S.Numerical analysis of pulverized coal combustion characteristics using advanced low-NOxburner[J].Fuel,2004,83(6):693-703.
[15]HILL S C,DOUGLAS L SMOOT.Modeling of nitrogen oxides formation and destruction in combustion systems[J].Progress in Energy and Combustion Science,2000,26(3):417-458.
[16]闫志勇,张慧娟.锅炉分级燃烧降低NOx排放的技术改造及分析[J].动力工程学报,2000,24(2).