电站锅炉低氮燃烧与高温受热面换热的联合模拟及分析
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摘要
基于CFD和Matlab平台,建立660MW超临界切圆锅炉炉内燃烧与高温受热面换热的耦合模型。针对不同管屏形状特点,提出Fluent结构和非结构化网格与Matlab离散微元的映射方法,实现了高温受热面壁温在风烟侧和汽水侧的迭代计算。模拟预测值和变工况趋势与锅炉热态试验吻合较好。结果表明,锅炉满负荷运行时,上调SOFA风摆角能降低化学未完全燃烧损失且抑制NO_x的生成,但燃尽风在炉内的消旋长度也减小,导致水平烟道烟温偏差和受热面局部高温区面积增加,使高温再热器炉内最高壁温难以始终维持在材料许用温度以内,对机组长期运行的安全性会产生影响。建议锅炉在以高效、低NO_x生成为燃烧优化目标的同时,兼顾运行调整对高温受热面壁温的影响。
Based on the commercial software CFD and Matlab, a coupled model was established for a 660 MW supercritical tangentially-fired boiler by combining the combustion process in the furnace with the heat transfer in the high-temperature heating surfaces. Considering the shape characteristics of different heating surfaces, a mapping method was proposed to connect the structured and unstructured meshes in Fluent with the discrete nodes in Matlab. Therefore,the tube wall temperature of the high-temperature heat exchangers can be calculated by coupling the fire and water-steam sides. The simulated results and the trend of off-design conditions was validated with the boiler test data. It indicates that, under the full load cases, a greater SOFA vertical tilt angle can reduce the chemical incomplete combustion loss as well as NO_x emission. However, the length in furnace for eliminating residual swirling flow decreases, which enhances the gas temperature deviation and the high-temperature area of the heaters in the horizontal pass. Thus, the maximum wall temperature of the final re-heater cannot always be controlled within the allowable temperature, which threatens to the safety of unit long-term operation. Overall, it suggests that the effect of boiler adjustments on the tube wall temperature should also be considered while conducting combustion optimization.
Based on the commercial software CFD and Matlab, a coupled model was established for a 660 MW supercritical tangentially-fired boiler by combining the combustion process in the furnace with the heat transfer in the high-temperature heating surfaces. Considering the shape characteristics of different heating surfaces, a mapping method was proposed to connect the structured and unstructured meshes in Fluent with the discrete nodes in Matlab. Therefore,the tube wall temperature of the high-temperature heat exchangers can be calculated by coupling the fire and water-steam sides. The simulated results and the trend of off-design conditions was validated with the boiler test data. It indicates that, under the full load cases, a greater SOFA vertical tilt angle can reduce the chemical incomplete combustion loss as well as NO_x emission. However, the length in furnace for eliminating residual swirling flow decreases, which enhances the gas temperature deviation and the high-temperature area of the heaters in the horizontal pass. Thus, the maximum wall temperature of the final re-heater cannot always be controlled within the allowable temperature, which threatens to the safety of unit long-term operation. Overall, it suggests that the effect of boiler adjustments on the tube wall temperature should also be considered while conducting combustion optimization.
引文
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[18]Zima W,Nowak-Oc?ońM,Oc?ońP.Simulation of fluid heating in combustion chamber waterwalls of boilers for supercritical steam parameters[J].Energy,2015,92:117-127.
[19]林宗虎,徐通模.实用锅炉手册[J].北京:化学工业出版社,1999,1:999.Lin Zonghu,Xu Tongmo.Utility boiler manual[J].Beijing:Chemical Industry Press,1999,1:999(in Chinese).
[20]Qi Jing,Zhou Keyi,Huang Junlin,et al.Numerical simulation of the heat transfer of superheater tubes in power plants considering oxide scale[J].International Journal of Heat and Mass Transfer,2018,122:929-938.
[21]美国机械工程师协会.ASME PTC 4-1998锅炉性能试验规程[S].阎维平,译.北京:中国电力出版社,2004.American Society of Mechanical Engineers.ASME PTC4-1998 Fired steam generators performance test code[S].Yan Weiping,Trans..Beijing:China Electric Power Press,2004(in Chinese).
[2]张晓宇.600MW低NOx切圆炉膛燃烧优化分析[J].中国电机工程学报,2016,36(S1):140-146.Zhang Xiaoyu.Analysis of combustion optimization on600MW low nitrogen tangentially coal-fired boiler[J].Proceedings of the CSEE,2016,36(S1):140-146(in Chinese).
[3]Zha Qiongliang,Li Debo,Wang Chang’an,et al.Numerical evaluation of heat transfer and NOx emissions under deep-air-staging conditions within a 600MWe tangentially fired pulverized-coal boiler[J].Applied Thermal Engineering,2017,116:170-181.
[4]Tan Peng,Tian Dengfeng,Fang Qingyan,et al.Effects of burner tilt angle on the combustion and NOx emission characteristics of a 700MWe deep-air-staged tangentially pulverized-coal-fired boiler[J].Fuel,2017,196:314-324.
[5]Liu Y C,Fan W D,Wu M Z.Experimental and numerical studies on the gas velocity deviation in a 600MWe tangentially fired boiler[J].Applied Thermal Engineering,2017,110:553-563.
[6]Chen Shinan,He Boshu,He Di,et al.Numerical investigations on different tangential arrangements of burners for a 600MW utility boiler[J].Energy,2017,122:287-300.
[7]Park H Y,Baek S H,Kim H H,et al.Reduction of main steam temperature deviation in a tangentially coal-fired,two pass boiler[J].Fuel,2016,166:509-516.
[8]Akkinepally B,Shim J,Yoo K.Numerical and experimental study on biased tube temperature problem in tangential firing boiler[J].Applied Thermal Engineering,2017,126:92-99.
[9]Tang Guangwu,Wu Bin,Johnson K,et al.Numerical study of a tangentially fired boiler for reducing steam tube overheating[J].Applied Thermal Engineering,2016,102:261-271.
[10]张晋,袁益超,刘聿拯,等.分隔屏布置对四角布置切圆燃烧锅炉水平烟道空气动力场的影响[J].中国电机工程学报,2010,30(17):6-11.Zhang Jin,Yuan Yichao,Liu Yuzheng,et al.Influence of the panel superheater layout on air dynamic field in tangentially fired boiler horizontal gas pass[J].Proceedings of the CSEE,2010,30(17):6-11(in Chinese).
[11]Tian Dengfeng,Zhong Lijin,Tan Peng,et al.Influence of vertical burner tilt angle on the gas temperature deviation in a 700MW low NOx tangentially fired pulverised-coal boiler[J].Fuel Processing Technology,2015,138:616-628.
[12]Park H Y,Baek S H,Kim Y J,et al.Numerical and experimental investigations on the gas temperature deviation in a large scale,advanced low NOx,tangentially fired pulverized coal boiler[J].Fuel,2013,104:641-646.
[13]Park H Y,Faulkner M,Turrell M D,et al.Coupled fluid dynamics and whole plant simulation of coal combustion in a tangentially-fired boiler[J].Fuel,2010,89(8):2001-2010.
[14]Schuhbauer C,Angerer M,Spliethoff H,et al.Coupled simulation of a tangentially hard coal fired 700℃boiler[J].Fuel,2014,122:149-163.
[15]Yang Yu,Bai Wengang,Wang Yueming,et al.Coupled simulation of the combustion and fluid heating of a300MW supercritical CO2 boiler[J].Applied Thermal Engineering,2017,113:259-267.
[16]许霖杰,程乐鸣,季杰强,等.超/超临界循环流化床锅炉整体数值模型[J].中国电机工程学报,2018,38(2):348-355.Xu Linjie,Cheng Leming,Ji Jieqiang,et al.Integrated numerical model for ultra/supercritical CFB boilers[J].Proceedings of the CSEE,2018,38(2):348-355(in Chinese).
[17]Wang Fengjun,Su Hongliang,Chen Tang,et al.Coupled modeling of combustion and hydrodynamics for a supercritical CO2 boiler[J].Applied Thermal Engineering,2018,143:711-718.
[18]Zima W,Nowak-Oc?ońM,Oc?ońP.Simulation of fluid heating in combustion chamber waterwalls of boilers for supercritical steam parameters[J].Energy,2015,92:117-127.
[19]林宗虎,徐通模.实用锅炉手册[J].北京:化学工业出版社,1999,1:999.Lin Zonghu,Xu Tongmo.Utility boiler manual[J].Beijing:Chemical Industry Press,1999,1:999(in Chinese).
[20]Qi Jing,Zhou Keyi,Huang Junlin,et al.Numerical simulation of the heat transfer of superheater tubes in power plants considering oxide scale[J].International Journal of Heat and Mass Transfer,2018,122:929-938.
[21]美国机械工程师协会.ASME PTC 4-1998锅炉性能试验规程[S].阎维平,译.北京:中国电力出版社,2004.American Society of Mechanical Engineers.ASME PTC4-1998 Fired steam generators performance test code[S].Yan Weiping,Trans..Beijing:China Electric Power Press,2004(in Chinese).