锅炉水冷壁腐蚀、结焦问题的数值模拟研究
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摘要
为了研究某350 MW前后墙对冲燃烧煤粉锅炉经低氮燃烧技术改造后炉膛水冷壁出现的腐蚀结焦问题,利用ANSYS FLUENT软件对炉膛内的燃烧状况进行了数值模拟研究。结果表明:水冷壁附近的还原性气体(CO+H_2S)的体积分数过高,约20.85%,是造成腐蚀、结焦问题的主要原因;分配调整燃尽风(OFA)风量和低氮燃烧器二次风风量,不能降低水冷壁附近还原性气体的体积分数;在保证现有运行工况不变的情况下,额外增加贴壁风口,贴壁风量为18.67 kg/s,在原腐蚀、结焦区附近形成空气保护层,能够有效地降低水冷壁附近还原性气体的体积分数至7.83%,从而有效地解决炉膛水冷壁的腐蚀、结焦问题。
In order to investigate the problem of serious corrosion and coking of water wall of a 350 MW opposite firing boiler transformed with new low NO_x burners,numerical simulation with ANSYS Fluent was employed to study the combustion process inside the boiler.The simulation shows that the reductive environment(CO+H_2S) is the main reason for corrosion and coking,and the concentration of the reductive gas is about 20.85% for the volume fraction.Fine tune of the over fire air flow and secondary air flow of the low NO_x burner cannot decrease the concentration of the reductive gases near the water wall.Installing air inlet close to the wall can introduce addition air flow on the surface of the water wall,approximately 18.67 kg/s,which effectively decreases the concentration of the reductive gases to 7.83% for the volume fraction and eventually reduces the corrosion and coking of the water wall.
In order to investigate the problem of serious corrosion and coking of water wall of a 350 MW opposite firing boiler transformed with new low NO_x burners,numerical simulation with ANSYS Fluent was employed to study the combustion process inside the boiler.The simulation shows that the reductive environment(CO+H_2S) is the main reason for corrosion and coking,and the concentration of the reductive gas is about 20.85% for the volume fraction.Fine tune of the over fire air flow and secondary air flow of the low NO_x burner cannot decrease the concentration of the reductive gases near the water wall.Installing air inlet close to the wall can introduce addition air flow on the surface of the water wall,approximately 18.67 kg/s,which effectively decreases the concentration of the reductive gases to 7.83% for the volume fraction and eventually reduces the corrosion and coking of the water wall.
引文
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[2] 杨建成,吴江全,胡亚民,等.高燃料氮烟煤空气分级燃烧氮氧化物排放特性实验研究[J].热能动力工程,2015,30(1):101-107,167-168.YANG Jian-cheng,WU Jiang-quan,HU Ya-min,et al.Experimental study of the nitrogen oxide emissions characteristics of a bituminous coal with a high fuel nitrogen content under the condition of the air staged combustion [J].Journal of Engineering for Thermal Energy and Power,2015,30(1):101-107,167-168.
[3] LING Zhong-qian,LING Bo,KUANG Min,et al.Comparison of airflow,coal combustion,NOx emissions,and slagging characteristics among three large-scale MBEL down-fired boilers manufactured at different times[J].Applied Energy,2017,187:689-705.
[4] 丘纪华,李敏,孙学信,等.对冲燃烧布置锅炉水冷壁高温腐蚀问题的研究[J].华中理工大学学报,1999(1):64-66,78.QIU Ji-hua,LI Min,SUN Xue-xin,et al.The Corrosion of water-wall in wall fired Boiler[J].Huazhong Univ.of Sci.& Tech,1999(1):64-66,78.
[5] SANCHEZ J,BAKKER W,FACCHIANO A,et al.Numerical modeling of waterwall wastage on an advanced low NOx PC fired boiler[R].1004739,Palo Alto,CA:EPRI,2004.
[6] 魏道君.1 000 MW锅炉侧墙水冷壁防止高温腐蚀解决方案研究[J].华电技术,2016,38(2):1-5,77.WEI Dao-jun.Solution study of 1 000 MW boiler side water wall high-temperature corrosion[J].Huadian Technology,2016,38(2):1-5,77.
[7] MOORES.Waterwall fireside corrosion under low-NOx burner conditions[R].1001351,Palo Alto,CA:EPRI,2001.
[8] 陈大为.哈锅670 t/h锅炉结焦的数值模拟和试验研究[D].吉林:东北电力大学,2008.CHEN Da-wei.Number simulation and test research for coke agglomeration of the HG 670 t/h power plant boiler[D].Jilin:Northeast Dianli University,2008.
[9] 毛晓飞,江卫国,万中平,等.330 MW贫煤锅炉结焦原因分析及治理[J].电站系统工程,2016,32(4):16-20.MAO Xiao-fei,JIANG Wei-guo,WAN Zhong-ping,et al.Reason analysis and treatment measure of slagging on a 330 MW meager coal boiler[J].Power System Engineering,2016,32(4):16-20.
[10] 华永明,周强泰,丁昭,等.1 025 t/h直流锅炉水冷壁壁温特性理论研究[J].锅炉技术,1999(1):8-13.HUA Yong-ming,ZHOU Qiang-tai,DING Zhao,et al.Theoreticalresearch on characteristics of waterwall metal temperature of 1 025 t/h once-through boiler[J].Boiler Technology,1999(1):8-13.
[11] 李鹏飞,徐敏义,王飞飞.精通CFD工程仿真与案例分析实战[M].北京:人民邮电出版社,2011.LI Peng-fei,XU Min-yi,WANG Fei-fei.Proficient in CFD:FLUENT GAMBIT ICEM CFD tecplot[M].Beijing:Posts & Telecom Press,2011.
[12] R VUTHALURU,VUTHALURU H B.Modelling of a wall fired furnace for different operating conditions using FLUENT[J].Fuel Processing Technology,2006,87(7):633-639.
[13] 王雪彩,孙树翁,李明,等.600 MW墙式对冲锅炉低氮燃烧技术改造的数值模拟[J].中国电机工程报,2015,35(7):1689-1696.WANG Xue-cai,SUN Shu-weng,LI Ming,et al.Numerical simulation on low NOx combustion technological transformation of a 600 MW boiler with opposed wall swirling burners[J].Proceeding of the CSEE,2015,35(7):1689-1696.
[14] 林鹏云,罗永浩,胡瓅元.燃煤电站锅炉NOx排放影响因素的数值模拟分析[J].热能动力工程,2007(5):529-533,579.LIN Peng-yun,LUO Yong-hao,HU Li-yuan.Numerical simulation and analysis of the influencing factors of NOx emissions of coal-fired utility boilers[J].Journal of Engineering for Thermal Energy and Power,2007(5):529-533,579.
[15] 蒋翀,徐宪斌,冷杰.华能丹东电厂低NOx分级燃烧系统[J].东北电力技术,2000(11):1-4.JIANG Chong,XU Xian-bin,LENG Jie.Low NOx staged combustion system of Huaneng Dandong Power Plant[J].Northeast Electric Power Technology,2000(11):1-4.