对冲燃烧锅炉防高温腐蚀改造数值研究
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摘要
针对某660 MW前后墙对冲燃烧锅炉侧墙出现的严重高温腐蚀现象,通过对侧墙近壁烟气成分进行分析,认为侧墙附近强还原性气氛和煤粉刷墙是导致侧墙高温腐蚀的主要原因。提出在前后墙布置贴壁风方案,采用数值模拟的方法,研究贴壁风对侧墙贴壁流场、组分浓度和炉内燃烧过程的影响。模拟结果表明:贴壁风覆盖在侧墙表面形成气膜,减轻了煤粉对侧墙的冲刷;添加贴壁风后,中层燃烧器至上层燃尽风侧墙大部分区域内O2体积分数维持在2%以上, CO体积分数控制在3%以内,还原性气氛得到有效改善;贴壁风的加入对炉膛中间区域燃烧过程影响较小,但在一定程度上降低了侧墙烟气温度,进一步抑制了高温腐蚀的产生。
High-temperature corrosion occurred on the sidewalls of a 660 MW opposite wall firing boiler. The measurement of near-wall gas components revealed that the strong reducing atmosphere near the sidewalls and the scouring of pulverized-coal on the sidewalls are the main causes. A retrofit scheme, in which near-wall air nozzles were arranged on the front and rear walls, was proposed. Numerical simulation was conducted to understand the effect of near-wall air on the flow field, components concentration in the near-wall region and combustion process in the furnace. The simulation results indicated that near-wall air forms gaseous film covering the surface of sidewalls, which relieves the scouring of pulverized-coal on the sidewalls. With the nearwall air nozzles, the mole fraction of O2 is kept over 2% and the mole fraction of CO is controlled below 3%in the most areas of sidewalls between the heights of middle layers of burners and upper layers of over-fire-air.Thus, the near-wall reducing atmosphere is significantly improved. The addition of near-wall air has negligible influence on the combustion in the center part of the furnace. It reduces the gas temperature in the sidewall region and restrains the formation of high-temperature corrosion.
High-temperature corrosion occurred on the sidewalls of a 660 MW opposite wall firing boiler. The measurement of near-wall gas components revealed that the strong reducing atmosphere near the sidewalls and the scouring of pulverized-coal on the sidewalls are the main causes. A retrofit scheme, in which near-wall air nozzles were arranged on the front and rear walls, was proposed. Numerical simulation was conducted to understand the effect of near-wall air on the flow field, components concentration in the near-wall region and combustion process in the furnace. The simulation results indicated that near-wall air forms gaseous film covering the surface of sidewalls, which relieves the scouring of pulverized-coal on the sidewalls. With the nearwall air nozzles, the mole fraction of O2 is kept over 2% and the mole fraction of CO is controlled below 3%in the most areas of sidewalls between the heights of middle layers of burners and upper layers of over-fire-air.Thus, the near-wall reducing atmosphere is significantly improved. The addition of near-wall air has negligible influence on the combustion in the center part of the furnace. It reduces the gas temperature in the sidewall region and restrains the formation of high-temperature corrosion.
引文
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[11]刘博,郑文广,朱良松.1 000 MW超超临界锅炉防治高温腐蚀技术改造[J].电站系统工程,2015,31(4):29-31.
[12]许涛,李敏,李春曦.对冲燃烧锅炉水冷壁高温腐蚀分析及防治[J].热力发电,2015,44(8):104-108.
[13]姚露,陈天杰,刘建民,等.组合式贴壁风对660 MW锅炉燃烧过程的影响[J].东南大学学报(自然科学版),2015,45(1):85-90.
[14]孟凡冉,高畅,金保昇,等.异距贴壁风喷口布置方案的数值模拟[J].化工进展,2017,36(9):3237-3242.
[15]YANG W,YOU R,WANG Z,et al.Effect of near-wall air application in a pulverized-coal 300 MWe utility boiler on combustion and corrosive gases[J].Energy&Fuels,2017(31):10075-10081.
[16]柳宏刚,张广才,王志刚,等.墙式对冲燃烧锅炉高温腐蚀原因分析与治理[J].热力发电,2013,42(12):129-131.
[17]LIU H,LIU Y,NIE L,et al.Effect of air staging conditions on the combustion and NOXemission characteristics in a600 MW wall fired utility boiler using lean coal[J].Energy&Fuels,2013(27):5831-5840.
[18]ZHOU H,YANG Y,DONG K,et al.Influence of the gas particle characteristics of a low-NOXswirl burner on the formation of high temperature corrosion[J].Fuel,2014(134):595-602.
[2]陈天杰,姚露,刘建民,等.某660 MW前后墙对冲燃煤锅炉贴壁风优化方案的数值模拟[J].中国电机工程学报,2015,35(20):5265-5271.
[3]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,1999,27(1):63-65.
[4]李敏,丘纪华,向军,等.锅炉水冷壁高温腐蚀运行工况[J].中国电机工程学报,2002,22(7):150-154.
[5]陈敏生,廖晓春.600 MW超临界锅炉防止高温腐蚀技术改造和运行调整[J].中国电力,2014,47(4):56-59.
[6]陈敏生,廖晓春,楼杰.对冲燃烧锅炉水冷壁高温腐蚀问题的探讨[J].电站系统工程,2013,29(5):33-34.
[7]李春曦,许涛,李敏,等.对冲燃烧锅炉防高温硫腐蚀改造的数值研究[J].动力工程学报,2016,36(11):853-861.
[8]梁学斌,孙军,蒙毅,等.非对称高速贴壁风系统在530MW俄制机组上的应用[J].热力发电,2017,46(3):87-92.
[9]杜智华,蒙毅,孙军.530 MW超临界机组对冲燃烧锅炉低氮燃烧贴壁风系统数值计算[J].动力工程学报,2017,37(6):425-431.
[10]陈敏生,廖晓春.改造燃烧系统降低对冲燃烧锅炉侧墙还原性气氛[J].中国电力,2014,47(1):91-95.
[11]刘博,郑文广,朱良松.1 000 MW超超临界锅炉防治高温腐蚀技术改造[J].电站系统工程,2015,31(4):29-31.
[12]许涛,李敏,李春曦.对冲燃烧锅炉水冷壁高温腐蚀分析及防治[J].热力发电,2015,44(8):104-108.
[13]姚露,陈天杰,刘建民,等.组合式贴壁风对660 MW锅炉燃烧过程的影响[J].东南大学学报(自然科学版),2015,45(1):85-90.
[14]孟凡冉,高畅,金保昇,等.异距贴壁风喷口布置方案的数值模拟[J].化工进展,2017,36(9):3237-3242.
[15]YANG W,YOU R,WANG Z,et al.Effect of near-wall air application in a pulverized-coal 300 MWe utility boiler on combustion and corrosive gases[J].Energy&Fuels,2017(31):10075-10081.
[16]柳宏刚,张广才,王志刚,等.墙式对冲燃烧锅炉高温腐蚀原因分析与治理[J].热力发电,2013,42(12):129-131.
[17]LIU H,LIU Y,NIE L,et al.Effect of air staging conditions on the combustion and NOXemission characteristics in a600 MW wall fired utility boiler using lean coal[J].Energy&Fuels,2013(27):5831-5840.
[18]ZHOU H,YANG Y,DONG K,et al.Influence of the gas particle characteristics of a low-NOXswirl burner on the formation of high temperature corrosion[J].Fuel,2014(134):595-602.