面向深度调峰的超临界煤粉锅炉变负荷燃烧三维数值模拟
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摘要
为解决低负荷运行时燃煤锅炉稳燃性下降和NO_x排放增加的问题,对一台660 MW超临界旋流对冲锅炉在低负荷(20%～60%额定负荷)下不同运行工况进行了三维数值模拟,并研究了低负荷下多种操作参数对锅炉稳燃性和污染物排放的影响.计算与分析结果表明:30%额定负荷运行时投运下层燃烧器,且一次风率为0.2、煤粉粒径为50μm时,NO_x排放最少;当负荷进一步降低时锅炉稳燃性迅速下降,同时NO_x排放量迅速增加;调整燃烧器运行方式、一次风率和煤粉粒径可以有效改善锅炉低负荷燃烧状况.在负荷低于30%额定负荷的深度调峰运行时,采用2台磨煤机、下层燃烧器运行,并适当降低一次风率和煤粉粒径可以提高燃煤锅炉的低负荷运行能力.
A 660 MW supercritical swirling opposed boiler was simulated under the low loads(rated loads of 20% to 60%),aiming at solving the problem of decreasing combustion stability and increasing NO_x emission of coal-fired boilers in the low load operation.The effects of operating parameters on the combustion stability and the pollutant emission of the boiler were studied.The simulation and analysis results show that NO_x emission reaches its lowest when the lower burners are put into operation at rated load of 30%, as well as the primary air rate is 0.2 and the particle size of the pulverized coal is 50 μm.When the load is further reduced,the boiler combustion stability decreases rapidly,while the NO_x emission increases significantly.The combustion performance can be improved effectively by adjusting the burner operation mode,primary air rate and pulverized coal particle size.It is suggested that two mills and lower burners should be used when the load rate is less than 30% in deep peak load regulation,and the primary air rate and pulverized coal particle size can be appropriately reduced to improve the operating performance of coal-fired boilers.
A 660 MW supercritical swirling opposed boiler was simulated under the low loads(rated loads of 20% to 60%),aiming at solving the problem of decreasing combustion stability and increasing NO_x emission of coal-fired boilers in the low load operation.The effects of operating parameters on the combustion stability and the pollutant emission of the boiler were studied.The simulation and analysis results show that NO_x emission reaches its lowest when the lower burners are put into operation at rated load of 30%, as well as the primary air rate is 0.2 and the particle size of the pulverized coal is 50 μm.When the load is further reduced,the boiler combustion stability decreases rapidly,while the NO_x emission increases significantly.The combustion performance can be improved effectively by adjusting the burner operation mode,primary air rate and pulverized coal particle size.It is suggested that two mills and lower burners should be used when the load rate is less than 30% in deep peak load regulation,and the primary air rate and pulverized coal particle size can be appropriately reduced to improve the operating performance of coal-fired boilers.
引文
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[2] 张广才,周科,鲁芬,等.燃煤机组深度调峰技术探讨[J].热力发电,2017,46(9):17-23.DOI:10.3969/j.issn.1002-3364.2017.09.017.Zhang G C,Zhou K,Lu F,et al.Discussions on deep peaking technology of coal-fired power plants[J].Thermal Power Generation,2017,46(9):17-23.DOI:10.3969/j.issn.1002-3364.2017.09.017.(in Chinese)
[3] Zheng Y,Gao X T,Sheng C D.Impact of co-firing lean coal on NOx emission of a large-scale pulverized coal-fired utility boiler during partial load operation[J].Korean Journal of Chemical Engineering,2017,34(4):1273-1280.DOI:10.1007/s11814-016-0352-7.
[4] 张广才,周科,柳宏刚,等.某超临界600 MW机组直流锅炉深度调峰实践[J].热力发电,2018,47(5):83-88.DOI:10.19666/j.rlfd.201802020.Zhang G C,Zhou K,Liu H G,et al.Practice of deep peak load regulation for a 600 MW supercritical concurrent boiler[J].Thermal Power Generation,2018,47(5):83-88.DOI:10.19666/j.rlfd.201802020.(in Chinese)
[5] Sun W J,Zhong W Q,Yu A B,et al.Numerical investigation on the flow,combustion,and NOx emission characteristics in a 660 MWe tangential firing ultra-supercritical boiler[J].Advances in Mechanical Engineering,2016,8(2):168781401663072.DOI:10.1177/1687814016630729.
[6] 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.DOI:10.1016/j.fuel.2012.06.091.
[7] Liu Y C,Fan W D,Li Y.Numerical investigation of air-staged combustion emphasizing char gasification and gas temperature deviation in a large-scale,tangentially fired pulverized-coal boiler[J].Applied Energy,2016,177:323-334.DOI:10.1016/j.apenergy.2016.05.135.
[8] Ti S G,Chen Z C,Kuang M,et al.Numerical simulation of the combustion characteristics and NOx emission of a swirl burner:Influence of the structure of the burner outlet[J].Applied Thermal Engineering,2016,104:565-576.DOI:10.1016/j.applthermaleng.2016.05.079.
[9] Yang M,Shen Y Y,Xu H T,et al.Numerical investigation of the nonlinear flow characteristics in an ultra-supercritical utility boiler furnace[J].Applied Thermal Engineering,2015,88:237-247.DOI:10.1016/j.applthermaleng.2014.09.068.
[10] 钟礼今,邓坚,孙伟杰,等.低负荷下燃烧器投运方式对锅炉性能的影响[J].动力工程学报,2015,35(9):693-698.DOI:10.3969/j.issn.1674-7607.2015.09.001.Zhong L J,Deng J,Sun W J,et al.Effects of burner operation mode on performance of the boiler under low load conditions[J].Journal of Chinese Society of Power Engineering,2015,35(9):693-698.DOI:10.3969/j.issn.1674-7607.2015.09.001.(in Chinese)
[11] Zhao S N,Fang Q Y,Yin C G,et al.New fuel air control strategy for reducing NOx emissions from corner-fired utility boilers at medium-low loads[J].Energy & Fuels,2017,31(7):6689-6699.DOI:10.1021/acs.energyfuels.7b00337.
[12] Zeng L D,Fu Z G,Qi W J,et al.Optimal simulation on the variable oxygen for an ultra-supercritical utility boiler[C]//2012 Asia-Pacific Power and Energy Engineering Conference.Shanghai,China.New York,USA:IEEE,2012:1-4.DOI:10.1109/APPEEC.2012.6307025.
[13] Zhou H,Yang Y,Liu H Z,et al.Numerical simulation of the combustion characteristics of a low NOx swirl burner:Influence of the primary air pipe[J].Fuel,2014,130:168-176.DOI:10.1016/j.fuel.2014.04.028.
[14] Zhang X H,Zhou J,Sun S Z,et al.Numerical investigation of low NOx combustion strategies in tangentially-fired coal boilers[J].Fuel,2015,142:215-221.DOI:10.1016/j.fuel.2014.11.026.