天然气锅炉分级柔和燃烧模拟研究
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摘要
燃气锅炉在我国应用广泛,随着煤改气的进行,应用越来越多, NO_x排放标准也越来越严格。降低NO_x的排放有利于减少空气污染。以小型天然气柔和燃烧炉膛为研究对象,通过数值模拟的方法研究燃料分级下的柔和燃烧特性,分析在不同当量比、不同热强度条件下轴向分级对炉膛烟气中NO_x生成的影响。结果表明,给定条件下柔和燃烧分级带来的NO_x减排收益随着二级燃料量的增加而减小,当二级燃料量在15%左右的时候可以最大程度地优化温度场分布,降低燃烧峰值温度,获得比较好的NO_x控制效果。随着当量比和热强度的提高,燃料分级带来的收益也会变大。
The gas-fired boilers are widely used in China. With the progress of coal-to-gas conversion, more and more applications have been made, and NO_x emission standards have become increasingly stringent. Reducing NO_x emissions will play an important role in reducing air pollution.The MILD combustioncharacteristics of a nature gas fired boiler with axial fuel-stagedwere studied by numerical simulations. The effect of the different equivalence ratio and heat release intensity on the NO_x formation in furnace was studied. The results show that MILD combustion with axial fuel-staged can reduce the NO_x formation and the NO_x decreases as the secondary fuel ratio increases under the given conditions. It will make the temperature field more uniform with lower peak temperature and lowerNO_x emissions when the secondary fuel ratio is 15%.As the equivalence ratio and heat intensity increased, the effect on reducing NO_x with fuel staged combustion will be better.
The gas-fired boilers are widely used in China. With the progress of coal-to-gas conversion, more and more applications have been made, and NO_x emission standards have become increasingly stringent. Reducing NO_x emissions will play an important role in reducing air pollution.The MILD combustioncharacteristics of a nature gas fired boiler with axial fuel-stagedwere studied by numerical simulations. The effect of the different equivalence ratio and heat release intensity on the NO_x formation in furnace was studied. The results show that MILD combustion with axial fuel-staged can reduce the NO_x formation and the NO_x decreases as the secondary fuel ratio increases under the given conditions. It will make the temperature field more uniform with lower peak temperature and lowerNO_x emissions when the secondary fuel ratio is 15%.As the equivalence ratio and heat intensity increased, the effect on reducing NO_x with fuel staged combustion will be better.
引文
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[3] 李灿,唐文武,梁卫民,等.高温空气燃烧技术在我国的应用现状与发展前景 [J].冶金能源,2003,22(2):41-46.LI Can,TANG Wen-wu,LIANG Wei-min,et al.Application and prediction of high temperature air combustion in our country [J].Energy for Metallurgical Industry,2003,22(2):41-46.(in Chinese)
[4] WüNNING J A,WüNNING J G.Flameless oxidation to reduce thermal no-formation [J].Progress in Energy and Combustion Science,1997,23(1):81-94.
[5] SMREKAR J,POTO■,SENEGA■ prediction of NOx emissions for a coal-based boiler [J].Applied Energy,2013,106:89-99.
[6] MI J,LI P,ZHENG C.Impact of injection conditions on flame characteristics from a parallel multi-jet burner [J].Energy,2011,36(11):6583-95.
[7] LI Y H,CHEN G B,LIN Y C,et al.Effects of flue gas recirculation on the premixed oxy-methane flames in atmospheric condition [J].Energy,2015,89:845-857.
[8] 王宝源.常温空气无焰燃气锅炉的强化换热和污染物减排研究 [D].合肥:中国科学技术大学,2010.WANG Bao-yuan.Heat Transter Enhancement and Pollutant Control in Gas-fired Boiler Using Normal Temperature Air Flameless Canbustion Technology [D].Hefei:University of Science and Technology of China,2010.(in Chinese)
[9] HUANG M,ZHANG Z,SHAO W,et al.Comparative study of syngas mild combustion characteristics in swirl diffusion and coflow diffusion staged combustor [C].Proceedings of the ASME Turbo Expo 2013:Turbine Technical Conference and Exposition.San Antonio,TX:ASME,2013.
[10] CHRISTO F C,DALLY B B.Modeling turbulent reacting jets issuing into a hot and diluted coflow [J].Combustion and Flame,2005,142(1-2):117-129.
[11] GALLETTI C,PARENTE A,TOGNOTTI L.Numerical and experimental investigation of a mild combustion burner [J].Combustion and Flame,2007,151(4):649-664.
[12] PARENTE A,GALLETTI C,TOGNOTTI L.Effect of the combustion model and kinetic mechanism on the MILD combustion in an industrial burner fed with hydrogen enriched fuels [J].International Journal of Hydrogen Energy,2008,33(24):7553-7564.
[13] CAVALIERE A,De JOANNON M.Mild combustion [J].Progress in Energy and Combustion Science,2004,30(4):329-366.
[14] ROTTIER C,LACOUR C,GODARD G,et al.On the effect of air temperature on mild flameless combustion regime of high temperature furnace [C].Proceeding of the European Combustion Meeting.Vienna,Austria:ECM,2009.
[15] DENG X,XIONG Y,YIN H,et al.Numerical study of the effect of nozzle configurations on characteristics of MILD combustion for gas turbine application [J].Journal of Energy Resources Technology,Transactions of the ASME,2016,138(4):042212.