基于CFD模拟的大差异流量烧结烟气与臭氧混合特性研究
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摘要
烧结烟气臭氧氧化工艺可耦合现有脱硫设备实现对NO_x和Hg等污染物的一体化脱除,其中臭氧与烟气的混合效果直接影响到NO_x氧化及其脱除效果。本文针对烧结烟气臭氧氧化脱硝过程中烟气与臭氧大差异流量的特征,采用CFD数值模拟方法考察了烟道内臭氧与烟气的流动及混合特性,分析了射流速度对传递过程的影响,基于流场分析提出加装环形构件的优化方案,获得了构件有效宽度与夹角对臭氧浓度分布均匀性与压降的影响规律。结果表明:大差异流量下射流速度对臭氧浓度分布均匀性影响较小;随构件宽度增大,压降增大,臭氧分布均匀性呈现先提高后下降的特征;随构件与烟道夹角增大压降减小,当夹角小于90°臭氧分布均匀性差异较小,当夹角大于90°无量纲高度小于1.75区域混合效果变差。
The ozone oxidation technology of sintering flue gas can be coupled with the existing desulfurization device for integrated removal of pollutants like NO_x and mercury,and the mixing effect of ozone and flue gas plays an important role in both NO_x oxidation and its removal efficiency.In view of the differential flow rate characteristics of flue gas and ozone during denitrification process of sintering flue gas and ozone oxidation denitrification process,the Computational Fluid Dynamic(CFD)simulation method is employed to explore the aerodynamics and mixing behaviors of sintering flue gas and ozone,and the effect of injection velocity on the transfer behavior is discussed.The optimization scheme of adding annular member is proposed based on the flow field analysis,and the law of influence of effective width and included angle of the member on even distribution and pressure drop of the ozone concentration is obtained.The simulation results indicate that,the high differential flow downward injection velocity has little influence on the uniformity of ozone distribution.The pressure drop increases with the increase of member width,and the uniformity of ozone distribution increases firstly and then decreases.However,the pressure drop decreases with the increase of the included angle between the member and the main duct,and when the included angle is less than 90°,there is little difference in the homogeneity of ozone distribution.When the included angle is more than 90°,the mixing effect becomes worse in the region with a dimensionless height less than 1.75.
The ozone oxidation technology of sintering flue gas can be coupled with the existing desulfurization device for integrated removal of pollutants like NO_x and mercury,and the mixing effect of ozone and flue gas plays an important role in both NO_x oxidation and its removal efficiency.In view of the differential flow rate characteristics of flue gas and ozone during denitrification process of sintering flue gas and ozone oxidation denitrification process,the Computational Fluid Dynamic(CFD)simulation method is employed to explore the aerodynamics and mixing behaviors of sintering flue gas and ozone,and the effect of injection velocity on the transfer behavior is discussed.The optimization scheme of adding annular member is proposed based on the flow field analysis,and the law of influence of effective width and included angle of the member on even distribution and pressure drop of the ozone concentration is obtained.The simulation results indicate that,the high differential flow downward injection velocity has little influence on the uniformity of ozone distribution.The pressure drop increases with the increase of member width,and the uniformity of ozone distribution increases firstly and then decreases.However,the pressure drop decreases with the increase of the included angle between the member and the main duct,and when the included angle is less than 90°,there is little difference in the homogeneity of ozone distribution.When the included angle is more than 90°,the mixing effect becomes worse in the region with a dimensionless height less than 1.75.
引文
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[11] Lang E,Drtina P,Streiff F,et al.Numerical simulation of the fluid flow and the mixing process in a static mixer[J]. International Journal of Heat & Mass Transfer,1995,38(12):2239-2250.
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[13] Barrué H,Karoui A,Sauze N L,et al.Comparison of aero-dynamics and mixing mechanisms of three mixers:OxynatorTM gas-gas mixer,KMA and SMI static mixers[J]. Chemical Engineering Journal,2001,84(3):343-354.
[14] 梁思超,张晓东,康顺,等.方体绕流的DES模拟及其旋涡结构分析[J].工程热物理学报,2015(3):535-540.
[2] 纪光辉.烧结烟气超低排放技术应用及展望[J].烧结球团,2018(2):59-63.
[3] 梁杰群,潘建,朱德庆,等.某钢铁厂烧结烟气氨法脱硫工艺脱硝效果的评估[J].烧结球团,2016,41(3):52-56.
[4] 王智化,周俊虎,魏林生,等.用臭氧氧化技术同时脱除锅炉烟气中NOx及SO2的试验研究[J].中国电机工程学报,2007,27(11):1-5.
[5] 李和平,吴胜利,韩加友.“臭氧氧化+循环流化床”法烧结烟气净化技术的应用[J].烧结球团,2018,43(6):1-6+18.
[6] 庄卓楷.基于数值模拟的NO臭氧氧化反应、双旋流气气混合器和湿法脱硝模型研究[D].杭州:浙江大学,2015.
[7] Mok Y S,Lee H J.Removal of sulfur dioxide and nitrogen oxides by using ozone injection and absorption–reduction technique[J].Fuel Processing Technology,2006,87(7):591-597.
[8] 王智化,周俊虎,温正城,等.利用臭氧同时脱硫脱硝过程中NO的氧化机理研究[J].浙江大学学报(工学版),2007,41(5):765-769.
[9] Sun C, Zhao N, Zhuang Z, et al. Mechanisms and reaction pathways for simultaneous oxidation of NOx and SO2 by ozone determined by in situ IR measurements[J].Journal of Hazardous Materials,2014,274(12):376-383.
[10] Wang Z, Zhou J, Jianren Fan A, et al. Direct Numerical Simulation of Ozone Injection Technology for NOx Control in Flue Gas[J].Energy & Fuels,2006,20(6):2432-2438.
[11] Lang E,Drtina P,Streiff F,et al.Numerical simulation of the fluid flow and the mixing process in a static mixer[J]. International Journal of Heat & Mass Transfer,1995,38(12):2239-2250.
[12] Myers K J,Bakker A,Ryan D.Avoid agitation by selecting static mixers[J].Chemical Engineering Progress,1997,93(6):28-38.
[13] Barrué H,Karoui A,Sauze N L,et al.Comparison of aero-dynamics and mixing mechanisms of three mixers:OxynatorTM gas-gas mixer,KMA and SMI static mixers[J]. Chemical Engineering Journal,2001,84(3):343-354.
[14] 梁思超,张晓东,康顺,等.方体绕流的DES模拟及其旋涡结构分析[J].工程热物理学报,2015(3):535-540.