基于CFD模拟的大差异流量烧结烟气与臭氧混合特性研究

Study on mixing behavior of sintering flue gas and ozone with high differential flow based on CFD simulation

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.