660MW燃煤电厂SCR脱硝系统CFD模拟优化研究

CFD Simulation and Optimization of SCR DeNO System in a 660MW Coal-fired Power Plant

为探究流场和组分浓度分布对SCR装置脱硝效率和氨逃逸的影响进而提升脱硝性能,基于ANSYS FLUENT软件平台、耦合多孔介质模型和E-R脱硝反应动力学模型,建立国内某660 MW燃煤机组SCR系统的三维计算流体力学模型;详细分析不同负荷下烟气速度分布、组分浓度分布、脱硝效率和氨逃逸等流动反应特性;进而针对分区喷氨和静态混合器对脱硝性能的影响进行模拟与优化。结果表明:当顶部导流板倾角与楔形弯头倾角相同时,流场分离现象消失,速度分布更加均匀。较之于均匀喷氨方式,分区喷氨可使NH3浓度均匀性提高55%、出口NO浓度偏差降低50%。采用平板型混合器结合分区喷氨策略,催化剂入口截面NH3浓度偏差系数小于2.5%,出口截面NO浓度偏差系数小于8%,局部最大氨逃逸为1.82mg/m3,脱硝效率提高了7%,实现SCR装置的稳定高效运行。

To investigate the influences of flow field and species concentration profile on deNOx efficiency and ammonia slip in an industrial SCR reactor, a 3 D computational fluid dynamics model was established based on ANSYS FLUENT software coupled with porous medium model and E-R deNOx reaction kinetics. The velocity profile, species concentration profile, deNOx efficiency and ammonia slip at various boiler loads were analyzed numerically, the zonal ammonia spraying strategy was simulated, and the static mixer was optimized. Simulation results show that as the inclination angle of deflector is same as that of the top wedge elbow, the undesirable flow separation disappears, and the gas velocity becomes more uniform. Compared with the uniform ammonia-injection scheme, the zonal ammonia spraying strategy could increase the uniformity of NH3 concentration by 55% while decrease the deviation of NO concentration by 50%. Combining the flat-plate mixer with the zonal ammonia injection scheme, the deviation coefficient of NH3 concentration at the inlet of catalyst layer is below 2.5%, the deviation coefficient of NO concentration at the SCR outlet is less than 8%, and the maximum ammonia slip could be reduced to 1.82 mg/m3. In addition, the whole deNOx efficiency is improved by 7%, and stable and efficient operation are achieved in the SCR deNOx system.