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

To investigate the influences of flow field and species concentration profile on deNOx efficiency and ammonia slip in an industrial SCR reactor, a 3D 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. © 2021 Chin. Soc. for Elec. Eng.