Experimental and Numerical Simulation of Catalyst Deactivation Caused by Transient Turbulence in Gradient Flow Field

In selective catalytic reduction (SCR) deNO X systems, the characteristics of gradient flow field have an important effect on the physical deactivation of catalysts. Through computational fluid dynamics (CFD) simulation, it was found that the relative standard deviation (RSD) coefficients of flow field with characteristic flow velocity were 10.03%, 12.48%, and 14.37% respectively. The uniformity of flow field deteriorated with the increase of flow velocity. Furthermore, the alternating flow field was more likely to scour, wear, and block the catalyst channel, leading to its inactivation. Through large eddy simulation (LES) models, it was found that the alternating flow field generated transient turbulent vortices in the system. The high energy area of flue gas is concentrated in the frequency range of 0.03–10 Hz. Pulsation is mainly caused by turbulent eddies of different scales; the higher the frequency, the faster the energy dissipates. In the low-speed flow field, the flow field at the inlet angle of the flue gas was disordered, and the velocity varied from 2.42 to 8.14 m/s. The transient vortices were triggered by the laminar stripping mechanism near the wall. In the high-speed flow field, the number of turbulent vortices increased sharply, especially on the surface of the first-layer catalyst, which greatly influenced its activity. The shear force of the flue gas jet was the triggering mechanism of turbulent vortices in this condition. Graphical Abstract