Experimental and numerical simulation of catalyst deactivation caused by transient turbulence in gradient flow field

Abstract

Abstract In SCR system, the velocity of flue gas field varies with the load, forming a gradient flow field. The characteristics of gradient flow field have important influence on the physical deactivation of catalyst. Through CFD simulation in this paper, it was found that the relative standard 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, and the alternating flow field was more likely to scour, wear and block the catalyst channel, leading to its inactivation. This conclusion is also confirmed by the test data obtained from the measuring points installed in various parts of the system. Through LES simulation, it is found that alternating flow field will generate transient turbulent vortices in the system, and with the increase of velocity, the number and distribution range of transient turbulent vortices increase rapidly. In the low-speed flow field, the flow field at the inlet Angle of the flue is disordered, and the velocity varies from 2.42m /s to 8.14m /s. At the corner of flue gas outlet, the flow velocity also varies between 4.86 m/s and 9.03 m/s, but there is laminar flow near the wall. The transient vortices are triggered by the laminar stripping mechanism near the wall. In high velocity flow field, the number of turbulent vortices increases sharply, especially on the surface of the first layer catalyst, which has a great influence on its activity. The triggering mechanism of turbulent vortices also changes. At this time, with the increase of the shear force of the flue gas jet, the turbulent vortex is mainly triggered in the shear jet.