PNNL

Abstract

A commercial SCR-filter, deployed in the United States in 2015, was sectioned and examined using techniques including mercury porosimetry, electron microscopy, and micro X-Ray computed tomography. Three distinct regions were observed with respect to catalyst loading and location. The first 15 to 21% of effective filter length near the inlet end of the filter was relatively lightly coated. Most of the catalyst present in this region was observed inside the porous filter walls, and the catalyst concentration was generally greater near the upstream filter wall surfaces. The next 14 to 20% of the effective filter length was more heavily coated, with catalyst present throughout the thickness of the porous filter walls, as well as coatings on both the upstream and downstream filter wall surfaces. The final region, which accounted for 65 to 70% of the filter length near the outlet end, had an intermediate catalyst loading. Most of the catalyst here was again observed inside the porous filter wall. Concentrations in this region were higher near the outlet filter wall surfaces. Detailed models of multi-functional aftertreatment devices such as this have included representations of catalyst distribution within the filter bricks. Catalyst distribution may have an impact on flow distribution, soot loading patterns, local concentrations, and ultimately pressure drop and conversion efficiency.