Patent ID: 7862640
Filing Date: 2011-01-04
Classification: B01D,F01N

Abstract:
1. A system for treating diesel exhaust, the system comprising: a first filter including a first substrate having layers of filtration material positioned between layers of corrugated metallic foil, the corrugated metallic foil defining a honeycomb arrangement of longitudinal passageways that extend from an upstream end to a downstream end of the first substrate, the corrugated metallic foil defining openings for allowing exhaust to pass between adjacent longitudinal passageways of the corrugated metallic foil, the filtration material being positioned such that exhaust passing between the adjacent longitudinal passageways passes through the filtration material, the corrugated metallic foil also including flow diverting structures positioned to divert exhaust flow within the longitudinal passageways through the openings; and a second filter positioned downstream from the first filter, the second filter including a second substrate defining a honeycomb arrangement of longitudinal passageways that extend from an upstream end to a downstream end of the second substrate, the longitudinal passages being selectively plugged adjacent upstream and downstream ends of the second substrate such that exhaust flow is forced to flow radially through walls between the longitudinal passages of the second substrate; wherein the first filter is loaded with a precious metal catalyst for catalyzing the conversion of NO to NO wherein the first filter is capable of filtering hard carbon from the diesel exhaust and the particulate mass reduction efficiency of the first filter in the range of 15-50 percent; wherein the second filter has a particulate mass reduction efficiency greater than 75 percent; wherein the first and second filters are relatively sized such that in use the space velocity of the first filter is 3-5 times the space velocity of the second filter; wherein the second filter is loaded with a precious metal catalyst and has an overall lower precious metal loading than the first filter; and; wherein the particulate mass reduction efficiency of the first filter and the precious metal catalyst loading of the first filter are balanced such that a ratio of NO