Wall-Flow Filter With Segmented Catalyst Channels
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Solution Overview
Problem
Conventional wall-flow filters face challenges in achieving high gas flow, mechanical stability, and efficient catalytic activity while maintaining a compact design, with complex production methods and limited porosity control.
Innovation Solution
The wall-flow filter design includes catalyst channels closed at both ends with common walls to the inlet and outlet channels, allowing high gas flow and efficient catalysis, using solid catalysts distributed within the channels rather than coatings, and allowing for varying catalyst materials and quantities without complex porosity adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If catalytic coatings with defined porosity are applied to porous walls, then catalytic activity is improved, but the coating thickness must be limited to avoid excessive back-pressure
Solution Approach 1:
The filter structure is segmented into separate catalyst channels with closed ends, distinct from the exhaust gas channels. This segmentation allows the catalyst to be contained in dedicated spaces without coating the entire porous wall, thereby maintaining high catalytic activity while preserving gas flow through the uncoated or lightly coated walls.
Solution Approach 2:
The catalytic function is extracted from the wall coating and transferred to separate catalyst channels. By removing the catalyst from the coating layer and placing it in dedicated channels, the patent eliminates the conflict between coating thickness for catalytic activity and back-pressure for gas flow.
2Reliability
If coating thickness is increased to provide more catalytically active material, then catalytic activity is improved, but back-pressure increases and gas flow decreases
Solution Approach 1:
The catalytic function is segmented into separate channels rather than being distributed as a coating. This allows the catalyst to be concentrated in specific areas (catalyst channels) without increasing the overall pressure drop across the filter, as the exhaust gas can flow freely through the remaining open channels.
3Reliability
If filter size is enlarged to compensate for limited catalytic material, then catalytic activity is improved, but the filter becomes less compact and heavier
Solution Approach 1:
The catalyst is concentrated in specific local areas (catalyst channels) rather than being distributed throughout the entire filter structure. This local concentration allows high catalytic activity to be achieved in a compact volume, as the catalyst is placed only where needed rather than coating the entire surface.
4Productivity
If porosity of channel walls is increased to improve gas flow, then gas flow is improved, but soot filtering efficiency and mechanical stability decrease
Solution Approach 1:
The filter structure separates the gas flow function (exhaust gas channels with high porosity) from the catalytic function (catalyst channels with closed ends). This allows the exhaust gas channels to have high porosity for good gas flow, while the catalyst channels provide filtration and catalytic activity through their closed-end structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enables high catalytic activity, mechanical stability, and efficient gas flow in a compact format, simplifying production by eliminating the need for precise porosity control and allowing for flexible catalyst use, resulting in improved filtration and reduced weight and volume.
Implementation Method 1
The catalysts serve in particular for the depletion of undesired gaseous exhaust gas components, such as nitrogen oxides (NOx), CO, hydrocarbons or H2S. Comparatively harmless products are obtained thereby, such as H2O, CO2 or N2.
Implementation Method 2
The solid components, in particular the soot particles, are filtered by the porous walls. In the case of surface filters, the particles collect mainly on the surface of the filter wall or, in the case of depth filtration, accumulate in the interior of the filter wall.
Implementation Method 3
the inlet channels and the catalyst channels have common walls and the outlet channels and the catalyst channels likewise have common walls. The latter are closed at both ends, that is at the front end (exhaust gas inlet end) and at the back end (exhaust gas outlet end). As a result, the catalyst is enclosed in the catalyst channels.
Data Source
AI summary
The invention relates to a wall-flow filter for cleaning exhaust gases from engines, with parallel exhaust gas inlet channels and exhaust gas outlet channels which are closed at alternate ends, said filter additionally comprising catalyst channels which are closed at both ends and contain a catalyst in solid form. The invention also relates to production methods and uses of the filter for cleaning exhaust gases, particularly from diesel engines.