Segmented Lean NOx Trap for Cost-Effective Emission Control
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Solution Overview
Problem
Lean NOx traps for reducing nitrogen oxide emissions in lean-burn engines are cost-inefficient due to the need for high amounts of platinum group metals to control NOx, hydrocarbon, and carbon monoxide emissions, and existing solutions do not effectively manage these emissions under increasing regulatory demands.
Innovation Solution
A modular exhaust-gas aftertreatment system with a large-volume lean NOx trap divided into two regions: a high-PGM first region for rapid heating and NOx storage/oxidation, and a low-PGM second region for NOx storage, optimized for cost-effective NOx reduction, where the first region is positioned close to the turbocharger to achieve high temperatures for efficient NOx and hydrocarbon/co conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a large-volume LNT is used to reduce NOx emissions, then NOx reduction effectiveness is improved, but the amount of platinum group metals required increases, leading to higher costs
Solution Approach 1:
The LNT is divided into two distinct regions: a first region with high PGM loading for rapid light-off and oxidation functions, and a second region with low PGM loading for NOx storage. This segmentation allows each region to be optimized for its specific function, reducing the overall PGM requirement while maintaining effective NOx reduction
Solution Approach 2:
Different regions of the LNT are assigned different PGM concentrations based on their specific functional requirements. The first region near the turbocharger outlet has high PGM content to facilitate rapid heating and oxidation, while the second downstream region has low PGM content since it primarily needs NOx storage capacity, not oxidation catalysis
2Object-generated harmful factors
If the LNT volume is increased to meet stricter NOx emission standards, then NOx reduction capacity is improved, but the system cost increases due to higher PGM requirements
Solution Approach 1:
The LNT is divided into two distinct regions: a first region with high PGM loading for rapid light-off and oxidation functions, and a second region with low PGM loading for NOx storage. This segmentation allows each region to be optimized for its specific function, reducing the overall PGM requirement while maintaining effective NOx reduction
Solution Approach 2:
Different regions of the LNT are assigned different PGM concentrations based on their specific functional requirements. The first region near the turbocharger outlet has high PGM content to facilitate rapid heating and oxidation, while the second downstream region has low PGM content since it primarily needs NOx storage capacity, not oxidation catalysis
3Volume of stationary object
If the LNT is positioned far from the turbocharger outlet, then there is more space for NOx storage, but the exhaust gas temperature decreases, reducing the efficiency of NOx storage and HC/CO reduction
Solution Approach 1:
The LNT is divided into two distinct regions: a first region with high PGM loading for rapid light-off and oxidation functions, and a second region with low PGM loading for NOx storage. This segmentation allows each region to be optimized for its specific function, reducing the overall PGM requirement while maintaining effective NOx reduction
Solution Approach 2:
The first region with high PGM loading performs preliminary oxidation of NO to NO2 and combustion of HC/CO before the exhaust gas reaches the second region. This preliminary action ensures that the necessary temperature and chemical conditions are established early in the LNT, enabling effective NOx storage in the second region even though it is positioned downstream
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 configuration reduces NOx emissions efficiently while minimizing platinum group metal usage, achieving cost-effective exhaust-gas aftertreatment by optimizing the distribution of PGMs within the system, allowing for a larger, cost-effective second region for NOx storage and reduction.
Implementation Method 1
storage/reduction of NOx and oxidation of NO to form NO2... in the first region
Implementation Method 2
the first region may comprise a coating with a relatively high proportion of PGM... for oxidation of NO to form NO2
Implementation Method 3
exhaust gas heats up the first region as quickly as possible such that a storage of NOx and oxidation of NO to form NO2 and a reduction of HC and/or CO can take place
Implementation Method 4
Said temperature is usually approximately 170 to 200° C.
Implementation Method 5
the second region may comprise relatively little PGM and a relatively large amount of NOx storage material... for the storage and/or reduction of nitrogen oxides (NOx)
Implementation Method 6
oxidation of NO to form NO2 or else for the reduction of hydrocarbon (HC) and/or carbon monoxide (CO) in the exhaust gas
Implementation Method 7
the first region may comprise a coating with a relatively high proportion of PGM... for reduction of HC and/or CO
Data Source
AI summary
An exhaust-gas aftertreatment system (1) for a motor vehicle having a turbocharged internal combustion engine (2) comprises a large-volume lean NOx trap (5) which is connected by means of a short connecting pipe (4) to an outlet of the turbocharger (3), wherein the lean NOx trap (5) has a first region (6) for the storage and/or reduction of NOx and oxidation of NO to form NO2 and/or reduction of hydrocarbon and/or carbon monoxide in the exhaust gas, and a downstream second region (7) for the storage and/or reduction of nitrogen oxides in the exhaust gas.