Lean NOx Trap Plus Low Temperature Adsorber for Cold Start
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Solution Overview
Problem
Current emission treatment systems for lean-burn engines face challenges in effectively capturing and removing nitrogen oxides (NOx) at low temperatures, particularly during the cold-start period, as existing catalysts like SCR and LNT systems are not sufficiently active below 200°C, and the integration of low-temperature NOx adsorbers with LNTs is complicated by the deactivation of the adsorption capacity during regeneration.
Innovation Solution
The proposed solution involves a configuration where a low-temperature NOx adsorber (LT-NA) is placed downstream of a lean NOx trap (LNT), with the LT-NA being protected from reducing gases by the oxygen-storage function of the LNT, allowing for extended low-temperature trapping and release of NOx emissions as the system reaches higher temperatures, without the need for additional fuel injection devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a low-temperature NOx adsorber (LT-NA) is integrated with a lean NOx trap (LNT) to extend low-temperature trapping range, then NOx adsorption at low temperatures is improved, but the LT-NA becomes deactivated by reducing gases during LNT regeneration
Solution Approach 1:
The system divides the NOx treatment function into two separate components: LNT for high-temperature trapping and regeneration, and LT-NA for low-temperature adsorption. This segmentation allows each component to operate in its optimal temperature range without interfering with the other's function.
Solution Approach 2:
The LNT acts as an intermediary protective layer between the exhaust stream and the LT-NA. During regeneration, the LNT consumes reducing gases through its oxygen storage component, preventing these gases from reaching and deactivating the LT-NA downstream.
2Device complexity
If conventional SCR or LNT systems are used alone, then the system structure is simple, but they fail to effectively capture and remove NOx at low temperatures below 200°C
Solution Approach 1:
The patent combines two different NOx treatment technologies (LNT and LT-NA) into a single integrated system. The LNT handles high-temperature trapping and regeneration, while the LT-NA handles low-temperature adsorption, creating a complementary system that covers the full temperature range.
Solution Approach 2:
The system exploits changes in temperature and chemical composition parameters to activate different functions. At low temperatures, the LT-NA adsorbs NOx; as temperature increases and reducing gases are present, the LNT regenerates and protects the LT-NA; at high temperatures, the LNT actively traps and regenerates NOx.
3Reliability
If additional fuel injection devices are added to protect LT-NA from reducing gases, then LT-NA deactivation is prevented, but device complexity and cost increase
Solution Approach 1:
The LNT's oxygen storage component automatically performs the protective function during regeneration. The system uses its own internal chemistry (oxygen storage and release) to prevent reducing gases from reaching the LT-NA, eliminating the need for external control systems or additional fuel injection devices.
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 enhances NOx adsorption at low temperatures and prevents the deactivation of the LT-NA, ensuring effective NOx capture and release at elevated temperatures, thereby improving the overall efficiency of NOx abatement in lean-burn engine exhaust streams.
Implementation Method 1
the LNT is configured to remove reducing gases present during a rich condition
Implementation Method 2
a low temperature NOx adsorber (LT-NA) comprising a molecular sieve
Implementation Method 3
the LNT is configured to remove reducing gases present during a rich condition
Data Source
AI summary
The present disclosure is directed to an emission treatment system for NOx abatement in an exhaust stream of a lean burn engine. The emission treatment system includes a lean NOx trap (LNT) in fluid communication with and downstream from the lean burn engine and a low-temperature NOx adsorber (LT-NA) in fluid communication with and downstream of the LNT. Further provided is a method for abating NOx in an exhaust stream from a lean burn engine utilizing the disclosed system.