Passive-Active SCR Aftertreatment for Ammonia-Fueled Engines and NOx Sensing
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Solution Overview
Problem
Conventional SCR systems are inadequate for ammonia fueled internal combustion engines due to high NOx and ammonia emissions, which overwhelm current NOx sensors and prevent accurate measurement and control.
Innovation Solution
An exhaust gas aftertreatment system comprising a passive SCR catalyst system downstream of the engine, utilizing unburned ammonia for NOx reduction, followed by an active SCR system with reductant injection controlled by NOx sensors, ensuring accurate NOx measurement and further reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a conventional SCR system with reductant injection is used, then NOx reduction capability is improved, but the system cannot handle high ammonia emissions from ammonia fueled engines and sensor measurement becomes impossible
Solution Approach 1:
The SCR system is divided into two distinct segments: a passive SCR catalyst section that operates without reductant injection to handle high ammonia emissions, and an active SCR catalyst section with reductant injection for precise NOx control. This segmentation allows each section to specialize in different functions, resolving the contradiction between handling high ammonia emissions and enabling accurate sensor measurement.
Solution Approach 2:
The passive SCR catalyst acts as an intermediary component between the engine exhaust and the active SCR system. It pre-treats the exhaust by utilizing unburned ammonia for NOx reduction, thereby reducing the ammonia concentration to levels that allow conventional NOx sensors to function properly in the active SCR section.
2Loss of substance
If unburned ammonia is utilized for NOx reduction, then reductant injection requirements are reduced, but accurate NOx measurement becomes difficult due to high ammonia concentrations
Solution Approach 1:
The catalyst system is segmented into passive and active sections. The passive section utilizes unburned ammonia for NOx reduction without requiring reductant injection, while the active section creates conditions suitable for accurate NOx sensing by maintaining lower ammonia concentrations through controlled reductant injection.
Solution Approach 2:
The passive SCR catalyst utilizes the unburned ammonia already present in the exhaust gas from the ammonia fueled engine, eliminating the need for external reductant storage and injection infrastructure. This self-service approach reduces system complexity and reductant consumption while the downstream active SCR system ensures measurement accuracy.
3Device complexity
If a single SCR catalyst system is used, then system complexity is reduced, but the system cannot simultaneously handle high ammonia emissions and enable accurate NOx sensing
Solution Approach 1:
The SCR system is divided into two functional sections: passive SCR catalyst and active SCR catalyst with reductant injection. This segmentation enables the system to simultaneously handle high ammonia emissions through the passive section while the active section maintains conditions for accurate NOx sensing and control.
Solution Approach 2:
The combined passive-active SCR system performs multiple functions: the passive section handles high ammonia tolerance and initial NOx reduction, while the active section provides precise NOx control and sensing compatibility. This multi-functionality allows a single integrated system to address both high ammonia emissions and accurate measurement requirements.
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
Enables precise NOx measurement and reduction in ammonia fueled engines, allowing conventional NOx sensors to function effectively and maintaining low ammonia levels for efficient emissions control.
Implementation Method 1
SCR catalysts are used to control the NOx emissions from lean burn combustion engines, mainly Diesel engines, by adding a reducing agent such as urea or ammonia upstream of these catalysts
Implementation Method 2
These catalysts are often used with an ASC (ammonia slippage catalyst) in order to control the ammonia excess slipping from the SCR catalysts
Data Source
AI summary
The present disclosure provides an exhaust gas aftertreatment system for an ammonia fueled internal combustion engine comprising: a passive SCR catalyst system arranged downstream of the engine, the passive SCR catalyst system comprising an SCR catalyst and no reductant injection system, and an active SCR catalyst system arranged downstream of the passive SCR catalyst system, the active SCR catalyst system comprising an SCR catalyst, a first NOx sensor and a reductant injection system, the reductant injection system comprising a reductant injector and a controller controlling reductant injection based on an NOx concentration measured by the first NOx sensor.