Ammonia Barrier Catalyst for SCR Ammonia Slip Control
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Solution Overview
Problem
The existing exhaust systems for internal combustion engines face challenges in efficiently adjusting the ammonia loading of the second SCR catalytic converter, leading to potential nitrogen oxide breakthroughs and ammonia slip, especially under dynamic operating conditions, due to inaccurate ammonia level regulation and cross-sensitivity issues with nitrogen oxide sensors.
Innovation Solution
Incorporating an ammonia barrier catalytic converter upstream of the second SCR catalytic converter, which converts ammonia to nitrogen oxides at higher temperatures, allowing for targeted adjustment of the ammonia loading by increasing the reducing agent intake when a predetermined temperature threshold is exceeded, thereby reducing ammonia slip and improving regulation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the quantity of reducing agent introduced into the exhaust gas by the first metering device is increased when the temperature threshold is exceeded, then the ammonia loading of the second SCR catalytic converter is reduced, but the risk of nitrogen oxide breakthroughs increases
Solution Approach 1:
The ammonia barrier catalytic converter acts as an intermediary component between the first SCR catalytic converter and the second SCR catalytic converter. It selectively converts excess ammonia to nitrogen oxides through oxidation, thereby regulating the ammonia loading of the second SCR catalytic converter without directly affecting the nitrogen oxide conversion reliability in the first SCR catalytic converter.
Solution Approach 2:
The system changes the chemical composition parameter of the exhaust gas by oxidizing ammonia to nitrogen oxides in the ammonia barrier catalytic converter. This parameter change allows precise control of the ammonia loading in the second SCR catalytic converter while maintaining reliable nitrogen oxide conversion in the first SCR catalytic converter.
2Object-generated harmful factors
If the ammonia barrier catalytic converter is used to oxidize ammonia, then the ammonia slip is reduced, but the complexity of the exhaust system increases
Solution Approach 1:
The ammonia barrier catalytic converter is merged with the existing SCR system architecture, integrating the ammonia oxidation function into the exhaust gas treatment chain. This combination approach reduces ammonia slip while maintaining a structured and organized exhaust system without excessive complexity.
Solution Approach 2:
The ammonia barrier catalytic converter serves multiple functions: it oxidizes ammonia to prevent ammonia slip, regulates the ammonia loading of the second SCR catalytic converter, and maintains reliable nitrogen oxide conversion. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in system complexity.
3Quantity of substance
If the reducing agent intake is increased to adjust ammonia loading, then the filling level of the second SCR catalytic converter is controlled, but the precision of ammonia level regulation is reduced
Solution Approach 1:
The ammonia barrier catalytic converter serves as a mediator that provides precise control over the ammonia level in the second SCR catalytic converter. By oxidizing a controlled amount of ammonia to nitrogen oxides, it enables accurate regulation of the ammonia filling level without the imprecision associated with direct reducing agent dosing adjustments.
Solution Approach 2:
The system employs feedback control where the ammonia barrier catalytic converter continuously adjusts the ammonia oxidation based on the ammonia loading level in the second SCR catalytic converter. This feedback mechanism enhances the precision of ammonia level regulation by dynamically responding to changes in the system state.
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 solution enables precise control of the ammonia level in the second SCR catalytic converter, reducing the risk of nitrogen oxide breakthroughs and ammonia slip, while maintaining high nitrogen oxide conversion rates across a wide operating range, by using the ammonia barrier catalyst to oxidize ammonia and adjust the filling level independently of the first SCR catalytic converter.
Implementation Method 1
the ammonia barrier catalytic converter, which converts ammonia to nitrogen oxides at higher temperatures
Implementation Method 2
exhaust gas of the internal combustion engine flows through a first selective catalytic reduction (SCR) catalytic converter
Implementation Method 3
a first selective catalytic reduction (SCR) catalytic converter, downstream of which an ammonia barrier catalytic converter is arranged
Data Source
AI summary
A method for operating an exhaust system of an internal combustion engine of a motor vehicle, in which exhaust gas from the internal combustion engine flows through a first SCR catalytic converter, which is followed by an ammonia barrier catalytic converter, and flows through a second SCR catalytic converter which is disposed downstream of the ammonia barrier catalyst, includes introducing a reducing agent introduced into the exhaust gas by a first metering device upstream of the first SCR catalytic converter and by a second metering device upstream of the second SCR catalytic converter. When a predetermined threshold value of a temperature of a region of the exhaust system is exceeded, a quantity of reducing agent introduced into the exhaust gas by the first metering device is increased.