Exhaust Dosing Control for SCR Catalyst Aging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The aging of selective catalytic reduction (SCR) catalysts in internal combustion engines leads to reduced ammonia storage capacity, resulting in increased nitrogen oxides (NOx) emissions and ammonia slip, as existing technologies lack effective control systems to adjust reductant dosing in response to catalyst degradation.
Innovation Solution
A dosing control system that includes NOx sensors upstream and downstream of the SCR apparatus, a reductant tank, and a control module to adjust the dosing of the reductant solution based on the NOx conversion efficiency, reducing the reductant injection as the catalyst ages, thereby maintaining optimal NOx conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the catalyst of the SCR apparatus is used over time, then the SCR apparatus performs NOx conversion function, but the catalyst ages and ammonia storage capacity reduces
Solution Approach 1:
The control module continuously monitors NOx emissions using upstream and downstream NOx sensors to detect changes in SCR apparatus performance. When conversion efficiency drops below a threshold, the system automatically adjusts reductant dosing to compensate for catalyst aging, creating a closed-loop feedback system that maintains reliable NOx conversion throughout the catalyst's service life.
Solution Approach 2:
The system dynamically adjusts the reductant dosing rate based on real-time monitoring of SCR apparatus performance. The control module modifies the dosing strategy from a fixed original dosing level to a variable adjusted dosing level, allowing the system to adapt to changing catalyst conditions and maintain optimal operation throughout the catalyst's lifespan.
2Duration of action of stationary object
If the catalyst ages with reduced ammonia storage capacity, then the SCR apparatus continues to operate, but tailpipe NOx emissions increase
Solution Approach 1:
Downstream NOx sensors monitor tailpipe emissions and provide feedback to the control module. When NOx emissions exceed acceptable levels due to catalyst aging, the system adjusts reductant dosing to compensate, ensuring emissions remain controlled throughout the catalyst's operational life.
Solution Approach 2:
The system changes the dosing parameter from a fixed original dosing level to a dynamically adjusted dosing level based on catalyst performance. This parameter adjustment compensates for catalyst aging effects and maintains effective NOx conversion throughout the catalyst's operational duration.
3Duration of action of stationary object
If the catalyst ages with reduced ammonia storage capacity, then the SCR apparatus continues to operate, but ammonia slip occurs and increases with degradation
Solution Approach 1:
The control module uses feedback from upstream and downstream NOx sensors to detect ammonia slip conditions. When slip is detected, the system adjusts reductant dosing to optimize the balance between NOx conversion and ammonia slip prevention, maintaining acceptable emissions throughout the catalyst's service period.
Solution Approach 2:
The dosing strategy transitions from a static original dosing level to a dynamic adjusted dosing level that responds to real-time catalyst performance. This dynamic adjustment prevents excessive ammonia slip while maintaining effective NOx conversion throughout the catalyst's degradation cycle.
4Device complexity
If the reductant dosing is maintained at original level despite catalyst aging, then the dosing system operates simply, but NOx conversion efficiency drops below defined level
Solution Approach 1:
The control module implements feedback control by continuously monitoring NOx conversion efficiency through upstream and downstream sensors. When efficiency drops below a defined threshold, the system automatically adjusts dosing to restore optimal performance, ensuring reliable NOx conversion with only moderate increases in system complexity.
5Reliability
If the reductant dosing is increased to compensate for catalyst aging, then NOx conversion efficiency is maintained, but reductant consumption increases
Solution Approach 1:
The system uses dynamic dosing adjustment rather than a fixed increased dosing level. The control module precisely modulates reductant dosing based on actual catalyst performance and operating conditions, maintaining optimal NOx conversion efficiency while minimizing reductant consumption through adaptive control.
Solution Approach 2:
The dosing parameter is changed from a static increased level to a dynamically optimized level based on real-time monitoring. This allows the system to maintain reliable NOx conversion efficiency while minimizing reductant usage by adjusting dosing to the precise amount needed for effective conversion.
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
The system effectively reduces NOx emissions and ammonia slip by dynamically adjusting the reductant dosing in response to catalyst aging, ensuring consistent NOx conversion efficiency and extending the life of the SCR apparatus.
Implementation Method 1
selective catalytic reduction (SCR) apparatus disposed in downstream flow communication with the exhaust flow port
Implementation Method 2
the urea is converted into ammonia, which is stored in the ceramic walls of the catalyst of the SCR apparatus
Implementation Method 3
The purpose of the urea injection into the SCR apparatus is to control the ammonia storage to assist with NOx conversion
Data Source
AI summary
A dosing control system for an exhaust system of an engine includes: a tank containing a reductant solution having urea; an injector operable to inject the reductant solution into an exhaust flow upstream of an SCR apparatus; first and second NOx sensors disposed to sense NOx emissions in the exhaust flow upstream and downstream, respectively, of the SCR apparatus; and a control module. The control module is disposed in signal communication with the first and second NOx sensors and in operable communication with the injector, the control module being operable to set an original dosing level and decrease a dosing of the reductant solution injected by the injector based on a determination from signals received from the first and second NOx sensors that a reduction in a conversion efficiency of the SCR apparatus below a defined level of conversion efficiency has occurred.