SCR System Efficiency Estimation via Injection and Loading Models
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Solution Overview
Problem
Current selective catalytic reduction systems for internal combustion engines face imprecision in estimating nitrogen oxides conversion efficiency, leading to insufficient or excessive ammonia injection, which fails to meet stringent future emission standards and results in increased carbon dioxide emissions.
Innovation Solution
A method that estimates the total efficiency of the SCR system by modeling the efficiency of two reactions: one between newly injected reducing agent and nitrogen oxides upstream of the catalyst, and another between remaining nitrogen oxides and stored reducing agent, taking into account environmental conditions and catalyst aging, without requiring hardware modifications, only software adaptations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional efficiency estimation methods are used, then current emission standards can be met, but future stringent emission standards cannot be complied with due to imprecision
Solution Approach 1:
The efficiency estimation is segmented into two distinct components: efficiency due to injection (reacting newly injected reducing agent with nitrogen oxides) and efficiency due to loading (reacting stored reducing agent with remaining nitrogen oxides). This segmentation allows each component to be modeled separately with appropriate parameters, improving overall estimation precision and enabling compliance with future stringent emission standards.
2Object-generated harmful factors
If insufficient reducing agent is injected due to underestimated efficiency, then ammonia desorption is avoided, but the full conversion potential of the system is not exploited
Solution Approach 1:
The system uses a feedback mechanism where the estimated total efficiency (combining injection and loading efficiencies) continuously informs the reducing agent injection quantity calculation. This ensures that the injection amount is precisely matched to the actual conversion needs, avoiding both ammonia desorption from over-injection and unexploited conversion potential from under-injection.
3Productivity
If too much reducing agent is injected due to overestimated efficiency, then full conversion potential is exploited, but ammonia desorption occurs
Solution Approach 1:
The invention changes the parameters used for efficiency estimation by incorporating multiple influencing factors including reducing agent loading, catalyst temperature, nitrogen dioxide ratio, hourly volumetric speed, and system aging. These parameter changes enable more accurate efficiency estimation, ensuring optimal reducing agent injection that exploits full conversion potential without causing ammonia desorption.
4Measurement precision
If hardware modifications are made to improve precision, then emission standards compliance improves, but implementation cost increases
Solution Approach 1:
The invention replaces potential hardware modifications with a software-based solution. By implementing a refined efficiency estimation algorithm in the engine computer that models both injection and loading efficiencies with multiple parameters, the system achieves superior precision without any physical hardware changes, thereby avoiding increased implementation costs.
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 approach enhances the precision of nitrogen oxides conversion efficiency, achieving a higher maximum attainable efficiency and significantly reducing carbon dioxide emissions while maintaining compliance with stringent emission standards at a lower implementation cost.
Implementation Method 1
selective catalytic reduction systems, also called SCR systems, aim to reduce the nitrogen oxides (NOx) contained in the exhaust gases. SCR systems implement a chemical reaction between nitrogen oxides and a reducing agent conventionally taking the form of ammonia.
Implementation Method 2
through another chemical species (a precursor), such as urea which decomposes into ammonia and carbon dioxide under the effect of heat.
Data Source
AI summary
The invention relates primarily to a method for controlling a catalytic selective reduction system for treating nitrogen oxides (NOx) present in the exhaust line of an internal combustion engine. The system comprises means for introducing a reducing agent into the exhaust line upstream of a nitrogen oxide reduction catalyst. The method is characterized in that it includes a step for estimating the system's efficiency, referred to as the total efficiency (EffTot), based on a model (100) of the efficiency of a first reaction, referred to as the injection efficiency (Efflnj), between a newly injected quantity of reducing agent and nitrogen oxides present upstream of the catalyst, and a model (101) of the efficiency of a second reaction, referred to as the loading efficiency (EffLd), between nitrogen oxides remaining after the first reaction and a quantity of reducing agent stored in the catalyst.