SCR Catalyst Reducing Agent Dosage Control
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Solution Overview
Problem
Existing SCR catalytic converters in exhaust gas treatment systems for mobile internal combustion engines face challenges in achieving complete conversion of nitrogen oxides and preventing ammonia breakthroughs due to temperature limitations and varying storage capacities, making precise addition of reducing agents difficult.
Innovation Solution
A method and device for controlled addition of a reducing agent, such as a urea-water solution, to an SCR catalytic converter with a nitrogen oxide storage capacity, involving determination of the nitrogen oxide amount and storage capacity, active regulation of the dosage, and temperature control to ensure complete conversion and prevent ammonia breakthroughs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If SCR catalyst is used for nitrogen oxide reduction, then nitrogen oxide conversion is achieved, but ammonia breakthrough occurs due to unconverted ammonia escaping from the catalyst
Solution Approach 1:
The control unit continuously monitors exhaust gas composition and adjusts the reducing agent dosage in real-time based on feedback from sensors. This closed-loop control ensures optimal conversion of nitrogen oxides while preventing ammonia breakthrough by dynamically adapting the urea injection amount to actual operating conditions and catalyst storage capacity.
Solution Approach 2:
The system actively controls the storage capacity of the SCR catalyst by adjusting operating parameters such as temperature and reducing agent dosage. By changing these parameters dynamically, the system optimizes the balance between nitrogen oxide conversion efficiency and prevention of ammonia slip, allowing the catalyst to operate in different operational modes as needed.
2Productivity
If reducing agent dosage is increased to improve nitrogen oxide conversion, then conversion rate increases, but ammonia breakthrough risk increases
Solution Approach 1:
The control unit uses real-time feedback from exhaust gas sensors to continuously adjust the reducing agent dosage. This ensures that the dosage is optimized for maximum nitrogen oxide conversion while simultaneously preventing excessive dosage that would lead to ammonia breakthrough, maintaining both high conversion rates and reliable emission control.
Solution Approach 2:
The system dynamically adjusts the reducing agent dosage based on varying operating conditions, exhaust gas composition, and catalyst state. This dynamic control allows the system to adapt to changing demands, increasing dosage when conversion is needed and decreasing it when ammonia breakthrough risk arises, rather than using a fixed dosage strategy.
3Adaptability or versatility
If SCR catalyst storage capacity is utilized to handle varying exhaust conditions, then flexibility is improved, but precise reducing agent addition becomes more difficult
Solution Approach 1:
The control unit continuously monitors the catalyst's storage capacity state through exhaust gas analysis and adjusts the reducing agent dosage accordingly. This feedback mechanism enables precise control of reducing agent addition even as the catalyst's storage capacity varies with different operating conditions, maintaining dosing accuracy throughout the catalyst's operational cycle.
Solution Approach 2:
The system replaces simple mechanical dosing mechanisms with an electronically controlled dosing system that uses sensor feedback and control algorithms. This substitution enables precise control of reducing agent addition by electronically adjusting dosage based on real-time information about catalyst storage capacity and exhaust composition, rather than relying on fixed mechanical dosing rates.
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 method ensures high conversion rates of nitrogen oxides and prevents ammonia breakthroughs by adapting the reducing agent dosage to the varying storage capacity and operating conditions, achieving efficient exhaust gas treatment.
Implementation Method 1
an SCR catalyst is regularly installed in the exhaust system, which reduces nitrogen oxides to nitrogen (N2) and water (H2O) with the reducing agent
Implementation Method 2
the SCR catalyst is further equipped with an electric heater
Implementation Method 3
The thermohydrolytic decomposition of urea, releasing ammonia, is achieved through the heat of the exhaust gas stream and/or a hydrolysis catalyst
Data Source
Figure 1~2
Figure 3a~3d
AI summary
A method and a device (8) for the controlled feeding of a reducing agent (1) into an exhaust gas treatment unit (2) with a storage capability for a component (3) of the exhaust gas (4) which is to be reduced in a mobile internal combustion engine (5), wherein the method comprises at least the following steps: a) determination of a quantity (6) of the component (3) of the exhaust gas (4) which is generated by the mobile internal combustion engine (5) and is to be reduced; b) determination of a storage capability of the exhaust gas treatment unit (2) for the component (3) of the exhaust gas (4) which is to be reduced; c) determination of metering (7) of the reducing agent (1) into the exhaust gas treatment unit (2) as a function of the steps a) and b); and d) feeding of the reducing agent (1) into the exhaust gas treatment unit (2).