Dual Catalyst Exhaust System Substoichiometric Additive Control
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Solution Overview
Problem
Existing exhaust treatment systems face challenges in optimizing fuel consumption and emission reduction, particularly due to inadequate soot oxidation in filters and the imbalance between nitrogen oxides reduction and fuel efficiency, leading to increased costs and reduced performance.
Innovation Solution
The method involves estimating future operating conditions based on road section data to actively control the supply of additives in a dual-step reduction process, maintaining substoichiometric conditions in the first reduction catalyst device and using the second device to eliminate residual nitrogen oxides, ensuring efficient soot oxidation and optimized fuel consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the first additive supply is increased to improve nitrogen oxides reduction in the first catalyst device, then nitrogen oxides emission decreases, but soot oxidation efficiency deteriorates due to insufficient nitrogen dioxide availability
Solution Approach 1:
The exhaust treatment system is divided into two separate reduction catalyst devices, each handling a portion of the nitrogen oxides reduction task. The first device operates under substoichiometric conditions to preserve soot oxidation capability, while the second device completes the reduction process, thereby segmenting the function to resolve the contradiction between nitrogen oxides reduction and soot oxidation efficiency.
Solution Approach 2:
The first reduction catalyst device is intentionally operated with partial action (substoichiometric additive supply) rather than complete nitrogen oxides reduction. This deliberate incomplete reduction maintains nitrogen dioxide levels necessary for soot oxidation, while the second device provides the additional reduction needed to meet emission standards.
2Object-generated harmful factors
If a single reduction catalyst device is used to maximize nitrogen oxides reduction, then emission standards are met, but fuel consumption increases due to stoichiometric or overstoichiometric additive supply
Solution Approach 1:
The nitrogen oxides reduction function is segmented across two catalyst devices, allowing the first device to operate under energy-efficient substoichiometric conditions while the second device handles the remaining reduction load. This segmentation enables overall emission compliance without requiring excessive additive supply that would reduce fuel efficiency.
Solution Approach 2:
The system changes the operating parameter (additive supply ratio) from stoichiometric or overstoichiometric to substoichiometric in the first catalyst device. This parameter change improves fuel efficiency by reducing unnecessary additive consumption while maintaining effective nitrogen oxides reduction through the coordinated operation of the second device.
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 allows for precise control of additive administration, reducing nitrogen oxide emissions while maintaining high fuel efficiency and minimizing additive usage, leading to improved soot oxidation and reduced manufacturing costs.
Implementation Method 1
SCR (Selective Catalytic Reduction) catalysts are a commonly used type of catalyst for this type of reduction, primarily for heavy goods vehicles. SCR catalysts usually use ammonia NH3, or a composition from which ammonia may be generated/formed, as an additive to reduce the amount of nitrogen oxides NOx in the exhausts.
Implementation Method 2
The additive added to the catalyst is adsorbed (stored) in the catalyst, in the form of ammoniac NH3, so that a redox-reaction may occur between nitrogen oxides NOx in the exhausts and ammonia NH3 available via the additive.
Implementation Method 3
a filter arranged in said exhaust treatment system to catch and oxidise soot particles
Data Source
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AI summary
According to the present invention, a method and an exhaust treatment system, are provided tor treatment of an exhaust stream, which results from a combustion in a combustion engine and comprises nitrogen oxides NOX. The method comprises an estimate of at least one future operating condition for the exhaust treatment system, which is based on a representation of a road section ahead of the vehicle. A first supply of a first additive into the exhaust stream is carried out, wherein the first additive is used at least at a first reduction of a first amount of nitrogen oxides NOx_1i in the exhaust stream in a first reduction catalyst device. A second supply of a second additive into the exhaust stream is carried out, wherein the second additive is used at a second reduction of a second amount of nitrogen oxides NOx_2 in the exhaust stream in a second reduction catalyst device, arranged downstream of the first reduction catalyst device. According to the present invention, the first supply of additive is controlled based on the estimated at least one future operating condition in such a manner, that the first reduction catalyst device is exposed, over time, to a substoichiometric condition, with respect to the first additive and the first amount of nitrogen oxides NOx_1.