Exhaust Aftertreatment Device SCR Segmentation
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Solution Overview
Problem
Current exhaust gas post-treatment systems for combustion engines, particularly those using selective catalytic reduction (SCR), face challenges in starting early enough at low temperatures and maintaining efficiency in urban driving conditions, leading to potential non-compliance with stringent NOx emission standards and increased ammonia leaks, especially in heavy vehicles.
Innovation Solution
A compact post-treatment device architecture featuring a small SCR catalyst integrated with a particle filter (SCRF) and an ammonia slip catalyst, which distributes NOx reduction across two organs, enhancing thermal efficiency and minimizing ammonia leaks by treating residual ammonia.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional SCR catalyst is used, then NOx reduction is achieved, but the device starts too slowly at low temperatures and is too large to be installed close to the engine
Solution Approach 1:
The SCR function is divided into two separate organs: a small dedicated SCR catalyst (6) with length of 50-60mm for rapid low-temperature startup, and a particle filter (7) with integrated SCRF catalyst for high-temperature NOx reduction. This segmentation allows each component to be optimized for its specific temperature range without requiring a single large catalyst to handle all conditions.
Solution Approach 2:
The patent transitions from a single-dimensional solution (one large SCR catalyst) to a two-dimensional approach by distributing SCR functionality across two separate organs positioned at different locations in the exhaust system. This allows the small SCR catalyst to be placed close to the engine for rapid warming while the particle filter with SCRF handles downstream processing.
2Speed
If the SCR catalyst is positioned close to the engine for rapid startup, then low-temperature performance improves, but the device becomes too large for the confined engine compartment space
Solution Approach 1:
By segmenting the SCR function into two organs, the small dedicated SCR catalyst (6) can be positioned close to the engine (within 500mm of exhaust collector outlet) for rapid startup, while the larger particle filter with SCRF (7) is positioned downstream where space is available. This eliminates the need for a single large catalyst to be installed in the confined engine compartment.
3Object-generated harmful factors
If a single SCRF particle filter is used, then NOx reduction is achieved, but ammonia leaks increase due to insufficient low-temperature SCR activity
Solution Approach 1:
The patent segments the NOx treatment function so that the small dedicated SCR catalyst (6) handles low-temperature conditions with high activity, reducing ammonia leaks during cold operation. The particle filter with SCRF (7) handles high-temperature conditions. This segmentation ensures optimal SCR activity at each temperature range, preventing ammonia slip that would occur with a single SCRF filter lacking sufficient low-temperature activity.
Solution Approach 2:
The small dedicated SCR catalyst (6) acts as an intermediary component between the exhaust source and the particle filter with SCRF (7). It pre-treats the exhaust gases at low temperatures, reducing the ammonia leak risk before gases reach the particle filter, where further NOx reduction occurs at higher temperatures.
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 configuration improves NOx reduction performance across a wider temperature range, ensures compliance with stricter emission standards, and reduces ammonia leaks, maintaining the device's compactness while effectively treating both gaseous and particulate pollutants.
Implementation Method 1
an oxidation catalyst member (3), a mouth (41) of a means (4) for introducing a reducing agent (or a precursor of a reducing agent)
Implementation Method 2
An oxidation catalyst allows the treatment of carbon monoxide, unburned hydrocarbons
Implementation Method 3
a catalyst member (6) for selective catalytic reduction of nitrogen oxides
Implementation Method 4
selective catalytic reduction technologies, or 'SCR' for 'Selective Catalytic Reduction' in English, are known, which consist of reducing NOx by introducing a reducing agent
Implementation Method 5
a particle filter member (7) provided with a catalyst coating (8) for selective catalytic reduction of nitrogen oxides
Implementation Method 6
a particle filter can be used to treat soot particles
Implementation Method 7
an ammonia leak treatment catalyst member (8) arranged downstream of the particle filter member (7)
Data Source
Figure 1~3
AI summary
The invention relates to a device for the post-treatment of the exhaust gases of a combustion engine (1), characterized in that it comprises, from upstream to downstream: an oxidation catalyst part DOC (3); an outlet (41) of a means (4) for introducing a reducing agent or reducing agent precursor for the selective catalytic reduction SCR of nitrogen oxides ; a catalyst part (6) for the selective catalytic reduction SCR of the nitrogen oxides NOx; a particle filter part (7) provided with a catalyst coating for selective catalytic reduction SCRF of nitrogen oxides NOx; and a part (8) for treating ammonia leaks.