Hybrid SCR-SCRF Catalyst Subassembly for Diesel Exhaust
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Solution Overview
Problem
Existing exhaust gas purification systems for diesel engines, particularly those using SCRF catalysts, face challenges with increased component volume, weight, cost, and thermal inertia, which affect efficiency and manufacturing costs.
Innovation Solution
A hybrid catalyst subassembly with an SCR catalyst upstream of an SCRF catalyst in a common housing, where the SCR catalyst has a dedicated supporting substrate and the SCRF catalyst is designed to match the volume of traditional particulate filters, allowing for modular construction and reduced dimensions, thereby lowering costs and improving thermal efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an SCRF catalyst is used for exhaust gas purification, then NOx conversion capability is improved, but component volume and weight increase
Solution Approach 1:
The catalyst system is segmented into two distinct functional units: an SCR catalyst for NOx reduction and an SCRF catalyst for particulate filtration with integrated NOx reduction. This segmentation allows each component to be optimized for its specific function, enabling the SCRF catalyst to maintain smaller volume by focusing on particulate capture while the SCR catalyst handles the bulk of NOx conversion.
Solution Approach 2:
The SCRF catalyst is designed with multi-functionality, serving both as a particulate filter and an NOx reduction catalyst. This universal design allows the same component to perform multiple functions, reducing the need for separate large-volume components and thereby decreasing overall system volume while maintaining effective NOx conversion.
2Reliability
If an SCRF catalyst is used for exhaust gas purification, then NOx conversion capability is improved, but manufacturing cost increases
Solution Approach 1:
By segmenting the catalyst system into SCR and SCRF components, manufacturing can be optimized for each part separately. The SCRF catalyst can be produced with reduced volume and simplified structure, lowering material costs, while the SCR catalyst can be manufactured using established processes, achieving cost efficiency through specialization.
Solution Approach 2:
The design allows the use of cost-effective materials and structures in the SCRF catalyst that may have shorter service life or lower performance requirements compared to a full-featured SCR catalyst, reducing overall manufacturing cost while maintaining adequate NOx conversion capability through the combined system.
3Reliability
If an SCRF catalyst is used for exhaust gas purification, then NOx conversion capability is improved, but thermal inertia increases
Solution Approach 1:
Segmenting the catalyst into SCR and SCRF components allows the SCRF catalyst to be designed with smaller mass and reduced thermal inertia, as it does not need to handle the entire NOx conversion load alone. The lighter SCRF catalyst heats up and reaches operating temperature faster, reducing thermal inertia effects.
Solution Approach 2:
The design changes the operational parameters by distributing NOx conversion tasks between two catalysts, allowing the SCRF catalyst to operate at lower loading. This parameter change enables the use of materials and structures with lower thermal mass, reducing overall thermal inertia while maintaining effective NOx conversion through the combined action of both catalysts.
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 results in a more efficient and cost-effective exhaust gas purification system with improved NOx conversion, reduced weight, and faster light-off behavior, while maintaining the same overall volume, thus addressing the disadvantages of traditional SCRF catalysts.
Implementation Method 1
SCR (selective catalytic reduction) refers to the selective catalytic reduction of nitrogen oxides (NOx) from exhaust gases of internal combustion engines
Implementation Method 2
soot particles and other solids present in the exhaust gas flow are fixed on a porous filter wall by adhesion
Implementation Method 3
In the oxidation catalyst, carbon monoxide and volatile hydrocarbons are oxidized to form carbon dioxide
Implementation Method 4
hydrolysis of the urea solution to form ammonia is performed in a first step
Data Source
AI summary
A catalyst subassembly for a device for purifying exhaust gases from an internal combustion engine, in particular a diesel engine, includes an SCRF catalyst and an SCR catalyst upstream of the SCRF catalyst. The two catalysts are arranged in a common catalyst housing. The catalyst housing, the SCRF catalyst and the SCR catalyst can be selected from a modular system for different variants of the internal combustion engine.