Diesel Engine SCR-ASC Catalyst for Emissions
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Solution Overview
Problem
Off-highway engines face challenges in meeting Tier IV final and Stage 4 emissions standards due to the complexity and cost of existing emissions abatement technologies, which often require multiple treatment systems and increased fuel consumption, particularly in achieving low NOx and PM reductions without compromising engine efficiency.
Innovation Solution
An engine system that includes a diesel engine with an SCR downstream of a reductant introduction point, an ASC to manage ammonia slip, and no intervening treatment systems, allowing for efficient low-temperature NOx and PM reduction without the need for additional catalysts like DOC or DPF, thereby reducing system costs and fuel consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If multiple treatment systems (DOC, DPF, SCR) are used to meet emissions standards, then NOx and PM reduction is improved, but system complexity and cost increase
Solution Approach 1:
The patent combines the DOC and SCR functions into a single integrated catalyst system. The catalyst performs both oxidation (DOC function) and selective catalytic reduction (SCR function) within one device, eliminating the need for separate DOC and DPF components while achieving the required NOx and PM reduction levels.
Solution Approach 2:
The single catalyst system is designed to perform multiple functions simultaneously: oxidizing CO and HC, reducing NOx through SCR, and trapping particulate matter. This multi-functional approach replaces the traditional multi-component aftertreatment system with one universal device that handles all emission control requirements.
2Object-generated harmful factors
If active DPF is used to remove PM, then PM reduction is improved, but fuel consumption increases
Solution Approach 1:
The catalyst system operates passively without requiring active regeneration through fuel injection. The PM removal is achieved through the natural catalytic activity and temperature conditions already present in the exhaust stream, eliminating the need for additional fuel consumption that would be required for active DPF regeneration.
3Object-generated harmful factors
If multiple catalysts are used, then emissions compliance is improved, but system cost increases
Solution Approach 1:
The patent integrates multiple catalytic functions into a single catalyst component, reducing the total number of parts that need to be manufactured, assembled, and maintained. This consolidation significantly reduces system cost while maintaining full emissions compliance through the combined activities of the single catalyst system.
4Object-generated harmful factors
If DPF is placed upstream of other treatment units, then PM removal is improved, but heat management becomes more difficult
Solution Approach 1:
The patent eliminates the need for upstream DPF placement by integrating PM removal functionality directly into the SCR catalyst. This removes the thermal management challenges associated with protecting upstream components from high temperatures, as the single catalyst system is designed to handle all temperature conditions within the exhaust stream.
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 achieves significant PM reduction (up to 50%) and NOx compliance within Tier 4 final/Stage IV standards, while minimizing system costs and fuel consumption, by leveraging the low-temperature activity of the SCR and dual functionality of the ASC in reducing PM and ammonia slip.
Implementation Method 1
an SCR immediately downstream of the conduit, the SCR having good low temperature activity
Implementation Method 2
an ammonia slip catalyst (ASC) downstream of the SCR acting to remove excess ammonia
Implementation Method 3
the ASC and the SCR in combination act to remove excess PM
Data Source
AI summary
A diesel engine having improved particulate emissions for particle material (PM) reduction for off-highway engine systems includesa reductant introduction point downstream of the diesel engine and in fluid flow communication therewith with no intervening treatment systems;a conduit immediately downstream of the reductant introduction point having sufficient length to enable mixing of the reductant with exhaust gases of the engine,an SCR immediately downstream of the conduit, the with good low temperature activity such that a diesel oxidation catalyst (DOC) is not neededan ammonia slip catalyst (ASC) downstream of the SCR acting to remove excess ammonia to meet the relevant limits for ammonia; andwherein the ASC and the SCR in combination act to remove excess PM.