SCR Catalyst Converter Segmentation for NOx Purification
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Solution Overview
Problem
Conventional exhaust gas purifying devices with SCR catalyst converters face issues of deteriorated NOx purification efficiency due to catalyst poisoning over time and fail to meet stricter emission regulations, especially at cold start points and low load conditions.
Innovation Solution
The exhaust gas purifying device includes a series arrangement of a first SCR catalyst converter, an oxidation catalyst converter, and a filter section, with a second SCR catalyst converter, featuring a pillar-shaped honeycomb structure with specific cell density, porosity, and catalyst loading, which enhances thermal energy transmission and catalyst activation at low temperatures, reducing catalyst poisoning and maintaining high NOx purification efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional SCR catalyst converter is used, then NOx purification is achieved at high temperatures, but the catalyst deteriorates due to poisoning over time and fails to meet stricter emission regulations
Solution Approach 1:
The patent divides the exhaust gas purification system into multiple segments: a first SCR catalyst converter positioned upstream, followed by an oxidation catalyst converter, then a filter section, and finally a second SCR catalyst converter downstream. This segmentation allows each component to perform its specific function optimally, with the first SCR converter handling initial NOx reduction and the second SCR converter providing enhanced purification, thereby extending overall system reliability without premature catalyst deactivation
Solution Approach 2:
The oxidation catalyst converter and filter section serve as intermediary components between the two SCR catalyst converters. These intermediaries protect the catalysts by oxidizing harmful substances before they reach the SCR catalysts and filtering particulate matter, thereby reducing catalyst poisoning and extending the service life of the SCR catalysts while maintaining continuous NOx purification efficiency
2Reliability
If a conventional SCR catalyst converter is used, then catalytic reaction occurs at high temperatures, but the NOx purification efficiency cannot satisfy regulations at cold start points and low load points
Solution Approach 1:
The patent applies local quality by positioning the first SCR catalyst converter with a specific catalyst formulation optimized for cold start conditions at the upstream location where exhaust gas temperature is lowest. This localized optimization ensures effective NOx purification during cold starts and low load operations, while downstream components handle high-temperature purification, thereby achieving adaptability across all operating conditions
Solution Approach 2:
The first SCR catalyst converter performs preliminary NOx reduction action at the upstream position before the exhaust gas cools down or during cold start conditions. This preliminary action ensures that NOx purification begins immediately upon engine startup, meeting emission regulations from cold start points without waiting for the exhaust gas to reach high 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 ensures high NOx purification efficiency and reduced catalyst deterioration, meeting stricter emission standards even at low temperatures and extended use periods, while being cost-effective and easy to manufacture.
Implementation Method 1
an oxidation catalyst converter (2)
Implementation Method 2
a selective catalytic reduction (SCR) catalyst converter including a honeycomb structure onto which a SCR catalyst is loaded. The SCR catalyst converter is configured to reduce NOx by use of a reducing agent
Implementation Method 3
a pillar-shaped honeycomb structure with specific cell density, porosity, and catalyst loading, which enhances thermal energy transmission and catalyst activation at low temperatures
Data Source
AI summary
An exhaust gas purifying device includes a first SCR catalyst converter, an oxidation catalyst converter, a filter section, and a second SCR catalyst converter arranged in series to a flow direction of an exhaust gas. The first SCR catalyst converter includes a pillar-shaped honeycomb structure a cell density of which is from 31 to 78 cells/cm2, a porosity of the partition walls of which is from 50 to 65%, and in which a first SCR catalyst is loaded onto the surfaces of the partition walls and inner portions of pores formed in the partition walls, and an amount of the first SCR catalyst to be loaded onto the surfaces of the partition walls and the inner portions of the pores is from 200 to 500 g/L and an amount of the first SCR catalyst to be loaded onto the inner portions of the pores is from 5 to 80 g/L.