Segmented Particulate Filter for NOx Reduction
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Solution Overview
Problem
Existing exhaust treatment systems face challenges in achieving an optimal NO to NO2 ratio for effective NOx reduction, often requiring larger reduction catalysts due to excessive NO2 production from all-exhaust-contacting oxidation catalysts, leading to slower NOx reduction efficiency.
Innovation Solution
A particulate filter system with a housing featuring multiple parallel channels defined by porous walls, where only a percentage of channels are coated with NO oxidizing materials, allowing controlled conversion of NO to NO2 and reducing back pressure, thereby optimizing the NO2 to NO ratio for faster and more efficient NOx reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If all tubes of the oxidation catalyst are coated with NO oxidizing material, then the amount of NO2 in the exhaust flow is increased, but the NOx reduction efficiency becomes slower and a larger reduction catalyst is required
Solution Approach 1:
The oxidation catalyst is divided into multiple channels, with only a subset (e.g., 50%) coated with NO oxidizing material. This segmentation allows the exhaust flow to be split between coated and uncoated channels, controlling the NO2 generation rate to optimize SCR reduction efficiency while preventing excessive NO2 accumulation
Solution Approach 2:
Different channels within the oxidation catalyst have different functional properties: some channels are coated with NO oxidizing material to convert NO to NO2, while other channels remain uncoated to allow direct exhaust passage. This local differentiation enables precise control over the NO:NO2 ratio in the combined exhaust flow
2Reliability
If a larger reduction catalyst is used to compensate for slow NOx reduction, then the device size increases, but the system complexity and space requirements increase
Solution Approach 1:
The oxidation catalyst performs preliminary conversion of NO to NO2 in a controlled manner before the exhaust reaches the SCR reduction catalyst. By pre-adjusting the NO:NO2 ratio to be closer to the optimal 50:50 range, the subsequent reduction catalyst operates more efficiently and requires smaller volume to achieve the same NOx reduction effectiveness
3Productivity
If the entire exhaust flow contacts platinum or palladium coating, then NO oxidation is maximized, but back pressure increases and system cost increases
Solution Approach 1:
The oxidation catalyst channels are segmented into coated and uncoated sections, allowing exhaust to flow through both types. This reduces the total surface area of precious metal coating required while maintaining sufficient NO oxidation capability, thereby reducing back pressure and material costs
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
The system effectively increases the NO2 to NO ratio, enhancing the efficiency of NOx reduction in the SCR device while minimizing back pressure and catalyst size requirements, thereby improving overall exhaust treatment efficiency.
Implementation Method 1
a plurality of parallel channels defined by a plurality of porous walls within the first and second sections of the housing
Implementation Method 2
The first chamber includes tubes coated with a catalytic material such as platinum that oxidizes NO and hydrocarbons
Data Source
AI summary
A filter includes a housing including an inlet and an outlet, and the housing includes a first section and a second section. The filter also includes a plurality of parallel channels defined by a plurality of porous walls within the first and second sections of the housing. The plurality of channels extend between the inlet and the outlet. The plurality of channels in the first section of the housing includes at least one first channel including an inlet stopper and at least one second channel including an outlet stopper. The plurality of channels in the second section of the housing including at least one open channel.