Catalyst-Carrying Filter Layer Segmentation for PM Removal
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Solution Overview
Problem
Existing catalyst-carrying filters for internal combustion engines are inefficient in removing particulate matter due to insufficient contact between particulate matter and the oxidizing catalyst, leading to frequent regeneration needs and increased pressure loss, while also suffering from catalyst deterioration and poor NOx purification efficiency.
Innovation Solution
A catalyst-carrying filter design with a PM collection layer having a smaller average pore size and coated with a PM removal catalyst, and a gas-outflow-side layer with a gas purification catalyst, optimizing the distribution and amount of oxidizing catalysts to enhance particulate matter removal and prevent catalyst deterioration, while reducing pressure loss and improving NOx purification efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a honeycomb filter with oxidizing catalyst is used to promote oxidation of particulate matter, then particulate matter removal efficiency is improved, but the catalyst is not effectively utilized because particulate matter does not reach the inside of the pores
Solution Approach 1:
The partition wall is divided into two distinct layers: a first layer (inflow-side layer) with small pores for particulate matter collection, and a second layer (outflow-side layer) with large pores for gas purification. This segmentation allows each layer to perform its specific function optimally, with the catalyst primarily located in the second layer where it can effectively contact gas-phase pollutants.
Solution Approach 2:
Different regions of the partition wall are given different properties: the inflow-side layer has small pores optimized for capturing particulate matter, while the outflow-side layer has large pores optimized for gas flow and catalyst contact. The catalyst is locally concentrated in the second layer where it can effectively utilize gas-phase pollutants passing through the large pores.
2Reliability
If particulate matter is collected by the partition wall surface, then particulate matter removal is achieved, but the filter must be frequently regenerated
Solution Approach 1:
The function of particulate matter collection is extracted from the catalyst layer and assigned to the separate inflow-side layer with small pores. This allows the catalyst layer to focus on gas-phase purification while the collection layer handles particulate matter, reducing the frequency of regeneration by preventing catalyst contamination from deposited soot.
Solution Approach 2:
The inflow-side layer with small pores acts as an intermediary between the exhaust gas and the catalyst layer. It collects particulate matter before the gas reaches the catalyst, preventing direct contact between soot and catalyst that would require frequent regeneration, while still allowing the catalyst to effectively purify gas-phase pollutants.
3Reliability
If the average pore size is reduced to ensure particulate matter collection, then collection reliability is improved, but pressure loss increases
Solution Approach 1:
The partition wall is segmented into two layers with different pore sizes: the first layer has small pores for reliable particulate matter collection, while the second layer has large pores for minimal resistance to gas flow. This segmentation allows the system to achieve both reliable collection and low pressure loss by distributing different functions across layers with optimized pore structures.
Solution Approach 2:
Different local regions of the partition wall have different pore sizes optimized for their specific functions: the inflow-side layer uses small pores for collection reliability, while the outflow-side layer uses large pores for gas flow efficiency. This local quality differentiation allows the overall system to maintain low pressure loss while achieving reliable particulate matter collection.
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 filter effectively increases the contact between particulate matter and the catalyst, improving regeneration efficiency, reducing pressure loss, and enhancing NOx purification, thereby extending catalyst lifespan and maintaining emission standards.
Implementation Method 1
an oxidizing catalyst for promoting oxidation (combustion) of particulate matter contained in exhaust gas
Implementation Method 2
the oxidizing catalyst supported on the surface of the partition wall of the honeycomb filter and the inner surface of the pore formed in the partition wall
Implementation Method 3
a filter that collects particulate matter is generally provided in an exhaust gas passage connected to an internal combustion engine or the like
Implementation Method 4
a partition wall formed of a porous ceramic having a number of pores
Data Source
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AI summary
A catalyst-carrying filter includes a gas-inflow-side layer and a gas-outflow-side layer, the gas-inflow-side layer including a PM collection layer that has a small average pore size and a PM removal catalyst layer that supports or is coated with an oxidizing catalyst, and the gas-outflow-side layer including a gas purification catalyst layer that supports or is coated with a gas purification catalyst.