Segmented Honeycomb Filter for PM Purification
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Solution Overview
Problem
Single honeycomb filters used in diesel particulate filters (DPFs) face challenges in effectively oxidizing and trapping particulate matter due to limitations in catalyst support and pore size, leading to inefficient PM oxidation and purification.
Innovation Solution
A honeycomb filter system comprising a first honeycomb filter with a porous partition wall matrix and a second honeycomb filter with a surface layer, where the first filter has a mean pore diameter of 25 µm to 70 µm and a porosity of 40% to 70%, and the second filter has a peak pore diameter of 0.3 µm to 20 µm and a porosity of 60% to 95%, allowing for enhanced oxidation and trapping of PM.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If pores are made small in a single honeycomb filter, then catalyst support capacity is improved, but PM trapping efficiency deteriorates because PM cannot enter deep layers
Solution Approach 1:
The invention divides the single honeycomb filter into two separate honeycomb filters connected in series. The first filter (upstream) has smaller pores optimized for catalyst support, while the second filter (downstream) has larger pores optimized for PM trapping. This segmentation allows each filter to specialize in one function, resolving the contradiction between catalyst capacity and trapping efficiency.
2Reliability
If pores are enlarged in a single honeycomb filter, then PM trapping efficiency is improved, but catalyst contact ability deteriorates
Solution Approach 1:
By segmenting the filter system into two filters, the upstream filter maintains small pores for effective catalyst contact, while the downstream filter uses enlarged pores for efficient PM trapping. This resolves the contradiction by assigning different pore sizes to different functional stages.
3Device complexity
If a single honeycomb filter is used, then device complexity is reduced, but PM purification performance deteriorates
Solution Approach 1:
The invention uses two honeycomb filters instead of one, accepting increased device complexity to achieve superior PM purification performance. The segmented structure enables optimized catalyst support and PM trapping functions that a single filter cannot provide.
Solution Approach 2:
The invention combines two honeycomb filters with different pore size characteristics into a series configuration. The first filter with smaller pores and the second filter with larger pores work together synergistically to achieve high catalyst contact ability and high PM trapping efficiency simultaneously.
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 achieves high PM purification efficiency by oxidizing and trapping particulate matter without allowing it to pass through, reducing pressure loss and residual PM accumulation.
Implementation Method 1
an oxidation catalyst containing at least one material selected from the group consisting of platinum (Pt), palladium, ceria, and alumina is supported on a part or whole of the inner surfaces of the pores of the partition wall matrix
Implementation Method 2
particulate matter in the exhaust gas is oxidized and decomposed by a catalyst
Implementation Method 3
particulate matter in the exhaust gas is oxidized and decomposed by a catalyst and trapped and removed by the pores
Implementation Method 4
trapped and removed by the pores
Implementation Method 5
fluid (exhaust gas) allowed to flow in from an end portion on one side where predetermined cells are open permeates the partition walls
Implementation Method 6
flows to the remaining cell side as a permeation fluid
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
There is provided a honeycomb filter system comprising a first honeycomb filter disposed upstream and satisfying the conditions (F1) and (F2) and a second honeycomb filter disposed downstream and satisfying the conditions from (R1) to (R5) to be lined up in series. (F1) In the first honeycomb filter, the partition wall matrix has a mean pore diameter of 25 µm or more and below 70 µm and a porosity of 40% or more and below 70%. (F2) In the first honeycomb filter, an oxidation catalyst containing at least one material selected from the group consisting of platinum (Pt), palladium, ceria, and alumina is supported on a part or whole of the inner surfaces of the pores of the partition wall matrix. (R1) In the second honeycomb filter, the surface layer has a peak pore diameter equivalent to or smaller than that of the partition wall matrix and a porosity higher than that of the partition wall matrix. (R2) In the second honeycomb filter, the surface layer has a peak pore diameter of 0.3 µm or more and below 20 µm and a porosity of 60% or more and below 95% (measured by mercury intrusion technique). (R3) In the second honeycomb filter, thickness L1 of the surface layer is 0.5% or more and below 30% of thickness L2 of the partition wall. (R4) In the se'cond honeycomb filtration, a mass per filtering area of the surface layer is 0.01 mg/cm2 or more and below 6 mg/cm2. (R5) In the second honeycomb filter, the partition wall matrix has a mean pore diameter of 10 µm or more and below 60 µm and a porosity of 40% or more and below 65%. The system has a PM oxidative decomposition function and a PM trapping function and is excellent in PM purification performance.