Ceramic Honeycomb Filter Pore Gradient for PM Capture
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Solution Overview
Problem
Conventional regenerable-with-catalyst ceramic honeycomb filters face challenges in achieving a high particulate-matter-capturing ratio from the initial stage of operation while maintaining low pressure loss, especially after forced regeneration, due to large pore diameters and opening area ratios on the exhaust gas inlet side, which lead to low capturing efficiency at low exhaust gas temperatures and increased pressure loss upon particulate matter accumulation.
Innovation Solution
The ceramic honeycomb structure features small pore diameters on cell wall surfaces and larger pore diameters inside the cell walls, optimized with a porosity of 55-75%, an average pore diameter of 5-30 μm, and a pore area ratio of 10-30%, along with a cordierite-based ceramic containing Fe and spinel, which reduces thermal expansion coefficients and enhances mechanical strength, using a moldable material with controlled storage elastic modulus and complex viscosity for ink-bottle-shaped pores.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If large pore diameters and opening area ratios are used on the exhaust gas inlet side, then the opening area is increased, but the particulate-matter-capturing ratio decreases and pressure loss increases
Solution Approach 1:
The patent applies local quality by creating different pore diameter distributions in different regions of the cell wall. The exhaust gas inlet side has larger pores (40-100 μm) for high opening area, while the exhaust gas outlet side has smaller pores (5-40 μm) for high capturing ratio. This spatial variation in pore characteristics allows simultaneous optimization of both opening area and capturing efficiency.
Solution Approach 2:
The patent segments the cell wall into distinct functional zones with different pore characteristics. By dividing the pore population into large pores (40-100 μm) and small pores (5-40 μm) with specific area ratios, the structure performs multiple functions: large pores provide opening area and flow capacity, while small pores provide capturing efficiency. This segmentation resolves the contradiction between opening area and capturing ratio.
2Reliability
If high porosity is achieved by adding foamed resin particles, then the particulate-matter-capturing ratio improves, but the cordierite crystal orientation is disturbed and thermal expansion coefficient increases
Solution Approach 1:
The patent changes the physical and chemical parameters of the moldable material to achieve optimal results. By controlling the storage elastic modulus (5×10^4 Pa to 1.4×10^6 Pa) and complex viscosity coefficient (1×10^4 Pa·s to 1×10^7 Pa·s), the material maintains cordierite crystal orientation during extrusion while forming the desired pore structure. This parameter optimization allows high porosity without disturbing crystal orientation.
Solution Approach 2:
The patent uses a composite moldable material consisting of cordierite material powder, foamed resin particles, binder, and water. This composite formulation allows the foamed resin particles to form pores while the cordierite powder maintains its crystal orientation. The binder and water control the extrusion process, ensuring both pore formation and crystal orientation are achieved simultaneously.
3Reliability
If pore diameters are increased to improve capturing efficiency, then the capturing ratio improves, but pressure loss increases upon particulate matter accumulation
Solution Approach 1:
The patent applies local quality by creating different pore diameter distributions in different regions of the cell wall. The exhaust gas inlet side has larger pores (40-100 μm) for high opening area, while the exhaust gas outlet side has smaller pores (5-40 μm) for high capturing ratio. This spatial variation in pore characteristics allows simultaneous optimization of both opening area and capturing efficiency.
Solution Approach 2:
The patent segments the cell wall into distinct functional zones with different pore characteristics. By dividing the pore population into large pores (40-100 μm) and small pores (5-40 μm) with specific area ratios, the structure performs multiple functions: large pores provide opening area and flow capacity, while small pores provide capturing efficiency. This segmentation resolves the contradiction between opening area and capturing ratio.
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 maintains a high particulate-matter-capturing ratio from the initial stage and prevents significant pressure loss even after substantial particulate matter accumulation, while offering excellent thermal shock resistance and mechanical strength.
Implementation Method 1
a moldable material with controlled storage elastic modulus and complex viscosity for ink-bottle-shaped pores
Implementation Method 2
a cordierite-based ceramic containing Fe and spinel, which reduces thermal expansion coefficients and enhances mechanical strength
Implementation Method 3
a ceramic honeycomb structure suitable for a ceramic honeycomb filter for capturing particulate matter
Implementation Method 4
by adding the foamed resin particles without using a large amount of inflammable powder
Data Source
AI summary
In a ceramic honeycomb structure having large numbers of flow paths partitioned by porous cell walls, the cell walls have a porosity of 55-75%, with an average pore diameter Da of 10-30 μm and a pore area ratio Sa of 10-30% on their surfaces, and the average length La of the pores at their openings and the average width Lb of the pores at depth La from the surfaces of the cell walls meet the condition of 1.1<Lb/La<5 in an arbitrary vertical cut surface of the cell walls. In the cordierite-based ceramic honeycomb structure, the ceramic contains Fe and a spinel, the amount of the spinel being 4% or less by an X-ray diffraction intensity ratio, and most of the spinel having particle sizes in a range of 0.01-5 μm.