Honeycomb Structure Micro Pores Slurry Coating Clogging
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Solution Overview
Problem
The reduction in cell wall thickness of catalytic converter honeycomb structures to improve exhaust gas conversion efficiency leads to mechanical strength deterioration and cell clogging issues due to decreased porosity, making it difficult to deposit catalyst solids uniformly and economically.
Innovation Solution
Incorporating micro fine pores with diameters of 2 μm or less in the cell walls to enhance slurry coating properties, allowing for a larger coat layer deposition with lower viscosity slurries and preventing cell clogging, while maintaining mechanical integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the cell wall thickness is reduced to improve exhaust gas conversion efficiency, then the thermal capacity is reduced and premature activation is improved, but the mechanical strength deteriorates
Solution Approach 1:
The invention introduces micro fine pores with diameters of 2 μm or less into the cell wall structure. These pores increase the surface area without significantly increasing the overall cell wall thickness, allowing the cell walls to be thinner while maintaining mechanical strength. The porous structure provides both the reduced thermal capacity needed for premature activation and the surface area required for mechanical integrity.
2Strength
If the porosity is reduced to heighten the density and compensate for mechanical strength, then the mechanical strength is improved, but the surface area of each cell is decreased making it difficult to deposit solids
Solution Approach 1:
The invention transitions from modifying the overall porosity to creating micro fine pores at a different scale (2 μm or less). This dimensional approach allows the micro pores to contribute to surface area for solid deposition while the overall cell wall density remains high enough to maintain mechanical strength. The micro fine pores provide additional surface area without compromising the macrostructural integrity.
3Quantity of substance
If the viscosity of the slurry is increased to deposit more solids, then the solid content is improved, but the coat layer thickness increases causing cell clogging
Solution Approach 1:
The micro fine pores in the cell wall act as a reservoir that can accommodate solid particles. When slurry with appropriate viscosity is applied, the solids are drawn into these micro pores, allowing for increased solid content deposition without proportionally increasing the outer coat layer thickness. This prevents cell clogging while maximizing catalyst carrier deposition.
4Force
If the binder content in the slurry is reduced to decrease viscosity, then the slurry flows better, but the solids settle and require continuous stirring
Solution Approach 1:
The invention changes the pore size parameter to 2 μm or less, which creates capillary forces that prevent solid settlement even in low-viscosity slurries. The micro fine pores provide sufficient resistance to gravity-induced settling, allowing the slurry to maintain homogeneity without continuous stirring while still achieving good flow characteristics for coating.
5Productivity
If the cell density is increased to improve exhaust gas conversion, then the converting function is improved, but more slurry is required causing thicker coat layers and cell clogging
Solution Approach 1:
The micro fine pores provide additional internal surface area within the cell wall structure. This allows the honeycomb to achieve higher effective cell density for exhaust gas conversion without proportionally increasing the external dimensions or requiring thicker coat layers. The solids deposit within the micro pores rather than forming thick external layers, preventing cell clogging.
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 honeycomb structure with micro fine pores enables efficient and uniform deposition of catalyst solids, reducing economic losses from cell clogging and allowing for adjustable coat amounts, even with reduced binder content in the slurry.
Implementation Method 1
micro fine pores having diameters of 2 μm (micrometer) or less are formed and dispersed in the cell wall surface... larger amounts of slurry is coated on the cell walls by one coating operation
Data Source
AI summary
With the recent yearly increase in cell density, use of the same slurry as a conventional one for forcibly depositing a solid, e.g., alumina for supporting, on the surface of cell walls has come to arouse a trouble that the resultant coat layer is thick and cell clogging is more apt to occur. When a slurry whose viscosity has been reduced by reducing the binder amount is used, the slurry which has flowed into cells is discharged without leaving a solid adherent to the surface of the cell walls. Namely, it is difficult to secure a desired solid deposition amount. A honeycomb structure for slurry coating is provided which is made of a porous object, wherein the surface of cell walls formed in the structure has fine pores dispersedly formed therein and having a pore diameter of 2 μm or smaller. Preferably, the total volume of the fine pores is 0-0.17 ml, excluding 0 ml, per g of the structure.