Honeycomb Monolith Coating via Vacuum Inversion
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Solution Overview
Problem
Existing methods for coating honeycomb monolith substrates with catalyst components face challenges such as high back pressure due to viscous washcoats, uneven coating, inefficiency in using expensive platinum group metals, and lack of flexibility for 'zoning' to enhance catalyst activity, particularly when using higher viscosity slurries and excessive liquid quantities.
Innovation Solution
A method and apparatus for automatedly coating honeycomb monolith substrates with lower viscosity liquids, involving steps like holding the substrate vertically, introducing a predetermined liquid, sealing it, inverting, and applying a vacuum to draw the liquid along the channels, which allows for precise and uniform coating of catalyst washcoats on inlet and outlet channels, optimizing catalyst loading and reducing liquid waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If higher viscosity slurries are used for coating, then the coating stability is improved, but the back pressure increases and coating uniformity deteriorates
Solution Approach 1:
The patent changes the viscosity parameter of the slurry from high (100-500 cps) to low (<50 cps) and modifies the coating process parameters (vacuum application timing, substrate inversion) to achieve both low back pressure and uniform coating. This parameter change resolves the contradiction by decoupling viscosity from coating stability through process optimization.
2Stability of the object's composition
If higher viscosity slurries are used for coating, then the coating stability is improved, but the coating uniformity deteriorates
Solution Approach 1:
The patent inverts the substrate after introducing the slurry, reversing the conventional coating approach. This inversion allows the low viscosity slurry to distribute uniformly through capillary action before vacuum removal, achieving both stability and uniformity that were previously contradictory.
Solution Approach 2:
The patent uses vacuum (pneumatic) control to remove excess slurry after coating. By applying vacuum at a controlled stage, the process achieves uniform coating removal without requiring high initial slurry viscosity, resolving the contradiction between stability and uniformity.
3Quantity of substance
If excess quantities of liquid are used for coating, then the coating coverage is improved, but the material loss increases
Solution Approach 1:
The patent introduces feedback control through vacuum application that removes excess slurry. The vacuum acts as a feedback mechanism that regulates the final coating quantity, ensuring adequate coverage while preventing excessive material application and loss.
Solution Approach 2:
The patent intentionally applies excess slurry initially (excessive action) but then removes the excess through vacuum control, achieving the desired coating coverage while minimizing material loss. This partial retention approach resolves the contradiction between coverage and material loss.
4Ease of operation
If impregnation method is used for coating, then the automation difficulty is reduced, but the coating speed deteriorates
Solution Approach 1:
The patent performs preliminary slurry introduction before vacuum application and substrate inversion. This preliminary action allows the slurry to penetrate the substrate structure in advance, enabling faster overall processing while maintaining operational simplicity.
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 approach enables more accurate and efficient loading of platinum group metals, reduces back pressure, achieves uniform axial coating profiles, and allows for flexible 'zoning' of catalysts, improving catalyst activity and compliance with customer specifications while minimizing material loss.
Implementation Method 1
applying a vacuum to open ends of the channels of the substrate at the inverted, lower end of the substrate to draw the liquid along the channels of the substrate
Implementation Method 2
applying a vacuum to open ends of the channels of the substrate at the inverted, lower end of the substrate to draw the liquid along the channels of the substrate
Implementation Method 3
placing a wall-flow filter substrate in a bath of aqueous solution and allowing the solution to impregnate the filter by capillary action
Data Source
AI summary
Catalysed wallflow filter substrate monolith obtainable by coating a honeycomb monolith substrate comprising a plurality of channels with a liquid comprising a catalyst component comprises the steps of: (i) holding a honeycomb monolith substrate substantially vertically; (ii) introducing a pre-determined volume of the liquid into the substrate via open ends of the channels at a lower end of the substrate; (iii) sealingly retaining the introduced liquid within the substrate; (iv) inverting the substrate containing the retained liquid; and (v) applying a vacuum to open ends of the channels of the substrate at the inverted, lower end of the substrate to draw the liquid along the channels of the substrate.