Honeycomb SCR Catalyst with Segmented Core for NOx Removal
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Solution Overview
Problem
Vanadium-based SCR catalysts used in stationary sources for NOx removal face challenges with sulfur oxide conversion, leading to fouling and mechanical instability due to SO2 oxidation, which reduces catalyst efficiency and stability.
Innovation Solution
A honeycomb SCR catalyst with an inner core layer of inert clay materials and an outer layer of titania, vanadium pentoxide, and tungsten trioxide, where the inner core makes up 50-95% of the channel wall thickness, providing mechanical stability and reducing SO2 oxidation while maintaining NO reduction activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the wall thickness of the monolith is reduced to increase specific surface area and NO removal activity, then the SCR reaction efficiency is improved, but the mechanical stability and erosion resistance of the catalyst structure deteriorates
Solution Approach 1:
The catalyst wall is segmented into two distinct layers: an inner structural layer providing mechanical strength and an outer catalytic layer providing NO removal activity. This segmentation allows each layer to be optimized for its specific function without compromising the other.
Solution Approach 2:
The catalyst employs a composite structure combining a structural layer (made of stabilizers and binders) with a catalytic layer (containing vanadium oxide, tungsten oxide, and titania). This composite approach enables simultaneous achievement of mechanical stability and high catalytic activity.
2Object-generated harmful factors
If the amount of vanadium oxide is reduced to minimize SO2 oxidation to SO3, then sulfate emissions are decreased, but the SCR reaction rate is also reduced
Solution Approach 1:
Vanadium oxide is concentrated in the outer catalytic layer where it is needed for SCR activity, while the inner structural layer contains no vanadium oxide, thereby eliminating SO2 oxidation in that region. This local distribution optimizes both SCR performance and minimizes harmful SO3 formation.
Solution Approach 2:
The patent optimizes the vanadium oxide content in the catalytic layer and introduces tungsten oxide as a modifier to change the chemical parameters of the catalyst, reducing its SO2 oxidation activity while maintaining SCR reaction rate through enhanced catalytic efficiency.
3Strength
If a thick catalyst wall is used to ensure mechanical stability, then the structure integrity is maintained, but the specific surface area for NO removal is reduced
Solution Approach 1:
The catalyst wall is divided into an inner structural layer for mechanical strength and an outer catalytic layer for surface area optimization. This allows the structural layer to be sufficiently thick for stability while the outer layer provides maximum catalytic surface area within the remaining thickness.
Solution Approach 2:
The composite structure with distinct structural and catalytic layers enables independent optimization of mechanical properties and catalytic surface area, resolving the trade-off between wall thickness requirements for strength versus surface area requirements for activity.
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 solution enhances mechanical stability, reduces SO2 oxidation, and maximizes NO reduction activity, offering improved erosion resistance and structure stability compared to conventional monoliths.
Implementation Method 1
the content of NOx in the flue gas can be removed or substantially reduced by conversion to free nitrogen with a reducing agent typically ammonia in the presence of a catalyst by the following reactions: 4NO+4NH3+O2-4N2+6H2O
Implementation Method 2
SO2 oxidation, which reduces catalyst efficiency and stability... vanadium-based catalysts in fact oxidise SO2 to SO3
Data Source
AI summary
A vanadium oxide based honeycomb SCR catalyst composed of a plurality of corrugated sheets stacked upon one another to form a plurality of flow through channels, the corrugated sheets are provided with an inert inner core layer and an outermost layer containing a SCR catalyst composition.