Monolithic SCR Catalyst Drying Rate Control
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Solution Overview
Problem
Concentration gradients in vanadium-based SCR catalysts affect NOx conversion efficiency due to uneven distribution of vanadium oxide, which is exacerbated by drying and washcoating processes, leading to reduced catalytic activity at high temperatures and increased activity at low temperatures.
Innovation Solution
A method involving controlled drying of the washcoated substrate with a drying rate of 5 mm/min or less, using micro or long wave heating, and positioning horizontally to minimize capillary forces, combined with calcination for activating the catalyst, ensures even vanadium distribution across the substrate surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional drying methods are used with high drying rates, then drying time is reduced and productivity is improved, but concentration gradients of vanadium oxide form leading to poor manufacturing precision
Solution Approach 1:
The patent applies parameter changes by controlling the drying rate to 5 mm/min or less and using micro or long wave heating methods to achieve uniform moisture removal. This prevents capillary forces from creating concentration gradients while maintaining efficient drying process
Solution Approach 2:
The patent replaces conventional thermal drying with micro or long wave heating methods. This substitution of heating mechanism allows for more uniform energy distribution through the washcoat layer, preventing localized overheating and associated concentration gradients
2Productivity
If fast drying is applied to increase productivity, then drying efficiency is improved, but capillary forces cause vanadium compound migration and gradient formation
Solution Approach 1:
The patent controls the drying rate parameter to 5 mm/min or less, which is slow enough to prevent capillary forces from migrating vanadium compounds but still maintains practical drying efficiency. This parameter optimization balances productivity with prevention of harmful compound migration
Solution Approach 2:
The patent uses micro or long wave heating to replace conventional thermal gradients that drive capillary action. This substitution eliminates the mechanical driving force (capillary forces) that causes vanadium compound migration while maintaining drying efficiency
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 significantly reduces concentration gradients and enhances NOx conversion efficiency across a broader temperature range by maintaining consistent vanadium oxide concentration, improving catalytic activity at both low and high temperatures.
Implementation Method 1
Both gravity and capillary forces cause the vanadium compound to move over the titania surface at and cause vanadium gradients over the surface.
Implementation Method 2
the drying of the coated substrate is performed by means of micro wave or long wave heating
Implementation Method 3
After having been coated with the washcoat, the substrate is dried and finally calcined for activation of the catalytic components in the coat.
Data Source
Figure 1
Figure 2~3
AI summary
Method of preparing monolithic SCR catalyst with a plurality of gas flow channels comprising the steps of (a) providing a monolithic shaped substrate with a plural ty of parallel gas flow channels; (b) coating the substrate with a wash coat slurry comprising vanadium oxide precursor compounds and titania and optionally tungsten oxide precursor compounds; and (c) drying the thus coated substrate with a drying rate of 5 mm/min or less along flow direction through the gas flow channels; and (d) activating the dried coated substrate by calcining.