Exhaust Catalyst Device with Shortened Oxidation Layer
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Solution Overview
Problem
Existing catalytic converter systems for reducing nitrogen oxides, hydrocarbons, and carbon monoxide in exhaust gases from industrial plants, particularly in the cement industry, are costly due to the need for expensive precious metals in oxidation catalysts, and face challenges with dust-laden gases that cause blockages and high pressure losses.
Innovation Solution
A catalytic converter device with a denitrification catalyst layer and a downstream oxidation catalyst layer, where the oxidation catalyst layer has a shorter length and a higher number of flow channels per unit area than the denitrification catalyst layer, reducing costs and increasing the effective surface area for carbon monoxide oxidation, and incorporating dust cleaning devices to manage dust deposits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxidation catalyst layers are made longer to increase contact time for CO oxidation, then oxidation efficiency improves, but device volume and cost increase
Solution Approach 1:
The patent transitions from increasing length in one dimension to increasing surface area through higher channel density in the same footprint. By packing more channels per unit area, the oxidation catalyst achieves greater contact surface area without extending the device length, thus maintaining CO oxidation efficiency while reducing overall device volume.
Solution Approach 2:
The patent changes the geometric parameters of the catalyst structure by increasing the number of flow channels per unit cross-sectional area. This parameter change allows the oxidation catalyst layer to provide sufficient contact surface area for CO oxidation without requiring increased layer length, thereby reducing device volume while maintaining oxidation efficiency.
2Volume of stationary object
If oxidation catalyst layers are made shorter to reduce device volume and cost, then device compactness improves, but mass transfer efficiency for CO oxidation decreases
Solution Approach 1:
Instead of compensating for shorter length by extending in other dimensions, the patent increases the density of flow channels within the same cross-sectional area. This dimensional reorganization provides greater total channel surface area in a compact volume, maintaining mass transfer efficiency while achieving device compactness.
Solution Approach 2:
The patent modifies the structural parameters by increasing the number of flow channels per unit area in the oxidation catalyst layer. This parameter change ensures that even with reduced layer length, the total catalytic surface area remains sufficient for effective CO oxidation, thus maintaining mass transfer efficiency in a more compact device.
3Reliability
If honeycomb catalysts with large flow cross-sections are used to prevent dust blockages, then dust resistance improves, but the surface area per unit volume for catalytic reaction decreases
Solution Approach 1:
The patent changes the geometric parameter of flow channel density by increasing the number of channels per unit cross-sectional area. This allows the catalyst to maintain large overall cross-sections for dust resistance while achieving high total surface area through increased channel multiplicity, thus resolving the trade-off between dust resistance and catalytic surface area.
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 achieves efficient reduction of nitrogen oxides, hydrocarbons, and carbon monoxide at lower costs by optimizing the geometry and surface area of the catalyst layers, while minimizing dust-related issues and pressure losses, ensuring effective pollutant removal from dust-laden exhaust gases.
Implementation Method 1
The reduction of nitrogen oxides is achieved, among other methods, through selective catalytic reduction (SCR)
Implementation Method 2
at least one layer of an oxidation catalyst downstream of the denitrification catalyst for reducing carbon monoxide
Implementation Method 3
Two layers serve to reduce NOx and oxidize hydrocarbons
Data Source
Figure 1
Figure 2
Figure 3~4d
AI summary
The catalyst device according to the invention for reducing pollutants in an exhaust gas has at least one layer of a denitrification catalyst for reducing nitrogen oxides and at least one layer of an oxidation catalyst connected downstream of the denitrification catalyst for reducing carbon monoxide. The at least one layer of the denitrification catalyst and the at least one layer of the oxidation catalyst connected downstream each has a plurality of flow channels. The length of the at least one layer of the oxidation catalyst is less than the length of a denitrification catalyst layer connected directly upstream thereof, and the at least one layer of the oxidation catalyst has a greater number of flow channels than the first layer of the denitrification catalyst.