Exhaust Gas Purifying System with Segmented Honeycomb Filter and NOx Catalyst
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Solution Overview
Problem
Conventional honeycomb catalytic members used for purifying NOx and microparticles in diesel engine exhaust gas face challenges in achieving high purifying efficiency while minimizing pressure loss, and are difficult to mount in limited spaces due to size constraints.
Innovation Solution
The system incorporates a honeycomb filter followed by a NOx purifying catalytic member with a catalyst carrier having a similar structure, arranged in series in the exhaust gas flow path, optimizing cell density, pore size, and porosity to enhance NOx purification efficiency while maintaining low pressure loss and compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cell density is increased to improve transmissibility of components to be purified, then purifying efficiency is improved, but pressure loss increases
Solution Approach 1:
The invention divides the purification function into two separate components: a honeycomb filter for PM removal and a NOx purifying catalytic member for NOx purification. This segmentation allows each component to be optimized independently - the catalytic member can have high cell density for efficient NOx purification without the pressure loss penalty affecting the entire system, while the filter handles particle removal separately.
Solution Approach 2:
The honeycomb filter acts as an intermediary component between the engine and the NOx purifying catalytic member. It pre-cleans the exhaust gas by removing microparticles, which prevents catalyst poisoning and maintains efficient mass transfer to the catalytic layer, thereby improving overall purification efficiency without requiring excessive cell density in the catalytic member alone.
2Productivity
If cell density is increased to increase surface area of catalytic layer, then purifying efficiency is improved, but pressure loss increases
Solution Approach 1:
The invention separates the functions of particle filtration and gas-phase catalytic purification into distinct components. The NOx purifying catalytic member can be designed with optimized cell density and large surface area for catalytic reactions without being constrained by the pressure loss requirements of the particle filter, achieving high purification efficiency with acceptable pressure loss.
Solution Approach 2:
The catalytic member uses a porous ceramic honeycomb structure with optimized pore size and porosity parameters. This porous structure provides large internal surface area for the catalytic layer while maintaining adequate flow channels, enabling efficient mass transfer of NOx components to the catalytic sites without excessive pressure drop across the member.
3Loss of energy
If size of honeycomb catalytic member is increased to reduce pressure loss, then pressure loss is reduced, but mounting space requirement increases
Solution Approach 1:
The invention divides the exhaust treatment system into two compact components: a honeycomb filter and a NOx purifying catalytic member. This segmentation allows each component to be smaller in size while maintaining effective performance, reducing the total mounting space requirement compared to a single large catalytic member, while the optimized structure of each component keeps pressure loss acceptable.
Solution Approach 2:
The catalytic member employs a three-dimensional honeycomb structure with optimized geometric parameters (cell density, pore size, porosity, wall thickness) that maximizes surface area and catalytic activity within a compact volume. This dimensional optimization enables high purification efficiency in a small footprint without requiring excessive length or diameter that would increase mounting space.
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 configuration achieves superior NOx purifying efficiency with reduced pressure loss and allows for mounting in constrained spaces, making it suitable for automotive and industrial applications.
Implementation Method 1
When the components to be purified diffuse in the catalytic layer at insufficient speed, the purifying efficiency of the honeycomb catalytic member tends to decrease
Implementation Method 2
a NOx purifying catalytic member 32 having substantially the same shape as the honeycomb filter 1 and carrying a NOx purifying catalyst 21
Data Source
Figure 1~4
Figure 5~7
Figure 8~9
AI summary
An exhaust gas purifying system has a honeycomb filter (1,31) including a porous partition wall (4,14,24,26) having a number of pores arranged so that a plurality of cells communicating between two end faces are formed, and a plugging portion (17,27) disposed in either of the end faces or inside the cell so as to plug the cell; and a NOx purifying catalyst (21) including a honeycomb catalyst carrier (55) having substantially same shape as the honeycomb filter (1,31), and a NOx selective reducing SCR catalyst or a NOx occluding catalyst carried on surface of the partition wall (4,14,24,26) and/or on surface of the pores, wherein the honeycomb filter (1,31) and the NOx purifying catalytic member (12,32) are disposed in this order in an exhaust gas flow path where exhaust gas discharged from a diesel engine circulates. To provide an exhaust gas purifying system which realizes excellent purifying efficiency of NOx contained in exhaust gas discharged from a diesel engine (5), and small pressure loss, and can be mounted in limited space.