Cordierite Honeycomb Filter Pore Microstructure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current diesel particulate filters face challenges in achieving a balance of low pressure drop, high filtration efficiency, and thermal durability due to limitations in porosity, pore size distribution, and coefficient of thermal expansion, which affect their performance and durability in diesel exhaust filtration applications.
Innovation Solution
The development of porous ceramic honeycomb articles made of cordierite with a specific pore microstructure and manufacturing method that includes a combination of raw materials and heating rates, optimizing porosity, pore size distribution, and thermal expansion properties to achieve low clean and soot-loaded pressure drop, high filtration efficiency, and high strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If increased porosity is achieved through coarser raw materials, pore forming agents, or lower sintering temperatures, then pressure drop is reduced, but thermal expansion increases which compromises filter survivability
Solution Approach 1:
The invention changes the particle size parameter of raw materials to a specific range (d10: 3-10 μm, d50: 15-30 μm, d90: 40-70 μm) to simultaneously achieve low pressure drop and low thermal expansion. This precise parameter control resolves the contradiction by finding an optimal window that balances porosity needs with thermal stability requirements.
Solution Approach 2:
The invention uses a composite approach by combining cordierite with specific auxiliary materials including pore formers (graphite, polyethylene beads, wood flour) and raw materials (talc, kaolin, alumina, silica) in controlled proportions. This composite material strategy enables simultaneous optimization of porosity, pore size distribution, and thermal expansion properties that cannot be achieved with single materials alone.
2Stress or pressure
If porosity is increased to reduce pressure drop, then filtration efficiency may be compromised, but increasing pore size improves pressure drop while potentially reducing filtration efficiency
Solution Approach 1:
The invention applies local quality by creating a controlled pore size distribution where different pore sizes serve different functions: smaller pores (d10: 3-10 μm) provide filtration efficiency while larger pores (d90: 40-70 μm) maintain low pressure drop. This spatial distribution of pore qualities resolves the contradiction between filtration efficiency and pressure drop.
Solution Approach 2:
The invention utilizes porous materials with specifically engineered pore size distribution and porosity (40-54%) to simultaneously achieve low pressure drop and high filtration efficiency. The controlled pore structure, characterized by d10, d50, and d90 parameters, enables both low resistance to flow and effective particle capture.
3Ease of manufacture
If coarser raw materials are used to increase porosity and reduce pressure drop, then manufacturing is simplified, but thermal expansion increases reducing thermal durability
Solution Approach 1:
The invention changes the particle size parameters to a specific intermediate range that is neither too fine nor too coarse. The d10 (3-10 μm), d50 (15-30 μm), and d90 (40-70 μm) specifications provide manufacturable materials that maintain low thermal expansion while achieving adequate porosity, thus preserving both ease of manufacture and thermal durability.
4Use of energy by stationary object
If lower sintering temperatures are used to maintain porosity, then energy consumption is reduced, but pore size distribution widens affecting filtration performance
Solution Approach 1:
The invention applies preliminary action by pre-establishing the correct pore size distribution through careful selection and preparation of raw materials with specific particle size ranges before sintering. This preliminary configuration of particles ensures that the desired pore structure is achieved without requiring excessive sintering energy, thus resolving the contradiction between energy consumption and pore size control.
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 provides ceramic honeycomb articles with a unique combination of properties, including low pressure drop, high filtration efficiency, and high strength, suitable for diesel exhaust filtration, with a narrow pore size distribution that enhances catalyst distribution and contact, leading to improved filtration performance and durability.
Implementation Method 1
Diesel particulate filters capture the soot in the diesel exhaust on or in the porous walls of the filter body
Implementation Method 2
the lower permeability of the soot layer causes a gradual rise in the back pressure of the filter against the engine
Implementation Method 3
the filter must be regenerated by burning out the soot, thereby restoring the back pressure again to low levels
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Disclosed are ceramic honeycomb articles, which are composed predominately of a crystalline phase cordierite composition. The ceramic honeycomb articles possess a microstructure characterized by a unique combination of relatively high total porosity of less than 54%, and relatively narrow pore size distribution having a d10 pore diameter of not less than 8 µm, a d90 pore diameter of not greater than 35 µm, and a value of df = (d5O-d10)/d50 of less than 0.50. The articles exhibit high thermal durability and high filtration efficiency coupled with low pressure drop across the filter. Such ceramic articles are particularly well suited for filtration applications, such as diesel exhaust filters or DPFs. Also disclosed are methods for manufacturing the ceramic articles of the present invention.