Integrated MFPF Filter Boosts NO2 Concentration
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Solution Overview
Problem
Current exhaust gas purifying systems for diesel vehicles face challenges in efficiently reducing nitrogen oxides due to low NO2/NOx ratios, are hindered by hydrocarbon interference with SCR function, and consume excessive precious metals, especially when dealing with low-temperature exhaust gases and particulate matter.
Innovation Solution
A multifunctional exhaust gas purifying filter (MFPF) is introduced, integrating a catalyzed diesel particulate filter (cDPF) and diesel oxidation catalyst (DOC) into a honeycomb structure with ceramic-like materials, coated with oxidation catalysts and zeolite for enhanced NO2 production and hydrocarbon adsorption, minimizing precious metal usage and optimizing SCR operational temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a DOC is installed downstream of a cDPF to increase NO2 concentration, then the NO2/NOx ratio improves, but the system complexity increases and spatial clearance is reduced
Solution Approach 1:
The patent combines the DOC and cDPF into a single integrated filter element, where the DOC function is incorporated within the cDPF structure. This merging eliminates the need for separate DOC and cDPF components, reducing system complexity while maintaining the ability to increase NO2 concentration for effective SCR operation.
Solution Approach 2:
The integrated filter element performs multiple functions simultaneously: it filters particulate matter (cDPF function), oxidizes CO and HC (DOC function), and generates NO2 from NO (SCR preparation function). This multi-functionality reduces the number of separate components needed while achieving all desired exhaust gas treatment objectives.
2Quantity of substance
If a DOC is installed downstream of a cDPF, then NO2 concentration increases, but the device requires more spatial clearance which is not available in vehicle installations
Solution Approach 1:
By merging the DOC and cDPF into a single integrated filter element, the patent eliminates the need for separate components that would require additional spatial clearance. The integrated design fits within the existing exhaust system space constraints while still achieving the desired NO2 generation for SCR operation.
3Productivity
If precious metals are used extensively in SCR catalysts, then nitrogen oxide reduction efficiency improves, but the cost increases
Solution Approach 1:
The patent performs preliminary oxidation of CO and HC, and conversion of NO to NO2, within the integrated filter element before the exhaust gas reaches the SCR catalyst. This preliminary action prepares the exhaust gas in an optimal state for SCR, allowing the SCR catalyst to operate more efficiently with reduced precious metal content while maintaining high nitrogen oxide reduction performance.
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 MFPF effectively increases the NO2/NOx ratio, suppresses hydrocarbon flow to the SCR layer, reduces precious metal consumption, and enhances nitrogen oxide decomposition efficiency while maintaining fuel efficiency and cost-effectiveness.
Implementation Method 1
NO+1⁄2O2→NO2 (4)
Implementation Method 2
an adsorption layer such as zeolite with excellent hydrocarbon adsorption ability is primarily coated on the surface of a contaminated gas inlet hole
Implementation Method 3
NOx can be decomposed through the following reaction mechanism on a catalyst under existence of a reducing agent
Implementation Method 4
4NO+4NH3+O2→4N2+6H2O,SCR (1)
Implementation Method 5
NO2+PM(carbon)→NO+CO/CO2 (5)
Data Source
AI summary
The present invention relates to a configuration method of a multifunctional particulate filter (MFPF), capable of reducing the content of particulate material (PM), carbon monoxide (CO) and hydrocarbons (HC), and increasing the content of nitrogen dioxide (NO2). The MFPF may coat zeolite and an oxidation catalyst on both exhaust gas intake/discharge sides simultaneously, so as to minimize the slippage of HC and generate high-concentration NO2.