CH4 Oxidation Catalytic Converter NO2 Ratio Control
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Solution Overview
Problem
Internal combustion engines that combust natural gas face challenges in reducing methane (CH4) emissions due to incomplete combustion, leading to high costs and short operating periods of catalytic converters used in existing exhaust gas aftertreatment systems.
Innovation Solution
Adjusting the NO2 proportion in the exhaust gas upstream of CH4-oxidation catalytic converters through measures on the gas combustion system or exhaust gas aftertreatment system, utilizing NO-oxidation catalytic converters and SCR-catalytic converters with ammonia or its precursors to enhance CH4 decomposition and reduce emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If catalytic converters with platinum metal group metals are used to decompose CH4, then CH4 decomposition efficiency is improved, but cost increases and operating period decreases due to deactivation by sulphur oxides
Solution Approach 1:
The patent changes the chemical composition parameters of the exhaust gas by introducing a two-stage aftertreatment system. The first stage converts NO to NO2, creating a specific NO2/NO ratio in the exhaust gas that enhances CH4 decomposition efficiency while reducing sulphur oxide deactivation, thereby extending the catalytic converter's operating period.
Solution Approach 2:
The patent introduces NO2 as an intermediary substance that mediates the CH4 decomposition process. By converting NO to NO2 in the first aftertreatment stage, the system creates a more effective oxidizing environment for CH4 decomposition that is less susceptible to sulphur oxide poisoning, thus improving both efficiency and durability.
2Reliability
If catalytic converters with high precious metal content are used, then CH4 decomposition efficiency is improved, but cost increases
Solution Approach 1:
The patent changes the exhaust gas composition parameters through the two-stage aftertreatment system, specifically creating optimal NO2/NO ratios that enhance catalytic activity. This allows the system to achieve high CH4 decomposition efficiency with reduced precious metal loading in the catalytic converter.
Solution Approach 2:
The patent substitutes part of the precious metal-based catalytic mechanism with a chemical environment optimization approach. By controlling the NO2/NO ratio and creating favorable oxidation conditions, the system reduces dependence on high quantities of precious metals while maintaining high CH4 decomposition efficiency.
3Reliability
If NO2 proportion in exhaust gas is increased to improve CH4 decomposition, then CH4 emissions reduction is improved, but NO2 emissions before decomposition increase
Solution Approach 1:
The patent performs preliminary conversion of NO to NO2 in the first aftertreatment stage before the CH4 decomposition occurs in the second stage. This preliminary action ensures that when CH4 decomposition happens, the optimal NO2 proportion is already present, maximizing decomposition efficiency while the subsequent stage handles NO2 conversion to prevent emissions.
Solution Approach 2:
The patent implements a continuous two-stage process where the first stage continuously converts NO to NO2, and the second stage continuously decomposes CH4 using the generated NO2. This continuous action ensures that NO2 is promptly utilized for CH4 decomposition rather than being emitted, maintaining high decomposition efficiency while controlling NO2 emissions.
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
Effectively reduces CH4 emissions by optimizing the NO2 proportion in the exhaust gas, minimizing the need for precious metals and extending the operating life of catalytic converters, while also lowering NO2 emissions post-decomposition.
Implementation Method 1
the NO2 proportion in the exhaust gas is adjusted via at least one NO-oxidation catalytic converter
Implementation Method 2
the decomposition of CH4 can be improved as a result of which it is possible to reduce CH4 emissions
Implementation Method 3
in the exhaust gas downstream of the SCR-catalytic converter NH3 or an NH3 precursor substance is introduced
Data Source
AI summary
Method for operating an internal combustion engine which has a gas combustion system and an exhaust gas post-treatment system. Exhaust gas that leaves the gas combustion system is directed to at least one CH4 oxidation catalytic converter of the exhaust gas post-treatment system. The CH4/NO2 mole ratio in the exhaust gas is set in a defined fashion by at least one gas-combustion-system-side and/or exhaust-gas-post-treatment-system-side measure upstream of at least one CH4 oxidation catalytic converter.