NOx Trap Desulfurization via Periodic Lean-Rich Phases
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Solution Overview
Problem
Existing desulphurization processes for NOx-Traps in diesel engines face challenges in maintaining efficient sulfur removal while avoiding high temperatures and the formation of harmful emissions like H2S and COS, requiring complex and sensitive models that are difficult to develop and adjust effectively.
Innovation Solution
Implementing a desulphurization process that includes alternating periods of rich and lean phases, with the introduction of at least one long lean period to increase oxygen storage capacity, allowing for a significant increase in oxygen storage and reducing harmful emissions by managing the duration of these phases using specific laws and conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If very high temperature (>650°C) and rich medium are used for desulfurization, then sulfur removal efficiency is improved, but harmful emissions (H2S and COS) increase and temperature regulation becomes difficult
Solution Approach 1:
The patent applies periodic alternation between rich phases (for desulfurization) and lean phases (for oxygen recharge and temperature control). This periodic action allows the system to achieve high sulfur removal efficiency during rich phases while controlling harmful emissions through subsequent lean phases that recharge oxygen and reduce temperature, preventing excessive H2S and COS formation
Solution Approach 2:
The patent dynamically changes operating parameters (air-fuel ratio, temperature) by alternating between rich and lean phases. During rich phases, the air-fuel ratio is enriched to promote sulfur removal. During lean phases, the air-fuel ratio is leaned out to recharge oxygen storage capacity and reduce temperature, thereby controlling the formation of harmful emissions
2Quantity of substance
If very high temperature (>650°C) is maintained for desulfurization, then sulfur removal efficiency is improved, but NOx-Trap device aging accelerates and structural degradation occurs
Solution Approach 1:
The patent uses periodic alternation between rich and lean phases to limit the duration of high-temperature exposure. High temperature is maintained only during rich phases for sulfur removal, followed by lean phases that allow temperature reduction, thereby preventing excessive thermal aging and structural degradation of the NOx-Trap device
Solution Approach 2:
The patent applies preliminary anti-action by introducing lean phases immediately after rich phases to counteract the thermal aging effect. The lean phases serve as a protective measure that reduces temperature and recharges oxygen storage capacity before the next rich phase, preventing cumulative thermal damage to the NOx-Trap structure
3Measurement precision
If complex dynamic models are used to regulate NOx-Trap temperature, then temperature control precision is improved, but system complexity and difficulty of development increase
Solution Approach 1:
The patent employs feedback mechanisms using downstream oxygen sensor measurements to regulate the alternation between rich and lean phases. The oxygen sensor provides feedback on the oxygen storage capacity of the NOx-Trap, allowing the control system to adjust the timing and duration of rich and lean phases to maintain optimal temperature and achieve effective desulfurization without requiring complex dynamic models
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 approach enhances desulphurization efficiency, reduces harmful emissions, and simplifies the development process by leveraging a double dynamic oxygen storage mechanism, maintaining optimal oxygen recharge and minimizing polluting emissions.
Implementation Method 1
the sulfur initially present in the fuel and the oil is found in the exhaust gases in the form of sulfur dioxide SO2, which is then adsorbed by the NOx-Trap on the sites of adsorption provided for nitrogen oxides NOx
Implementation Method 2
Desulfurization of NOx-Trap requires very high heat within the NOx-Trap, i.e. a temperature generally above 650°C, and a rich medium (excess reducing agents) to reduce the sulfur components
Implementation Method 3
The sulfur oxide S02 desorbed during the desulphurization reacts with the reducing agents present and is transformed after a few seconds into hydrogen sulphide H2S and carbonyl sulphide COS
Implementation Method 4
fuel can be injected just after top dead center during the expansion phase, which has the effect of increasing the temperature and richness of the exhaust gases
Data Source
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AI summary
The method involves setting a long lean period (18) for increasing oxygen storage capacity parameter of a nitrogen oxide trap, where the long lean period has duration that ranges between 20 and 60 seconds. An end of the short lean period (17) is determined by applying a law, where the short lean period has duration that ranges between 5 and 30 seconds. An end of rich period (16) is determined by applying the law for restarting a short lean period. An independent claim is also included for a power train of a motor vehicle.