Exhaust Aftertreatment N2O Reduction via Dosing Frequency
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Solution Overview
Problem
Current exhaust gas aftertreatment systems face challenges in reducing nitrous oxide (N2O) emissions, particularly due to temperature-dependent ammonia storage issues in SCR catalytic converters, which can lead to ammonia slip and subsequent N2O production, a potent greenhouse gas.
Innovation Solution
The method involves adjusting the dosing frequency of the reducing agent, such as urea, upstream of the SCR catalytic converter, increasing it when exhaust gas temperatures exceed a threshold to minimize N2O production, while maintaining the total amount of reducing agent, thereby reducing variations and ammonia slip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the dosing frequency of reducing agent is increased when exhaust gas temperature exceeds threshold, then N2O emissions are reduced, but the system complexity increases
Solution Approach 1:
The dosing frequency of the reducing agent is dynamically adjusted based on exhaust gas temperature conditions. When the temperature exceeds a predetermined threshold, the dosing frequency is increased to minimize N2O production. This dynamic adaptation allows the system to optimize emissions reduction without requiring complex hardware modifications, as the control strategy adapts to varying operating conditions.
Solution Approach 2:
The invention changes the dosing frequency parameter of the reducing agent injection system based on temperature conditions. By adjusting this operational parameter rather than modifying the physical structure, the system reduces N2O emissions while avoiding increased device complexity. The total amount of reducing agent remains constant, but its distribution over time is optimized.
2Reliability
If ammonia storage level is maintained at adequate level in SCR catalytic converter, then NOx conversion efficiency is improved, but ammonia slip increases at high temperatures
Solution Approach 1:
The system dynamically adjusts the dosing frequency of the reducing agent based on temperature conditions. At high temperatures where ammonia storage capacity decreases, the dosing frequency is increased to prevent ammonia slip while maintaining adequate storage levels for NOx conversion. This dynamic control allows the system to adapt to temperature variations and maintain optimal performance without excessive ammonia accumulation.
Solution Approach 2:
The control unit monitors temperature conditions and adjusts the dosing frequency accordingly. When temperature exceeds a threshold, the system increases dosing frequency to compensate for reduced ammonia storage capacity, ensuring continuous adequate storage levels for efficient NOx conversion while preventing ammonia slip. This feedback mechanism maintains the balance between conversion efficiency and ammonia emission 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
This approach effectively reduces N2O emissions by optimizing the dosing frequency of the reducing agent, ensuring higher conversion efficiency and minimizing N2O production in both SCR and ASC catalysts, without requiring changes to existing hardware.
Implementation Method 1
the reducing agent is broken down and forms ammonia (NH3), which in turn reacts with NOx to form water and nitrogen (N2)
Implementation Method 2
The reducing agent reacts with NOx in the SCR catalytic converter to achieve the NOx reduction
Implementation Method 3
NH3 must be stored in the SCR catalytic converter. For the SCR catalytic converter to be able to work efficiently, the stored level must be at an adequate level
Implementation Method 4
an ammonia slip catalyst, hereinafter ASC catalyst, is used downstream of the SCR catalytic converter to process any residual ammonia
Implementation Method 5
The purpose of this is in part to generate a sufficient amount of NO2 to achieve passive oxidation of soot that is captured by a DPF. This occurs according to the reaction: C + 2NO2 → CO2 + 2NO
Data Source
Figure 1~2
Figure 3
AI summary
The invention concerns an exhaust gas aftertreatment system (2) adapted so as to reduce the amount of N2O that is produced in a selective catalytic reduction catalytic converter (SCR catalytic converter) (6) and/or in an ammonia slip catalyst (ASC catalyst) (4) disposed in the exhaust gas flow from a combustion engine (3), which exhaust gas aftertreatment system (2) comprises an SCR catalytic converter (6) arranged in an exhaust gas line (8) upstream of an optional ASC catalyst (4) and the exhaust gases from the combustion engine (3) pass through the SCR catalytic converter (6) and any ASC catalyst (4) before they are released into the surroundings via the exhaust gas outlet (10), and which exhaust gas aftertreatment system (2) further comprises an injection device (12) adapted so as to inject a reducing agent into the exhaust gases in the exhaust gas line (8) upstream of the SCR catalytic converter (6) at a dosing frequency F. The exhaust gas aftertreatment system further comprises a control unit (14) adapted so as to generate a control signal (16) intended to adjust the dosing frequency F so that the amount of N2O that is produced in the SCR catalytic converter (6) and/or in the ASC catalyst (4) is minimized while maintaining the amount of reducing agent added. The invention also concerns a method for an exhaust gas aftertreatment system.