SCR Converter NH3 Slip Control via Mass Flow Feedback
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Solution Overview
Problem
Current SCR catalytic converter systems with two converters face challenges in controlling ammonia (NH3) slip, leading to potential overshooting and reduced NOx performance due to reactive responses only to NH3 filling levels, rather than deviations from desired levels.
Innovation Solution
The method involves controlling the NH3 mass flow after the first SCR catalytic converter to detect deviations in NH3 slip earlier and adjust the filling level in the second SCR catalytic converter, using a first control system to setpoint values calculated by models or sensors, ensuring accurate and robust control by maintaining a steady NH3 filling level in the second converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the SCR catalytic converter is operated at a high NH3 filling level to achieve high NOx conversion rates, then NOx conversion efficiency is improved, but ammonia slip occurs when the reservoir is completely filled
Solution Approach 1:
The patent implements a feedback control system that continuously monitors the NH3 filling level in the second SCR catalytic converter and adjusts the NH3 mass flow from the first SCR catalytic converter accordingly. The control system compares the actual filling level with a setpoint and modifies the NH3 slip from the first converter to maintain the second converter at the desired filling level, thereby preventing both ammonia slip and ensuring high NOx conversion efficiency
Solution Approach 2:
The control system proactively adjusts the NH3 mass flow from the first SCR catalytic converter before the second converter's filling level becomes critical. By detecting deviations from the setpoint filling level and responding with appropriate NH3 slip adjustments, the system prevents ammonia slip from occurring in the first place while maintaining optimal NOx conversion conditions
2Reliability
If the control system responds only to NH3 filling level in the second SCR catalytic converter, then the system can be brought under control, but the response is delayed and overshooting occurs
Solution Approach 1:
The patent employs a feedback control mechanism that continuously monitors the NH3 filling level in the second SCR catalytic converter and adjusts the NH3 mass flow from the first converter in real-time. This closed-loop control detects deviations from the setpoint filling level and responds immediately by modulating the NH3 slip, thereby reducing response time and preventing overshooting while maintaining control stability
Solution Approach 2:
The control system dynamically adjusts the NH3 mass flow from the first SCR catalytic converter based on the current filling level in the second converter. By making the NH3 slip variable and responsive to real-time conditions rather than fixed, the system achieves faster response times and prevents overshooting while maintaining reliable 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 prevents severe overshooting of NH3 filling levels and enhances NOx performance by allowing earlier intervention in NH3 filling level adjustments, maintaining optimal NOx conversion rates with minimal NH3 slip.
Implementation Method 1
an SCR catalytic converter (selective catalytic reduction) in the exhaust region of internal combustion engines, said catalytic converter reducing nitrogen oxides contained in the exhaust gas of the internal combustion engine to nitrogen in the presence of a reducing agent
Implementation Method 2
SCR catalytic converters store a certain quantity of ammonia on their surface through absorption
Data Source
AI summary
A method (300) for operating an SCR catalytic converter system which has a first SCR catalytic converter (12) and a second SCR catalytic converter, characterized by a step of controlling (310) an NH3 mass flow after the first SCR catalytic converter (12).