SCR Catalytic Converter Ammonia Dosing Control
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Solution Overview
Problem
Existing methods for operating exhaust gas treatment systems with SCR catalytic converters face challenges in accurately determining the ammonia feed rate, leading to underdosing or overdosing, which reduces treatment effectiveness and increases ammonia slip due to parameter changes over time.
Innovation Solution
A method that involves a computer model to calculate the ammonia filling level and dosing rate, with adjustable long-term and short-term adaptation factors to correct the dosing rate based on actual filling levels and emission values, ensuring optimal ammonia storage and catalytic converter efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a model-based combination of measurement values and stored characteristic values is used to determine NH3 filling level and control dosing rate, then the NH3 filling level and catalytic converter efficiency can be optimized, but errors caused by parameter changes accumulate over time leading to dosing errors and reduced treatment effectiveness
Solution Approach 1:
The patent implements a feedback mechanism where the measured NH3 filling level from sensors is continuously compared with the modeled NH3 filling level. Based on this comparison, the dosing rate is adjusted to correct deviations caused by parameter changes over time. This closed-loop control ensures that accumulated errors are compensated and the catalytic converter maintains optimal efficiency.
2Productivity
If the NH3 feed rate is increased to ensure sufficient ammonia storage in the catalytic converter, then the nitrogen oxide conversion is improved, but ammonia slip increases due to overdosing
Solution Approach 1:
The system uses real-time feedback from NH3 sensors to monitor the actual ammonia filling level in the catalytic converter. The control unit adjusts the dosing rate dynamically to maintain the filling level within optimal boundaries, preventing both underdosing (which would reduce NOx conversion) and overdosing (which would cause ammonia slip).
Solution Approach 2:
The patent dynamically adjusts the dosing rate parameter based on the measured NH3 filling level and operating conditions. By changing the dosing rate in response to real-time measurements, the system optimizes nitrogen oxide conversion while preventing ammonia slip through precise parameter control.
3Object-generated harmful factors
If the NH3 feed rate is decreased to avoid ammonia slip, then ammonia emission is reduced, but nitrogen oxide conversion effectiveness is compromised due to underdosing
Solution Approach 1:
The feedback control system continuously monitors the NH3 filling level and adjusts the dosing rate to maintain optimal operation. This ensures that the system does not underdose (which would compromise NOx conversion) nor overdose (which would cause ammonia slip), by dynamically finding the optimal dosing rate based on real-time measurements.
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 allows for precise adjustment of ammonia levels and dosing rates, compensating for short-term and long-term disturbances, thereby enhancing nitrogen oxide conversion and maintaining optimal catalytic converter efficiency.
Implementation Method 1
catalytically supported removal of nitrogen oxides (NOx) from internal combustion engine exhaust gases
Implementation Method 2
NH3 is released as the actual selective reducing agent with regard to the NOx reduction at a so-called SCR catalytic converter by means of thermolysis and/or hydrolysis
Implementation Method 3
NH3 is released as the actual selective reducing agent with regard to the NOx reduction at a so-called SCR catalytic converter by means of thermolysis and/or hydrolysis
Data Source
AI summary
In a system with an SCR catalytic converter, a correction by a changeable long term adaption factor to a target dosing rate is provided for the model dosing rate and a correction by a changeable short term adaption factor to an assumed actual filling state for the ammonia filling level value. A dosing unit controllable by a control unit adds an ammonia-containing reducing agent to the exhaust gas and an exhaust gas enriched with ammonia according to the dosing is fed to the SCR catalytic converter. An ammonia filling level value for a filling level of ammonia stored in the SCR catalytic converter and a model dosing rate for dosing the reducing agent into the exhaust gas are calculated by a computer model.