SCR Dosing Control via NOx Sensor Cross-Sensitivity Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current exhaust treatment systems face challenges in accurately controlling the injection of dosing agents, such as ammonia, into selective catalytic reduction (SCR) catalysts due to cross-sensitivity issues with NOx sensors and variations in exhaust flow, leading to suboptimal NOx conversion rates and potential NH3 slip.
Innovation Solution
A dosing control system that includes an SCR analysis module, dosing management module, adjustment module, and error module to estimate ammonia storage, control dosing agent injection, and adjust parameters based on cross-sensitivity and delay periods, ensuring optimal NOx conversion and minimizing NH3 slip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If dosing agent injection is controlled based on traditional NOx sensor readings downstream of SCR catalyst, then NOx conversion rate can be optimized, but measurement precision is compromised due to sensor cross-sensitivity to NH3 and exhaust flow variations
Solution Approach 1:
The patent introduces an intermediary correction model that mediates between the raw sensor reading and the actual NOx concentration. This model uses upstream NOx sensor data, exhaust flow rate, and SCR catalyst characteristics to calculate correction factors that compensate for cross-sensitivity to NH3 and exhaust flow variations, thereby recovering measurement precision while maintaining optimized NOx conversion control.
Solution Approach 2:
The patent implements a feedback mechanism where downstream NOx sensor readings are continuously compared with predicted values based on upstream sensor data and SCR catalyst performance models. The difference (error signal) is used to adjust dosing agent injection rates and refine the correction model, creating a closed-loop system that maintains measurement precision despite sensor cross-sensitivity and exhaust flow variations.
2Productivity
If dosing agent injection is increased to maximize NOx conversion, then NOx conversion rate improves, but NH3 slip increases due to insufficient control precision
Solution Approach 1:
The patent applies dynamic control by continuously adjusting dosing agent injection rates based on real-time exhaust flow rate measurements and varying SCR catalyst characteristics. The system adapts injection parameters dynamically rather than using fixed rates, allowing optimization of NOx conversion while preventing NH3 slip through responsive adjustment to changing operating conditions.
Solution Approach 2:
The patent changes multiple parameters simultaneously including dosing agent injection rate, exhaust flow rate compensation factors, and correction model coefficients. By coordinating changes in these parameters rather than adjusting them independently, the system achieves high NOx conversion while maintaining precise control to prevent NH3 slip.
3Adaptability or versatility
If exhaust flow rate varies due to engine operating conditions, then system adaptability improves, but measurement precision deteriorates due to flow-induced sensor reading errors
Solution Approach 1:
The patent uses exhaust flow rate as a dynamic correction parameter that adjusts sensor readings in real-time. The system changes the interpretation of sensor readings based on actual exhaust flow conditions, applying flow-dependent correction factors that compensate for flow-induced measurement errors while maintaining adaptability to varying engine operating conditions.
Solution Approach 2:
The patent implements feedback control where exhaust flow rate measurements are used to continuously refine correction models and adjust dosing strategies. The system learns from flow variations and adjusts parameters accordingly, maintaining measurement precision despite the adaptability required to handle varying engine operating conditions.
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
The system effectively maximizes NOx conversion rates while minimizing NH3 slip by accurately controlling dosing agent injection, accounting for sensor cross-sensitivity and exhaust flow dynamics, thereby improving the efficiency of exhaust treatment systems.
Implementation Method 1
NH3 provided by the dosing agent is absorbed by the SCR catalyst 120
Implementation Method 2
NH3 reacts with NOx in the exhaust passing the SCR catalyst 120
Data Source
AI summary
A dosing control system comprises a selective catalytic reduction (SCR) analysis module, a dosing management module, an adjustment module, and an error module. The SCR analysis module estimates ammonia (NH3) stored by an SCR catalyst, a maximum NH3 storage capacity of the SCR catalyst, and a nitrogen oxides (NOx) measurement for a NOx sensor downstream of the SCR catalyst. The dosing management module controls dosing agent injection upstream of the SCR catalyst based on the maximum NH3 storage capacity and the NH3 stored. The adjustment module outputs an adjusted estimate of the NOx measurement based on the estimate of the NOx measurement, cross-sensitivity of the NOx sensor, and a delay period for exhaust flow. The error module selectively adjusts at least one of the NH3 stored and the maximum NH3 storage capacity based on a difference between the adjusted estimate and NOx measured by the NOx sensor.