SCR Catalyst Control via Upstream Temperature Prediction
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Solution Overview
Problem
Existing SCR control systems face challenges in managing transient engine speeds and loads in mobile vehicles, leading to suboptimal NOx conversion and ammonia slip due to inadequate real-time adjustment of reductant injection based on catalyst temperature changes.
Innovation Solution
A control system that includes sensors to measure temperature upstream of a filtering device, predicting changes in the SCR catalyst's ability to store reduction agents and adjusting the injection of reduction agents accordingly to prevent ammonia slip and optimize NOx conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the amount of NH3 stored on the catalyst's surface is increased to maximize NOx conversion, then the NOx conversion efficiency is improved, but the NH3 desorption rate increases exponentially with catalyst temperature leading to ammonia slip
Solution Approach 1:
The control system performs preliminary action by measuring temperature upstream of the filtering device before the exhaust reaches the SCR catalyst, and adjusts the reductant injection rate in advance based on the predicted temperature change. This anticipatory control prevents ammonia slip before it occurs by proactively reducing injection when temperature increase is detected, rather than reacting after slip has already happened.
Solution Approach 2:
The system implements feedback control by continuously monitoring the upstream temperature and using this information to adjust the reductant injection rate. The controller compares the measured temperature with reference values and modifies the injection strategy accordingly, creating a closed-loop control system that adapts to changing engine conditions in real-time.
2Productivity
If the reductant injection rate is increased to improve NOx conversion under transient conditions, then the NOx conversion is improved, but the来不及 adjustment due to time lag causes ammonia slip
Solution Approach 1:
By measuring temperature upstream of the filtering device, the system obtains temperature information earlier in the exhaust flow path. This allows the control system to predict temperature changes at the SCR catalyst before they occur, enabling advance adjustment of the reductant injection rate and eliminating the time lag that causes ammonia slip during transient conditions.
Solution Approach 2:
The system adds a spatial dimension to the control strategy by measuring temperature at multiple locations - specifically upstream of the filtering device in addition to downstream. This multi-point temperature measurement provides earlier warning of temperature changes, extending the control horizon and allowing more time for injection rate adjustment.
3Power
If the catalyst temperature increases to improve reaction kinetics, then the reaction rate is improved, but the NH3 desorption rate increases exponentially causing ammonia slip
Solution Approach 1:
The control system applies preliminary anti-action by detecting temperature increases upstream and proactively reducing the reductant injection rate before the temperature rise causes excessive ammonia desorption. This counteracting action prevents the harmful effect of ammonia slip while allowing the catalyst to operate at elevated temperatures for improved reaction kinetics.
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 limits pollutant emissions by predicting and adjusting the reduction agent injection based on temperature changes, reducing ammonia slip and maintaining efficient NOx conversion even under transient engine conditions.
Implementation Method 1
The NH3 may be stored on the surface coating of the catalyst where it reacts with the NOx in the exhaust flow
Implementation Method 2
The NH3 may be stored on the surface coating of the catalyst where it reacts with the NOx in the exhaust flow to create environmentally friendly products, such as nitrogen gas (N2) and water (H2O). The chemical reactions of the SCR process
Implementation Method 3
the thermal properties of the filtering device may be such that a temperature buffer is created between exhaust flow entering the SCR device and exhaust flow leaving the filtering device
Data Source
AI summary
An emissions control system is disclosed. The emissions control system may have a power source that creates a flow of exhaust and a filtering device that receives the flow of exhaust. A first sensor may be located at or upstream of the filtering device, the first sensor being configured to measure a first temperature, and an SCR catalyst may be located downstream of the filtering device. The emissions control system may also have an injector configured to inject a reduction agent into the flow of exhaust in the presence of the SCR catalyst. The emissions control system may further have a controller in communication with the first sensor. The controller may be configured to predict a change in an ability of the SCR catalyst to store reduction agent using a measured change in the first temperature and adjust the injector according to the predicted change in the storage ability of the SCR catalyst.