NOx Emission Estimation via Virtual Sensor and Time Delay Compensation
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Solution Overview
Problem
Current systems for monitoring NOx emissions, such as continuous emissions monitoring systems (CEMS) and predictive emissions monitoring systems (PEMS), are expensive, complex, and require frequent maintenance and recalibration, making them inefficient for obtaining an optimal estimate of NOx emissions in industrial processes.
Innovation Solution
A control system that combines a continuous emission monitoring sensor with a virtual sensor and a processor featuring a time delay compensation circuit and low pass filter to generate an optimal estimate of NOx emissions, which is then used as a feedforward signal in the selective catalytic reduction process, thereby improving the accuracy and efficiency of NOx emission monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If continuous emissions monitoring systems (CEMS) are used to directly measure NOx emissions, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent creates a virtual sensor that generates a copy of the continuous emission monitoring sensor's output signal using a dynamic model. This virtual copy allows the system to maintain measurement precision while reducing device complexity by eliminating or supplementing the physical CEMS hardware with a computational model that replicates its function.
Solution Approach 2:
The patent replaces the physical CEMS measurement system with a dynamic model-based virtual sensor that computes NOx emissions from engine operating parameters. This substitution eliminates the need for complex physical sensing hardware while maintaining measurement capability through mathematical modeling of the emission process.
2Measurement precision
If continuous emissions monitoring systems (CEMS) are used to directly measure NOx emissions, then measurement precision is improved, but maintenance requirements increase
Solution Approach 1:
By creating a virtual sensor that replicates CEMS functionality through dynamic modeling, the system maintains measurement precision while eliminating the physical components that require maintenance and calibration. The virtual sensor uses computational algorithms instead of physical sensors, eliminating calibration needs.
Solution Approach 2:
The virtual sensor acts as a software-based, virtually inexhaustible measurement resource that requires no physical maintenance. Unlike physical CEMS sensors that degrade and require calibration, the virtual sensor can be continuously updated and reset without physical wear or calibration requirements.
3Device complexity
If predictive emissions monitoring systems (PEMS) are used to predict NOx emissions, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent implements a dynamic model that continuously adapts to changing engine operating conditions, allowing the virtual sensor to maintain high measurement precision across varying loads and speeds. The dynamic nature of the model enables it to track real-time emission changes accurately without requiring complex hardware.
Solution Approach 2:
The system uses feedback from actual CEMS measurements to continuously update and refine the dynamic model parameters, improving the virtual sensor's prediction accuracy over time. This feedback mechanism allows the simplified PEMS approach to achieve precision comparable to or exceeding traditional CEMS while maintaining lower device complexity.
4Ease of operation
If traditional PEMS are used to predict emissions, then ease of operation is improved, but adaptability deteriorates
Solution Approach 1:
The system incorporates feedback loops where actual CEMS measurements are used to continuously adjust and refine the dynamic model parameters. This feedback mechanism enables the model to automatically adapt to real-world conditions and changing engine characteristics without requiring manual retraining or specialized staff intervention.
Solution Approach 2:
The dynamic model performs self-adjustment using feedback from the system it monitors, eliminating the need for external specialists to retrain or recalibrate the model. The system automatically adapts to changing conditions through its own operational data, maintaining both ease of operation and adaptability.
Data Source
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AI summary
A control system (10) for providing an optimal estimate of NOx emission in an exhaust during a selective catalytic reduction process is provided. The control system (10) includes a continuous emission monitoring sensor (12) configured to generate a responsive signal (14) representing a first estimate of NOx emission. The control system (10) also includes a virtual sensor (18) configured to generate a relatively faster responsive signal representing a second estimate of NOx emission. The control system (10) further includes a processor (22) that includes a time delay compensation circuit (24) configured to introduce a second time lag in the relatively faster responsive signal. The processor (22) also includes a low pass filter circuit (28) coupled to the time delay compensating circuit (24). The processor (22) is further configured to subtract the time delayed signal from the summation of the responsive signal (14) and the relatively faster responsive signal to generate the optimal estimate of the NOx emission.