Virtual Urea Composition Sensing for Real-Time N/C Ratio Control
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Solution Overview
Problem
Urea production processes face challenges in controlling composition variables like the N/C ratio due to safety risks and inaccuracies associated with manual sampling and the high cost and maintenance requirements of dedicated measurement instruments, leading to inefficiencies and instability in operations.
Innovation Solution
A virtual sensing method that estimates the N/C ratio using a model based solely on online measured process variables such as flow rate, temperature, and pressure, eliminating the need for offline composition measurements and reducing the reliance on expensive measurement instruments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual sampling and laboratory analysis are used to measure composition variables, then measurement capability is provided, but safety risks increase and measurement precision decreases due to high pressure conditions
Solution Approach 1:
The patent introduces an intermediary computational model that processes readily available process variables (temperature, pressure, flow rates) to estimate composition variables. This mediator eliminates the need for direct physical sampling under high pressure conditions, thereby removing safety risks while providing continuous composition data for process control.
Solution Approach 2:
The patent replaces the mechanical sampling and laboratory analysis system with a computational estimation system. Instead of physically extracting samples under high pressure for chemical analysis, the system uses mathematical models and process data to calculate composition variables, eliminating the harmful mechanical intervention in high-pressure zones.
2Loss of time
If dedicated measurement instruments are installed to measure composition variables in real-time, then measurement precision and response time improve, but device complexity and maintenance requirements increase
Solution Approach 1:
The patent makes existing multi-functional process measurement instruments serve an additional purpose. Temperature, pressure, and flow rate sensors already installed for process control are also used as input variables for composition estimation, eliminating the need for dedicated composition measurement instruments and reducing device complexity.
Solution Approach 2:
The patent creates a virtual copy of composition measurement capability through computational modeling. Instead of installing physical instruments to directly measure composition variables, the system generates a computational replica (estimated composition) based on relationships with other measured process variables, achieving real-time measurement without additional hardware.
3Measurement precision
If manual sampling is performed multiple times a day, then measurement capability is maintained, but productivity decreases due to extended waiting periods for laboratory results
Solution Approach 1:
The patent transforms discontinuous batch laboratory analysis into continuous real-time composition estimation. By using continuously available process variables as model inputs, the system provides uninterrupted composition data, eliminating waiting periods and enabling continuous process optimization without sacrificing measurement accuracy.
Solution Approach 2:
The patent performs preliminary computational processing of process data to predict composition variables before actual composition measurement would be available. The model continuously calculates estimated composition based on current process conditions, providing advance information for immediate process adjustment without waiting for laboratory results.
Data Source
AI summary
The invention relates to a virtual sensing method and system for controlling at least one composition variable in a urea production process, based on a plurality of online measured process variables and a model, wherein the model is used to estimate, during the urea production process, the at least one composition variable indicative of a urea content on the basis of the plurality of online measured process variables, and modifying at least one of the plurality of online measured process variables for ensuring that a value of the at least one composition variable is within a predetermined range. The invention also relates to determining the model.