HRSG Drum Level Control Using Closed-Loop Flow Multipliers
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Solution Overview
Problem
Industrial control systems for managing drum levels in heat recovery steam generation (HRSG) systems face challenges in maintaining consistent fluid flow rates due to variations in operational characteristics, leading to inefficiencies and potential equipment damage from swell and shrinkage during startup.
Innovation Solution
Implementing Closed Loop Flow Rate Control (CLFRC) that determines a variable multiplier based on the commanded and measured fluid flow rates, allowing for precise control of fluid flow rates to maintain a constant average flow rate, thereby accounting for environmental and operational variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional drum level control methods are used, then the system can operate with simple control logic, but the fluid flow rate varies significantly during operational transitions causing swell and shrinkage
Solution Approach 1:
The patent implements feedback control by continuously measuring the actual fluid flow rate through flow meters and comparing it with the commanded flow rate. The controller adjusts the fluid flow command based on the difference between commanded and measured flow rates, creating a closed-loop system that maintains stable drum levels despite operational variations.
Solution Approach 2:
The patent applies dynamic control by using a variable multiplier that changes based on operational conditions. The controller dynamically adjusts the fluid flow command using the formula: fluid flow command = commanded flow rate × variable multiplier. This dynamic adjustment allows the system to adapt to changing operational characteristics and maintain stability during transitions.
2Productivity
If the fluid flow rate is increased to improve productivity, then more steam can be generated, but the equipment experiences increased stress from rapid level changes
Solution Approach 1:
The feedback mechanism continuously monitors the actual fluid flow rate and compares it with the commanded rate. When the actual flow deviates from the commanded flow, the controller adjusts the fluid flow command to maintain the desired rate, preventing excessive stress on equipment while allowing high productivity operation.
Solution Approach 2:
The system applies preliminary anti-action by using the variable multiplier to preemptively counteract flow rate deviations before they cause significant drum level changes. The controller calculates the adjusted fluid flow command in advance to compensate for expected variations, reducing equipment stress from rapid level changes.
3Adaptability or versatility
If the control system uses fixed flow rates, then the system is easier to operate, but it cannot adapt to environmental and operational variations
Solution Approach 1:
The system uses dynamic control with a variable multiplier that automatically adjusts based on operational conditions. The controller applies the formula: fluid flow command = commanded flow rate × variable multiplier. This dynamic approach provides adaptability to environmental and operational variations while maintaining ease of operation through automated adjustment.
Solution Approach 2:
The control system performs self-service by automatically adjusting the fluid flow command using the variable multiplier without requiring manual intervention. The controller continuously calculates and applies the adjusted command based on measured flow rates, providing adaptability while maintaining operational simplicity.
Data Source
AI summary
A method includes determining, via a processor, a commanded fluid flow rate of a fluid entering or exiting the drum of an industrial system, wherein the commanded fluid flow rate comprises a rate of fluid entering the drum of the industrial system, exiting the drum of the industrial system, or a combination thereof. The method additionally includes determining, via the processor, a measured flow rate of the fluid. The method further includes determining, via the processor, a variable multiplier based at least in part on the commanded fluid flow rate and the measured flow rate; and deriving, via the processor, a multiplied flow rate command for the industrial system by applying the variable multiplier to the commanded fluid flow rate.