HRSG Drum Water Level Control via Characteristic Chart Model
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Solution Overview
Problem
The rapid water level rise in the boiler drum during start-up operations of a combined cycle power plant's HRSG system poses safety issues and efficiency challenges due to the abrupt evaporation of water when heated by gas turbine exhaust gases, requiring precise control to prevent equipment damage and minimize heat losses.
Innovation Solution
A method and system for controlling the boiler drum water level using a characteristic chart model based on drum geometry, vapor pressures, and metal temperatures, which involves measuring actual water levels, vapor pressures, and metal temperatures to determine an optimum water level and adjust it by adding or blowing down water, while also managing gas turbine load to prevent swelling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If water is added to maintain drum water level, then water level stability is improved, but heat loss increases due to cold water injection
Solution Approach 1:
The system predicts future water level changes by analyzing current trends and operational parameters before the actual level deviation occurs. This allows proactive adjustment of water addition rates, ensuring stability while minimizing the need for corrective actions that would cause heat loss.
Solution Approach 2:
The control system continuously monitors water level, steam generation rate, and operational parameters, using this feedback to dynamically adjust the water addition rate. This closed-loop control ensures water level stability while optimizing the timing and amount of water addition to minimize heat loss from cold water injection.
2Reliability
If water level is lowered in advance to prevent swelling, then equipment safety is improved, but steam generation efficiency decreases
Solution Approach 1:
The system dynamically adjusts the water level setpoint based on real-time operational conditions, steam generation rate, and predicted load changes. This dynamic approach replaces static pre-lowering with adaptive control that maintains optimal water levels for both safety and efficiency under varying conditions.
Solution Approach 2:
The control system changes operational parameters including water level setpoint, water addition rate, and steam generation targets based on predicted operational scenarios. This allows the system to prevent swelling through parameter optimization rather than conservative water level reduction, maintaining steam generation efficiency.
3Measurement precision
If complex control algorithms are implemented to optimize water level, then control precision is improved, but system complexity increases
Solution Approach 1:
The system uses readily available operational data from existing sensors and plant instrumentation to perform predictions and control adjustments. By leveraging existing measurements and simple predictive relationships, the system achieves high control precision without requiring complex external measurement systems or elaborate control algorithms.
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
This approach allows for efficient and safe control of the boiler drum water level during start-up, minimizing heat losses and preventing equipment damage by determining the optimal water level and adjusting it accordingly, thus ensuring stable operation of the HRSG system.
Implementation Method 1
when the water in the HRSG system is heated with the high temperature gas turbine exhaust gases
Implementation Method 2
evaporation starts suddenly
Implementation Method 3
the boiler drum provides a stable water supply to the HRSG system and accumulates heat energy for compensating for changes in the amount of steam generated or consumed
Data Source
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AI summary
A method for controlling a water level of a drum (34) of a heat recovery steam generation system (12) for a combined cycle power plant (10) is provided. The method includes determining an optimum drum water level during start up operation of the heat recovery steam generation system (12) based on a characteristic chart model (100). The characteristic chart model (100) is generated based on a plurality of vapor pressures of the drum (34) and a plurality of temperatures of drum metal at the time of the start up operation of the heat recovery steam generation system (12).