Thermally Decoupled Servo Metering Valve for Steam Attemperation
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Solution Overview
Problem
Attemperators in power plants face reliability issues due to high temperature and pressure, leading to thermal fatigue, plugging of HRSG tubing, and reduced operational control, especially during flexible operations, and current designs lack precise control over cooling water injection.
Innovation Solution
A metering valve system with a thermally decoupled servo-valve and a discharge valve, designed to minimize fluid loss and enhance control, allowing for precise injection of cooling water into superheated steam streams, using a 4-way, 2-position valve configuration and throttle plates for optimal control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single valve controls multiple nozzles, then device complexity is reduced, but measurement precision and control precision deteriorate
Solution Approach 1:
The system divides the control function by providing a separate metering valve for each nozzle, allowing independent control of cooling water flow to each nozzle. This segmentation enables precise control of the amount of cooling water injected into the steam stream, resolving the contradiction between device complexity and control precision.
2Device complexity
If the servo-valve is positioned close to the metering valve, then device complexity is reduced, but the servo-valve is exposed to high temperature causing thermal fatigue and reliability issues
Solution Approach 1:
The servo-valve is extracted from the high-temperature environment by positioning it remotely from the metering valve and nozzle assembly. This separation removes the servo-valve from the harmful thermal conditions that cause thermal fatigue, thereby improving reliability while maintaining a manageable device configuration.
Solution Approach 2:
A control line or piping system acts as an intermediary between the remotely positioned servo-valve and the metering valve, transmitting control signals or fluid pressure without direct thermal contact. This intermediary enables the servo-valve to control the metering valve from a thermally safe location.
3Adaptability or versatility
If downstream piping length is reduced, then plant design flexibility is improved, but adequate mixing and thermal quenching cannot be ensured
Solution Approach 1:
The system employs high-velocity injection of cooling water through precisely controlled nozzle design to create intense mixing and rapid thermal quenching in a compact space. The kinetic energy of the injected water provides the mixing action traditionally achieved through long piping, enabling adequate steam composition uniformity with reduced downstream piping length.
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 improves the reliability and precision of attemperation, enabling better handling of flexible operations and reducing thermal damage to the servo-valve, while minimizing fluid loss and ensuring efficient mixing without the need for long downstream piping.
Implementation Method 1
the servo-valve is decoupled from the metering valve to thermally distance the servo-valve from any heat from the fluid passing through the metering valve
Implementation Method 2
The cooling water evaporates using the excess heat from the superheated steam, thus reducing the overall steam temperature
Implementation Method 3
The cooling water evaporates using the excess heat from the superheated steam
Data Source
AI summary
The present invention is directed to a metering valve for controlling the amount of a fluid passed through the valve and a servo-valve for controlling the metering valve, wherein the servo-valve is decoupled from the metering valve to thermally distance or thermally isolate the servo-valve from any heat from the fluid passing through the metering valve. The metering valve and servo-valve may be used to attemperate a steam stream in a power plant attemperation system, such as a system for attemperating a superheated steam gas stream from a power plant being used for a heat-recovery steam generator. An integrated metering valve and discharge valve for discharging fluid during periods of non-use is also provide. Changeable throttle plates are also provided that control the flow of the fluid through the control chamber of the metering valve and the discharge valve.