Combined Cycle Plant Load Control via Bypass Valve Segmentation
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Solution Overview
Problem
Combined cycle power plants face poor load followability due to fluctuations in gas turbine and steam turbine loads, leading to unstable steam generation and inefficient energy conversion.
Innovation Solution
A combined cycle plant with a gas turbine, heat recovery steam generator, steam turbine, and bypass line, controlled by a unit that adjusts fuel and steam valves to regulate load fluctuations, allowing for earlier and more stable adjustments in steam supply to the steam turbine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the steam turbine load follows gas turbine load fluctuations, then the overall plant load follows, but the steam turbine has poor load followability due to delayed steam generation response
Solution Approach 1:
The bypass line allows steam to be diverted from the main steam line before it reaches the steam turbine when load decrease is required. This preliminary diversion of steam enables the steam turbine load to decrease immediately without waiting for the heat recovery steam generator to reduce steam production, thus improving load followability and reducing response time.
2Productivity
If the fuel regulating valve adjusts fuel supply to match target load, then the gas turbine load changes, but the steam turbine load lags behind due to thermal inertia in steam generation
Solution Approach 1:
The steam supply system is segmented into two paths: the main steam line for normal operation and the bypass line for rapid load adjustment. This segmentation allows independent control of steam flow to the steam turbine, enabling quick load changes without disrupting the overall steam generation process in the heat recovery steam generator.
Solution Approach 2:
The bypass line acts as an intermediary mechanism between the main steam line and the steam turbine. It provides a direct control path that bypasses the thermal inertia of the heat recovery steam generator, allowing rapid adjustment of steam supply to the steam turbine while maintaining stability in the main steam generation system.
3Speed
If the bypass valve remains open during load decrease, then steam turbine load follows quickly, but steam flow instability occurs without gradual adjustment
Solution Approach 1:
The bypass valve opening degree is dynamically adjusted based on the required load change. The control unit gradually changes the bypass valve opening from its initial position to the target position, enabling the steam turbine load to follow the target load smoothly and stably while maintaining steam flow stability throughout the transition process.
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
Improves the followability of the steam turbine to overall load fluctuations, stabilizing the load of both the gas and steam turbines, and enhances energy conversion efficiency by allowing earlier adjustments in steam supply.
Implementation Method 1
a heat recovery steam generator which generates steam by recovering heat of exhaust gas discharged from a gas turbine
Implementation Method 2
a steam turbine that is rotated using the steam generated by the heat recovery steam generator
Implementation Method 3
a turbine which is rotated using combustion gas generated by the combustor
Implementation Method 4
a combustor to which fuel is supplied from a fuel supply line so as to combust the air compressed by the compressor
Data Source
AI summary
A gas turbine combined cycle (GTCC) power generation plant (100) equipped with a control unit which performs a load reduction following operation with respect to a fuel adjustment valve (Vd), a main steam valve (V1), and a bypass valve (V4), wherein, when a load reduction request for reducing a GTCC load target value has been input in a closed bypass operation, the degree of opening of the fuel adjustment valve (Vd) is reduced in accordance with the target value while the main steam valve (V1) is in an open state, and the bypass valve (V4) is placed in an open state, after which the bypass valve (V4) is placed in the closed state when the GTCC load reaches the target value.