Combined Cycle Plant Start-Up Control via Predictive Steam Turbine Roll-Off
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Solution Overview
Problem
Combined cycle power plants face challenges during start-up due to drastic transients, which can damage components and increase emissions, as standard start-up procedures operate gas turbines at low loads to prevent damage, leading to longer waiting times and higher emissions.
Innovation Solution
A system and method that modifies gas turbine operational parameters to increase exhaust gas temperature above standard start-up levels, using predictive control based on data from sensors to satisfy steam turbine roll-off permissives, thereby optimizing start-up conditions and reducing emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gas turbine is operated at low load during start-up, then the steam temperature is kept low to prevent damage to steam turbine components, but the start-up time increases and emissions increase
Solution Approach 1:
The system performs preliminary heating of steam turbine components using insulation blankets and heating elements before steam introduction. This pre-warming action ensures components reach safe temperatures in advance, allowing the gas turbine to operate at higher loads during start-up without causing thermal shock or damage to the steam turbine components.
Solution Approach 2:
The system introduces an intermediary heating system between the gas turbine exhaust and steam turbine components. This intermediary system includes electric heating elements and insulation blankets that independently control component temperatures, decoupling the gas turbine operation from direct thermal impact on steam turbine components, thereby enabling higher gas turbine loads during start-up.
2Reliability
If the gas turbine is operated at low load during start-up, then the steam temperature is kept low to prevent damage to steam turbine components, but emissions increase
Solution Approach 1:
The system performs preliminary heating of steam turbine components using insulation blankets and heating elements before steam introduction. This pre-warming action ensures components reach safe temperatures in advance, allowing the gas turbine to operate at higher loads during start-up without causing thermal shock or damage to the steam turbine components.
Solution Approach 2:
The system introduces an intermediary heating system between the gas turbine exhaust and steam turbine components. This intermediary system includes electric heating elements and insulation blankets that independently control component temperatures, decoupling the gas turbine operation from direct thermal impact on steam turbine components, thereby enabling higher gas turbine loads during start-up.
3Productivity
If the gas turbine is operated at higher load during start-up, then emissions decrease and start-up time is reduced, but the steam temperature may exceed safe limits for steam turbine components
Solution Approach 1:
The system implements a feedback control mechanism that continuously monitors steam turbine component temperatures using sensors and thermocouples. The control system receives real-time temperature data and dynamically adjusts gas turbine operational parameters and heating element power levels to maintain component temperatures within safe operating limits, enabling high-load start-up operations while ensuring component safety.
Solution Approach 2:
The system transitions from static, fixed operational procedures to dynamic, adaptive control during start-up. The gas turbine operational parameters and heating element power levels are continuously adjusted based on real-time component temperature measurements, allowing the system to optimize start-up efficiency while maintaining component safety throughout the transient 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
This approach reduces start-up time, lowers fuel consumption, and decreases emissions by operating the gas turbine at higher loads while ensuring safe and efficient steam turbine operation, matching steam temperature with turbine components to prevent damage.
Implementation Method 1
The thermal energy of the exhaust gas is used to generate steam in the HRSG
Data Source
AI summary
In accordance with one aspect of the present technique, a method is disclosed. The method includes modifying one or more operational parameters of a gas turbine (GT) to increase an exhaust gas temperature above a standard start-up temperature. The method also includes receiving at least one of GT operational data, heat recovery steam generator (HRSG) operational data, and steam turbine (ST) operational data from a plurality of sensors. The method further includes predicting a ST roll-off time based on at least one of the GT operational data, the HRSG operational data, and the ST operational data. The method further includes modifying the one or more operational parameters of the GT to satisfy one or more ST roll-off permissives at the predicted ST roll-off time.