Injection Cooling for Flexible Power Plant Operation
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Solution Overview
Problem
Modern power plants face challenges in maintaining the rate of change of fresh steam and intermediate superheater steam temperatures within permissible limits during load reduction or complete shut-off of auxiliary firing, which can lead to excessive stress on the steam turbine, compromising flexibility and efficiency.
Innovation Solution
A method is introduced where at least one injection cooling device is brought online simultaneously with the auxiliary firing, allowing for continuous regulation of steam temperatures by increasing the injection quantity as auxiliary firing power increases, and maintaining constant temperatures throughout the load range by coupling setpoint temperatures to actual measurements, ensuring safe operation and extended turbine service life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the auxiliary firing is switched off to reduce load, then the power plant flexibility is improved, but the steam temperature rate of change exceeds permissible limits causing turbine stress
Solution Approach 1:
The injection cooling device is activated in advance together with the auxiliary firing switch-on, and remains in operation throughout the entire load range. This preliminary action ensures that when the auxiliary firing is subsequently reduced or switched off, the cooling device can immediately counteract rapid temperature increases, maintaining steam temperature rate of change within permissible limits and preventing turbine stress.
Solution Approach 2:
The system continuously monitors steam temperatures and adjusts the injection cooling device operation accordingly. The control system responds to temperature deviations by modulating the cooling injection, creating a feedback loop that maintains temperature stability during auxiliary firing load changes, thereby preventing excessive turbine stress while preserving plant flexibility.
2Temperature
If the injection cooling device is used to counter rapid temperature increase, then the steam temperature is controlled, but the injection quantity cannot be reduced infinitely causing temperature slide
Solution Approach 1:
The injection cooling device operates continuously throughout the entire auxiliary firing load range, providing uninterrupted temperature control. This continuous operation eliminates gaps in temperature regulation that would occur if the device were switched off, ensuring that steam temperatures remain controllable even when auxiliary firing is reduced or switched off, thereby preventing temperature slides.
3Productivity
If the auxiliary firing power is increased quickly to meet grid demand, then the power output is increased, but the steam temperature rate of change exceeds maximum permissible rates
Solution Approach 1:
The injection cooling device is activated simultaneously with the auxiliary firing switch-on to preemptively counteract the rapid temperature increase that would otherwise occur. This preliminary anti-action allows the auxiliary firing power to be increased quickly to meet grid demand while the cooling device prevents the steam temperature rate of change from exceeding maximum permissible rates, thus protecting the turbine.
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 method allows for flexible operation of the power plant by maintaining constant steam temperatures over the entire load range of auxiliary firing, preventing turbine stress and ensuring high plant flexibility while minimizing efficiency losses and material wear.
Implementation Method 1
at least one injection cooling device is brought on-line directly upon using the auxiliary firing
Implementation Method 2
an auxiliary firing is arranged within the flue gas duct of a waste heat steam generator in the region of the heat exchanger stages which serve as superheaters or intermediate superheaters
Data Source
AI summary
A method for flexible operation of a power plant having a recovery steam generator having heat exchanger stages for generating live steam and/or reheater steam for a steam turbine from an exhaust flow of a gas turbine, wherein auxiliary firing is arranged in a flue gas channel of the recovery steam generator in the region of the heat exchanger stages. In order to regulate the live steam and/or the reheater steam, at least one injection cooling device is brought online directly upon using the auxiliary firing.