Gas Turbine Recirculation Control via Feedforward Feedback
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Solution Overview
Problem
Existing gas turbine power plants with exhaust gas recirculation face challenges in accurately and quickly controlling the concentration of components like oxygen and carbon dioxide due to the large volumes and dead times of exhaust gas lines, leading to inefficiencies in NOx emission reduction and carbon dioxide removal processes.
Innovation Solution
A method and system that utilize a closed control loop with feedforward and feedback mechanisms, including an exhaust gas divider and recirculation control elements like flaps or blowers, to adjust the recirculation flow based on setpoint concentrations determined by combustion process variables, incorporating correction values to adapt to actual system behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If exhaust gas recirculation is used to reduce NOx emissions and control gas composition, then emission reduction and combustion optimization are improved, but the large volume of exhaust gas lines and recirculation systems causes slow and inaccurate feedback control
Solution Approach 1:
The patent applies feedforward control by calculating the required recirculation flow rate in advance based on measured gas composition (O2, CO2 concentrations) and predetermined control characteristics. This preliminary calculation allows the system to adjust the recirculation flow proactively before deviations occur, rather than waiting for feedback from the large-volume exhaust gas lines which causes delays. The control unit determines the recirculation flow rate as a function of measured values and control characteristics, enabling timely response.
2Device complexity
If simple feedback control systems are used in exhaust gas recirculation, then system complexity is reduced, but control accuracy and responsiveness deteriorate due to large volumes and dead times
Solution Approach 1:
The patent combines feedback control with feedforward control to achieve accurate gas composition control. The system continuously measures actual gas composition (O2 and CO2 concentrations) and compares it with target values, then uses this feedback information to adjust the recirculation flow rate. The control unit calculates the recirculation flow rate based on measured values, target values, and control characteristics, ensuring precise control of NOx emissions and combustion efficiency despite the large volumes in the exhaust gas system.
3Productivity
If exhaust gas recirculation ratio is increased to control component concentrations, then NOx emissions and combustion efficiency are improved, but system responsiveness and control accuracy deteriorate due to dead times in recirculation lines
Solution Approach 1:
The system performs preliminary calculation of the required recirculation flow rate based on currently measured gas composition and predetermined control characteristics. This allows the control system to determine the optimal recirculation ratio in advance, adjusting it proactively to maintain combustion efficiency and control NOx emissions without waiting for the delayed feedback from the recirculation lines.
Solution Approach 2:
The system continuously monitors actual gas composition (O2 and CO2 concentrations) and uses this feedback to dynamically adjust the recirculation flow rate. By combining real-time measurement with control characteristics, the system maintains accurate control of combustion efficiency and emission levels despite the inherent dead times in the recirculation system.
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 enables rapid and accurate control of gas turbine operating conditions, optimizing combustion efficiency and reducing NOx and CO2 emissions by precisely managing oxygen and carbon dioxide concentrations, thus enhancing the overall performance of gas turbine power plants.
Implementation Method 1
a significant proportion of the exhaust gas is diverted from the overall exhaust gas flow and, typically after cooling and cleaning, is fed to the inlet mass flow of the gas turbine or the compressor, the recirculated exhaust gas flow being mixed with fresh air
Implementation Method 2
an exhaust gas re-cooler
Data Source
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AI summary
The invention relates to a method for operating a gas turbine power plant (38) with exhaust gas recirculation. In the method a setpoint concentration of one component (Cc ) of the inlet gas (3) and/or of the hot working gas and/or of the exhaust gas of the gas turbine (8, 19, 20, 21, 24) is determined in a first step, in accordance with the operating conditions of the gas turbine (6), from a combination of a setpoint value of a control loop, a feedforward control signal and a correction value. In a second step, the position of a control element (11, 29) is adjusted in accordance with the setpoint/actual deviation in the concentration of the component. The invention furthermore relates to a gas turbine power plant for carrying out the method.