ASU Compressor Control for Fast Oxyfuel Power Plant Load Response
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Solution Overview
Problem
Thermal power plants face limitations in providing rapid primary and secondary responses to changing grid demand, leading to reduced flexibility, increased operational costs, and potential grid instability, especially when operating beyond their design limits and with conventional control methods that compromise cycle efficiency and CO2 capture rates.
Innovation Solution
A dynamic control method for thermal power plants with an air separation system and liquid oxygen storage, adjusting the works power of ASU compressors in real-time to match short-term changes in grid demand, while maintaining CO2 capture rates, and coordinating with firing and CO2 compressor strategies to optimize overall system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional control methods are used to respond to grid demand changes, then the power plant can maintain basic operation, but the response speed is too slow and cycle efficiency deteriorates
Solution Approach 1:
The control system dynamically adjusts multiple parameters including ASU compressor works power, firing rate, and CO2 compressor speed in real-time based on grid demand signals. This dynamic coordination enables rapid response while maintaining optimal cycle efficiency by preventing the plant from operating in suboptimal regions.
Solution Approach 2:
The system changes operational parameters such as ASU compressor power consumption, furnace firing rate, and CO2 compression speed to rapidly adjust net power output. These parameter changes enable the plant to provide primary and secondary frequency response while maintaining efficient operation through coordinated control.
2Adaptability or versatility
If the power plant operates beyond design limits to increase flexibility, then response capability improves, but material stresses increase and plant life decreases
Solution Approach 1:
The control system adjusts operational parameters within safe design limits by coordinating ASU compressor power, firing rate, and CO2 compression. This enables the plant to provide frequency response capabilities without exceeding material stress limits, thereby maintaining plant life and reliability.
Solution Approach 2:
The control system continuously monitors plant operating conditions and adjusts control actions based on feedback signals to keep operations within safe design limits. This feedback control prevents excessive material stresses while maintaining the required flexibility for grid support services.
3Power
If ASU compressor works power is reduced to increase net power output, then grid demand response improves, but oxygen supply to the furnace may be insufficient
Solution Approach 1:
The control system coordinates changes in ASU compressor works power with corresponding adjustments in firing rate and CO2 compressor speed. This coordinated parameter change ensures that oxygen supply is reduced in proportion to the power output reduction, maintaining the correct stoichiometric balance and preventing insufficient oxygen supply to the furnace.
4Reliability
If CO2 capture rate is maintained at target level during rapid response, then environmental performance improves, but system complexity increases
Solution Approach 1:
The control system adjusts CO2 compressor speed as one of the coordinated parameters to maintain target CO2 capture rates during rapid response events. By integrating this control action with ASU and firing rate adjustments, the system maintains environmental performance through a unified control strategy rather than separate complex subsystems.
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 enhances the power plant's flexibility and ability to provide rapid responses to grid demand changes, reduces material stresses, and maintains target CO2 capture rates, leading to improved cycle efficiency, extended plant life, and reduced maintenance costs, while ensuring grid stability and commercial viability.
Implementation Method 1
the oxygen required to burn the fuel is supplied by using atmospheric air as a comburant gas. In the case of oxyfuel firing a supply of gas with a higher oxygen content, and in particular a mixture of substantially pure O2 and recycled CO2, is used as a comburant gas. To effect this, the combustion air supply must first be separated prior to supply to the furnace in a suitable air separation unit (ASU).
Implementation Method 2
Oxyfuel firing is a means of firing the fuel with an oxygen enriched comburant gas. In conventional fossil fuel fired combustion equipment for example in boilers for steam generation the oxygen required to burn the fuel is supplied by using atmospheric air as a comburant gas. In the case of oxyfuel firing a supply of gas with a higher oxygen content, and in particular a mixture of substantially pure O2 and recycled CO2, is used as a comburant gas. The oxyfuel combustion process seeks to produce combustion products that are highly concentrated in CO2
Implementation Method 3
The CO2 is not vented to atmosphere but is removed from flue gases by a suitable apparatus and as a rich CO2 gas compressed and stored away from the atmosphere.
Data Source
AI summary
A method of operation of a thermal power plant having an air separation system with a plurality of air storage unit (ASU) compressors and a liquid oxygen/liquid air (LOX/LA) storage facility for oxyfuel firing of fossil fuel and a power plant having a control system to perform the same are described. The method is characterized by the step of controlling the net power output of the plant in response to short term variations in grid demanded net plant output by dynamically adjusting the works power of the ASU compressors preferably in conjunction with co-ordinated changes in firing demand. The method is in particular a method to produce an improved primary and secondary response to transient changes in grid demand and to provide accurate response to load dispatch ramps.