Oxyfuel Power Plant ASU Compressor Control for Rapid Grid Response
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Solution Overview
Problem
Thermal power plants face limitations in providing rapid and flexible responses to short-term changes in grid demand, leading to increased operational costs, reduced plant lifetime, and decreased grid stability, especially when combined with oxyfuel firing and carbon capture technologies.
Innovation Solution
A dynamic control method for the air separation unit (ASU) compressors and liquid oxygen/liquid air storage facility, allowing for real-time adjustments in response to short-term grid demand changes, integrating with steam generation and CO2 compression systems to optimize power output and maintain CO2 capture rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional thermal power plants operate at full load continuously, then plant lifetime and operational stability are improved, but the ability to respond rapidly to short-term grid demand changes deteriorates
Solution Approach 1:
The invention applies dynamics by enabling the power plant to transition between different operational states (full load, part load, rapid ramping) through controlled variations in combustion intensity and steam flow. The system dynamically adjusts the firing rate and turbine valve positions to respond to grid demand while managing thermal stresses on equipment.
Solution Approach 2:
The invention uses preliminary action by pre-heating feedwater using waste heat from flue gases before it enters the boiler. This prepares the water for rapid vaporization when fuel is introduced, enabling faster response to load changes while reducing thermal shock to the boiler system.
2Productivity
If rapid changes in firing level are used to meet response requirements, then grid response capability is improved, but plant lifetime and maintenance costs worsen due to operation beyond design points
Solution Approach 1:
The invention applies parameter changes by systematically varying combustion parameters (fuel flow rate, air-to-fuel ratio, combustion chamber pressure) within safe operating limits. The control system adjusts these parameters in coordinated sequences that maintain thermal stresses within material design specifications, enabling rapid response without exceeding equipment ratings.
Solution Approach 2:
The invention uses beforehand cushioning by introducing feedwater that has been pre-heated to near-boiling temperature using waste heat recovery. This cushioning effect reduces the thermal shock to the boiler when rapid fuel addition occurs, protecting the system from thermal stresses that would otherwise occur with cold water injection during rapid load changes.
3Reliability
If oxyfuel firing with air separation unit is implemented, then CO2 capture efficiency is improved, but works power consumption increases due to ASU compressor operation
Solution Approach 1:
The invention applies continuity of useful action by operating the air separation unit compressors continuously at optimized load levels rather than cycling them on and off. The liquid oxygen and liquid air storage facilities buffer the system, allowing the compressors to run at steady state while meeting varying oxygen demand, thereby maintaining high CO2 capture efficiency while minimizing compressor power consumption.
Solution Approach 2:
The invention uses preliminary action by pre-storing liquid oxygen and liquid air in storage facilities during periods of low power demand or when excess oxygen is available. This preliminary storage allows the ASU compressors to operate at optimal efficiency points while meeting peak oxygen demands without requiring continuous high-power compressor operation.
4Power
If ASU compressor power is reduced to meet grid demand, then net power output increases, but oxygen supply to the combustion process may be insufficient
Solution Approach 1:
The invention applies preliminary action by pre-storing liquid oxygen in storage facilities during periods when ASU compressors operate at high capacity. When grid demand requires reduced ASU compressor power, the stored liquid oxygen is vaporized and supplied to the combustion process, ensuring adequate oxygen supply while maximizing net power output.
Solution Approach 2:
The invention uses an intermediary approach by introducing liquid air storage as a buffer between the ASU compressors and the combustion process. Liquid air can be stored and then vaporized to supplement oxygen supply when ASU compressor output is reduced, acting as a mediator that decouples oxygen supply from instantaneous compressor power output.
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 primary and secondary responses to grid demand changes without reducing CO2 capture rates, improving cycle efficiency, reducing maintenance costs, and extending plant life.
Implementation Method 1
an air separation system with a plurality of ASU compressors and a LOX/LA storage facility
Implementation Method 2
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
Only the separated gaseous oxygen is intended for supply to the combustion process
Implementation Method 4
the combustion of such fossil fuels produces a large volume of CO2 which was conventionally vented to atmosphere
Implementation Method 5
Most of the energy used in the world today is derived from the combustion of fossil fuels, such as coal, oil, and natural gas, for example in thermal power generation plants
Data Source
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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.