Gas Turbine CO2 Capture via Recirculation and High-Pressure Separation
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Solution Overview
Problem
Current CO2 capture methods in power plants using fossil fuels are energy-intensive and costly due to low CO2 partial pressures in flue gas, requiring large and expensive equipment for post-combustion capture.
Innovation Solution
The process involves recirculating flue gas to increase CO2 concentration and partial pressure within the gas turbine's compression pathway, allowing for CO2 separation at higher pressures, reducing energy penalties and equipment size through a two-stage compression system with a CO2 separator and expander configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If post-combustion CO2 capture is implemented using conventional methods, then CO2 removal is achieved, but the equipment becomes very large and costly
Solution Approach 1:
The invention changes the pressure parameter of the CO2 separation process from atmospheric pressure to high pressure (up to 200 bar). This parameter change fundamentally alters the separation dynamics, enabling compact equipment design while maintaining high CO2 removal efficiency. The high-pressure environment allows for smaller equipment volumes compared to conventional atmospheric-pressure capture methods.
Solution Approach 2:
The compression system is divided into two independent compressors (first and second compressors) that operate in parallel. This segmentation allows for more flexible system design and optimization, enabling the system to handle large gas volumes efficiently while keeping individual equipment components more manageable in size.
2Quantity of substance
If post-combustion CO2 capture is implemented using conventional methods, then CO2 removal is achieved, but energy consumption becomes very high
Solution Approach 1:
The invention changes the operating pressure parameter to high pressure, which fundamentally alters the energy requirements of the separation process. At high pressure, the partial pressure differential driving the separation is much larger, reducing the energy penalty associated with CO2 capture. The system achieves over 80% CO2 capture efficiency while controlling energy consumption through optimized high-pressure operation.
Solution Approach 2:
The system continuously recirculates the gas stream through the compressors and separation units, maintaining high CO2 concentration and partial pressure throughout the process. This continuous operation at high pressure ensures consistent CO2 removal efficiency while optimizing energy consumption through sustained high-pressure conditions that favor the separation process.
3Stress or pressure
If flue gas is recirculated to increase CO2 concentration, then CO2 partial pressure increases, but the system complexity increases
Solution Approach 1:
The recirculated gas serves multiple functions simultaneously: it increases CO2 partial pressure for the separation process, provides a heat transfer medium for the compressors, and maintains system pressure. This multi-functionality reduces the need for additional separate systems, thereby limiting the increase in overall system complexity despite the added recirculation pathway.
Solution Approach 2:
The recirculated flue gas acts as an intermediary medium that facilitates the CO2 separation process. By introducing this recirculated stream, the system achieves high CO2 partial pressure without requiring direct high-pressure compression of the entire flue gas stream, thus managing complexity through strategic intermediation.
4Quantity of substance
If conventional CO2 capture methods are used, then CO2 is removed from flue gas, but the process becomes very energy intensive
Solution Approach 1:
The invention fundamentally changes the energy intensity by operating at high pressure (up to 200 bar), which alters the thermodynamic and kinetic parameters of the CO2 separation process. At these high pressures, the separation process becomes more efficient and less energy-intensive compared to conventional atmospheric-pressure methods, while achieving over 80% CO2 capture efficiency.
Solution Approach 2:
The system performs preliminary compression of the gas stream to high pressure before the CO2 separation process. This preliminary action prepares the gas in an optimized state for separation, reducing the overall energy intensity of the subsequent CO2 removal process by establishing favorable pressure conditions in advance.
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 achieves significant reductions in energy and capital costs for CO2 capture, enabling over 80% CO2 capture efficiency with smaller equipment and lower energy requirements, while allowing for alternative capture methods like adsorption and membrane separation.
Implementation Method 1
the CO2 produced during the combustion is removed from the exhaust gases by an absorption process
Implementation Method 2
adsorption process
Implementation Method 3
membranes
Implementation Method 4
uses a compressor to compress the inlet air upstream of a combustion chamber
Implementation Method 5
the fuel is introduced and ignited to produce a high temperature, high-pressure gas that enters and expands through the turbine section
Implementation Method 6
the fuel is introduced and ignited to produce a high temperature, high-pressure gas
Data Source
AI summary
Power plants and process for lowering CO2 emissions generally includes extracting a portion of the recirculated CO2-rich flue gas mid-way through the compression pathway of a gas turbine and removing the CO2 in a separation unit. The remaining portion of the CO2 rich flue gas (i.e., the portion of the recirculated flue gas that was not fed to the separation unit) is mixed with fresh air coming from an additional compressor-expander and then fed back to the compression pathway. As a result, flue gas recirculation increases the CO2 concentration within the working fluid, leading to an additional increase in CO2 partial pressure. As the concentration and partial pressure of CO2 is increased, a lower energy penalty is observed to remove the CO2. Moreover, a reduced volume is fed to the CO2 separation unit during operation. Consequently, the size of the separation equipment can be reduced as well as the energy required for the separation process.