CCGT Flue Gas Splitting With Electrolysis Oxygen Recirculation
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Solution Overview
Problem
Combined cycle gas turbines face high investment and energy costs due to large carbon capture and storage units required for low CO2 content in flue gas, and renewable energy sources provide intermittent power, complicating the reduction of these units' size and energy consumption.
Innovation Solution
An installation integrating a combined cycle gas turbine with a splitter to divide flue gas, a carbon capture unit for the high CO2 stream, a renewable electricity unit, an electrolysis unit for hydrogen and oxygen production, and a mixing unit to create a working fluid, allowing operation modes to optimize energy use and reduce CCS unit size and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a carbon capture and storage unit is used to capture CO2 from flue gas, then CO2 emissions are reduced, but the unit size and investment costs increase significantly
Solution Approach 1:
The flue gas stream is segmented into two separate streams: a first gas flow sent to the CCS unit for CO2 capture, and a second gas flow recycled back to the combustion chamber. This segmentation allows the CCS unit to process only a portion of the total flue gas, reducing its required size and investment costs while still achieving the desired CO2 emission reduction.
2Volume of stationary object
If flue gas is recirculated to reduce CCS unit size, then the CCS unit becomes smaller, but the working fluid temperature increases and oxygen content decreases
Solution Approach 1:
The invention changes the composition parameters of the working fluid by adding oxygen-enriched gas (from electrolysis) to compensate for the oxygen depletion caused by flue gas recirculation. This parameter change allows higher recirculation rates to be used without compromising the working fluid's oxidizing capability, thus further reducing CCS unit size while maintaining temperature control.
3Volume of stationary object
If flue gas recirculation rate is increased to reduce CCS unit size, then investment costs are reduced, but energy output decreases
Solution Approach 1:
By changing the oxygen concentration parameter in the working fluid through electrolysis-based oxygen enrichment, the system can sustain higher flue gas recirculation rates without losing oxidizing power. This parameter change maintains the energy output while allowing greater recirculation rates that reduce CCS unit size and investment costs.
4Object-generated harmful factors
If renewable electricity production units are used to power electrolysis, then carbon footprint is reduced, but production becomes intermittent and unreliable
Solution Approach 1:
The system dynamically adapts its operation by switching between renewable and conventional electricity sources for the electrolysis unit based on availability. When renewable electricity is available, it powers the electrolysis; when unavailable, conventional electricity from the grid or gas turbine fills the gap. This dynamic operation ensures continuous oxygen supply for working fluid enrichment while minimizing carbon footprint.
Solution Approach 2:
The electrolysis unit acts as an intermediary that converts electricity (from either renewable or conventional sources) into oxygen, which then serves as the working fluid additive. This intermediary approach decouples the reliability issue of renewable electricity from the oxygen supply requirement, as the electrolysis can draw from multiple electricity sources.
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
The installation produces electricity with zero CO2 emissions and reduced costs by enhancing flue gas recirculation and optimizing energy use, while maintaining flexibility with renewable energy integration.
Implementation Method 1
an electrolysis unit adapted for receiving water and electricity, and for producing a hydrogen flow and an oxygen flow
Implementation Method 2
the working fluid is first compressed, then heated in the combustion chamber of the gas turbine where the fuel gas is burnt with the working fluid as oxidizer
Implementation Method 3
the heat recovery steam generator being adapted for receiving the flow of first flue gas and producing steam
Implementation Method 4
the steam turbine being adapted for receiving the steam and producing a second mechanical power
Data Source
AI summary
An installation for producing electricity and/or mechanical power, comprising: a CCGT unit, a splitter for receiving and splitting flue gas into a first gas flow and a second gas flow, a CCS unit for receiving the first gas flow and storing CO2, a renewable electricity production unit, an electrolysis unit for producing an oxygen flow, a mixing unit for receiving the second gas flow and at least part of the oxygen flow, and for producing a working fluid of a gas turbine.The installation is configured for switching between: a first operation mode, in which the renewable electricity production unit produces renewable electricity, and the electrolysis unit uses at least some of it, a second operation mode, in which the renewable electricity production unit is idle, and the electrolysis unit uses electricity from the CCGT unit or a local grid.