CCGT Flue Gas Recirculation With Electrolysis Oxygen for Smaller CCS
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Solution Overview
Problem
Existing combined cycle gas turbine systems 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 systems have intermittent production, complicating the reduction of these units' size and energy consumption.
Innovation Solution
An installation integrating a combined cycle gas turbine with a carbon capture and storage unit, a renewable electricity production unit, and an electrolysis unit, allowing for flexible operation modes and increased flue gas recirculation with pure oxygen addition, reducing the size and energy consumption of the carbon capture unit.
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 requires large size and huge investment costs due to low CO2 content in flue gas
Solution Approach 1:
The flue gas flow is divided into two separate flows: a first gas flow sent to the CCS unit for CO2 capture, and a second gas flow recycled as working fluid. This segmentation allows the CCS unit to process only a portion of the flue gas, reducing its required size and investment costs while still achieving effective CO2 capture from the concentrated stream.
Solution Approach 2:
The CO2 concentration parameter in the gas stream is changed by selective routing. The first gas flow directed to the CCS unit has higher CO2 content than the original flue gas, which improves the efficiency and reduces the size of the capture unit. This parameter optimization allows the CCS unit to operate more effectively with smaller dimensions.
2Quantity of substance
If flue gas is recirculated as part of the working fluid, then the amount of flue gas to be treated by the CCS unit is reduced, but the temperature of the working fluid increases and oxygen content decreases
Solution Approach 1:
The temperature parameter of the recirculated second gas flow is controlled and adjusted before mixing with the primary working fluid. By optimizing the temperature of the recirculated stream, the system reduces the amount of flue gas requiring CO2 capture while preventing excessive temperature increase in the combined working fluid that would compromise turbine performance.
3Quantity of substance
If flue gas is recirculated as part of the working fluid, then the amount of flue gas to be treated by the CCS unit is reduced, but the oxygen content decreases reducing its ability to serve as an oxidizer
Solution Approach 1:
The oxygen concentration parameter in the recirculated second gas flow is managed by controlling the recirculation rate and mixing ratio. This ensures that while flue gas recirculation reduces the volume requiring CO2 capture, the oxygen content in the combined working fluid remains sufficient to maintain reliable combustion and oxidizing performance in the gas turbine.
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 achieves CO2-free electricity production at reduced costs by minimizing the carbon capture unit's size and energy consumption, while utilizing renewable energy to stabilize power output.
Implementation Method 1
an electrolysis unit (32) adapted for receiving water and electrical energy and producing a hydrogen flow and an oxygen flow
Implementation Method 2
a heat recovery steam generator, adapted for receiving the flow of first flue gas and producing steam
Implementation Method 3
the working fluid is first compressed, then heated in the combustion chamber of the gas turbine where the fuel gas is burnt
Implementation Method 4
the combustion products are expanded in the turbine part, thus producing mechanical power
Implementation Method 5
the steam turbine being adapted for receiving the steam and producing a second mechanical power
Data Source
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AI summary
An installation (10) for producing electricity (12) and/or mechanical power, comprising: - a CCGT unit (18), - a splitter (26) for receiving and splitting flue gas (68) into a first gas flow (92) and a second gas flow (94), - a CCS unit (28) for receiving the first gas flow and storing CO2, - a renewable electricity production unit (30), - an electrolysis unit (32) for producing an oxygen flow (102), - a mixing unit (34) for receiving the second gas flow and at least part of the oxygen flow, and for producing a working fluid (60) of a gas turbine (20). The installation is configured for switching between: - a first operation mode, in which the renewable electricity production unit produces renewable electricity (36), 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 (38) from the CCGT unit or a local grid (40).