Fuel Cell Cooling via Recirculated Exhaust Gas
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Solution Overview
Problem
In power generation systems combining fuel cells and gas turbines, it takes a long time to cool the fuel cell when it is stopped, as the supply of compressed air from the gas turbine is halted, leading to inefficient cooling due to high operating temperatures.
Innovation Solution
A power generation system with a fuel gas recirculation line and a cooler that operates when the fuel cell is stopped, using the recirculated exhausted fuel gas to cool the fuel cell, and additional features like a reductant supply line and purge gas line to maintain a reducing atmosphere and prevent oxidation, ensuring efficient cooling and protection of the fuel cell components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the fuel cell is stopped and separated from the gas turbine, then the fuel cell can be inspected or maintenance can be performed, but the supply of compressed air from the compressor is stopped and it takes a long time to cool the fuel cell
Solution Approach 1:
The patent introduces a recirculation blower as an intermediary device that circulates exhaust gas from the fuel cell through a cooling heat exchanger and back to the fuel cell inlet. This mediator enables continuous cooling of the fuel cell even when the gas turbine compressor is stopped, thereby resolving the contradiction between stopping the fuel cell for inspection and maintaining efficient cooling.
Solution Approach 2:
The patent extracts the cooling function from the gas turbine compressor system and creates an independent cooling circulation system using the recirculation blower. This allows the cooling function to operate independently from the compressor, enabling the fuel cell to be stopped for inspection while maintaining continuous cooling through the separate recirculation path.
2Productivity
If the gas turbine and fuel cell are stopped at the same time, then power generation can be halted, but supply of compressed air from the gas turbine is stopped and it takes a long time to cool the fuel cell
Solution Approach 1:
The recirculation blower acts as a mediator that maintains cooling circulation independently of the gas turbine operation. When both the gas turbine and fuel cell are stopped, the recirculation blower continues to circulate exhaust gas through the cooling heat exchanger, providing continuous cooling without relying on the gas turbine compressor.
Solution Approach 2:
The system establishes a preliminary cooling circulation path that can operate independently before the gas turbine is stopped. The recirculation blower and cooling heat exchanger are pre-configured to provide continuous cooling, so when the gas turbine stops, the cooling function is already in place and continues without interruption.
3Loss of time
If a method is used to reduce the operation temperature of the fuel cell and stop the fuel cell under a state in which the fuel cell and gas turbine are operated in cooperation, then cooling time can be reduced, but the temperature of the compressed air supplied through the compressor outlet is about 300 to 450°C and the fuel cell cannot be cooled lower than that temperature
Solution Approach 1:
The cooling heat exchanger serves as a mediator that removes heat from the recirculating exhaust gas and transfers it to a cooling medium (such as water). This intermediary heat transfer mechanism enables the fuel cell to be cooled below the temperature of the compressed air by using a separate cooling circuit that can achieve lower temperatures through the heat exchanger.
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 system allows for prompt cooling of the fuel cell when stopped, improving cooling efficiency and preventing deterioration by using recirculated cooled fuel gas and maintaining a reducing atmosphere, thus extending the fuel cell's lifespan.
Implementation Method 1
a cooler provided in the fuel gas recirculation line; and a control unit adapted to operate the cooler when the control unit has stopped the fuel cell and has cut the compressor and the second compressed oxidant supply line
Data Source
AI summary
A gas turbine including a compressor and a combustor, an SOFC including an air electrode (cathode) and a fuel electrode (anode), a first compressed air supply line adapted to supply a compressed air compressed by the compressor to the combustor, a second compressed air gas supply line adapted to supply a part of a compressed air compressed by the compressor to the air electrode (cathode), a first fuel gas supply line adapted to supply a fuel gas to the combustor, a second fuel gas supply line adapted to supply a fuel gas to the fuel electrode (anode), a fuel gas recirculation line adapted to return an exhausted fuel gas discharged from the fuel electrode (anode) to the fuel electrode (anode), a cooler provided in the fuel gas recirculation line are provided.