Fuel Cell Recirculation Complex for Carbon Deposition Prevention
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Solution Overview
Problem
Solid-oxide fuel cells (SOFCs) face challenges in maintaining a high steam-to-carbon ratio, leading to carbon deposition and reduced efficiency, especially near the inlet, which can cause damage and require frequent maintenance, and there is a need to increase fuel utilization and separate CO2 for sequestration or power generation.
Innovation Solution
A fuel cell recirculation complex that includes a waste heat recovery cycle, compressor, expander, and heat exchanger system to recycle and pre-cool the anode exhaust gas, removing water and CO2, and returning a stream with a higher molar concentration of CO and H2 to the anode inlet, enhancing fuel utilization and efficiency while capturing CO2.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If steam reforming is performed to maintain high steam-to-carbon ratio, then carbon deposition is prevented, but fuel utilization decreases and CO2 separation becomes necessary
Solution Approach 1:
The patent extracts CO2 from the anode exhaust stream through a CO2 capture unit, separating it from the reformed fuel gas. This allows the system to maintain high steam-to-carbon ratio for carbon deposition prevention while improving fuel utilization by removing CO2 that would otherwise limit the reforming process.
Solution Approach 2:
The patent changes the operational parameters by implementing a recirculation system that controls the ratio of fresh fuel feed to recirculated reformed fuel gas. By adjusting this ratio and maintaining optimal operating conditions in the reformer, the system achieves both high fuel utilization and sufficient steam-to-carbon ratio for carbon deposition prevention.
2Device complexity
If internal reforming is implemented to simplify design, then system complexity is reduced, but carbon deposition increases near the inlet
Solution Approach 1:
The patent applies different conditions to different regions of the fuel cell system. By introducing steam injection specifically at the anode inlet region and implementing recirculation of reformed fuel gas, the system creates locally optimized conditions that prevent carbon deposition near the inlet while maintaining internal reforming throughout the cell.
3Productivity
If fuel cell operates at high temperature for efficiency, then power generation efficiency increases, but carbon deposition is promoted
Solution Approach 1:
The patent implements preliminary steam injection at the anode inlet before the fuel undergoes reforming and electrochemical reactions. This pre-introduction of steam ensures that sufficient steam is present from the beginning of the process to prevent carbon deposition, even while operating at high temperatures that promote both efficiency and carbon formation.
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 increases SOFC efficiency to over 50% with simultaneous carbon capture, preventing carbon deposition and improving long-term operation, and allows for the generation of a nearly pure CO2 stream for sequestration or power expansion.
Implementation Method 1
a heat exchanger system configured to receive at least a portion of the expanded gas and to pre-cool the compressed waste heat recovery cycle exhaust gas
Implementation Method 2
remove by phase change water (H2O) and carbon dioxide (CO2) from the exhaust gas
Implementation Method 3
an expander configured to expand and cool the compressed exhaust gas
Implementation Method 4
an anode configured to generate a hot anode exhaust stream
Data Source
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AI summary
A system and method are provided for boosting overall performance of a fuel cell while simultaneously separating a nearly pure stream of CO2 for sequestration or for use in generating electrical power to further increase overall efficiency of the process. The system and method employ a heat exchanger system configured to generate a stream of fuel that is returned to the inlet of the fuel cell anode with a higher molar concentration of carbon monoxide (CO) and hydrogen (H2) fuel than was initially present in the fuel cell anode outlet.