Solid Oxide Fuel Cell Hydrogen Separation for CO2 Capture
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Solution Overview
Problem
Current methods for producing electrical power and carbon dioxide are energy-inefficient and not suitable for producing clean, pressurized carbon dioxide for enhanced oil recovery, and existing fuel cell systems optimized for high fuel utilization are not effective as hydrogen generators with carbon dioxide capture.
Innovation Solution
A method and system using a solid oxide fuel cell (SOFC) with two consecutive water-gas shift reactors, a high temperature water-gas shift reactor, and a low temperature water-gas shift membrane reactor to convert reformed process gas into carbon dioxide, hydrogen, and electricity, where the low temperature reactor includes an electrochemical pump to separate hydrogen and produce a carbon dioxide-rich stream.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a fuel cell system is optimized for high fuel utilization (approaching 100%), then system efficiency is improved, but the system is no longer suitable as a hydrogen generator with carbon dioxide capture
Solution Approach 1:
The patent segments the fuel utilization process into two distinct streams: one optimized for high fuel utilization (96-99%) to maximize electricity generation efficiency, and another dedicated to hydrogen generation with CO2 capture. This segmentation allows each stream to be independently optimized for its specific function without compromise.
Solution Approach 2:
The fuel cell system is designed to perform multiple functions simultaneously: it generates electricity with high efficiency while also producing purified hydrogen and capturing CO2. The system achieves this multi-functionality by processing the anode exhaust stream through different pathways - one for electricity generation and another for hydrogen separation and CO2 concentration.
2Reliability
If additional resources and products are introduced to run the process, then carbon dioxide capture capability is improved, but energy efficiency deteriorates
Solution Approach 1:
The system uses the anode exhaust stream from the fuel cell as the feed for the water-gas shift reaction, which naturally produces CO2 and H2. The electrochemical hydrogen pump then separates H2 from this stream, automatically concentrating CO2 without requiring additional energy-intensive processes. The system essentially serves itself by using its own exhaust as the basis for CO2 capture.
Solution Approach 2:
The patent changes the operational parameters of the water-gas shift reaction by controlling temperature and pressure conditions in the reactor, and adjusts the electrochemical pump operation to achieve optimal H2 separation. These parameter changes enable efficient CO2 concentration without requiring additional energy inputs or external resources.
3Productivity
If the electrochemical hydrogen pump operates at excess of 90% utilization, then fuel utilization rate is improved (approaching 100%), but the system cannot function as a hydrogen generator with carbon dioxide capture
Solution Approach 1:
The patent divides the electrochemical hydrogen pump operation into two modes: one operating at >90% utilization to maximize fuel consumption for electricity generation, and another operating at lower utilization to produce purified hydrogen. The anode exhaust stream is directed to different processing pathways based on the desired output, allowing the system to switch between high fuel utilization and hydrogen generation modes.
4Reliability
If a pressurized SOFC system is used, then carbon dioxide capture is achieved, but the system becomes less energy-efficient
Solution Approach 1:
The patent changes the pressure parameter by operating the SOFC system at atmospheric pressure rather than elevated pressure. This parameter change eliminates the energy penalty associated with pressurization while maintaining effective CO2 capture through the water-gas shift reaction and electrochemical hydrogen separation process.
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 enables efficient production of purified hydrogen, carbon dioxide, and electricity from a reformed process gas feed, allowing for flexible fuel utilization and self-sufficient operation with minimal additional resources, while maintaining high system efficiency and reducing energy consumption.
Implementation Method 1
converting hydrogen and carbon monoxide of the reformed process gas in combination with oxygen into an anode off-gas comprising steam, carbon dioxide and unconverted process gas
Implementation Method 2
converting carbon monoxide and steam into carbon dioxide and hydrogen
Implementation Method 3
converting carbon monoxide and steam into carbon dioxide and hydrogen, whereby the low temperature water-gas shift membrane reactor comprises a hydrogen pump that produces purified hydrogen on a permeate side, while removing hydrogen from a feed side
Data Source
AI summary
Method and system for producing CO2, purified hydrogen and electricity from a reformed process gas feed using a solid oxide fuel cell. The method having the steps of: introducing the reformed process gas into the solid oxide fuel cell; converting hydrogen and CO of the reformed process gas in combination with oxygen into an anode off-gas including steam, CO2 and unconverted process gas; introducing the anode off-gas into a high temperature water gas shift reactor; in the high temperature water-gas shift reactor, converting CO and steam into CO2 and hydrogen, introducing the gas exiting the high temperature water-gas shift reactor into a low temperature water-gas shift membrane reactor, in the low temperature water-gas shift membrane reactor, converting CO and steam into CO2 and hydrogen, whereby the low temperature water-gas shift membrane reactor comprises a hydrogen pump producing purified hydrogen on a permeate side, while removing hydrogen from a feed side.