Low Pressure CO2 Removal from Fuel Cell Anode Exhaust
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Solution Overview
Problem
High temperature fuel cells, such as molten carbonate and solid oxide fuel cells, face inefficiencies due to the presence of carbon dioxide in anode exhaust, which hinders the recycling and utilization of valuable byproduct gases like hydrogen and carbon monoxide.
Innovation Solution
A system comprising a shift reactor, an absorption system with an absorber and stripper column, and an anode gas oxidizer, which performs a water-gas shift reaction and absorbs carbon dioxide using solvents like amine solutions or dimethyl ethers of polyethylene glycol, allowing for the recycling and oxidation of gases to enhance fuel cell efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If carbon dioxide is removed from anode exhaust using conventional methods, then hydrogen and carbon monoxide can be recycled, but the system complexity increases due to additional equipment
Solution Approach 1:
The patent extracts carbon dioxide from the anode exhaust stream using an absorption system with solvent, separating it from valuable hydrogen and carbon monoxide components. This allows the useful gases to be recycled back to the anode while the captured CO2 is diverted to oxidation or storage, directly resolving the contradiction by enabling productivity improvement through selective removal without requiring complete system redesign
Solution Approach 2:
The anode exhaust gas is directed to multiple uses: portion is recycled to the anode for continued fuel cell operation, portion is sent to the absorption system for CO2 capture, and portion is directed to the anode gas oxidizer. This multi-functional approach maximizes the utility of the exhaust stream while managing CO2, improving overall system productivity without proportionally increasing complexity
2Use of energy by moving object
If anode exhaust is recycled to improve fuel utilization, then efficiency increases, but carbon dioxide accumulation hinders the recycling process
Solution Approach 1:
The patent converts the harmful effect of carbon dioxide accumulation into a beneficial process by capturing CO2 through the absorption system and directing it to the anode gas oxidizer where it is converted to useful heat and power. This transforms the waste product that hinders recycling into a useful resource, enabling continuous exhaust recycling while maintaining fuel utilization efficiency
Solution Approach 2:
The absorption system acts as an intermediary between the anode exhaust stream and the recycling process. By removing CO2 through solvent absorption before recycling, it mediates the conflict between CO2 accumulation and efficient recycling, allowing high fuel utilization without harmful gas buildup
3Object-affected harmful factors
If carbon dioxide is captured and oxidized, then harmful emissions are reduced, but energy is consumed in the oxidation process
Solution Approach 1:
The anode gas oxidizer utilizes the carbon dioxide from the absorption system to generate heat and power that are fed back into the fuel cell system. This self-service approach means the energy required for CO2 oxidation is partially or fully supplied by the CO2 itself, converting what would be a net energy loss into a self-sustaining process that reduces emissions without external energy input
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 effectively removes carbon dioxide from anode exhaust, increasing fuel cell efficiency by recycling hydrogen and reducing the need for external fuel, while also capturing carbon dioxide for further use, thereby improving overall system performance.
Implementation Method 1
a shift reactor configured to receive a first portion of the anode exhaust gas and to perform a water-gas shift reaction to produce an output stream primarily comprising hydrogen and carbon dioxide
Implementation Method 2
an absorber column configured to absorb the carbon dioxide from the output stream in a solvent
Implementation Method 3
a stripper column configured to regenerate the solvent and to output a carbon dioxide-rich stream
Implementation Method 4
The anode gas oxidizer is configured to receive and oxidize an anode gas oxidizer input stream and at least a portion of the carbon dioxide-rich stream
Data Source
AI summary
A fuel cell system for removing carbon dioxide from anode exhaust gas includes: a fuel cell having an anode configured to output an anode exhaust gas comprising hydrogen, carbon monoxide, carbon dioxide, and water; an anode gas oxidizer; and an absorption system configured to receive the anode exhaust gas, the absorption system including: an absorber column configured to absorb the carbon dioxide from the anode exhaust gas in a solvent and to output a resultant gas comprising hydrogen and a hydrocarbon that is at least partially recycled to the anode; and a stripper column configured to regenerate the solvent and to output a carbon dioxide-rich stream. The anode gas oxidizer is configured to receive and oxidize an anode gas oxidizer input stream and at least a portion of the carbon dioxide-rich stream. The anode gas oxidizer input stream comprises a portion of the anode exhaust gas.