Fuel Cell Recirculation Passage for Thermal Management
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Solution Overview
Problem
Conventional fuel cell systems with tubular solid oxide fuel cells lack optimal thermal management, leading to inefficiencies and potential damage from thermal expansion/contraction and carbon formation.
Innovation Solution
A fuel cell system with a recirculation passage inside the fuel cell main body that recirculates exhaust products directly to the anode side for reaction, and optionally includes a reforming catalyst to partially reform the mixture within the passage, improving local thermal management and reducing the risk of anode surface damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If exhaust products are recirculated externally to the steam reformer, then steam for reforming is provided, but thermal management is suboptimal and system complexity increases
Solution Approach 1:
The patent merges the recirculation passage and steam reforming function into the fuel cell main body itself, eliminating the need for external pipe work and external steam reformers. The recirculation passage is configured to receive exhaust products from the exhaust plenum and recirculate them to the fuel inlet, with the steam reforming occurring within the main body, thereby simplifying the overall system structure while optimizing thermal management.
Solution Approach 2:
The recirculation passage acts as an intermediary component that facilitates the transfer of exhaust products back to the fuel inlet within the compact main body. This intermediary structure enables efficient thermal coupling between the exhaust stream and the reforming process without requiring complex external piping, thus resolving the contradiction between thermal management and system complexity.
2Device complexity
If recirculation passage is located outside the fuel cell main body, then exhaust recirculation is possible, but system compactness is reduced and thermal management is suboptimal
Solution Approach 1:
The recirculation passage is merged with the fuel cell main body structure, eliminating separate external components. The passage is integrated within the main body to receive exhaust from the exhaust plenum and deliver recirculated exhaust to the fuel inlet, achieving both compactness and optimal thermal management through this unified structure.
Solution Approach 2:
The recirculation passage is nested within the fuel cell main body, with the passage positioned to utilize the thermal field and spatial arrangement of the existing fuel cell components. This nesting approach allows the recirculation function to be accommodated within the compact main body without adding external complexity, while maintaining effective thermal coupling.
3Productivity
If no recirculation of exhaust products is implemented, then system simplicity is maintained, but fuel utilization decreases and thermal management is suboptimal
Solution Approach 1:
The recirculation passage enables continuous recirculation of exhaust products containing unreacted fuel and steam back to the fuel inlet. This continuous recirculation process maintains useful action by repeatedly utilizing the unreacted fuel and steam for further reforming and reaction at the anode, thereby improving fuel utilization without significantly increasing system complexity.
Solution Approach 2:
The recirculation system implements feedback by returning exhaust products to the fuel inlet, where unreacted fuel and steam are reused. This feedback loop continuously improves fuel utilization by ensuring that fuel components not consumed in the first pass are recovered and reacted again, creating a closed-loop system that maximizes fuel efficiency.
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
Enhances thermal management, increases fuel utilization, and reduces the risk of anode surface damage by minimizing thermal stress and carbon formation, while maintaining a compact system design without external pipe work or steam reformers.
Implementation Method 1
The recirculated exhaust products provide the steam that is needed for the steam reforming process and the recirculated unreacted fuel increases fuel utilization
Implementation Method 2
The waste heat is recovered by the heat exchanger 18 as the oxygen-depleted air is exhausted through an air outlet 20, to thereby heat the air supplied through the air inlet 16
Implementation Method 3
a suitable hydrocarbon fuel (for example natural gas containing methane) is injected into a steam reformer 22 which is located externally of the fuel cell main body 11
Implementation Method 4
The steam-reformed fuel is reacted at the surface of each internal anode 12 such that the hydrogen and carbon monoxide is electrolytically oxidized by oxygen ions passing through the fuel cell surface
Data Source
AI summary
A fuel cell system comprises a fuel cell main body containing a fuel cell having an anode side at which fuel is reacted, exhaust products arising at the anode side of the fuel cell as a result of the reaction at the anode side. A recirculation passage is located inside the fuel cell main body and recirculates a proportion of the exhaust products directly to the anode side of the fuel cell for reaction at the anode side. The recirculation passage may include an ejector arrangement for mixing fresh fuel with the recirculated exhaust products and may also include a reforming catalyst for partially reforming the mixture in the recirculation passage.