SOFC Anode Off-Gas Recirculation for Carbon-Free Hydrocarbon Start-Up
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Solution Overview
Problem
Fuel cell systems operating with hydrocarbon fuels at intermediate-temperature solid oxide fuel cells face challenges such as carbon deposition and the need for external water supplies during start-up and shut-down, which increase complexity and cost.
Innovation Solution
A method that allows start-up and shut-down of fuel cell systems using unreformed hydrocarbon fuel without an external reformer, water supply, or partial oxidation reactor, by recirculating anode off-gas to the anode inlet and producing water internally for steam reforming, reducing the number of components and minimizing carbon deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external water supply and steam generator are used during start-up, then steam reforming can occur to produce hydrogen and prevent carbon deposition, but system complexity and cost increase
Solution Approach 1:
The fuel cell system generates its own steam during operation through the electrochemical reaction, which is then recirculated to the reformer. This self-generated steam prevents carbon deposition without requiring external water supplies or steam generators, making the system self-sufficient and reducing complexity
Solution Approach 2:
The system recycles water that would otherwise be wasted or require external supply. By capturing and recirculating steam back to the reformer, the system continuously replenishes the steam needed for reforming and carbon prevention without external inputs
2Quantity of substance
If external reformer is used to convert hydrocarbon fuel, then hydrogen-rich reformate stream is produced, but device complexity and cost increase
Solution Approach 1:
The reforming function is merged with the fuel cell stack itself. The reformer and fuel cell operate as an integrated system where the fuel cell provides heat and the reformer processes fuel in-situ, eliminating the need for separate external reforming equipment
Solution Approach 2:
The fuel cell system performs multiple functions: it generates electricity through electrochemical reaction, produces steam through the reaction, provides heat for reforming, and prevents carbon deposition. This multi-functionality eliminates the need for dedicated external reforming equipment
3Object-affected harmful factors
If steam is supplied to reformer during start-up, then carbon deposition is prevented, but water supply infrastructure is required
Solution Approach 1:
The fuel cell generates its own steam during operation, which is then recirculated to the reformer. This eliminates the need for external water supply infrastructure while continuously providing the steam needed to prevent carbon deposition on the anode
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 reduces the number of components, lowers costs, and minimizes carbon build-up in the stack, enabling reliable operation over 500 cycles with negligible carbon deposition, while eliminating the need for external water supplies.
Implementation Method 1
A typical fuel cell converts chemical energy in the form of a fuel and an oxidant to electrical energy
Implementation Method 2
steam reforming at a reformer is typically used to convert a hydrocarbon fuel stream (such as natural gas) into a hydrogen-rich reformate stream
Implementation Method 3
the fuel cell itself produces water, which is removed from the stack and could be used in the reformer
Data Source
AI summary
A fuel cell system (200, 300) and a method for operating the fuel cell system (200, 300). The fuel cell system (200, (1300) comprising an anode inlet (226) and an anode outlet (227); means for heating the stack (205); an anode off gas recirculation loop (240) configured to provide a gas flow path to recirculate anode off gas from the anode outlet (227) to the anode inlet (226); and a controller (290). The method comprising, at start-up of the fuel cell system (200, 300); heating the stack (205) to a first threshold temperature; providing an unreformed hydrocarbon fuel to the anode inlet (226) at a first fuel flow rate from a fuel supply (225) when but not before the stack (205) is above the first threshold temperature; recirculating anode off gas from the anode outlet (227) to the anode inlet (226) while providing unreformed fuel to the anode inlet (226); and drawing a current from the fuel cell system (200, 300) while recirculating the anode off gas.