Multistage Combustor for Fuel Cell Startup
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Solution Overview
Problem
Fuel cell systems face challenges in starting up efficiently and safely, as components like the anode can be subject to oxidative damage at low temperatures, and the reformer requires specific chemistry and heat for catalytic reactions, while preventing the formation of explosive mixtures during startup.
Innovation Solution
A multistage combustor is employed, comprising a partial oxidation (POX) burner and a second burner, which partially oxidizes a fuel/oxidant mixture to produce different output gases for safe and reducing gas generation, protecting the anode and heating the reformer, with the second burner further oxidizing remaining fuel to maximize heat and minimize pollutants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single-stage combustor is used for startup, then the device complexity is reduced, but it cannot provide both reducing gas for anode protection and heating for reformer simultaneously
Solution Approach 1:
The combustor is divided into two separate stages: a first combustor that produces reducing gas for anode protection, and a second combustor that produces heated gas for reformer startup. This segmentation allows each stage to be optimized for its specific function while avoiding the need for a complex single-stage system that would need to perform both functions simultaneously.
Solution Approach 2:
The dual-stage combustor system provides multi-functionality by generating two different types of output gases that can be selectively applied to different system components (anode and reformer) during startup, making the combustor system versatile enough to handle multiple startup requirements.
2Temperature
If complete oxidation is performed in the combustor, then maximum heat is generated for heating components, but no reducing gas is available for anode protection
Solution Approach 1:
The oxidation process is segmented into two distinct combustors: the first combustor performs partial oxidation to generate reducing gas for anode protection, while the second combustor performs complete oxidation to generate high-temperature heated gas for reformer startup. This segmentation resolves the contradiction by separating the conflicting requirements of reducing gas generation and heat generation.
Solution Approach 2:
The first combustor acts as an intermediary that produces reducing gas which is then used to protect the anode before the second combustor provides heated gas for reformer startup. This intermediary step ensures anode protection is established before high-temperature heating begins.
3Reliability
If partial oxidation is performed to generate reducing gas, then anode protection is achieved, but insufficient heat is generated for reformer heating
Solution Approach 1:
The heat generation function is segmented from the reducing gas generation function by using two separate combustors. The first combustor focuses on producing reducing gas for anode protection, while the second combustor is dedicated to generating high-temperature heated gas for reformer startup, ensuring both requirements are met optimally.
Solution Approach 2:
The dual-stage combustor system enables continuous useful action by simultaneously providing both reducing gas flow to the anode and heated gas flow to the reformer during the startup process, ensuring that protection and heating occur concurrently without interruption.
4Use of energy by moving object
If fuel/air mixture is supplied during startup, then energy is available for heating, but risk of explosive mixture formation increases
Solution Approach 1:
The system performs preliminary action by first establishing reducing gas flow from the first combustor to create a protective atmosphere in the anode, before introducing the fuel/air mixture to the second combustor for heating. This preliminary protection reduces the risk of explosive mixtures forming in the anode during the high-energy heating phase.
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 multistage combustor effectively starts the fuel cell system by providing a safe, reducing gas to protect the anode and heat the reformer, ensuring a controlled and efficient startup, minimizing the risk of explosions and extending catalyst life, while achieving efficient heat-up and reducing pollutant emissions.
Implementation Method 1
the partial oxidation (POX) burner being configured to partially oxidize a fuel in the fuel/oxidant mixture to yield a partially oxidized gas
Implementation Method 2
the second burner being configured to receive a second amount of the partially oxidized gas from the POX burner and to oxidize at least some of a remaining fuel in the second amount of the partially oxidized gas
Implementation Method 3
the reformer may require a specific chemistry in addition to heat, in order to start its catalytic reactions that generate the synthesis gas
Data Source
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AI summary
A multistage combustor is configured for starting a fuel cell system, and includes a partial oxidation (POX) burner having an inlet for receiving a flow of a fuel/oxidant mixture, the POX burner being configured to partially oxidize fuel in the fuel/oxidant mixture to yield a partially oxidized gas; a first output coupled to the fuel cell system and configured to provide a first amount of the partially oxidized gas as first output gas to a first fuel cell system component; a second burner coupled to the POX burner, the second burner being configured to receive a second amount of the partially oxidized gas from the POX burner and to oxidize at least some remaining fuel to yield a second output gas different from the first output gas; and a second output coupled to a second fuel cell system component and configured to provide the second output gas to the second fuel cell system component.