Fuel Cell Reformer Startup Dynamics and Heat Management
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Solution Overview
Problem
Fuel cell systems face challenges in starting quickly from ambient temperatures with low pollutant emissions and fuel consumption, as existing methods are inefficient and unstable below operating temperatures.
Innovation Solution
Operating the reformer as a burner with an excess of oxygen to rapidly reach start temperature, and using a residual gas burner to generate heat for the reformer and fuel cell, with preheating of oxidizer and cathode gas to stabilize the reformer process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the reformer is operated in normal reformer operating state to generate fuel gas, then fuel gas can be supplied to the fuel cell, but the heating process is too slow and starting time is excessive
Solution Approach 1:
The reformer operates in two distinct dynamic states: a burner operating state during startup with excess oxygen (λ > 1) for rapid heating, and a reformer operating state during normal operation with fuel-rich conditions (λ < 1) for fuel gas generation. The system dynamically switches between these states based on temperature requirements, allowing fast startup followed by stable fuel production.
Solution Approach 2:
The air ratio (oxygen ratio λ) is changed as a key parameter to control the reformer's function. During startup, λ > 1 creates a high-temperature burner mode for rapid heating. During normal operation, λ < 1 creates a fuel-rich reforming mode for hydrogen production. This parameter change enables the reformer to serve dual purposes at different stages.
2Temperature
If the reformer is heated rapidly using burner operating state with excess oxygen, then the reformer reaches start temperature quickly, but fuel consumption increases during startup
Solution Approach 1:
The reformer heats itself during startup by operating as a burner, eliminating the need for external heating sources. The fuel and oxidizer are combusted directly within the reformer to generate the necessary temperature, making the heating process self-contained and efficient.
Solution Approach 2:
The excess oxygen that would normally be wasted or require separate handling is converted into a useful heating resource during startup. By intentionally operating with λ > 1, the system uses the oxidizer excess to create high-temperature combustion that rapidly brings the reformer to operating temperature, turning a potential waste into a beneficial heating mechanism.
3Temperature
If cold oxidizer is supplied to the reformer during heating, then the reformer can be heated, but the mixture formation process and partial oxidation process are severely impaired
Solution Approach 1:
The oxidizer is preheated before being supplied to the reformer during the heating phase. This preliminary heating action ensures that when the oxidizer contacts the fuel in the reformer, the mixture formation and partial oxidation processes can proceed smoothly without being disrupted by cold oxidizer injection, maintaining process stability throughout the heating sequence.
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 significantly shortens the starting time of the fuel cell system, reduces emissions and fuel consumption, and stabilizes the reformer process by efficiently heating the system to operating temperatures.
Implementation Method 1
operating the reformer as a burner, which converts the fuel with the oxidizer, until a reformer start temperature is reached
Implementation Method 2
combusting anode waste gas containing hydrogen gas produced during operation of the fuel cell with cathode waste gas containing oxygen gas
Implementation Method 3
the oxidizer fed to the reformer can be preheated by burner exhaust gas discharged from the residual gas burner
Implementation Method 4
the cathode gas supplied to the fuel cell can be preheated by the burner exhaust gas discharged from the residual gas burner
Data Source
Figure 1
AI summary
The method involves operating a reformer (3) for generating combustion gas containing hydrogen gas, from a fuel and an oxidizer, which contain hydrogen and oxygen, respectively, below a reformation starting temperature in a combustion operating condition for combustion of the fuel with the oxidizer. The reformer is operated above the temperature in the reformer operating condition for generation of fuel/combustion gas. A fuel cell is deactivated for generating electric current. The oxidizer is preheated by exhaust gas from a burner (13).