Variable Nozzle Steam Jet-Ejector for SOFC Anode Recirculation
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Solution Overview
Problem
Existing fuel cell systems face challenges in managing the Oxygen-to-Carbon (O/C) ratio due to the complexity and inaccuracy of high temperature gas stream composition measurements, leading to limited control over recirculation ratios and efficiency, particularly in solid oxide fuel cells (SOFCs) requiring high-pressure fuel feeds and sophisticated machinery.
Innovation Solution
A method utilizing conventional components, including a water pump, steam generator, and steam jet-ejector to generate pressurized steam, which injects into the fuel cell system to entrain and compress the anode exhaust gas, controlling the O/C ratio without external water feeds and simplifying the system by using anode exhaust gas as a water source, thus enhancing fuel utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If high pressurized fuel feed is used as motive stream in jet-ejector to entrain anode tail gas, then pressure of fuel gas mixture is increased to overcome pressure losses, but system requires high pressure fuel feedstock and has limited capability for controlling recirculation ratio
Solution Approach 1:
The patent replaces the fixed geometry jet-ejector with a variable geometry nozzle that can dynamically adjust its opening area. This allows the system to control the recirculation ratio by varying the nozzle opening, enabling adaptation to different operating conditions while maintaining the pressure boost function.
Solution Approach 2:
The patent changes the key control parameter from the fixed geometric configuration of the jet-ejector to the variable opening area of the nozzle. By controlling the nozzle opening area, the system can dynamically adjust the recirculation ratio and O/C ratio, providing versatile control capability.
2Adaptability or versatility
If fan or compressor is used for anode off-gas recirculation, then flexibility and controllability are improved, but device complexity and potential reliability issues increase
Solution Approach 1:
The patent extracts the core function of pressure boosting and recirculation from complex mechanical devices (fans, compressors) and implements it through a simpler variable geometry nozzle system driven by the existing high-pressure fuel feed, eliminating the need for additional sophisticated machinery.
Solution Approach 2:
The system uses the high-pressure fuel feedstock as a self-sufficient motive stream to drive the jet-ejector and enable anode off-gas recirculation, eliminating the need for external power sources or additional mechanical devices.
3Measurement precision
If measurement means are used for high temperature gas stream composition, then O/C ratio determination is attempted, but measurement accuracy is insufficient leading to poor control
Solution Approach 1:
The patent introduces a water mass flow rate as an intermediary control parameter that indirectly controls the O/C ratio. By controlling the water mass flow rate added to the system, the O/C ratio is adjusted without requiring direct measurement of high-temperature gas composition, avoiding the measurement difficulties.
Solution Approach 2:
The patent shifts the control parameter from direct O/C ratio measurement (which is difficult at high temperatures) to water mass flow rate control (which is easily measurable), providing accurate control through a different, more accessible parameter.
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 effectively manages the O/C ratio using conventional components, improving fuel utilization and reducing system complexity by leveraging anode exhaust gas for water and recirculation, thereby enhancing the efficiency and reliability of fuel cell operations.
Implementation Method 1
utilizing at least one steam jet-ejector for injecting at least part of said steam to the fuel cell system and entraining part of the essentially low pressure anode exhaust gas stream
Implementation Method 2
compressing the gas mixture to an intermediate pressure of the fuel feed-in stream
Implementation Method 3
evaporating water from said facilitated water flow for generating pressurized steam having at least the motive pressure for a steam jet-ejector
Data Source
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AI summary
The object of the invention is a fuel cell system arrangement for controlling Oxygen-to-Carbon (O/C) relationship comprises means (112) for providing water to the anode side fuel recirculation, at least one water pump (118) for pumping the provided water to facilitate a water flow, means (120) for evaporating water from said facilitated water flow for generating pressurized steam having at least the motive pressure for a steam jet-ejector (122), and said at least one steam jet-ejector (122) for injecting at least part of said steam to the fuel cell system and entraining part of the essentially low pressure anode exhaust gas stream in said anode side gas recirculation and compressing the gas mixture to an intermediate pressure of the fuel feed-in stream for controlling Oxygen-to-Carbon (O/C) relationship in the fuel side of the fuel cell system.