Ejector Anode Gas Recirculation for High Temperature Fuel Cells
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Solution Overview
Problem
High temperature fuel cell and electrolysis systems face challenges in achieving efficient reactant utilization and thermal conditioning due to limitations in anode gas recirculation, particularly at varying operating modes, which can lead to inefficient fuel utilization and complex system design.
Innovation Solution
A recirculation arrangement using an ejector with a convergent-divergent nozzle and supplementary fluids to regulate motive flow and pressure, allowing for flexible and controlled anode gas recirculation, including parallel feedstock flows and heat exchanger integration to maintain optimal conditions across different operating modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If anode gas recirculation is implemented to improve fuel utilization, then reactant utilization efficiency is improved, but system complexity increases due to additional recirculation components
Solution Approach 1:
The ejector merges the recirculation flow path with the fuel feed path, combining multiple functions (recirculation, mixing, pressurization) into a single integrated component rather than separate pipes and valves
Solution Approach 2:
The ejector acts as an intermediary device that uses the primary feedstock fluid as a working medium to drive the recirculation of anode exhaust gas, eliminating the need for additional pumps or compressors
2Productivity
If recirculation components are added to control gas flow, then reactant utilization is improved, but device complexity increases
Solution Approach 1:
The ejector is a passive device that self-regulates the recirculation flow based on the pressure and flow characteristics of the primary feedstock fluid, eliminating the need for external control mechanisms
Solution Approach 2:
The mechanical recirculation system (pumps, valves, controllers) is replaced with a fluid-dynamics-based ejector that uses pressure differentials and flow mixing to achieve recirculation
3Reliability
If supplementary fluids are used to maintain ejector performance, then system reliability is improved, but device complexity increases
Solution Approach 1:
The system adjusts the flow parameters (pressure, temperature, flow rate) of the primary and supplementary feedstock fluids to optimize ejector performance under different operating conditions
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 enhances system performance, simplifies the design, and improves feasibility by ensuring efficient reactant utilization and thermal conditioning, while reducing complexity and maintaining reliability across various operating conditions.
Implementation Method 1
the ejector having at least one nozzle; means for providing at least one primary feedstock fluid to said nozzle of the ejector, which nozzle has a convergent-divergent flow channel through which the fluid will expand from an initial higher pressure to a lower pressure
Implementation Method 2
at least one ejector for recirculating a fraction of gas exhausted from the anode side and for accomplishing a desired flow rate of the recirculated flow
Implementation Method 3
heat exchanger integration to maintain optimal conditions across different operating modes
Data Source
AI summary
A method and system for high temperature fuel cell system or electrolysis cell are disclosed which include recirculating a fraction of gas exhausted from at least one of sides an anode side and a cathode side; accomplishing a desired flow rate of the recirculated flow by using an ejector via at least one primary feedstock fluid to a nozzle of the ejector, which nozzle has a convergent-divergent flow channel through which fluid is expanded from an initial higher pressure to lower pressure; providing supplementary fluid to the nozzle of the ejector; regulating respective ratio of the fluids of the ejector to maintain a desired motive flow and pressure at the nozzle of the ejector in order to accomplish desired recirculated flow rate; and cutting off the supplementary fluid when a level of system loading is the primary feedstock fluid alone maintains desired flow and pressure at ejector inlet.