Fuel Cell SCR Control via Flow and Current Sensors
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Solution Overview
Problem
In fuel cell systems, it is challenging to measure the steam to carbon ratio (SCR) in real time due to difficulties in simultaneously measuring CO, CH4, and H2O content, leading to issues like carbon deposition, reduced efficiency, and potential system shutdowns.
Innovation Solution
A fuel cell system with an anode recirculation loop equipped with a flowmeter to measure fuel flow rate, a current sensor to measure current drawn from the fuel cell stack, and a processor to determine the SCR based on these measurements, allowing for real-time monitoring and control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the SCR is measured using traditional methods (direct measurement of CO, CH4, and H2O content), then the measurement precision may be sufficient, but the device complexity and difficulty of real-time measurement increase significantly
Solution Approach 1:
The patent introduces an intermediary approach by using a processor to calculate SCR indirectly through measurements of fuel flow rate, current, and predefined relationships (equations) rather than directly measuring CO, CH4, and H2O content. This mediator (processor with calculation algorithm) simplifies the measurement system while maintaining SCR determination capability
Solution Approach 2:
The patent replaces complex mechanical/chemical measurement systems (direct gas composition analysis) with an electrical/electronic calculation system. By substituting direct gas chromatography or spectroscopy with electrical measurements (fuel flow rate, current) and computational algorithms, the system achieves SCR determination with reduced complexity
2Reliability
If the SCR is kept high to prevent carbon deposition, then carbon formation is reduced, but cell voltage degradation accelerates and electrical efficiency decreases
Solution Approach 1:
The patent implements feedback control by continuously monitoring SCR through the processor and adjusting operating parameters (fuel flow rate, current) to maintain SCR within an optimal range. This feedback mechanism allows the system to prevent carbon deposition while avoiding excessive SCR values that would reduce electrical efficiency, dynamically balancing reliability and energy performance
Solution Approach 2:
The patent changes the control parameter from fixed high SCR to dynamically optimized SCR within a specific range. By adjusting SCR from a static high value to a variable parameter optimized through real-time calculation and control, the system prevents carbon deposition while maintaining acceptable electrical efficiency
3Loss of energy
If the SCR is reduced to improve electrical efficiency, then energy loss decreases, but carbon formation and deposition increase leading to system shutdown
Solution Approach 1:
The feedback control system continuously monitors SCR and adjusts operating conditions to maintain SCR above the carbon deposition threshold while minimizing energy loss. This real-time feedback prevents the system from operating at SCR values that would cause carbon formation, ensuring system continuity while optimizing electrical efficiency
4Reliability
If tight control of SCR is implemented to prevent carbon deposition, then reliability improves, but device complexity increases due to difficulty in real-time measurement
Solution Approach 1:
The patent replaces complex direct measurement systems with a simplified electrical measurement and calculation system. By substituting gas analysis equipment with electrical sensors (flow rate, current) and computational algorithms, the system achieves tight SCR control with reduced device complexity
Solution Approach 2:
The processor acts as an intermediary that simplifies SCR control by calculating SCR from easily measurable parameters (fuel flow rate, current) rather than requiring direct gas composition measurement. This mediator enables tight SCR control while minimizing system complexity
Data Source
AI summary
A fuel cell system is disclosed, which includes an anode recirculation loop having a fuel cell stack for generating power, a flowmeter, a current sensor and a processor. The flowmeter is configured for measuring a fuel flow rate provided into the anode recirculation loop. The current sensor is configured for measuring a current drawn from the fuel cell stack. The processor is configured for determining a steam to carbon ratio in the anode recirculation loop based on the measured fuel flow rate and the measured current. The fuel cell system further includes a temperature sensor for measuring a temperature in the anode recirculation loop. The process is configured for determining the steam to carbon ration further based on the measured temperature. A method for operating the fuel cell system and a fuel cell power plant are also disclosed.