Fuel Cell System with Cathode Exhaust Heat Recovery
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Solution Overview
Problem
In fuel cell systems, the heat from cathode exhaust gas is not utilized effectively, leading to inefficient temperature management and potential carbon deposition in the anode due to rich combustion gas with low temperatures.
Innovation Solution
A fuel cell system configuration that includes a first and second combustor, heating gas return channels, and a gas supplier to mix cathode exhaust gas with heating gases, allowing for efficient temperature regulation of the fuel cell while preventing carbon deposition by using lean combustion and controlled temperature settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If cathode exhaust gas is not utilized for heating, then the system structure remains simple, but the temperature management efficiency deteriorates and fuel consumption increases
Solution Approach 1:
The system uses its own cathode exhaust gas as a heating source to warm the fuel cell during startup, making the system self-sufficient and reducing external fuel requirements. The exhaust gas that would otherwise be wasted is redirected through a return channel to heat the fuel cell stack.
Solution Approach 2:
Instead of discarding the cathode exhaust gas directly to the atmosphere, the system recovers its thermal energy by routing it through a heat return channel to preheat the fuel cell during cold startup, thereby recovering waste heat that would otherwise be lost.
2Reliability
If rich combustion gas with low temperature is supplied to the anode, then the startup process is simplified, but carbon deposition occurs in the anode
Solution Approach 1:
The system changes the temperature parameter of the heating gas supplied to the anode by mixing cold rich combustion gas with hot cathode exhaust gas. This temperature blending prevents carbon deposition while maintaining the necessary fuel-rich conditions for startup.
Solution Approach 2:
The cathode exhaust gas acts as an intermediary medium that transfers thermal energy to the rich combustion gas destined for the anode. This intermediary heating process prevents carbon deposition without requiring direct temperature control of the fuel gas.
3Productivity
If cathode exhaust heat is utilized to raise fuel cell temperature, then temperature management efficiency improves, but the system complexity increases due to additional heating channels
Solution Approach 1:
The cathode exhaust gas return channel serves multiple functions: it acts as a thermal insulation barrier for the fuel cell stack and simultaneously serves as a heating pathway during cold startup. This multi-functionality reduces the need for separate insulation and heating systems.
Solution Approach 2:
The system merges the exhaust gas discharge path with the heating function by creating a return channel that both insulates the fuel cell and delivers thermal energy during startup, combining two functions into a single integrated structure.
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 configuration effectively utilizes cathode exhaust heat to raise the fuel cell temperature, reducing the risk of damage and carbon deposition, and minimizes fuel consumption during startup by using waste heat, thereby enhancing the system's efficiency and reliability.
Implementation Method 1
a first combustor (20) which burns fuel and selectively supplies a heating gas to the cathode (13)
Implementation Method 2
a second combustor (60) which burns fuel and selectively supplies a heating gas to the anode (12)
Implementation Method 3
a heat exchanger (40) having a heat exchanging section in which heat is exchanged between exhaust gas and air or fuel
Implementation Method 4
a reformer (30) which converts hydrocarbon gas into hydrogen-rich gas
Data Source
AI summary
A fuel cell system includes a fuel cell, a first combustor, a second combustor, a first heating gas return channel, a second heating gas return channel and a gas supplier. The fuel cell includes a solid electrolyte cell with an anode and a cathode. The first combustor supplies a heating gas to the cathode. The second combustor supplies a heating gas to the anode. The first heating gas return channel is arranged to mix at least some exhaust gas discharged from the cathode with the heating gas from the first combustor. The second heating gas return channel is arranged to mix at least some exhaust gas discharged from the cathode with the heating gas from the second combustor. The gas supplier is connected to the first heating gas return channel for supplying the exhaust gas from the cathode to mix with the heating gas of the first combustor.