Steam-Driven Ejector Fuel Cell Reforming With Anode Exhaust Heat Recovery
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Solution Overview
Problem
Existing fuel cell systems require auxiliary motive power sources for anode exhaust gas suction and waste combustion heat, leading to inefficient energy utilization.
Innovation Solution
A fuel cell system that generates steam using heat exchange with anode exhaust gas to vaporize water, integrating an ejector for recycling gases, and a vaporizer to enhance energy efficiency by utilizing thermal energy from anode exhaust.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a source gas pump is used to suck anode exhaust gas, then the anode exhaust gas can be circulated and mixed into raw fuel, but an auxiliary motive power source is required which decreases system efficiency
Solution Approach 1:
The system uses the anode exhaust gas itself to drive the ejector through its own combustion, eliminating the need for external auxiliary motive power sources. The combustion of anode exhaust gas generates the driving force for gas circulation and mixing, making the system self-sufficient.
Solution Approach 2:
The mechanical pump system is replaced with a thermal-field-based ejector system. Instead of using mechanical power to drive a pump, the system uses thermal energy from anode exhaust gas combustion to create a pressure differential that drives gas flow through the ejector.
2Ease of operation
If steam generated by combustion heat of anode exhaust gas is used as drive fluid, then the ejector can operate without auxiliary power, but the combustion heat is wasted and energy utilization decreases
Solution Approach 1:
The system converts the previously wasted combustion heat into a useful resource by using it to generate steam that drives the ejector. The thermal energy that would have been discarded is now harnessed to perform mechanical work, driving the gas circulation and mixing process.
Solution Approach 2:
The system utilizes the phase transition of water from liquid to steam through combustion heating. This phase change creates high-energy steam that serves as the drive fluid for the ejector, efficiently converting thermal energy into kinetic energy for gas transport.
3Loss of energy
If full anode exhaust gas is used for steam generation, then energy efficiency is improved, but insufficient gas remains for preheating raw fuel
Solution Approach 1:
The system uses only a portion of the anode exhaust gas for steam generation in the vaporizer, while the remaining gas is directed to preheat the raw fuel. This partial action ensures that both functions - steam generation for ejector drive and fuel preheating - are adequately served without one compromising the other.
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
Enhances energy efficiency by effectively using thermal energy from anode exhaust gas for steam generation, reducing the need for auxiliary motive power and improving system efficiency and reliability.
Implementation Method 1
the vaporizer generates the steam through heat exchange with the anode exhaust gas before the recycled gas is recovered therefrom
Implementation Method 2
a vaporizer which generates the steam by vaporizing water
Implementation Method 3
an ejector which, using, as a drive fluid, steam to be used as the moisture, sucks either a raw fuel containing the hydrocarbon or a recycled gas recovered from an anode exhaust gas
Implementation Method 4
a fuel cell stack which generates electric energy through electrochemical reaction of the reformed gas and an oxidant separated from each other at an anode and a cathode
Implementation Method 5
a reformer which generates a reformed gas containing hydrogen by reacting hydrocarbon and moisture with each other
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A fuel cell system includes: a reformer (2) which generates a reformed gas (F05) containing hydrogen by reacting hydrocarbon and moisture with each other; a fuel cell stack (1) which generates electric energy through electrochemical reaction of the reformed gas (F05) and an oxidant (F03); an ejector which, using steam (F11) as a drive fluid, sucks either a raw fuel (F01) containing the hydrocarbon or a recycled gas (F07) recovered from an anode exhaust gas (F06), and supplies a resultant gas to the reformer (2); and a vaporizer (4) which generates the steam (F11) by vaporizing water, wherein an operation temperature of the fuel cell stack (1) is higher than a boiling point of water at an operation pressure, and the vaporizer (4) generates the steam (F11) through heat exchange with the anode exhaust gas (F06).