Steam-Driven Anode Off-Gas Ejector with Water Recovery
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Solution Overview
Problem
Current anode off gas recirculation systems in fuel cells face inefficiencies due to high energy consumption, increased pressure loss, and cost issues, particularly with blower-based systems and fuel-driven ejectors, while steam-driven ejectors may rely excessively on anode off gas for water supply.
Innovation Solution
A recirculation system that includes a superheater to extract thermal energy from anode off gas, generating steam to drive steam-driven ejectors and reduce boiler load, with control valves managing steam distribution to adapt to varying operating parameters, allowing for efficient recirculation without external water supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If blower-based recirculation systems are used, then anode off gas can be recirculated, but energy consumption increases and operational costs rise
Solution Approach 1:
The patent replaces the mechanical blower system with a steam-driven ejector system. The ejector uses steam expansion and pressure differential to drive the recirculation process, eliminating the need for mechanical moving parts and external power sources, thereby reducing energy consumption while maintaining recirculation productivity
Solution Approach 2:
The system uses waste heat from the fuel cell exhaust and internally generated steam to drive the recirculation process. The ejector is self-actuating through steam pressure, and the heat exchanger recovers heat from the hot exhaust stream, making the system self-sufficient without external energy input
2Productivity
If fuel-driven ejectors are used, then anode off gas recirculation is achieved, but pressure loss increases
Solution Approach 1:
The patent replaces fuel-driven ejectors with a steam-driven ejector system. Steam, being a cleaner and more controllable working fluid, reduces pressure losses compared to fuel-driven systems. The steam expansion process in the ejector creates a more efficient pressure differential with minimal pressure loss across the recirculation loop
3Use of energy by moving object
If steam-driven ejectors are used, then energy efficiency is improved, but water supply from anode off gas becomes insufficient
Solution Approach 1:
The patent introduces an external water source as an intermediary to supplement the water supply. This external water is fed to the steam generator to produce additional steam, which then drives the ejector. This mediator resolves the contradiction by ensuring sufficient water supply for steam generation without depleting the anode off gas water content
Solution Approach 2:
The steam generator serves multiple functions: it produces steam to drive the ejector, recovers heat from the exhaust stream, and accepts water from both the anode off gas and external sources. This multi-functionality allows the system to maintain energy efficiency while ensuring adequate water supply through diversified water inputs
4Use of energy by moving object
If thermal energy from anode off gas is extracted to generate steam, then energy efficiency improves and boiler load reduces, but system complexity increases
Solution Approach 1:
The patent merges the heat exchanger and steam generator into an integrated unit that performs multiple functions: cooling the exhaust stream, recovering thermal energy, generating steam, and controlling the recirculation process. This consolidation reduces system complexity compared to having separate components for each function while maintaining high energy efficiency
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 system enhances energy efficiency, reduces pressure loss, and lowers operational costs by utilizing thermal energy from anode off gas, ensuring effective anode off gas recirculation while minimizing water consumption and boiler overload.
Implementation Method 1
a superheater disposed downstream from the flow splitter and configured to cool a portion of the anode off gas received at the flow splitter
Implementation Method 2
a boiler operably coupled to the superheater and configured to receive the portion of the anode off gas cooled by the superheater, wherein the boiler is configured to generate steam
Implementation Method 3
the superheater is configured to use the generated steam to drive an ejector
Data Source
AI summary
A recirculation system for a fuel cell includes a flow splitter operably coupled to an anode of the fuel cell and configured to receive an anode off gas therefrom, a superheater disposed downstream from the flow splitter and configured to cool a portion of the anode off gas received at the flow splitter, and a boiler operably coupled to the superheater and configured to receive the portion of the anode off gas cooled by the superheater, wherein the boiler is configured to generate steam and direct at least a portion of the generated steam to the superheater, and wherein the superheater is configured to use the generated steam to drive an ejector.