Fuel Cell Waste Heat Recovery via Gas Oxidizer
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Solution Overview
Problem
Conventional fuel cell systems are limited in recovering high pressure steam and waste heat, with maximum recoverable heat restricted to about 371.1° C (700° F) and 103.4 kPa (15 psig), resulting in inefficiencies and unusable waste heat in high pressure steam applications.
Innovation Solution
A fuel cell system with a gas oxidizer/high level heat recovery assembly that oxidizes fuel cell exhaust to generate high pressure high temperature steam, incorporating a boiler to produce steam above 426.7° C (800° F) and utilizing waste heat for other processes, along with water and heat recovery systems to enhance efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional heat exchanger is used to recover waste heat, then heat recovery is achieved, but the maximum temperature is limited to about 371.1° C (700° F) and pressure to about 103.4 kPa (15 psig)
Solution Approach 1:
The patent changes the fundamental parameter of heat recovery by transitioning from indirect heat exchange to direct combustion of exhaust gases. This allows the steam temperature to exceed 426.7° C (800° F) and pressure to reach 4136.8 kPa (600 psig), dramatically improving both temperature and pressure parameters while recovering otherwise unusable high-level waste heat.
Solution Approach 2:
The patent introduces a boiler as an intermediary device that receives exhaust gases and uses them to generate high-pressure steam. This intermediary enables the conversion of waste heat into a useful form (high-pressure steam) that can be directly applied to industrial processes, bypassing the temperature and pressure limitations of conventional heat exchangers.
2Productivity
If conventional heat exchanger with temperature approach of 10.0° C (50° F) to 65.6° C (150° F) is used, then heat transfer is achieved, but additional 5 to 20% of heat becomes unavailable
Solution Approach 1:
The patent converts the previously harmful waste heat exhaust into a beneficial resource by combusting it in a boiler. The exhaust gases, which were previously discarded as waste heat, now serve as fuel to generate high-pressure steam, turning a loss into a productive asset and eliminating the temperature approach penalty entirely.
3Stress or pressure
If waste heat is recovered for high pressure steam production, then steam pressure can be increased, but the amount of waste heat recovered is greatly reduced in conventional systems
Solution Approach 1:
The patent fundamentally changes the method of heat recovery from indirect heat exchange to direct combustion, which enables simultaneous achievement of high steam pressure (4136.8 kPa or 600 psig) and high waste heat recovery efficiency. The direct combustion process eliminates the temperature approach limitation, allowing maximum energy extraction from the exhaust gases.
4Reliability
If conventional water preparation components are used, then water treatment is achieved, but power is required for their operation
Solution Approach 1:
The system recovers water from the exhaust gases through condensation and uses this recovered water for steam generation, making the system self-sufficient for water preparation. This eliminates or reduces the need for external water treatment components and their associated power consumption, as the system essentially treats and recycles its own waste water.
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
The system achieves improved electrical efficiency, increased waste heat recovery, and eliminates the need for conventional water preparation components, enabling the production of high pressure steam and efficient heat recovery for industrial applications.
Implementation Method 1
an oxidizer adapted to oxidize one or more of exhaust output from the at least one high temperature fuel cell stack and a gas derived from the exhaust, and to generate high level heat
Implementation Method 2
a boiler adapted to receive feed water and to generate high pressure high temperature steam using the waste heat generated by the oxidizer
Implementation Method 3
a high level heat recovery system adapted to recover the high level heat generated in the oxidizer assembly
Data Source
AI summary
A fuel cell system for generating electrical power and high level heat comprising at least one high temperature fuel cell stack having an anode side and a cathode side and adapted to generate electrical power, and a gas oxidizer/high level heat recovery assembly comprising an oxidizer adapted to oxidize one or more of exhaust output from the at least one high temperature fuel cell stack and a gas derived from the exhaust, and to generate high level heat, and a high level heat recovery system adapted to recover the high level heat generated in the oxidizer.