Fuel Cell Heat Exchanger Network for Steam Reforming

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Solution Overview

Problem

High temperature fuel cell systems, such as solid oxide fuel cells, face inefficiencies in heat transfer from anode exhaust to water and fuel, requiring additional heating sources due to the form of latent heat in the exhaust, making typical heat exchangers commercially impractical for steam reforming needs.

Innovation Solution

The system employs a heat transfer device that uses the cathode exhaust stream to evaporate water into steam for the fuel inlet, and an air preheater to utilize anode exhaust heat, eliminating the need for additional heating sources and maximizing thermodynamic potential.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If typical heat exchangers are used to transfer heat from anode exhaust to water and fuel, then heat transfer is achieved, but additional heating sources are required due to latent heat form in exhaust making the process commercially impractical

Engineering Contradiction:

Improveheat energy recoveryVSAvoidheat exchanger system complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent converts the waste heat in anode exhaust, which was previously unusable due to being in latent heat form, into a beneficial resource by using it to evaporate water and generate steam for the fuel inlet, thereby eliminating the need for additional heating sources and improving overall system efficiency

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the thermal parameters of the system by using the cathode exhaust stream at high temperature to evaporate water, transforming the heat transfer process from a conventional sensible heat exchange to a phase change process that fully utilizes the available thermal energy

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If additional heating sources are used to compensate for insufficient heat transfer, then steam reforming needs are met, but system efficiency decreases

Engineering Contradiction:

Improvesteam quantity for reformingVSAvoidsystem energy efficiency

Core Design Contradiction:

Quantity of substanceVSUse of energy by moving object

Solution Approach 1:

The system achieves self-service by using its own cathode exhaust stream to provide the heat necessary for water evaporation and steam generation, eliminating the need for external heating sources and thereby maximizing energy efficiency while meeting all steam reforming requirements

Inventive Principle:

Principle #25Self-service

3Adaptability or versatility

If cathode exhaust stream is used to evaporate water, then additional heating sources are eliminated, but heat transfer device complexity increases

Engineering Contradiction:

Improveheat utilization flexibilityVSAvoidheat transfer device structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent merges the water evaporation function with the existing cathode exhaust stream, integrating multiple functions (heat recovery, water evaporation, steam generation) into a single heat transfer device, thereby eliminating the need for separate heating sources while maintaining practical device complexity through functional integration

Inventive Principle:

Principle #5Merging (Combining)

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 approach enhances system efficiency by fully recapturing heat energy without additional mass transfer devices, maintaining the fuel cell's elevated operating temperature and reducing the need for supplemental heating, thus improving overall system performance.

Implementation Method 1

a heat transfer device adapted to transfer heat from a cathode exhaust stream of the fuel cell stack to water to be provided to a fuel inlet stream

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Implementation Method 2

a water evaporator adapted to convert liquid water to steam

Methodology Applied

Scientific EffectEvaporation: Evaporation

Implementation Method 3

an air preheater which is adapted to preheat an air inlet stream using heat from an anode exhaust stream

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Implementation Method 4

the air preheater is adapted to partially condense the water vapor in the anode exhaust stream prior to the anode exhaust stream entering a condenser

Methodology Applied

Scientific EffectCondensation: Condensation

Implementation Method 5

Fuel cells are electrochemical devices which can convert energy stored in fuels to electrical energy with high efficiencies

Methodology Applied

Scientific EffectElectrochemical conversion: Fuel Cell

Data Source

PatentUS7858256B2High temperature fuel cell system with integrated heat exchanger network

Publication Date: 2010.12.28 BLOOM ENERGY CORP

AI summary

A fuel cell system (1) is provided and includes a fuel cell stack (3) and a heat transfer device (5) adapted to transfer heat from a cathode exhaust stream of the fuel cell stack (3) to water to be provided to a fuel inlet stream.