# US 8,771,888 B2 · Fuel cell system and method of load following operation of the same

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- Number: US 8,771,888 B2
- Document ID: US8771888B2
- Status: Granted
- Kind: B2
- Application number: 12/934,992
- Filed: 2009-02-18
- Published: 2011-02-03
- Granted: 2014-07-08
- Earliest claimed: 2008-03-27
- Assignees: Jx Nippon Oil & Energy Corporation
- Applicants: Susumu Hatada
- Inventors: Susumu Hatada
- Web page: https://patentgrep.com/patent/US8771888B2

## CPC

- H01M 8/04589: {of fuel cell stacks}
- C01B 3/384: with external heating of the catalyst
- H01M 8/04373: {of auxiliary devices, e.g. reformers, compressors, burners}
- H01M 8/04425: {at auxiliary devices, e.g. reformers, compressors, burners}
- H01M 8/04776: {at auxiliary devices, e.g. reformer, compressor, burner}
- H01M 8/0491: {of fuel cell stacks}
- H01M 8/0494: {of fuel cell stacks}
- H01M 8/04955: Shut-off or shut-down of fuel cells
- H01M 8/04992: characterised by the implementation of mathematical or computational algorithms, e.g. feedback control loops, fuzzy logic, neural networks or artificial intelligence
- H01M 8/0618: {Reforming processes, e.g. autothermal, partial oxidation or steam reforming}
- C01B 2203/0233: the reforming step being a steam reforming step
- C01B 2203/066: with fuel cells
- C01B 2203/085: by electric heating
- C01B 2203/1288: Evaporation of one or more of the different feed components
- C01B 2203/1619: Measuring the temperature
- C01B 2203/1685: Control based on demand of downstream process
- C01B 2203/169: Controlling the feed
- H01M 2008/1293: {Fuel cells with solid oxide electrolytes}
- Y02E 60/50: Fuel cells
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

Provided is a fuel-cell system and a method of operating the fuel-cell system, wherein functions F=f(P) and P=f−1(F) of electrical output P and fuel flow-rate F required to output P are beforehand obtained, and a reformable fuel flow-rate FR is calculated from the temperature of reforming catalyst layer. When FR≧Fmin, if the output demand PD≦maximum output PM, and when f(PD)≦FR, F is set to f(PD); and when f(PD)>FR, the P is set to the maximum value within a range of less than PD amongst P calculated from P=f1(FR), and F is set to FR. When PD>PM, and when f(PM)≦FR, the cell output is set to PM, and F is set to f(PM). When f(PM)>FR, the cell output is set to the maximum value amongst P calculated from P=f1(FR), and F is set to FR.

## Claims

### Claim 1

A method of load following operation of a fuel cell system comprising a reformer having a reforming catalyst layer, for reforming a hydrocarbon-based fuel to produce a reformed gas containing hydrogen, and a high temperature fuel cell for generating electric power using the reformed gas, the method comprises determining before start of the load following operation:
functions F=f(P) and P=f−1(F),
where P is an electrical output of the fuel cell and F is a flow rate of the hydrocarbon-based fuel required to be supplied to the reforming catalyst layer in order to output the electrical output P from the fuel cell, P=f−1(F) is an inverse function of
F=f(P), wherein flow rate F is uniquely determined for each value of P in the range of 0 to PM, wherein PM represents maximum electrical output of the fuel cell and wherein for at least one value of F there are plurality of P values; and
a minimum value of flow rate of the hydrocarbon-based fuel, which is represented as Fmin, said Fmin being a minimum value that is given by the function F=f(P) when P ranges in the range of 0 to PM,
the load following method comprising:
A) measuring a temperature of the reforming catalyst layer;
B) calculating a reformable flow rate FR that is a flow rate of the hydrocarbon-based fuel capable of being reformed in the reforming catalyst layer, based on the measured temperature of the reforming catalyst layer;
C) when the calculated reformable flow rate FR is smaller than the minimum value Fmin, stopping electric power generation in the fuel cell; and
D) when the calculated reformable flow rate FR is equal to or more than the minimum value Fmin,
performing step d1 if a fuel cell output demand value PD is equal to or less than the maximum electrical output PM, and performing step d2 if the fuel cell output demand value PD exceeds the maximum electrical output PM,
d1) calculating a flow rate f(PD) of the hydrocarbon-based fuel required to be supplied to the reforming catalyst layer in order to output the fuel cell output demand value PD from the fuel cell, using the function F=f(P),
if f(PD) is equal to or less than the calculated reformable flow rate FR, setting an electrical output of the fuel cell to PD, and setting a flow rate of the hydrocarbon-based fuel supplied to the reforming catalyst layer to f(PD), and
if f(PD) exceeds the calculated reformable flow rate FR, setting the electrical output of the fuel cell to a P value that is the highest from amongst one or more P values calculated from P=f−1(FR), but which is lower than the PD value, and setting the flow rate of the hydrocarbon-based fuel supplied to the reforming catalyst layer to FR,
d2) calculating a flow rate f(PM) of the hydrocarbon-based fuel supplied to the reforming catalyst layer required to be supplied to the reforming catalyst layer in order to output the maximum electrical output PM from the fuel cell, using the function F=f(P),
if f(PM) is equal to or less than the calculated reformable flow rate FR, setting the electrical output of the fuel cell to PM, and setting the flow rate of the hydrocarbon-based fuel supplied to the reforming catalyst layer to f(PM), and
if f(PM) exceeds the calculated reformable flow rate FR, setting the electrical output of the fuel cell to a P value that is the highest from amongst one or more P values calculated from P=f−1(FR), and setting the flow rate of the hydrocarbon-based fuel supplied to the reforming catalyst layer to FR,
wherein output demand value PD fluctuates with time.

### Claim 2 (depends on 1)

The method according to claim 1, wherein steps A to D are repeatedly performed during the load following operation.

### Claim 3 (depends on 1)

The method according to claim 1, wherein the hydrocarbon-based fuel comprises a hydrocarbon-based fuel with a carbon number of two or more.

### Claim 4 (depends on 3)

The method according to claim 3, wherein the concentration of a compound with a carbon number of two or more carbon atoms in the reformed gas is 50 ppb or less on a mass basis.

### Claim 5 (depends on 1)

The method according to claim 1, wherein the fuel cell system comprises a solid oxide fuel cell.

### Claim 6 (depends on 5)

The method according to claim 5, wherein the solid oxide fuel cell is an indirect internal reforming solid oxide fuel cell.

### Claim 7 (depends on 6)

The method according to claim 6, wherein the reformer is disposed at a position where radiation head can be directly transferred from the solid-oxide fuel cell to the reformer.

### Claim 8 (depends on 1)

The method according to claim 1, wherein the fuel cell system comprises a molten carbonate fuel cell.