triple combustion cycle power plant

8/10/2019 Triple Combustion Cycle Power Plant

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Development of SOFC-GTCombined Cycle System

with Tubular Type Cell Stack

1

Fuel Cell Seminar 2010 at San Antonio

October 19, 2010

Kazuo Tomida, M. Nishiura, S. Koga, K. Miyamoto, Y. Teramoto,S. Yoshida, N. Matake, S. Suemori, T. Kabata, Y. Ando, Y. Kobayashi

Mitsubishi Heavy Industries, LTD


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Contents1. About Mitsubishi Heavy Industries (MHI)

2. Strategy of SOFC-GTCC Development at MHI

3. 200kW-Class SOFC-MGTCC System

2

. ct v ty an rogress o eve opment5. Conclusion


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Net sales : 3,200 billion yen (2007-2009 average)Manufacturing about 700 items in a very broadrange of fields:

Power systemsAerospaceMachinery & steel structuresShipbuilding & ocean development

About MHI

3

Air conditioning & refrigeration systemsMachine tools, others


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Operating bases

Total number of employees (consolidated basis): 67,669 (as of March 31, 2010)

4


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Contributing to achieve a low-carbon society withMHIs integrationResponding to community needs for rebuilding infrastructure of energy and environment byapplying a wide range of MHI product technologies to realize smart community.

5


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Contents1. About Mitsubishi Heavy Industries (MHI)



6



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SOFC-GT Combined Cycle System

Fuel

Inverter

Air

RecirculationBlower

SOFC

Combustor

Steam Turbine

7

Gas Turbine

Heat Recovery Steam Generator

Efficiency LNG : 70%-LHV (800MW-class)

Coal : 60%-LHV (700MW-class)


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Efficiency Improvement by combining SOFC with GT

50

55

60

65

70

75

ncy%n

etA

C/LHV

1400C class GTCC

1500C class GTCC

1700C class GTCC

SOFC-GT combined cycle

8

35

40

45

1100 1200 1300 1400 1500 1600 1700 1800

Turbine inlet temperature (T1T) (C)

Effic

ie

1200C class GTCC

Obtaining higher effect of efficiencyimprovements by combining SOFC

The efficiency of SOFC-GTCC is expected to improve 10% or more

compared with that of GTCC, since exhaust fuel and heat of SOFC are

able to use for operation of GT.


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(-netAC/L

HV)

Efficiency of SOFC-GTCC in various power range

70

6560

55

50

45

Central power station applyingSOFC-GT-ST combined cycle system

Residential, CommercialCHP using SOFC

SOFC-MGT combined cyclesystem (SOFC-MGTCC)

Central powerstation

9

Power (kW)

Efficienc

Industrial GE (special high voltage)Commercial, Industrial GE (high voltage)

4035

30

25

5,000 500,000

Cogeneration

10 25 200 400 600 800 1,000 3,000

Residential, CommercialCHP using PEFC

Residential, commercial GE (low voltage)

MGT: Micro Gas TurbineGE: Gas Engine

SOFC-GTCC is a key technology to realize sustainable society of reducingCO2 emissions, since high efficiency is obtained even in the system ofsmall capacity.


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Strategy of SOFC-GTCC development at MHI

Several hundreds MW classusing NG as fuel

Coal gasificationgas as fuel (IGFC)

Efficiency: 60%-LHV

Partial topping system for GTCC(SOFC : several tens MW class)

Efficiency: maximum +15%

Efficiency: 70%-LHV

10

20052010 2020

30

2015

200kW class CommercializationEfficiency: 5560%-LHVEfficiency: 52%-LHV

SOFC-MGTCC(200kW - several MW class)

Test result


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Contents

1. About Mitsubishi Heavy Industries (MHI)



11



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Development of 200kW-class SOFC-MGTCC

Improvement ofElemental Technology

Cell stack

Verification test of system integration

200kW-class SOFC-MGTCC System

Fuel

Air

MGT

SOFC

SOFC Module

12

Cartridge MGT Customization Preparatory Operation Tests

Module40kW classSub-Module

MGT Test StandLow-calorificFuel Combustor

PressureVessel

Micro Gas Turbine

Sub-Module


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Natural GasRecirculation

Blower

SOFC

TE

DPXDifferential pressure controlbetween fuel and air of SOFC

PX

Independent control of MGTfuel pressure at outlet ofrecirculation blower

Additional volumeof SOFC for MGT

Flow diagram of 200kW-class SOFC-MGTCC

13

Exhaust Gas

Air

Micro GasTurbine (MGT)

Combustor

Temperaturecontrol of SOFC

Recuperator

Air feed to SOFC atconstant pressure

Dual fuel combustor(1) Start up for natural gas(2) Depleted fuel of SOFC


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Appearance of the 200kW-class SOFC-MGTCC

14


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Initial performance of the 200kW-classSOFC-MGTCC

200

300

400

500

owerOutput

[kW-DC]

owerOutput[

kW-AC]

400

600

800

1000

ge[V],SOFC

Current[A]

emperature[

]

SOFC Current

SOFC Temperature

SOFC Power Output

Max. Power229kW Efficiency52%

15

0

100

0 10 20 30 40 50 60 70 80 90

SOFC

MGT

0

200

SOFCVo

lt

To age

MGT Power Output

Power Generation Hours [Hr]

Firstly starting MGT, SOFC temperature was raised, and then load current of SOFC wasincreased simultaneously after warming up to approximately 600C of the temperature.

The state of combined cycle power generation of SOFC and MGT was established, and229kW of maximum power and 52% of the maximum efficiency were achieved.


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40

60

80

100

120

Power()

400

600

800

1000

1200

Ctemperature()

SOFC Temperature SOFC Power

MGT Power

Stop Stop StopStop

Stop

Long-term operation result of the SOFC-MGTCC

16

0

20

0 500 1000 1500 2000 2500 3000 3500

Operation hours (h)

0

200 SO

F

Operation hours : 3,224hThermal Cycle : 4 Times

No degradation of SOFC performance.


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Results of the 200kW-class SOFC-MGTCC

200200200200

229229229229

204204204204

188188188188

41414141

17

50%50%50%50% 52.1%52.1%52.1%52.1% / / / /

0.25%/10000.25%/10000.25%/10000.25%/1000 0%/10000%/10000%/10000%/1000

3,2243,2243,2243,224


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Contents

1. About Mitsubishi Heavy Industries (MHI)



18



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Activity and progress of SOFC development

MHI joined to following NEDO projects.

(1) Durability and reliability improvementCollaborating with research institutions and universities to

understand degradation phenomena and to investigate ofdegradation mechanism.Improvement of Redox robustness.

19

-

in elevated pressureDevelopment of compact SOFC module and the preparatory test

in elevated pressure.Development of simplified system with improved reliability.

(3) Research of lower cost materials for cell stackCollaborating with stack developers and materials suppliers torealize the common specifications of cathode and anode materials.


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AirCathode

Electrolyte

Length : 1500 mm, diameter : 28mm

Segmented-in-series tubular cell stack

Air

20

n erconnec

Substrate tube

AnodeFuel

(, )(, )(, )(, )

(, )(, )(, )(, )

10101010 (, )(, )(, )(, )

Fuel


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O2Cathode

ElectrolyteInterconnect

Substrate tube

Anode

Weak point of the tubular cell stack

H2Fuel

Air

21

Issue : Relative density of interconnect region overlapping withelectrolyte is lower than that of the effective region.

Cross leak of hydrogen and oxygen through the interconnect.


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Damage process via anode re-oxidation

(1) Oxygen leak to anode side through interconnect.

(2) Volume expansion via re-oxidation of partial anode.

Steady: oxygen is consumed by hydrogen.Transient: oxygen reacts with Ni when hydrogen of anode

side is shortage for amount of leaked oxygen.

O2

22

(3) Inducing compression stressto reduced anode layer.

(4) Inducing tensile stresses to electrolyte/interconnect layerand inner side of substrate tube.

Fuel

(5) Cracks will be induced when the tensile stressexceeds the material strengths.

Increasing the relative density of interconnect by modifyingthe sintering characteristics.


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Characteristics of improved interconnect

90

100

110

120

edensity(%)

0.6

0.8

1.0

1.2

1.4

rength(-)

Relative density (%)

Sterngth (-)

0.6

0.8

1

1.2

nvoltage(V)

60

80

100

120

140

ower(W)

Fuel : H2/N2 = 70/30(H2 = 1.77Nl/m, N2 = 0.76 Nl/m)Oxidant : Air (11.6 Nl/m)Temperature : 900CPressure : 0.1MPa

23

Improvements of relativedensity and strength. Cell stack performance applying

improved interconnect is almost

equivalent to that of conventional type.

60

70

80

Conventional Improved

Relati

0.0

0.2

0.4

S

0

0.2

0.4

0 100 200 300 400

Current density (mA/cm2)

M

e

0

20

40

Voltage of conventionalVoltage of improvementPower of conventionalPower of improvement


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Comparison of N2 purge tolerance in anode

Fuel : H2/N2 = 5/95, N2 =100Oxidant : Air

Temperature : 900

CPressure : 0.1MPa

Cell voltages have not0.6

0.8

1

1.2

ltage(V)

Coventional cell stack Improved cell stack

Switching anode gasfrom H2/N2 to N2

Switching anode gasfrom N2 to H2/N2

Anode: (1)H2/N2(5/95) (2)N2 (3)H2/N2(5/95)

24

Redox robustness of the improved cell stack increased to about2 times than that of conventional cell stack.

Restriction relief of system managementSimplification of protection system.

Crack was inducedin the electrolyte orinterconnect.

0

0.2

0.4

-0.5 0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 8.5 9.5

Time (h)

Cellv

3.2h

Improved 6.2h


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25

-





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Durability test of LSM-YSZ interlayer

20

30

ltage[V]

0.92%/1,000h (9,000-10,000h)No.4 Cell-Stack

1.21%/1,000h (4,000-5,000h)No.3 Cell-Stack

0%/1,000h (1,500-2,500h)

No.2 Cell-Stack

0.22%/1,000h (1,500-2,500h)No.1 Cell-Stack

[V]

at CRIEPI (Central Research Institute of Electric Power Industry)

26

0 2000 4000 6000 8000 100000

10

Power generation hours [h]

0 1000 2000 3000

23

24

25

Cell-StackVo

No.4 Cell-StackNo.3 Cell-Stack

No.2 Cell-StackNo.1 Cell-Stack

Power generation hours [h]Ce

ll-StackVoltag

e


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Nernst loss (ne)

Anode Polarization

(RAJ)

Pressure : 0.101MPa

Temperature : 900C

Current Density : 150mA/cm2

Overvoltage analysis of the durability test

77 7787

35 30 45 56 64

1922

18 20 17

35 35 35 35 35

800

850

900

950

geofCell-St

acks[mV]

at CRIEPI

27

(RCJ)Ohmic Loss

(RIRJ)

Operating Voltage

750 751729

710 702

97

650

700

750

255 2487 5439 7960 9999

Power generation hours [h]

Averagevo

lta

Degradation is due to the increase of cathode polarizationand IR loss after 2500h.


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SEM Images of cathode/electrolyte interface

Initial

LSM/YSZ

YSZ

LSCM

3000h

YSZ

LSCMLSM/YSZ

28

5000h 10,000h

YSZ

LSCMLSM/YSZ LSM/YSZ

YSZ

LSCM

Interface Voids increased as durability test became long.


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Investigation on increase of cathode polarization

Cell Stack

Electric Furnace

Fuel Inlet

Fuel Injection tube

Air su l /0.00E+00

5.00E-08

1.00E-07

1.50E-07

2.00E-07

2.50E-07

integratedw

eightofCr(g)

Fuel Outlet

29

Amount of Cr diffusion increases in the three phaseboundary with operation time.

Cr poisoning is also a cause ofthe increase of cathode polarization.

Air OutletAir Inlet

exhaust tubeOperation time (h)Integrated weight of chromium deposition in theboundary layer of cathode/electrolyte of 4m as afunction of operation time.


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Durability test of SDC interlayerCathode interlayer : LSM-YSZ SDC

Air supply and discharge tube : metal and ceramic

0.7

0.8

0.9

voltage(V)

Ceramics tube wihout containing Cr

Metal tube containin Cr

Pressure : 0.101MPa

Temperature : 900C

30

0.5

0.6

0 2000 4000 6000

Operation time (h)

Mea

urrent ens ty : m cm

Fuel: H2/N2 = 70/30, Oxidant: airFuel utilization rate: 60%

Air Utilization rate: 20%

Degradation rate: LSM-YSZ using metal tube = 0.83 %/1000hSDC using metal tube = 0.38 %/1000h

SDC using ceramics tube = 0.23%/1000h

The increase of cathode polarization was also observed in SDC interlayer.


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MHIDurabilitytest

AISTSIMS, FE-SEM

Kyushu Univ.: STEM

K oto Univ.: FIB-SEM

CRIEPI: Performance anddurability evaluations

technology Understanding degradationphenomena and investigationof degradation mechanism

Cooperation framework in NEDO PJ

31

Tohoku Univ.:Mechanical analysis

MHISEM/EPMA

MHI: improvement of cell stack

Focus: investigation on the change of micro structureand element migration at the cathode side.


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32

-





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Comparison of module structures

Upper heatexchange part

Powergenerationpart

Lower heat

Fuel

Flow

Part

Upper

HEX

Part

Tubular

33

Conventionalcartridge

Compactcartridge

Compactness: 400 700 Cell-Stack/m2

Optimizing air flow and temperaturedistribution by simulating heat transfer.

AirFlow

Generatio

Lower

HEX

Part

Cell- stack


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Appearance of the compact cartridge

Pressure vessel

34

Compact cartridge Test stand


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I-V characteristics of compact cartridge

Pressure : 0.3MPaFuel: Natural gas

Oxidant: air

0.4

0.6

0.8

1.0

1.2

anvoltage(V)

35

The performance of compact cartridge is almostequivalent to that of conventional type.

0.0

0.2

0 200 400 600

Current density (mA/cm2)

M

Compact cartridge

Coventional module


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600

800

1000

1200

1400

gthdirection

(mm)

Test result (0.63V, UA=15%)

Test result (0.73V, UA=26%)

Simulation (0.7V, UA=17%)

Fuel inlet

Air outlet

Temperature distribution in the generation room

36

0

200

400

400 600 800 1000

Surface temperature ofcell stack (C)

Positionof

len

The compact cartridge also exchanged heat quantity as the designdemand, and the temperature distribution in generation room wasgood agreement with the simulation value.

Fuel outlet

Air inlet


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SOFC

MGT (MHI)Conventional

Conventional

Configuration and layout planning

37

SOFC

MGT (TOYOTA) CompactCompact

The footprint of improved system will become smaller to about 1/2than that of conventional system.


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300kW Class SOFC-MGT Combined Cycle System

MGT

Pressure Vessel

38

Total Net AC Output 300 kW Class

Electrical Net Efficiency >55 % (LHV)

Target performance.


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Conclusion1. 200kW-class SOFC-MGTCC test was successful, since

efficiency of 52.1% and the durability test of 3000h wasattained.

2. Durability and reliability improvement(1) Improvement of Redox robustness of the cell stack

by increasing the density of interconnect.

39

by applying SDC interlayer.(3) Obtaining the equivalent performance of the compact

cartridge as well as the conventional module.

We are accelerating the technological developments inbroad range to improve reliability, durability, compactnessand simplicity for the practical use of SOFC-MGTCC.


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Acknowledgments

This work was supported by

New Energy and Industrial TechnologyDevelopment Organization (NEDO).

40

We would appreciate NEDO.


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