MOLTEN CARBONATE FUEL CELLSMOLTEN CARBONATE FUEL CELLS

ANSALDO FUEL CELLS: Experience & ANSALDO FUEL CELLS: Experience & Experimental resultsExperimental results

Filippo Parodi /Paolo Capobianco (Ansaldo Fuel Cells S.p.A.)

Roma , 14th & 29th March 2007

MOLTEN CARBONATE FUEL CELLSANSALDO FUEL CELLS EXPERIENCEElements of Fuel Cell TheoryElements of Fuel Cell Theory

Evaluation of the characteristic Evaluation of the characteristic

parametersparameters

Flow diagram of a typical MCFC plantFlow diagram of a typical MCFC plant

ANSALDO Fuel Cells experienceANSALDO Fuel Cells experience

Experimental resultsExperimental resultsFilippo Parodi (Ansaldo Fuel Cells S.p.A. - Italy)

Roma , 14th March 2007

MOLTEN CARBONATE FUEL CELLSANSALDO FUEL CELLS EXPERIENCE

FUEL CELL IS A DEVICE ...

DIRECTLY TRANSFORMS THE CHEMICAL ENERGY OF THE FUEL INTO ELECTRICAL ENERGY BY ELECTROCHEMICAL REACTIONS

Anode Cathode

Electrolyte

e-

Electrical Energy

CO3=

O =

H +

H +

OH -

H +

AFC

PEFC

DMFC

PAFC

MCFC

SOFC

H2

H2

H2

H2

H2

H2O

H2O

CO2

H2O

CH3OH

O2

O2

O2

O2

O2

O2

H2O

H2O

H2O

CO2

100 °C

80 °C

80 °C

200 °C

650 °C

1000 °C

Fuel

H2

Oxygen

Air

FUEL PROCESSING

CO2 H2O

FUEL

FUEL CELL

OXYGEN

H2

ELECTRICENERGY

HEAT

FUEL

OXYGEN

CO2, NOx, SOx, particulate, ash

ELECTRICENERGY

COMBUSTION

THERMAL TO MECHANIC CONVERSION

Heat losses

MECHANIC TO ELECTRICAL CONVERSION

Mechanical losses

Steam/Gas Turbine Alternator

FUEL CELLS BASED vs. CONVENTIONAL ENERGY PRODUCTION PROCESS

Direct energy conversion (no combustion) Less conversion steps / Lower energy losses Higher efficiency

Environmental benefit No moving parts in the energy converter, Low maintenance , Low

noise Low exhaust emissions,

Modularity Modular installations to match load and increase reliability Size flexibility Good performance at off-design load operation

Fuel flexibility hydrogen, Natural Gas, biogas, biomass gasification, landfill gas,

reformed heavy fuels Possibility of remote/unattended operation

Fuel Cells based vs. conventional power systems

Fuel Cells Technologies

AFC PEMFC PAFC MCFC SOFC

Electrolyte Potassiumhydroxide

IonExchangeMembrane

ImmobilisedLiquid

PhosphoricAcid

ImmobilisedLiquidMolten

Carbonate

Ceramic

OperatingTemperature 100°C 80°C 205°C 650°C 800-1000°C

ChargeCarrier OH- H+ H+ CO3

= O=

CatalystNi, Ag,nobelmetals

Platinum PlatinumNot

requiredNot

required

Fuel H2 H2 H2 H2, CO H2, CO

Oxidant O2 O2 / Air Air Air, CO2 Air

Poisons CO, CO2,CH4, S

CO, CO2, S CO, S S S

AFCo selects as most promising FC technology:

Operating temperature about 650°C

No noble metal catalysts are used into the stack

Uses carbon monoxide as fuel and carbon dioxide as cathode reactant

Allows much simpler reforming section

Allows coupling to gas turbine hybrid cycles (higher efficiencies)

Plants up to 1- 2 MW size, for stationary applications, demonstrated in USA & Japan

MCFC

Ansaldo Fuel Cells Labs MCFC single cells

Electrochemical Reactions:CO2 + ½ O2 +2e- CO3

- - cathode

H2 + CO3- - H2O + CO2 + 2e- anode

----------------------------------------------------H2 + ½ O2 H2O overall reaction

Materials:

anode: Ni / Cr

cathode: Li x Ni 1-x O

matrix: LiAlO2

electrolyte: K2CO3 e Li2CO3

MCFC STACKS

single cell voltage = 0.6 - 1 V

current = up to 1000A

DC

To obtain the required electrical

voltage and power, many cells

are connected in series to build

the MCFC Stack

MCFC stack components and manufacturing

These aspects will be shown on the next lesson

Working principles of Fuel Working principles of Fuel

CellsCells

MCFC technologyMCFC technology

Key materials and Key materials and

componentscomponents

Technological Technological

developmentdevelopment

LAB level testsLAB level tests

29/03/07

Paolo Capobianco Ansaldo Fuel Cells S.p.A.

Responsible for laboratories

Elements of Fuel Cell theory Characteristic parameters

Reversible cell potential temperature effects operating pressure effects reversible cell potential calculation

cell voltage out of reversibility polarisation effects: activation, ohmic, concentration experimental data on MCFC thermal management and operating ranges

MCFC based power plants fuel reforming + MCFC mass balance performance experimental results

reversible cell potential

The Fuel Cell is a device that directly transforms chemical energy of the fuel into

electric energy by mean of electrochemical reactions.

From the thermodynamic point of view:

for electro-chemical reactions

VPUH

A C

+-

H2 O2

H+

RL

e-

VPUHP

LQU

elWVPW

at constant pressure:

1st Principle of Thermodynamics:

for reversible transformations: STQ

From the thermodynamic point of view:

reversibie cell potential definition

W e l i s r e l a t e d t o a n o d e a n d c a t h o d e v o l t a g e s :

revArevCel VVFnW ,,

w i t h :n N u m b e r o f e x c h a n g e d e l e c t r o n s i n t h e u n i t r e a c t i o nF F a r a d a y ’ s c o n s t a n tV C , r e v r e v e r s i b l e c a t h o d e p o t e n t i a lV A , r e v r e v e r s i b l e a n o d e p o t e n t i a l

F r o m t h e r m o d y n a m i c s t h e G i b b s p o t e n t i a l i s

revArevCPPVVFnSTHG ,,

d e f i n i n g t h e r e v e r s i b l e c e l l p o t e n t i a l a s :

revArevCrev VVE ,,

w e h a v e t h e d i r e c t r e l a t i o n s h i p b e t w e e n a v a i l a b l e c h e r m i c a l e n e r g y G a n d t h e e l e c t r i c p o t e n t i a l E r e v

revPEFnG

Temperature effects on Erev

Fn

S

T

Erev

OHOH 222 21

T

[K]

T

[°C]

-G

[cal/gmole]

-H

[cal/gmole]

S

[cal/gmole K]

298 25 54583 57973 -11.4

600 327 51147 58342 -12.0

800 527 48610 58757 -12.7

1000 727 46005 59034 -13.0

1250 977 42615 59633 -13.6

1500 1227 39202 59702 -13.7

0

T

Erev

Temperature effects on Erev

DG = -0,0012T2 - 10,621T + 57895

DH = -0,0002T2 + 1,886T + 57371

E = -3E-08T2 - 0,0002T + 1,2551

0

10000

20000

30000

40000

50000

60000

70000

0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600

T [K]

- D

G [

cal/

g m

ole]

- D

H [

cal/

g m

ole

]

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

E (

T, 1

ata)

[V

]

-DG

-DH

E (T, pi=1ata)

Operating pressure effects on Erev

OHOH 222 21

nF

V

P

E

T

rev

0

T

rev

P

E

DCBA

tsreac

products

react

products

p

pTRGG

tan.

00 ln

react

products

react

productsrevrev

p

p

nF

TRTEE

ln)(*

**

react

products

react

productsrevrev

p

p

nF

TREE

ln0

0

Operating pressure effects on Erev

2322

22232

221

2

COeOCOcatodo

eCOOHCOHanodo

AA

C

CCA COOHOCOH ,22

650

,2,2,2 21

2

1

,,,

,,*

222

22ln2

)(COCCOAH

ACOAOHrevrev

ppp

pp

F

TRTEE

21

,,,

21

,,*

222

22ln2

)(COCCOAH

ACOAOHrevrev

xxx

Pxx

F

TRTEE

Erev : study case calculation for MCFC

T [K] 923P [ata] 3.5

CATODO ANODO O2 10.2 H2 51.0 %molCO2 6.2 CO2 6.6 %molH2 O 21.0 CO 8.2 %molN2 62.6 H2 O 33.4 %mol

N2 0.0 %molCH4 0.8 %mol

E*rev (923K) = 1045 mV

Erev (923K) = 1039 mV

21

,,,

21

,,*

222

22ln2

)(COCCOAH

ACOAOHrevrev

xxx

Pxx

F

TRTEE

Erev: pressure effects on MCFC

1.010

1.015

1.020

1.025

1.030

1.035

1.040

1.045

1.050

1.055

1.060

1 2 3 4 5 6 7 8 9 10

P [ata]

Ere

v [

V]

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

dEre

v/dP

[m

V/a

tm]

E*

Erev(P) a 650°C

dErev/dP

Elements of Fuel Cell theory Characteristic parameters

Reversible cell potential temperature effects operating pressure effects reversible cell potential calculation

cell voltage out of reversibility polarisation effects: activation, ohmic,

concentration experimental data on MCFC thermal management and operating ranges

MCFC based power plants fuel reforming + MCFC mass balance performance experimental results

cell voltage on load

LR

VI revEV

A C

+-

combustibile

H+

RL

ne-

ossidante

I

fuel oxidant

out of reversibility conditions

cell voltage on load

revEV

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

1.5

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

i

V

Erev

OCV

A

B

C

OCV-A: polarization for activation

Erev-OCV: parasitical reactions

A-B: linear voltage drop - ohmic behaviour

B-C: polarization for concentration

concattirev IREV

Elements of Fuel Cell theory Characteristic parameters

Reversible cell potential temperature effects operating pressure effects reversible cell potential calculation

cell voltage out of reversibility polarisation effects: activation, ohmic,

concentration experimental data on MCFC thermal management and operating ranges

MCFC based power plants fuel reforming + MCFC mass balance performance experimental results

Experimental results on a MCFC stack

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

1400

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Current Density [A/m²]

Cel

l Ave

rag

e V

olt

age

[m

V]

0,00

0,20

0,40

0,60

0,80

1,00

1,20

1,40

Po

wer

Den

sity

[

KW

/m²]

design condition

By courtesy of Ansaldo Fuel Cells SpA

Voltage vs current characteristic curve is linear: V = Erev - Rpol • I

Negligible activation and parasitic voltage loss

High current density design condition is possible

Concentration effects

experimental results on MCFC single cell

0 500 1000 1500 2000 2500 30000.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

H2 Concentration

Experimental Simulation

Cel

l Vo

ltag

e [V

]

Current density [A/m2] By courtesy of Ansaldo Fuel Cells SpA

can be measured only for gas

compositions very poor in H2

or

at very high current densities

good agreement with simulated

values

Elements of Fuel Cell theory Characteristic parameters

Reversible cell potential temperature effects operating pressure effects reversible cell potential calculation

cell voltage out of reversibility polarisation effects: activation, ohmic,

concentration experimental data on MCFC thermal management and operating ranges

MCFC based power plants fuel reforming + MCFC mass balance performance experimental results

Thermal management on MCFC results from detailed simulation code (*)

(*) By courtesy of Ansaldo Fuel Cells SpAand PERT group of Genoa University

exothermal electrochemical

reaction

power generation produces heat

excess in the cell

thermal management need to

avoid high temperature damaging

of components

high gas flow rate is used to cool

down the stack

Thermal management on real MCFC

STACK MCFC - experimental data

temperature distribution on the cell plane

700-710

690-700

680-690

670-680

660-670

650-660

640-650

630-640

620-630

610-620

600-610

By courtesy of Ansaldo Fuel Cells SpA

typical operating ranges

operating parameter typical values management

temperature 580 < T < 700°Ccooling system: cathode gashigh flow ratesexhaust gas recirculation

pressure and pressure drops1 5 atmP anode/cathode < 20 mbar

pressurised sytemsallows higher performance,higher flow rates and lowerpressure drop

fuel utilisationoxidant utilisation

75% 56%

prevent concentration effectson V vs. I curve

CO2 5%

necessary for cathode reaction

available by recirculation ofanode exhaust to cathode(catalytic burner)

Oxygen concentration 10%necessary for cathode reactionand catalytic burner combustion

pollutants H2S, HCl, NH3, trace metals proper clean up systems

AIR TREATEMENT

FUEL CELLS

DC / AC

(DC / DC)

FUEL

COGENERATION

CONTROLSYSTEM

FUEL processor

AIR

H2

O2

Steam+

heat Steam+

heat

Fuel Cells Plant Concept

to accomplish with proper

operating ranges the fuel cell

need of a Balance of Plant

tailored on the application

MOLTEN CARBONATE FUEL CELLSANSALDO FUEL CELLS EXPERIENCE

Elements of Fuel Cell TheoryElements of Fuel Cell Theory

Evaluation of the characteristic Evaluation of the characteristic

parametersparameters

Flow diagram of a typical MCFC plantFlow diagram of a typical MCFC plant

ANSALDO Fuel Cells experienceANSALDO Fuel Cells experience

Experimental resultsExperimental results