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