diesel reforming for fuel cell auxiliary power units library/research/coal/energy systems... ·...
TRANSCRIPT
Fuel Cell Program
Diesel Reforming for Fuel Cell Auxiliary Power Units
SECA Core Technology Program ReviewAlbany NY, Sept 30 – Oct 1.
Rod Borup, W. Jerry Parkinson, Michael Inbody, Jose Tafoya, Will J. Vigil, and Dennis R. Guidry
Los Alamos National Laboratory
DOE Program ManagersSECA – Daniel Driscoll/Wayne Surdoval
POC: Rod Borup:[email protected] - (505) 667 - 2823
Fuel Cell Program
Potential Applications of Diesel Reformers in Transportation Systems
Diesel Exhaust
POx/SRLean NOxCatalyst
Fuel TankNOx Reductant
SOFCEngineEGR
SOFC Fuel
ReducedNOx ExhaustDiesel Engine
The reforming of diesel fuel potentially has simultaneous on-board vehicle applications:• SECA application: reforming of diesel fuel for SOFC / APU• reductant to catalyze NOx reduction• Hydrogen addition for high engine EGR • fast light-off of catalytic convertor
Fuel Cell Program
Diesel Reforming Tasks and Activities • Objectives: Develop technology suitable for on-board reforming of diesel fuel for transportation SOFC auxiliary power units
• Develop fundamentals (kinetics ….), models, examine components• Approach: Examine Catalytic partial oxidation and steam reforming• Modeling
• Carbon formation equilibrium modeling• Reformer operation with anode recycle
• Experimental• Development of direct diesel fuel injection• Adiabatic reformer operation
• Catalyst evaluation, activity measurements• Hydrocarbon breakthrough speciation
• Anode recycle simulation• Iso-thermal reforming and carbon formation measurements
• Carbon formation rate development• Catalyst regeneration due to carbon formation
Fuel Cell Program
Diesel Reforming MeasurementsAdiabatic Reactor with nozzle
ModelingEquilibrium
KineticCompositionIso-thermal Microcatalyst
Iso-thermal system• Measure kinetics• Steam reforming / POx• Light-off• Carbon formation
NozzleAir / anode recycle Catalyst(Pt/Rh)
Furnace
Window for Catalyst Reaction Zone Observation
Windows forlaser diagnostics
Fuel Cell Program
Relative Carbon Formation from Fuel Vaporization
-0.02
0
0.02
0.04
0.06
0.08
0.1
Diesel(commercial)
Diesel (low - S)
Kerosene(commercial)
Kerosene(low-S)
Hexadecane Dodecane
Rel
ativ
e C
arbo
n Fo
rmat
ion
Dur
ing
Fuel
Ref
luxi
ng
• Saturated pure diesel components do not show pyrolysis• S removal, decreases carbon formation (removes PAHCs)• Diesel fuel injection require technology to avoid carbon formation
during vaporization
Fuel Cell Program
Direct Fuel Nozzle Operation
Simulated Anode ExhaustRecycle (H2, CO, CO2, N2, H2O, HCs)
POx/SR
Noble metalReticulated foam
Supported Catalyst
Fuel Tank
Air
Fuel PressureRegulator
P
Nozzle
• Directly inject fuel to reforming catalyst• Commercial nozzle, control fuel pressure for fuel flow (~ 80 psi)• Air / anode recycle (H2 / N2) distribute in annulus around fuel line / nozzle
• Experimental results• Operated successfully at steady state
• Minimum fuel flow dictated by fuel distribution from nozzle• Requires control of fuel/air preheat, limiting preheat (~ < 180 oC)
• Prevents fuel vaporization/particulate formation
Flowmeter
Fuel Cell Program
SOFC Anode Recycle to Reformer! Water Addition
POx/SR
Fuel Tank
SOFC
Anode RecycleStream
Exhaust
AirReformate
• Methods for water introduction and availability:• Separate water tank (tank, freezing)• Anode water recovery by condensation (heat ex., cond., tank, pump freezing)• Anode recycle to reformer (blower)
Currently simulating anode recycle with N2/H2 mixture
Fuel Cell Program
SOFC Anode Recycle Modeling
Green – Fractional increase in flow due to increasing gas volume due torecycle ratio, leads to larger reformer
800
820
840
860
880
900
920
940
960
0 10 20 30 40 50 60
Recycle Rate / %
Out
let T
empe
ratu
re /
o C
0
0.2
0.4
0.6
0.8
1
1.2
S/C
and
Ref
orm
er O
utle
t Flo
wra
te
Frac
tiona
l Inc
reas
e
Outlet Temp at O/C = 1
S/C
Reformer Outlet FlowrateFractional Increase
Fuel Cell Program
Hydrogen / CO production
Pt / Rh supported catalystResidence time ~ 20 msecAnode recycle simulated with H2, N2, H2O
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.8 0.9 1 1.1 1.2 1.3 1.4
Oxygen / Carbon Ratio
Con
cent
ratio
n / %
H2 (40% Recycle)CO (40% Recycle)H2 + CO (40% Recycle)H2 (30% Recycle)CO (30% Recycle)H2 + CO (30% Recycle)
CO
H2
H2 + CO
30 % Recycle
30 % Recycle
30 % Recycle
40 % Recycle
40 % Recycle
40 % Recycle
Fuel Cell Program
760
780
800
820
840
860
880
900
920
940
0.8 0.9 1 1.1 1.2 1.3 1.4
Oxygen / carbon ratio
Ref
orm
er O
utle
t Tem
pera
ture
/ o C
40 % Recycle30 % Recycle
Reformer temperature during diesel reforming
• Higher recycle reduces operating temperature• Operation with recycle < 30 % difficult due to high operating
temperatures and catalyst sintering
Model Pts
Fuel Cell Program
Reformer Outlet Hydrocarbon Speciation
• Complete hydrocarbon conversion:• Higher O/C reduces HCs• Higher residence and catalyst loading reduces HCs
• Gasoline/PEM reforming durability work shows HCbreakthrough at ~ 500 – 750 hours
0
0.2
0.4
0.6
0.8
1
1.2
0.8 0.9 1 1.1 1.2 1.3
Oxygen / Carbon Ratio
Hyd
roca
rbon
Con
cent
ratio
n / %
.
C1C2C3C4
Fuel Cell Program
Light-off of Reformer with Diesel
• Light-off requires preheating of catalyst • Degree of preheat depends upon fuel• Higher HCs and aromatics require higher
Preheat temperatures for light-off
Repeated light-offs show an increase in temperature required to achieve light-off
100
120
140
160
180
200
220
240
260
280
iso-
octa
ne
Isoo
ctan
e X
ylen
e
Isoo
ctan
e an
thra
cene
Isoo
ctan
e n
apth
alen
e
RFG
Kero
sene
Low
S D
iese
l
Die
sel
Ligh
t-off
Tem
pera
ture
/ o C
150
175
200
225
250
275
300
1 2 3 4 5 6 7 8 9 10
Run #
Tem
pera
ture
/ o C
Low Sulfur Diesel Fuel - CatalystDiesel Fuel (Set #2) - Catalyst T
Fuel Cell Program
Carbon Formation Equilibrium Modeling• Various forms of carbon exist
• (different forms of carbon exist in the literature, and different forms have been observed during reforming)• Commercial codes handle vapor, liquids
• Difficult to deal with solids as 3rd phase • Difficult to input of thermodynamics components
• Different carbon forms have different thermodynamic characteristics
• Developed chemical equilibria code to analyze conditions for carbon formation• Includes 3 types of amorphous carbon
• Dent Carbon (C1)• Boudart Carbon (C2)• Water gas carbon (C3) – (limited thermodynamic data)
• Operation of model in iso-thermal modes (adding adiabatic)• C++ Code operates on Windows PC
Fuel Cell Program
Model Operation & Availability• Specify:
• Isothermal• Adiabatic (needs improvement for amorphous Carbon)
• Gas phase components & concentrations• Equilibrium temperature• Pressure• Types of solid phase
• Output yields (code works where carbon formation is observed)• gas phase concentration• solid phase quantities• (Delta H reaction, outlet temperature – for adiabatic case)
•Model is (will be) available • no-cost (or nominal), non-exclusive to SECA industry teams
Fuel Cell Program
Carbon Disappearance Temperature with Recycle Ratio
500
600
700
800
900
1000
1100
1200
1300
0 10 20 30 40 50 60Recycle Rate / %
Car
bon
Dis
appe
aran
ce T
empe
ratu
re /
o C
Disappearance of all types of amorphous carbon
Fuel Cell Program
Carbon Formation Dependence on Recycle Ratio
• Dent Carbon (C1)• Boudart Carbon (C2)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
600 700 800 900 1000 1100 1200 1300
Temperature / oC
Rel
ativ
e C
arbo
n Fo
rmat
ion
/ Mas
s
C12 - 0% RecycleC12 - 10% RecycleC12 - 20% RecycleC12 - 30% RecycleC12 - 40% RecycleC12 - 50% Recycle
Fuel Cell Program
Carbon Formation:Competing effects kinetics vs. equilibrium
0
0.05
0.1
0.15
0.2
0.25
500 550 600 650 700 750 800 850
Reforming Temperature / oC
Rel
ativ
e C
arbo
n fo
rmat
ion
/ g
Low Sulfur DieselCommercial Diesel
Conditions:Iso-thermal operationTotal O/C = 1.0Pt/Rh support catalystResidence Time = ~ 30 msec
Low temperature – high equilibrium / low kineticsHigh temperature – low equilibrium / high kinetics
Fuel Cell Program
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.00088 0.00092 0.00096 0.001 0.00104
1/Temperature (K)
Car
bon
Form
atio
n
Carbon Formation MeasurementsIso-thermal operationCarbon formation trends with equilibrium at high temperatures
Trends with T (kinetic effect) at lower temperaturesCarbon Formation linear vs. 1/T
Adiabatic operationCarbon formation trends with equilibrium
Carbon decreases with increasing temperatureCarbon Formation linear vs. T
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
950 1000 1050 1100 1150Temperature / K
Car
bon
Form
atio
n
0
0.1
0.2
0.3
0.4
0.5
0.6
0.001 0.00104 0.00108 0.00112 0.00116 0.00121/Temperature (K)
Car
bon
Form
atio
n
Commercial DieselLow Sulfur Diesel
Fuel Cell Program
Carbon AnalysisThermal Gravimetric analysis of catalyst post-carbon forming measurements
Carbon is not typically ‘bound’ to catalyst surface (for noble metal catalysts)
Carbon removal is about 0.4 % catalyst weight
90
92
94
96
98
100
102
0 200 400 600 800 1000 1200
Temperature / oC
Cat
alys
t wei
ght /
%
Fuel Cell Program
Summary/Findings• Direct fuel injection via fuel nozzle
• Control of fuel temperature critical• Prevent fuel vaporization, fuel pyrolysis / clogging of nozzle• Potentially limited turn-down with nozzle
• Reformer operation with SOFC anode recycle• High adiabatic temperatures at low recycle rates
• Leads to catalyst sintering• Limits light-off of reformer
• High recycle increases reformer size, parasitic losses• Operation at 30 – 40 % recycle rate reasonably successful
• Limited success at lower (<20 % recycle rates due to high adiabatic T)• Carbon Formation
• Equilibrium carbon formation modeling• Equilibrium code available for iso-thermal carbon formation cases
• Experimental carbon formation measurements show kinetic effects and equilibrium effects
Fuel Cell Program
Future Activities - Modeling
• Modeling • Make model available for SECA industrial teams (Beta version)
• (no or nominal cost , non-exclusive license)• Model improvements
• Incorporate other carbon species enthalpies (CH0.2)• Incorporate sulfur into equilibrium code• Improve code robustness & make ‘user friendly’
• Examine system effects of anode recycle (efficiency and parasitics)
Fuel Cell Program
Future Activities - Experimental• Experimental
• Examine reformate effect on SOFC• Effect of hydrocarbon ‘breakthrough’ on SOFC
• incorporate SOFC ‘button’ cell operating on reformate• Sulfur effect on reforming kinetics• Carbon formation as function of catalyst, recycle ratio
• Reformer design considerations• Durability – catalyst sintering• Turndown – fuel / air feed preparation• Stand-alone start-up & consideration to avoid C formation• Recycle ratios – evaluate various anode recycle ratios
• ‘real’ recycle – incorporate major/minor constituents