Fuel Processing of Diesel for Fuel Cells
National Energy Technology Laboratory
June 19, 2002
David A. Berry, Todd H. Gardner, Robert James, William Rogers, and Dushyant
Shekhawat
2002 SECA CORE REVIEW
Descriptor - include initials /org#/date
Diesel Fuel ProcessingTechnical Issues Addressed
• Diesel fuel is complex and difficult to reform :• Diesel fuel is a complex, multi-component (>100 compounds) sulfur-
containing fuel that exhibits varying reaction pathways and kinetic rates for differing fuels and catalyst types.
• Deactivation of fuel reforming catalysts and fuel cell components via carbon deposition and sulfur poisoning are the principle technology barriers.
• System integration can be a significant challenge:• Reformer integration with fuel cell system requires desulfurization,
water management, and thermal considerations. • Certain FC applications may require high power density design with
“fast” response and high efficiency for both steady-state and transient operations.
• Hydrocarbon slip must be avoided to provide fuel cell with a clean synthesis gas.
Descriptor - include initials /org#/date
Diesel Fuel ProcessingR&D Objectives
• Develop fundamental understanding of diesel fuel processing and provide necessary tools and information to fuel cell/fuel process developers and system integrators for technology development, performance optimization, and system control.
Descriptor - include initials /org#/date
Diesel Fuel ProcessingTechnical Approach
• Utilize CFD Models to Understand and Address Heat and Mass Transfer Issues and Reactor Performance for Steady State and Transient Analysis
• Conduct Systems Analysis to Understand Reformer Integration and Operational Requirements
• Conduct Kinetic Rate Determination Studies in the Laboratory to Allow for Predictive Modeling and Design
ATR Reactor
Combustor
Fuel CellStack
ZnOSorbent
Bed
HeatExchanger
HeatExchanger
250 C
300 C800 C
650 C
Recycle
Air In
Fuel In
Exhaust
Descriptor - include initials /org#/date
Combustor
AutoThermalReformer
DesulfurizerSorbent Bed
ExhaustCondenser
SteamGenerator
Air Preheater
Air Compressor
Fuel Pump
Water Pump
800 C SECA APU
FuelCell
StackCathode
Anode800 C800 C
800 C
800 C
650 C
Diesel Fuel ProcessingSystems Analysis Results - High Efficiency Diesel Fuel Processor
Descriptor - include initials /org#/date
Combustor
AutoThermalReformer
DesulfurizerSorbent Bed
ExhaustCondenser
SteamGenerator
Air Preheater
Air Compressor
Fuel Pump
Water Pump
800°C NETL APU
FuelCell
Stack Cathode
Anode800 C800 C
800 C
800 C
700 C
650 C
Goals:- Maximize Thermal Integration- Flexible System Startup
Diesel Fuel ProcessingSystems Analysis Results - Integral Combustor/Reformer
Descriptor - include initials /org#/date
Diesel Fuel ProcessingSystems Analysis Results - Effect of Heat Integration
Shared Heat Non-Shared Heat
Fuel (kg/hr) 0.834 0.834
Air – Stoichs In 5.5 5.2
ATR F/A Ratio 9 3.5
Steam/C Ratio 0.8 0.8
Efficiency 49.8 42.39
Net Power 5.0 4.221
ATR Temperature 800 800
FC Temperature 845 813
Descriptor - include initials /org#/date
Diesel Fuel ProcessingSystems Analysis - Effect of Heat Integration
Shared Heat Non-Shared Heat
Fuel (kg/hr) 0.834 0.834
Air – Stoichs In 5.5 5.5
ATR F/A Ratio 9 9
Steam/C Ratio 0.8 0.8
Efficiency 49.8 47.16
Net Power 5.0 4.734
ATR Temperature 800 565
FC Temperature 845 745
Descriptor - include initials /org#/date
Diesel Fuel ProcessingSystems Analysis - Effect of Heat Integration
800 C SECA APUNon-Shared Heat Concept
564 C
745 C
855 C
564 C
650 C
277 C
307 C
272 C
25 C
Air Inlet
Fuel Inlet
Steam
25 C
Combustor
AutoThermalReformer
DesulfurizerSorbent Bed
ExhaustCondenser
SteamGenerator
Air Preheater
Air Compressor
Fuel Pump
Water Pump
FuelCell
Stack
Descriptor - include initials /org#/date
0.00
00
0.15
00
0.30
00
0.45
01
0.60
01
0.75
01
0.90
01
03.5
70
2
4
6
8
10
12
14
16
CO Molar Flow
(kmol/hr)
O2/C Ratio
Steam/C Ratio
CO Molar Flow vs. O2/Steam/C Ratio
0.00
00
0.15
00
0.30
00
0.45
01
0.60
01
0.75
01
0.90
010
4
8
0
5
10
15
20
25
30
35
H2 Molar Flow
(kmol/hr)
O2/C Ratio
Steam/C Ratio
H2 Molar Flow vs. O2/Steam/C Ratio
Diesel Fuel ProcessingSystems Analysis - ATR Oxygen & Steam Sensitivity
Descriptor - include initials /org#/date
• Develop a ATR model in Fluent− Fuel atomization and vaporization− Partial oxidation of diesel fuel− Steam reforming of diesel fuel− Combustion of anode exhaust gas
• Obtain reaction kinetic expressions from− Catalyst manufacturer− Literature− Experiments
• Conduct steady state simulations and validate model with ATR experimental data
• Conduct transient simulations− Use the simulation results to study reformer performance− Export temperature fields into ANSYS and calculate the
thermal stresses
Diesel Fuel ProcessingCFD Modeling - Approach
Descriptor - include initials /org#/date
ATR Region
Anode Exhaust Combustor
Outer Diameter = 6 in.
Inner Diameter = 2 in.
Length = 12 in.
Diesel Fuel ProcessingCFD Modeling Results - ATR Model Prototype Geometry
Descriptor - include initials /org#/date
Diesel Fuel ProcessingCFD Modeling Results - Reaction Zones
Anode Exhaust Combustor
Catalytic Steam Reforming
Fuel Spray Vaporization and POX
Length = 6 in.
Length = 6 in.
Descriptor - include initials /org#/date
ATR Model Inlet Conditions
Fuel Spray
C8H18
0.2 g/s
Nozzle Air
21% Vol. O279% Vol. N2
0.2g/s
650C/923K
Steam
0.18g/s
Anode Exhaust
5%Vol. H23%Vol. CO 21% Vol. CO236% Vol. H2O 35% Vol. N2
1.6g/s
800C/1073K
Cathode Exhaust
18% Vol. O282% Vol. N20.2g/s 650C/923K
Descriptor - include initials /org#/date
ATR Model Results
CO Mole Fraction
H2 Mole Fraction
Descriptor - include initials /org#/date
Diesel Fuel ProcessingReaction Rate Determination - Modeling Approaches
Level 1Intuitative Lumping
Level 2Mechanism Based
Lumping
Level 3Structure Oriented
Lumping
Level 4Mechanistic
• Lumps derived fromintuition (grossidentification oflumping groups), e.g.paraffins, aromatics,etc.
• Little is knownregarding the exactmechanism
• Psuedo-1st order
• Psuedo-homogeneous phase
• Easy to develop,inexpensive
• Suitable for processsimulators, e.g.ASPEN, ChemCad
• Predicts transientresponse andhydrocarbon slip
• Psuedo-homogeneous phase
• Based on psuedo-species lumpedtogether based onthe elucidation of adetailed mechanism
• Requires aknowledge ofprocess chemistry
• Must possess theanalytical ability tomeasure thepsuedo-species only
• Suitable for processsimulators, e.g.ASPEN, ChemCad
• Predicts transientresponse,hydrocarbon slip,coking and catalystdeactivation
• State of the art incomplex mixturemodeling
• Closely resemblespure mechanisticapproach
• Involves lumpingisomers only
• Detailed knowledgeof process chemistryneeded, expensiveanalytically
• Detailed kineticstudies needed forthe development oflumps
• Suitable for CFDpackages, e.g.Fluent
• Pure mechanisticapproach
• Detailed kineticstudies of singlecomponents andtheir mixtures
• Development ofexperimentalprocedures toevaluate processchemistry
• Knowledge ofcatalyst propertiesneeded
• Requiresspectroscopicmethod
• Predicts transientresponse,hydrocarbon slip,coking and catalystdeactivation basedon fundamentals
Descriptor - include initials /org#/date
C {-R}n
{-R}n
{-R}n
C {-R}n H2 + CO + CO2
O2/H2O
O2/H2OO2/H2O
O2/H2O
AromaticsAromatics
ParaffinsParaffins
NaphthenesNaphthenesOlefinsOlefins
Diesel Fuel ProcessingReaction Rate Determination - Complex Reaction Network
Descriptor - include initials /org#/date
Product Distribution from ATR of Diesel(T=850 C, O2/C=0.3, S/C=1.5)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
15 25 35 45 55 65 75Residence Time (10-3 sec)
(Mol
e of
H2/C
O fo
rmed
per
mol
e of
C in
fe
ed)
H2 (Ru)CO (Ru)H2 (Pt)CO (Pt)H2 (Pd)CO (Pd)
Descriptor - include initials /org#/date
Diesel Fuel ProcessingExperimental Vs Predicted Values for Diesel ATR on Pt/Al2O3
R2 = 0.91
0.0015
0.0025
0.0035
0.0045
0.0055
0.0015 0.0025 0.0035 0.0045 0.0055
Experimental, [-dCHC/dt]
Pred
icte
d, [-
dCH
C/d
t]
-rHC=k0exp(-8315/T)CHC0.87CH2O
-1.02CO2-0.13
Descriptor - include initials /org#/date
Diesel Fuel ProcessingExperimental Vs Predicted Values for Diesel ATR on Pd/Al2O3
R2 = 0.90
0.0015
0.0025
0.0035
0.0045
0.0015 0.0025 0.0035 0.0045
Experimental, [-dCHC/dt]
Pred
icte
d, [-
dCH
C/d
t]
-rHC=k0exp(-8260/T)CHC0.74CH2O
-1.07CO20.10
Descriptor - include initials /org#/date
Diesel Fuel ProcessingExperimental Vs Predicted Values for Diesel ATR on Ru/Al2O3
R2 = 0.72
0.0025
0.0035
0.0045
0.0055
0.0065
0.0075
0.0085
0.0095
0.0025 0.0035 0.0045 0.0055 0.0065 0.0075 0.0085 0.0095
Experimental, [-dCHC/dt]
Pred
icte
d, [-
dCH
C/d
t]
-rHC=k*exp(-4860/T)CHC0.50CH2O
-1.39CO2-0.03
Descriptor - include initials /org#/date
• Diesel-based 5-kWe fuel cell APU system with 45% -50% electrical conversion efficiency identified
• A prototype CFD model including all the key elements of ATR has been developed− Developed a model that accounts for fuel atomization and
vaporization, partial oxidation, steam gasification, and anode exhaust gas combustion
− Tested the convergence behavior of the model
• Laboratory Kinetic Experiments Conducted− Tested Pt, Pd, and Ru catalysts− Initial rate measurements made for hexadecane and diesel fuel
Diesel Fuel Processing2002 Results Accomplishments
Descriptor - include initials /org#/date
• Diesel-based 5-kWe fuel cell APUs are considered a significant high volume market for SOFC’s.
• Fundamental understanding of diesel reforming and general methodology for kinetic rate determination would be very beneficial to catalyst developers. May extend to hydrocarbon fuels in general.
• A validated CFD model would be useful to fuel reforming developers and system integrators to predict steady-state and transient performance, develop control strategies, maximize efficiency, and minimize cost.
Diesel Fuel ProcessingApplicability to SOFC Commercialization
Descriptor - include initials /org#/date
Diesel Fuel ProcessingFuture Plan
2002 2003 20062004 2005
PREDICTIVE CFD MODEL DEVELOPMENT FOR PREDICTIVE CFD MODEL DEVELOPMENT FOR DIESEL REFORMINGDIESEL REFORMING
- ValidateLEVEL 1 KINETIC MODELLEVEL 1 KINETIC MODELDEVELOPMENTDEVELOPMENT
LEVEL 2 KINETIC MODELLEVEL 2 KINETIC MODELDEVELOPMENTDEVELOPMENT - Validate
LEVEL 3 KINETIC MODELLEVEL 3 KINETIC MODELDEVELOPMENTDEVELOPMENT
DEVELOP KINETIC RATEDEVELOP KINETIC RATEMETHODOLOGYMETHODOLOGY
CONDUCT DESIGN & EVALUATION OF DIESEL REFORMING TECHNOLOGYCONDUCT DESIGN & EVALUATION OF DIESEL REFORMING TECHNOLOGY