1. Affect of Biodiesel Blends on DPF and SCR Systems
Aaron Williams, Dan Pedersen, John Ireland, Bob McCormick
National Renewable Energy Laboratory
Howard L. Fang
Cummins, Inc.
CLEERS Workshop
Dearborn, Michigan
May , 2008

2. How are DPFs impacted by blending with biodiesel?
Balance point temperature testing – Understand how biodiesel blends impact temperature of soot oxidation on DPF (DECSE method)
Regeneration rate testing – Understand how biodiesel blends may impact rate of filter regeneration (Slope method)
Soot characterization – Understand fundamental differences in biodiesel soot (Raman Spec, SEM-EDX, TGA)

3. How are DPFs impacted by blending with biodiesel?
Cummins ISB 300
2002 Engine, 2004 Certification
Cooled EGR, VGT
Johnson Matthey CCRT
12 Liter DPF
Passively Regenerated System
Pre Catalyst (NO2 Production)
Fuels: ULSD, B100, B20, B5
ReFUEL Test Facility
400 HP Dynamometer
Transient & Steady State Testing
Cummins
Soot Characterization

4. DPF Balance Point Temperature & Regeneration Rate
Regen Rates
DPF Regeneration Rate increases with increasing biodiesel content
Even at 5% blend levels biodiesel PM measurably oxidizes more quickly
Balance Points
BPT – DPF temp where soot load rate is equal to soot regeneration rate
BPT with B20 and B100 is lower than 2007 Cert by 45 ºC and 112 º C
Effect of Biodiesel Blends on DPF Performance:

5. Soot Characterization
Lower combustion temperature for biodiesel soot – (TGA)
Higher disordered carbon content for B100 soot – G/D Carbon Ratio (Raman Spec) G/DULSD = G/DB100 = .586
Higher oxygen content for B100 soot – Carbon/Oxygen Ratio (SEM-EDX)
C/OULSD = C/OB100 = 20.34
N2 Feed
O2 Feed

6. Does Biodiesel’s DPF benefits translate to real-world performance?
Conduct Vehicle Testing on Chassis Dynamometer
Test Vehicle
International Class 8 Truck
2007 Cummins ISX
20 Liter DPF – actively regenerated system
Chassis Dynamometer
Test Range: 8,000–80,000 lb (Class 3-8)
Twin 40” rolls (adjustable wheelbase)
380 hp DC motor
Road Load and Inertia Simulation
380 hp DC Brake
Gearbox
47” Flywheels
40” Rolls
adjustable

7. How does B20 impact DPF load and regeneration during vehicle operation?
Central Business District (CBD)
Filter Loading – Operate under low speed & light load conditions
Cycle Time = 1 hour
Max Speed = 20 mph
Vehicle Inertia = 28,000 lbs
Avg Exhaust Temp = 225 C
DPF Regeneration Opportunity = “Low”
WVU Interstate
Filter Regen – Operate under high speed & high load conditions
Cycle Time = 26 min
Max Speed = 60 mph
Vehicle Inertia = 64,000 lbs
Avg Exhaust Temp = 365 C
DPF Regeneration Opportunity = “High”

8. Soot Load & Regeneration Rate for Cert & B20
CBD Cycle (DPF Load)
WVU Int. Cycle (DPF Regen)
250
200
Cert Diesel
y = 18.67x
150
Filter Loading (grams)
100
B20 Soy
y = 14.95x 50 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Run Time (hours)

9. How are SCRs impacted by blending with biodiesel?
Compare SCR catalyst performance with ULSD and Soy B20
Measure relative importance of catalyst temp, exhaust chemistry and catalyst space velocity
Measure B20’s impact on these system variables and overall NOx conversion
Focus on steady-state modal tests
de-NOx Aftertreatment
JM Zeolite SCR (15.5 Liters)
Urea Injection (air assisted)
NH3 Slip Catalyst
Urea Injection
Diesel Particulate Filter
DOC
Selective Catalytic Reduction
NH3 Slip Cat

10. Critical SCR Performance Variables
8-Mode Test Points
SCR Catalyst Temperature
NO2:NOx Ratio Entering SCR
SCR Catalyst Space Velocity
SCR Catalyst Temperature
NO2:NOx Ratio Entering SCR
SCR Catalyst Space Velocity
SCR Catalyst Temperature
NO2:NOx Ratio Entering SCR
SCR Catalyst Space Velocity
SCR Catalyst Temperature
NO2:NOx Ratio Entering SCR
SCR Catalyst Space Velocity 
(1) 4NH3 + 4NO + O2 → 4N2 + 6H standard
(2) 4NH3 + 2NO + 2NO2 → 4N2 + 6H2O fastest
(3) 8NH3 + 6NO2 → 7N2 + 12H20 slowest

11. Dependence on SCR Temperature
ULSD created higher SCR Temperatures (11º C on average)
No distinct trend between NOx Conversion and SCR Temperature
Mode 3 vs 4 & 7 vs 8 – have very different Conversion % under same temperature conditions

12. Dependence on NO2:NOx Ratio
B20 created higher NO2:NOx ratio (3% on average)
No distinct trend between NOx Conversion and NO2:NOx ratio
Modes 3 & 7 showed highest NOx Conversion even with NO2:NOx well below the optimal 50%

13. Dependence on Space Velocity
Space Velocity nearly identical for two fuels
Distinct linear trend between NOx Conversion and Space Velocity
NOx Conversion drops with decreasing residence time in the catalyst

14. ULSD vs B20 – Overall NOx Conversion
No statistical difference in NOx Conversion with B20
Lower Catalyst Temperature and higher NO2:NOx have negligible impact on overall NOx Conversion

15. Diesel Particulate Filter Selective Catalytic Reduction
Summary
Diesel Particulate Filter
Biodiesel creates lower BPT and Regeneration Rate
Biodiesel soot is more reactive
Benefits also observed in vehicle testing
Fuel economy impacts for active systems still uncertain
Selective Catalytic Reduction
B20 causes lower Catalyst Temperature and higher NO2:NOx
In a space velocity limited system, residence time dominates influence on NOx Conversion
No change in Space Velocity with B20
No change in NOx Conversion with B20

16. Future Research
Long term durability of aftertreatment with biodiesel
Impact of Alkali metals (Na + K) and other impurities (Ca + Mg + P) in biodiesel
5ppm (Na + K) and (Ca + Mg) can lead to significant ash accumulation over aftertreatment full useful life (435k miles for HHD)
Alkali ash can diffuse into Cordierite and SiC substrates, attack protective oxide coatings, neutralize active catalyst sites and change substrate mechanical properties
Fuel quality survey showed 80% of samples below 1ppm detection limit for (Na + K)
Is this low enough?

17. Thank You US Dept of Energy (OVT) Cummins Inc.
National Biodiesel Board
CLEERS Organization