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 13 - 15, 2008

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)

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

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: http://www.nrel.gov/vehiclesandfuels/npbf/pdfs/40015.pdf

Soot Characterization Lower combustion temperature for biodiesel soot – (TGA) Higher disordered carbon content for B100 soot – G/D Carbon Ratio (Raman Spec) G/DULSD = .836 G/DB100 = .586 Higher oxygen content for B100 soot – Carbon/Oxygen Ratio (SEM-EDX) C/OULSD = 25.34 C/OB100 = 20.34 N2 Feed O2 Feed www.pecj.or.jp/english/jcap/images/jcap18_01.gif

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

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”

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)

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

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 http://www.dieselnet.com/tech/cat_scr.html  (1) 4NH3 + 4NO + O2 → 4N2 + 6H20 standard (2) 4NH3 + 2NO + 2NO2 → 4N2 + 6H2O fastest (3) 8NH3 + 6NO2 → 7N2 + 12H20 slowest

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

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%

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

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

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

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?

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