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Affect of Biodiesel Blends on DPF and SCR Systems

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?.

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Affect of Biodiesel Blends on DPF and SCR Systems

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  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 13 - 15, 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: http://www.nrel.gov/vehiclesandfuels/npbf/pdfs/40015.pdf

  5. N2 Feed O2 Feed 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 www.pecj.or.jp/english/jcap/images/jcap18_01.gif

  6. 380 hp DC Brake 40” Rolls Gearbox Gearbox adjustable 47” Flywheels 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

  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. Cert Diesel y = 18.67x B20 Soy y = 14.95x Soot Load & Regeneration Rate for Cert & B20 CBD Cycle (DPF Load) WVU Int. Cycle (DPF Regen) 250 200 150 Filter Loading (grams) 100 50 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Run Time (hours)

  9. Urea Injection DOC Diesel Particulate Filter Selective Catalytic Reduction NH3 Slip Cat 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

  10. http://www.dieselnet.com/tech/cat_scr.html 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 + 6H20 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. 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

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