Affect of Biodiesel Blends on DPF and SCR

Affect of Biodiesel Blends on DPF and SCR Systems Aaron Williams, Dan Pedersen, John Ireland, Bob Mc. Cormick 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 (NO 2 Production) § Fuels: ULSD, B 100, B 20, B 5 § Re. FUEL Test Facility § 400 HP Dynamometer § Transient & Steady State Testing § Cummins § Soot Characterization

DPF Balance Point Temperature & Regeneration Rate § DPF Regeneration Rate increases with increasing biodiesel content § Even at 5% blend levels biodiesel PM measurably oxidizes more quickly Regen Rates Balance Points § BPT – DPF temp where soot load rate is equal to soot regeneration rate § BPT with B 20 and B 100 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 B 100 soot – G/D Carbon Ratio (Raman Spec) G/DULSD =. 836 G/DB 100 =. 586 § Higher oxygen content for B 100 soot – Carbon/Oxygen Ratio (SEM-EDX) C/OULSD = 25. 34 C/OB 100 = 20. 34 N 2 Feed O 2 Feed www. pecj. or. jp/english/jcap/images/jcap 18_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) 40” Rolls § Twin 40” rolls (adjustable wheelbase) § 380 hp DC motor § Road Load and Inertia Simulation Gearbox 380 hp DC Brake adjustable 47” Flywheels

How does B 20 impact DPF load and regeneration during vehicle operation? Central Business District (CBD) Filter Loading – Operate under low speed & light load conditions § § § WVU Interstate Cycle Time = 1 hour Max Speed = 20 mph Vehicle Inertia = 28, 000 lbs Avg Exhaust Temp = 225 C DPF Regeneration Opportunity = “Low” 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 & B 20 CBD Cycle (DPF Load) Filter Loading (grams) 250 WVU Int. Cycle (DPF Regen) 200 Cert Diesel y = 18. 67 x 150 100 B 20 Soy y = 14. 95 x 50 0 0 1 2 3 4 5 6 7 8 9 10 Run Time (hours) 11 12 13 14 15

How are SCRs impacted by blending with biodiesel? § Compare SCR catalyst performance with ULSD and Soy B 20 § Measure relative importance of catalyst temp, exhaust chemistry and catalyst space velocity § Measure B 20’s impact on these system variables and overall NOx conversion § Focus on steady-state modal tests Urea Injection DOC Diesel Particulate Filter de-NOx Aftertreatment § § § JM Zeolite SCR (15. 5 Liters) Urea Injection (air assisted) NH 3 Slip Catalyst Selective Catalytic Reduction NH 3 Slip Cat

Critical SCR Performance Variables 8 -Mode Test Points 1. SCR Catalyst. Temperature 2. NO 2: NOx Ratio. Entering. SCR 3. SCR Catalyst Space. Velocity http: //www. dieselnet. com/tech/cat_scr. html (1) 4 NH 3 + 4 NO + O 2 → 4 N 2 + 6 H 20 standard (2) 4 NH 3 + 2 NO 2 → 4 N 2 + 6 H 2 O fastest (3) 8 NH 3 + 6 NO 2 → 7 N 2 + 12 H 20 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 NO 2: NOx Ratio § B 20 created higher NO 2: NOx ratio (3% on average) § No distinct trend between NOx Conversion and NO 2: NOx ratio § Modes 3 & 7 showed highest NOx Conversion even with NO 2: 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 B 20 – Overall NOx Conversion § No statistical difference in NOx Conversion with B 20 § Lower Catalyst Temperature and higher NO 2: NOx have negligible impact on overall NOx Conversion

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 § B 20 causes lower Catalyst Temperature and higher NO 2: NOx § In a space velocity limited system, residence time dominates influence on NOx Conversion § No change in Space Velocity with B 20 § No change in NOx Conversion with B 20

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

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