Biodiesel Quality and Impact on Emission Control Systems Bob McCormick National Renewable Energy Laboratory Golden, Colorado September 6, 2006 What is biodiesel? Mono-alkyl esters of fatty acids (i.e. methyl or ethyl esters) O O O OCH 3 OCH 3 OCH 3 Methyl Oleate Methyl Linoleate Methyl Linolenate 100 lb triglyceride + 10 lb alcohol = 10 lb glycerine (byproduct) + 100 lb Mono-alkyl ester soy oil methanol Biodiesel Must meet the quality requirements of ASTM D6751 Typically used as blend with petrodiesel (up to 20%) $1/gal tax credit for agri-biodiesel (vegetable oil/animal fat), $0.5/gal for waste cooking oil initiated in January 2005 1
Biodiesel Production 80,000,000 70,000,000 60,000,000 Gallons per Year 50,000,000 40,000,000 30,000,000 20,000,000 10,000,000 0 1999 2000 2001 2002 2003 2004 2005 NBB predicting over 250 million gallons for 2006 Current production capacity is more than 400 million annual gallons More than 570 million annual gallons under construction or planned Biodiesel Production Process Crude Products Methanol for Purification and Recycle Fat or Vegetable Oil Excess Methanol Catalyst (caustic soda, NaOH) 8 Crude Biodiesel for Purification Crude Glycerol for Sale or Purification 2
Potential Impurities in Biodiesel Methanol Degrades some plastics and elastomers, corrosive Can lower flashpoint to unsafe levels (fire safety) Unconverted/partly converted fat (bound glycerin) Results in very poor cold flow properties, injector and incylinder deposits, potential engine failure Glycerin (free glycerin) Results in injector deposits, clogged fuel filters, deposit at bottom of fuel storage tank Catalyst/Adsorbents/Contaminants Excessive injector, fuel pump, piston, and ring wear, filter plugging, issues with lubricant, emission control catalyst ASTM D6751-06e Limits Impurities Flashpoint 130ºC minimum Limits methanol to very low level Total glycerin is limited to 0.24 wt% maximum Free glycerin is limited to 0.02wt% maximum Sodium + Potassium (from manufacturing catalyst) limited to 5 ppm max and sulfated ash is limited to 0.020 wt% Magnesium + Calcium (from adsorbents and hard water) limited to 5 ppm max (recently passed) Phosphorus (from phospholipids in vegetable oil) limited to 10 ppm max It is critical to insure that all B100 meets D6751 limits 3
Biodiesel Degradation Biodiesel can degrade in storage: Oxidation Increases acidity (limited in D6751-06e to 0.5) Forms gums A stability requirement is being added to D6751 Microbial contamination Biodiesel is biodegradable Microbes form films or mats that can plug filters Requires water in storage tank Storage tank housekeeping issue/biocide treatment Also an issue for petroleum fuels Can B100 Stability Ensure B20 Stability? 250 B20 D2274M Total Insoluble, mg/100 ml 200 150 100 50 25 20 15 10 5 0 0 1 2 3 4 5 6 7 8 Yes, B100 stability appears to be an excellent predictor of blend stability, 3 hour Rancimat ensures low deposits and 6 hr Rancimat in the blend 0 0 2 4 6 8 10 B100 Rancimat IP, hr Similar data available for 5% biodiesel blends Blend stability is dominated by B100 stability A 3 hr Rancimat IP for B100 appears to be adequate to ensure stability of both B5 and B20 blends passed at ASTM Subcommittee E in June 2006 4
ASTM Specification For Blends Engine manufacturer s top priority Preventing engine manufacturer s from offering warranty coverage thus a significant market barrier Do not exist today Critical for protection of engines from poor quality fuel Addition of up to 5% biodiesel into D975 (diesel fuel spec) Stand alone specification for B20, ultimately for blends from 6 to 20% A necessary requirement is an oxidation stability specification for B100 now being included 2007 OEM Project Project Goal: Investigate the impact of B20 and lower on 2007 and later fuel system, engine, and emission control technology Primary focus on ECS performance and durability in multiple platforms Fuel Injection Equipment Impacts Fleet Evaluation Significant funding from NBB, DOE and in-kind resources from stakeholder industries Including MECA 5
Biodiesel Testing with DPF MD Engine 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, B100, B20, B5 ReFUEL Test Facility Aaron Williams leading this effort for NREL 400 HP Dynamometer Transient & Steady State Testing Cummins Soot Characterization Heavy Duty Transient (HDT) Test Results Installation of DPF (base fuel): 97% CO, 99% THC, 99% PM, +1% BSFC B20 results in 24% PM reduction w/o DPF, 27% reduction w/ DPF 6
BPT and Regeneration Rate Test Procedures Balance Point Temperature (BPT) DPF temperature where rate of PM collection equals rate of PM oxidation BPT is determined by monitoring DPF back pressure Regeneration Rate Test simulates active regeneration strategy BPT/Regeneration Rate Results BPT ULSD 360ºC B20 320ºC B100 250ºC BPT is 40ºC lower for B20 Soot is more easily burned off of filter B20 can be used for lower temperature duty cycle Regeneration rate increases with increasing biodiesel content Even at 5%, biodiesel PM measurably oxidizes more quickly 7
Availability of NO x for Soot Regeneration Catalyzed DPF s use NO 2 to oxidize soot There is no evidence to higher availability of NOx from biodiesel fuels Regeneration Rate Test ULSD = 2.01 g/bhp-hr B5 = 1.97 g/bhp-hr B20 = 2.15 g/bhp-hr No statistical difference (at alpha = 0.05) Balance Point Temp Test B100 BPT B20 BPT Biodiesel DPF Summary B20 vs. ULSD Transient test results Both fuels < 0.01 g/bhp-hr PM with CCRT installed PM reduction from B20 vs. ULSD still measurable with CCRT installed BPT decreased by 45 ºC with B20 and 112 ºC with B100 Significant differences in regeneration rate with blend levels as low as 5% Soot Characterization TGA confirms higher reactivity of biodiesel soot Higher oxygen content for biodiesel soot Higher ratio of disordered carbon for biodiesel soot Results to be reported in October SAE 2006-01-3280 Phase II Test Plan 2007 compliant engine Heat exchanger to control exhaust temperature Quantify fuel penalty associated with active systems Adding raw exhaust NO/NO x measuring capability 8
Light Duty Project Leverages significant development work under APBF-DEC activity Conducted via subcontract with FEV Engine Technologies Builds on existing strategies Modern hardware Matt Thornton leading effort for NREL Mercedes C200 CDI MB OM646 Engines Scope of Work Task 1: System Commissioning and Baseline Testing Task 2: System optimization for NO x adsorber/dpf B5 and B20 Task 3: System optimization for SCR/DPF B5 and B20 Task 4: Durability testing of NO x adsorber/dpf 700 hour test with periodic evaluations using B20 Task 5: Durability testing of SCR/DPF 700 hour test with periodic evaluations using B20 Task 6: Engine and FIE system inspections 9
Protocols System Optimizations: Lean/rich modulation (for NAC) Catalyst mapping Desulfurization (for NAC) Rapid warm-up Performance Evaluations: Cold and hot UDDS US06 HFET Engine dyno testing at FEV Chassis dyno testing at EPA Ann Arbor Accelerated aging to represent 2100 hours of operation (approximately 120,00 miles or full useful life) for B20 Technical Progress Task 1: System Commissioning and Baseline Testing - Completed Task 2: System optimization for NO x adsorber/dpf - Ongoing Calibration for low engine-out NO x Defined system architecture Task 3: System optimization for SCR/DPF Ongoing Calibration for more optimal engine-out NO x Working to define system architecture CFD modeling of urea injection and decomposition 10
NO x Emissions Calibration NOx emissions comparison at 14 calibration modes 800 700 Base calibration Optimized calibration 600 500 NOx [ppm] 400 300 200 100 0 650 0.00 1000 1.80 1200 3.02 1425 1.61 1615 3.07 1750 6.30 2000 4.00 2060 6.40 2300 4.05 2050 1.46 2250 8.16 2650 6.69 1450 4.59 1750 4.59 Engine speed [rpm] / BMEP [bar] Emission Control Layout and Specifications: NAC/DPF 11
Modeling SCR Components to Finalize Design CFD model of SCR system Focus on urea mixing and decomposition Spray Model: Urea Injection Urea decomposition modeled w/ CHEMKIN: Urea (23 H 2 O) NH 3 + HNCO + 23 H 2 O HNCO + H 2 O NH 3 + CO 2 Catalyst modeled w/ global reaction chemistry 4 NH 3 + 4 NO + O 2 4 N 2 + 6 H 2 O 4 NH 3 + 2 NO + 2 NO 2 4 N 2 + 6 H 2 O 4 NH 3 + 3 O 2 2 N 2 + 6 H 2 O SCR Possible Geometries (Catalyst Locations) Geometries & Meshes 12
Closing Remarks Biodiesel production in the US is increasing rapidly, will approach 1 billion annual gallon in 2 to 3 years ASTM D6751 limits the impurities in biodiesel Intended to protect ECS Not yet validated experimentally or in the field Testing with DPF indicates increased reactivity of PM for biodiesel blends Lower BPT Potential advantages need to be verified Ongoing LD project is examining biodiesel blends with: NAC/DPF SCR/DPF Future projects with NO x control on MD and HD engines, including off-highway http://www.nrel.gov/vehiclesandfuels/npbf/pubs_biodiesel.html 13