Alternative Fuels asa Diesel EmissionsControl StrategyBy Aleksandar Bugarski, Ph.D.Diesel Aerosols and Gases in UndergroundMetal and Nonmetal Mines,14th U.S. / North American Mine Ventilation SymposiumSalt Lake City, Utah, June 17th, 2012

Diesel Fuels Diesel fuels– Petroleum based– Biodiesel– Synthetic diesel Properties and quality of diesel fuels and lubricants play major rolein efforts of underground mining industry to control emissions fromdiesel powered equipment. Reformulated conventional petroleum diesel and alternative fuelssuch as biodiesel and synthetic diesel can be used to reduceemissions from existing and new design diesel engines.

Regulations Pertinent to Use of Diesel Fuel inUnderground Metal/nonmetal (MNM) Mines in the U.S. 71 Fed. Reg. 28924 [2006]. Mine Safety and Health Administration: 30 CFR57.5060, Diesel particulate matter exposure of underground metal and nonmetalminers. Limit on concentration of diesel particulate matter. Final rule. Code of FederalRegulations, Washington, DC: U.S. Government Printing Office, Office of the FederalRegister.– LSD - 500 ppm sulfur 66 Fed. Reg. 5001 [2001]. Environmental Protection Agency: 40 CFR Parts 69,80, and 86. Clean Diesel Trucks, Buses, and Fuel: Heavy-duty Diesel Engine andVehicle Standards and Highway Diesel Fuel Sulfur Control Requirements. Final Rule.U.S. Code of Federal Regulations, Washington, DC: U.S. Government PrintingOffice, Office of the Federal Register.– ULSD - 15 ppm sulfur 69 Fed. Reg. 38957 [2004]. Environmental Protection Agency: 40 CFR Parts 9,69, 80, 86, 89, 94, 1039, 1048, 1051, 1065, and 1068. Control of Emissions of AirPollution from Nonroad Diesel Engines and Fuel. Final rule. U.S. Code of FederalRegulations, Washington, DC: U.S. Government Printing Office, Office of the FederalRegister.

Petroleum Diesel The quality of the diesel fuels in the U.S. is specified by ASTM International standardASTM D 975PropertyFlash Point, C, min.Water and Sediment, % vol, maxDistillation Temperature, T90 %, % volrecovered,minMaxKinematic Viscosity, mm2/S at 40 CminMaxAsh % mass, maxSulfur, ppm (µg/g)F max% mass, max% mass, maxCopper strip corrosion rating, max(3 h at a minimum control temperatureof 50 C)Cetane number, minOne of the following properties mustbe met:(1) Cetane index, min.(2) Aromaticity, % vol, maxLubricity, HFRR @ 60 C, micron, maxConductivity, pS/m or ConductivityUnits (C.U.), minASTMTestMethodLimits for various gradesNo. 1No. 2No. 2DDDS5000S15S500No. 1DS15No. 1DS500380.05 380.05 380.05 520.05 .288 288 288D 482D 5453D 2622D 129D 1301.32.40.0115 No. 0.05 No. 3D 61340D 976–80D 1319D 6079D 2624/D4308403552025D 93D 2709D 1796D 86No. 2DS5000No. 4D520.05 520.05 55 0.50282338282338282338 0.50No. No. 0.05 No. 0.50No. 35.524.00.10 2.00 404040404030403552025 52025403552025403552025 52025 D 445

Petroleum Diesel Hydrocarbons– Saturated acyclic (aliphatic) hydrocarbons (parafins or alkanes),CnH2n 2;– Unsaturated hydrocarbons with double bonds (olefins andalkenes) or triple bonds (acetylene or alkynes), CnH2n (doublebonds) and CnH2n-2 (triple bonds);– Cyclic (aliphatic) hydrocarbons, either saturated (cycloalkanes ornaphtenes) or unsaturated (cycloalkenes or cycloalkynes), CnHn;– Aromatic hydrocarbons (arenes). Trace elements– Sulfur and sulfur compounds,– Water and sediments,– Ash etc.

Effects of Diesel Fuel Properties on Emissions Sulfur content:– Higher sulfur content results in higher emissions of SO2 and sulfateparticulates;– Minor effects on NOX, CO and HC. Cetane number:– Slight reductions in NOX, CO and HC emissions;– Minor effect on PM emissions. Density:– Fuels with lower density tend to benefit PM emissions;– But those can possibly increase HC emissions. Aromatics– Fuels with lower content of aromatics benefit PM and HC emissions Oxygen content (e.g. biodiesel):– Lower PM emissions;– Increase in HC emissions.6

Identifying contributions from individual properties tothe overall effects presents challenge Changes in some fuel properties generally result in concurrentchanges in other fuel properties, e.g.:– Increase in specific gravity reduces Cetane number.– Specific gravity increases with total aromatic content.– Increase in total aromatic content reduces Cetane number. EPA 2001. Strategies and Issues in Correlating Diesel FuelProperties with Emissions. Staff Discussion Document.EPA420-P-01-001.– Literature review ( 33 studies);– Multi-parameter regression analysis;– Engines built between 1979 and 2002 with different engine designs: Type of injection; Rated speed; Injection control.7

EPA (2001), Results The effects of fuel on emissions in general depend on enginedesign and engine operating conditions.– The engines equipped with EGR exhibit no benefits in NOXemissions from higher Cetane (EPA 2003).– PM emissions from DI engines are more sensitive to fuel changesthan those from IDI engines.– Increase in Cetane number reduced NOX emissions from DI andincreased NOX emissions from IDI engines. The effects of fuel properties on emissions are much smallerthan the differences in emissions from engine to engine.8

Biodiesel Biofuels:– long chain fatty acid methyl esters (FAME) – oxygenatedbiodiesel;– biomass-to-liquid (BTL) – non-oxygenated. Biodiesel fuels are appealing because of:– renewable, nontoxic, and biodegradable nature;– significance to the efforts to reduce dependence on importedpetroleum;– potential to reduce DPM emissions. Most common sources of biomass for FAME:– virgin vegetable oil: Soy, rapeseed (canola), corn, cottonseed, sunflower, palm oil.– animal fats: Beef tallow, pork lard– waste cooking oil.

Regulations Pertinent to Use of Biodiesel inUnderground Mines in the U.S. The neat biodieselfuels must meet thespecifications ofASTM D6751standard. The blends with 6 to20 percent ofbiodiesel must meetASTM D7467standards. The blends belowB5 typically meetsthe ASTM D975diesel fuelspecifications.ASTMTestMethodB100(ASTM D 6751)B6 to B20(ASTM D7467)S15S500S15S500D 9393935252EN 14110D 930.21300.21300.21300.2130D 27090. 1160360360--PropertyFlash Point, C, min.Alcohol Control – One of thefollowing must be metMethanol Content, % vol., maxFlash Point C, minWater and Sediment, % vol., maxDistillation Temperature, T90, C,maxDistillation Temperature, T90, C,maxKinematic Viscosity, mm2/S at 40 CSulfur, ppm (µg/g)Sulfated Ash, mass %Copper Strip Corrosion Rating, maxCetane Number, minD 86--343343D 445D 5453D 874D 130D 6131.9-6.0150.02No. 347Report tocustomer0.051.9-6.05000.02No. 347Report tocustomer0.051.9-4.1151.9-4.1500No. 340Report tocustomer-No. 340Report tocustomer-Cloud Point, ºC,D2500Carbon Residue, % mass, maxRamsbottom Carbon Residue on 10%bottoms, % mass, maxAcid Number, mg KOH/gAsh Content, mass%, maxFree Glycerin, % massTotal Glycerin, % massPhosphorus Content, % massSodium and Potassium, combined,ppmCalcium and Magnesium, combined,ppm (µg/g) maxD4530Cold Soak Filtration, seconds, maxCold Soak Filtration, for use intemperatures below -12 ºC, seconds,maxLubricity, HFRR @ 60 ºC, micron,maxOxidation Stability, hoursBiodiesel Content, %, 10.001EN 145385555EN 145385555Annex toD 6751360360--Annex toD 0

FAME Biodiesel vs. ULSPD PropertiesFuel PropertyTest MethodULSPDFatty Acid Methyl Ester Content [%]ASTM 7371N/AHeat of Combustion [BTU/gal]ASTM D240API Gravity @ 15.6 C [ 84128118126089ASTM D129838.135.834.632.229.8Cetane NumberASTM D6136050505352Sulfur by UV [ppm]ASTM D545311.072.745.066.048.36Cloud Point [ C]ASTM D2500-9-10-8110Pour Point [ C]ASTM D97-24-14-13-21Flash Point, Closed Cup [ C]ASTM D9367687480173ASTM D6079640190170230240Lubricity, HFRR, Wear Scar Diameter[µm] Biodiesel is oxygenated fuel ( 10-11%) Biodiesel has:––––––Lower energy contentLower densitySimilar or lower Cetane numberSulfur content similar to the one of ULSPDNo aromaticsHigher lubricity

Effects of FAME Biodiesel on DPM EmissionsUnderground Experimental Mine Evaluation Experimental work done at NIOSH Mobile Engine Emissions Laboratory (MEEL) at LakeLynn Experimental Mine (LLEM)12

Effects of FAME Fuels and DOC on Average Aerosol MassConcentrations [µg/m3] Biodiesel fuels increased total massconcentrations for M1 (muffler only)and M3, butTotal mass concentrationsdecreased for M2 (muffler and DOC)and M4.400.0Mass Concentration [µg/m 3] 13

Effects of Fuel and DOC on Total Number Concentrations with50dem between 10 and 400 nm Biodiesel fuels increased total numberconcentrations of aerosols for M1 andM3, butTotal number concentrations ofaerosols remained unchanged for M2and decreased slightly for M4.1.50E 06Total Concentrations [#/cm3] 00B10011440006472004835006021007941005741001.00E 065.00E 050.00E 00Mode/Exhaust System14

Effects of FAME Biodiesel on EmissionsEffects of biodiesel fuels on size distribution, number and mass concentrations,and EC concentrations strongly dependent on engine operating mode.Reductions in EC were observed for all engine operating modes and exhaustconfigurations when biodiesel fuels were used.The increase in number and mass concentrations are observed for the light-loadengine operating conditions. Those can be attributed to increase in semi-volatileorganic compounds.The advantage of using DOC are particularly evident in the case of light-loadengine operating conditions.The downside of using the DOC might be increase in NO2 concentrations at highload engine operating conditions.Results are published in: Bugarski, A.D., Cauda E., Janisko, S.J., Hummer, J.A.,Patts, L.D. [2010]. Aerosols Emitted in Underground Mine Air by Diesel EngineFueled with Biodiesel. Journal of Air and Waste Management Association. 60, 237244.

Effects of FAME Biodiesel on DPM EmissionsUnderground Production Mine Evaluation The evaluation was conducted in an active underground mine using a production vehicleusing isolated zone methodology. The vehicle/engine was operated for extended period of time in the 600 feet long sectionof main drift of the isolated zone. The vehicle/engine duty cycle consisted of several repetitions of a 300-second longsimulated haulage-truck duty cycle.16

Effects of FAME Fuels on Average EC, OC, and TCConcentrations [µg/m3] Emitted by the Haulage Truck Poweredby Tier 3 Engine Biodiesel fuels reduced EC, OC, and TC concentrations of aerosols inmine air. The reductions in EC and TC (dominated by EC) concentrations weredirectly related to biodiesel content in the blends.17

Effects of FAME Fuels on Number Size Distributions In general, the sizedistributions of aerosolsobserved for thebiodiesel blends werefound to becharacterized bysmaller mediandiameter (D50) andlower peakconcentrations than thecorresponding sizedistributions observedfor the ULSD.18

Biodiesel in Underground Mining Relatively simple to implement.– B5 to B20 - quite strait forward– B20 to B100 – number of uncertainties The major issues preventing a wider use of biodiesel in the U.S.underground mines:– availability;– quality;– low-temperature operability;– engine compatibility;– compatibility with exhaust aftertreatment technologies;– cost;– safety.

Low Temperature Operability At cold temperatures FAME fuels crystallize, clog the fuel filters andeventually gel so they cannot be pumped from the fuel tank to theengine. The cold flow properties of FAME fuels depend strongly onfeedstock: e.g. soy methyl ester has cloud point of 0 ºC (32 ºF) andedible tallow methyl ester has cloud point of 19 ºC (66 ºF) [NREL2009]. Since FAME fuel gels at temperatures 11 ºC to 17 ºC (20 ºF to 30ºF) higher than petroleum diesel, the handling of neat and blendedFAME fuels during cold temperatures is a major issue.

Low Temperature Operability The critical properties for identifying the low-temperature operabilityof FAME fuels are cloud point, pour point, cold filter plugging pointand low-temperature flow test. Cloud point is the most widely usedand provides the most conservative estimate of the cold weatheroperability. The typical diesel cold flow additives have a limited effectiveness onB100, but work with varying degrees of effectiveness with B20[NREL 2009]. Storing biodiesel in the underground or heated fuel tanks can helpmitigate issues with operability during periods of cold weather

Engine Compatibility Engine manufacturers approve use of biodiesel blends with up to 5and 20% biodiesel– cold flow properties;– material compatibility;– maintenance intervals;– fuel stability;– biological growth;– energy content;– emissions;– overall handling Warranty issues.

Compatibility with Exhaust AftertreatmentTechnologies Theoretically, biodiesel fuels that are found to reduce total PMemissions, increase NOX emissions, and produce DPM with highersoluble organic fraction should have positive effect on performanceof DPF systems. Due to reductions in DPM emissions and slight increase in NOXemissions, the NOX/DPM ratio in the exhaust of an engine fueled bybiodiesel should be higher than the same engine fueled withpetroleum diesel. Higher NOX/DPM ratio is desirable for the DPFsystems that are designed to regenerate passively by NO2 oxidation. B20 and neat SME biodiesel were shown to lower balance pointtemperature of catalyzed diesel particulate filter by 45 ºC and 112ºC, respectively [Williams et al. 2006].

Compatibility with Exhaust AftertreatmentTechnologies Increase in levels of SME and RME biodiesel in the fuel results inincrease in the rate of DPF regeneration at any given engineoperating conditions [Williams et al. 2006, Fukuda et al. 2008]. The fuels with high content of biodiesel were found to hinderregeneration of the CRT and CCRT systems that are regeneratedwith help of after- and post-injection of fuel [Fukuda et al. 2008].Lower heating value of biodiesel and changes in fuel injectioncharacteristics are potential culprits.

Synthetic Diesel Fuels The following fuels fall in this category:– gas-to-liquid (GTL),– coal-to-liquid (CTL), and– biomass-to-liquid (BTL) fuels. The most widely used process to produce synthetic fuels is the onepatented by Fischer and Tropsch in 1930. Synthetic diesel– near-zero sulfur content,– near 100% paraffinic, near-zero aromatic content, and– high Cetane number, typically in excess of 70

Effects of Synthetic Diesel Fuels on Emissions Substantial reductions in regulated emissions when neat GTL fuelsare used in place of petroleum based diesel fuels even inunmodified engines [Schaberg et al. 1997, Norton et al. 1998, Maly2004, Alleman et al. 2005, CEC 2006, Maly et al. 2007, Li and Zhen2009]:– PM between 22 and 35%,– NOX between 7 and 35%,– HC between 5 and 46%, and– CO between 11 and 38%. Decrease number concentrations of nucleation mode particles indiesel engine exhaust is observed when GTL fuel is used [Li andZen 2009].

Effects of Synthetic Diesel Fuels on EnginePerformance Synthetic diesel fuels have poor lubricity and cold weather flowproperties when compared with petroleum diesel fuel:– Lubricity additives are used to prevent fuel-injection systemwear.– Additives and/or appropriate handling practices need to befollowed to prevent gelling in cold environments. Synthetic diesel fuels do not require– modifications on the engine;– new or modified pipelines, storage tanks, or pumps. Fuel consumption might go up 3-5%.

Other Issues with Using Alternative Diesel Fuels Blending: The cost effectiveness diminishes for both biodiesel andsynthetic diesel fuels when percentage of blended alternative fuelexceed approximately 50. Optimization: The effects of alternative fuels on the emissions couldbe further reduced through optimization of engine design to accountfor differences in fuel properties. Compatibility with engine components:– Engines with high pressure fuel injection systems are moresensitive to fuel quality issues– High levels of biodiesel present in the engine oil may result inpolymerization and cause serious engine oil sludge problems.Therefore, when high blends of biodiesel are used, the engine oilchange intervals should be significantly shortened.

Other Issues with Using Alternative Diesel Fuels Compatibility with aftertreatment: The reformulated fuels might aideor diminish performance of exhaust aftertreatment technologies:– different composition of DPM;– different exhaust temperatures.

Fuel Additives Fuel additives are added to diesel fuel for a wide variety ofpurposes:– Improvement in the fuel delivery system performance (injectorcleaners, lubricity additives);– Improvement in the combustion process (cetane numberimprovers, smoke suppressants);– Fuel handling (antifoam, de-icing, low-temperature operabilityadditives);– Fuel stability (antioxidants, stabilizers, metal deactivators,dispersant);– Contaminant control (biocides, deemulsifiers, corrosioninhibitors)– Emissions control (oxygenated compounds, biodiesel,diesel/water emulsions)– Enhancing the regeneration of DPF systems.

Fuel Additives Multifunctional packages added at the refinery or at the terminal;– Organosilicone compounds - to suppress foaming;– Alcohols/glycols - to prevent turning free water in diesel fuel inice crystals;– Various polymers - to improve cold flow properties of diesel fuel– Mono acids, amides, and esters - to improve lubricity ofhydrotreated diesel fuels;– Alkyl nitrates, nitrates, peroxides - to improve cetane number;– Ashless polymeric detergents - to clean fuel injector deposits;– Hindered phenols and certain amines - to suppress oxidation ofdiesel fuel;– Alcohols, glycol ethers and esters, and methyl esters (biodiesel)to reduce diesel emissions. With some exception, the concentration of these additives in thediesel fuel is typically low, on the order of a couple ppm to a coupleppt.

Fuel Additives Aftermarket additives:– Water/diesel emulsions;– Fuel borne catalyst (FBC): bulk fuel supply dedicated to the vehicles equipped with DPFs; via onboard dosing systems.– Biodiesel.

Regulations Pertinent to Use of Fuel Additives in theU.S. Underground Mines Only fuel additives registered with the EPA are able to be usedin underground mines in the U.S. [66 Fed. Reg. 27864 (2001),71 Fed. Reg. 28924 (2006)]. 66 Fed. Reg. 5001 [2001] and 69 Fed. Reg. 38957 [2004]require registration of additives with EPA . The manufacturersneed to prove, through a three-tier process, that the fueladditives are safe and do not change or create new/harmfulemission species.– survey existing scientific information on each product, andanalyze the combustion and evaporative emissionsgenerated by fuels and additives (Tier 1),– conduct testing to determine the potential adverse effectsof inhalation of fuels and fuel additive emissions (Tier 2),and if adequate information is not available,– conduct additional testing focusing on areas of concern(Tier 3).

The FBC Additives Containing Transition Metals The FBC additives containing transitional metals are of majorconcern The use of small concentrations of FBC in engines equipped withDPF systems has not been shown to substantially increase therisk associated with exposure to aerosols and gases emitted bydiesel-powered equipment. In the case of DPF equipped engines, the concentrations ofmetals, from FBC dosing, emitted into the environment have beenshown to be minimal. Metallic materials in these additives will add to the amount of ashcaptured in the DPF and thus, even at low dosages, shorten theash removal servicing intervals.

The FBC Additives Containing Transition Metals It is absolutely critical that FBC-treated fuels not be used in enginesnot fitted with DPF systems. This precaution should also be taken toprevent the use of FBC-treated fuels in engines equipped withcompromised DPF systems. A potential engineering solution, for this problem, would involve thedeployment of onboard dosing systems, with closed feedback loops,monitoring the exhaust backpressure and shutting off the dosingsystem in the case of a DPF failure [Lemaire 1999, Seguelong andQuigley 2002, D’Urbano and Mayer 2007].

Lubricating Oil The performance of contemporary diesel engines and advancedexhaust aftertreatment systems is highly sensitive to properties andquality of lubricants. Improvements in quality of diesel fuels and lubricants brought byEPA regulations [66 Fed. Reg. 5001 (2001), 69 Fed. Reg. 38957(2004)], particularly reduction in sulfur content to less than 15 ppm,and introduction of low-ash lubricating oil (API CJ4), playedimportant role in enabling development and implementation ofcatalyzed DPF technology across wide spectrum of applications. Removal of sulfur from the fuel and lubricating oil minimized sulfateproduction and poisoning of the catalyst. Minimizing ash content in lubricating oil helps minimizing ashaccumulation and extending periods between DPF cleaning.

Thank you for yourattention!Aleksandar Bugarskiabugarski @cdc.gov412.386.5912The findings and conclusion of this publication have not been formally disseminated by theNational Institute for Occupational Safety and Health and should not be constituted to representany agency determination or policy.Mention of any company or product does not constitute endorsement by NIOSH.

ASTM D6751 standard. The blends with 6 to 20 percent of biodiesel must meet ASTM D7467 standards. The blends below B5 typically meets the ASTM D975 diesel fuel specifications. ASTM Test B100 B6 to B20 Property Method (ASTM D 6751) (ASTM D7467) S15 S500 S15 S500 Flash Point, C, min. D 93 93 93 52 52 Alcohol Control - One of the