Biodiesel or biodiesel blends described in this chapter (up to B5 in ASTM D975 and B6 to B20 covered by ASTM D7467) are used in the same equipment as conventional diesel fuels, often without modification or restrictions. Therefore, the same general fuel characteristics and considerations for engines and equipment with conventional diesel fuels also applies to the use of biodiesel and biodiesel blends. The reader is referenced to those sections in this manual for more information and this will not be repeated here. We will instead focus the next information on the considerations that vary from those of conventional petrodiesel.
Sulfated Ash
Ash-forming materials may be present in biodiesel in three forms: (1) abrasive solids, (2) soluble metallic soaps, and (3) unremoved catalysts. Abrasive solids and unremoved cata- lysts can contribute to injector, fuel pump, piston and ring wear, and engine deposits. Soluble metallic soaps have little effect on wear but may contribute to filter plugging and engine deposits. The ash-forming materials may also contrib- ute to exhaust catalyst plugging and additional deposition in diesel particulate filters (sometimes referred to as particu- late traps).
Sulfur
B100 is essentially sulfur free, although some animal fat–based biodiesel has been found with up to 100 ppm sulfur (a result of hides and hair from the animal fat–rendering process) and some yellow grease–based biodiesel has been found with similar levels (a result of frying foods high in sulfur like onion rings).
Test Method ASTM D5453 should be used with biodiesel. Use of other test methods may provide falsely high results when analyz- ing B100 with extremely low sulfur levels (less than 5 ppm). Bio- diesel sulfur analysis from RR: D02-1480, Biodiesel Fuel Cetane Number Testing Program, January–April, 1999, using Test Method D2622 yielded falsely high results due to the presence of the oxygen in the biodiesel. Sulfur results using Test Method D2622 were more accurate with B20 than with B100 due to the lower oxygen content of B20. Potential future improvements to Test Method D2622 may provide more accurate values.
Cetane Number
Cetane number is a measure of the ignition quality of the fuel and influences startability, white smoke, and combus- tion roughness. The cetane number requirements depend on engine design, size, nature of speed and load variations, and starting and atmospheric conditions. The calculated cetane index, Test Method D976 or D4737, may not be used to approximate the cetane number with biodiesel or its blends as it will result in falsely low values. There is, as yet, no sub- stantiating data to support the calculation of cetane index with biodiesel or biodiesel blends.
Carbon Residue
Carbon residue gives a measure of the carbon depositing ten- dencies of a fuel. While not directly correlating with engine deposits, this property is considered an approximation.
Although biodiesel is in the petroleum diesel boiling range, most biodiesels boil at approximately the same temperature and it is difficult to leave a 10 % residual upon distillation. Thus, a 100 % sample is used to replace the 10 % residual sample.
TABLE 4—Detailed Requirements for B6 to B20 Biodiesel Blends
Property Test Method Grade
B6 to B20 S15 B6 to B20 S500A B6 to B20 S5000B
Acid umber, mg KOH/g, max D664 0.3 0.3 0.3
Viscosity, mm2/s at 40C D445 1.9–4.1C 1.9–4.1C 1.9–4.1C
Flash point,C, min D93 52D 52D 52D
Cloud point,C, max or LTFT/CFPP,C, max D2500, D4539, D6371 E E E
Sulfur content (mg/g) D5453 15 . . . . . .
mass percent, max D2622 . . . 0.05 . . .
mass percent, max D129 . . . . . . 0.50
Distillation temperature,C, 90 % vol recovered, max
D86 343 343 343
Ramsbottom carbon residue on 10 % bottoms, mass percent, max
D524 0.35 0.35 0.35
Cetane number, min D613F 40G 40G 40G
One of the following must be met:
(1) Cetane index, min.
D976-80H 40 40 40
(2) Aromaticity, % vol, max D1319-03H 35 35 . . .
Ash content, mass percent, max D482 0.01 0.01 0.01
Water and sediment, volume percent, max D2709 0.05 0.05 0.05
Copper corrosion, 3 h at 50C, max D130 No. 3 No. 3 No. 3
Biodiesel content, % (V/V) D7371 6. - 20. 6. - 20. 6. - 20.
Oxidation stability, hours, min EN 14112 6 6 6
Lubricity, HFRR at 60C, micron (mm), max D6079 520I 520I 520I
AUnder United States of America regulations, if Grades B6-20 S500 are sold for tax exempt purposes then, at, or beyond terminal storage tanks, they are required by 26 CFR Part 48 to contain the dye Solvent Red 164 at a concentration spectrally equivalent to 3.9 lb per thousand barrels of the solid dye standard Solvent Red 164, or the tax must be collected.
BUnder United States of America regulations, Grades B6-20 S5000 are required by 40 CFR part 80 to contain a sufficient amount of the dye Solvent Red 164 so its presence is visually apparent. At or beyond terminal storage tanks, they are required by 26 CFR Part 48 to contain the dye Solvent Red 164 at a concentration spectrally equivalent to 3.9 lb per thousand barrels of the solid dye standard Solvent Red 26.
CIf Grade No. 1-D or blends of Grade No. 1-D and Grade No. 2-D diesel fuel are used, the minimum viscosity shall be 1.3 mm2/s.
DIf Grade No. 1-D or blends of Grade No. 1-D and Grade No. 2-D diesel fuel are used, or a cloud point of less than –12C is specified, the minimum flash point shall be 38C.
EIt is unrealistic to specify low temperature properties that will ensure satisfactory operation at all ambient conditions. In general, cloud point (or wax appearance point) Low Temperature Flow Test, and Cold Filter Plugging Point Test may be useful to estimate vehicle low temperature operability limits but their use with B6 to B20 has not been validated. However, satisfactory operation below the cloud point (or wax appearance point) may be achieved depending on equipment design, operating conditions, and the use of flow-improver additives as described in X3.1.2. Appropriate low temperature operability properties should be agreed upon between the fuel supplier and purchaser for the intended use and expected ambient temperatures. Test Methods D4539 and D6371 may be especially useful to estimate vehicle low temperature operability limits when flow improvers are used but their use with B6 to B20 from a full range of biodiesel feedstock sources has not been validated. Due to fuel delivery system, engine design, and test method dif- ferences, low temperature operability tests may not provide the same degree of protection in various vehicle operating classes. Tenth percentile mini- mum air temperatures for U.S. locations are provided in Appendix X3 as a means of estimating expected regional temperatures. The tenth percentile minimum air temperatures may be used to estimate expected regional target temperatures for use with Test Methods D2500, D4539, and D6371. Refer to X3.1.3 for further general guidance on test application.
FCalculated cetane index approximation, Test Method D4737, is not applicable to biodiesel blends.
GLow ambient temperatures, as well as engine operation at high altitudes, may require the use of fuels with higher cetane ratings. If the diesel fuel is qualified under Table 1 of Specification D975 for cetane, it is not necessary to measure the cetane number of the blend. This is because the cetane num- ber of the individual blend components will be at least 40, so the resulting blend will also be at least 40 cetane number.
HThese test methods are specified in 40 CFR Part 80.
IIf the diesel fuel is qualified under Table 1 of Specification D975 for lubricity, it is not necessary to measure the lubricity of the blend. This is because the lubricity of the individual blend components will be less than 520 micron (mm) so the resulting blend will also be less than 520 (mm).
Acid Number
The acid number is used to determine the level of free fatty acids or processing acids that may be present in biodiesel. Biodiesel with a high acid number has been shown to increase fueling sys- tem deposits and may increase the likelihood for corrosion.
The acid number measures a different phenomenon for biodiesel than petroleum based diesel fuel. The acid number for biodiesel measures free fatty acids or degradation by- products not found in petroleum-based diesel fuel. Increased fuel temperatures in some new fuel designs due to fuel recy- cling from common rail injector systems, may accelerate fuel degradation, which could result in high acid values and increased filter plugging potential.
Free Glycerin
The free glycerin method is used to determine the level of glycerin in the fuel. High levels of free glycerin can cause injector deposits, as well as clogged fueling systems, and result in a build up of free glycerin in the bottom of storage tanks and fueling systems.
Total Glycerin
The total glycerin method is used to determine the level of glyc- erin in the fuel and includes the free glycerin and the glycerin por- tion of any unreacted or partially reacted oil or fat. Low levels of total glycerin ensure that high conversion of the oil or fat into its mono-alkyl esters has taken place. High levels of monoglycerides, diglycerides, and triglycerides can cause injector deposits and may adversely affect cold weather operation and filter plugging.
Phosphorus Content
Phosphorus, a natural element in all plants that is also found in vegetable oils, can affect the conversion rates in diesel exhaust catalytic converters used to control emissions. Accord- ingly, the phosphorous level should be kept low. Catalytic con- verters are increasingly being used globally on diesel-powered equipment as emissions standards are tightened. Biodiesel pro- duced from U.S. sources has been shown to have low phos- phorus content (below 1 ppm) and the specification value of 10 ppm maximum is not problematic. Biodiesel from other sources may or may not contain higher levels of phosphorus, and this specification was added to ensure that all biodiesel, regardless of the source, has low phosphorus content.
Reduced Pressure Distillation
Biodiesel exhibits a series of close boiling points rather than a distillation curve. The fatty acids chains in the raw oils and fats from which biodiesel is produced are mainly comprised of straight chain hydrocarbons with 16 to 18 carbons that have similar boiling temperatures. The atmospheric boiling point of biodiesel generally ranges from 330 to 357C, thus the specifi- cation value of 360C is not problematic. This specification was incorporated as an added precaution to ensure the fuel has not been adulterated with high boiling contaminants.
Density
The density of biodiesel meeting the specifications in Table 1 (Table 1 in D396 and D975) falls between 0.86 and 0.90, with typi- cal values falling between 0.88 and 0.89. Because biodiesel density falls between 0.86 and 0.90, a separate specification is not needed.
The density of raw oils and fats can be similar to biodiesel and the use of density as an expedient check of fuel quality may not be as useful for biodiesel as it is for petroleum-based diesel fuel.
Lubricity
In certain fuel injection equipment in compression ignition engines, such as rotary/distributor fuel pumps and injectors, the fuel functions as a lubricant. Blending biodiesel fuel with petroleum-based compression-ignition fuel typically improves fuel lubricity. No specification is needed for biodiesel lubric- ity as values are lower than a 300 m Wear Scar Diameter (WSD) using HFRR with B100.
Alcohol Control
Alcohol control is to limit the level of unreacted alcohol remaining in the finished fuel. This can be measured directly by the volume percent alcohol or indirectly through a high flash point value.
The flash point specification, when used for alcohol con- trol for biodiesel, is intended to be 100C minimum, which has been correlated to 0.2 volume percent alcohol. Typical values are over 160C. Due to high variability with Test Method D93 as the flash point approaches 100C, the flash point specification has been set at 130C minimum to ensure an actual value of 100C minimum. Improvements and alternatives to Test Method D93 are being investigated.
Once complete, the specification of 100C minimum may be reevaluated for alcohol control.
Calcium and Magnesium
Calcium and magnesium may be present in biodiesel as abrasive solids or soluble metallic soaps. Abrasive solids can contribute to injector, fuel pump, piston, and ring wear, as well as to engine deposits. Soluble metallic soaps have little effect on wear, but they may contribute to filter plugging and engine deposits. High levels of calcium and magnesium compounds may also collect in the exhaust catalyst and in the diesel particulate filter (DPF). These compounds are not typically removed from the diesel par- ticulate filter during passive or active regeneration, and may result in ash accumulation on the catalyst or in the DPF, producing increased back pressure and the potential for reduced time between service intervals.
Sodium and Potassium
Sodium and potassium may be present in biodiesel as abra- sive solids or soluble metallic soaps. Abrasive solids can con- tribute to injector, fuel pump, piston and ring wear, and also to engine deposits. Soluble metallic soaps have little effect on wear, but they may contribute to filter plugging and engine deposits. High levels of sodium or potassium com- pounds may also collect in the exhaust catalysts and in the DPF. These compounds are not typically removed from the diesel particulate filter during passive or active regeneration and may result in ash accumulation on the catalyst or in the DPF producing increased back pressure and the potential for reduced time between service intervals.
Oxidation Stability
Products of oxidation in biodiesel can take the form of various acids or polymers, which, if in high enough concen- tration, can cause fuel system deposits and lead to filter clogging and fuel system malfunctions. Additives designed to terminate reactions leading to the formation of perox- ides that precede the formation of polymers and gums can significantly improve the oxidation stability performance of biodiesel.
ASTM Test Methods
Number Title
D93 Test Methods for Flash Point by Pensky- Martens Closed Cup Tester
D130 Test Method for Corrosiveness to Copper from Petroleum Products by Copper Strip Test D189 Test Method for Conradson Carbon Residue
of Petroleum Products
D445 Test Method for Kinematic Viscosity of Trans- parent and Opaque Liquids (and Calculation of Dynamic Viscosity)
D524 Test Method for Ramsbottom Carbon Residue of Petroleum Products
D613 Test Method for Cetane Number of Diesel Fuel Oil
D664 Test Method for Acid Number of Petroleum Products by Potentiometric Titration D874 Test Method for Sulfated Ash from Lubricat-
ing Oils and Additives
D974 Test Method for Acid and Base Number by Color-Indicator Titration
D975 Specification for Diesel Fuel Oils
D976 Test Method for Calculated Cetane Index of Distillate Fuels
D1160 Test Method for Distillation of Petroleum Products at Reduced Pressure
D1266 Test Method for Sulfur in Petroleum Products (Lamp Method)
D1796 Test Method for Water and Sediment in Fuel Oils by the Centrifuge Method (Laboratory Procedure)
D2274 Test Method for Oxidation Stability of Distil- late Fuel Oil (Accelerated Method)
D2500 Test Method for Cloud Point of Petroleum Products
D2622 Test Method for Sulfur in Petroleum Products by Wavelength Dispersive X-Ray Fluorescence Spectrometry
D2709 Test Method for Water and Sediment in Middle Distillate Fuels by Centrifuge D2880 Specification for Gas Turbine Fuel Oils D3117 Test Method for Wax Appearance Point of
Distillate Fuels
D3120 Test Method for Trace Quantities of Sulfur in Light Liquid Petroleum Hydrocarbons by Oxidative Microcoulometry
D3242 Test Method for Acidity in Aviation Turbine Fuel
D3828 Test Methods for Flash Point by Small Scale Closed Cup Tester
Number Title
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products
D4294 Test Method for Sulfur in Petroleum and Petroleum Products by Energy Dispersive X-Ray Fluorescence Spectrometry
D4530 Test Method for Determination of Carbon Residue (Micro Method)
D4737 Test Method for Calculated Cetane Index by Four Variable Equation
D4865 Guide for Generation and Dissipation of Static Electricity in Petroleum Fuel Systems
D4951 Test Method for Determination of Additive Elements in Lubricating Oils by Inductively Coupled Plasma Atomic Emission
Spectrometry
D5452 Test Method for Particulate Contamination in Aviation Fuels by Laboratory Filtration D5453 Test Method for Determination of Total
Sulfur in Light Hydrocarbons, Spark Ignition Engine Fuel, Diesel Engine Fuel, and Engine Oil by Ultraviolet Fluorescence
D5773 Test Method for Cloud Point of Petroleum Products (Constant Cooling Rate Method) D6217 Test Method for Particulate Contamination
in Middle Distillate Fuels by Laboratory Filtration
D6300 Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and Lubricants
D6450 Test Method for Flash Point by Continuously Closed Cup (CCCFP) Tester
D6469 Guide for Microbial Contamination in Fuels and Fuel Systems
D6584 Test Method for Determination of Free and Total Glycerin in B-100 Biodiesel Methyl Esters by Gas Chromatography
D6890 Test Method for Determination of Ignition Delay and Derived Cetane Number (DCN) of Diesel Fuel Oils by Combustion in a Constant Volume Chamber
D7039 Test Method for Sulfur in Gasoline and Diesel Fuel by Monochromatic Wavelength Disper- sive X-Ray Fluorescence Spectrometry 2.2 Government Standard:
40 CFR Part 79 Registration of Fuels and Fuel Additives Section 211(b) Clean Air ActA
2.3 Other Documents:
UOP 389 Trace Metals in Oils by Wet Ashing and ICP-OES
References
[1] Hoekman, S. K., Gertler, A., Broch, A., and Robbins, C.,
“Investigation of Biodistillates as Potential Blendstocks for Trans- portation Fuels,” CRC Project No. AVFL-17 Final Report, June 2009.
[2] Engine Manufacturers Association, Alliance of Automobile Manu- facturers, “Use of Raw Vegetable Oil or Animal Fats in Diesel Engines,” March 2006.
[3] McCormick, R. L., Alleman, T. L., Waynick, J. A., Westbrook, S. R., and Porter, S., “Stability of Biodiesel and Biodiesel Blends:
Interim Report,” prepared under Task No. FC06.9400, NREL/
TP-540-39721, April 2006.
Number Title
UOP 391–91 Trace Metals in Petroleum Products or Organ- ics by AAS
EN 14112 Fat and Oil Derivatives—Fatty Acid Methyl Esters (FAME)—Determination of Oxidation Stability (Accelerated Oxidation Test)
EN 14110 Fat and Oil Derivatives—Fatty Acid Methyl Esters (FAME)—Determination of Methanol Content
Number Title
EN 14538 Fat and Oil Derivatives—Fatty Acid Methyl Esters (FAME)—Determination of Ca, K, Mg and Na Content by Optical Emission Spectral Analysis with Inductively Coupled Plasma (ICP OES)
AAvailable from U.S. Government Printing Office Superintendent of Documents, 732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401.
6
Burner, Heating, and Lighting Fuels 1
C. J. Martin2 and Lindsey Hicks3
ALTHOUGH MOST PETROLEUM PRODUCTS CAN BE used as fuels, the term “fuel oil,” if used without qualification, may be interpreted differently in various countries. For exam- ple, in Europe, fuel oil generally is associated with the black, viscous, residual material that remains as the result of refin- ery distillation of crude oil, either alone or in a blend with lighter components, and it is used for steam generation for large slow-speed diesel engine operation and industrial heat- ing and processing. In the United States, the term “fuel oil” is applied to both residual and middle distillate type products, such as domestic heating oil, kerosine, and burner fuel oils.
Because fuel oils are complex mixtures of compounds of carbon and hydrogen, they cannot be classified rigidly or defined exactly by chemical formulas or definite physical properties. For purposes of this chapter, the term “fuel oil”
will include all petroleum oils heavier than gasoline that is used in burners. Because of the wide variety of petroleum fuel oils, the arbitrary divisions or classifications, which have become widely accepted in industry, are based more on their application than on their chemical or physical properties.
Thus, it is not uncommon to find large variations in proper- ties among petroleum products sold on the market for the same purpose. However, two broad classifications are gener- ally recognized: (1) “distillate” fuel oils and (2) “residual”
fuel oils. The latter are often referred to as heavy fuel oils and may contain cutter stock or distillates.
Middle distillate fuel oils are petroleum fractions that have been vaporized and condensed. They are produced in the refin- ery by a distillation process in which petroleum is separated into fractions, according to their boiling range. These middle distil- late fuel oils may be produced not only directly from crude oil, that is, “straight-run,” but also from subsequent refinery conver- sion processes, such as thermal or catalytic cracking. Domestic heating oils and kerosine are examples of middle distillate fuel oils. Common terms for the lighter (distillate) products include range oil, stove oil, and furnace oil, with range and stove oil being the lighter of the products.
On the other hand, residual or heavy fuel oils are com- posed wholly or in part of undistillable petroleum fractions from crude oil distillation (atmospheric or vacuum tower bottoms), vis-breaking, or other refinery operations. The vari- ous grades of heavy fuel oil are generally produced to meet definite specifications to ensure suitability for their intended purpose. Residual oils are classified usually by viscosity in
contrast with distillates, which normally are defined by boil- ing range.