Diesel fuel learning module


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Diesel fuel learning module

  1. 1. Notes on this draft: 03/06/06 This draft is provided with suggested visuals, mostly photography. We will schedule this photography after other drafts in this series are reviewed unless we can find or purchase stock photos that sill suffice. Writer’s comments This is V1.1 of the diesel fuel module rearranged -- with one exception -- to the revised outline from the client. I did not move "low sulfur diesel" and "ultra-low sulfur diesel" fuels to the alternative fuels section. They are not alternative fuels. Low sulfur diesel is the regular diesel you buy at the pump every day. Ultra-low sulfur diesel is what you'll buy at the pump when the new regulations take effect later this year. Also, while I moved "diesel fuel grades" under diesel properties, I really think they need to stand on their own as an /H1/ heading. Finally, I have a section -- contaminants -- which is not on the outline. I came across this subject while writing and it's in the spot in the copy I feel is most appropriate Diiesel Fuels V-1 3/7/06 1
  2. 2. ELECTRICAL AND ELECTRONIC SYSTEMS Learning Objectives The student will be able to: 1. Describe various diesel fuel properties 2. Describe various diesel fuel additives 3. Describe various alternative fuels used in diesel engines 4. Describe various performance combustion supplements Terms to Learn Additives Liquefied natural gas (LNG) Aromatic content Liquefied petroleum gas (LPG) Bacteria Low-sulfur fuel Biocide Lubricity Biodiesel Non-taxed dyes British Thermal Unit (BTU) Particulate mater Carbon Petrodiesel Cetane Pour point Cloud point Specific gravity Compressed natural gas (CNG) Sulfur Contaminants Sulfur dioxide Detergent Viscosity Diesel fuel grades Volatility Flash point Ultra-low sulfur fuel Fungus Water Heat Valve Water injector Hydrocarbon Hydrotreating /H1/ Introduction (Insert still of diesel fuel pump at gas station) Diesel fuel is produced from petroleum and is sometimes called petrodiesel. It’s basically a mixture of hydrocarbons (hydrogen and carbon) extracted from crude oil through a process called distillation. Diiesel Fuels V-1 3/7/06 2
  3. 3. During the combustion process, the chemical energy of the fuel is converted into mechanical energy to power the vehicle. Compared to gasoline, Diesel fuel contains approximately 18% more energy per unit of volume. This, combined with the greater fuel efficiency of diesel engines, contributes to a diesel engine’s relatively better fuel economy compared to a gasoline engine. Diesel fuel is also simpler to refine than gasoline. One of the drawbacks of diesel fuel is that it contains higher quantities of sulfur which result in harmful exhaust emissions. Strict EPA standards control the amount of sulfur allowed in diesel fuel. To reduce the sulfur content, the fuel undergoes special processing after distillation. /H2/ Low Sulfur Diesel Fuel (Insert still of truck on highway belching black diesel smoke.) The sulfur level in diesel fuel has been identified as a major contributor to harmful diesel exhaust particulate and sulfur dioxide emissions. In October 1993, the EPA limited the sulfur content in diesel fuels intended for highway vehicles to 500 parts per million (PPM). This was a significant reduction from the previous standard of 5000 PPM. This was done to reduce exhaust emissions, particularly particulate mater and sulfur dioxide. (Insert still of petroleum refinery plant.) Sulfur content is reduced during refining with one of the most effective processes being “hydrotreating.” This process involves the introduction of hydrogen into the refining process to remove sulfur and reduce aromatic hydrocarbons. Lowering the sulfur content of diesel fuel reduces its “lubricity” or its ability to lubricate moving arts, especially those in the fuel injection pump and injectors. Most fuel providers added a lubricity additive into the blend and there are aftermarket lubricity enhancers available. /H2/ Ultra-Low Sulfur Diesel Fuel Ultra-low sulfur is the new standard mandating the sulfur content in diesel fuel sold for highway vehicles in the United States. Diiesel Fuels V-1 3/7/06 3
  4. 4. The allowable sulfur content is 15 parts per million (PPM) which is a drop from the 500 PPM previously allowed. This new standard will greatly reduce emissions of sulfur compounds (blamed for acid rain). In fact, the EPA estimates that once this new ultra-low standard is fully implemented, nitrogen oxide emissions will be reduced by 2.6 million tons each year. Soot and particulate matter will be reduced by 110,000 tons per year. In addition to reducing emissions of sulfur compounds, this new fuel standard will allow the use of far more advanced emission control systems that would not survive under the previous fuel standard. These advanced systems can greatly reduce emissions of oxides of nitrogen and particulates. The switch to an ultra-low sulfur standard will further reduce the lubricating properties of the fuel. Diesel fuel providers will include an additive to restore the lubricity to required levels to prevent engine damage and maintain service component life. In addition, the processing used to produce ultra-low sulfur fuel reduces the aromatics and density of the fuel, which in turn results in a reduction of energy content (BTU/gallon and a slight drop in fuel mileage. /H3/ Ultra-Low Sulfur Fuel Introduction Schedule Ultra-low sulfur fuel will be the only diesel fuel legally available for highway use starting in 2006. The new ultra-low sulfur fuel will introduced progressively throughout North America. H4/ United States (Except California) Refinery: June 1, 2006 Terminal: September 1, 2006 Retailer: October 15, 2006 H4/ California Refinery: June 1, 2006 Terminal: July 15, 2006 Retailer: September 1, 2006 H4/ Canada: Diiesel Fuels V-1 3/7/06 4
  5. 5. Refinery: June 1, 2006 Terminal: July 15, 2006 Retailer: September 1, 2006 /H1/ Diesel Fuel Properties The refiner of diesel fuel has several methods of achieving the desired properties: • Choice of crude oil • Refinery processing • Refinery blending • Additives /H2/ Diesel Fuel Grades Diesel fuel has been categorized by the American Society of Testing Materials into three classifications or grades. These grades are numbers 1D, 2D and 4D. Grades 1D and 2D are used in diesel vehicles. Grade 4D is blended for use in marine applications and large stationary diesel engines that operate at a constant speed. 4D diesel is not suitable for use in vehicles. The higher the grade number, the heavier the fuel. Generally speaking, heavier diesel fuels produce more energy. However, the higher viscosity of a heavier diesel fuel can inhibit its flow properties in cold weather which can hamper starting and negatively impact overall engine performance. /H3/ Diesel Fuel #1 1D is the most refined diesel fuel among the three grades and it is the most volatile. It’s intended for high-rpm engines that experience frequent changes in speed and load. /H3/ Diesel Fuel #2 2D is the grade most commonly used in diesel vehicles, especially in warm to moderate climates. However, some diesel engines require Number 1D fuel in order to perform satisfactorily. Always follow the engine manufacturer’s fuel recommendations. /H2/ Heat Value Heat value is the amount of energy stored in one gallon of diesel fuel. The heat value indicates how well the engine converts the heat energy of combustion into actual work. Heat value is measured in British Thermal Units (BTUs). Diiesel Fuels V-1 3/7/06 5
  6. 6. The higher the heat value per gallon of fuel, the more power derived from each gallon of fuel used. The BTU content of number 2D diesel fuel is generally higher than that of number 1D diesel fuel. /H2/ Specific Gravity Diesel fuel specific gravity refers to a comparison of the density of fuel versus the density of water. In other words, specific gravity refers to the ratio of fuel density to water density. Water is the standard in this comparison and is assigned a specific gravity of one. (Insert still of hydrometer.) Diesel fuel is lighter than water and therefore its specific gravity will always be less than one. Specific gravity can be measured with a common hydrometer. The specific gravity of diesel fuels ranges from 0.8 to 0.94. Why is this important? Heavier fuels (higher specific gravity) generally have a higher Heat Value than lighter fuels. This means that specific gravity is a good indicator of the amount of BTUs present in a diesel fuel. More BTUs equal more energy and better performance. (Insert still or illustration of injector spray pattern.) Specific gravity also has an effect on the spray penetration of the fuel as it is injected into the combustion chamber. This in turn can impact ignition and burning characteristics as well as lubrication properties. You may encounter another scale to measure specific gravity devised by the American Petroleum Institute (API). On the API scale, diesel fuels range from 20 to 45. Again, the higher the number, the more BTUs contained in the fuel. /H2/ Cetane Number The cetane number refers to the ignition quality and is a measure of the ease with which the liquid diesel fuel is vaporized and ignited in the diesel engine. The higher the cetane number, the easier the fuel ignites when subjected to the elevated temperatures and pressures in the engine’s combustion chamber. A higher cetane number is beneficial during engine starting and warm-up, as well as in cold weather and in service with prolonged low engine loads. Diiesel Fuels V-1 3/7/06 6
  7. 7. The cetane rating scale runs from 0 to 100, with 100 being the highest ignition quality. A high cetane number also equates to lower exhaust emissions. Typically, diesel vehicle fuels have a cetane number between 40 and 55. A cetane rating of 40 or above is currently the standard for all on-highway diesel engines. However, a 50 cetane rating or higher is required in certain areas. In addition, newer diesel engines may require a higher cetane fuel rating. The engine service manual will specify which cetane number is required. /H2/ Volatility Volatility refers to a liquid fuel’s ability to vaporize. Diesel fuel must vaporize in order to ignite during the engine’s combustion process. Volatility is measured by the air-vapor ratio formed at a specific temperature. Diesel fuel volatility is represented by a 90% distillation temperature which is the temperature at which 90% of the diesel fuel is distilled off /H2/ Cloud Point The cloud point is the temperature at which crystals of paraffin wax begin to appear in the fuel. Another term for cloud point is “wax appearance point.” (Insert still of container of diesel fuel at cloud point.) Diesel fuel contains paraffin wax which is desirable as a source of energy and is normally dissolved in the fuel as a liquid. In cold temperatures, the wax begins to congeal and solid wax crystals can form in the fuel. These crystals can plug fuel lines and engine filters which in turn inhibit fuel flow and negatively impact engine performance. You can actually detect the presence of these wax crystals by a cloudy look to the fuel. As a general rule of thumb, if the fuel’s cloud point is at least 10 degrees below the ambient temperature, the engine performance should not suffer. Grade 2D diesel fuel has a cloud point of approximately 10 degrees Fahrenheit (-12 degrees Celsius). Grade 1D has a cloud point of 20 degrees Fahrenheit (-28.8 degrees Celsius). Special winter fuel blends, special additives and fuel heaters are all effective methods of preventing wax formation. Diiesel Fuels V-1 3/7/06 7
  8. 8. /H2/ Pour Point Pour point is simply the lowest temperature at which fuel can flow. The pour point of diesel fuel is 5 degrees Fahrenheit (8.8 degrees Celsius) above the temperature at which the fuel will not flow. Pour point is also approximately 10 degrees lower than the cloud point. In other words, as temperatures drop below freezing, wax crystals begin to form as the fuel reaches its cloud point. If the temperature continues to drop, the fuel will reach and exceed its pour point becoming too thick to flow and eventually becomes a solid. There are additives available which can improve fuel flow and lower the pour point in extremely cold temperatures. /H2/ Viscosity Viscosity is the degree to which a fluid resists flowing when a force is applied. Viscosity has an impact on: • Injector spray atomization • Ignition characteristics • Burn efficiency • lubrication Viscosity is measured by heating the fuel to a specific temperature (generally 100 degrees Fahrenheit, 38 degrees Celsius) and measuring its flow rate through a standardized orifice. Viscosity is expressed in either centistokes (cSt) or seconds Saybolt Universal (SSU). Diesel fuel viscosity generally falls within a range of 2.4 to 4.1 cSt or 34 SSU. Any fuel with a lower viscosity is too thin for diesel operation and its use could lead to engine damage, specifically to the injectors and other fuel system components. Diesel fuel also has a low viscosity index. This means the fuel is thin and flows easily when hot and thickens as the temperature drops. Diesel fuel can be too thin or too thick for proper engine operation so viscosity is a critical property in blending diesel fuel. /H2/ Lubricity In diesel engines, fuel pumps and fuel injectors are lubricated by the diesel fuel. Diiesel Fuels V-1 3/7/06 8
  9. 9. (Insert still of diesel pump) Diesel fuel lubricity is the measure of a diesel fuels ability to lubricate and reduce wear on the metal parts of these fuel system components. /H2/ Flash Point The flash point of a fuel is the temperature at which vapors formed above the surface of a liquid fuel will ignite when exposed to an open flame. Flash point has a minimal effect on engine performance and is more relevant in the handling and storage of the fuel. /H2/ Sulfur Content All diesel fuels contain varying amounts of various sulfur compounds. Excessive amounts of sulfur in fuel can lead to a number of engine reliability and performance problems. These include: • Accelerated piston, piston ring and cylinder wear. • Varnish formation on piston skirts • Crankcase oil sludge • Corrosive damage to finished surfaces, bearings and other engine components • Higher exhaust emissions • Damage to catalytic converter To minimize these potential problems and reduce exhaust emissions, regulations require a sulfur content no greater than .05% in highway diesel fuels. Sulfur is removed from diesel fuels through a process called hydrotreating. The process uses hydrogen along with a catalyst at temperatures between 500 – 800 degrees Fahrenheit (260 – 427 degrees Celsius) to create a reaction. The resulting reaction forms hydrogen sulfide which is separated from the hydrocarbon thereby lowering the sulfur content of the fuel. Reducing sulfur will in turn reduce sulfur dioxide emissions and sulfate particles for reduced harmful exhaust emissions. /H3/ Reduced Lubricity Diiesel Fuels V-1 3/7/06 9
  10. 10. One drawback of reducing the sulfur content of fuel is the corresponding drop in lubrication. Sulfur is the primary lubricating property in diesel fuel and lack of adequate lubrication can reduce the service life of engine components such as fuel injectors and injection pumps. Restoring lubricity is addressed in the blending process and through fuel treatment additives. /H2/ Aromatic Content Aromatic content is the presence of the benzene family in hydrocarbon compounds that occur naturally in the refining of diesel fuel. Other aromatic compounds of toluene, xylene and naphthalene are also present in the chemical make-up of the fuel. The aromatic content of diesel fuel is a product of the distillation process and contributes to harmful exhaust emissions. To reduce these harmful emissions, most state regulations now mandate a maximum aromatic content of 35% in on- highway diesel fuels. California regulations restrict the aromatics content to less than 10% in order to reduce emissions. Reducing aromatic content to 10% greatly reduces the lubricity of the fuel so many refiners treat the fuel with a lubricity additive. Note that diesel fuels with low sulfur, low aromatic content and a high cetane number enhance engine performance because of improved combustion. The result is easier engine start-up, smoother running, reduced engine noise and less smoke. /H2/ Carbon Residue Carbon residue refers to carbon deposits left in the combustion chamber. These deposits can be caused by incomplete combustion or the use of residual blend fuels. (Insert still of combustion chamber with heavy carbon build-up.) Excessive carbon deposits can have a negative impact on engine performance. Soot ash is another type of potentially harmful residue and results from either the base crude oil or oil additives. Soot ash can accelerate the wear on components such as fuel injectors, pistons and piston rings thereby reducing the service life of the engine. Diiesel Fuels V-1 3/7/06 10
  11. 11. Currently, regulations call for a maximum of .001% soot ash content in on- highway diesel fuels. /H1/ Fuel Contaminants Fuel contamination is common problem in diesel fuels and can affect engine performance, engine reliability and service life. /H2/ Water Water is the most common type of contamination in diesel fuel and can be the mot destructive. Water in a diesel fuel system is found in two forms, free and dissolved. Free water generally comes from one of three sources: 1. Bulk storage tanks 2. Condensation 3. Dissolved water (Insert photo of bulk storage tank.) As fuel is removed from storage tanks or vehicle fuel tanks, it’s replaced by air which contains water vapor or humidity. This water vapor is eventually condensed into liquid water. The second type of water found in diesel fuel systems is dissolved water. Dissolved water is found in virtually all diesel fuels. Currently, there is no method of removing dissolved water from diesel fuel. Since water is heavier than diesel fuel, it collects at the bottom of the fuel tank or storage tank. This water can be mixed with the fuel when the tank bottoms become agitated. This can occur when a tank is dispensing or receiving fuel. Water in the fuel can reduce engine power and lead to the corrosion of fuel system components. Since water cannot pass easily through nozzle orifices, water will accumulate, vaporize and then cause the tip to blow off the end of an injector. Diiesel Fuels V-1 3/7/06 11
  12. 12. In extremely cold temperatures, water in a fuel tank can turn to ice. Since ice is lighter than diesel fuel, it can actually float through the fuel system. This can create blockages in fuel separators, fuel filters and in extreme conditions, fuel pump injectors. Plugged fuel filters when the ambient temperature is above 10-degrees Fahrenheit are generally caused by frozen water and not the fuel itself. Water also reduces the lubricity of the fuel which can result in seizure and scoring of moving metal surfaces. Water can combine with sulfur in the fuel to form a strong corrosive acid. Water causes rusting of iron components, which in turn produces abrasive iron oxide particles. Significant quantities of these particles contribute to premature wear of close-tolerance, moving fuel system components. Finally, water in fuel contributes to the growth of micro-organisms which can multiply and eventually plug fuel filters. /H2/ Fungus and Bacteria Initially, diesel fuel is sterilized thanks to the high temperatures involved in refinery processing. However, fuel can quickly become contaminated with microorganisms present in air or water. These microorganisms contain bacteria (yeasts) and fungi (molds). While bacteria and fungi can occur in working fuel tanks, storage tanks where fuel is held for an extended period of time are a much better growth environment for this type of contaminant. Fungus and bacteria are introduced to diesel fuel through air or water and will spread throughout a fuel system when moisture is present. They actually feed on the hydrocarbons found in diesel oil. The presence of fungus and bacteria will shorten the service life of the engine filters. The only way to prevent these contaminants is through the use of a biocide fuel additive. If the contamination has been progressing for a prolonged period of time, a heavy biofilm may accumulate on the surface of the tank which will prevent the biocide additives from neutralizing the contaminants. In that case, the tank must be drained and manually cleaned. /H1/ Diesel Fuel Additives Diiesel Fuels V-1 3/7/06 12
  13. 13. (Insert still of a variety of aftermarket additive products.) For general use, in healthy engines operating in moderate temperatures, no fuel additives are generally required. In addition, premium brands and knowledgeable suppliers will often add the additives they feel will best meet the prevailing conditions or improve the quality of the fuel they sell. However, even with a high quality fuel, engine performance, cold weather operation, fuel stability, engine service life and other diesel fuel characteristics can be improved through the use of additives. Additives may be added to diesel fuel at the refinery, during distribution, at the terminal, by the marketer or the ultimate end-user customer. Any additives added to the fuel after it leaves the terminal are referred to as “aftermarket additives.” /H2/ Non-taxed Dyes Diesel fuel sold for use on highways is subject to the Federal Highways Fuel Tax and is clear or amber in color. Diesel fuel for stationary, commercial marine engines, agricultural and construction equipment and off-road use is not taxed. Neither is the fuel used in government agency and Red Cross vehicles. This non-taxed fuel is dyed bright blue or red to indicate that the tax has not been paid. (Insert still of container filled with dyed fuel.) The dye used to mark these fuels is so concentrated that that even a small amount of dye will mark a large quantity of fuel. Since it is illegal to use these fuels on highway vehicles, there are hefty fines for an operator caught using non-taxed fuels. Also note that off-road diesel fuel has a higher sulfur content which can lead to catalytic converter failure when used in an engine intended for highway use. /H2/ Cetane Booster This additive raises the cetane number of the fuel for faster start-ups, more efficient ignition, improved power and performance. In some cases, this additive can also reduce combustion noise and smoke. /H2/ Biocide Contaminant Control Diiesel Fuels V-1 3/7/06 13
  14. 14. Biocides are most effective in the prevention of bacteria and fungi as they work to neutralize the growth of these contaminants. These additives can also be used with varying degrees of success when bacteria and fungi microorganisms reach problem levels. However, if contamination is extreme, the fuel tanks, filters and other fuel system will have to be cleaned manually. /H2/ Injector Cleaner (Detergent) Fuel and crankcase lubricants can form deposits on the fuel injector nozzles. Excessive deposits can alter the injector spray pattern and reduce the efficiency of the combustion process and ultimately, the engine’s performance. Injector deposits can also result in increased exhaust emissions. Injector cleaners have the ability to bond to an existing deposit and an agent that dissolves the deposits so they can be burned in the combustion process. This additive also reduces the opportunity for deposits to form on the injector nozzles. /H2/ Lubricity Improvers Lubricity additives are used to compensate for the poor lubrication qualities of low sulfur and ultra low sulfur diesel fuels. Lubricity additives contain a polar group of agents that is attracted to metal surfaces. These agents cause the additive to form a thin surface film which acts as a boundary lubricant when two metal surfaces come into contact. /H2/ Smoke Suppressants Smoke suppressants use organometallic compounds as combustion catalysts to increase the efficiency of the combustion process. Adding these compounds to a fuel can help to reduce exhaust smoke particulates, black smoke and carbon dioxide. /H2/ Corrosion Inhibitors The presence of water in diesel fuel will ultimately lead to corrosion in pipes, tanks and other steel fuel system components. Diiesel Fuels V-1 3/7/06 14
  15. 15. Rust particles will form and break off which can plug fuel filters and increase fuel pump and injector wear reducing their service life. Over time, this corrosion will eventually eat holes in the steel components creating leaks. Corrosion Inhibitors are compounds that that attach to metal surfaces and form a barrier that prevents corrosion. /H1/ Winter Fuel Blends Diesel fuel number 2D loses its ability to flow at temperatures below 20-degrees Fahrenheit. This is caused by the formation of wax crystals. (Still of diesel fuel pump in snowy environment.) Most fuel companies offer a “winter blend” of the diesel fuel they sell during winter months in cold climates. In other words, Maine may receive a “winter blend” during winter months while the blend in Florida may not change throughout the year. Generally speaking, number 2D diesel fuel performs satisfactorily at or above 10- degrees Fahrenheit. In formulating their “winter bend,” oil companies adjust the cloud point (the temperature at which crystals of paraffin wax begin to appear in the fuel) to suit the various climatic conditions in different locations and during different times of the year. Lower the cloud point during winter months is generally done by the addition of heavier components (napthalenes and aromatics) and other fluidity improver additives. Some winter blends mix a small amount of Diesel number 1D fuel with 2D fuel. The addition of about 15% to 20% diesel number 1D to diesel fuel number 2 will reduce the cloud point of the fuel by about 5 degrees Fahrenheit. Winter fuel is lighter than summer fuel and is less economical. Both power and overall mileage suffers when diesel number 1 is added to the blend. /H2/ Winterizing Additives A number of aftermarket additives can be added to diesel fuel to minimize fuel system problems in low-temperature environments. /H3/ De-icing Additives Diiesel Fuels V-1 3/7/06 15
  16. 16. Water in diesel fuel freezes at low temperatures. If enough water is present in the fuel, the resulting ice crystals can block the flow of fuel to the engine by plugging fuel lines and fuel filters. De-icing additives incorporating low molecular weight alcohols or glycols can be added to diesel fuel to prevent ice formation. They prevent ice formation by giving the resulting additive/water mixture a lower freezing point than plain water. /H3/ Low Temperature Additives (Cold Flow Improvers) These additives (also known as Anti-gel agents) are designed to lower the diesel fuel’s pour point or cloud point, or improve its cold-flow properties. They contain polymers which interact with the wax crystals that form in diesel fuel when it’s cooled below its cloud point. The polymers minimize the effect of the wax crystals on fuel flow by modifying their size, shape and formation. To be effective, these additives must be blended into the fuel while the fuel is above its cloud point and before the wax crystals have formed. /H1/ Alternative Fuels Thanks to the constantly fluctuating price and uncertain availability of petroleum- based fuels, along with more stringent emissions standards, research is expanding in the development of alternate fuels. A number of alternative fuels are currently available but questions of easy availability, engine modifications, cost and fuel mileage have yet to be answered limiting their use and overall acceptance in the marketplace. /H2/ Biodiesel Biodiesel is a non-fossil fuel obtained from vegetable oil and anima fats. Biodiesel fuels are biodegradable, non-toxic and have significantly fewer emissions than petroleum based (petrodiesel) fuels when consumed. Biodiesel can be made from a number of sources. • Soybean, rapeseed, mustard, palm oil and hemp. • Waste vegetable oil Diiesel Fuels V-1 3/7/06 16
  17. 17. • Animal fats (tallow, lard and yellow grease) Plants offer the most promising sustainable source of biodiesel fuels. Plants use photosynthesis to convert solar energy into chemical energy. It’s this chemical energy that’s released when Biodiesel is burned. Biodiesel has combustion properties very similar to regular diesel fuel including viscosity, combustion energy and cetane ratings. It offers the same btu/gallon ratio as #1 diesel while offering better lubricity. It can accommodate winterizers and has a gel point slightly higher than diesel #2. Biodiesel offers a number of environmental benefits: • It reduces carbon monoxide (CO) emissions by approximately 50% and carbon dioxide emissions by 78% compared to pretodiesel. • It contains fewer aromatic hydrocarbons: 56% les benzofluoranthene and 71% less Benzopyrenes. • It has zero sulfur emissions. • It reduces the emission of particulates by up to 65%. Biodiesel can be mixed with regular diesel fuel in any amount, although the most popular blend is 20 – 30% soybean oil to 70-80% #1 diesel fuel. As a blend, little or no alteration to the fuel injection system is necessary which simplifies conversion. In addition to its advantages, Biodiesel also has a number of drawbacks to consider. For example, an important point to remember when switching to or blending Biodiesel is that this alternative fuel has solvent properties that can clean out the deposits built up from petrodiesel use and can clog fuel filters. Also note that Biodiesel can harm the rubber gaskets and hoses found in vehicles manufactured before 1992. Biodiesel is “hydrophilic” which means it has an affinity for water which as you’ve read earlier, can cause numerous problems in the fuel system. Finally, Biodiesel fuel currently costs significantly more than convention petro- diesel fuels. /H2/ Compressed Natural Gas (CNG) Natural gas is a cleaner alternative to conventional diesel fuel and it produces very low particulate and nitrogen dioxide emissions. Diiesel Fuels V-1 3/7/06 17
  18. 18. (Insert still of CNG tank.) As the name implies, compressed natural gas is compressed and stored in high- pressure cylinders. Compressed natural gas is composed primarily of methane and hydrocarbon and it offers a high carbon-to-hydrogen ratio. Hydrogen is an excellent fuel that produces good power, good fuel economy and minimal pollution. Because CNG is a gas, it does not have to be vaporized as a liquid fuel does. CNG enters the combustion chamber as a vapor making the combustion process significantly more efficient. /H2/ Liquefied Natural Gas Liquefied natural gas is made through a process called liquefaction. Natural gas is refrigerated to minus 260 degrees Fahrenheit to condense it into a liquid. The liquefaction process removes most of the water vapor, butane, propane and other trace gasses. The resulting LNG is more than 98% pure methane. The LNG returns to a vapor as the temperature rises. /H2/ Liquefied Petroleum Gas Liquefied petroleum gas (LPG) is a mixture of gasses produced from petroleum and made up primarily of propane and butane. LPG is stored under pressure to keep it in a liquid state. Because the pressure needed to liquefy the gas is considerable, the containers holding it must be constructed of heavy steel. LPG reverts back to a gas when the pressure is sufficiently reduced. The advantage of converting this gas to a liquid is in transportation and storage. The fuel is 250 times more dense as a liquid than it is as a fuel meaning more liquid fuel can be carried and stored in a smaller container. LPG has combustion qualities that equal or surpass diesel fuel. It burns with little air pollution, generates minimal solid residue in the engine and does not dilute the engine lubricants. /H2/ Water Injection Diiesel Fuels V-1 3/7/06 18
  19. 19. While water in the fuel is a problem, water in the combustion chamber can actually enhance performance while reducing emissions. In certain situations, the introduction of vaporized water into the cylinder at time of combustion can lower Nitrogen Oxide emissions and soot formation. Water injection can also result in better fuel economy. (Insert still of water injection kit or actual engine installation.) Water helps to cool the inlet charge of fuel which reduces high combustion temperatures and minimizes detonation. Water can also be mixed with other additives such as methanol, propane and CNG to produce more power and torque. Several after market companies make water injection kits designed for diesel engines. Care should be used when using water injection as it has the potential to reduce performance and damage the engine if not installed and calibrated correctly. Diiesel Fuels V-1 3/7/06 19