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ALTERNATIVE FUELS- Boidiesel- Lecture 6-7.pptx

  1. Difinition Biodiesel refers to a non-petroleumbased diesel fuel consisting of short chain alkyl (methyl or ethyl) esters, made by transesterification of vegetable oil, which can be used (alone, or blended with conventional petrodiesel) in unmodified dieselengine vehicles.
  2. Difinition  Biodiesel is a renewable fuel which can be made from vegetable oils, animal fats, or recycled restaurant grease. Believe it or not, this can then be used in diesel vehicles already on the road because its physical makeup is similar enough to petroleum diesel, but it burns much more cleanly. Biodiesel is also much safer. Not only is it easier on the environment if spilled, but it has a flashpoint of over 130 degrees celsius, compared to 52 for normal diesel. Pure biodiesel, known as B100, reduces carbon dioxide emissions by more than 75% compared with normal diesel.
  3. Biodiesel  Biodiesel is a renewable fuel that is produced from a variety of edible and non-edible vegetable oils and animal fats. It is mainly used as Alternative Fuel in Diesel Engine The term “biodiesel” is commonly used for methyl or ethyl esters of the fatty acids in natural oils and fats, which meet the fuel quality requirements of compression-ignition engines.  Straight vegetable oils (SVO) are not considered as biodiesel. The straight vegetable oils have a very high viscosity that makes flow of these oils difficult even at room temperatures. Moreover, presence of glycerine in the vegetable oil causes formation of heavy carbon deposits on the injector nozzle holes that results in poor and unacceptable performance and emissions from the engine even within a few hours of operation.
  4. Production of boidiesel  Biodiesel is produced by reacting vegetable oils or animal fats with an alcohol such as methanol or ethanol in presence of a catalyst to yield mono-alkyl esters.
  5. Properties of biodiesel  A variety of vegetable oils such as soybean, rapeseed, safflower, jatropha-curcas, palm, and cottonseed oils have been used for production of biodiesel. Waste edible oils left after frying/cooking operation etc., have also been converted to biodiesel for study of their performance. The biodiesel are also known as fatty acid methyl esters [FAME]. Recently non-edible oil produced from jatropha- curcas seeds has gained interest in India as this plant can be easily grown on wastelands.  The vegetable oil esters are practically free of sulphur and have a high cetane number ranging from 46 to 60 depending upon the feedstock. Due to presence of oxygen, biodiesels have a lower calorific value than the diesel fuels. European specifications for biodiesel or fatty acid methyl esters (FAME)
  6. Emission of biodiesel  The influence of biodiesel on emissions varies depending on the type of biodiesel (soybean, rapeseed, or animal fats) and on the type of conventional diesel to which the biodiesel is added due to differences in their chemical composition and properties. The average effects of blending of biodiesel in diesel fuel on CO, HC, NOx and PM emissions compared to diesel as base fuel are shown in Fig.8.7.The Table 8.19 gives change in emissions with 20 % blend of biodiesel in diesel and 100% biodiesel compared to diesel alone. These show the average of the trends observed in a number of investigations.  Use of biodiesel results in reduction of CO, HC and PM, but slight increase in NOx emissions is obtained. Reduction in CO emissions is attributed to presence of oxygen in the fuel molecule. A slight increase in NOx emissions results perhaps due to advancement of dynamic injection timing with biodiesel. The methyl esters have a lower compressibility, which results in advancement of dynamic injection timing with biodiesel compared to diesel. Lower SOF with biodiesel and advanced injection timing also results in lower PM emissions.
  7. Emission of biodiesel  Volumetric fuel consumption with biodiesel is higher than diesel due to its lower heating value. An increase of 10-11 % in fuel consumption compared to diesel may be expected when comparing their heating values. An increase in volumetric fuel consumption by 0.9-2.1% with 20% blends has been obtained.
  8. Biomass  Plant and animal material, especially agricultural waste products, used as a source of fuel.
  9. Biomass Conversion Technologies There are four types of conversion technologies currently available that may result in specific energy and potential renewable products:  Thermal conversion is the use of heat, with or without the presence of oxygen, to convert biomass into other forms of energy and products. These include direct combustion, pyrolysis, and torrefaction. 1. Combustion is the burning of biomass in the presence of oxygen. The waste heat is used to for hot water, heat, or with a waste heat boiler to operate a steam turbine to produce electricity. Biomass also can be co-fired with existing fossil fuel power stations. 2. Pyrolysis convert biomass feedstocks under controlled temperature and absent oxygen into gas, oil and biochar (used as valuable soil conditioner and also to make graphene). The gases and oil can be used to power a generator and some technologies can also make diesel and chemicals from the gases. 3. Torrefaction is similar to pyrolysis but in a lower operating temperature range. The final product is an energy dense solid fuel often referred to as “bio-coal”.
  10.  Thermochemical conversion is commonly referred to as gasification. This technology uses high temperatures in a controlled partial combustion to form a producer gas and charcoal followed by chemical reduction. A major use for biomass is for agriculture residues with gas turbines. Advanced uses include production of diesel, jet fuel and chemicals.  Biochemical Conversion involves the use of enzymes, bacteria or other microbes to break down biomass into liquids and gaseous feedstocks and includes anaerobic digestion and fermentation. These feedstocks can be converted to energy, transportation fuels and renewable chemicals.  Chemical Conversion involves the use of chemical agents to convert biomass into liquid fuels which mostly is converted to biodiesel.
  11.  Combustion - direct combustion of biomass is the most common way of converting biomass to energy - both heat and electricity. Compared to the gasification and pyrolysis it is the simplest and most developed.  Gasification - gasification is a high-temperature (1200-1400 Degree Celsius)thermo chemical conversion process but the process is used for production of gas, instead of heat.  Pyrolysis - thermal decomposition occurring in the absence of oxygen. We use pyrolysis to produce a liquid fuel, bio-oil or pyrolysis oil.
  12. Biogass  Biogas is the gaseous emissions from anaerobic degradation of organic matter (from plants or animals) by a consortium of bacteria. Biogas is principally a mixture of methane (CH4) and carbon dioxide (CO2) along with other trace gases. Methane gas, the primary component of natural gas (98%), makes up 55-90% by volume of biogas, depending on the source of organic matter and conditions of degradation. Biogas is produced in all natural environments that have low levels of oxygen (O2) and have degradable organic matter present. These natural sources of biogas include: aquatic sediments, wet soils, buried organic matter, animal and insect digestive tracts, and in the core of some trees. Man’s activities create additional sources including landfills, waste lagoons, and waste storage structures. Atmospheric emissions of biogas from natural and man-made sources contribute to climate change due to methane’s potent greenhouse gas properties. Biogas technology permits the recovery of biogas from anaerobic digestion of organic matter using sealed vessels, and makes the biogas available for use as fuel for direct heating, electrical generation or mechanical power and other uses. Biogas is often made from wastes but can be made from biomass energy feedstocks as well.  Getting energy out of biomass by burning it, turning it into a liquid or by turning it into a gas called bio gas. • It contains about 65% of methane gas as a major constituents
  13. Biogas production stages  Biogas is produced using well-established technology in a process involving several stages:  Biowaste is crushed into smaller pieces and slurrified to prepare it for the anaerobic digestion process. Slurrifying means adding liquid to the biowaste to make it easier to process.  Microbes need warm conditions, so the biowaste is heated to around 37 °C.  The actual biogas production takes place through anaerobic digestion in large tanks for about three weeks.  In the final stage, the gas is purified (upgraded) by removing impurities and carbon dioxide.
  14. Is biogas the same as biofuel  Biogas is only one of many types of biofuels, which include solid, liquid or gaseous fuels from biomass. Any combustible fuel derived from recent (non-fossil) living matter (biomass) may be considered a biofuel, including ethanol derived from plant products, biodiesel from plant or animal oils, as well as, biogas from biomass. All biofuels are produced from sources which are renewable and are included as a subset of renewable energy sources that also include energy produced from solar, hydro, tidal, wind, and geothermal sources. Biogas, like natural gas, has a low volumetric energy density compared to the liquid biofuels, ethanol and biodiesel. However, biogas may be purified to a natural gas equivalent fuel for pipeline injection and further compressed for use as a transportation fuel. Methane, the principal component in biogas, has four times the volumetric energy density of hydrogen (H2) and is suitable for use in many types of fuel cell generators.
  15. Examples of Biofuels  Ethanol: It is produced from sugarcane .Its CALORIFIC VALUE is less than petrol. It also less heat when compare to petrol.  Methanol: It is easily obtained from ethanol .Its CALORIFIC VALUE is too low when compared to gasoline and diesel.
  16. Advantages  It’s a renewable source of energy.  It’s a comparatively lesser pollution generating energy.  Biomass energy helps in cleanliness in villages and cities.  There is tremendous potential to generate biogas energy.  Biomass energy is relatively cheaper and reliable.  It can be generated from every day human and animal wastes, vegetable and agriculture left-over etc.  Growing biomass crops use up carbon dioxide and produces oxygen.
  17. Disadvantages  Cost of construction of biogas plant is high, so only rich people can use it.  Some people don’t like to cook food on biogas produced from sewage waste.  Biogas plant requires space and produces dirty smell.  It is difficult to store biogas in cylinders.  Transportation of biogas through pipe over long distances is difficult.  Crops which are used to produce biomass energy are seasonal and are not available over whole year.
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