Comparative Study for Biodiesel Properties and Standards for Gas Turbine

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Due to the depletion of fossil fuels, decrease of the conventional oil reserves,
environmental and economic concerns, bio-fuels have gathered a significant attention
as alternative fuels for the future. Their applications in automobiles, industrial gas
turbines and aviation are increasing day by day. This article will discuss bio-diesels and
will provide an overview of their physical properties and compositions, which play an
important role in their injection, atomization, combustion performance and emissions.
Furthermore, it will be judicious to mention the conformity of bio-diesels and their
blends with the standards and regulations. Consequently, the purpose of this study will
be to reveal the acceptance criteria imposed by the standards in order to determine
which bio-diesels will be the most adequate.

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  • Today I will present you an interesting study on biodiesels . First we will look at their properties ()next at their standards , ()than explore their emissions and ()finally we will summarize their strength and weakness .
  • -The term biodiesel as defined by the ASTM is a long chain fatty acids of mono-alkyl esters derived from vegetable oils or animal fats , through a chemical process called trans-esterification . -In other words , vegetable oils or animal fats named triglycerides shall undergo a chemical reaction in the presence of alcohol and a catalyst to produce esters and glycerin. -Once separated from the glycerin and alcohol , esters can be called Free Fatty acid Alkyl esters FAAE which are the chemical name of biodiesels .
  • Now I shall present you the impact of different Feed stocks on the Fatty acids composition, from there we shall study their influence on the major biodiesel properties . The properties to be reviewed are :
  • -Viscosity and surface tension are important factors in the atomization process.-Globally Viscosity and surface tension of BIOD are higher than the conventional Diesel fuels . -These 2 properties found to be directly proportional to the degree of saturation and to the chain length and inversely proportional to the double bond configuration which is mainly presented in the unsaturated FA .-High viscosity and surface tension can have a negative impact on the atomization and spray characteristic, such as High SMD , low evaporation rate , low combustion efficiency and high rate of pollution
  • Biodiesels have to meet ASTM specification in order to be certified as a fuel . Till date all ASTM standards specified for Biodiesels are : ASTM D6751-11b : Specification for the pure biodiesel B100.ASTM D396-10:that allows up to 5% blends for the use in home heating applications and industrial burners. ASTM D975-11b:that allows up to 5% blends for the use in the on and off road diesel engines application .ASTM D7467-10 :that allows up to 20% blends for the use in on –off road diesel engines application .
  • -Regarding ASTM specification for Gas turbine fuels.ASTM D 1655 : For Jet A and Jet A1 , biodiesel is not accepted . Only in the incidental material section biodiesel if found shall be below <5 mg/kg . ASTM D 7566 D : the only non –conventional fuels accepted is SPK (synthesized paraffinic kerosene ). ASTM D 2880-03 : for conventional fuels Not for biodiesels . - can be used if it is in accordance to the limits specified in this specification .
  • -most of test methods specified for biodiesel were originally developed for petroleum diesel and Biodiesel were not in their scope of work. Figure shows the low precision of some test methods quoted by the ASTM 6751 for B100 -Detection of Phosphorus content : D4951 :not accurate in the detection of low levels such as limits specified for biodiesels -Calcium , magnesium & potassium , Sodium : EN 14538 : this test method is reporting the metals as additions -Sulfated Ash : D 874 : does not include bio-fuels in their scope statements . Acid no. : D 664 : does not include biodiesels in its scope statementsCloud point : D 2500 : ASTM had gave the choice between 3 test methods the one that is currently used shows lower accuracy than the other 2 . Glycerin no. : D 6548 : not applicable to all feed stocks since it does not cover high ranges of saturated FA acids.
  • -Some searches have questioned the calibration methods of tests that were not originally developed by the ASTM , like tests adapted from the European standards . -another important factor in evaluating the efficiency of a test method is the TPI . If a test gets a value below 0.8 it shall be considered inconsistent to the ASTM precision statement , and , so has to be revised . Some biodiesel tests found below the acceptance values. ( Distillation point D 1160 , cloud point ASTM 2500 , glycerin no. ASTM 6584 )
  • Experimental tests had been carried out using different Feed stocks , blending levels , atomization techniques and equivalence ratios .2 general trends were observed : No improvement in the Nox emission as concluded from the experience done on RR-GT engine . Biodiesel blends with Jet A 1 was not preheated . High viscosity , High SMD , low evaporation rate . Reduction in Nox emission was observed in the other 2 experiences that have adapted a different injection technique .
  • The reduction of Soot and CO and UHC emissions when biodiesel was used is correlated with to 2 parameters 1) O2 molecules present in the biodiesel composition which will encourage the combustion and gives cleaner emissions 2) the absence of aromatic rings as biodiesels is considered as an aromatic free fuel . This trend was observed through 3 different tests :
  • -Lots of improvements and researches are still required in order to allow us to build a reliable knowledge base relating to biodiesels . -One major problem for biodiesels is the cold flow property and the high viscosity , several laboratories are currently working on improving these parameters . -Standards and regulations should reconsider some test methods as well as the allowance for a higher blends .-Improving the production and agricultural technique of biodiesels and feed stocks require lots of coordination between several sectors such as biological , chemical , physical .. -Governments have to encourage the production and the consumption of biodiesels , through legislative and public policies .
  • Comparative Study for Biodiesel Properties and Standards for Gas Turbine

    1. 1. Combustion Research Laboratory Laval University Quebec City Comparative Study for Biodiesel Properties and Standards for Gas Turbine CI/CS 2012 Spring Technical Meeting May 13 - 16, 2012 University of Toronto Mina Youssef, Joachim Agou, Bernard Paquet, and Alain de Champlain
    2. 2. OVERVIEW 5/15/2012CI/CS 2012 Spring Technical Meeting2 • Definition • Production What is Biodiesel ? • Free Fatty Acid • Fuel Properties Biodiesel Properties • ASTM Standards • Consensus issues Fuel Standards and Regulation • Major tendencies • Limited data Emissions • Future Improvements ?Conclusion
    3. 3. What is Biodiesel ? 5/15/2012CI/CS 2012 Spring Technical Meeting3  Fuel composed of mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fats  Biodiesel is made through a chemical process called trans-esterification, whereby the glycerin is separated from the fat or vegetable oil  Fatty Acid Alkyl Esters = FAAE = Biodiesel
    4. 4. Biodiesel Production Basic 5/15/2012CI/CS 2012 Spring Technical Meeting4  FAME = Fatty Acid Methyl Ester if methanol is used as an alcohol during the process  FAME is widely produced due to the low price of methanol  FAEE = Fatty Acid Ethyl Ester if ethanol is used as an alcohol during the process  Biodiesel blends are denoted as, "BXX" with "XX" representing the percentage of biodiesel contained in the blend  B20 is 20% biodiesel and 80% petroleum diesel  Fatty Acids (FA) structure and composition should determine the final properties of the biodiesel (?)
    5. 5. BIODIESEL PROPERTIES OUTLINE 5/15/2012CI/CS 2012 Spring Technical Meeting5 Free Fatty Acid (FFA) percentage and influence FFAs Vs. Feedstock Main fuel properties impacted by the Fatty Acid profile • Viscosity • Surface Tension • Cetane number • Heat of combustion • Cold flow properties • Oxidative stability • Lubricity
    6. 6. Free Fatty Acid (FFA) influence 5/15/2012CI/CS 2012 Spring Technical Meeting6  Type and structure of the fatty acid esters present in biodiesel both play an important role  Structural features that influence biodiesel properties are:  Fatty acid chain length  Degree of un-saturation  Branching of chains (chemical bonds)
    7. 7. Feedstock Vs. FFA 5/15/2012CI/CS 2012 Spring Technical Meeting7  Shown below an approximative trend of the composition of FFA with respect to their feedstock 0% 20% 40% 60% 80% 100% Canola Saltflower Sunflower Corn Olive Soybean Peanut Cottonseed Yellow Grease Lard Beef Tallow Palm Coconut Saturated Unsaturated + cetane number + cloud point + stability increase with saturated FFA A general indicative trend shows that:
    8. 8. Viscosity & Surface Tension 5/15/2012CI/CS 2012 Spring Technical Meeting8 Higher viscosity & surface tension than petroleum based diesel • Increase with degree of saturation • Increase with chain length • Double bond configuration decrease viscosity Negative impact on atomization and spray • Sauter Mean Diameter (droplet size) • Evaporation rate • Combustion efficiency • Pollution
    9. 9. Cetane Number 5/15/2012CI/CS 2012 Spring Technical Meeting9 Higher cetane number than petroleum based diesel Decrease with decreasing chain length Decrease with increasing double bond configuration Positive impact on ignition Reduce ignition time delay Reduction NOx emissions* (depending on the degree of un-saturated acid) Too high cetane number leads to incomplete combustion and smoke emissions
    10. 10. Biodiesel Properties 5/15/2012CI/CS 2012 Spring Technical Meeting10 • Increases with the chain length • Fatty esters contribute up to 90% of heat of combustion in diesel fuel no.2 Heat of Combustion • Changes in biodiesel properties with longer storage duration • Autoxidation is due to the presence of double bonds • Rate of autoxidation dependent on the number and the position of double bonds Oxidative Stability
    11. 11. Biodiesel Properties (Cont.) 5/15/2012CI/CS 2012 Spring Technical Meeting11 • Higher CP and PP than conventional diesels • High saturated fatty % will display higher CPs and PPs • Negative impact it can clog the fuel filters and damage the fuel pump • Blending biodiesel in a higher portion decrease the CP and PP Cold flow properties • No significant effect (due to fatty acid composition) • Unsaturated acids exhibits a better lubricity than saturated • Restore fuel lubricity by mixing biodiesel to the low sulfur petroleum-derived diesel Lubricity
    12. 12. STANDARDS AND REGULATION OUTLINE 5/15/2012CI/CS 2012 Spring Technical Meeting12 ASTM •Biodiesel •Aviation Gas Turbine •Stationary Gas Turbine Adequacy and precision of some test methods Consensus issues
    13. 13. Standards and Regulation 5/15/2012CI/CS 2012 Spring Technical Meeting13 ASTM D6751-11b • Specifications for pure biodiesels (B100) ASTM D396-10 • Specifications for conventional fuel oils used for home heating and industrial boilers application (B1 to B5) ASTM D975-11b • Specifications for diesel fuel oils used for on-and off- road diesel applications (B1 to B5) ASTM D7467-10 • Specifications for diesel fuel oils and biodiesel blends (B6 to B20) Biodiesel must meet certain specifications in order to be certified as fuel. Almost all specification found for biodiesels:
    14. 14. Standards of Biodiesels for Gas Turbines applications 5/15/2012CI/CS 2012 Spring Technical Meeting14 Biofuel for Gas Turbines Aviation Sector ASTM D1655-11b For conventional fuels Jet A/A1 In the incidental material section: Biodiesel is allowed up to < 5mg/kg. ASTM D7566-11a For non- conventional fuels Only SPK is allowed Biodiesel is not allowed since it not an SPK Stationary Sector ASTM D2880-03 For conventional fuels Not for Biodiesels Can be used if it is satisfactory
    15. 15. Adequacy and Precision of Standards 5/15/2012CI/CS 2012 Spring Technical Meeting15 Low Precision of some ASTM Tests Phosphorus Bad in detecting low limits content Ca, Mg & Na, K Reporting metals as additions Sulfated Ash Test scope does not include biodiesels Acid number Test scope does not include biodiesels Cloud Point Some other test methods showed better accuracy Glycerin Number Not applicable for high ranges of FA acid
    16. 16. Reliable Calibration ? 5/15/2012CI/CS 2012 Spring Technical Meeting16 Calibration of NON-ASTM test methods • EN 14538 : For the determination of Ca , Mg & K , Na • EN 15751 : For the determination of the oxidation stability • EN 14110 : For the determination of the methanol content >1.2 Satisfactory 0.8-1.2 Improvement should be considered >0.8 Inconsistent to the ASTM precision statement  Test Performance Index (TPI)  Some Biodiesel tests found inconsistent <0.8
    17. 17. EMISSIONS OUTLINE 5/15/2012CI/CS 2012 Spring Technical Meeting17 Few Examples • Experimental Studies Major tendencies • CO • NOx • UHC • Smoke emission Limited amount of reliable data ?
    18. 18. Impact on the NOx emissions in Gas Turbines 5/15/2012CI/CS 2012 Spring Technical Meeting18 • Exp.1: RR-T56-A-15 test rig combustor • Not preheated • High SMD and Low evaporation rate NO improvement • Exp.2: Air blast atomizer with a heated co-flow air • Exp.3: Pressure atomizer + preheated fuel • Reduction in viscosity • Low SMD (droplet size) • Higher evaporation rate NOx Reduction
    19. 19. Impact of properties on the Soot formation 5/15/2012CI/CS 2012 Spring Technical Meeting19 • Presence of O2 molecules in the fuel composition → Encourage the combustion, hence low emission • Absence of aromatic rings General trend shows reduction of Soot, CO, and UHC emissions  Exp.1: RR-T63-A-700 (Helicopter engine)  Exp.2: Air blast atomizer with a heated co-flow air  Exp.3: Pressure atomizer and the blend was preheated
    20. 20. Lack of reliable data ? 5/15/2012CI/CS 2012 Spring Technical Meeting20  Information regarding the use of biodiesel in gas turbines is limited  The lack of reliable data about the emissions of CO, NOx, UHCs, and soot provokes divergent thinking Difference in combustion mode, equivalence ratio, pressure & temperature ratios C.I. Engines High blends  High NOx Gas Turbine High Blends  NOx ???
    21. 21. Biodiesel Advantages 5/15/2012CI/CS 2012 Spring Technical Meeting21 Reduction of Greenhouse gas emission Non-toxicity Biodegradability Safer to handle Can be produced virtually from any type of oil or fat
    22. 22. Future improvements 5/15/2012CI/CS 2012 Spring Technical Meeting22 Cold weather operation Specific calibration standards for biodiesel Specification for higher blending levels Producing enough feedstock oil to replace a large portion of petroleum (biology, chemistry, physics, economics) Legislative efforts can make technological advancement more economical while the industry develops (public policy)
    23. 23. Thanks for your attention. 5/15/2012CI/CS 2012 Spring Technical Meeting23 o Any questions?

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