Energy Fuels 2010, 24, 2002–2009 Published on Web 12/30/2009
: DOI:10.1021/ef901158a
Physical and Chemical Properties of Ethanol-Biodiesel Blends for Diesel Engines )
Eloisa Torres-Jimenez,† Marta Svoljsak-Jerman,‡ Andreja Gregorc,‡ Irenca Lisec,‡ M. Pilar Dorado,§, and Breda Kegl*,§,^ †
)
Department of Mechanics and Mining Engineering, University of Ja en, C/Alfonso X el Sabio, 23700 Linares (Ja en), Spain, ‡ Petrol d.d., Ljubljana, Dunajska 50, SI-1527 Ljubljana, Slovenia, Department of Chemical Physics and Applied Thermodynamics, EPS, Ed Leonardo da Vinci, Campus de Rabanales, Universidad de C ordoba, 14071 C ordoba, Spain, and ^ Faculty of Mechanical Engineering, University of Maribor, Smetanova 17, SI-2000 Maribor, Slovenia. § Authors who contributed to the project leadership. Received October 11, 2009. Revised Manuscript Received December 8, 2009
This paper discusses the physical-chemical properties of ethanol-biodiesel blends considered as fuel for diesel engines. Attention is focused on the properties that significantly influence the injection, the engine characteristics, and subsequently, the exhaust emissions. In this context, the following properties have been investigated experimentally: fuel stability, density, viscosity, cold filter plugging point (CFPP), cloud point (CP), pour point (PP), flash point, filter plugging tendency (FPT), corrosiveness, lubricity, Fourier transformation infrared analysis, carbon-hydrogen-nitrogen (CHN) composition, and water content. Physical and chemical properties of biodiesel and ethanol-biodiesel blends have been measured according to the requirements and test methods for biodiesel (EN14214). The tested fuels were pure biodiesel (B100), 5% (v/v) ethanol-biodiesel blend (E05B95), 10% (v/v) ethanol-biodiesel blend (E10B90), and 15% (v/v) ethanol-biodiesel blend (E15B85). It has been proven that, for ethanol-biodiesel blends, additives are not necessary to ensure stability under low-temperature conditions. Furthermore, cold weather properties, such as CP and PP, are improved by adding ethanol to biodiesel. In general, the results show that ethanol in biodiesel influences beneficially the most important fuel properties of the blended fuel. Potentially, this may offer a possibility to improve engine characteristics. However, to confirm this assumption, further engine tests have to be performed.
season conditions, production technologies, and biofuel producers.6,7 Therefore, when considering a specific biofuel, a measurement of its properties is required.8 Some of the main concerns for burning bio-oils in diesel engines have to do with poor volatility, high viscosity, corrosiveness (acids), cold flow problems, and coking (thermally unstable components).9 Many investigations are focused on the influence of biodiesel and their blends with mineral diesel on engine performance and exhaust emissions, showing a slight decrease in engine power and an increase in NOx emissions.10,11 To moderate the NOx emissions, several strategies have been proposed, depending upon the fuel and injection system type.4,12-14 When using biodiesel-diesel and dieselbiodiesel-ethanol blends, it was found that CO and HC were significantly reduced at high engine load, whereas NOx increased, compared to the use of diesel fuel.4,15
1. Introduction The importance of issues such as energy security and the possible role of alternative and renewable fuels is now generally accepted, and first actions have already been initiated to produce a sustainable fuel supply. Biofuels for diesel engines comprise petrodiesel-biodiesel blends and pure biodiesel.1,2 Many biodiesel investigations are related to the usage of vegetable oils in modified or indirect injection diesel engines; e.g., Dorado et al.1,2 determined that a 10% (v/v) waste vegetable oil-90% (v/v) petrodiesel can also run a diesel engine, and Hribernik et al.3 tested pure waste cooking oil with good results. Biodiesel can be produced from many different raw materials, such as rapeseed, soy, olive, sesame, algae, and used frying oils.4,5 However, research has shown that biofuels differ to a great extent as a consequence of various raw materials,
(7) Dorado, M. P.; Ballesteros, E.; Lopez, F. J.; Mittelbach, M. Energy Fuels 2004, 18, 77–83. (8) Pinzi, S.; Garcia, I. L.; Lopez-Gimenez, F. J.; Luque de Castro, M. D.; Dorado, G.; Dorado, M. P. Energy Fuels 2009, 23, 2325–2341. (9) Mittelbach, M.; Remschmidt, C. Biodiesel: The Comprehensive Handbook; Martin Mittelbach: Graz, Austria, 2005. (10) Dorado, M.; Ballesteros, E.; Arnal, J.; Gomez, J.; Gimenez, F. J. L. Energy Fuels 2003, 17, 1560–1565. (11) Dorado, M.; Ballesteros, E.; Arnal, J.; Gomez, J.; Lopez, F. Fuel 2003, 82, 1311–1315. (12) Kegl, B. Fuel 2006, 85, 2377–2387. (13) Kegl, B. Energy Fuels 2006, 20, 1460–1470. (14) Szybist, J. P.; Boehman, A. L.; Taylor, J. D.; McCormick, R. L. Fuel Process. Technol. 2005, 86, 1109–1126. (15) Kwanchareon, P.; Luengnaruemitchai, A.; Jai-In, S. Fuel 2007, 86, 1053–1061.
*To whom correspondence should be addressed. E-mail: breda.kegl@ uni-mb.si. (1) Pischinger, G. H.; Siekmann, R. W.; Falcon, A. M.; Fernandes, F. R. Proceedings of the International Conference on Plant and Vegetable Oils as Fuels, American Society of Agricultural Engineers (ASAE), Fargo, ND, 1982; pp 198-208. (2) Dorado, M. P.; Arnal, J. M.; G omez, J.; Gil, A.; Lopez, F. J. Trans. ASAE 2002, 45, 519–523. (3) Hribernik, A.; Kegl, B. Energy Fuels 2009, 23, 1754–1758. (4) Nabi, M. N.; Akhter, M. S.; Zaglul Shahadat, M. M. Bioresour. Technol. 2006, 97, 372–378. (5) Dorado, M. P.; Ballesteros, E.; de Almeida, J. A.; Schellert, C.; Lohrlein, H. P.; Krause, R. Trans. ASAE 2002, 45, 525–530. (6) Dorado, M. P.; Ballesteros, E.; Mittelbach, M.; Lopez, F. J. Energy Fuels 2004, 18, 1457–1462. r 2009 American Chemical Society
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Energy Fuels 2010, 24, 2002–2009
: DOI:10.1021/ef901158a
Torres-Jimenez et al.
and transporting the fuel. Ghobadian et al.28 measured the flash points of several ethanol-biodiesel-petrodiesel blends and found that by adding only 3% ethanol reduces the flash point of the fuel blends almost to the flash point of pure ethanol. Filter plugging tendency (FPT) controls the quality of ethanol-biodiesel blends and predicts the applicability of these blends after long storage periods. Corrosiveness is also an important factor that needs to be considered, providing that parts of the fuel injection system and fuel tank could be damaged by the use of new fuels.29 Fuel lubricity characteristics play a significant role in the engine lubrication systems. In diesel engines, the fuel is part of the engine lubrication process and gains special interest when oxygenated blended fuels are used. Fuel quality determines whether a fuel can be commercialized. This is because the presence of contaminants can lead to severe operational problems, such as engine deposits.30 Fourier transformation infrared (FTIR) analysis is used in the present study to determine if any undesirable component (contaminant) is present in the sample. Using FTIR analysis, it is rarely, if ever, possible to identify an unknown compound, which is in contrast to the gas chromatography (GC) technique. However, FTIR analysis is becoming a preferred method for quality control of biofuels, because of its operational ease, rapidity of measurement, and nondestructiveness.30,31 Moreover, it is useful for identifying certain functional groups in molecules, and an IR spectrum of a given compound is unique and can therefore serve as a fingerprint for this compound. Consequently, by referring to known spectra, the region can be used to identify a compound. GC tests are used when it is necessary to obtain the fatty acid profile of any source, and these tests give information about which is the raw material of the biodiesel.32 Furthermore, when the water content exceeds the prescribed values (considering international standards), aqueous microorganisms can appear in the fuel tank.33 Thus, water content must be checked and controlled. Previous studies have demonstrated that low concentrations of biodiesel can be used as an emulsifier to avoid phase separation between petrodiesel and ethanol.15,34-36 However, the aim of the present study is to test biodiesel as a fuel for diesel engines and not only as an additive. In this paper, the most important physical and chemical properties of ethanol-biodiesel blends are analyzed and compared to those of pure biodiesel. Fuel properties such as stability, density, viscosity, CP, PP, CFPP, flash point, FPT, corrosiveness, lubricity, IR spectrum, carbon-hydrogennitrogen (CHN) composition, and water content are tested.
Fuel injection characteristics depend upon both the type of injection system and fuel properties.16-20 A significant influence of the biodiesel combustion temperature on injection characteristics has already been demonstrated.21 It is known that higher density, sound velocity, and bulk modulus of fuel cause advanced injection timing in mechanically controlled inline injection systems, thus increasing combustion temperature. This may be one of the reasons for increased NOx emission.13,22,23 Fuel properties do not influence the injection timing in electronically controlled common rail injection systems. Despite this, investigations show that the usage of biodiesel in common rail systems may also increase NOx.24 The fuel stability during a long time period as well as at various fuel temperatures is required to enable appropriate fuel injection and combustion processes. If a blend of various fuels separates after some time period, this means that variable fuel is injected into the cylinder. Because the engine management is optimized for a specific fuel, the engine characteristics will vary with respect to time. In this case, some additional mixing of blends will be necessary. Besides this, in the case of solidification of some fuel components at lower temperatures, fuel delivery to some cylinders may become seriously hindered, which is of course completely unacceptable. Fuel density, sound velocity, and bulk modulus of elasticity influence the injection characteristics significantly.13,25 At low temperature, fuel viscosity and density increase, which influence the increase of both the pressure drop through the filter and the flow resistance through the low-pressure pump gallery. The fueling through individual injection assemblies can vary considerably.26 The higher viscosity affects the atomization of a fuel upon injection into the combustion chamber and, thereby, ultimately increases the tendency of the formation of engine deposits. When viscosity is low, the engine power is reduced; however, increasing the fuel viscosity will negatively affect atomization and will also cause power loss.27 If cold filter plugging point (CFPP), cloud point (CP), and pour point (PP) properties are very high, this means that solids and crystals grow rapidly, agglomerate, clog fuel lines and filters, and cause major operability problems. To avoid possible problems when fuel passes through the filtration system, a low CFPP is recommended. This is important in low-temperate countries; a high CFPP will clog vehicle engines more easily. The flash point affects the shipping and storage classification. A lower flash point means higher precautions in handling (16) Yamane, K.; Ueta, A.; Shimamoto, Y. Int. J. Engine Res. 2001, 2, 249–261. (17) Bannikov, M. G.; Tyrlovoy, S. I.; Vasilev, I. P.; Chattha, J. A. Proc. Inst. Mech. Eng., Part D 2006, 220, 787–792. (18) Canakci, M. Bioresour. Technol. 2007, 98, 1167–1175. (19) Zhang, G. D.; Liu, H.; Xia, X. X.; Yang, Q. L. Proc. Inst. Mech. Eng., Part D 2004, 218, 1341–1347. (20) Wallace, F. J.; Hawley, J. G. Proc. Inst. Mech. Eng., Part D 2005, 219, 413–422. (21) C-etinkaya, M.; Ulusoy, Y.; Tekin, Y.; Karaosmanoglu, F. Energy Convers. Manage. 2005, 46, 1279–1291. (22) Kegl, B.; Kegl, M.; Pehan, S. Energy Fuels 2008, 22, 1046–1054. (23) Mittelbach, M.; Tritthart, P.; Junek, H. Energy Agric. 1985, 4, 207–215. (24) McCormick, R. L.; Graboski, M. S.; Alleman, T. L.; Herring, A. M.; Tyson, K. S. Environ. Sci. Technol. 2001, 35, 1742–1747. (25) Boehman, A. L.; Morris, D.; Szybist, J.; Esen, E. Energy Fuels 2004, 18, 1877–1882. (26) Kegl, B. Fuel 2008, 87, 1306–1317. (27) Ghobadian, B.; Rahimi, H.; Hashjin, T. T.; Khatamifar, M. J. Agric. Sci. 2008, 10, 225–232. (28) Li, D.; Zhen, H.; Xingcai, L.; Wu-gao, Z.; Jian-guang, Y. Renewable Energy 2005, 30, 967–976.
(29) Ribeiro, N. M.; Pinto, A. C.; Quintella, C. M.; da Rocha, G. O.; Teixeira, L. S. G.; Guarieiro, L. L. N.; do Carmo Rangel, M.; Veloso, M. C. C.; Rezende, M. J. C.; Serpa da Cruz, R. Energy Fuels 2007, 21, 2433– 2445. (30) Knothe, G. J. Am. Oil Chem. Soc. 1999, 76, 795–800. (31) Dorado, M. P.; Cruz, F.; Palomar, J. M.; del Rio, M. In Expoliva. Feria Internacional del Aceite de Oliva e Industrias Afines, Jaen, Spain, 2005; pp 1-6. (32) Van Gerpen, J. Report from Iowa State University for the National Renewable Energy Laboratory (NREL), 2004; NREL/SR510-36242. (33) Schleicher, T.; Werkmeister, R.; Russ, W.; Meyer-Pittroff, R. Bioresour. Technol. 2009, 100, 724–730. (34) Cheenkachorn, K.; Fungtammasan, B. Int. J. Green Energy 2009, 6, 57–72. (35) Cheenkachorn, K.; Narasingha, M. H.; Pupakornnopparut, J. Proceedings of the Joint International Conference on Sustainable Energy and Environment, Hua Hin, Thailand, 2004; pp 171-175. (36) Fernando, S.; Hanna, M. Energy Fuels 2004, 18, 1695–1703.
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Energy Fuels 2010, 24, 2002–2009
: DOI:10.1021/ef901158a
Torres-Jimenez et al. Table 1. Biodiesel Characteristics
limits EN 14214 (B100) minimum/maximum
property density at 15 C CFPP (seasonal specification applies) CP PP flash point sulfated ash content iodine number acidity number ester content linolenic acid methyl ester methanol content phosphorus content oxidation stability at 110 C monoglycerides content diglycerides content triglycerides content free glycerol total glycerol water content solid impurities sulfur content, WD-XRF kinematic viscosity at 40 C carbon residue corrosiveness to copper, 3 h at 50 C lubricity FPT pressure/volume element composition (CHN) a
unit 3
test method (standard)
B100
kg/m C
EN ISO 12185 EN 116
882.6 -10
minimum at 120 maximum at 0.02 maximum at 120 maximum at 0.5 minimum at 96.5 maximum at 12.0 maximum at 0.20 maximum at 10.0 minimum at 6
C C C % (m/m) g of iodine/100 g mg of KOH/g % (m/m) % (m/m) % (m/m) mg/kg h
EN ISO 23015 EN ISO 3016 EN ISO 2719 ISO 3987 EN 14111 EN 14104 EN 14103 EN 14103 EN 14110 PML.07.30a EN 14112
-3 -6 138.5
