Energy Fuels 2010, 24, 4503–4509 Published on Web 07/23/2010
: DOI:10.1021/ef100505n
Investigation of the Performance and Emission Characteristics of Biodiesel Fuel Containing Butanol under the Conditions of Diesel Engine Operation Sergejus Lebedevas,† Galina Lebedeva,‡ Egle Sendzikiene,§ and Violeta Makareviciene*,§ †
Department of Marine Engineering, Klaipeda University Maritime Institute, I. Kanto 7, LT-92123 Klaipeda, Lithuania, Computer Science Department, Faculty of Natural Sciences and Mathematics, Klaipeda University Maritime Institute, I. Kanto 7, LT-92294, Klaipeda, Lithuania, and §Laboratory of Chemical and Biochemical Research for Environmental Technology, Lithuanian University of Agriculture, Studentu 11, Akademija, LT-53361, Kaunas, Lithuania
‡
Received April 22, 2010. Revised Manuscript Received June 22, 2010
To expand the raw materials base for the production of biodiesel fuel, it is advantageous to make use of biobutanol (B) produced from renewable resources, which can be used in two ways as fuel for diesel engines: by direct inclusion into multicomponent fuel for diesel engines or by producing fatty acid butyl esters from rapeseed oil. Multicomponent fuels D70/B30, D70/B15/RME(RBE)15, and D50/B25/RME(RBE)25 meet the standards for fossil diesel fuel (D) and biodiesel fuel in terms of the main indicators of quality. When 30% biocomponents are included in a mixture with fossil diesel fuel, the effective efficiency factor of the engine (ηe) is as high as that of pure fossil diesel fuel, and reductions are achieved in the emission of all harmful components (CO, HC, NOx, and BSN). Usage of a such mixture is more promising if compared with a mixture containing higher content of biocomponents. Increase of biocomponents to 50% causes an increase in ηe of up to 4% compared to that of fossil diesel fuel, reduction in emissions of CO and BSN, and little change in the level of NOx and HC emissions. Also, the three-component fuel containing rapeseed butyl esters has better qualities than fuel containing rapeseed methyl esters. The introduction of biobutanol in three-component mixture instead of ethanol is more promising due to the better performance and environmental characteristics of the fuel.
used in diesel and Otto engines. The production process of biobutanol is very similar to that of bioethanol.5-10 The same raw materials are used: maize, grain, sugar cane, sugar beets, and agricultural waste (straw and maize stems). Butanol’s properties as a fuel component are better than those of ethanol. Butanol mixtures with diesel fuel are less sensitive to water than ethanol mixtures,11 which tend to settle in layers when water is present. The calorific value of butanol is higher than that of ethanol or methanol, and the latent vaporific heat is lower than that of ethanol or methanol; therefore, an engine that uses this fuel is easier to start during winters. The good low-temperature properties of butanol fuels are also very significant. One of the main weaknesses of the performance of widely used biofuel based on rapeseed oil methyl esters (RME) is its limited possibility of use during intermediate periods as well as during the coldest periods of the year.12 Usage of various alcohols (methanol, ethanol, propanol, and butanol) in Otto engines has been tested in mixtures with petrol.13-15 Diesel fuel consumption increases constantly in comparison to that of petrol; therefore, it is necessary to look
1. Introduction The production and consumption of biofuel is affected by the European Commission’s regulations,1-3 which promote the production and usage of biofuel. Among the biofuels obtained from biomass containing cellulose, notable ones include bioethanol and the more promising biobutanol. Ethanol production company facilities can be easily transformed into facilities for the production of biobutanol,4 which can be *To whom correspondence should be addressed. Telephone/Fax: þ370 37 752292. E-mail:
[email protected]. (1) Directive 2003/30/EC of the European Parliament and the Council of 8 May 2003 on the promotion of the use of biofuels or other renewable fuels for transport. OJ L 123, 2003; pp 42-46. (2) Council Regulation (EC) No 1782/2003 of 29 September 2003 establishing common rules for direct support schemes under the common agricultural policy and establishing certain support schemes for farmers and amending Regulations (EEC) No 2019/93, (EC) No 1452/ 2001, (EC) No 1453/2001, (EC) No 1454/2001, (EC) 1868/94, (EC) No 1251/1999, (EC) No 1254/1999, (EC) No 1673/2000, (EEC) No 2358/71 and (EC) No 2529/2001. OJ L203, 2003; p 1. (3) Council Directive 2003/96/EC of 27 October 2003 restructuring the Community framework for the taxation of energy products and electricity. OJ L283, 2003; pp 51-70. (4) Du Pont Fact Sheet on Biobutanol. http://www.dupont.com/ag/ news/releases/BP_DuPont_Fact_Sheet_Biobutanol.pdf (accessed Mar, 2009). (5) Pfromm, P. H.; Amanor-Boadu, V.; Nelson, R.; Vadlani, P; Madl, R. Biomass Bioenergy 2010, 34, 515–524. (6) Ezeji, T. C.; Qureshi, N.; Blaschek, H. P. J. Biotechnol. 2005, 115, 179–187. (7) Ezeji, T.; Qureshi, N.; Blaschek, H. P. Process Biochemistry 2007, 42, 34–39. (8) Durre, P. Biotechnology 2007, 1, 1525–1534. (9) Ramey, D.; Yang, S.-T. Production of Butyric Acid and Butanol from Biomass. Final Report. Environmental Energy Inc., Department of Chemical and Biomolecular Engineering, The Ohio State University: Columbus, OH, 2004; pp 1-103. r 2010 American Chemical Society
(10) Festel Capital. Biofuel Technologies: Situation and Outlook in Europe. Production Technologies & Investment Opportunities. 2nd Generation Bioenergy & Biofuels; Rueschlikon, Sep 12, 2006; pp 1-29 (http:// www.energyvcfair.com/download_06/session4_Gunter-Festel.pdf (accessed Jun, 2009). (11) Chotwichien, A.; Luengnaruemitchai, A; Jai-In, S. Fuel 2009, 88 (9), 1618–1624. (12) Dunn, R. O. J Am Oil Chem Soc. 2002, 79 (7), 709–715. (13) Pukalskas, S.; Bogdanovicius, Z.; Sendzikiene, E.; Makareviciene, V.; Janulis, P. Transport 2009, 24 (4), 301–307. (14) Zervas, E.; Montagne, H.; Lahaye, J. Environ. Sci. Technol. 2003, 37 (14), 3232–3238. (15) Butkus, A.; Pukalskas, S.; Bogdanovicius, Z. Transport 2007, 22 (2), 80–82.
4503
pubs.acs.org/EF
Energy Fuels 2010, 24, 4503–4509
: DOI:10.1021/ef100505n
Lebedevas et al. Table 1. Fuel Analysis Methods
parameter density viscosity
method
calorific value
EN ISO 12185 crude petroleum and petroleum products; determination of density, oscillating U-tube method EN ISO 3104 þ AC petroleum products; transparent and opaque liquids; determination of kinematic viscosity and calculation of dynamic viscosity EN 116 diesel and domestic heating fuels; determination of cold filter plugging point
flash point cetane number
EN ISO 3679 determination of flash point; rapid equilibrium closed cup method EN ISO 5165 petroleum products; diesel fuels; determination of ignition quality of diesel fuels; cetane engine method
for new raw materials and technological solutions in the production of fuel for diesel engines. One of the new raw materials for diesel fuel production could be butanol in pure form or in the form of butyl esters obtained by applying the vegetable oil transesterification process with butanol. Researchers have analyzed the properties of butanol mixtures with fossil diesel fuel (up to 30% butanol), and the emissions of engines fueled with such mixtures were evaluated.16 Aiming to increase the bioenergy part in transport sector production and the properties of multicomponent fuel containing fossil diesel fuel, fatty acid methyl esters and ethanol were investigated. It was found that the admixture of ethanol in fuel increased the indicated efficiency of a diesel engine and decreased the concentration of harmful components in exhaust gases.17 However, emissions of engines fueled with multicomponent fuels containing fossil diesel, butanol, and rapeseed oil butyl/methyl esters have not been tested. Production of the fatty acids butyl esters has been analyzed, though, by chemical and biotechnological methods.18,19 The use of alcohol-based biofuels for vehicles has largely been concentrated on bioethanol in Otto and diesel engines.17 The motor properties of butanol are less well understood, and studies have been limited mainly to spark-ignition internal combustion engines.20,21 Research of biofuel containing alcohols not only is limited to the energy and environmental parameters of engines22,23 but also includes aspects of operation and alcohol biofuel combustion kinetics20,21. The authors24 have extensively investigated the operational properties of and heat release in a one-cylinder Otto engine when operating with various petrol mixtures, from petrol to pure butanol. The effects of the process mixture spark timing and the engine compression ratio on the differential and integral characteristics of heat release were assessed. It was discovered that an increased proportion of butanol in a mixture with petrol improves the indicated efficiency factor by up to 3%. There has been, however, one study conducted on butanol motor properties and combustion characteristics with diesel engines.25
Table 2. Main Technical Parameters of the VALMET 320 Diesel Engine parameter
value
number of cylinders operational volume (dm3) cylinder diameter (mm) stroke (mm) fuel injection method high pressure pump starting pressure of fuel injection (MPa) nominal power (Penom) (kW) nominal rpm (nnom) (min-1)
3 3.3 108 120 direct injection sectional Bosch 23.5 ( 0.5 30 1500
Research into the use of butanol-containing biofuels in internal combustion engines is quite new in Lithuania, but the results regarding fuel consumption and the environmental impact of the butanol-petrol mixtures used in the Otto engine are noteworthy.26 By increasing the concentration of butanol to 50% in a mixture with petrol, CO and CO2 emissions were reduced by 80% and 15%, respectively, and effects on HC emissions were ambiguous. It should be noted that increased specific fuel consumption was detected due to butanol’s lower calorific value compared to that of petrol. The aim of our research was to analyze the possibility of using biobutanol in diesel engines and to evaluate the mixed fuel’s energy and environmental effectiveness. Comparative analyses were carried out in two directions: (1) laboratory and motor tests of three-component mixtures containing fossil diesel fuel, conventional biodiesel fuel (rapeseed methyl esters), and butanol and (2) laboratory and motor tests of threecomponent mixtures containing fossil diesel fuel, synthesized rapeseed oil butyl esters, and butanol. The biofuel’s energy and environmental and motor properties were tested under real conditions of diesel engine operation. 2. Materials and Methods 2.1. Materials. Analytical grade butanol (99.8%, Sigma Aldrich) was used. Rapeseed oil methyl esters (RME) were produced by JSC Mestilla. The quality characteristics of this product met the requirements of standard EN 14214 Automotive fuels; Fatty acid methyl esters (FAME) for diesel engines; Requirements and test methods. Commercial fossil diesel fuel (arctic, class 2) met the quality requirements of standard EN 590 automotive fuels; Diesel; Requirements and test methods. Rapeseed butyl esters (RBE) were synthesized in the laboratory through the conventional two-stage transesterification method by using an alkaline catalyst: potassium hydroxide. The ester content in this product was 97.1%. 2.2. Methods. Fuel analysis methods are presented in Table 1. Operational tests of multicomponent fuels were carried out with a VALMET 320 DMG three-cylinder diesel engine made by the manufacturer Agco Sisu Power. The main technical parameters of the diesel engine are given in Table 2. Engine load is assured by gradually increasing the consumption of electrical power generated by the diesel generator during the test. The load is increased from the near-idle mode to the full
(16) Karabektas, M..; Hosoz, M. Renewable Energy 2009, 34 (6), 1554–1559. (17) Lebedevas, S.; Lebedeva, G.; Makareviciene, V.; Janulis, P.; Sendzikiene, E. Energy Fuels 2009, 23 (1), 217–223. (18) Linko, Y.-Y.; Rantanen, O.; Yu, H.-C.; Linko, P. Factors Affecting Lipase Catalyzed n-Butyl Oleate Synthesis. In Biocatalysis in Non-Conversional Media, Progress in Biotechnology 8; Tramper, J., Vermue, M. H., Beeftink, H. H., von Stockar, U., Eds.; Elsevier Science Publishers B. V.: Amsterdam, 1992; pp 601-608. (19) Ghamgui, H.; Karra-Cha^abouni, M.; Gargouri, Y. Enzyme Microb. Technol. 2004, 35 (4), 355–363. (20) Gautam, M.; Martin, D. W. Proc. Inst. Mech. Eng. 2000, 214A, 497–511. (21) Gautam, M.; Martin, D. W. Proc. Inst. Mech. Eng. 2000, 214A, 165–82. (22) Zervas, E.; Montagne, H.; Lahaye, J. Environ. Sci. Technol. 2002, 36 (11), 2414–2421. (23) Zervas, E.; Montagne, H.; Lahaye, J. Environ. Sci. Technol. 2001, 35 (13), 2746–2751. (24) Szwaja, S.; Naber, J. D. Fuel 2010, 89 (7), 1573–1582. (25) Laza, T.; Kecskes, R.; Bereczky, A.; Penninger, A. Period. Polytech., Mech. Eng. 2006, 50 (1), 11–29.
(26) Pukalskas, S.; Bogdanovicius, Z.; Sendzikiene, E.; Makareviciene, V.; Janulis, P. Transport. 2009, 4, 301–308.
4504
Energy Fuels 2010, 24, 4503–4509
: DOI:10.1021/ef100505n
Lebedevas et al.
Table 3. Parameters of Measurement Devices measured components CO gas analyzer HGA 400 gas analyzer TESTO 330 XL smoke meter MDO-2 a
limits accuracy limits accuracy limits accuracy
CO2
0...10% vol 0...20% vol (5% (5% 0...20000 ppm 0...25% vol (5% (0.3% vol smokiness, 0-100% (2%
HC
O2
0...20000 ppm (5%
NO2
NO
NOx
0...22% vol (5% 0...25% vol 0...500 ppm 0...3000 ppm (0.2% vol (5% (5% coefficient of absorbance, 0-9.99 m-1 (2%
0...5000 ppm (1 ppma
Resolution.
load (Pefull) for engines operating with different types of fuel: 5-10% Pefull, ∼25% Pefull, ∼55% Pefull, 65-70% Pefull, and 80-85% Pefull at a rotation speed of n = 1500 min-1. Fossil diesel fuel was used at the beginning and at the end of the tests to ensure repeatability of the results and to control the stability of the engine’s technical parameters. An 884 Instructor precise fuel flow meter was used to measure the fuel input in the engine. The fuel flow meter ensures that measurement error does not exceed 0.1-0.5% (even some stand tests fail to achieve such precision). Parameters of the instruments used for the measurement of the harmful components in the engine exhaust gas are given in Table 3.
Table 4. General Characteristics of Fuels fuel diesel fuel butanol RME RBE ethanol
calorific value density at flash (MJ/kg) 15 °C (kg/m3) point (°C)
CFPP (°C)
cetane number
43
830
125
-32
48
33 37 38 27
810 840 840 789
28 150 150 13
-36 -15 -18
15 53 59.7 15
As mentioned above, the operational properties of fuel and the efficiency of diesel engine operation are highly influenced by the quantity of oxygen in the fuel.27,28 The oxygen content in fuel should not exceed 19%.29 Oxygen content in pure butanol is higher and equals 21.6% (see Table 6); therefore, before engine tests it was necessary to evaluate oxygen content if fuel mixtures contained butanol and rapeseed oil butyl esters. It was found that the mixtures without RME or RBE, i.e., consisting of 50% butanol and 50% fossil diesel fuel, were characterized by the highest oxygen content of 11%. However, this value does not exceed the established limit at which a reduction of efficiency of the diesel engine was detected. Therefore, any composition of fuel can be used for operational tests in the engine. Other physical and chemical properties of fuel mixtures were tested and compared with standard requirements (Table 6). It is important to note that it is difficult to compare the properties of new fuel mixtures with the requirements of standards EN 590 and EN 14214 because these standards are intended exclusively for pure fossil fuels and biofuels whose composition differs significantly from the composition of mixtures that we tested. There is no standard governing fuel mixtures, even for those containing only two components of significantly high concentrations (for example, B30 and B50). The fuel’s lower calorific value Hu of the tested multicomponent fuels is lower than that of fossil diesel fuel. It requires increasing the fuel-feeding portion during operation to ensure that the engine does not lose power and draft properties. An increase of the biofuel fraction in mixtures with D causes a proportionate reduction of the Hu value. The similar chemical composition of RME and BME biofuels also leads to similar Hu values. In the case of 30% RME and BME in a mixture with D, the reduction in Hu does not exceed 2%, i.e., it decreases from 42.4 MJ/kg for fossil diesel fuel to 41.5-41.6 MJ/kg for biofuel. In the case of 50% biocomponents (including the D70/B30 mixture), Hu is reduced by 6-6.5%. In some situations where diesel engines
3. Results and Discussions 3.1. Physical and Chemical Properties of Fuel Containing Butanol and Rapeseed Oil Butyl Esters. Fatty acid methyl esters are used as fuel in pure form or in mixtures with fossil diesel fuel, but they have poor low-temperature characteristics (cold filter plugging point and cloud point) than those of fossil diesel fuel. These characteristics depend on the nature of the biodiesel fuel, i.e., on the composition of fatty acids, their chain length, and the degree to which they are unsaturated. Tests of the cold filter plugging point (CFPP) of RME, REE, and RBE were carried out to assess how lowtemperature characteristics are influenced by the chain length of alcohol used for transesterification. The results showed that the CFPP of the conventional biodiesel fuel (rapeseed methyl ester) is -15 °C. CFPP values are lowered when alcohol chain length increases. The cold filter plugging point of REE reaches -16 °C and that of RBE reaches -18 °C (Table 4). This reveals that rapeseed oil butyl esters in mixtures with fossil diesel fuel are more promising for use during the cold periods of the year. The CFPP of pure butanol is equal to -36 °C, indicating that it would be useful to add it to mixtures. On the basis of the existing usage of B30 fuels in some EU countries, the possibility of using mixtures containing 70% fossil diesel fuel was analyzed. The possibility of increasing the quantity of biocomponents to 50%, where the RBE (RME) and B ratio is 1:1, was also investigated. Two-component mixtures containing fossil diesel fuel and butanol at a 7:3 ratio were analyzed as well. The characteristics of the tested mixtures and pure components are provided for comparison in Tables 4 and 5. The research results showed that the calorific value of methyl and butyl esters is lower than that of fossil diesel fuel, and that the cetane number is higher, especially that of butyl esters. This allows an increase of butanol concentration in the three-component D-RBE-B mixtures without having a negative influence on the mixture’s combustibility characteristics. The CFPP of butanol is equal to -36 °C, lower than that of fossil diesel fuel. An advantage of using three-component mixtures is that multicomponent fuels would have better properties, as compared to separate components.
(27) Zannis, T. C.; Pariotis, E. G.; Hountalas, D. T.; Rakopoulos, D. C.; Levendi, Y. A. Energy Convers. Manage. 2007, 48, 2962–2970. (28) Momani, W.; Abu-Ein, S.; Momani, M.; Fayyad, S. M. Am. J. Appl. Sci. 2009, 6 (5), 974–977. (29) Sendzikiene, E.; Makareviciene, V.; Janulis, P. Renewable Energy 2006, 31 (15), 2505–2512.
4505
Energy Fuels 2010, 24, 4503–4509
: DOI:10.1021/ef100505n
Lebedevas et al.
Table 5. Physicochemical Characteristics of Multicomponent Fuels and Limit Values of Standards para meter
value
EN 14214
EN 590
% (m/m)
min. 96.5 min. 51 860-900 3.5-5
max. 5 min. 51 820-845 2-4.5
ester content cetane number density at 15 °C viscosity at 40 °C calorific value (lower) CFPP
kg/m3 mm2/s MJ/kg °C
stechiometric air/fuel ratio l0 calorific value (lower) of air and fuel stoichiometric blend
kg of air/kg of fuel kJ/kg of air-fuel blend
A1 class A1 class (e-26 °C) (e-26 °C)
D70/ B30
D70/RME15/ B15
D70/RBE15/ B15
D50/RME25/ B25
D50/RBE25/ B25
46.2 833 3.45 39.8 -36
30 50.5 835 3.29 41.5 -29
30 51 832 3.39 41.6 -33
50 50.2 838 3.15 39.6 -27
50 51.8 833 3.32 39.8 -29
13.37
13.97
13.95
13.35
13.35
2770
2775
2780
2770
2800
Table 6. Elemental Composition of Multicomponent Fuels and Their Mixtures fuel composition D
RME (RBE)
C% B
100 100 70 50 70 50
15 25
100 30 50 15 25
H%
O%
RME RBE RME RBE RME RBE 87 77 64.9 80.4 75.9 80.9 78.2
78.4
81.1 78.4
13 12.3 13.5 12.9 13.1 14.2 13.6
12.1
14.2 13.7
0 10.7 21.6 6.7 11.0 4.9 8.2
9.5
4.7 7.9
Figure 2. Excess air factor when diesel engine is fuelled with multicomponent fuel and pure fossil diesel fuel (n = 1500 min-1).
Results of viscosity and density tests of three-component fuel containing fossil diesel fuel, butanol, and RME or RBE showed that the density of fuel containing RBE instead of RME when the components are in the same proportions is slightly lower, while the viscosity is slightly higher (see Table 6). It is worth mentioning that in the case where RBE is added rather than RME, the changes in the proportion of mixture components has less of an effect on the changes in mixture viscosity and density. The data in Table 6 show that all of the fuel mixtures investigated have good low-temperature properties. Their CFPP values (when no additives, i.e., depressants, are used) meet the requirements for winter-grade fuel class A1 (e -26 °C). Fuel of compositions D70/B30, D50/B50, and D70/RBE15/ B15 also meet the requirements of class A2 (e -32 °C). The studies were carried out not only to select optimal mixtures of fuels but also to evaluate engine characteristics, as well as the concentration of harmful components in exhaust gases when the engine is fuelled with selected fuel mixtures. 3.2. Performance Characteristics of Fuel Containing Butanol and Rapeseed Oil Butyl Esters. The engine tests were carried out by using the selected multicomponent mixtures and, for purposes of comparison, conventional fossil diesel fuel (D) and biodiesel fuel-rapeseed oil methyl esters (RME). To evaluate the working stability of a diesel engine, tests were first carried out with fossil diesel fuel, and operational load characteristics were recorded at the beginning, during the process, and at the end of testing. Hourly fuel consumption Gf and, more importantly, deviations in the experimental data for special effective fuel economy be from their approximation curves do not exceed their measurement error. On the basis of the above-mentioned facts, it can be concluded that the experimental data are reliable and represent a real change in the operational parameters of the diesel engine.
Figure 1. Break specific fuel consumption when engine is fuelled with fossil diesel fuel (n = 1500 min-1).
are used (for agricultural machinery, small-scale electricity generation, or tractors), such reduction of the maximum capacity by 2-6% does not require a special adjustment of diesel fuel feeding devices. Figure 1 shows break specific fuel consumption during the test. The air-fuel stoichiometric constant L0 (which indicates the quantity of air necessary for complete fuel combustion) of biofuel is lowered compared to that of D because of the above-mentioned difference in chemical composition (Table 5). However, the lower calorific value of the fuel stoichiometric mixture HUL =HU /(L0 þ 1), i.e., the lower calorific value of the fuel mixture, is more important when analyzing problems from replacing D with biofuel. First of all, when preparing a diesel engine for operation with biofuel without inflation aggregates, according to the HUL value, the tentative assessment of presumed change in maximal capacity is possible. HUL values of the tested fuels fall in the range to 27502800 kJ/kg, which is not significantly different from that of fossil diesel fuel (HUL =2750 kJ/kg). This means that there is no need to change work mode parameters or reduce the excess air coefficient factor R=Gair/(L0 3 Gf), in lockstep with the increase of the cyclic portion of the fuel, when preparing a diesel engine for operation with biofuel. 4506
Energy Fuels 2010, 24, 4503–4509
: DOI:10.1021/ef100505n
Lebedevas et al.
Figure 3. Break specific fuel consumption when diesel engine is fuelled with multicomponent fuel (n = 1500 min-1).
Figure 2 shows values of the excess air factor R of the diesel engine when used with each of the fuels being studied. The results obtained indicate that diesel engine preparation for work with biofuel does not negatively influence the formation of a working air-fuel mixture and its combustion. A reduction in R is not evident over the entire range of diesel engine loads for biofuel B30, and R increases by only 2-4% for the average and low-load modes. Increase of R when hourly fuel consumption is Gf - const is associated with an increase of hourly air consumption Gair; therefore, a working mixture of higher quality is formed, and the combustion process is more efficient. As a result, the increase of overall efficiency factor is observed (see Figure 4). In the case of biofuel B50 at Pe
