Preparation and emission characteristics of ethanol-diesel fuel blends

Journal of Enuironmental Sciences Vol 16, No 5, Pp. 793--796 2004Article nl:1001-0742(2004)050793-04CLC number: x511 Document code: APreparation and emission characteristics of ethanol-diesel fuel blendsZHANG Run-duo, HE Hong", SHI Xiao-yan, ZHANG Chang-bin, HE Bang-quan,WANG Jian-xin(1. Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China. E-mail: honghe mail rcees ac cn;2. State Key Laboratory of Automotive Safety and Energy, Tsinghua University, Beijing 100084, China)Abstract: The preparation of ethanol-diesel fuel blends and their emission characteristics were investigated. Results showed the absoluteethanol can dissolve in diesel fuel at an arbitrary ratio and a small quantity of water (0. 2% )addition can lead to the phase separation ofblends. An organic additive was synthesized and it can develop the ability of resistance to water and maintain the stability of ethanol-diesel-trace amounts of water system The emission characteristics of 10%, 20%, and 30% ethanol-diesel fuel blends, with or without additiveswere compared with those of diesel fuel in a direct injection( Di)diesel engine. The experimental results indicated that the blend of ethanolwith diesel fuel significantly reduced the concentrations of smoke hydrocarbon( HC), and carbon monoxide( CO)in exhaust gas. Using20% ethanol-diesel fuel blend with the additive of 2% of the total volume, the optimum mixing ratio was achieved at which the benchdiesel engine testing showed a significant decrease in exhaust gas. Bosch smoke number was reduced by 5596, HC emission by 70%0and CO emission by 45 %, at 13 kW/1540 r/min. However, ethanol-diesel fuel blends produced a few ppm acetaldehydes and moreethanol in exhaust gasKeywords: ethanol-diesel fuel blends: preparation; emission; acetaldehyde; ethanolIntroduction(Ajav, 1999 )also found that the COreduced by 36.8%,56.5%,58.8%, and 62.5% by theMotor vehicles have an important impact on air quality, use of 5%,10%6, 15%,anehich affects both human health and the environment. respectively, as compared to using diesel fuel alone. Inlegislations were introduced to limit the emission previous work( ajav, 1998; 1999; 2000; Noguchi, 1996;of CO, HC, nitrogen oxides( NOx), and smoke from vehicles Ahmed, 2001; Satge de Caro, 1997; 2001), the correlation(Ertl, 1999). The diesel engine has the advantage of lower between ethanol-diesel blends and exhaust emissions fromconsumption of fuel and lower emission of CO, carbon dioxide diesel engine had been researched for the case of regulated( Co,)and HC than usual gasoline engine. However, diesel pollutants(smoke, HC, NOx, CO). However, exhaust gasengine emits a large amount of smoke and NOx compared to contains other specific pollutants such as acetaldehydethe gasoline engine equipped with a three-way catalyst. It is ethanol that have not been thoroughly investigated soa suitable way to solve this problem by partially replacing New analytical method should be set up to determinediesel fuel by ethanol( Abu-Qudais, 2000; Ajav, 1998; amounts of acetaldehyde and ethanol in exhaust gas1999; 2000; Wang, 2002; Noguchi, 1996; Ahmed, 2001; Moreover, ethanol is a substance with polar molecules withSatge de Caro, 1997; 2001; Zervas, 2001; 2002; Reddy, properties similar to water and far away from diesel fuel. It is1999). Because replacing diesel fuel entirely by ethanolnecessary to introduce additive into ethanol-diesel blends torather difficult, researchers focus on particular substitute for stabilize the mixture in the presence of water and ensure thediesel fuel which consist of diesel fuel, ethanol and certain homogeneity and compatibility of blends under all conditionsdditivesThe influences of newly introduced additives on the emissionThe most common methods for achieving ethanol characteristics of ethanol-diesel fuel blends have not beenalternative fuel are ethanol fumigation( Abu-Qudais, 2000; well established. A study was, therefore, undertakenAjav, 1998), dual injection( Wang, 2002; Noguchithe objective of finding out the optimum method to par1996), ethanol-diesel fuel blend( Abu-Qudais, 2000; Ajavreplace diesel by ethanol with or without additive1999; 2000; Ahmed, 2001), and ethanol-diesel fuel comparing the emissions of various pollutants from dieselemulsion( Satge de Caro, 1997: 2001). An advantage of engine using ethanol-diesel fuel blends with or withoutethanol-diesel fuel blending is that no major component additive and diesel fuel alone. Considering the new organicchanges are required for its use. Small adjustments to the compound pollutants brought by blending ethanol with dieselinjection timing and fuel delivery may be necessary tofuel, the emissions of acetaldehyde and unbumed ethanolfull power( Eugene, 1984). M. Abu-Qubesides the emissions of regular pollutants( NOx, HC, COQudais, 2000 )studied the impact of ethanol-diesandblending on the performance and emissions of a single中国煤化工1M:cylinder diesel engine. He pointed out that the optimumCNMHGthanol percentage for ethanol-diesel fuel blends was 15 %, 1.1 athis produced a reduction of 32 in smoke level. Ajav elAdditive is mainly produced from oleic acid, polyvinylitem: The Knowledge Innovation Project of the Chinese Academy of Sciences( No. KZCX3-SW-430): the Chinese Academy of Sciences Program for AttractingOverseas Professionals; Corresponding author794ZHANG Run-duo et alVol. 16alcohol and lecithin. Oleic acid, polyvinyl alcohol, xyleand tetrabutyl phthalate were mixed together in the ratio of 2 Results and discussion15: 5: 3: 1. After stirring completely, this mixture was pourinto a rotary evaporator and evaporated at 70 C for 10 h under 2.1 Ethanol-diesel fuel blendsvacuum condition. 2% lecithin in the volume of preparedthanol is a hydrophilic organic compound containingmixture was added and mixed continuously, and then a hydroxyl functional group and can dissolve in water. Dieselyellow and viscousadditive was preparedfuel is a sort of product of petroleum. The1.2 Ethanol-diesel blend fuelcomposition of diesel fuel is depended on its original area andlol( Beijing Chemical Engineering Factory, process. In general, diesel fuel is mainly composedAR)and commercial diesel fuel( commercial diesel, 0, Cx saturated hydrocarbon, olefin, and arene. Because of theChinese Petrochemical Co ) were mixed together to get different polarity between ethanol and diesel fuel,itethanol-diesel mixture( ethanol diesel). 2% additive of the necessary to introduce some material to decrease the tensiontotal volume was introduced into this mixture. After stirring, between ethanol and diesel fuel to obtain an even, stableultrasonic vibration and filtering, an ethanol-diesel fuel blend ethanol-diesel fuel blend. The stability of ethanol-diesel fuelwas obtained( ethanol diesel +additive)blend is affected by diesel fuel composition, contained water1.3 Operational condition of diesel enginedensity, temperature and additive amount. In additionThe emission characteristics of ethanol-diesel fuel blendbecause diesel fuels also serve as lubricants for diesel enginewere carried out in a DI diesel engine rig. The test engine is (Abu-Qudais, 2000), with this regards the properties ofa two-cylinder unit, Model 295TA with a compression ratio of additive should not have an obvious distinction from those17: 1 and a displacement of 2000 cm'. The engine rated diesel fuel in order to avoid the problem in the practicalpower is 20 kW at a speed of 2200 r/min. Engine speed andin diesel engine. Low cost and easy obtaining of fuel blendsload were detected and controlled by tachometer and electric are also the factors that should be considered in practiceeddy dynamometer. The engine speed was fixed at 1540 r/In this investn, ethanol was mixed with diesel fuelInd the range of engine load was from 20 Nm to 80 Nm at the ratio of 19, 3: 7, 1: 1, 7: 3, and 9: 1, respectivelyIt was found that absolute ethanol was highly soluble in diesel1.4 Analytical methods of exhaust gaslel. A homogenous ethanol-diesel mixture was obtainedwas divided into twothrough gas analysis system(AVLGEM-110, AVL Company, different condition in the presence of water because thehydrogen bond is formed between water and ethanol. TheBosch smoke number was detected by a FBY-1 smoke effect of water on ethanol-diesel mixture can not be ignoredanalyzer. Another part was collected by plastic sampling bag Water will be brought into diesel fuel during the process ofcoated with aluminum film. The concentrations ofstore and transportation, so the ability of resistance to wateracetaldehyde and unburned ethanol were quantitatively effect must be enhanced for ethanol-diesel blendsanalyzed by gas chromatograph( GC)/mass spectrometry(MS)Gradually adding water into 30 ethanol-diesel blendAgilent Company, America ) with a PLOT-Q capillary we observed cloudiness in the mixture followed by separationwhen water addition amount reached 0. 2% of the totalThis study of ethanol-diesel fuel focuses on its effectsvolume. Additive for ethanol-diesel fuel was prepared byon the environment, so more attention has to be paid to thesuitable method as described in the experimental sectionproduction and exhaust of new pollutants suchAdding 2% additive into the mixture of 30% ethanol+acetaldehyde and unburned ethanol after ethanol blendingdiesel +0.2 water, we found that the separationThe authors developed a quantitative method to determine the disappeared and the mixed solution became clear again.Thisamounts of exhaust acetaldehyde and unburned ethanol by additive has the surfactant properties to offer the maximumpermissible water content with an amphiphilic structure that isethanol-diesel fuel blend at the power of 3.4kW. SIM model aligned between ethanol-water and diesel fuel, therebyInaInreinforcing the structural affinities between the variousfragment ion of acetaldehyde and ethanol are 29, 44, 43 andcomponents of the mixture. The hydrophobic functional group31, 45, 27 respectively. As shown in Fig. I acetaldehyded ethanol were separated completely to ensure the accurateof the additive has a strong affinity with diesel fuel, while thehydrophilic part orients toward the ethanol-water moleculesSo the additive could improve the ability of resistance to waterAcetaldehyde 2.66 ppmand keep the compatibility of ethanol-diesel-water system4000Homogenous and stable ethanol-diesel fuel blend was中国煤化工adeCNMH PUmps. In this attemptRetention time. minshown in Table 1. Compared with diesel fuel, ethanol-dieselFig. I The GC/MS chromatogram of acetaldehyde and ethanolmixture has a low viscosity. This viscosity did not exceed theemissions by 20% ethanol-diesel fuel blend combustion at therequired minimum(2 Pa. s)of diesel fuel Satge de Caroload of 3, 4 kw2001). With the addition of additive, the viscosity ofNo 5Preparation and emission characteristics of ethanol-diesel fuel blendsethanol-diesel blend fuel increased up to 2.3 Pa' s. The effectively under excess oxygen condition( Sumiya, 1998)introduction of the additive improved the lubrication of dieselengine. At ambient temperature half of the viscosity of dieselfuel that is lost by adding ethanol can be recovered by usingthe additive. This additical use of ethanol-diesel fuel-dIeselTable 1 The viscosity of difTerent fuel at ambient temperatureEthanol Diesel fuel 30% ethanol30% ethanol-diesel mixture diesel fuel blendEngine power, kwIn conclusion, absolute ethanol can dissolve in diesFig. 3 The relationship between NOx concentrations and diesel engine loadsfuel at an arbitrary ratio. 0. 2% water addition leads to theappearance of separation. The additive can increase the2.4 Emission of HCability of resistance to water for ethanol-diesel fuel blends andEmission of HC increased with the increase inkeep the stability of ethanol-diesel-trace amounts of waterr as shown in Fig 4. When the engine posystemto 13 kW, HC concentration in exhaust gas for diesel fuel3.5was 2764 ppm higher than that at low loads. This result is3.o f 10% ethanol+diesel + 2%due to the fact of rich fuel air ratio at high loads. The HC2.5F=+20%ethanol+diesel+2%emission decreased to 1620 ppm with the blend of 30%ethanol in the absence of additive at 13 kw. At high loadsthe insufficiency of oxygen supply can not maintain a goodcombustion condition for HC. Ethanol is an oxygenateorganic compound that can improve the combustion of HCunder this condition. With the introduction of the additiveHC emission of ethanol-diesel blend fuel was less than that ofethanol-diesel mixture without using the additive. TheFig.2 The relationship between Bosch smoke numbers and diesel engine loads additive can improve the distribution of ethanol in diesel fuelso HC emission of ethanol-diesel fuel blends decreased even2.2 Trends of smoke level of exhaust gasmore in the presence of additive. The HC emission of 20Smoke is one of the major pollutants of diesel exhaust ethanol-diesel fuel blend can be inhibited by 70%comparedemission and is usually produced under high load condition. with that of diesel fuel at 13 kwFig 2 shows the correlation between smoke level and power ofdiesel engine. Smoke level of the exhaust gas was low atpower level lower 7 kw. As the power of engine increasedsmoke emission became heavier. Bosch smoke number is 3. 1hanol+dieselat 13 kw with the use of diesel fuel alone, while boschand 30% ethanol-diesel fuel blends, respectively, under thesame operating condition. This means that the blend of6810121416ethanol can significantly reduce the smoke in exhaust gas ofEngine power, kwthe diesel engine. As an oxygenated compound, ethanol canincrease the oxygen-to-fuel ratio in fuel-rich regions and Fig 4 The relationship between HC concentrations and diesel engine loadreduce the production of incomplete combustion particulatesThe optimum percentage for ethanol-diesel fuel blends is 2.5 Emission of CO20%. When the addition of ethanol is 20 %, an optimumCo is emitted from diesel engine as a product ofperformance was achieved with up to 55 less smokeincomplete combustion of fuel under usual condition. Fig. 52.3 Emission of noxshows that CO emission was almost constant at low loads. COFig. 3 shows NOx emission of diesel engine for emission became higher at high loads because of the increasecombustion of different fuels at various load conditions Itof the incomplete combustion of fuelclear from the figure that NOx emissions increased with theig.5 also indicates that the blend of ethanol suppressedincrease in engine load. NOx emission of 30% ethanol-diesel the CO emission significantly. With 30% ethanol blendingmixture in the absence of additive was higher than that ofonly 47n kw in the absence ofdiesel fuel. The ethanol-diesel fuel blend was prepared byadditive中国煤化工sut( Ahmed,200)introducing additive into ethanol-diesel mixture. Thco emCNMHGction of the additiveexperimental results showed that adding additive inhibited thelau ua of diesel fuel aloneNOx emissions. Due to the additive, the NOx emission levels Exhaust CO concentration of 20% ethanol-diesel blend fuel isof ethanol-diesel fuel blends were close to that of diesel fuel1531 ppm when the power of diesel engine is 13 kW, so itsSince NOx is also one of the main pollutants of diesel engine, Co level was decreased almost by 45 as compared with thewh數瞻4A20cmyremove NOxdiesel fuelZHANG Run-duo et alVol 16且3500Engine power, kWFig. 5 The relationship between CO concentrations and diesel engine loadsEngine power,Fig. 7 The relationship between unbumed ethanol concentrations and diesel2. 6 Emission of acetaldehydeAcetaldehyde is produced from the incompletecombustion of ethanol. Fig. 6 shows the effect of ethanol system. The ethanol-diesel fuel blends could reduce theddition on acetaldehyde emission at various load conditionsparticle level of combustion exhaust remarkably. When thIt seems that diesel fuel combustion just produced littlediesel engine power was 13 kW, smoke level decreasedamounts of acetaldehyde( within 3 ppm). Adding 30% 54.8% when using 20% ethanol-diesel blend fuel comparedthanol into diesel fuel, the concentration of exhaust with operation on diesel fuel alone. Meanwhile, ethanolacetaldehyde increased up to 8.6 ppm when engine power was (especially ethanol and additive)addition also reduced the4.7 kW. The additive served to inhibit the emission of HC emission noticeably. Ethanol addition led to the increaseacetaldehyde. After introducing the additive, the of unburned ethanol emission, but the additive used couldacetaldehyde emission of ethanol-diesel fuel blend was similar suppress this emissionto that of diesel fuel. In general, the addition of ethanol into referencesfuel will not bring out any new environmental risksAbu-Qudais M, Haddad 0, Qudaisat M, 2000. The effect of alcohol fumigationon diesel engine perf86FoDieselethanol-diesel blends in CI engines[ R]. SAE Tech Pup Ser. No. 012475engine using vaporized ethanol as supplementary fuel J]. Biomass andBioenergy,15:493-502Ajay E A, Singh B, Bhattacharya T K, 1999. Experimental study of some6810ethanul-diesel blends as fuel[ J]. Biomass BioenerK, 17: 357-Engine power, kwAjay E A, Singh B, Bhattacharya TK, 2000. Thermal balance of a single cyliderdiesel engine operating on alternative fuels[J].Energ.Fig. 6 The relationship between acetaldehyde concentrations and dieselErtl G, Kndzinger H, Weitkamp ], 1999. Environmental catalysis[M]. WILEY-VCH Pres2.7 Emission of ethanolT J et al., 1984. State-of-the-art reportthe use of alcohols in diesel engines[ R]. SAE. Tech Pap Ser., No. 840118The change in ethanol emission in exhaust gas at various Noguchi N, Terao H, Sukata C, 1996. Performance improvement by control ofload conditions is shown in Fig. 7. It is clear that diesel fuelflow rates and diesel injection timing on dual-fuel engine with ethanol[ J]combustion did not produce any ethanol. More unburnedBioresource Technol, 56: 35-39ethanol was emitted with the blend of ethanol. When engine Reddy c V R, Krishna M V S M, PrasadC M V, 1999. Studies exhaustwas 4. 7 kw, the unburned ethanol emission of 30%emissions in semi -adiabatic compression ignition engine, Influence if fuel analence ratio[J]. Indian J Eng Mater S, 6(5): 249--255ethanol-diesel mixture was 132 ppm. The increase of Satge de Caro P, Mouloungui Z, Gaset A, 1997. Synthesis of derivatives ofunburned ethanol emission is due to an uneven distribution ofalkylamino alkyloxy proparethanol, which leads to the incomplete combustion ofnitration[ J]. J Am Oil Chem Soc, 74(3):241-247Satge de Caro P, Mouethanol. For ethanol-diesel blend fuel, unburned ethanolombining an additive with diesel-ethanol blends for use in diesel engemissions decreased with the addition of additive, TheiJIadditive facilitated the blend of ethanol and diesel fuel more Sumiya S Saito M, He H1998, Reduction of lean NOx by ethanolevenly to restrain the unburned ethanol emission.InAg/A1, 0, catalysts in the presence of H20 and So, [J]. Catal Lett87-91addition, the unbumed ethanol can be used as a specific Wang JX, Yan X G, Cheng y et al., 2002. Researches on combustion andreducing agent for selective catalytic reduction NOx( SumiyaINt Diesel. 20: 225-229X, ahave J. 2001. C-Cs organic acid emissions from an SI3 Conclusions中国煤化工 valence ratio[J]. nviron SciThe technology of ethanol-diesel fuel blend is an ZervasCNMHimportant method to reduce pollutant emissions from dieselcaught. Influence of fuel and air/fuelengineabsolute ethanol could dissolve into diesel fuel atquivalence ratio J]. Environ Sci Technol, 36: 2414-2421arbitrary ratio. Trace amounts of water(e. g. 0.2 %)additionReceived for review October 29, 2003, Accepted December 20, 200led to phase separation. An additive was prepared in order tokeep the stability of ethanol-diesel-trace amounts of water万方数