Dört çeşit bitkisel yağın motorin alternatifi olarak kullanımı

Cığızoğlu, Kemal Barış
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Fen Bilimleri Enstitüsü
Bitkisel yağlar, yenilenebilir kaynaklara dayalı günümüzün en önemli motorin alternatifidir. Bitkisel yağların Diesel motorlarında doğrudan kullanımı, enjektörlerin tıkanması, yağlama yağının kalınlaşması, silindirde aşırı koklaşma gibi çeşitli sorunlara yolaçmaktadır. Bu sorunları gidermek için piroliz, mikroemülsiyon, transesterifikasyon ve seyreltme modifikasyon teknikleri uygulanmaktadır. Bu çalışmada seyreltme modifikasyon tekniği; ayçiçek, soya, mısırözü, zeytin ve kullanılmış ayçiçek yağlarına uygulanmış ve bitkisel yağ-motorin karışımlarının alternatif motorin özellikleri incelenmiştir. Karışım yakıtlar hacmen %20 oranında bitkisel yağ içermektedir. Alternatif motorinlerin yakıt analizleri yapılmış ve motor testleri gerçekleştirilerek motorine benzer yakıt özellikleri ve motor performanslarına sahip oldukları belirlenmiştir.
Vegetable oils are the most important biomass originated alternative motor fuels. The use of vegetable oils as source of energy has already been known by men for along time. History records that R. Diesel, the inventor of the engine that bears his name, used vegetable oils as a fuel in his engines as early as 1900. The OPEC oil embargo of the 70's, fuel shortages and rapidly escalating fuel prices caused a resurgence of interest in finding alternative fuels. The energy crisis sparked a renewed interest in the use of vegetable oils as fuels and today the subject continues to attract attention because of the successful results obtained in the applications.Liquid fuels are a vital necessity particularly for the continuation of agricultural production which mostly depends on diesel fuel. Timing of the field operations such as planting, cultivating, and harvesting is especially critical. For all of these operations a readily available supply of liquid fuel is essential and vegetable oil-based fuels seem to be convenient solution to the in the case an emergency occurs. Substitution of petroleum-based diesel fuels with vegetable oil- based fuel alternatives requires the establishment of an integrated system which involves the production, processing and end use of the new fuels on a dual technology strategy. The selected oil crop must be a valuable oil export crop and must be easily cultivated while it should readily be turned into liquid fuel according to demand changes. The equipments used for processing oil for the export and import markets should also serve as the production equipment for fuel alternatives at times of crisis and emergency. Such a biomass based technology when administrated properly is important especially for developing countries with rich agricultural potential. Türkiye is a developing country and more than 90% of the consumed crude petroleum is provided through imports which is a heavy burden on the country's agriculture based economy. Like most of the developing countries, Türkiye is endowed with rich biomass sources; with the completion of the South East Anotalia Project 1.6 million hectares of arid land will be irrigated and the oil crop production is estimated to increase by 73%. Proper selection of the oil crop for the area can easily create a valuable source for vegetable oil based liquid fuel production. Evaluation of such a renewable energy source seems to be the appropriate option which can help to solve the necessity of petroleum importation of the country in the future. Vegetable oils have heat contents that are approximately 90% of that of diesel fuel but their high viscosity is a major restriction in their direct use in compression ignition engines. Whereas short-term engine tests indicate a good potential for the whole of vegetable oil fuels, long-term endurance tests show that there are serious problems in using vegetable oil fuels. The major problems in using vegetable oils as fuels include: vai . Fuel line and filter clogging due to fines, phosphatide gums, waxes, or high melting saturated fat,. Polymerization or partial oxidation during storage of the oil, which raises viscosity,. Polymerization in the combustion chamber due to heat or free radicals which leads to deposits and ring sticking,. Injector coking and ring sticking due to the high viscosity and non volatility of the oils,. Pour ignition and combustion characteristics, resulting from improper atomization of this high viscosity fuel,. Polymerization of the triglycerids in the lube oil resulting in lubricating oil thickening. The four techniques proposed to solve the problems cited above are pyrolysis, microemulsion, transesterification and dilution. In this study dilution technique is applied. This study is an investigation on the evaluation possibilities as a diesel fuel alternative of the blends prepared by mixing sunflower oil, olive oil, soybean oil, corn oil and used sunflower oil with diesel fuel. The oils used in this study are the most widely consumed vegetable oils in Türkiye. The experimental work covers the steps cited below:. The characterization of the vegetable oils,. The preparation of the blend fuels,. The determination of the fuel properties of the blend fuels, and. The engine test of blend fuels. The oils were obtained from commercial market. The only refining step applied to used sunflower oil was filtration before determining its properties. The fatty acid composition of the oils was subjected to capillary gas chromatographic analysis with the apparatus of Hewlett Packard 5890 series II fitted with a flame ionization detector (FID). Fatty acid methyl esters were prepared for chromatographic analysis (GLC) using BF3 - methanol reagent. The working conditions were as follows: Column: Ultra 2 (25m x 0.32mm x 0.52nn film thickness of 5% diphenyl, 95% dimethyl polysiloxane); gases:N2, carrier gas: 2 ml/min, air: 374 ml/min, H2: 27 ml/min; injection temperature: 200°C; flame ionization detector: 250°C (FID) temperature; oven temperature program: 30°C(5 min), 30-170°C (5°C/min), 170°C(5 min), 0-20Q°C(3°C/min), 200°C( 30 min); detection response factor : 1.0. The major oil characteristics like density, refractive index, acid value, saponification value, iodine value were also determined according to the standard methods of analysis of fats and oils. As expected sunflower, soybean and corn oil were found to be rich in linoletc acid whereas olive oil was rich in oleic acid. The used sunflower oil was found to have the greatest amount and sunflower and soybean oils were found to have the lowest amount of free fatty acid. Blend fuels were prepared by diluting 20 volume part of vegetable oils with 80 volume parts of Grade No.2-D diesel fuel. This ratio was determined taking into consideration the previous works (namely those of F.Karaosmanoğlu and A.lşığıgür, given in the Kaynaklar section with numbers 45,46 and 47) and the fact that the blend fuels have to have a suitable viscosity and the engine has to operate without modifications. There wasn't any problem encountered while mixing the oil samples with diesel fuel. The blend fuels are named as follows: sunflower oil - IX diesel fuel: AKY; soybean oil - diesel fuel: SKY; corn oil - diesel fuel: MKY; olive oil- diesel fuel: ZKY; used sunflower oil - diesel fuel: KAKY. The viscosity of the diesel fuel used in the experimental study was found to be 2.610 cSt. The viscosity of the sunflower oil at the same temperature is 13, that of the soybean oil 11.8, that of the com oil 12.6, that of the olive oil 17 and that of the used sunflower oil is 14.2 times viscous than diesel fuel. The maximum viscosity value of a Grade No.2-D diesel fuel is 4.1 cSt at 40°C. As can be seen except ZKY, the blend fuels have close values to that of diesel fuel. The fuel properties namely the density, flash point, pour point, sulphur content, lower heating value, cetane index and the copper corrosion test of the blend fuels were determined according to the ASTM and the results were given in Table 2. A general evaluation indicates that blend fuels have similar properties to those of diesel fuel. The cetane index of ZKY was found to have the closest value to that of diesel fuel. Other blend fuels have cetane indexes over 40 which is restriction value for diesel fuels. Heating the fuel lines or fuel tank of the engine will certainly improve the viscosity and cetane index of the blend fuels. The flash points of blend fuels are somewhat higher than diesel fuel which is an advantage in storing, transporting and using these fuels. The sulphur content of the alternative fuels is approximately 20% lower than that of the reference diesel fuel. The gross heating value of blend fuels was %2 lower and their pour points were within the limits given for Grade No.2-D diesel fuel. Table 1. The Viscosities of the Vegetable Oils, Diesel Fuel and Blend Fuels. Engine tests, using reference diesel fuel and the fuel alternatives were performed on a Daimler Benz OM horizontal, six cylinder (cylinder volume: 4580 cm3) diesel engine having a pre-combustion chamber and a bore/stroke ratio 90mm/120mm and a maximum output of 66 kW at 2800 rpm was used in engine tests. The engine characteristics; power (Pe, kW), torque (Md, N nn), specific fuel consumption (be, g/kWh), brake mean effective pressure (Pme, kPa), thermal efficiency (r\,%) and smoke emissions were calculated as a function of revolution per minute (n, d/d) at full load for all of the blend fuels and at 2/3 load for AKY and KAKY. Since the blend fuels have lower heating value than diesel fuel, an increase was observed in specific fuel consumption when using the blend fuels. The blend fuels showed similar power values to that of the baseline diesel fuel. The highest J/J CD 3 U_ ?o c 0) m.o c CO "55 3 U. "0) (fl (D O ı/> Çü.e
Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 1996
Anahtar kelimeler
Bitkisel yağlar, Dizel yakıtlar, Plant oils, Diesel fuels