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Extracted Biodiesel as Feed for Internal Combustion Engine

Wubishet Degife, Melkamu Ashenafi, Raja Thiyagarajan, Omprakash Sahu*

Department of Chemical Engineering, KIOT Wollo University, Kombolcha (SW), Ethiopia

Abstract: Diesel fuel is very important for countries’ economy due to it has wide area of usage such as long haul truck, transportation, railroad, agricultural and construction equipment. Diesel fuel contains different hydrocarbons sulfur and contamination of crude oil residues. On the other side biodiesel does not contain any sulfur, aromatic hydrocarbons, metals and crude oil residues, which reduced the pollution level in Environment. In this work sunflower oil is used for production of biodiesel. In experiment catalysis loading 20%wt/wt, average 5 h methanol oil ration 15:1 and reaction temperature 150°C found to be suitable for biodiesel production. As well as 20% of biodiesel added with diesel show good performance in internal combustion engine.

Keywords: Biodiesel, High-acid oil, saturated fatty acids, Transesterification

Received October 30, 2014; Revised February 20, 2015; Accepted February 27, 2015

Citation: Wubishet Degife, Melkamu Ashenafi, Raja Thiyagarajan, Omprakash Sahu, Extracted Biodiesel as Feed for Internal Combustion Engine. Journal of Mechanical Design and Vibration, 3 (1). 1-7. January 2015. doi:10.12691/jmdv-3-1-1

1. Introduction

Biofuels are considered in part, a solution to such issues as sustainable development, energy security and a reduction of greenhouse gas emissions. Biodiesel, an environmental friendly diesel fuel similar to petro-diesel in combustion properties, has received considerable attention in the recent past worldwide. Our future economic growth considerably depends on the long-term accessibility of energy from the sources that are easily available, safe and affordable [1]. The global economic growth has seen a dramatic increase in the energy demand of the world. Energy consumption is expected to increase by 84 percent by 2035 in most of the developing countries. Ethiopia faces a dreadful challenge in meeting its energy needs and in providing sufficient energy of preferred quality in various forms in a sustainable manner and at competitive prices [2,3]. If Ethiopia has to eradicate poverty and meet its human development goals, then it has to sustain an 8% to 10% economic growth rate, over the next 25 years. For delivering a sustained growth rate of 8%, Ethiopia needs to increase its primary energy supply by 3 to 4 times. New sources of energy like biofuels may play a significant role in meeting the energy demands [4]. Biomass sources have turned out to be more effective in the recent days because of the insufficiency of conventional fossil fuels, their price hike and increased emissions of pollutants generated during combustion [5]. The petroleum-based fuel reserves are concentrated in only some parts of the world and these resources are depleting day by day [6,7]. The likelihood of producing biofuels from locally grown sources and using them as an alternative for various petrol products is one of the best attractive method to overcome the energy crisis. Any investments in biofuels will lead to a considerable boost in economic development [8]. It is expected that with suitable production process, biofuels will produce significantly lesser greenhouse gas emissions than are produced by fossil fuels.

The diesel engine came into its existence in the year 1893 when the paper titled “The theory and construction of a rational heat engine” was published by a great German inventor Dr. Rudolph Diesel [9]. The use of vegetable oil was first started by Rudolph Diesel. He developed the first diesel engine working on peanut oil at the World’s Exhibition in Paris, 1900 [10]. The main focal points for biodiesel production to expand were the oil seed crops. Until 1920s vegetable oils were utilized as the source of energy in the diesel engine. The factors like profitability, availability, low sulfur content, low aromatic content, biodegradability and renewability makes vegetable oils more advantageous over diesel fuel [11]. At present higher market values for challenging uses restricted the utilization of crops for biodiesel production.

Biodiesel refers to a processed fuel resulting from the biological sources and it is equivalent to petro-diese [12]. Biodiesel acts as a safe alternative fuel for substituting traditional petroleum diesel. It is a clean burning fuel with high lubricity. Biodiesel produced from renewable sources acts like petroleum diesel but produces significantly less air pollution. It is bio-degradable and very safe for the environment. Biodiesel production can be achieved in different methods. Biodiesel is a mono alkyl ester of fatty acids produced from both edible and non edible vegetable oils or animal fat and various other bio fuels such as methanol, ethanol etc. [13,14].

In recent times biodiesel has been produced from sources like vegetable oils, animal fats, soap stock and also recycled frying oils. In order to know which vegetable oil is best suited for the production of biodiesel, certain factors like geography, climate, and economics must be considered [15]. Vegetable oils are considered as the renewable forms of fuel and they are more attractive in environmental benefits as they are made from renewable resources. Vegetable oil potentially forms the unlimited source of energy; with an energy content equivalent to that of diesel fuel [16]. Direct use of vegetable oil in diesel engines gives rise to many problems such as jamming and gumming of filters, lines and injectors; engine knocking; starting problem during cold weather; coking of injectors on piston and head of engine; extreme engine Wear; carbon deposition on piston and head of engine [17]. Vegetable oils are of high viscosity and in order to reduce their viscosity and to overcome their problems to enable their use in many diesel engines, a process called transesterification must be carried out. The product so formed after transesterification is called as biodiesel. Biodiesel has relatively higher heating values. Biodiesel is 100% pure and hence it is referred as “neat fuel” or “B100”. The high heating values (HHV’s) of biodiesel ranges from 39 to 41 MJ/kg. Biodiesel can be utilized by blending with petrol diesel and those blends are referred as BXX where XX represents the amount of biodiesel in the blend. Pure biodiesel can be denoted as B100 [18].

Biodiesel production can be achieved using waste vegetable oils due to their low cost. They are collected from large food processing units and service facilities. They include several chemical reactions such as hydrolysis, polymerization and oxidation during food frying process, which leads to increased efficiency of fatty acids. In this regard’s an effort has been made to produce the low-cost ecofriendly and high efficiency biodiesel by Sunflower oil. The effect of temperature, catalysis loading reaction time and methanol oil ratio was studied. Obtained biodiesel was applied to diesel engine for performance test.

2. Materials and Methods

2.1. Material

Table 1. Fatty acid composition of sunflower oil

Sunflower oils were collected from local area and were used as feedstocks. Prior to transesterification, the waste food oil samples were dried over calcium chloride (CaCl₂) and filtered through a cellulose filter to remove any suspended matter and CaCl₂ crystals. Chromatographic grade methanol (99.5%), phosphoric acid, potassium hydroxide, sodium hydroxide, anhydrous sodium sulfate and calcium chloride were supplied by Lachema. (China), silica gel from Fluka (Buchs, Netherland), while the reference standard for the gas chromatographic determination of fatty acid methyl esters was obtained from Supelco (Bellefonte, USA). The fatty acid compositions of sunflower oil are shown in Table 1.

2.2. Transesterification Procedure

Biodiesel produced through the process known as transesterification. The reaction involved for the production is shown in Figure 1.

Figure 1. Reaction occur in Transesterification

Methyl esters (biodiesel) were synthesized in a batch type reactor using alkali catalysts. The ester preparation involved a two-step transesterification followed by purification and drying. The amount of Jatropha curcasoil used in the reaction was 200 g, which was placed in a dry two necked flask equipped with a thermometer and a reflux condenser. Dryness was absolutely necessary as water in the reactor would consume some of the catalyst, thereby slowing the reaction. The methanol and catalyst were added into the flask in the quantities to obtain the desired ratios relative to the oil. Namely, the study was realized using a mole ratio of methanol to Sunfloweroil of 3:1, 6:1 and of 9:1, whereas the catalyst (either NaOH or KOH) was added in quantities equivalent to 1 and 1.5 mass% of Sunfloweroil. In the first step, the mixture was stirred for 30 min at 30°C and 400 rpm, and then it was poured into a separation funnel. After one hour separation, glycerol was removed from the bottom of the flask, while the top esters layer was transferred into second two-necked flask, heated to 60°C and mixed with a second methanol/ catalyst solution. After stirring the mixture for 30 min at 400 rpm, it was poured into a separation funnel and allowed to separate for 12 h. The glycerol was removed by gravity settling and the methanol was removed from the thus-obtained crude esters layer by rotary evaporation at 65°C and 20 kPa. The obtained crude methyl esters were weighed and further purified by passing them through a bed of silica gel with a top layer of anhydrous sodium sulfate in order to remove the remaining salts and glycerol, as it was shown previously that high yields could be obtained in this manner from acidic feedstocks. The obtained dried methyl esters were then bottled and kept for characterization studies. The systematic flow diagram for the production of biodiesel is shown in Figure 2.

Figure 2. Flow diagram for the production of biodiesel

2.3. Characterization of Feedstocks and Methyl Esters

The feedstock WFO was characterized after drying and filtering (i.e., prior to transesterification) in a series of tests. Furthermore, the physical and chemical properties of the methyl esters (ME) obtained by two-step alkali transesterification after purification on silica gel were determined by the methods listed in the JUS EN 14214:2004 standard. [8] This standard is equivalent to EN 14214:2004 and defines the requirements and test methods for fatty acid methyl esters (FAME) to be used in diesel engines. Even though it is not required by JUS EN 14214:2004, the saponification value (Sv) was also determined using the titration method described in ISO 3657:2002. The iodine value (Iv) and Sv were also calculated based on the fatty acid (methyl ester) composition determined by gas chromatography [19]. In this way, an attempt was made to see if the calculated values could predict satisfactorily these two properties and be alternatively employed instead of the corresponding experimental procedures for their determination. A method for an estimation of the cetane index (CI) based on Sv and Iv was previously described, [20] as a simpler and more convenient method than the experimental procedure, for the determination of the cetane number utilizing a cetane engine (EN ISO 5165:1998). In this work, the experimentally obtained values of Sv and Iv were used for calculating CI. However, the proposed equation for CI is not recommended for feedstock characterization as it has been previously documented that the cetane indexes of oils are generally much lower than those of methyl ester derivates, despite the fact that they have similar Sv and Iv values [21].

2.4. Engine Specification

The performance tests were carried on a single cylinder, four strokes naturally aspirated, and water-cooled Kirloskar computerized diesel engine test rig. Diesel engine was directly coupled to an eddy current dynamometer. The engine and dynamometer were interfaced to a control panel, which was connected to a computer. This computerized test rig was used for recording the test parameters such as fuel flow rate, temperature, air flow rate, and load for calculating the engine performance such as mean effective pressure, power, brake specific fuel consumption, brake thermal efficiency, and emission like HC, CO, NOx and smoke [19]. The exhaust gas temperature, inlet and outlet water temperatures were measured through the data acquisition system and were fed to the computer. The exhaust gas was made to pass through the probe of Crypton computerized exhaust gas analyzer for the measurement of HC, CO, NOx and later passed through the probe of smoke meter of Bosch type for the measurement of smoke opacity. A whole set of experiments were conducted at the engine speed of 1400 to 3200 rpm and compression ratio of 17.5:1.

3. Results and Discussion

3.1. Effect of Catalysis Loading

Figure 3. Effect of catalysis loading on oil conversion under condition

The effect of the amount of catalyst used in the conversion of the triglyceride to methyl esters was studied as the percentage loading of catalyst with respect to oil was varied from 5 to 20% wt /wt keeping all other reaction parameters identical. As shown in Figure 3, it was observed that the oil conversion increased with an increase in catalyst loading. The highest conversion of 88% was obtained at a catalyst loading of 20% wt/wt which was comparative with the conversion value of 86% at 15%wt/wt. From the view-point of the reaction kinetics, a larger amount of catalyst leads to a higher yield of methyl esters in a shorter reaction time, however here we can say that this is sufficient from the viewpoint of economics. As a consequence, the optimal amount of catalyst used in this pilot was 15wt% loading as it was sufficient in catalyzing the reaction despite the challenge posed by the three phase reaction system where initial mass transfer control is inhibited due to heterogeneous kinetics. This is because of the fact that the solid catalyzed process is an immiscible liquid/liquid/solid 3-phase system (corresponding to oil, methanol and catalyst) that is highly mass transfer limited [22].

3.2. Effect of Reaction Time

In order to study the influence of the reaction time on the oil conversion using the KNO₃/flyash catalyst, a set of experiments were carried out at 2, 5, 10, 15 and 24 hours. The results are shown in Figure 4. It can be observed that the oil conversion was not greatly affected by an increase in the reaction time. This implied that, the reaction equilibrium had been reached after 5 hrs when the reaction temperature was 150°C. A study by Kotwal et al [23] showed that reaction times higher than 8 hrs had a negative impact on the oil conversion.

Figure 4. Effect of reaction time on oil conversion under condition

3.3. Effect of Reaction Temperature

Figure 5. Effect of reaction temperature on oil conversion under condition

Transesterification can occur at different temperatures depending on the oil used and temperature is a crucial parameter as it influences the reaction rate and yield of the methyl esters and in order to determine the effect of reaction temperature on the oil conversion, experiments were conducted at 25, 50, 100, 150 and 200°C. The results are shown in Figure 5 and from the activity profile, it was observed that as reaction temperature increased, there was a corresponding increase in the conversion of the triglycerides to methyl esters, showing peaks at temperatures ≥ 150°C. The highest conversion was 92.34% at a reaction temperature of 200°C which compares to the conversion value of 86% at the reaction temperature of 150°C. Artkla et al. [24] carried out the transesterification of palm oil with methanol at 60, 120 and 150°C in the presence of K₂O loaded on MCM-41 synthesized from rice husk. The performance depended on the K₂O loading and temperature with the highest conversion observed on 8% K2O/RH-MCM-41 at 100°C. However reports by Ramos et al. [25] showed that a methyl ester content of 95.1 wt% was obtained at 60°C by transesterification of sunflower oil over zeolites as catalyst using different metal loading.

3.4. Effect of Methanol and Oil Ratio

One of the most important factors that affect the yield of ester is the molar ratio of alcohol to triglyceride. It is of important for screening catalyst performance. Although the stoichiometric molar ratio of methanol to triglyceride for transesterification is 3:1 (Figure 1), higher molar ratios are used to enhance the solubility and to increase the contact between the triglyceride and alcohol molecules. Specifically, it has also been proven that that the use of excess alcohol is a good option in improving the rate of the transesterification reaction where heterogeneous catalysts are considered [26]. The effect of the molar ratio was of methanol to oil on the conversion of the methyl ester was examined by varying the amount of methanol with a fixed amount of sunflower oil (20 g) in the reactions at 150°C. The initial amounts of methanol were set and amounts corresponding to the methanol: oil molar ratios of 3:1, 6:1, 9:1, 12:1, 15:1 were used. The result is illustrated in Figure 6.

Figure 6. Effect of methanol and oil ration on oil conversion under condition

From the Figure, it can be seen that the highest methyl ester conversion of 87% was observed at a methanol: oil molar ratio of 15:1. It can be also be observed from the activity profile that as the molar ratio increased from 3:1 to 15:1, the conversion was found to increase from 47.3% to 87%. Further addition of methanol into the reaction phase did not show any significant increase in the conversion. Moreover, a limitation to the use of a greater amount of methanol needed to propel the forward reaction is that an occurrence of flooding of the active sites by the methanol molecules rather than triglyceride molecules which might hinder the completion of the triglyceride conversion to methyl esters as conversion at methanol oil ratios higher than 15 appeared to decline [27]. Also, feeding too much alcohol adversely affects the transesterification process by rendering the product separation difficult as glycerol; co-product specie of methyl ester is highly soluble in methanol, which reverses the transesterification progress according to Le Chatelier’s principle. Another important variable affecting the yield of methyl ester is the type of alcohol to triglyceride. In general, short chain alcohols such as methanol, ethanol, propanol, and butanol can be used in the transesterification reaction to obtain high methyl ester yields.

3.5. Physicochemical Parameter of Biodiesel

The calculated quality parameters are summarized in Table 2, and compared with the ASTM standards value.

Table 2. Comparatively result biodiesel with ASTM

Acid value of the biodiesel varied from 0.68 mgKOH/g to 0.89 mgKOH/g. The acid value is used to determine the amount of free fatty acid content in biodiesel. The lower acid value indicates that the quantity of free fatty acid in the biodiesel is also lower. Saponification value of the biodiesel was from 100.1 mgKOH/g to 111.5 mgKOH/g. Saponification value shows the amount of biodiesel that changes to soap by KOH in the at high temperature in presence of water. Lower saponification value of the result is higher in quality of the product. Thus, the residual soap is about 1.6%, and the waste water was taken at the first to get the maximum amount of waste in terms of soap during glycerol separation when biodiesel was being washed. Density of the biodiesel was from 839 kg/m³ to 843 kg/m³. Kinematic viscosity of biodiesel was from 2.90 mm²/s to 4.5 mm²/s. Thus, transesterification reaction reduced density and kinematic viscosity. Flash point of the biodiesel was between 132°C to 150°C. Flash point shows the first temperature where biodiesel is going up in to flames. From Table 2, high flash point values of the biodiesel were observed. Therefore, the flash point of the biodiesel is good for handling, storage or transportation. Moisture content was determined to be from 0.011% (w/w) to 0.019% (w/w) in the biodiesel. If there is high moisture content in the biodiesel, it causes further oxidation due to microbial growth during storage which reduces the shelf life and the product quality. The source of moisture in the biodiesel is highly related to wash water although there are other sources, such as poor drying [28]. Thus, the moisture content was obtained in the biodiesel was very small in amount as the biodiesel was dried in an oven for longer period of time at 105°C. The ash content of biodiesel was from 0.019% (w/w) to 0.029% (w/w). If high ash content is present, it shows that the biodiesel has solid materials that are resulted from catalysts during transesterification reaction or seed cake during oil extraction process. But the feed oil was refined and the biodiesel was washed with warm water and distilled water, with better mixing, low ash content was gained. Properties of biodiesel were under standard specification of ASTM. Iodine value and cetane number were not done due to lack of reagent chemicals and equipment. The lower density fuel burns quickly and consumed immediately while higher density fuel burns for longer time. The lower flash point fuel is more favor for spontaneous ignition while it is transported or stored for longer time. However higher flash point fuel resists such problems.

3.6. Power Output

Maximum power values were obtained at 2600 rpm for all blend fuels and diesel fuel, shown in Figure 7. There were no noticeable differences in the measured engine power output between diesel fuel and the blends fuels at lower speeds. However, at higher engine speeds, a slight decreasing in power output of the engine was obtained with B50 and B75, according to diesel fuel. Decreasing of power ranged from 0% to 6.2% depending on the amount of biodiesel and engine speeds. This is due to low calorific value of blend fuels [29,30].

Figure 7. Power output at load condition

3.7. Torque

Figure 8. Torque at load condition

The characteristics of torque curve did not change, according to the type of fuel, which shown Figure 8. Maximum torque point of engine was obtained at 2000 rpm for three blend fuels and diesel fuel. The maximum reduction of torque was 5.8% with blend of B60 at 1800 rpm. Average decreasing of torque values with blend fuels were 2.3% for B25, 3.8% for B50, and 5% for B75. The results showed that, in comparison with other blend fuels, higher torque values were usually obtained with B25 [31].

3.8. Specific Fuel Consumption

The lowest specific fuel consumption values were obtained at 2400 rpm with all test fuels which is shown in Figure 9. Usually, there was an interaction between specific fuel consumption value and calorific value of test fuels. Because, comparing with diesel fuel, increasing of specific fuel consumption with blend fuels ranged from 0% to 9.5%, depending on the amount of biodiesel [32]. At low and high engine speeds, increasing of specific fuel consumption was lower. Average increasing of specific fuel consumption values were 4.48% for B25, 5.9% for B50 and 8.7% for B75.

Figure 9. Specific flue consumption at load condition

3.9. Heat Loss on Exhaust

Heat loss to exhaust of engine is shown in Figure 10. The lowest percent heat losses to exhaust were obtained with blend of B25. The results showed that engine thermal efficiency of the engine with B25 increased. However, there were not significantly differences in percent heat loss to exhaust of engine between other blend fuels and diesel fuel.

Figure 10. Heat loss from exhaust at load condition

4. Conclusion

Fossils fuels are non renewable forms of energy resources and they are depleting day by day so the production of biofuels such as biodiesel is increasing rapidly. Biofuels like biodiesel are renewable, eco-friendly and non-toxic energy resources. Biodiesel is similar to petroleum diesel in its properties but biodiesel emits very less amount of CO₂, sulfur and particulates compared to petroleum diesel. It can be produced by a simple transesterification process using acid or base catalyst or enzymes as catalyst. From the experiment it was found that oil conversion increases with increased catalyst loading. The highest conversion of oil was obtained at a catalyst loading of 20%wt/wt. Influence of process parameters such as reaction time 5 h, reaction temperature 150°C and 15:1 molar ratio of methanol to oil are show maximum production of biodiesel. The oil conversion was not greatly affected by an increase in the reaction time. However, reaction time between 5 to 8 hours will lead to better oil conversion. The highest conversion was observed at a temperature of 200°C. The activity profile shows that increase in the methanol to oil ratio from 3:1 to 15:1 resulted in increased conversion from 43.7% to 87%. A decline in the oil conversion was observed when the recovered catalyst was recycled for use. In diesel engine power output shows better performance at 2600 rpm where torque is at 1800 rpm, fuel consumption at 2400 is less and heat loss is increase with increase in rpm. It is concluded that the biodiesel is one of the cheap and ecofriendly source for energy.

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