Performance and Emission Studies of a Diesel Engine Using Biodiesel Tyre Pyrolysis Oil Blends 2013-01-1150 Published 04/08/2013 Abhishek Sharma and Bijay Dhakal NIT Rourkela,India Copyright 2013 SAE International doi:10.4271/2013-01-1150 ABSTRACT The latest trend world-wide, is to restrict the use of fossil fuels and replace them partially or totally by renewable fuels. In the present study, Jatropha methyl ester (JME) blended with tyre pyrolysis oil (TPO) was tested in a single cylinder, 4 stroke, air cooled, direct injection (DI) engine, to evaluate the performance and emissions characteristics. Four JMETPO blends, namely, JMETPO5, JMETPO10, JMETPO15 and JMETPO20 were used as fuel in the engine. The performance and emission results were analysed and compared with those of diesel operation. The results of the investigation indicate that the engine can run with JMETPO blends without any engine modification. The brake thermal efficiency of the engine fueled with the blends decreased marginally compared to that of diesel. The CO, HC and smoke emissions were found to be lower for the JMETPO blends in comparison with diesel. The NO emission increased with the JMETPO blends. The results are presented in this paper. INTRODUCTION Biodiesel is a renewable fuel and is of low toxicity. It can be made from vegetable oils, animal fats and algae. Fats and oils are chemically reacted with alcohol, using a chemical catalyst (NAOH/KOH) to produce chemical compounds known as fatty acid esters. Vegetable oils are often seen as a more suitable source for biodiesel production compared to animal fats and algae [1]. In the recent past, the utilization of biodiesel in compression ignition (CI) engines has significantly increased. It is reported that 20% biodiesel blended with 80% diesel fuel (B20) gives comparable performance and emission with that of diesel, when it is used in a conventional diesel engine. Nowadays, engines are manufactured for a configuration such as 100% biodiesel (B100) can be used with little or no modification. Transportation and storage of biodiesel do, however, require special attention [2]. Biodiesel has the potential to reduce the emissions of unburnt HC, CO, sulphates and particulate matter. This reduction increases with the blend percentage of biodiesel, and is the maximum with B100. Many countries have started using biodiesel derived from edible or non-edible seeds, as transportation fuels. However, the availability of seeds is limited, discouraging the use of biodiesel. The debate over the ethical and practical consideration of replacing mineral diesel with biodiesel is both lengthy and contentious [3]. The search for alternative hydrocarbon sources to be used as extenders of biodiesel to add to this replacement remains important. On the other hand, converting waste to energy through recycling is another possible solution for deriving alternative fuel. The disposal of solid waste is a prime task in the world today, as it causes severe environmental pollution. Waste automobile tyre is one of the solid wastes that are disposed in large quantities every year throughout the world. The waste tyre is composed of long chains of polymer fabrics, chemicals, steel, and wires. The tyres resist easy degradation when dumped in landfills. Combustion of tyres results in harmful pollutants, including polycyclic aromatics, hydrocarbon, benzene, styrene, phenols and butadiene. As a result, burning of tyres in the open is banned in many countries. Therefore, these two options are not good solutions for the disposal of waste automobile tyres. The other possible solution is pyrolysis and gasification. Pyrolysis is a simple method to convert waste automobile tyres in to value added products. In pyrolysis, long chain polymers are thermally broken down at high temperatures (300-900 C) into small molecules in the absence of oxygen. The recovered tyre pyrolysis oil (TPO), a mixture of paraffins, olefins and aromatic compounds, is a dark-brown liquid and has a
considerable heating value. Its properties are similar to those of diesel [4]. There have been several fundamental documented studies on the pyrolysis of waste automobile tyres. The research includes methods of pyrolysis (i.e. vacuum pyrolysis, flash pyrolysis, fluidized bed). Different operating parameters such as the heating rate, reactor temperature and reactor design have been examined [5]. Different types of tyres have also been investigated in the recent past for a better yield of value added products. Some of the researchers have investigated the type of reactors such as vertical and horizontal (rotating drum). A few catalysts (CaO, Ca(OH) 2 ) were also tried, for higher production of liquid pyrolysis oil [6]. In recent years, there have been commercial tyre pyrolysis plants installed around the world, especially in countries such as China, India, Canada, France, Italy and Spain, where a few pilot plants have come up with a production capacity in the range of 5-20 tons. TPO consists of C, H, O, N and S containing organic compounds and water. The organic compounds range from C 5 to C 20. Pyrolysis oil thus contains fractions of volatility consistent with gasoline, kerosene and diesel. As a result, the TPO was tried as an alternative fuel in both spark ignition (SI) engines and compression ignition (CI) engines. Only a limited number of studies have been previously performed to investigate the effect of tyre derived fuel/diesel blends on engine performance and emission as an alternative fuel for diesel engines. The previous experimental works by the authors studied the effect of lower and higher concentrations of the TPO/diesel blends on the performance, emission and combustion characteristics of a single cylinder, four stroke, air cooled, DI diesel engine running at 1500 rpm. It was reported that the HC, NO, CO and smoke emissions usually increased with increasing TPO content in the diesel blends. Furthermore, it was found that increasing the TPO content in the diesel blends increased the maximum combustion pressure, rate of pressure rise and ignition delay. The maximum TPO diesel blend was found to be 70%. Further, the engine was unable to run with more than 80% TPO diesel blends [7]. In another work, the influence of the distillation process on raw TPO properties and on engine performance and emissions was studied in a DI diesel engine by using three different test fuels (crude TPO, distilled TPO and diesel). The distillation process improved the fuel properties of crude TPO, and the engine test results showed that the engine performance and emissions improved considerably. Another publication by the authors reported that, the crude TPO, which was obtained by pyrolysis under a nitrogen atmosphere, was tested in a single-cylinder DI diesel engine and the test results showed similar trends with the pure diesel operation with respect to performance and emissions. Recently, a study was performed to evaluate the performance and emission characteristics of a single-cylinder DI diesel engine by using TPO/diesel blends. The authors reported that the HC, CO, SO 2 and smoke emissions usually increased and NO X emissions decreased with the increasing tyre derived fuel content in the diesel blends. In addition, the engine output power and torque decreased while the brake specific fuel consumption increased with the increasing tyre derived fuel content in the diesel blends [8]. The present investigation is aimed to study the effect of blending TPO in lower percentages with JME in a CI engine. For the investigation, a naturally aspirated, single cylinder, 4- stroke, air cooled, DI stationary diesel engine is used. Four different blends JMETPO5, JMETPO10, JMETPO15 and JMETPO20, of TPO_varying from 5 to 20% with a regular interval of 5% in the blends were used as fuels. The numeric values after JMETPO indicate the percentage of TPO in the blend. MATERIALS AND METHODS Biodiesel Production For the present investigation JME was collected from a commercial biodiesel plant that produces the methyl ester through the transesterification process. Jatropha oil consists of a series of saturated and unsaturated monocarboxylic acids as glycerides. Jatropha oil has four major groups of fatty acids, which are oleic acid, linoleic acid, palmitic acid and stearic acid. Those major fatty acids can be transesterified to fatty esters in the presence of alcohol. Transesterification is the most common method for biodiesel production due to its simplicity. Figure 1. Inputs and outputs of the transesterification unit process
In the transesterification process, Jatropha oil requires modification with the input ratios of the alcohol reagent and reaction catalyst, as well as alterations to the reaction temperature and time, in order to reach optimal biodiesel production results. The optimal inputs for the transesterification of Jatropha oil are identified to be 20% methanol (by mass on oil basis), and 1.0% NaOH (by mass on oil basis). The maximum ester yield is achieved after 90min reaction time at 60 C [9-10]. Table 1. Composition of Jatropha oil Pyrolysis Process The automobile tyre was cut into a number of pieces and the bead, steel wires and fabrics were removed. The thick rubber at the periphery of the tyre was alone made into small chips. The tyre chips were washed, dried and fed into the pyrolysis reactor unit. The pyrolysis reactor used was a fully insulated chamber. An inert environment was created in the pyrolysis reactor by supplying nitrogen from a cylinder, and then externally heated by means of a 7kW heater. A temperature controller was used to control the temperature of the reactor. Pyrolysis was performed at a temperature of 550 C, at which maximum yield of oil was obtained. The products of pyrolysis in the form of vapour were sent to a water cooled condenser, and the condensed liquid was collected as pyrolytic oil. The oil was drained through the outlet of the oil collection tank. The non-condensable gases were collected in a gas bag, weighed, and then released to atmosphere. The TPO collected was crude in nature. Approximate yields from the process were 50 %wt TPO, 40 wt% gases and 10 wt% char [11]. Comparison of Fuel Properties The physical properties of JME and crude TPO are compared with those of diesel and given in Table 2. Table 3 gives the comparison of the physical properties of JMETPO blends. Table 2. Properties of diesel, Jatropha methyl ester and crude TPO Table 3. Physical properties of JMETPO blends EXPERIMENTAL SETUP Experiments have been conducted in a single cylinder, four stroke, air cooled, direct injection, diesel engine, with a developing power of 4.4kW at 1500 rpm. Figure 2 shows the schematic diagram of the experimental set up, and Table 4 gives the technical specifications of the engine used in this study. The blends were measured on volume basis and kept in different collecting tanks. The blend was kept for an observation for thirty days to check its stability. It was observed, that the TPO is miscible with the JME and the blend was stable during the period of observation. Table 4. Engine specifications Experiments were initially started with diesel and after the engine's warm up condition, it was switched over to JME, and then the different JMETPO blends. A fuel level indicator is used for measuring the total fuel consumption. A U tube manometer was used for measuring the intake air flow rate. A K-type thermocouple was installed to measure the exhaust gas temperature. The exhaust emissions of the engine were measured by an AVL DiGas444 exhaust gas analyser. An AVL437 smoke meter was used to measure the smoke emission. For each load, the engine was run for 30 minutes. Once the experiment was complete, then the test fuel was drained, from the fuel line. The engine was further run with diesel for 30 minutes to remove the strains of JMETPO blend. After this the engine was tested with the next blend.
Figure 2. Schematic diagram of experimental setup PERFORMANCE PARAMETERS The performance parameters, such as brake thermal efficiency, brake specific energy consumption (BSEC) and exhaust gas temperatures (EGT) of the JMETPO blends are compared with those of diesel and discussed below. Brake Thermal Efficiency Figure 3 portrays the variation of the brake thermal efficiency with brake power for diesel, JME and JMETPO blends. JBTPO15 and JMETPO20 is 29.40, 29.87, 29.88 and 29.88% respectively, at full load. However, all the JMETPO blends have a thermal efficiency slightly lesser than that of diesel. This may be due to the lower calorific value of the JMETPO blends. The poor atomization of the blend droplet, as a result of the higher viscosity of the JMETPO blends, may also be one of the reasons for lower brake thermal efficiency than that of diesel operation [12]. Brake Specific Energy Consumption (BSEC) The brake specific fuel consumption is not a very reliable factor to compare the two fuels as the calorific value and the density of the blends are different from those of diesel [13]. Figure 3. Variation of brake thermal efficiency with brake power The brake thermal efficiency of the engine increases with an increase in the brake power for diesel and the JMETPO blends, as expected. The brake thermal efficiency for diesel and JME at full load is found to be 29.89 and 28.61%. The brake thermal efficiency for JMETPO5, JMETPO10, Figure 4. Variation of BSEC with brake power
Figure 4 shows the variation of the BSEC for diesel, JME and the JMETPO blends. The BSEC for diesel is 11.86 MJ/kWh, while for JME is 12.55 MJ/kWh at full load. As the blends contain JME and TPO as a constituent, this reduces the net calorific value and hence, the BSEC also varies accordingly. All the JMETPO blends exhibit higher BSEC than that of diesel, as a result of a lower calorific value. The values of BSEC for JMETPO5, JMETPO10, JMETPO15 and JMETPO20 are found to be 12.24, 12.67, 11.92 and 12.67 MJ/kWh respectively at full load. Exhaust Gas Temperature (EGT) Figure 5 shows the variation of the exhaust gas temperature with respect to brake power. It shows that the EGT increased with an increase in the brake power for all the fuels tested in this study. For diesel and JME, at full load condition, the EGT are 303 and 329 C. At full load, the values of EGT are 318, 297, 330 and 325 C for JMETPO5, JMETPO10, JMETPO15 and JMETPO20 respectively. The EGT values are higher for the JMETPO blends. Figure 6. Variation of carbon monoxide with brake power It is apparent from the figure that the CO emission from the JMETPO blends is lower than that of diesel. The excess oxygen present in the JME is helpful for the complete combustion, and hence the amount of CO emission is less [15]. Hydrocarbon (HC) Emission The values of HC emission from a diesel engine in the case of JMETPO blends is less than those of diesel as is evident from Figure 7. Figure 5. Variation of exhaust gas temperature with brake power Poor volatility and high viscosity are the reasons for the higher exhaust gas temperature of the JMETPO blends [14]. EMISSION PARAMETERS Emissions such as carbon monoxide, unburnt hydrocarbon, nitric oxide and smoke opacity for diesel, JME and the JMETPO blends are discussed in the subsequent sections. Carbon Monoxide (CO) Emission Figure 6 illustrates the CO emission for diesel, JME and the JMETPO blends with respect to brake power. The CO emission in a CI engine is due to less oxygen availability and poor mixture formation, as the CI engine is operated with a lean mixture. Figure 7. Variation of hydrocarbon with brake power Hydrocarbon emission is mainly due to incomplete combustion. The HC emissions increase with increasing the load for all the fuels tested. The HC emissions for diesel and JME at full load are 18 and 23 ppm. At full load, the HC emissions are 18 ppm, 19 ppm, 20 ppm and 21 ppm for JMETP05, JMETPO10, JMETPO15 and JMETPO20 respectively. The reduction in the HC emission is mainly due to the result of improved combustion with the JMETPO blends, as JME is oxygenated fuel [16].
Nitric Oxide (NO) Emission Figure 8 shows the variation of NO emission with brake power for the fuels tested. The NO emission is highly dependent on the temperature and availability of oxygen inside the cylinder [17]. As the load increases the temperature inside the cylinder also increases. At full load, the NO emissions are 452, 614, 612, 589, 574, and 564 ppm for diesel, JME, JMETPO5, JMETPO10, JMETPO15 and JMETPO20 respectively. complete combustion. But, as the percentage of the TPO increases in blend, the aromatic content and carbon/ hydrogen ratio also increases and this results in higher smoke with increasing TPO in the blends. [18]. Smoke opacity for diesel at full load is 86.3%. At full load the smoke opacity values are 52.2, 53.5, 56.2, 58.6, and 63.1% for JME, JMETPO5, JMETPO10, JMETPO15 and JMETPO20 respectively. CONCLUSION In the present investigation, experiments were conducted in a single cylinder, 4 stroke, air cooled, and DI diesel engine with JMETPO5, JMETPO10, JMETPO15 and JMETPO20. The conclusions of the investigation are summarized and given below. The engine works smoothly with the JMETPO blends and exhibits similar performance and lower HC, CO, smoke emission, but higher NO emission compared to that of diesel. JMETPO15 gives the optimal result compared to the other JMETPO blends. Figure 8. Variation of nitric oxide with brake power The NO emission is found to be higher for all the JMETPO blends compared to that of diesel, but lower than JME. The reason for lower NO emission with JMETPO blends than JME are due to the increase in aromatic contents of the blends. Smoke Opacity The brake thermal efficiency of JMETPO15 is almost the same as that of diesel at full load. The BSEC for JMETPO15 is 11.92MJ/kWh and for diesel 11.86MJ/kWh at full load. The BSEC increases by about 0.05% with JMETPO15. The EGT is higher for JMETPO15 compared to that of diesel at full load. Carbon monoxide is decreased by about 11.36% for JMETPO15 compared to that of diesel, at full load. The NO emission is increased by about 27% for JMETPO15, compared to diesel, at full load. Figure 9. Variation of smoke opacity with brake power Figure 9 shows the variation in the smoke opacity with brake power for the different tested fuels. Smoke opacity increases with an increase in the brake power for all the tested fuels, and is lower for the JMETPO blends compared to that of diesel. This reduction is due to the absence of sulphur and presence of oxygen in JME, which plays a vital role in Smoke opacity is lowered by about 32% for JMETPO15 compared to that of diesel, at full load. REFERENCES 1. Asakuma, Y., Maeda, K., Kuramochi, H. and Fukui, K., Theoretical Study of the Transesterification of Triglycerides to Biodiesel, Fuel 88:786-791, 2009. 2. Fang, H. and McCormick, R., Spectroscopic Study of Biodiesel Degradation Pathways, SAE Technical Paper 2006-01-3300, 2006, doi: 10.4271/2006-01-3300. 3. Searchinger, T., Heimlich, R., Houghton R. A., Dong F., et al. Use of U.S. Croplands for Biofuels Increases Greenhouse Gases Through Emissions from Land-Use Change, Science 319 (5867): 1238-1240, doi: 10.1126/ science.1151861. 4. Glkılıç, C. and Aydin, H., Fuel Production from Waste Vehicle Tyres by Catalytic Pyrolysis and its Application in a
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