Light and Heavy Phases derived from waste polyethylene by thermal cracking and their usage as fuel in DI diesel engine

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1 198 Journal of Scientific & Industrial Research J SCI IND RES VOL 72 MARCH 2013 Vol. 72, March 2013, pp Light and Heavy Phases derived from waste polyethylene by thermal cracking and their usage as fuel in DI diesel engine Mustafa ÖZCANLI * Çukurova University, Department of Mechanical Engineering, 01330, Adana, Turkey Received 06 February 2012; revised 31 July 2012; accepted 31 December 2012 Recycled fuels have been receiving great attention in order to supply energy recovery especially from waste products. An experimental study was conducted to evaluate the use of fuels produced from waste polyethylene (WPE) as an internal combustion engine fuel. Waste Polyethylene (WPE) was degraded thermally for conversion. The fuel collected at optimum conditions ( C range and 2 h reaction time) was fractionated at different temperatures and fuel property of the fractions was evaluated. The volatile fractions and the residue part of WPE final product are called as light phase (LP) and heavy phase (HP), respectively. Light Phase and Heavy Phase were blended with diesel fuel (D) at the volumetric ratios of 5%, 10%, 15%, %20 and 100%. Fuel properties of plastic oils and their blends with diesel fuel were stated. On the other hand, performance and emission characteristics of 5% waste fuel-diesel fuel were evaluated. The WPE fuels were compared with the diesel fuel. Although the pour points of waste fuels have been concluded as a disadvantage, it is found that they can also be used as recycled-fuel in compression ignition engines by blending them with diesel fuel in order to reduce fossil fuel usage. Keywords: Polyethylene, fuel, cracking, waste, performance Introduction Converting waste products to useful materials is a growing interest in fuel research area. Environmental concerns about wastes can be eliminated by recycling processes. Both in energy recovery and treatment of waste plastics, thermal and catalytic cracking are the well known methods for conversion. Generally, cracking process is defined as splitting macromolecules into smaller parts with the assistance of high temperature. Synthetic polymer based plastics such as polyethylene (PE), polypropylene (PP), polystyrene (PS) and polyvinyl chloride (PVC) are widely used in many important applications such as clothing, household appliances, automotive products and aerospace. Polyethylene (PE) and polypropylene (PP) are the most investigated polymers in the literature 1-9 because more than 55% of all plastic wastes are consisting of these polymers. Diesel engines are the most preferable machines which converts chemical energy of fuel to mechanical energy. Due to the increase in the petroleum prices and *Author for correspondence ozcanli@cu.edu.tr the environmental concerns about exhaust emissions, alternative diesel fuels becoming a famous topic for scientists. Waste plastics have also been used for productions such as supplemental fuel 10 for furnaces and engine fuels Nearby the production of plastic oil from waste polyethylene via the cracking method, performance and emission characteristics were evaluated in this study. Light phase (LP) of waste polyethylene s final product after distillation and the residue part of waste polyethylene called heavy phase (HP) were produced. Then, fuel properties of the products were determined. The extended LP-Diesel and HP-diesel blend ratios (5%, 10%, 15%, 20% and 100%) were prepared for detailed fuel analysis and were compared with the diesel fuel. Finally performance and emission tests were conducted in a four stroke, naturally aspirated, direct injection diesel engine. Experimental Studies The experimental studies were conducted in Petroleum Research and Automotive Engineering Laboratories of the Department of Mechanical Engineering in Cukurova University.

2 MUSTAFA ÖZCANLI: LIGHT & HEAVY PHASES DERIVED FROM WASTE POLYETHYLENE 199 Raw materials Waste polyethylene (WPE) from municipal waste dump were supplied from Turkish local sources and used as a raw material for plastic oil production. Cracking and cracking reactor Plastic oils were produced by thermal cracking method in this study. The cracking reactions were carried out in a special produced cracking reactor which is presented in Figure 1. The main parts of the reactor unit are: the stainless steel cracking reactor body, the plate type heat exchanger for distillation, thermocouple, digital temperature indicator, the manometer and the liquid product receiver. Three heaters gave the possibility to Figure 1 Scheme of cracking reactor control temperature of the supplied feed in the temperature range from o C. As can be seen from the Figure 1, the heaters exist at the external surface of the cracking reactor. Thermal cracking procedures were carried out under atmospheric pressure for 1 hour at around o C temperature ranges. The product was distillated into a receiver and the final product was taken from the receiver for all of the experiments. Waste polyethylene products distillated again and the distillated part which has volatile fractions, are called light phase (LP) for waste polyethylene s final product and the residue part of waste polyethylene is stated as heavy phase (HP). Determination of fuel properties The obtained products were blended with diesel fuel with the volumetric ratio of 5%, 10%, 15%, 20% and 100% and fuel properties of blends were measured. Instruments used for analyzing the product; Zeltex ZX 440 NIR petroleum analyzer with an accuracy of ±0.5 for determining cetane number; ISL CPP 97-2 with an accuracy of ±0.5 o C for pour point; Koehler Saybolt viscosity test for determining the viscosity; Kyoto electronics DA-130 for density measurement and Tanaka flash point control unit FC-7 for flash point determination. Results and Discussion Fuel Properties Properties of Light Phase-Diesel Blended Fuels Light phase has been blended into euro-diesel with various rates (5%, 10%, 15% and 20%) and the blends have been analyzed by the EN standard test methods. Table 1 represents the test results of LP100 and blends. Density and pour point values of LP100 were determined critical. While density value was found out of regulated ranges, pour point value seemed higher than diesel fuel for pure usage at winter climate conditions in Turkey. Because of pour point values, LP5 fuel specifications were found the most similar to Diesel fuel. Table 1-Properties of Light Phase-Euro diesel Blended Fuels Test Fuels Density Cetane Pour Kinematic Flash (g/cm 3 ) number Point ( o C) Viscosity at Point ( o C) 40 o C (mm 2 /s) Euro-Diesel LP LP LP LP LP

3 200 J SCI IND RES VOL 72 MARCH 2013 Table 2 Properties of Heavy Phase-Euro diesel Blended Fuels Test Fuels Density Cetane Pour Kinematic Flash (g/cm 3 ) number Point( o C) Viscosity at Point ( o C) 40 o C (mm 2 /s) Euro-Diesel HP HP HP HP HP Figure 2 Brake power output versus engine speed for LP5 and Diesel Figure 3 Torque output versus engine speed for LP5 and Diesel Properties of Heavy Phase-Diesel Blended Fuels Heavy phase has been blended into euro-diesel with various blended rates (5%, 10%, 15%, 20%) and the blends have been analyzed by the standard EN test methods and results are shown in Table 2. As it is seen in the table, there is no conflict on fuel specification of heavy phase. Similar to LP test results, there is no conflict on using HP-Diesel blends. The pour point value of HP5 was found -16 oc which was strictly similar to Diesel result. For this reason HP5 seemed the most suitable results for engine usage. Performance and Emissions Light Phase (LP) Figure 2 shows the variation of brake power according to different engine speed values. There were no noticeable differences in the engine power output between LP5 and diesel fuel at low engine speeds. The characteristics of power curve were not changed, according to the type of fuel. It was observed that the maximum power values with all fuels were obtained at an engine speed of 2400 rpm. The torque outputs of test fuels are shown in Figure 3. The maximum torque values for diesel and LP5

4 MUSTAFA ÖZCANLI: LIGHT & HEAVY PHASES DERIVED FROM WASTE POLYETHYLENE 201 Figure 4 Brake power output versus engine speed for HP5 and Diesel Figure 5 Torque output versus engine speed for HP5 and Diesel were obtained at an engine speed of rpm. Engine torque outputs of LP5 and diesel fuel were found similar. As the fuels have similar cetane, viscosity and density, parallel results were also expected. The variation of carbon monoxide (CO) and carbon dioxide (CO 2 ) emissions were determined similar for both LP5 blend and Diesel fuel. Although CO values were found a little less (2%) than Diesel there were negligible differences were seen on CO 2 emissions. On an average of 2.01% increment in the nitrogen oxides (NOx) was obtained for LP5 as compared to diesel. Heavy Phase (HP) Figure 4 and Figure 5 show the variation of brake power and torque results according to different engine speed values. There were no noticeable differences in the measured engine power and torque outputs between HP5 and diesel fuel. CO emission results were found 3% decreased according to Diesel fuel results while CO 2 variations of HP5 were similar to Diesel fuel values. The nitrogen oxides (NOx) emissions of test fuels were found 2.76% increased by HP5 as compared to diesel. The reductions in NOx emission could be due to the higher combustion temperature. Conclusions In order to decrease fossil fuel consumption, recycled fuel production and usage were evaluated in this study. Generally, fuel properties of blends were found comparable with those of diesel fuel within the EN standards and they can also be used as fuel in compression ignition engines. Only the pour point values were stated as disadvantages. For this reason LP5 and HP5 are determined as the suitable blends for engine usage related to cold weather conditions and they can be used in diesel engines without any constructive modification.

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