PRODUCTION AND UTILIZATION OF LIQUID FUEL DERIVED FROM WASTE PLASTIC IN A AGRICULTURE DIESEL ENGINE

Abstract

Waste plastic disposal and excessive use of fossil fuels have caused environment concerns in the world. Both plastics and petroleum derived fuels are hydrocarbons that contain the elements of carbon and hydrogen. The difference between them is that plastic molecules have longer carbon chains than those in LPG, petrol, and diesel fuels. Therefore, it is possible to convert waste plastic into fuels. The pyrolysis reaction consists of three progressive steps: initiation, propagation, and termination. Initiation reaction cracks the large polymer molecules into free radicals. The free radicals and the molecular species can be further cracked into smaller radicals and molecules during the propagation reactions. At last, the radicals will combine together into stable molecules, which are termination reactions. The activation energy and the energy requirement for the pyrolysis are dependent on the reaction process and the distribution of the final products. Following the equations from the literatures, the theoretical energy requirement to pyrolyze 1kg PE is 1.047 MJ. The measured calorific value of the product obtained is 45.3 MJ/kg. Therefore, the energy profit is very high for this process. The main objectives of this study were to understand the processes of plastic pyrolysis for maximizing the diesel range products and to test the fuel obtained in an agriculture diesel engine. Pyrolysis of polyethylene (PE) has been investigated experimentally in a lab-scale pyrolysis reactor. The key factors have been investigated and identified. A batch reactor type pyrolysis reactor is designed and liquid fuel is obtained from the waste plastic particularly. Feed Material used is low density polyethylene that is generally polythene bags and plastic cups. The performance and emission characteristic of agriculture engine is also investigated running on plastic pyrolysis oil and compared it with diesel fuel. The plastic was cracked thermally at temperature range of 500ºC to 600ºC. The products obtained were of different composition and the product yield was different for different temperatures. The liquid product obtained had a specific gravity of 0.7787, kinematic viscosity of 1.6 and calorific value of 45.3 MJ, which is quite good and falls in the range of diesel fuel. These properties do also match with the gasoline range fuels but the flash point is very high. Thus the plastic pyrolysis oil was tested only in the diesel engine. vi The engine was able to operate stably on plastic pyrolysis oil at different engine rpm and load. The engine brake thermal efficiency was lower for 100 % plastic pyrolysis oil comparison to diesel. All measured emissions (NOx, UHC, CO and CO2) were higher for plastic pyrolysis oil compared to diesel, however if we use blends of plastic pyrolysis oil and diesel then emissions could be controlled.