DEVELOPMENT OF A PROCESSING PLANT FOR RECYCLING OF SPENT ENGINE OIL

Abstract

Spent engine oil is typically referred to as used motor oil that has been collected from oil change workshops, garages, and industrial sources such as hydraulics oil, turbine oil, process oil and metal working fluids. In disposing spent engine oil, many people use it as a dust cure; that is, for dust prevention which constitute air and water pollution. This work aims at designing and fabricating a small scale processing plant. Mild steel was used in fabricating majority of parts of the plant. Some components of the plant developed includes; closed heating vessel, frame for holding the vessels, double wall open vessel, settling tank, boiler, gate valve and a 2HP(horsepower) electric motors. The electric motors provided the needed low speed of 100rpm required to drive the stirrer shaft for stirring the mixing oil. Ten litres spent engine oil drum is emptied into the heating vessel made of steel. The closed vessel is directly heated by an industrial heating element at the bottom. The oil is heated up to 170 0C with an intermediate holding at 100 0C to let the water content evaporate. Having reached the temperature of 170 0C the oil is open into the first steel agitator. This open vessel is double walled to allow water to be passed through as cooling agent. The oil is cooled down to 30 0C. At that temperature concentrated sulphuric acid is added at a quantity of 10 percent of the amount of oil (i.e one litre of concentrated sulphuric acid). The mixture is stirred steadily for two hours to let the acid react with the impurities forming sulphates. The oil-acid mixture is afterwards opened into cylindrical steel vessel with a conical shape at the lower end. The clear oil-acid mixture is subsequently open through a gate valve into a second open steel agitator. This agitator is double – walled as well, here for heating purposes. The heating takes place indirectly using steam from a separate boiler. After filling the agitator with the oil-acid mixture (content ten litres approximately 400 g calcium oxide is added). The mixture was heated up to 170 0C while stirring, the whole process last for about three hours so that the calcium oxide will react with the acid neutralizing the oil. At the end of the calcium oxide treatment the content of the agitator is passed through a filter press separating the solids from oil. The clean oil is now stored into a vessel. The amount of clean oil produced after this exercise was about seven litres. The efficiency of the developed spent engine oil recycling plant is 70 %. The test results conducted in the laboratory for kinematics viscosity at 900 for samples of fresh engine oil is 0.40, spent engine oil is 0.15, and recycled spent engine oil is 0.30. This shows that the spent engine oil has lost most of its; viscosity. However, treatment has restored most of these properties. Further processing of recycled spent engine oil will upgrade the product to high quality.