Track: Sustainability and Green Systems

Abstract

Large amounts of used lubricating oils are generated from the automotive and process industries and pose environmental hazards if not properly managed. In this study, the potential to re-refine used lubricating oils for reuse was investigated using a combination of vacuum distillation, solvent extraction with additive for maximum performance. Used oils were collected from a local garage and were first dehydrated at 240 °C and varying pressure of 4-12 bars under vacuum distillation. Solvent extraction of the oils was done using Methly Ethly Ketone (MEK) as solvent with varying ratios from 2:1 to 6:1 at mixing temperatures of 60 °C. Afterwards, the MEK and oils mixture underwent atmospheric distillation at 80 °C to allow separation of the oils and the MEK. During the re-refining process, the amount of water removed, the ash content, sulphur content, viscosity, specific gravity, flash point and pour point were measured. Optimum oils yield of 94 (wt %) was achieved at a solvent to oil-ratio of 6:1. Re-refining of the used oils resulted in 73% reduction in the sulphur content, 76% reduction in ash content and 64% water removal. The re-refined oil’s viscosity of 90 cP, flash point of 160 °C, specific gravity of 0.91 and pour point of -12 °C. The re-refined used oils propertied were almost similar to those of the virgin oil. The re-refined oils employing zinc dialkyl dithiosulphate as an additive exhibited physicochemical characteristics similar to the virgin lubricating oils and can be adopted for re-use.