Spent /waste oil is generally denoted as an oil which, due to changed properties, no longer meets the original requirements (e.g. oiliness), and whose characteristics cannot be further enhanced by treatment. Potential sources are spent oils from engines and gearboxes, oily emulsions, bilge water, tank residuals etc. These waste oils have different densities, viscosities and impurity levels.
Waste oils can be treated or refined by means of chemical-physical processes or used as high-grade fuels in the cement industry or in smelters. The waste oil ordinance stipulates the priority of the material treatment of waste oils by means of refining in as far as this does not conflict with technical and economic as well as organizational constraints. The composition of the waste oil as well as the level of contaminants in the waste oil likewise determine the method of disposal.
If the waste oil is to be incinerated, all impurities such as solids and water must be removed beforehand. During incineration, the water content lowers the calorific value. The solids lead to deposits in the boiler, clogging of the nozzles and diminish the thermal efficiency.
Waste oil can be treated by means of mechanical centrifugal technology. Decanters and self-cleaning separators can be used for separating solids and water from waste oil.