Summary
When processing waste oils into base oils for lubricants, the residual additive components contained in the waste oils and their decomposition products, the unstable mineral oil components modified by oxidation and mechanical shearing, as well as metal abrasion, soot and other solid foreign substances, must be removed after the removal of water and low-boiling components (petrol, solvents, etc.) by distillation.
Previously, the removal of these substances was carried out with sulphuric acid and bleaching earth and subsequent fractional distillation using the so-called sulphuric acid/bleaching earth/hot contact process at SÜDÖL. This process produces relatively high proportions of the problem waste acid resin and oil-laden bleaching earth.
An improvement in the separation of the undesirable interfering components from the waste oil and the recovery of high-quality lubricating oil fractions is now achieved with the aid of a tubular reactor for total evaporation by utilising the different binding energies of the waste oil components. For this purpose, dewatered waste oil is continuously injected into the tubular reactor and evaporated under high vacuum at a tube wall temperature of about 340 °C. At the same time, 1.1 % sodium hydroxide is added in the form of a 50 % aqueous solution to precipitate chlorine compounds and destroy carcinogenic substances. In addition to lubricating oil/gas oil fractions, the tube reactor produces a sump which can be used as flux oil, fuel or bitumen additive. It is currently burnt as fuel.
Results:
- Waste reduction: In the plants downstream of the tubular reactor, the distillate (gas oil and lubricating oil) is treated with only 26 % of the operating materials (sulphuric acid and bleaching earth) compared to the previous process. As a result, only 13 % of the previous problem waste (acid resin and oil-laden bleaching earth) is now produced.
- Economic efficiency: With the tubular reactor process, the processing costs per ton of dry oil are reduced. This helps to make the processing of used oil economically attractive.
