Technology for rerefining used lube oils applied in Europe: A review

The European oil rerefining industry is comprised of 28 plants treating waste oil, which represent one-third in volume of the total European market for lubricants. The biggest European rerefineries with capacity greater than 40 000 tons/year apply various technologies for recycling of used oils from different sources. Used oil recycling technology has undergone significant changes over the past decade. With the newly developed rerefining technologies it is possible to produce higher quality base oil compared with the traditional and old acid clay methods. Currently in Europe the following re-refining methods are widely used: solvent extraction (N-methyl-2-pyrrolidone (Germany), Interline process (United Kingdom, Spain)); combined vacuum distillation and solvent extraction (Vaxon process (Denmark, Spain); hydroprocessing (Hylube process (Germany)); combined thin film evaporation and hydrofinishing (CEP process (Finland)); combined thermal de-asphalting and hydrofinishing (Revivoil process (Italy, Poland, and Spain)). The majority of applied technologies in Europe is appropriate for rerefining of synthetic lubricating oils, which currently are replacing the conventional mineral lube oils due to their enhanced performance characteristics. However, for the rerefining technologies applying alkaline treatment (CEP, Vaxon) and hydrofinishing step (Cyclon, Snamprogetti, Revivoil) the amount of synthetic or semi-synthetic oils based on esters in the feedstock should be eliminated, since these oils are less stable under alkali and hydrofinishing conditions.