1) All oils and liquids containing oils delivered to our processes by tank trucks, tank wagons, vessels or oil-tankers are subject to a quality analysis on receipt corresponding with the Ordinance on Oil. Only separatly collected qualities of oil are used for lubricant recycling. Only these types guarantee ecological closed loop upcycling in terms of resource preservation. All other qualities can only be used for down-cycling to flux oils and heavy oils. (2) Depending on the above mentioned, the oils and liquids containing oils are deposited in various storage tanks. Then, according to their purpose, they are reworked in the different processing lines. The most important and complex processing line for us is the manufacture of base oil, the basis of the lubricant production which follows it. In the recycling of base oil the used oil runs through several stages of processing. (3) Dehydration of the oils is achieved by atmospheric distillation or under a partial vacuum. The purpose of the plant is to separate water and low-volatile hydrocarbon fractions (e.g. naphtha) from the used oil down to a residual content of about 0.1 – 0.2 wt./% by distillation. (4) The dehydrated oil is now fed into a flash distillation unit. In a first stage of distillation gasoil fractions are separated and sorted out. In the following stages the desired raw distillate is manufactured. These raw distillates contain hydrocarbon chains in the distillation range from about 320°C up to 540°C. The distillation residues which also occur in the flash distillation unit represent bottom product. They in contain essentially the additives originally used in the oil, together with sooty particles and heavy metals. To manufacture the base oil fractions demanded by the market, the raw distillate recovered is then fed into a fractionating plant, where the desired viscosities are produced. In our process, we limit ourselves to producing three different viscosity grades of the base oil starting fractions. (5) In order to remove the remaining undesirable residues in the base oil starting fractions (e.g. polycyclic aromatic hydrocarbons [PAHs], particles of dirt or unstable organic compounds), these are treated with a suitable solvent in a liquid-liquid extraction plant. The base oil freed of all residual impurities now forms the raffinate phase, together with a small proportion of solvent. The solvent containing the impurities forms the extract phase. Both the raffinate and the extract phases are now separated from the solvent in the following distillation units. Thus completely recovered, the solvent can now once again be fed back into the extraction process. The raffinate or Kernsolvat® thus recovered is now stored in the tank-farm and can be sold directly as high-quality base oil or be further processed in our own blending and filling plant for diverse lubrication applications (e.g. motor oils, hydraulic oils, gearbox oils, industrial lubricants etc.), The extract, which occurs at an average rate of 9%, can either be sold as a heating oil ingredient or used in our own steam generating plant. The innovative feature of the extraction technology developed by the Mineralöl-Raffinerie Dollbergen GmbH is that it works without producing any waste and in an environmentally-friendly manner and preserves resources. |
