Global warming and environmental pollution has intensified our need to recycle our limited natural resources and to extend the lifespan of the manufactured products we use. The lubricants industry is no exception and currently in South Africa most of the used oil collected is recycled into heating fuel. However, internationally especially in the European Union, there is a significant trend in the larger refineries towards re-refining used oil back to base oil.
The European Union’s Waste Directive strongly favours re-refining over burning for energy recovery, and as a result, it is thought that re-refined base oils could meet nearly a quarter of Europe’s base oil demand by 2020.
Used oil processing in South Africa
Bubele Nyiba, the CEO of the ROSE Foundation (Recycling Oil Saves The Environment) explains that in South Africa less than 20% of used oil is re-refined to base oil with most being used as heating fuel.
“The international trend of refining the majority of used oil back to base oil is exciting, but premature for a developing country like South Africa because of the prohibitive cost of the technology and developing the necessary processes.”
Re-Refining vs Recycling
Nyiba explains that the term recycling is very different from re-refining.
“The term ‘recycling used oil’ generally means to take used motor oil and use it for a different purpose, most commonly to be burned as fuel. In the lube oil industry, ‘recycling oil’ or ‘reconditioning oil’ is most commonly referring to using commercial filtration systems to remove insoluble impurities. This method, however, does not remove any of the soluble contaminants. This resulting oil is generally used for fuel and is only good for one-time use. Reconditioned oil is not suitable for use in vehicles.
Re-refining used oil is a process that has been developed over many years. It removes all impurities, both soluble and insoluble, and returns the oil to a quality suitable for use in vehicles. Re-refined oil has quality that is equal to or better than some virgin base oils and motor oils can be re-refined many times.
The used oil refining process explained
Pre-treatment of used oil involves removing any water within the oil by placing it in large settling tanks, which separates the oil and water.
Next the oil is filtered and demineralised to remove any solids, inorganic material and certain additives present in the oil, producing a cleaner burner fuel or feed oil, which can be further refined.
The demineralised oil is filtered to remove suspended fine particles (to solid waste) and run off to storage as a clean burner fuel. It can be further diluted or ‘cut’ with a lighter petroleum product (called cutter stock) to produce light viscosity lubricants suitable for general lubricant applications, low viscosity lubricants for automotive and industrial applications, and high viscosity lubricants for heavy-duty applications. The oil that is produced in this step is referred to as re-refined base oil (RRBL).
Next comes propane de-asphalting to remove the heavier bituminous fractions, producing re-refined base oil. This is an important pre-treatment step in the re-refining process producing de-asphalted lube-oil, which becomes a feedstock for the next step in a re-refining facility. The residue (waste) component is mixed with bottoms from the vacuum distillation tower to produce an asphaltic material.
Following de-asphalting comes distillation to produce re-refined base oil suitable for use as a lubricant, hydraulic or transformer oil. This process is very similar to the process undergone by virgin oil.
The final step is blending additives into the oil to produce final products with the right detergent and anti-friction qualities. Then each product is tested again for quality and purity before being released for sale to the public.