SECTOR FOCUS: RE-REFINING
Re-refining vs recycling waste oils
Dr Srđan Sokolović, Expert for chemicals and waste management, NIS a.d. Novi Sad.
All around the world, lubricants are present in applications where they are used to reduce the friction, heat, and wear between mechanical components that are in contact with each other. Approximately half of total purchased lubricants are lost during use or through leakage, while the other half of purchased lubricants end up as waste oil.
The collection and treatment of waste oil in the EU is defined by Directive (EU) 2018/851 [1] of 30 May 2018 amending Directive 2008/98/EC on waste:
“Any mineral or synthetic lubrication or industrial oils which have become unfit for the use for which they were originally intended, such as used combustion engine oils and gearbox oils, lubricating oils, oils for turbines and hydraulic oils.”
In the same Directive, regeneration (re-refining) of waste oil and recycling of waste are defined as follows [1]: • ‘regeneration of waste oils’ means any recycling operation whereby base oils can be produced by refining waste oils, in particular by removing the contaminants, the oxidation products and the additives contained in such oils;
• ‘recycling’ means any recovery operation by which waste materials are reprocessed into products, materials or substances whether for the original or other purposes.
• According to UK European Union (Withdrawal) Act 2018[2], the Directive (EU) 2018/851 was cut and pasted in UK domestic law, which means that the same definitions of regeneration and recycling are used in UK.
10 LUBE MAGAZINE NO.166 DECEMBER 2021
Generally waste oil could be used as [3]: • Industrial burner oil, where the used oil is dewatered, filtered and demineralised for use in industrial burners;
• Mould oil to help release products from their moulds (e.g. pressed metal products, concrete);
• Bitumen based products; • Re-refined base oil for use as a lubricant, hydraulic or transformer oil.
Recycling of waste oil The processes that are used for recycling [3] are: • Pre-treatment or Dewatering • Filtering & demineralisation.
Pre-treatment or Dewatering In waste oil, there is water which can be found as free phase or as emulsions (bound water) [3]. Dewatering represents the process where free water is removed from waste oil in a separator by gravity. If there is emulsion present, de-emulsifier must be used in order to free water from emulsion. Waste oil mostly free of water [3] is then sent to a tank where it is heated so the rest of the water would evaporate. After this waste oil is sent to go through the process of filtering & demineralisation [3].
Figure 1: Dewatering of waste oil [3]
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