RE-REFINING
Renewable resource
How re-refining used lubricating oils is making a difference Mark Olpin, Executive Chairman. Slicker Recycling
The second in four-part series from Slicker Recycling, this article illustrates the scope and workings of the used lubricants re-refining sector, the challenges if it is to do more, and why the wider industry should work closely to make an even greater contribution to sustainability.
In this article we look at the challenges that a re-refiner faces focusing on processing options to deliver high quality products with a low impact on the carbon cycle.
The Base oil processing dimension and re-refining challenge
In the first article we highlighted the importance of collecting used lubricating oils (ULO) at sufficient scale and quality to act as feedstock for a modern base oil re-refinery. In addressing processing options for a virgin or re-refined base oil then the overarching need is to deliver a required performance standard. With few exceptions re-refiners aim to emulate or surpass the comparative standards of virgin base oils to gain market acceptance and overcome any perception often seen as second best.
Comparing conventional base oil processing with that of re-refining
By understanding conventional base oil processing options, a re-refiner can decide what treatments might best address the challenge of recovering from a waste oil merchantable qualities of base oil for reuse.
A range of viscosities is probably the single biggest driver of base oil selection relying on good fractionation helping to control volatility, but it is also
evident that oxidative and thermal stability properties of the output are critical parameters delivering performance. Over time experienced refiners have skilfully learned how to selectively partition feedstocks and then remove a range of unwanted complex hydrocarbons including, reactive sulphur and nitrogen and waxy components.
Processing options have evolved from now redundant acid refining of selected hydrocarbon streams to the use of various organic solvents to remove undesirable species, a step that is often followed by chilled solvent dewaxing to improve the oils low temperature properties. It was also not uncommon to see the growing use of a final light hydrogen treatment to remove traces of polar materials, sometimes referred to as ‘polishing’. As these oils were acid-free, they commonly became known as solvent neutral oils and are still widely used.
In the 1970s, refiners were developing new hydrogen- based catalytic processes to obtain more fuel from hard to process crudes and that technology was being Continued on page 12
LUBE MAGAZINE NO.177 OCTOBER 2023 11
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