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Understanding Extraction and Other Processing Steps in Re-Refined Base Oil Production

Understanding Extraction and Other Processing Steps in Re-Refined Base Oil Production

Dec 11, 2023
Posted by David Price, Engine Oils Product Manager

This is the second of three articles in a series about re-refined base oil’s place in the passenger car and heavy-duty vehicle market.

Re-refining base oil from used engine oil is a concept that has been around for many years and for which demand is growing globally. One selling point for RRBO is that re-refined base oils are a way to make use of some of the millions of litres of used engine oil that are otherwise disposed of in the ground or through combustion each year. Another advantage of RRBO is that it is a reusable resource; every litre of RRBO in use offsets the amount of virgin base oil needed in machines and vehicles. While the advantages seem clear, production of RRBO is more complicated than the process for virgin base oil. RRBO is not simply reclaimed and recycled engine oil. Getting RRBO to a level of quality needed for use in most passenger car and heavy-duty vehicle engines involves the removal of water, additives, dirt and other materials through a multi-step process.

Common RRBO terms and processes

In this article, we’ll discuss some of common terms and processes used in RRBO production. Because no single technique is considered the standard for RRBO processing, the list below describes the variety of steps in a typical RRBO process.

Vacuum distillation: In simple terms, distillation involves the use of heat to force the separation of substances. That’s the goal of distillation for RRBO as well. The “vacuum” in vacuum distillation in RRBO involves the use of a vacuum to allow the used engine oil to reach a boiling point at a lower temperature, enabling it to be pulled away from other materials for further processing. The heavy materials that separate away from the base oil during vacuum distillation are put to use in products like asphalt extenders.

Dehydration: Water is present in stored used engine oil for a variety of reasons and must be removed. It’s a fairly straightforward process, though. Evaporation through heating the used engine oil removes the water.

Hydrotreating: In hydrotreatment, hydrogen is used to cause a chemical reaction, which impacts the color and other qualities of the final product.

Solvent Extraction: The most common strategy for removing additives is through solvent extraction, most often a liquid solvent. Sulfur dioxide is one example of a chemical used in solvent extraction, but other chemicals typically used in other refining processes, like phenol and fufural, are also used depending on the type of compounds being removed.

Re-Refined Base Oil in the marketplace

As demand for re-refined base oil grows, especially in countries with government regulations requiring a percentage of RRBO in all engine oils, the pressure to produce RRBO products that meets modern vehicle standards is increasing. At the moment, RRBO is not able to be purified to the point that it matches virgin base oil, but the percentage of RRBO in engine oils is likely to grow as processes evolve.

Read the first article in the RRBO series:

Re-Refined Base Oil for Use in Passenger Cars and Heavy-Duty Vehicles

Next in the series: Re-Refined Base Oil Market Capacity

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