Used Oil Re-Refining Technologies Comparison: Selecting the Right Process for High-Quality Base Oil

It is important to use appropriate technologies for refining used oil to obtain quality base oil. The technologies differ by their separation and purification efficiency, which makes the selection of the appropriate one a critical step.

When selecting equipment and technologies for the processes, one should not take into account their effectiveness alone; rather, one should evaluate them in regard to their suitability to the feedstock, the quality of the required base oil, processing volume, and the process as a whole.

For a broader overview of the used oil re-refining process, including its main treatment stages, read our comprehensive guide.

What Makes Re-Refining Technologies Different?

The re-refining of used oils has two basic goals, which include oil fractioning and base oil upgrading.

The separation technologies like vacuum distillation and thin film evaporation are mainly used for the removal of unwanted impurities and the isolation of the good oil fractions. The purification technologies like solvent extraction, hydrotreating, and adsorption aim at improving particular properties of the oil fraction.

Sometimes these technologies do not replace each other directly, as they have their own functions, while sometimes they can be regarded as alternative approaches to solving the same problems.

Comparison of Key Re-Refining Technologies

It is in these aspects that the main distinctions can be seen when comparing the different re-refining technologies.

Technology	Primary role	When to consider it	Main selection factor
Vacuum distillation	Oil fraction separation	As a core separation stage	Separation efficiency and thermal control
Thin-film or wiped-film evaporation	Separation with short thermal residence time	For suitable high-boiling or heat-sensitive streams	Feed characteristics and equipment requirements
Solvent extraction	Selective removal of unwanted compounds	When additional purification is required	Solvent recovery and target oil properties
Hydrotreating or hydrofinishing	Improvement of chemical quality and stability	When higher product specifications are required	Hydrogen availability, investment, and operating requirements
Adsorption or clay treatment	Removal of selected impurities and color bodies	When additional polishing is needed	Treatment effectiveness and spent adsorbent handling

The results make it clear why there cannot be an all-encompassing technology to be labeled as the best one for all plants. The right technology will depend on what function the technology performs and how well it is integrated into the entire process.

Which Factors Should Guide Technology Selection?

Quality of Feedstock

The water content, viscosity, additives, oxidation products, and contaminants in used oil are not constant. This means that a technology that works efficiently with relatively stable feedstock might not work well with highly varying feedstock.

It is, therefore, necessary to conduct a feedstock analysis before choosing the right equipment. It will determine the purification needs and avoid wasting resources on unnecessary steps.

Proper feed preparation is an important part of the overall process. Learn more about waste oil pre-treatment technologies and how they prepare used oil for downstream refining.

Quality of Target Base Oil

Specification requirements are amongst the top parameters used in choosing technologies for re-refining process.

Different processes can be needed for base oil that has less strict requirements for the color, quality, stability, or performance compared to more strict conditions for these characteristics.

Instead of adding extra stages of oil treatment, the aim is to meet specification requirements.

Oil Yield and Consistency

A good technology for removing contaminants should also be assessed in respect of the effect on the amount of recovered oil and oil consistency.

Parameters such as operating conditions, the nature of feed stock, and operation of both pre-treatment and post-treatment devices are to be considered.

Operational and Maintenance Needs

There are unique needs that each technology has regarding energy, utilities, materials, maintenance, and process controls. Hydrogen finishing will need to have proper hydrogen handling systems put in place, while solvent-based systems need good solvent management.

This need should be taken into consideration along with product quality and recovery. It is not always the solution that is simplest that wins.

To compare the financial implications of different process configurations, explore our guide to used oil re-refining cost control.

Common Mistakes in Re-Refining Technology Selection

There are several errors that may hinder the operation of a used oil re-refining system.

Selection of the technology solely based on the performance of the equipment: Good performance of each piece of equipment does not imply good performance of the whole facility.

• Neglecting the variability of feedstock: The changes in feedstock can have an effect on separation and purification and also on the quality of the end products.
• Over-processing: Extra processing will not necessarily provide extra quality.
• Neglecting downstream compatibility: Each step should prepare the oil for the next step.
• Assessment of technologies individually: Oil recovery, quality, stability, and maintenance should all be assessed as a whole system.

The above-mentioned structured process of selection enables the operator to avoid such errors.

A Practical Framework for Selecting the Right Technology

Before deciding on a re-refining process, five basic issues need to be addressed:

• What are the major pollutants and properties of the used oil to be processed?
• What are the specifications for the base oil that needs to be produced?
• What separation and purification operations are required to reach the desired specifications?
• What is the impact of each of the technologies considered on recovery, operations, and product uniformity?
• Is the chosen technology capable of functioning reliably within an overall system?

Answering these questions is a starting point for a realistic comparison of different processes. In some cases, further work such as pilot testing of the feedstock and/or product may be needed.

Frequently Asked Questions

• Which used oil re-refining technology is the best?

There is no single best technology. It depends on the quality of feedstock, specifications of the target base oil, recovery required, and the function of each stage of the process.

• Is it possible to combine several used oil re-refining technologies?

Yes. Technologies are usually combined because separation and purification processes have different purposes. The particular combination should fit the feedstock and final product requirements.

• How to avoid unnecessary process complexity?

It is important to determine the specifications of the target product first, analyze the feedstock, and decide which treatment functions are needed. Any new technology added should have its own function and benefits.

The selection of used oil re-refining technologies is mostly a matter of matching the process rather than competing with particular equipment types. Comparing treatment functions, suitability for the feedstock, product requirements, and compatibility will help to create a configuration which ensures high-quality base oil and production reliability.

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