After the feed stream dehydration step, the lighter fractions are separated in flash vessels. The heavy fraction is heated and sent to wiped film evaporators under vacuum at ≤0.1Pa and temperatures close to 350ºC, where the deasphalting process occurs. The heavier fraction of the oil, containing a major part of the contaminants and degraded oil, is
Diesel
Gases to burn
Used lubricating oil
Distillation
Spindle oil
Light neutral oil
Grating
Dehydration
To vacuum sytem
Gases to burn
Separation drum
Make-up hydrogen
Fired heater
Hydrotreating reactor
Hydrogen recycle
Recycle gas compressor
Lubricating base oil
Gas scrubber
Purge gas
Figure 6 Basic arrangement for a hydrotreating process for re-refining of used lubricating oil
relatively high and is only attractive for process plants with large capacity. Some researchers have devoted efforts to developing new re-refining technologies for treating used lubricating oils, and some of these technologies, such as ultrafiltration using membranes, have shown promise, but they are still in an initial stage of development. In Brazil, close to 40% of lubricating oil consumption is recovered and sent to processing by re-refiners (Brazilian Petroleum Agency (ANP), 2025) . Currently in Brazil, most of the production of lubricating oils is for Group I and II oils. Two Brazilian refineries use the solvent route for re-refining, while a third is able to produce naphthenic lubricating oils for specific applications, such as isolators used in electrical equipment. Conclusion The drivers to reduce the carbon intensity of the energy industry and improve overall energy security create a great trade-off for the crude oil refining industry. In this context, re-refining used lubricating oil offers a good circularity strategy for refiners. The Brazilian case shows that synergy between regulations, robust infrastructure, and effective reverse logistics can deliver excellent results to reduce the carbon intensity of the refining sector. VIEW REFERENCES Marcio Wagner Da Silva marciows@petrobras.com.br
removed as neutral sludge, which can be directed to the asphalt industry. After the deasphalting process, the used oil is treated with sulphuric acid (sulphonation) to remove remaining contaminants from the base lube oil. The wiped film evaporator process reduces acid sludge production and has a lower environmental impact than the acid-clay process. However, the base oil produced by this route only meets the Group I specifications. Some re-refiners apply a propane deasphalting process to replace the wiped film evaporators. However, the necessity of constant solvent replacement and additional HSSE requirements from handling solvent can increase operational costs, although the capital investment is similar for both technologies. As with virgin lube oils, the production of higher-quality base lubricating oils (Group II-IV) from waste oils requires hydrotreatment. Figure 6 presents a basic process flow for used lubricating oil re-refining via the hydrorefining route. After the dehydration step, the used oil passes through a distillation column where the lube oil is separated from the lighter fractions. The bottom product of the distillation column is mixed with hydrogen and preheated. The process is conducted under mild conditions with temperatures ranging from 250 to 300ºC and pressures close to 30 bar, using a cobalt/ molybdenum catalyst on an aluminium oxide carrier. The clear advantages of the hydrorefining route are the higher quality of the base lubricating oil and a reduction in the environmental footprint. However, the necessary capital investment is
www.decarbonisationtechnology.com
47
Powered by FlippingBook