Originally Posted By: JHZR2
Originally Posted By: Nyogtha
Thus far PCMO re-refining has not been sustainable without government requirement. There is some technology involved that is not used in a typical crude oil refinery called thin film evaporation made necessary by the man-made additives added to base oil to make it into a lubricant. Those must be efficiently removed in order to recover and re-refine base stock suitable for blending into a lubricant once again.
Not all recycled PCMO is found suitable for re-refining. A significant portion of used oil collected by Safety Kleen is blended into fuel oil instead of re-refined. History has shown numerous technologies attempted such as feeding used PCMO to cokers to convert to fuels & petrochemicals with significant later coker unit mechanical integrity problems due to the additives in PCMO.
I have yet to see PCMO at retail priced competitively with PCMO made from virgin stocks, whether it be Valvoline Nextgen or Safety Kleen's product that was on Walmart shelves for a while last decade (excluding clearance sales of course). That indicates to me any cost or energy advantage claimed for re-refined PCMO base stock is only being examined with one eye open.
It would be interesting to see the process in detail. I have to wonder if there's a lot of expensive adsorbents or other methods to remove additives. Or, if as you mentioned regarding mechanical integrity, they have to amortize plant equipment faster to cover damages?
Safety-Kleen has a re-refining lube oil process overview for their approach as part of a video on their web site and on youtube. It doesn't show any specialized adsorbents but the man-made additives are permanent poisons for the hydrotreating catalyst. Evidently plain distillation is too violent to reject enough of the man-made additives so thin film evaporation, not a typical step in crude oil refining, is incorporated as a process step. I don't think the capital cost per barrel of throughput is exorbitant on thin film evaporation but perhaps that's the key. I do think thin film evaporation may be significantly more energy intensive per barrel of throughput relative to distillation. Hydrotreating catalyst can undergo several regeneration cycles and be re-used several times if most of the permanent catalyst poisons are removed from the oil before it reaches the catalyst. However each regeneration cycle does some degree of irreparable damage to the catalyst pore structure, so it can't be regenerated indefinitely. This approach thus includes catalyst regeneration costs as well as eventual fresh catalyst purchases and completely spent catalyst metals reclamation and disposal costs. It furthermore requires purchased hydrogen as unlike a typical petroleum refinery there's no integral naphtha reformer or hydrogen plant to generate hydrogen.
There's also a youtube video regarding solvent extraction being used to re-refine used lube oil in Europe, It's shown to use propane as a solvent so it's similar to propane deasphalting technology for a conventional crude oil refinery. No hydrotreating is required of the recovered base oil in this approach. Evidently yields of recovered base stock are similar to Safety Kleen's process.
It would be interesting to see both a capital cost & operating cost comparison for these two technology approaches for the same size re-refinery. Offhand, it would appear proane extraction is a simpler processing scheme with no hydrotreating involved thus no need for hydrogen or catalyst purchases but there isn't really enough detail in either video.
Interestingly, the Yabucoa refinery on Puerto Rico has been converted at least in part for re-refining lube oils from the Caribbean. Sunoco used to produce base oils at that refinery years ago, then it was purchased by Shell around 1991 and run as a more conventional refinery to produce fuels and petrochemical feedstocks, then it was shut down in 2009. They're actually producing their hydrogen electrolytically by cracking water, very energy intensive vs. typical conversion of natural gas and steam to hydrogen and CO2 via steam methane reforming.
http://www.oleinrefinery.com/process-oleinrefinery.html
