I believe the solution is vacuum distillation. This may also produce oil that is suitable to use in the crankcase.
It’s also worth considering .5-micron filtering. I know this won’t remove additives, and I’m not sure these are the problem, but I certainly get a reduction of ash, in my waste oil burner, if I filter finer.
Using wmo as a fuel is too good to reject without further testing.
What sort of burner do you have? and how much black carbon or white ash or both do you get?
As what you see will help others under stand what's happening to WMO when it's burnt.
I use a Kroll and it needs wmo filtered to 100 micron. It produces white ash and only black ash/soot when the baffles need cleaning (lack of oxygen flow).
I used to filter the wmo to 100 micron but now go down to 50. I have experimented with 20 micron and each reduction has reduced the ash production.
Ash in the burner box is not a problem, I just vacuum it out every few months, but I’m wondering if .5 micron filtering would greatly reduce the ash problem in engines.
What micron have you been filtering to? Sock filters or cartridge?
Now image the ash and carbon that you clean out all going through an engine.
The white ash is the oil additives and you are seeing them every where.
These additives burn and can not be left behind by evaporating as they evaporate with the oil it's self.
It's the white ash that is abrasive and doing the damage, you can not filter out additives.
The white ash I get in the burner is from 50-micron oil. I would expect this ash as the oil obviously still contains a high percentage of non-oil particles.
20-micron oil produces less ash, so I would suggest this is showing that the ash is coming from non-oils that can be filtered out.
Wmo that is intended for use as an engine fuel would be filtered to .5 micron so should contain a much lower percentage of non-oils.
If you have been filtering to 5 micron with a filter bag, or even 1 micron with a low-grade cartridge filter, this may explain the quantity of ash your fuel is producing.
As far as I know, companies that produce ‘new’ engine oil from wmo use the distillation process. One would presume this does not contain abrasives?
It’s important to look on the positive side. Experimenters never fail, they only learn things!