This is a bit of a new one for me guys. I have some very high titrating oil (55T) and it is being very stubborn about drying out. It actually passes HPT, but there is still a ton of moisture coming off when drying!
This oil first passed HPT early yestarday, I now have an additional 12+ hours dry time and it is still kicking off a lot of steam . My only guess at this time is very high monogylcerides holding the water in and making such small bubbles during HPT that it 'appears' to pass.
Any other guesses out there?
Since passing HPT I now have over 20 hours dry time plus an additional 24 hours bubble drying with heat on. I just refired the fan dryer and am still getting a ton of moisture steam coming off this oil.
My best guess is the high animal fat and monoglyceride content is holding the moisture in solution. I redid HPT this morning with no visable bubbles (same as all other HPT tests).
I have noticed I got steam coming off (I though it was smoke from the oil burning but apparently it is mostly moisture) The bubbles are just too small to see.
Interesting find, and may be another reason why some guys with very high titrating oil/fats are not getting consistent AE results.
Any thoughtd guys?
Acids have slightly higher boiling points than water. 38% HCL, for example, boils at 110degC. that hardly seems like it would explain your problem, but it might contribute a little bit to it.
I wonder if it would help to acid-esterfy the oil first, then dry it. It seems counter-intuitive, but an acid treatment would reduce the pH and FFA's, which might be the source of the water.
What temperature are you drying at?
Acid Esterification as a pretreat wouldn't go anywhere with this much water. H2O is the enemy of the esterification process. Also the FFA's shouldn't be the issue, they don't like absorbing water
The point was to dry the oil and then do the AE, or in my case HTAE. I did finally manage to get it dry, it took 24 hours bubble and 25+ hours fan and element drying to get it done AFTER passing initial HTP. WHEW!
Never had one this stubborn before!
I have seen something similar. I routinely dry my oil by boiling to 120C. As the temperature climbs, you see steam coming off in variable amounts as if there is more than one mechanism binding the water to the oil. Once I left the burner going and the oil went to 130C, with another wave of steam. This stuff is normal mixed UCO usually titrating around 3 or 4. I incline to the notion that the monos or dis bind water more strongly than the tris.
PHO and fats hold water better than clear oil, BD made from them might be similar.
I was surprised how much H2O they held in solution, the oil I work with has very high animal fats and monoglycerides since it comes from grease traps but for some reason this last batch was particularly stubborn at giving up all the water (either that or this is the first time I noticed it still had H2O in solution).
I bet a lot of the issues still seen with AE/HTAE and base have much to do with this 'hidden' water in some of our oil.
When I finally got it dry I had my best AE yet after factoring the very low quantity of methonal used. I think this is something that should be looked at more closesly when people on the forum are having issues with processing.