KOH glyc not dropping

[Tony]

Background - nasty creamy oil, heated to 105C and got about 8l of water out of 130l of oil.

Did a KOH glyc wash (first time for everything) and what came out was about the volume I put in but a lot thicker.

In went 15l Meth and 1.275kg KOH.

Mixed for an hour but on standing, nothing drops!  3/27 shows roughly 50% conversion.

Any advice?

I've dumped in another 5l meth and 425g KOH (a little under 7g base for 50% unconverted) and that's mixing now.

[Julian]

I had a several batches that did exactly the same a little while back ... never worked out why, and I was using a much higher percentage of  methanol than you are.

My solution (which seems to cure most problems) was exactly what you've done ... whack more catalyst in.

[Manfred]

I can't really give advise to someone with your experience as I've  only had a stage 2 not drop,but I added stage 1 back and that did the trick for me.
It looks as though the oil sucked some meth out of the glyc wash though. Be interesting to see what comes out after the 2nd stage.

[julianf]

I had one some time back.  I tried more chem, but that did not work.

In the end, i canned it, and have been feeding into subsequent batches (1/3 failed to 2/3 good oil) prior to the glyc wash stage.  And then dosing for the oil only (not the failed part)

Has been going ok.  But, be aware, if you can it, it will go to jelly when it cools.

[Tony]

Well the extra meth and KOH did the trick, the glyc is dropping like it's hawt.

Unfortunately not much more than the 50% converted, it seems the creamier/lumpier the oil, the more work it creates for me to convert it.  I've had to three stage a few batches recently with the oil dregs I've been using.

First stage glyc is always a lot thicker and darker than later stages which get progressively lighter.  I can only assume that stage one contains a lot of soap from free fatty acids, and that later stages are lighter soaps (shorter free fatty acid chains?) and glycerol (which should be clear, if it's pure).  It does make sense that shorter fatty acid chains take longer to drop out as the molecular weight must be closer to the liquid in which it is suspended.

The only time I've experienced this before with NaOH has been when water has been involved and as observed above, jelly is in the making.  I could believe that with this batch since so much water came out of it when drying - possibly still a little damp.

[willbuild]

I have also had the same problem with my last few batches, 50 60% conversion, oil comes from fried chicken outlet and am using around 1800 hrs of Kohl for 110 litres of oil. 17% methanol.
I put it down to poor oil. Last batch mixed with 30% better oil and got better results.
On my first 10/90 test I notice a fine dust at the bottom of the flask that I think might be flower?

[Julian]

On my first 10/90 test I notice a fine dust at the bottom of the flask that I think might be flower?

I've experienced that and also suspected flour.  The oil came form an Italian restaurant and the owner confirmed that they fry a lot of calamaris rolled in flour (best calamaris I've had in this country, not the great big tough rings, but whole baby octopus).

The flour settles/filters out of the bio and appears to have no deleterious effect on the process.

[Tony]

Well this batch continues to be a work in progress, I'm loving that with KOH I can just "park" it and leave.  So this morning after sitting or a fw days I've drained the glyc and pumped in some fresh Methoxide to finish it off.  That can now sit until I've got time to pump and heat again for stage three.

I get the impression that KOH doesn't pack the same punch as NaOH when it comes to converting oil.  I know it's only 90% but the quantities should all stack up still.

Ah well, there's a lot to say for liquid glyc

[julianf]

I always breath a sigh of relief, when i drain that first pint glass, after stage one, and hold it up to the light....  and start to see the glyc dropping.

I find that, if you can get past that point, normally the rest of the process is plain sailing.  Normally.

[oakwoodtv]

Only tried potassium once but as I demeth and settle found that the soap can take weeks to drop.

[Tony]

I'm still waiting to see how my first KOH batch turns out, this is only my second one.  I've been using NaOH exclusively since I started years ago (2007/8?), buying 99% NaOH drain cleaner from the local DIY shop

[willbuild]

I also notice with creamy oil batches that once it's fully converted and I do the 7% wash the glycerol drops within 2 hours.
I don't do wbd as at 17% meths on poor oil there's not much meths left to recuperate.

[Tony]

This batch continues to be bizarre.  Stage three now has a clear 3/27 pass having added the extra methoxide and mixed for a bit, but if left to stand no more glyc drops.

So I'm onto demething in case it's excess meth holding glyc in suspension.  But now the pump is making very odd noises and not pushing any pressure.  I suspect cavitation as all the Meth in the mix reaches boil point.

This has become an epic battle between man and biochemistry

[julianf]

IIRC, i had a batch like that once.

Kept dosing, and the 90/10 eventually went clear.

Demeth, and the brew thickened up, somthing started cavitaing or somthing, and it ended up spluttering out of the intake to the venturi.

Most of it ended up on the garage floor.

....where, at least, it set to jelly almost instantly!


I really do wish you better luck than i had!

[Tony]

I'm alarmed that it was 20% unconverted, than apparently totally converted, but no extra glyc recovered.  That in combination with the very unhappy pump noises.

I turned the pump off and just heated the mix to 90C, got 7l of Meth back.

I've not been out yet to see what has happened to the 120l pumped out (tenuously) into the settling drum last night - it only seemed to come out of the pump if I restricted the pump's outlet (I guess this minimises cavitation at the inlet)

I left it bubbling away.  Smells absolutely rank, like something died in it.  I've had batches smell this way before and been fine for fuel, always seems to result from using the nastiest oils.