Biopowered - vegetable oil and biodiesel forum
Biodiesel => Chemistry and process => Topic started by: Tony on November 30, 2014, 05:31:09 PM
-
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.
-
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.
-
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.
-
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.
-
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.
-
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?
-
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.
-
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 :)
-
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.
-
Only tried potassium once but as I demeth and settle found that the soap can take weeks to drop.
-
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 :)
-
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.
-
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 :)
-
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!
-
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.
-
when I tried KOH first time after years of using NaOH I didn't like the longer settling times so as soon as the bag was used I went back to NaOH, I've been given a few half bags of KOH over the years and I just mixed em in a bit at a time with the NaOH.
-
The bubbled one hasn't set to jelly on cooling, so I'm quietly hopeful. Still wondering where all the glyc went, might find it at the bottom of the settle drum after a couple of weeks - or it could turn out to be one of those awkward ones that never settles.
-
Not convinced on this whole KOH thing, doing another batch this time with a mix of nice oil and some whites, and still it needs to be three-staged to reach completion despite using excess KOH. At least NaOH has enough "poke" to get the job done easily.
-
For a while, i was using sodium on stage one, and then potassium on stage two.
That, for me, worked well - cheaper sodium for the start, then more expensive potassium, to keep the s2 glycerol liquid for the next glyc wash. S2 glycerol always seems cleaner too (which is another reason why i like to use it for the glyc wash)
...but i seem to recall, you dont glyc wash, so that would be of no benefit for you anyhow.
-
I've done some glyc washing now I've got liquid glycerol.
I'm starting to dislike KOH though. I keep having issues where stage 1 won't drop, and adding extra methanol doesn't help but extra catalyst does. But I end up using a ridiculous amount of catalyst, far in excess of what is needed for converting the whole batch, and only getting 80% converted (even with plenty of meth present). So I keep having to three stage to get to a clear pass on the 3/27.
I don't understand why KOH is not converting properly for me. I know the meth is OK a) because it was working fine with NaOH and b) because it measures 100% on the hydrometer.
I even thought the pump was underperforming on the mixing (I've been using an 80lpm Pedrollo) which I've swapped out for one of the multistage Calpedas (what a transformation that makes to venturi sucking, but I digress) and that hasn't helped. I'm at bit of a loss.
-
Tony...Uncle H (Chad) is having the very same issues as you. He's about to go back to my ASM now. He's also at a loss as to why he's using so much.
-
Hi all I only use koh very rarely use more than 1kg for 100litres I do only use rapeseed oil never use whites or gung I do a 2stage make in morning drop glyc next day then move to settling tank then dry wash week later
-
I did a WBD on the current 80% batch to see how much excess Methanol was in it, and only got 1l of Methanol back up to 90C - so perhaps stalled due to lack of Methanol rather than the catalyst. Odd, because it had a good 20l of Meth in my 125l batch (16%). But after WBD I've yet to do another 3/27 to see if more conversion took place.
-
Well I got 40l glyc from my 125l batch, add water to it and it instantly turns solid. This is like my early days of brewing again ::)
-
Finally a good batch, two staged successfully.
I'm just not using enough Methanol in stage one. It seems the whole stage one Methanol stall technique doesn't play nicely with KOH, I have to add a bit more to get the glyc to drop. Got a nice clear pass yesterday, didn't use foolish amounts of KOH and got a better yield too. Not bad considering the oil was like lumpy icecream in consistency.