Or better yet, why doesn't it seperate?
I pretreat my oil with the previous batch's glycerine. I add 10 gallons mix 4-6 hours, let it settle for 6-8 hours. Consistently I only get 5 gallons back.
The last batch, I let it settle 24 hours. At the 6 hour mark I had 5 gallons. At 24 hours, I had maybe 5 1/2 gallons.
Needless to say, when I process the batch I wind up with 15 gallons of glyc. So it does come out eventually, just wondering why the 5 gallons stays around on the pretreatment. Binds to WVO better? Any ideas?

Hello Dane

quote:

Originally posted by Dane M. Stewart:
Or better yet, why doesn't it seperate?
I pretreat my oil with the previous batch's glycerine. I add 10 gallons mix 4-6 hours, let it settle for 6-8 hours. Consistently I only get 5 gallons back.
The last batch, I let it settle 24 hours. At the 6 hour mark I had 5 gallons. At 24 hours, I had maybe 5 1/2 gallons.
Needless to say, when I process the batch I wind up with 15 gallons of glyc. So it does come out eventually, just wondering why the 5 gallons stays around on the pretreatment. Binds to WVO better? Any ideas?

Yep, I have a few.
Just curious, are you ever going to demonstrate these sarcastic and funny qualities you claim to have?

"If The Phone Doesn't Ring, It's Me." ~Song title by Jimmy Buffet

If you do a glycerine pretreatment you'll need to let the mixture settle for several days. Some folks let the mixture settle for 3 days then drain the crud and then drain again every day for the next 2 days. Of coarse, you'll need a see-through hose at the bottom of your processor to see when the phase changes, or pull the oil off the top. This all depends on the temperature of the solution. If you try this proceedure in the winter you'll need to wait months before you drain the glycerine.

If you don't get most of the glycerine out of the mixture you will have a sub-standard reaction because the glycerine byproduct contains water and other crud that will dilute the purity of your solution.

BTW, you'll want Tilly to visit any discussions you have if you intend to have any fun at all. He's finally getting his groove back.

Wow! Guys, why wait 2 or more days before dropping out your glycerol pretreatment. Get your WVO up to temp, add glycerol anything up to 100% or more if you want to, mix for a couple of hours, let stand for a couple of hours, (at most) drop out the glycerol, and proceed to process as you would normally do, all the c**p and water will fall out with the initial few litres anyway, and so what if there is still some glycerol left, it will all drop out once the process is completed. 2 or more days! come on! You can finish a 1000 Litre batch in 2 days with ease.
Jim.

Yup. I agree.

Just heat it up and mix for a couple hours then let settle.

Just finished the latest batch.
10 gallons of methanol in, about 14 gallons of glycerine out. But it passed 27/3, looks clear and washing is going fine. Just curious about theories about the ... missing ... glyc. I'll just keep on keeping on.

Dane,

What was your titration before and after the pretreatment? Your results could indicate a high titration. A few days settling may increase the glycerin dropout.

I now run a weekly batch and pretreat the next batch the next day. I let the oil settle for a few days before dumping the glycerin. I have had extremely good yields lately. I think the glycerin continues to drop out over time.

Don't titrate anymore. I have a BP 190, and just add the suggested amounts. When I did, the oil from this was in the 6-7 range and dropped 1 - 2 points. And it is mixed with other sources now that are much lower.

Next time I'll titrate pre and post and see how it does.

Dane M. Stewart's Post:

quote:

Consistently I only get 5 gallons back.

Glycerine does not act the same in WVO as it does in biodiesel. Glycerine can seperate from biodiesel in an hour or 2 but can take several days or more to completely seperate from WVO, depending on temperature. If you have byproduct in your WVO you will need to compensate by adding extra methanol and possibly lye.

Glycerine in your WVO will degrade your reaction.

quote:

If you have byproduct in your WVO you will need to compensate by adding extra methanol and possibly lye.

Not in my experience, in fact quite the opposite is true.
I settle for around 12 hours before draining the glycerin. I measure the caustic based on the original amount of WVO (not the new amount in the reactor)and add l8% methanol when pretreating. When I don't pretreat I need to use 22% methanol.
So the amount of caustic needed goes down as well as the methanol usage and so far the reactions have gone great!
Jon

I'm with John Heron on this-I am getting away with 17.5% methanol-I add NaOH based on original oil volume-Last batch I pre treated 3 times with the last 3 runs worth of by product-mixed for 1 hour each at temp and settled for 1 hour before dropping glyc-made my oil the dryest ever,and gave superb 27/3 result after processing-I'm not going back to wasting 20% methanol(famous last words)

Jon Heron's Post:

quote:

I settle for around 12 hours before draining the glycerin. I measure the caustic based on the original amount of WVO (not the new amount in the reactor)and add l8% methanol when pretreating. When I don't pretreat I need to use 22% methanol.
So the amount of caustic needed goes down as well as the methanol usage and so far the reactions have gone great!

That's great. Do you heat the mixture when pretreating or do you do it cold?

teralec's Post:

quote:

I'm with John Heron on this-I am getting away with 17.5% methanol-I add NaOH based on original oil volume-Last batch I pre treated 3 times with the last 3 runs worth of by product-mixed for 1 hour each at temp and settled for 1 hour before dropping glyc-made my oil the dryest ever,and gave superb 27/3 result after processing-I'm not going back to wasting 20% methanol(famous last words)

Same question for you. Do you heat as you mix? What's your proceedure?

Don't get me wrong. I swear by this method, just search my posts. I call it "polishing the oil". I do 500 gallon batches so I don't heat that much oil unless I have to. I mix cold.

I used to drain the glycerine after just a few hours but I didn't pass 27/3. Ordinarily, I would pass. Then I noticed that after a day or so, more glycerine would percipitate at the bottom of the tank. Then based on the comments on this forum at that time I came to these conclusions.

Based on my experience, it seems best to polish the hell out of your oil then make sure you have removed all of the pretreatment glycerine from your batch before proceeding.

Tell me what you think.

quote:

That's great. Do you heat the mixture when pretreating or do you do it cold?

I bet thats where the difference in experiences is!
I add the glycerin after I dewater and the oil is cooled down to around 160F. I set the heater to maintain the temp at 150F and mix for around 4hours before settling over night. I still get less out than I put in on the first draining but it all comes out in the end with no ill effects. I am currently only doing 100 litre batches so thats like a drop in the bucket compared to the size of your operation...
The secret must be in the heating, probably in letting the heavier water laden glycerin settle out quicker in the more viscous oil.
Jon

Dane,
OK, back to the subject at hand.
Do you heat when pretreating your oil with glycerine?

Bio logic
Yes I do heat as I mix-basic procedure as follows:feedstock is mainly soy which is wet plus some canola which is very good stuff.(never more than 20% canola)
tip waste oil in processor-all of it including crud and water(empty the cubies completely) (115 lts batch size).(water gets in because oil is stored in open top drum with funnel in outside restaurant!!)
heat to 55c(stat set to 55,but rarely gets hotter than 49c)Once oil is above 35c start running thru 25uM filter sock-filter and heat for around 1hr.Remove filter sock.
Tip in ~20 Lts by product from the oldest of my last 3 runs-mix and heat for 1-2 hrs-transfer to my cone tank-let settle for 1-2 hrs-drop glyc and transfer oil back to processor-switch heat back on and tip in 20 Lts of 2nd oldest by product-heat and mix again for 1- 2 hrs-then settle 1- 2 hrs then drop glyc.Then repeat again using the freshest 20 Lts of by product-heat and mix for 1-2 hrs but this last time I do leave the glyc to drop out over night(forgot to include this in my previous post) before I go on to methoxide addition(I do 80/20 use 5g base NaOH + tit of the oil after 3rd pretreat-base it on 115 Lts of oil,but only use 20 LTs Methanol).The multi glyc pretreat seems to completely dry my oil-I do no other drying process and my oil starts off wet,I can see the water in it-this method has almost completely eliminated soaps being formed and my fuel(used to be an issue with just 1 pretreat) water washes far far quicker and higher yield.For me it is my best method so far.
I do not do any kind of methanol recovery,so my by product is probably quite methanol rich and giving up some meth during pretreat plus probably some titration lowering from excess NaOH.During the pretreat"mixes",the oil is getting lighter and clearer after each pre treat,and changes from a starting"vaseline"emulsion colour to a lovely clear light golden yellow.I pass 27/3 almost immediately the 2nd stage is added but run on for an hour just for good practice-again settling overnight before glyc removal and on to washing-I am considering lowering the methanol further to see how far I can push it.

taralec's comment:

quote:

Yes I do heat as I mix-basic procedure as follows:

This is very good information and you have obviously got your procedure down. Some folks will find this info very useful. But, we are in this thread to answer Dane's needs. We haven't heard from Dane in a while. Maybe it's because this thread got sidetracked. That could be largely my fault.

Anyway, I am a glyc pretreatment addict and I'd love to discuss it further. Maybe we should discuss this in a seperate thread? I think the description of all of your hard work would find a larger audience.

bio Logic
Yes you're right, maybe we should start another thread on the benefits of pretreating.
To answer Dane's original post,I would guess his lost glyc,must be excess methanol/bio that is in his glyc-although it does seem an awful lot at almost 50%.
I would try a test batch,cutting back the methanol a bit.
Good luck.

Nah, I wasn't around because of work. And mostly my question was answered. The gly is still there. And will be unless I want to let it settle for a week or so. Ain't gonna happen. I still process as usual, it passes 3/27, soap test and it looks purty. And obviously all the glyc comes out, because my oil ain't that bad and using 10 gallons of MeoH and getting back 15 gallons of glyc after the processing means the glyc come out eventually.

So my question was answered, got some additional info, and all is well.

In my case when I process 50 gallons I put in 8 gallons (16% total methanol base/base) of meth and drain out 16-18 gallons of gly 40-42 gallons of bio + 16-18 gallons = 58 gallons total so IMO about half of the by product could be methanol and part of it stays suspended in the wvo the drained gly comes out I doesnt reek of methanol when its drained from the pretreatment

What does the glycerin pretreatment do to lower the titration test results? How does it lower the acid value?