Glycerol composition.

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: Glycerol composition.

Hi smithy,

You are correct!
It did puzzle me that you would admit to having a yield under 100% when performing a reaction

Thank you for pointing out my mistake.

[smithw Senior Member Find all posts View Profile Close smithw]

Re: Glycerol composition.

Around 300L sometimes 330L sometimes 280L Just depends on how fatty the oil is. I generally don't titrate the oil before I start, as what would I do with this information?
Last time I did it I think it was around 7-8, so the WVO is pretty filthy.

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: Glycerol composition.

Hi smithw,

I used to make a lot of my biodiesel from animal fat/ tallow. The main brands I used were "frytol" and "red band"
I found that animal fat requires the same reaction procedures and the same chemical amounts as you use reacting vegetable oil and would produce similar yields.

The "rule of thumb" is that in a normal single stage base reaction, for every 1% FFA's present in the oil you will will lose 1% yield as the soap produced and 2% yield because of the biodiesel bound with the soap.
A KOH titration of 1= about 1/2% FFA
WVO with a KOH titration of 8= about 4% FFA which should result in a loss of yield of about 4% as the soap produced along with about 8% loss of yield due to the biodiesel bound with the soap.

That means that if you were doing a single stage reaction on WVO titrating 8 KOH you would expect a total loss of yield of around 12% so you should expect a yield in the order of 88%.
I do know that on the occasions when I actually checked the results I achieved, my yields were pretty much in line with these numbers or possibly a slightly less yield.

However, because your first stage reaction is a glycerol pre-wash these numbers change and that depends on a number of things including, but not limited to, the amount of methoxide and the amount of glycerin contained in the glycerol that is used to do the pre-wash reaction.
Many people find that after they perform the pre- wash reaction stage and drain the glycerol, besides a partial reaction occurring, there is actually an increase in volume of the contents in the reactor.
This increase in volume in the reactor is due to some of the biodiesel bound in the glycerol that was added to the reactor to perform the pre-wash reaction had been released into the reactor.

Your yield seems to be considerably less than I would expect you to achieve

[smithw Senior Member Find all posts View Profile Close smithw]

Re: Glycerol composition.

Tilly I also do a caustic striping, and I lose about 40-50 L with that. If I don't do a caustic strip my bio gels in winter.

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: Glycerol composition.

Hi smithw,

Tilly I also do a caustic striping, and I lose about 40-50 L with that. If I don't do a caustic strip my bio gels in winter.

That is an awful lot to lose in caustic stripping

I personally have never performed caustic stripping, however the articles I have read about caustic stripping seemed to suggest that the only loss is the FFA's converted into soap which is a loss of 1% yield for every KOH titration of 2.

The things that normally affect the gel qualities of your biodiesel is the oil the biodiesel is made from and the amount of conversion of the biodiesel.
I understand that if you use ethanol in the reaction that will affect the gel qualities of the biodiesel produced but I do not know anyone who produces backyard biodiesel who uses ethanol

I doubt that converting your FFA's into soap by caustic stripping would have any significant affect on the gel properties of the biodiesel when compared to biodiesel where the FFA's are neutralized in the normal way using methoxide. In either case you are converting the FFA's into soap and water and removing the soap and water

What chemical are you using to do the caustic stripping?
If it were me, I would do a few 1 litre test samples just to make sure there really was an increase in jel temperature when performing the standard reaction.
I do not think there will be.

In the mean-time I will do a little research and see what I can find on caustic stripping.
I do know that Keith Addison was one of the first backyard biodiesel producers to do some testing with caustic stripping and he posted his results on his JTF site.
I'll go have a look

[smithw Senior Member Find all posts View Profile Close smithw]

Re: Glycerol composition.

Caustic striping formula is, titrate the WVO ,lets call it Y
3.5+Y add this amount of NaOH to 40ml of boiling water for every liter of feedstock.
Mix in the caustic water into the feedstock at 50C
Drain and allow the soups to settle overnight.
This will strip the FFA from the feedstock and lower the amount of catalyst needed for the batch.
I cant take credit for this, I use Paul Martins book, he is a industrial chemist and bio diesel expert.
http://grownfuel.com.au/

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: Glycerol composition.

Hi smithw,

Caustic striping formula is, titrate the WVO ,lets call it Y
3.5+Y add this amount of NaOH to 40ml of boiling water for every liter of feedstock.

You are lowering the titration number of the oil by about 4 which is only about 2% FFA.
2% FFA is about 8.4 litres of your starting total of 420 litres of WVO but you are removing 40- 50 litres of content from your reactor when performing the caustic stripping.
Something is not right there!

That seem a lot of NaOH.
Keith Addison's recommendation is to only use the titration amount of NaOH mixed into 40ml water per litre of WVO
http://journeytoforever.org/biodiesel_make2.html#deacid

[smithw Senior Member Find all posts View Profile Close smithw]

Re: Glycerol composition.

Im not a chemist so Ill take your word for it, Ive been using Paul Martins method for over 10 years, I had all sorts of problems before that and almost gave up. I see he has a new book, I don't know if he has updated his formula or not, but it might be worth a look.

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: Glycerol composition.

A quick addition-

If you are performing the titration using NaOH instead of KOH the conversion factor for FFA% using an NaOH titration is:
FFA% = 0.766X titration number.

So, if you perform a standard biodiesel titration using NaOH instead of KOH and the NaOH titration number is 4 then the FFA% is:
0.766X 4= 3.06% FFA.

[Tony From West Oz Vice Chairperson of WARFA Find all posts View Profile Close Tony From West Oz]

Re: Glycerol composition.

Caustic striping formula is, titrate the WVO ,lets call it Y
3.5+Y add this amount of NaOH to 40ml of boiling water for every liter of feedstock.
Mix in the caustic water into the feedstock at 50C
Drain and allow the soups to settle overnight.
This will strip the FFA from the feedstock and lower the amount of catalyst needed for the batch.
I cant take credit for this, I use Paul Martins book, he is a industrial chemist and bio diesel expert.
http://grownfuel.com.au/

Smithw, I would recommend against mixing the NaOH (or KOH) with boiling water. Mixed with cold water, the caustic will raise the temperature of the water to over 50°C.
If you use boiling water, you will have the water turning to steam, taking the caustic with it. The steam will be highly corrosive.

[smithw Senior Member Find all posts View Profile Close smithw]

Re: Glycerol composition.

I should of said very Hot water which is what i do.
So my first batch of cement diesel is now drying. Heres the good the bad and the ugly. The first thing i noticed is that putting cement in the methoxide just looks wrong, once i got over that, I also notice that as I pumping the methoxide the WVO seemed to generate a lot more heat and the methanol smell stunk out my shed.The reaction too was also quicker. I would of lost about 5Liters of methoxide as the cement seems to expand making this nasty mud in the bottom of the barrel and was difficult to suck the last little bit of methoxide out.
I got 90 liters of glycerine out down from 120L and the colour of the last 20 liters was very light.
Ill post the results of the bio test when it drys.

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: Glycerol composition.

Hi smithw

Were you performing a controlled comparison test with two identical batches of WVO taken from the same heating container where the only difference was that one batch used cement dried methoxide and the other batch used normally produced methoxide?

[smithw Senior Member Find all posts View Profile Close smithw]

Re: Glycerol composition.

No i didn't. I just compared the what i usually do, to what i usually do + adding cement. If the 3/27 test is good I going to try less Naoh in the caustic striping + cement.
Hope that makes scene, Im not feeling well and my brain hurts

[tillyfromparadise Senior Member Find all posts View Profile Close tillyfromparadise]

Re: Glycerol composition.

Hi smithw,

You did not perform a comparison test just comparing it to what you normally achieve.
In an earlier post to this thread you posted your yield was:
"Around 300L sometimes 330L sometimes 280L."
That would put the 90 litres of glycerine in this batch in the range you typically achieve

If the 3/27 test is good I going to try less Naoh in the caustic striping + cement.

You are doing a three stage reaction procedure with Caustic stripping after the first stage- that is certainly not the norm

1. Your first stage reaction is the glycerol pre-treatment which contains an unknown amount of methoxide and an unknown amount of biodiesel.
This will result in the first stage reaction producing an unknown amount of soap+ an unknown amount of water+ an unknown amount of partial an fully reacted biodiesel+ an unknown amount of biodiesel falling out of the glycerol that was added to the reactor into the reactor
2. You then perform a caustic stripping procedure
3. You then perform an additional two stages of reaction containing a total of 20% methanol and add water to the third stage at the end.

I would be surprised if you did not pass the 3/27 test

I agree with reducing the NaOH in the caustic stripping- you seem to be using far too much.
If it were me, I would have another look at the caustic stripping instructions in the book just to be sure

[smithy Senior Member Find all posts View Profile Close smithy]

Re: Glycerol composition.

Hi smithw, I would say you are doing the glycerol pre-treatment and the caustic stripping the wrong way round. How are you drying your oil after caustic stripping. The norm is to strip first then run off the water, then use glycerol.

Always difficult to say on a forum unless I was there to help you but I rekon your very poor yield is due to wet oil after stripping. In any case there is no need to caustic strip with oil that only titrates at 4ish, it is an over complication that you don't want.