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Thread: Glycerol composition.

  1. #21
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    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/

  2. #22
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    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
    Last edited by tillyfromparadise; 4th December 2017 at 08:01 PM.

  3. #23
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    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.

  4. #24
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    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.
    Last edited by tillyfromparadise; 5th December 2017 at 01:12 AM.

  5. #25
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    Re: Glycerol composition.

    Quote Originally Posted by smithw View Post
    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 50C.
    If you use boiling water, you will have the water turning to steam, taking the caustic with it. The steam will be highly corrosive.
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  6. #26
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    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.

  7. #27
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    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?

  8. #28
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    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

  9. #29
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    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

  10. #30
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    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.
    Last edited by smithy; 8th December 2017 at 02:44 AM.

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