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Glycerol disposal problem

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  • Glycerol disposal problem

    A question, Gents. I've been making bio from WVO, using KOH for a couple of years now. The mix usually titrates between 5.8 and 6.1, and I use the 80/20 method. I usually make between 200 and 260L, water-washing with about 5L of cool water for an instant before stopping the pump. Add and drain several 10L buckets of water thereafter, then airwash, finishing up with a spray-dry at about 40-50°C before storing the fuel. For the last few times, the glycerol drops out of the reactor at about 30°C, but in the bucket, it turns to gloop - about the consistency of stiffish mortar. Even if I mix it 1:1 with water, it's like that, whether or not I mix in 5kg of cement to the methoxide and settle it out. If left in the bucket, it resembles sloppy soap, with rain making it into a nice hand wash. But it's almost impossible to get rid of. Am I missing something, or doing something wrong?
    Photo 1: On the way out of the reactor;
    Photo 2: Gloop after 5L of water with paint mixer.
    Cheers

  • #2
    G'day Monaro,
    I assume you are using KOH in the titrating fluid. You have fairly high titrating oil. That means you are making a fair bit of soap in the reaction that will come out with the glycerine. This may be affecting the viscosity of the glycerine. I have quite a bit of glycerine sitting around and it does increase in viscosity a lot but It will still slowly flow out of the container and I can dip it out with a pan. My WVO only titrates at between1 and 2 KOH so there is not as much soap produced when making my biodiesel.

    How much methanol and KOH are you using per litre of WVO?

    My testing has shown that the only thing that mixing cement in the methoxide does is to increase the cost of producing your biodiesel by the added cost of the bag of cement and the wasted methanol because some of the methanol comes out with the cement layer.
    For years I have routinely made biodiesel at ambient temperature without using cement. I do however softly intone the "Happy Biodiesel Warrior chant" while mixing the biodiesel which I am sure has the same or better results as adding cement.

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    • #3
      Thanks, Tilly. My latest batch was 18% methanol, 260L of oil and 4.16kg of KOH. My KOH (1g/1L deionised water) may be a bit old, so it's probably time to recalibrate this aspect. I'tt try a smaller batch next time and get it accurate before going bigger...

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      • #4
        It's not clear to me what method you're using, but warmth always increases the viscosity of the glycerol. It's also not clear to me whether the glycerol gets any water before you drain it. I drain my glycerol before the first water (acid) wash, and it's only slightly more viscous than water. That's because it's the potassium salt - if you let any water get near it, you protonate the glycerol, which promotes hydrogen bonding, and therefore increases the viscosity. The other thing is heat will drive off residual MeOH which always helps thin it out

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