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Thread: washing with heat

  1. #21
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    Re: washing with heat

    Hi Cade,

    Quote Originally Posted by Mark View Post
    Luckily for you I am a Chemist, unlike anyone else on this forum.
    Indeed, we are lucky.
    If it had not been for Mark, it is doubtful that anyone else would have realized that you can not make biodiesel at room temperature using the "standard" production procedure.

  2. #22
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    Re: washing with heat

    Sounds like you have a fair handle on this.

    this one will test you

    from what you are saying I wont be able to get all of the methanol out of solution by heating. That would imply that there will still be remaining methanol once it has stopped 'boiling'.

    So how much methanol by weight (this is much easier to measure) will there be in solution before I start to boil?

    FYI I use a 20% by volume proportion of methanol to oil (i.e. 40L meth in 200L of oil)

    Reason I ask this is to know how much methanol I have removed at the end of the 'boiling' process. I will do a test on 1kg of freshly made bio.

    I will do a test over the weekend, as i need to get this right soon. I dont want to be paying for fuel any longer than I have to!
    Regards,

    Cade.

    2006 Landcruiser HDJ100 (1HD-FTE) 20,000 on bio
    2006 Ford Courier(WLT Motor), 10,000 on bio
    2002 Landcruiser HZJ105r (1HZ motor) 250,000 on bio (sold)
    2006 Mazda B2500 (WLT motor) 80,000 on bio (sold)



  3. #23
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    Re: washing with heat

    Re: washing with heat

    'Luckily for you I am a Chemist, unlike anyone else on this forum.'

    I think you need to pull your head out of your arse.

  4. #24
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    Re: washing with heat

    Tilly, post No 21, I think you mean 'can' not 'can not' Also in a previous post you said the neutralisation reaction between ffa's and methoxide does not produce water, I don't think you are correct, it does produce water.

    Cade and Tony, I have tested processed, raw bio many times whilst bubbling for soap. The starting soap level post reaction is very variable depending on quite a few factors but after settling for 12 hours it is nominally 2500ppm. You can bubble/de-meth at ambient temperature (takes longer than if using heat) and you will find the soap level decreases exponentially.

    A settling time is required after bubbling as some of the glycerol/soap still in suspension will be mixed up by the bubbler. Nominal soap levels (using KOH) after bubbling 24 hours and settling 24 hours is 250ppm. If you don't intend to do any further purification then further bubbling will be reqd to reduce the soap to max spec (66ppm) but most here (UK) will pass the 250ppm level bio through woodchip or similar which should reduce the level to <66ppm.

  5. #25
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    Re: washing with heat

    Cade, there is a rough way to estimate the methanol left in your bio.

    Based on a 100 litre batch and adding 20 litres of methanol. The approximate amount of methanol reqd to reach full conversion would be 12.5 litres.
    The residual methanol of 7.5 litres is split 'roughly' 3 to 1 glycerol to bio, So roughly 1.9 litres in the bio and 5.6 litres in the glycerol.

    So the answer to your question of how much methanol by weight is left in your 200 litre batch is 3.8 litres x 0.82= 3.1kgs (roughly)
    Last edited by smithy; 19th October 2017 at 03:34 AM. Reason: Additional information for Cade.

  6. #26
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    Re: washing with heat

    Hi smithy,

    Quote Originally Posted by smithy View Post
    Tilly, post No 21, I think you mean 'can' not 'can not'
    Exactly the point.
    You still do not know that biodiesel can not be produced at room temperature. I think Mark needs to come back and explain to you again that you can not make biodiesel ar room temperature.
    Otherwise you will probably keep making biodiesel at room temperature which we now know is not possible.



    Also in a previous post you said the neutralisation reaction between ffa's and methoxide does not produce water, I don't think you are correct, it does produce water.
    You are correct, it does produce water! I wonder why I have thought it did not produce water.

    "When an alkali catalyst is added to these feedstocks, the FFA react with the catalyst to form soap and water as shown in the reaction below:"

    R-COOH + KOH R-COOK+ H20"
    Last edited by tillyfromparadise; 19th October 2017 at 04:13 AM.

  7. #27
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    Re: washing with heat

    Hi smithy,

    Quote Originally Posted by smithy View Post
    Cade, there is a rough way to estimate the methanol left in your bio...is split 'roughly' 3 to 1 glycerol to bio...
    My testing as well as Neutral's showed the split was about 2/3 of the recoverable methanol is in the byproduct layer and 1/3 of the recoverable methanol is in the biodiesel layer.
    But these are only "rules of thumb" and are variable

  8. #28
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    Re: washing with heat

    Captain Cademan; Yes heating the crude bio will drive off the excess methanol. I have used vacuum distillation to remove the excess alcohol. Lowering the pressure enough and methanol might become vapor at maybe 20-30 degrees celcius. But imploding the boiling pot if it is large and the pressure is low is a possibility. I made an aparatus that allowed a gas to bubble through a boiling pot in a vacuum still (that's not from a book). By lowering the air pressure over the biodiesel the methanol can boil out at reduced temperature, increasing energy efficiency. You can find on the internet the boiling point of methanol at various atmospheric pressures. There's another formula for figuring boiling point of methanol diluted by a higher boiling miscible solvent (biodiesel) at atmospheric pressure. I probably don't need to give that one.

  9. #29
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    Re: washing with heat

    Captain cademan; using a google search on the internet using key words Methanol (data page) Wikipedia , I found the boiling point of methanol at 100 milliters of air pressure is about 20-21 degrees centigrade. Pulling vacuum on a still pot of 100 millimeters of pressure while allowing slow release of air at the bottom of the still pot would create a moving gas phase to remove methanol vapor at any temperature above about 21 degrees centigrade. It's a balancing of energy input to optimize biodiesel production with a minimum of energy input. Obviously running the electric vaccuum pump requires energy expense. Just boiling it out would be energy expensive, but it would work. On biodiesel forum Ireland a while back , someone removed methanol from crude biodiesel , then let the crud settle out over weeks or months.

  10. #30
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    Re: washing with heat

    The boiling-point elevation of a solution relative to that of a pure solvent (methanol) depends on the concentration of dissolved particles (biodiesel present), just as vapor pressure lowering does. The change in boiling point Delta T boiling for a solution is , delta T equals molal (not molar) concentration of solute particles (number of moles of solute per kilogram of solvent) times molal boiling-point elevation constant (which I do not have). In a high boiling liquid (biodiesel) a lower boiling liquid's (methanol) boiling point is elevated based on it's quantity present in the larger liquid volume. It's boiling point elevation, methanol diluted in biodiesel. High heat will force almost all of it out. At reduced pressure with a moving phase of air passing through it that changes the physical dynamics (it's cheating on the boiling point elevation formula using evaporation in addition to boiling out of a dilute methanol/biodiesel solution). That's the formula I skipped earlier in this thread. Slowly bubbling methanol out under vaccuum.
    Last edited by WesleyB; 19th October 2017 at 10:03 PM.

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