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Thread: The Warnqvest Test and re-processing

  1. #1
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    The Warnqvest Test and re-processing

    "The Warnqvest Test and re-processing

    Over the last several years, a procedure has gained in popularity which uses the dropout amount from a warnqvest test to calculate the amount of chemicals required to reprocess or perform the second stage of a 2 stage reaction.
    This method involves measuring the percent of dropout in the warnqvest test and then treating this as the percent of oil with a zero titration remaining from the initial reaction to be reprocessed.

    An Example
    You have a 40 litre batch of oil that you react and find that when you then perform a 10/90 version of the Warnqvest test you have 3ml of dropout.
    3ml dropout is 30% of the 10ml warnqvest test sample, so you then calculate the un-reacted oil remaining to be reacted in the second stage as 30% of 40 litres.
    30% of 40 litres is 12 litres.
    Because all of the FFA's have been converted into soap in the first stage, you treat this remaining 12 litres of oil to be reacted as if it were new oil with a zero titration.

    When reacting oil with a zero titration, most people will use 5g NaOH/ 8g KOH mixed into 200ml methanol for every litre of oil being reacted.
    In the above example, you have calculated that there is 12 litres of oil remaining to be reacted.
    The KOH amount required in the reprocess is 8g X 12= 96g KOH
    The methanol amount required in the reprocess is 200ml X 12= 2400ml Methanol

    This method has been proven to be quite reliable in performing a second stage reaction that does produce biodiesel that subsequently passes the Warnqvest test.

    Recent testing posted to another thread on this forum has demonstrated what everyone has suspected for years, there is NOT a 1 to 1 correlation between dropout and conversion in the Warnqvest test.

    People have asked why the above procedure works so well at reprocessing if there is not a 1 to 1 correlation between dropout and unreacted oil.

    Some preliminary information

    Most people want to make very high conversion biodiesel that will pass the Warnqvest test while spending as little money as possible.
    Testing has shown that the formula of 5g NaOH/ 8g KOH and 200ml methanol is about the least amount of chemicals you can use to react a litre of zero titration oil in a single stage that will probably pass the Warnqvest test.
    If you use more chemicals than 5g NaOH/ 8g KOH and 200ml methanol, this will give you even higher conversion and a more reliable pass on the Warnqvest test.

    For instance, a few weeks ago I made a litre of biodiesel from new oil using about 16g KOH and 250ml methanol.
    This turned out to be extremely high conversion biodiesel, but it also cost more to produce. I would not use this formula for my daily driving biodiesel.

    Why the above procedure works so well if there is not a 1 to 1 correlation

    Recent testing has shown that the Warnqvest test actually has more dropout than would be the case if there were a 1 to 1 correlation.
    In other words, the above procedure overstates the amount of oil remaining to be reacted and as a consequence, if you use the above procedure, you end up using more than 5g NaOH/8g KOH and 200ml methanol for every litre of oil remaining to be reacted.
    This results in a very high likelihood that you will pass the warnqvest test after reprocessing using this procedure."
    Last edited by tillyfromparadise; 21st July 2014 at 10:42 PM.

  2. #2
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    Re: The Warnqvest Test and re-processing

    This test is completely unnecessary. You are making fuel, not a pure laboratory product. Using biodiesel, instead of WVO, is all about viscosity. The efficiency of conversion is therefore immaterial - as long as you have sufficient conversion to reduce the viscosity enough so that your car will start on a freezing cold winter morning, that's the only test you need. Personally a far more useful test would be to put the fuel in the fridge after you make it. If it doesn't gel (which it may if you don't have full conversion) you're good to go. That's not to say that there is not some clever chemistry behind this test, because there is - you just don't need to do it.

    www.drchemical.com.au
    Last edited by Dr Mark; 20th March 2017 at 10:47 AM.

  3. #3
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    Re: The Warnqvest Test and re-processing

    I disagree, but only in one instance. If you are making biodiesel from fat then complete conversion is the best way, otherwise your filters are going to clog when the fuel cools down. When using liquid oil unconverted oil is no problem as it just mixes in with the bio.
    Johnnojack
    4WD Isuzu Jackaroo 3.1 160,000km on WVO,(2016) 2 tank home built system 6 solenoids. Mk. 9 version. Improvements under investigation

  4. #4
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    Re: The Warnqvest Test and re-processing

    The Warnqvist test is more accurate than most people think. The dropout amount as Tilly rightly reported does overstate the amount of triglycerides, however this is only part of the story.

    In the methanol phase there are also 'invisible' monoglycerides present and (presumably) some diglycerides. To achieve full conversion both these 'intermediates' need to be converted into biodiesel (fame)

    Somehow, be it by luck or a querk of fate the overstated dropout amount revealed by the test, resulting in what would seem to be an over addition of chemicals for the next reaction actually is the correct addition to mostly convert the mono's and di's.

    I say mostly because (and I have done many tests to try and get rid of these totally) there is always a small amount of monoglycerides present. Water washing by an agressive nature (pump or compressor) reveals a small emulsified layer which settles between the water and the bio. If this layer is removed the mist/gel point temperature of the biodiesel is reduced.

    Here in the UK with our colder Winters some have a lot of trouble with misting etc. My biodiesel is made from lightly used rapeseed and with this emulsified layer removed the misting point is reduced to below -9C, with the mono's left in the bio this temperature is 3 to 4 degrees higher.

  5. #5
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    Re: The Warnqvest Test and re-processing

    Quote Originally Posted by Johnnojack View Post
    I disagree, but only in one instance. If you are making biodiesel from fat then complete conversion is the best way, otherwise your filters are going to clog when the fuel cools down. When using liquid oil unconverted oil is no problem as it just mixes in with the bio.

    Yes that's a fair point - I hadn't considered that. I've only ever used liquid WVO

  6. #6
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    Re: The Warnqvest Test and re-processing

    Generally the higher the molecular weight an organic chemical has the lower the vapor pressure. In considering synthetic fuel made from vegetable oil, relatively positive and negative polarity areas of a molecule decrease the vapor pressure also. A fuel with high vapor pressure turns to gas easier when injected into the combustion chamber, so monoglycerides and di glycerides are bad to be present in biodiesel because they don't vaporize as easily as the methyl or ethyl fatty acid esters. A more complete reaction produces a better fuel since it vaporizes easier.

  7. #7
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    Re: The Warnqvest Test and re-processing

    Good to know Wesley, thank you.

    I will carry on emulsifying the mono's via my aggressive water wash and thus removing them.

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