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Counterintuitive power control question

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  • jrwme
    Greetings all, First my set up, I have a 50mm (2inch) diameter, 450mm high (18Inch) Bokakob still with copper mesh packing. It is mounted on a 5 L boiler with
    Message 1 of 4 , Dec 28, 2007
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      Greetings all,
      First my set up, I have a 50mm (2inch) diameter, 450mm high (18Inch)
      Bokakob still with copper mesh packing. It is mounted on a 5 L boiler
      with a 2200 Watt electric element. The input power is controlled via a
      Virac (variable transformer). The temperature is measured using a
      platinum PT100 +/- 0.2% RTD.

      I collect my main cuts between 78.4 Deg C and 80.0 Deg C after
      discarding the fore shots. I run up the boiler at full power and then
      reduce the power by reducing the voltage to 70% (half power or 1100
      watts) and collect approx .7L of 94% ABV

      I have found the following, which is Counterintuitive:

      If I reduced the voltage to 35%, (12.5% power or 270 Watts) I only
      collect .4L of 94.5% ABV.

      If I reduced the voltage to 85%, (73.5% power or 1600 Watts) I collect
      .85L of 94% ABV

      I believe that at the lower power settings I should collect more
      product at a higher purity. While the purity has improved slightly,
      the amount of product that I collect at the lower power settings is
      much less than expected.

      Can anyone shed some light on why this may be happening?

      Regards
    • abbababbaccc
      First of all, you are not running your column at optimum efficiency since you are only getting 94% ABV. The low end value is quite understandable since you
      Message 2 of 4 , Dec 29, 2007
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        First of all, you are not running your column at optimum efficiency
        since you are only getting 94% ABV. The low end value is quite
        understandable since you have less vapor generated. WIth less vapor
        and similar reflux ratio you get less product. Besides 5"/s is below
        the best efficiency area.

        Now, since you are not running for 95.6% ABV you use numerically
        lower reflux ratio than is optimal. This means that you can use
        higher vaporspeed without choking since you are taking out more
        product (less reflux running down the column). This in term means
        that at 1.6kW you get more low quality stuff. If you were running for
        95.6% you'd be choking the column at that point. You should note that
        the quality at 1.6kW (~30"/s) is likely inferior to that of 1.1kW
        (~20"/s) if you are using same cuts.

        Cheers, Riku

        --- In Distillers@yahoogroups.com, "jrwme" <jrwme@...> wrote:
        >
        > Greetings all,
        > First my set up, I have a 50mm (2inch) diameter, 450mm high (18Inch)
        > Bokakob still with copper mesh packing. It is mounted on a 5 L
        boiler
        > with a 2200 Watt electric element. The input power is controlled
        via a
        > Virac (variable transformer). The temperature is measured using a
        > platinum PT100 +/- 0.2% RTD.
        >
        > I collect my main cuts between 78.4 Deg C and 80.0 Deg C after
        > discarding the fore shots. I run up the boiler at full power and
        then
        > reduce the power by reducing the voltage to 70% (half power or 1100
        > watts) and collect approx .7L of 94% ABV
        >
        > I have found the following, which is Counterintuitive:
        >
        > If I reduced the voltage to 35%, (12.5% power or 270 Watts) I only
        > collect .4L of 94.5% ABV.
        >
        > If I reduced the voltage to 85%, (73.5% power or 1600 Watts) I
        collect
        > .85L of 94% ABV
        >
        > I believe that at the lower power settings I should collect more
        > product at a higher purity. While the purity has improved slightly,
        > the amount of product that I collect at the lower power settings is
        > much less than expected.
        >
        > Can anyone shed some light on why this may be happening?
        >
        > Regards
        >
      • Christine
        I may be way off base as my distillaton experience is with essential oils, often using transformers in a lab setting. If I am wrong, I sure would like to know
        Message 3 of 4 , Dec 29, 2007
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          I may be way off base as my distillaton experience is with essential
          oils, often using transformers in a lab setting. If I am wrong, I
          sure would like to know why....I've been lurking here to learn how
          to use my ebay bought copper still.

          I think this has to do with the volatility of the compounds. Once
          you cut it back, less "heat" keeps those aromatics
          (alcohols/esters/ketones/aldehydes,etc...) with a higher boiling
          point from volatilizing. Your foreshots contain those aromatics
          with a lower boiling point. At the lower setting the ABV is higher
          (more alcohol). As your volume increases with the higher power
          setting, other aromatics other than the alcohols volatilize,
          decreasing the totat ABV, but increasing the % of non-alcolholic
          compoounds in the mix.

          I would think the 35% power setting would contain less of
          the "tails" than the 70 or 85%. I am asking myself where does the
          tail collection begin? Where do the undesireable compounds start to
          come off at the end of the distillation? Christine

          --- In Distillers@yahoogroups.com, "jrwme" <jrwme@...> wrote:
          ....I collect my main cuts between 78.4 Deg C and 80.0 Deg C after
          discarding the fore shots. I run up the boiler at full power and
          then reduce the power by reducing the voltage to 70% (half power or
          1100 watts) and collect approx .7L of 94% ABV. I have found the
          following, which is Counterintuitive:
          >
          > If I reduced the voltage to 35%, (12.5% power or 270 Watts) I only
          > collect .4L of 94.5% ABV.
          >
          > If I reduced the voltage to 85%, (73.5% power or 1600 Watts) I
          collect .85L of 94% ABV
          >
          > I believe that at the lower power settings I should collect more
          > product at a higher purity. While the purity has improved slightly,
          > the amount of product that I collect at the lower power settings is
          > much less than expected. Can anyone shed some light on why this
          may be happening? Regards
        • Harry
          ... Save yourselves a lot of trouble and speculation. Get a copy of The Compleat Distiller by Mike Nixon & Mike McCaw. It explains all the science, theory
          Message 4 of 4 , Dec 29, 2007
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            --- In Distillers@yahoogroups.com, "Christine" <ccmurph@...> wrote:
            >
            > I may be way off base as my distillaton experience is with essential
            > oils, often using transformers in a lab setting. If I am wrong, I
            > sure would like to know why....I've been lurking here to learn how
            > to use my ebay bought copper still.



            Save yourselves a lot of trouble and speculation. Get a copy of "The
            Compleat Distiller" by Mike Nixon & Mike McCaw. It explains all the
            science, theory and practice behind distillation as it applies to
            ethanol and essential oils.

            The Amphora-society site is currently not processing orders due to
            Mike's ill-health, but you can still get the book through Ian Smiley
            here...
            http://www.home-distilling.com/HD_tcd_main.asp

            IMHO it should be the classroom text.

            Slainte!
            regards Harry
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