## Counterintuitive power control question

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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
Message 1 of 4 , Dec 28, 2007
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
• 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
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
>
• 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
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
• ... 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
--- 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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