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44994Re: Reflux

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  • alaray_992000
    Apr 11 5:29 PM
      My problem has been resolved.
      After checking all equipment it was found that the digital thermometer must have received a knock and whilst appearing to be operating correctly was actually giving incorrect temperatures.
      It has now been re-calibrated and worked perfectly on the last just finished distillation.
      Thanks for your assistance.
      Alan Carson


      --- In Distillers@yahoogroups.com, "Harry" <gnikomson2000@...> wrote:
      >
      > --- In Distillers@yahoogroups.com, "alaray_992000" <carsonar@>
      > wrote:
      > >
      > > Sorry for my lack of information.
      > > My system and procedures are as follows.
      > > I brew 2 brews of 57 litres each containing 12 and a half kg
      > Dextrose
      > > and 3kg Sugar. This is brewed with Heat Wave yeast. Each 57 litre
      > is
      > > stripped giving 17 litres (34 litres total) for the 2nd
      > distillation.
      > > The still is 60 litre S/S with a column of 1.15 metres x 50mm S/S
      > non
      > > packed for stripping and for the 2nd distillation a 1.95 mitre x
      > 50mm
      > > S/S column packed with Structured Pure Copper Mesh Column Packing
      > > with a gap of 100mm from the return pipe from the offset head to
      > the
      > > top of the packing.
      > > The still is heated by a 2400 watt element controlled by a Helios
      > SSR
      > > controller which allows me to strip at 100% and then on the 2nd
      > > distillation turn power down to 30%. I reflux normally between 30 –
      > > 50% heat settings. My 2nd distillation gives me an output of
      > between
      > > 13 and 14 litres at 94/95%. I re-distil any distillation below 93%.
      > > In the past things have gone well with output of 95% for 13 litres
      > > with top of column temps reducing from 80at start to as low as 76
      > > during distillation. I am at a loss as to why I could not get the
      > top
      > > of column temp below 86. To my knowledge I did not deviate from
      > > normal procedures.
      > >
      >
      >
      > Sounds like you're doing everything right. Looking for
      > possibilities...
      >
      > The temp at the top of the packed column is an indication of the
      > ratio of [ethanol : water] vapours passing the probe. At 86°C
      > measured, it's somewhere around 75% ethanol to 25% water (assuming a
      > binary mix for simplicity. It's not, as there are minute amounts of
      > other substances involved, but I digress...).
      >
      > Now this is fine for a flavoured spirit (e.g whisk(e)y or rum) but
      > not good enough for GNS or vodka. And it's certainly not good enough
      > for a packed-column reflux run.
      >
      > To increase purity (therefore separation) in a 50mm Ø you need to:
      > A. Increase the coolant flow
      > B. Decrease the product takeoff
      > C. decrease the energy input
      >
      > A combination of A & B will increase the reflux ratio, thereby
      > improving separation. 'C' is necessary if you are overdriving the
      > still, creating more vapour than the still column was designed to
      > handle.
      >
      >
      >
      > It's entirely possible that your controller has developed a fault and
      > you may be applying more power than you think. I find it suspicious
      > that in previous runs the temp was dropping below the BP of ethanol.
      > This indicates either a LOT of heads or not enough power being
      > applied to maintain the boil. From your above description of the run
      > in question, I'd be checking the accuracy of the controller with a
      > multimeter. Some of them are not designed for continuous duty cycle.
      >
      > Also check the coolant system for correct operation. There may be a
      > blockage of some sort restricting flow and upsetting reflux ratio.
      >
      > Let us know the results.
      >
      >
      > Slainte!
      > regards Harry
      >
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