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Re: [Distillers] Continuous still ?

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  • Ted Palmer
    I feel that to get any real return from such a setup you have to be heating the wash to the temperature of the steam that is condensing, in this case the
    Message 1 of 4 , Feb 18, 2001
      I feel that to get any real return from such a setup you have to be heating the wash to the temperature of the steam that is condensing, in this case the ethanol. That means a large surface area(best) and/or long contact time with the steam(not good for this usage). I don't think a "cold finger" will work. Do the math using a larger id tubing for pressure drop and flow rate. You'll probably find that 20 feet of 1/2" refrigeration copper is the best solution, which means a redesign of the condenser to accommodate such a large coil. Also solves the low feedrate problem.
      What to do when you run out of wash? just put water in the feed tank to keep the condenser cold till the run is done.
      A pump is the only way to go. You'll need a preheating system to get up to speed and a pump with a few valves to recirculate the wash from the thumper section back into the instant hot water heater is an easy solution. The pump can then be used to move the feed into the system with a few valve turns. My grandfather abandoned a gravity system after the still kept running dry when the pressure dropped from having less weight of wash to push down with.
      So why even go through with all this? 30% energy savings is nice but the amount of time that you can save is worth even more!
      Ted Palmer

      Good thinking... my plan was to try and keep it as simple as possible,
      without using anything fancy (not even a pump) or extra - see if I could do
      it as a simple add-on to a normal column...but you got me thinking more
      about trying to use the condenser, rather than the boiler. 

      I originally had problems with seeing how to pass the wash through the
      condenser coil (as my present one has quite a large pressure drop - doubtful
      that a simple gravity feed system would push through it).  But - how about a
      "cold finger" design ?  It doesn't have to be perfect - just as long as the
      feed does a fair chunk of its heating up there, it is freeing up the boiler
      to make the vapour.  And keep the water cooled coil above it, for backup in
      times of low wash feedrate.  The coldfinger could be a large diameter, with
      little pressure drop.  The way I have my condenser at present, this could
      easily be added as a separate unit between the condenser and the metering
      valve - no modifications required.  The only downside of not perfectly
      heating (or superheating) the feed is that it will use a bit more of the
      column to heat up - so get a small dead zone not doing much below the feed
      point, other than transferring heat - no dramas - just make the stripping
      section a little bit longer.

      I've included a second diagram - not to scale, but to show the layout

      By taking the coil out of the boiler, the boiler could be made even smaller.
      The new problem that this introduces is that the wash barrel now has to be
      higher than the top of everything - probably a couple of meters up.  Need
      someway of getting it on top of a ladder, or using a header tank (and pump,
      damm !)

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