GNS Continuous Still?

edited January 9 in General

Howdy all,

So i just had a thought... tell me if this is stupid please...

OK so I've read that a lot of folks redistill their GNS for vodka so its made in house.

My question, is it dumb to think that a pretty simple continous still with a few rectification plates at the top could be made to run GNS through? I mean there are no solids to deal with, minimal anything other than water and ethanol... hell would you even need to make cuts since it's already fully rectified?

Typically stripping stills would see a 8-12% beer, what's would you proof your GNS down to if you ran this setup?

Thanks,
B

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Comments

  • edited January 7

    No dilution, run full strength, the only thing you'll be taking off is heads (which can be done as vapor).

    A well known manufacturer sells a system like this.

    image

    Uses a very, very simple approach. At 2 gallons feed rate a minute, it's a little rocket ship.

    image.jpg
    800 x 470 - 30K
  • There is an older thread where we talked about this design a little bit. A small amount of alcohol is lost as vapor along with any heads.

    Given your input is near azeotropic, if your source product is decent quality GNS, there are no tails to cut away, and it's likely the only material cut would ever be a heads cut as a 'correction'.

  • edited January 7

    Thanks @grim, I've seen this drawing and it makes WAY more sense now knowing that's its to rerun GNS (not produce GNS like how I read it).

    So say you don't have the $45k for the model above, and wanted to run it as an electric element driven thermosyphon reboiler. Do you think you could proof down to say 40% or would you need to go lower?

  • @grim said: There is an older thread where we talked about this design a little bit. A small amount of alcohol is lost as vapor along with any heads.

    Thanks, I'll see if I can find it!

  • edited January 6

    Electric element would work, but you would need additional level sensors to prevent the element from running dry, and if you really built this thing using all classified (xp) electrics, it would be expensive. Your feed rate will be entirely determined based on how fast you can vaporize 100% of your feed.

    Unfortunately, you absolutely can not proof down with this approach. Your product will be taken off as exactly the same proof as your input. If you proof to 40%, your distillate can not be considered vodka or neutral spirits, it's going to come off at 40%.

    Would also require significantly more energy to heat and cool the greater volume.

  • Ah that makes sense. So by steam heating a HX to reboil the 95% GNS, there's not the same explosion risk as running a submersible element dry.

    Thanks man!

  • There is zero material difference between 40% ethanol and 95% ethanol in terms of flammability or explosivity at or near it's boiling point.

  • edited January 7

    Thanks @grim

  • edited January 9

    OK I'm kinda obsessed with this now

    Using the drawing above... what if instead of a steam reboiler one were to use band heaters like on some of the old @Telluride continuous columns?

  • edited January 7

    Go back and do the math required to heat and vaporize ethanol, and work backwards from your power input to see what that means in terms of feed rate.

    I don't have a calculator handy, but I'm guessing you'd be talking somewhere in the ballpark of 40kw to support 2gpm, assuming zero heat recovery (which isn't the case), so maybe closer to 30kw?

    That thing isn't a reboiler, it's a single pass 'boiler', in 1 minute, 2 gallons of feed is heated and completely vaporized.

  • edited January 7

    Ok single pass boiler.

    Yeah but who says you have to run it that fast.

    To run a 55g barrel in 6 hours (using 408w pg ph) you'd only need 3.7kw.

  • Anybody every see one of these first hand? Is the column an actual column and what keeps it hot? Or is the column being hot an academic detail?

    StillDragon North America - Your StillDragon® Distributor for North America

  • Nope, can't even find an actual picture of it.

    Based on the drawings I assume it's heated by the boiler

  • There are photos on the site under skid mounted - of the larger version.

  • That larger one is a behemoth at 5-10 gpm

  • The column can only be working as a thumper.

  • edited January 9

    @grim, What makes you say that?

  • edited January 8

    The vapor tube out of the boiler enters the top of the still column.

    If it was entering as straight vapor, what point would the “still column” even have?

    If this thing was a fugazi, why not just pump the vapor straight into the condenser and out?

    The level sensor for the column is off to the side in a separate sight glass style arrangement. This is only ever done when the contents of the vessel are boiling or moving violently enough to cause a problem for the level sensor.

  • That makes sense, at least with the thumper some of the heads would still redistill off.

  • The diagram also shows a little elbow on the inside of the column. Not sure why they would have shown something like that too.

  • I saw that little elbow too, I thought it might be just to direct any liquid that boiled up from the boiler down

  • edited January 9

    @Bolverk said: To run a 55g barrel in 6 hours (using 408w pg ph) you'd only need 3.7kw.

    Based on playing around with this design, I can't see how you could do that with such little power.

    The latent heat of vaporization of ethanol is 340btu/lb, at 6.8 pounds a gallon for ethanol, we're talking 127,000 BTU's or 37kw total, just to take it from near boiling to vapor. So for a 6 hour run time, you'd need 6.2kw, and that's just vaporization, which doesn't account for heating from ambient to boiling point.

    Now sure, you'll recover some energy with the preheater, but there are going to be losses on the piping, column, etc.

    I tried to do the math in my head the other day thinking 30-40kw to achieve the 2gpm they state, but it's probably even more than that.

  • Wow, I was way off.

    I got the 408w pg ph based on other continous threads.

  • My main bain marie still is 330l but when i run it with 220l i run it with 3 elements pushing about 6kw each. On a 220l batch it will heat up in about 45 mins and strip in about 2.5 hours. A 330l run will take about an hour and 15 mins depending on the abv and take 3.5 to 4 hours to strip. Again depending on the abv and if it pukes and inhave yo slowndown the first 30 mins.

  • edited January 10

    Just looked at some of those older threads, those guys were talking about 408 watts per gallon of feed per hour, not per minute, which I think explains it. For 2 gallons a minute, that's 2 * 60 * 408 = 49kw. Now we're cooking.

    I have a tube in shell boiler that came out of a Millipore steam distillation purifier skid unit that I was experimenting with for building one of these. It's built for steam feed, and to boil 100% of the feed in one pass.

    I'm not joking when I tell you that thing can easily consume every single BTU of our main boiler to be able to boil off a few gallons a minute (single digits). We're talking way more than 150kw, but there was no heat recovery in my testing.

    One of my favorite tests was trying to build a continuous gin still off the vapor feed. Take a feed from a barrel of GNS and a barrel of water. Boil them off at the desired ABV. Push that vapor through a set of two baskets (with a valve to direct the vapor feed). Turn that baby on and just keep changing baskets until your swimming pool is full of gin.

  • Man, I can't even imagine 2 gpm...

    That's cool idea!

    There's a distillery in Australia (I think, i do know Downunder Stills made the column) that runs a rum continous with thumpers that they can switch in/out like that. Very cool idea.

  • @grim said: Unfortunately, you absolutely can not proof down with this approach. Your product will be taken off as exactly the same proof as your input. If you proof to 40%, your distillate can not be considered vodka or neutral spirits, it's going to come off at 40%.

    I don't have a horse in this race, but while vodka needs to be distilled to 190+ proof, I don't see a stipulation that vodka needs the last distillation to be 190+. Now, maybe we're talking about class changing, but that's something else that may be legally significant but not actually end product significant.

    Good feedback everywhere else as usual.

  • I was going to ask about this is a different way... so there's a local distillery that claims to pot still their vodka 7 times in order to get their neutral... but even if they are diluting down the their high wines to 40%, they'd never hit 190. How is it you think they are getting away with it?

  • 7 times distilled vodka is BS (here in the US).

    How are they getting away with it? Mostly because no one cares.

    It is unfortunate, and I do have a horse in that race.

  • Honestly, I doubt they are really distilling more than 3 times based on the taste. They've already been caught trying to pass their sourced whiskey off as in-house so there's a history of hinky shit.

    I guess im surprised the TTB doesn't actually check to make sure...

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