StillDragon® Community Forum


Be part of our community & join our international next generation forum now!

In this Discussion

Second Column on a Thumper

I am designing my vodka column to cope with a low ceiling (11'9") and came up with what might be a looney idea. I am very interested in any thoughts you all have.

The goal is to be able to charge my 300 gallon still with 270 gallons of all-grain wash and go straight to a neutral 95+ in one run, and in under 12 hours, not counting warm-up.

I would run an 8" SD column on top of my 300gal boiler - 4 bubble plates, then a packed section, then dephlegmator. After dephlem, 180 bend, taper down to 2" TC pipe, and run straight down into the top (the fill port) of a smaller pot/thumper back down at floor level. The thumper will be filled with water sufficient to cover its electric immersion element. The thumper has its own 4" SS wool packed column about 100" tall, dephlem, condenser. The piping between the first dephlem and the thumper would be well-insulated, as would the thumper and packed column sections.

I have a controller that will adjust the 8" dephlem on the big still to maintain a set temp in the vapor above the dephlem (around 175F, but will require experimentation). I'd also maintain the water temp in the thumper at a set temp (somewhere between 173F and 212F, but will require experimentation). The idea is that vapor doesn't condense (or doesn't stay condensed for long) in the thumper, but is fed into the second column with already high ABV, and at a very even and controllable temperature. There would be a lot of experimentation required on how to run it - heat input to big still, output temp of first column, temp of thumper water...

Is this nuts? Do you think the second column has to be 8" as well, I was going to use 4" there because I already have it, but I'm not sure how much it will constrict my output rate.

Any thoughts are appreciated.


  • edited January 2014

    I'm probably wrong here but wouldn't it be a concern that the water in the thumper with it's own element becomes saturated with alcohol and there be a potential for 160+ proof alcohol being boiled in the thumper and creating a dangerous situation?

  • A thumper needs pressure to drive it, you would have to run your column flat out to drive it.


  • Wow, @SammletonDistilling, an amazing idea you have.
    You are essentially creating a second boiler. As @unsub mentions, you'd need to take precautions that the second boiler's element can never be dry-fired - it must be kept covered by liquid.
    I think by reducing to 4" on the second column you are restricting the 8" column.


    Maybe you don't need to thump it.

    second boiler.png
    327 x 348 - 6K
  • Do you think it needs a lot of pressure even with the vapor entering above the liquid level of the thumper? it wouldn't have to push through liquid, and the heater in the thumper gives any extra power to drive column 2?

    Good point that liquid level and proof in the thumper is something to think about and watch. I think as long as the element is submerged, there is no risk of auto-ignition, just vapor that could do that, but I'll research that more

  • Its my understanding that the pressure on your main boiler will be related to the sum of the liquid levels on all of the plates, and in your case the height of the liquid above the inlet tube should you plan to thump the second boiler.
    By not thumping the second boiler you can decrease the pressure.
    By adding power to a second boiler the math gets more complex and I don't understand it.

    I really think you are on to something here.

    It would be tricky to master this still. What to charge the second boiler with? When to add power to it? Does the second boiler when powered add back pressure to the first column? If so, thumping the second boiler may actually be a good thing.

  • If I leave off the thumper, its pretty much a side-by-side column, but then I think I need a drain line to the pot - which then means it has to be higher than the liquid level of the big pot, right? Or is there another way to get column two lower than the big pot without a pump return? The other idea behind it - which may or may not make sense - stems from the findings others have had about using deep-downcomer bubble trays below packing to manage the heat a bit before it hits the packing, maximizing the packing. I thought this might allow me to not only up the abv before it hits column 2, but to precisely control the vapor temp as it enters. The thumper might not need much heat at all if well insulated between defleg 1 and the thumper - maybe I can heat the thumper externally, with a band heater or similar...

    I think you're right though, the 4" second column would probably be the choke point. I thought since column 1 might have to run at higher reflux than column 2, since it is stripping more out and is shorter, the amount of vapor let through might be manageable by the 4".

  • Yeah, this would be tricky to get to work right for sure - if its possible at all. As I think about it, the smell of burnt toast is coming from my ears... Backpressure from the thumper to column 1! Good point. I have no idea what effect that would have, or what to do about it...

  • I can't see what you are trying to achieve, a plated column will give you 90+abv' what more can you achieve by adding a thumper as a thumper is generally used to raise the abv from a pots till.


  • Your idea of the second boiler is the only way I can see to have the second column be below the fluid level of boiler 1. Pumping the reflux from column 2 to column 1 sounds tricky.

    I'm not sold on very deep fluid levels on a plate. You are only going to get one distillation per plate whether the fluid level is 10mm or 1 meter deep.

  • It's the second column that's the main point i think Mike.

    The extra element sounds like a recipe for BOOM to me. An overflow with anti siphon and a small ignition proof pump sounds a much better idea. Safer, cheaper, simpler and controlable.

    It may take a while for the second tower to get up to temp and i think the amount of vapour that you are going to need to drive it (without a reboiler) will be beyond what the plates can handle.

    I'd speak to a distillation consultant about whether what you want to do is possible. We can supply the modular equipment but it sounds like a job for an engineer to design it.

    StillDragon Australia & New Zealand - Your StillDragon® Distributor for Australia & New Zealand

  • The ultimate goal is to get 95+ neutral at reasonable speed in one run, but with 11'9" ceilings. I'm misusing the word "thumper." Its really just a side-by-side column, but with with heat added at the bottom of column 2 to avoid having to put a return line to the main pot. I want to do that so column 2 can start lower than the liquid level in the main pot. I thought rather than heat the metal surface at the bottom of column 2, to reboil any condensed vapor, I'd heat water at the bottom of column 2, because it would be easier to maintain a stable temp, and would be safer. So if all I can get off of column 1 at reasonable speed is vapor at say 180F, then I hold the water in the pot at the bottom of the "thumper" at 180, or maybe a little above. The vapor does not bubble through that water, it enters above it. The goal is to get the vapor from column 1 to column 2 at a set temp, so it acts like one continuous column. Fair enough about the safety concerns though, I'll clear anything I do with an engineer first. Kinda fun to ponder regardless though!

  • image

    bain marie reboiler.png
    327 x 348 - 7K
  • Aahh i see what you are saying, but with a RC on top the water will not stay as water for long, regardless of dicking round with temp control. The reflux has to drip out the bottom and it will be at least as rich as the vapour feeding it (probaly over 95%).

    I don't mean to be picking the negatives, i'm just not smart enough to see the workarounds.

    StillDragon Australia & New Zealand - Your StillDragon® Distributor for Australia & New Zealand

  • Brilliant! A small Bain Marie pot at the bottom of column 2, but with no water in the pot itself. Keep the water in the jacket at 210 (or maybe less, depending on heat transfer efficiency), it will boil off the reflux that hits the bottom of column 2. I don't think there would be a safety issue either. Backpressure remains a question though. Punkin, you're totally right. With my original idea, reflux of column 2 would end up in the water. It doesn't give me a safety concern if there is enough water, but its goofy in its end result. If I kept that water at 180 or whatever, I would have a bunch of alcohol left in there at the end of the run. I could then heat up the thumper and run it off, but thats getting really goofy with cuts... I need another martini.

  • Yes, backpressure seems to be the wild card but the vapor will take the path of least resistance which will be up column 2.
    I don't imagine the Bain Marie (BM) will need much energy to operate so any backpressure to column 1 should be minimal.

    I do imagine any juice left in the BM pot, after the run, if there even is any, would be nasty.

    Certainly the BM could be operated to allow fluid to build up or to be instantly boiled off.

    Perhaps a more compact, though less modular, approach?


    bain marie reboiler - Copy.png
    327 x 348 - 8K
  • There are a few issues to think about that you may or may not, have already considered.

    1. I don'think you need to heat the second boiler at all. There may be sufficient energy in the vapour from the first column to deal with that. Balancing the requirements for the vapour speed in both columns might be an issue.

    2. You must consider the VOLUME of column bottoms generated by the second column during the course of the run. This is relatively easy to calculate and if your secondary boiler is not big enough, you will need an overflow or pump system to deal with it.

    If a conventional column is opperating correctly the column bottoms are very low proof liquid that can be disposed of, instead of sending it back to the boiler. With the split column this may not be the case. You should expect to reboil the bottoms, or to send them back to the primary boiler for reprocessing

  • @Myles, my drawings should have been put in the Loony Bin thread but it started here :))
    I agree with you, some of what gets processed Down the column should be kept down - otherwise everything that's pushed into column 2 must be taken as product. Well, that's not good.

    Column 2 will always have a very high ABV vapor and plate fluid but the enrichment/purity process depends on sending water and lower alcohols back down the column as normal reflux. Some of this fluid should be drained from column 2 for it to operate properly. On an 8" plate we're talking liters per minute but we don't need to return all of that to the main boiler (or simply collected for another run perhaps?).

    After column 2 gets up to operating temperature the energy in the vapor from column 1 should be enough to drive column 2, with a little help from the BM. The BM is to push most, but not all, of the refluxed liquid back into vapor to be reused by column 2, in my untested opinion. We are all speculating about something that none of us has ever seen before - nothing new there, huh?

    I think this could actually work.

    As long as there is reflux falling into the BM pot, I believe, MOST of it is very high quality alcohol that could be heated to keep it in play instead of being sent back to the main boiler. And it won't take much additional heat to do it.

    A balance would need to be found by the operator to allow a small portion of the reflux from column 2 to be removed to keep column 2 'healthy'.


    bain marie reboiler3.png
    317 x 331 - 7K
  • @Myles said: If a conventional column is opperating correctly the column bottoms are very low proof liquid that can be disposed of, instead of sending it back to the boiler. With the split column this may not be the case. You should expect to reboil the bottoms, or to send them back to the primary boiler for reprocessing

    The liquid in the bottom can only get as low abv as the vapour pushing in to my understanding? Oter wise it would be enriched by that vapour?

    I'm not up much in the theory and maybe i should keep out of a discussion that hurts my brain with concepts i don't understand.

    StillDragon Australia & New Zealand - Your StillDragon® Distributor for Australia & New Zealand

  • Not correct Punkin. By deffinition if you have a vapour and a liquid at the same temperature at any point in the column, the liquid has a lower ABV than the vapour. In the ideal column, the volume of reflux that manages to get to the bottom of a packed column is significantly lower than the volume produced by the dephlegmator. Part of it has evapourated on route down the column.

    The ideal situation is when the reflux liquid reaching the bottom of the column is completely devoid of volatile components. Not achievable in practice (unless there is packing BELOW the vapour injection point) as some of the volatiles in the vapour disolve into the reflux liquid.

    That is a simplistic way of looking at it but it does help to describe the process. Reality is more complex.

  • You're right, reflux off column 2 will have stuff we have to end up getting rid of - either back to the main pot, out to a separate container, or it remains sitting in the thumper at the end of the run. To put some numbers in to play with: if the initial charge is 250 gallons of 10% abv, and it comes off column 1 at 90%, then out of column 2 at 95%, column 2 will have had to strip out about 2.8 gallons of water/other stuff. If we can just drain essentially everything out of the downcomer of the bottom plate of column 2, then Lloyds last drawing is the answer I think. How much good ethanol would we lose out of that though? I'm not sure how to figure that out. If that would be too much loss, I can't help but come back to the original idea of a water-filled still as the pot at the bottom of column 2. This is what I'm thinking: I hold the water in the pot at say 208, and the heat input stays at the level required to maintain water at 208. Reflux from column 2 drips into the 208 degree water and mixes. When the abv gets high enough in the mix, the boiling point will drop below 208, and it will boil off until it reaches 208 again and plateaus. I'd just accept that the 10 gallons or so of 4% abv in the pot at the end of the run is a loss. Is it that simple? I'm guessing not...

  • I'm certainly not in a position to argue with you Myles. If you say the liquid that makes it's way from the bottom plate after coming in at 90%+ is devoid of alcohol enough to warrant disposing of it then so be it.

    StillDragon Australia & New Zealand - Your StillDragon® Distributor for Australia & New Zealand

  • @SammletonDistilling I'd think the distillate removed from the BM on column 2 would be very high proof and could be considered as feints to be added to the next run.
    It was high proof enough to escape from column 1 but not good enough to be collected by column 2. I also agree the discharge from column 2 would be gallons and gallons.

    I like your idea of pre-charging the BM pot with water. Thinking we could consider the BM pot as an additional plate or re-distillation. I know the vapor does not bubble through it but the action of the reflux being reprocessed there should account for at least a partial plate?

    This split column BM idea that we are kicking around has a few similarities with a continuous still.
    But how about a simpler concept...


    3 column.png
    317 x 331 - 2K
  • The boilers all have 2" spare ferrules in place already.....

    StillDragon Australia & New Zealand - Your StillDragon® Distributor for Australia & New Zealand

  • Interesting. That pretty much a conventional side-by-side, but with a little heat from the boiler on the bottom of the second and subsequent columns. Certainly simpler and more proven. However, no control over the heat applied to the subsequent columns, and it doesn't get the other columns starting down below the pot, to maximize a low ceiling. For me, the kicker is that it won't really work on my pot. I thought about using a stainless IBC, where the flat top would be perfect, but mine will be a copper dome. It will probably make sense for me to first just see how the one column to the ceiling works, then add a conventional side-by-side with return to the boiler and see how that goes. Do you guys know of a successful use of an SD 8" column as a side-by-side setup? I'm just wondering if all the components are balanced correctly for that. I'd probably do 1 bubble plate, then 60" of ss wool packing for each column, with a defleg on each column. I have about 50kw in the 300 gallon main pot. My defleg cooling water is about 55F.

  • @awesome has an 8" Crystal Dragon configured for side by side but i don't know how he's going with getting it set up. He has so many projects on the go.

    StillDragon Australia & New Zealand - Your StillDragon® Distributor for Australia & New Zealand

Sign In or Register to comment.