How does a Thumper keg work?

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How does a Thumper keg work?

Postby Dolmetscher » Sat Nov 10, 2012 10:59 am

So, I understand how a pot still works.

And a reflux still is just a pot still with a long column, with "something:" rocks, perforated discs, copper webbing, etc. in the column so that the water "sticks" to the material and drips back into the still, and a more pure ethyl alcohol makes it through the material and into the worm to condense back into the liquid.

Now, I've seen all this stuff about "thumpers" or "thump kegs." I've never seen one in real life, so... if you will indulge me... I'd like to tell you guys what I think they are, and you tell me if I've got it.
A thumper is a vessel, partially filled with some inert liquid (water, extra mash etc.). The still's head has a pipe that comes out of the pot, and goes into this thump keg, and the tip of the column is submerged in the liquid. So, the alcohol vapors travel through the column and into the water inside the thump keg, where they emerge as bubbles of hot alcohol steam. The bubbles rise through the water and pop, releasing the alcohol into the keg, which then travels through a "release pipe," that goes into a worm/condensor... and comes out as a high proof alcohol. The theory being that the water, being cooler than the steam, condenses what little water is in steam, allowing for a more pure alcohol. It most likely also somehow "scrubs" the steam of some impurities, and heavier molecules... kinda like a water-bong in college. :-P

Is this true? If not... please set me straight.
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Re: How does a Thumper keg work?

Postby Richard7 » Sat Nov 10, 2012 11:45 am

Dolmetscher, from what I understand that is about half of it. The thumper is also heated by the steam and becomes a "second boiler" kind of like two distillations for one. Your description of the flow sounds spot on.
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Re: How does a Thumper keg work?

Postby Usge » Sat Nov 10, 2012 12:19 pm

Not exactly...but close. A thumper is a parasitic secondary boiler. For it to work like it traditionally should work...you need to start with some alc in the thumper (ie., wash or low-wines, feints, etc). You only start with enough to cover the input tube at the bottom. The alc vapor coming over into the thumper condenses as it bubbles into the liqiuid which fills the thumper, increases the abv of what's in the thumper and heats the solution at the same time. Remembering your theory...the higher abv solution in the thumper will now have a "lower" boiling point than the pot that is driving/feeding it. This is what you want. Once the solution in the thumper heats to it's somewhat lower boiling point..it will pass off higher proof alc vapor through the output tube where it goes to condensor. The pot continues to heat and feed and drive the thumper. It is in this way that it's a secondary/parasitic boiler.

Think of it as one giant bubble cap plate. What you are looking for using a thumper is not double proof. It should start at slightly higher proof, but sustain it longer through the middle of the run (instead of it dropping linearly as it normally does on a potstill run). It's about equivalent of 1.5x distilling. It also depends a lot on how much volume you have in your pot (how much alc) as well as the proof, and what you start with in your thumper. Starting with water in your thumper means...it has to fill, raise the abv, and heat up to a higher boiling point before it will start working and kick in. It takes longer to start, and it uses more alc from your pot to get it primed and online. You can also use "Flavorings" in this way. In my experience with them...they work better when running off a pot full of low-wines than it does when trying to single run wash through it and starting with some alc to prefill the thumper (ie., wash and/or lowwines). YMMV.
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Re: How does a Thumper keg work?

Postby OBX Phantom » Sat Nov 10, 2012 12:49 pm

+1 Usge

I use a thumper, and Usge is absolutely correct, a thumper really doesn't raise your ABV more than 1 or 2%, but it does however work as more like a filter to get more of the impurities out. And it also keeps your ABV more consistant through the run then drops off more abruptly towards the end. He is also right about it doing better with higher ABV. runs. so you still need to do stripping runs, and save up your low wines and feints for a spirit run through the thumper.
If you do a search you will find a thread called "adding a thumper" that I put up on here about a month ago. In it you will find no.s from my spirit run, and also more explanation.
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