Robo-Still Inline Thumper Build

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MidnightThunder
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Robo-Still Inline Thumper Build

Post by MidnightThunder » Sat Sep 05, 2020 9:20 pm

Hey guys, here is the start of my newest build of an expansion head that I will can a giant bubble-cap for to run as an inline thumper to pre-charge my 4" VM column, with a combo of packing and plates.

The boiler on the bottom is 18 gallons including the volume of the cone leading up to the still head which is 7.75 gallons itself. Thinking I will have to make a 2" feed going to what will probably resemble a 4" version of a Pro-cap to take full advantage of the large volume of this head.

Looking for feedback from anybody with experience running an inline thumper under a reflux column of any variety, and what kind of increases this should yield on speed. My understanding is that it should yield a pretty significant increase in rate of production.


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silverbean
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Re: Robo-Still Inline Thumper Build

Post by silverbean » Sun Oct 11, 2020 4:04 am

Wow that certainly looks impressive. Sorry I have to experience to help, I didn't even know you could run a column off a thumper. I thought thumpers were only useful on a pot still. Looking forward to see how it turns out and the results you get.
Happy Stilling.

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LWTCS
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Re: Robo-Still Inline Thumper Build

Post by LWTCS » Sun Oct 11, 2020 4:12 am

Good looking outfit.
Do you have a specific question beyond speed?

What you are essentially doing is shifting alcohol out of your primary kettle in order to feed your column.

The thumper only represents one plate value so doesn't get much credit from the "theoretical plate" guys.

The real benefit is two fold.
The liquid bed's first responsibility is to condense incoming vapor. Therefore the thumper is a condenser,right?
And the larger liquid bed in the thumper has the ability to absorb more heat input compared to the much smaller liquid bed on a plated column. Make sense so far? Bigger condenser absorbs more heat. Simple.

And since the cooling medium in this condenser is alcohol, the flash point will be determined by the abv of the cooling medium.
Let's recap.We will shift as much alcohol as possible into the oversized plate in order to absorb what will eventually become un needed heat at the top of the apparatus. The thumper protects the column from unneeded heat. You'll be able to throw more heat at the system because the thumper will protect the column. Does that make sense so far? That is point #1

Point #2, Part A:The size of the thumper will prevent alcohol from draining back into the primary kettle. This adds efficiency since additional BTUs don't have to be produced to flash alcohol that has already been shifted out of the primary on the first go round.
Part B: Not only does alcohol not return back to the primary, but water also does not get returned to further dilute any remaining alcohol in the primary.
All of this adds to efficient behavior.

Here is the problem: in the beginning of the run (reflux period) the abv will only enrich. But at some point when refluxing, liquid levels will eventually accumulate and start to drain back to the primary when collecting. Soon after the enriched liquid in the thumper will become less and less enriched. Therefore, it is important to initiate collection of product at an optimal time before the enrichment process reverses itself if you see my meaning?

Keep in mind none of this has anything to do with making a good spirit (though you absolutely can). This is simply building a hot rod and clocking ridiculous collection speeds.
Trample the injured and hurdle the dead.

zapata
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Re: Robo-Still Inline Thumper Build

Post by zapata » Sun Oct 11, 2020 2:32 pm

I don't know that I agree with the heat statements as anything other than metaphor. Other than radiation from the surface area, all the heat energy entering a thumper leaves it almost immediately once up to temp. The energy is just transferred to proportionally more volatile vapor and less volatile liquid. But it's the same energy balance as a pot boiler with the same surface area. The point of a thumper is to condense, sure, but also to vaporize, and the energy transfers perfectly.

Specifically for running under a column there are 2 useful aspects not specifically about energy or production rate.

1. Packing physically works better fed with higher ABV vapors, especially over about 40%. Water likes itself too much and clumps together into channels in the packing wherever in a column strength is below that. A thumper or plates will feed the column with higher strength vapor further into the run. Look at a phase diagram. If running a column straight off a boiler then the bottom of the packing starts being too wet when the boiler charge is down to about 5 or 6%. But step off one plate, and boiler at ~1% is still feeding the thumper ~6%, which feeds the column ~40%. (This is just illustrative, running a batch still is dynamic and nothing is ever perfect) This probably isn't a huge effect for a tall column, but probably relates to losing about 1 or 2 theoretical plates halfway through a run from wash, from low wines there probably isn't much in it at all since you are probably into tails before the boiler is that low.

2. An inline thumper provides space for congeners of moderate volatility. A fair number of congeners get concentrated at 20-40% ABV. In a column there just isn't much physical room, so they end up making that section of the column less effective at separating ethanol. But note that for just one thumper / plate, this will only work in the beginning, as the abv drops in the thumper they are pushed into the column anyway. 2 plates do a very good job at this, as any flute user knows. It's why people say "flutes hold back the tails". A 4 plate still runs clean, because the mid boiling congeners have room to concentrate, even toward the end on a perf plate when the bottom plate dries up, distillate can still be clean because the "tails" are still stuck in the 2nd and 3rd plates. I don't think plates magically "hold back tails", they simply provide a convenient volume to hold them.

I've been looking at European and Russian hobbyists, and a lot of them do a reservoir at the base of a column that doesn't even thump. It just catches reflux and overflows. There is still energy / mass transfer to it via the walls because it dries up toward the end of the run, and so it provides both functions above. IDK why they wouldn't just make it thump though, clearly intimate vapor / liquid interaction is better than indirectly transfering heat through a tube.

To me a reflux column runs notably better and more steady fed by a plate or 2. It's not life changing, but is real. I used to have a thumper with a much larger holdup that I played with a bit, and determined that if there was anything to larger volume I couldn't see it. A shallow depth typical of most plates does the job, at the hobby scale the absolute volume of congeners is tiny. And the benefits are lost if the height makes you shorten the packed column, other than the first Theoretical Plate fed low strength vapor, packing will be a better use of height if you have low ceilings or tall rigs.

You could of course use the slight gains of 1 and 2 to bleed the edge and try to run at hot rod speeds. Personally I think the utility is to stay at speeds reasonable for the rest of the rectifying work and just enjoy the stability of a column that doesn't decrease it's effective rectification halfway through a run.

All that nerdiness aside, I think aesthetics matter very much, unique personal gear matters very much, and I like the looks of it. I would smile every time I used it.

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LWTCS
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Re: Robo-Still Inline Thumper Build

Post by LWTCS » Sun Oct 11, 2020 4:07 pm

With respect to temps, my comment was to illustrate
(weather I'm explaining correctly or not) that the larger liquid bed below the column allows the base of the column to have cooler temps, and run more stable with better separation as Minime's experiments proved.
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zapata
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Re: Robo-Still Inline Thumper Build

Post by zapata » Sun Oct 11, 2020 7:44 pm

Gotcha. Yeah, that's definitely true. A thumper will absolutely cause lower temperatures in the column by feeding it consistently higher strength (cooler) vapors, right up to the point it's thumped out. Exactly as you said. I was probably reading with my spectrum brain where energy is not temperature :)
Cheers

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