2" vs 3" column on a CM still

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2" vs 3" column on a CM still

Postby jackfiasco » Wed Aug 02, 2017 5:41 pm

After using an 8 gal brewhaus cm still with a 2" column for several years, I decided to go larger and recently got the 15 gallon version with a 3" column. Everything I have read has said that a 3" column should be able to run roughly twice as fast as a 2" column, so I figure with double the charge, double the heat (2 x 2000 watt elements), and the increased speed, a run shouldn't take much longer than it did on the 2", but yield around twice as much.

Well I've only run the 3" a couple times now, and I don't know what I'm doing wrong, but it doesn't seem to output any faster. I get it close to boiling then turn off one element and control the other as usual. If I crank the heat to try to get it to go faster, the proof drops way too much. I am just running it as a pot still, not using the CM, as I mainly do stripping runs and then rerun them with botanicals to make gin.

Is there something I am missing or should be doing differently with the increased column size?

The only other explanation I can think of is that my wash was just lower than usual in abv. I switched to larger fermenters as well and just increased the volume of the usual Deathwish Wheat Germ recipe I always use, but maybe I did some math wrong and watered it down too much? I didn't take the starting gravity because I've made that wash a hundred times or so and after a while I stopped bothering to measure. I will measure the next one though!
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Re: 2" vs 3" column on a CM still

Postby shadylane » Wed Aug 02, 2017 6:11 pm

jackfiasco wrote:.....Everything I have read has said that a 3" column should be able to run roughly twice as fast as a 2" column, ....I am just running it as a pot still, not using the CM, as I mainly do stripping runs and then rerun them with botanicals to make gin.....
Is there something I am missing or should be doing differently with the increased column size?
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Re: 2" vs 3" column on a CM still

Postby jackfiasco » Wed Aug 02, 2017 6:13 pm

Could you tell me what you're getting at please?
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Re: 2" vs 3" column on a CM still

Postby Klein » Wed Aug 02, 2017 6:27 pm

jackfiasco wrote:Could you tell me what you're getting at please?


There will be no difference from 2" vs 3" in a pot still.
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Re: 2" vs 3" column on a CM still

Postby shadylane » Wed Aug 02, 2017 6:46 pm

jackfiasco wrote:Could you tell me what you're getting at please?

My Bad, all I managed to post was the quote part :oops:
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Re: 2" vs 3" column on a CM still

Postby jackfiasco » Wed Aug 02, 2017 6:46 pm

Not according to prairiepiss and multiple other users on this thread:
viewtopic.php?f=15&t=32445

why would there be no difference?
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Re: 2" vs 3" column on a CM still

Postby bluefish_dist » Wed Aug 02, 2017 7:35 pm

Unlike a column still where the diameter is highly related to output, a pot still does not seem to be as effected by vapor speed. Take off is effected by power input on a pot still, but no rules like for a column, everyone usually says find the sweet spot. Not necessarily bad advise as I recently talked to another distilled and he runs a strip and spirit run with 4 plates while I run a single spirit run with 2 plates. Very different ways to reach the same goal.
I have never found anyone who has discussed hard facts of what factors control sizing vs output on a pot still. Ie boiler size, heat input, output size vs takeoff rate. I have little experience with a pot still, but would like to learn more when I have time.
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Re: 2" vs 3" column on a CM still

Postby jackfiasco » Wed Aug 02, 2017 9:05 pm

Thanks for your reply. I'll try again with a properly charged boiler. I think my amount of alcohol in there was too low to begin with, as I didn't get nearly as much out, at any temp, as I should have with 15 gallons in. Hopefully then I'll find the sweet spot. We shall see..
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Re: 2" vs 3" column on a CM still

Postby still_stirrin » Thu Aug 03, 2017 4:22 am

More heat input, regardless of the size of the boiler, will produce more vapor faster. And when the boil is rolling faster, it will carry not only more alcohol, but also more water and congeners. So, the faster you run a potstill, the more it will smear and likely the "off pipe" proof will fall because of it.

So, you did not say what your collected proof was (throughout the run). Nor did you tell us the potential alcohol, that is, the OG and FG of the ferment and the size of the charge.

What I suspect is that you stopped the run too early because the proof off the spout was lower than what you got with your smaller still. In a stripping run you need to strip all the alcohol from the charge, so you need to run it deep into the tails. Then on the spirit run, throttle that big sucker back so you can get better separation between the fractions.

Your impatience will reveal itself in your product. Don't be in such a hurry to produce a big jar of spirits. You've got to invest time...it's the hardest part to get into the bottle.
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Re: 2" vs 3" column on a CM still

Postby Klein » Thu Aug 03, 2017 5:42 am

jackfiasco wrote:Not according to prairiepiss and multiple other users on this thread:
viewtopic.php?f=15&t=32445

why would there be no difference?


The power input will make the difference in a pot still,

if the only thing that changed during the run was the 3" column and everything else stayed the same then the vapour speed in the new (larger) 3" section will be slower. While the output will be the same.
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Re: 2" vs 3" column on a CM still

Postby shadylane » Thu Aug 03, 2017 7:30 am

jackfiasco wrote:.....Everything I have read has said that a 3" column should be able to run roughly twice as fast as a 2" column, ....I am just running it as a pot still, not using the CM, as I mainly do stripping runs and then rerun them with botanicals to make gin.....
Is there something I am missing or should be doing differently with the increased column size?

Is the question about a pot-still or a CM still :?:

I've done a few experiments with unpacked columns on a potstill.
More reflux made it run slower, without significantly increasing the ABV
A bigger column will dissipate heat and increase passive reflux
Long story short, a bigger riser will slow down a potstill
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