Pot Still best height and angles advice please

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Pot Still best height and angles advice please

Postby wow400 » Mon Sep 11, 2017 11:24 pm

Hi guys, I'm building myself a pot still with the initial intention of doing gin.
The plan is to use a ss keg boiler then a 2" column.
The first question is - is there a sweet length? I've heard 8-15"

The 2nd question is - am I best off using a 2" 90° adapter at the top of this column (and then drop it down to 1/2") or just reduce it in size (2"-1/2") at the top of the column and use the 1/2" 90° adapter from there?
Does it make any difference to the process do you think?

My final question is - is there a specific or best angle & length that the condenser (I'll be making a Liebig) and output pipe should be?

It seems that there is so much info out there that it is hard for me to pick out which is best!

Thanks for any help or advice.
Cheers,
Nic
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Re: Pot Still best height and angles advice please

Postby still_stirrin » Tue Sep 12, 2017 5:59 am

How are you heating?

I recommend turning the 90* elbow before reducing because it puts the vapor acceleration pointing away from the riser. But, a 2" elbow is much more expensive than a 1" or a 3/4" elbow (I don't recommend reducing to 1/2" from a 2" riser).

What happens when reducing the pipe size, is the vapor must speed up because you're shoving the same mass flow through a smaller pipe. When the vapor speeds up, its static pressure will drop and the density will decrease, further accelerating the vapor. When the vapor velocity is very fast, you will need a longer Liebig to increase the dwell time in the condenser, otherwise you may get vapor puffing out the product discharge.

But many potstills have been made with small tubing coming from the boiler. It just limits the mass flow capability because of vapor velocity in the tubing. With a keg boiler (2" outlet) you should be capable of good vapor production (depending on how you're heating the boiler), so you will be able to strip quite fast. Keeping the vapor flow through larger piping as long as possible will help this process.

As for the Liebig sizing, 3/4" over 1/2" copper is a good option and for a 2" riser, you'll need at least a 36" long jacketed section (for most common heat sources, that is). Use the calculator on the parent site to determine the minimum condenser size for your maximum heat input. It'll get you "in the ballpark".
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Re: Pot Still best height and angles advice please

Postby Bushman » Tue Sep 12, 2017 7:40 am

I always liked Walking Wolfs balance and design.
viewtopic.php?f=16&t=19610&p=6885210#p6885210
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Re: Pot Still best height and angles advice please

Postby Pikey » Tue Sep 12, 2017 2:29 pm

Yes that's nice - He seems to think he's picking up a little passive reflux and one can see that if there's ant scope for passive reflux, that column angle would pick it up.

I think there is a place for a taller column in a pot still.
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Re: Pot Still best height and angles advice please

Postby zapata » Tue Sep 12, 2017 6:33 pm

I often run with a 3 foot 2" riser. I currently reduce before the turn, used to have one that didnt reduce, dont notice a difference.

All that being said, I dont think there is a "best". I wouldnt spirit run with less than 12", I think some amount of riser is important to reduce smearing from entrained vapor, and maybe a bit of passive reflux. Otherwise I think almost all homescale pot stills are more similar than they are different.

Regarding liebig angle, anything not vertical is best, exact angle matters very little. I played with condesnser modeling software for a bit and saw very little difference in changing angles.
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Re: Pot Still best height and angles advice please

Postby Bushman » Tue Sep 12, 2017 8:18 pm

My main reason for liking it was balance and looks, I don't think any passive reflux would result in anything noticeable.
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Re: Pot Still best height and angles advice please

Postby Truckinbutch » Tue Sep 12, 2017 8:20 pm

You should consider tailoring it to your needs and keep vapor speeds in mind . I go 2" to the turn and beyond . From there I reduce to 1" into and out of the thumper and reduce to 1/2" at the Liebig condenser connection . That's been working well for my pot still for several years . Condenser angle is about 38 degrees right now as a matter of convenience for me .
Design heights and locations to be user friendly . If you stay with this hobby you are going to be spending a lot of time with your new made friend .
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Re: Pot Still best height and angles advice please

Postby wow400 » Tue Sep 12, 2017 11:31 pm

Thanks for the info and ideas guys!
I'm planning on a 50l / 13 gallon SS keg with 2 electric elements - a 2kw & a 3kw. The 2kw just to help get it up to temp then unplug leaving the 3kw element controlled by an SCR controller.

I saw the Calc for the minimum length for the leibig condenser but I wasn't sure if there would be any issues making it longer?
Great to know the condenser angle makes little difference so I'll do as suggested and work it all out so that it's at a convenient height for operation.

Thanks again for the info and help guys :thumbup:
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