Improving a pot still ?

[FreeMountainHermit]

sergiolis ,I'm wondering why you haven't told us about your coolant supply and what It's capable of delivering. Are you on a closed loop or do you have an unlimited supply such as tap water assuming adequate flow of course.

The picture of your rig is fairly typical of what's seen here and your dimension are on the mark so could you tell us more about your cooling limitations, if any, please.

FMH.

[skow69]

Incidentally I only experience huffing at the end of the run .That is when I find backing off water flow helps .

Hmmmmmmmm..... I'm thinking the end of the run is more water rich, and the latent heat of condensation for ethanol is about 850 and for water it is about 2250 so it takes more cooling capacity to collapse the vapor so maybe it can't condense all of it and it oscillates maybe. But why does reducing the cooling water fix it? Do you adjust the heat input also? The output should tale off a little too, but maybe not if you're running very high heat, which I think I remember you might be.

[der wo]

BTW : sergio, all three pot heads I made all huffed , so it would appear to me that condenser size and reduction sizes has little to do with it . Incidentally I only experience huffing at the end of the run .That is when I find backing off water flow helps .

And one of the liebigs was dimensioned sufficient according to the calculator? If no, perhaps it has something to do with the size though?
In my experience huffing slows down the take off speed, the ventilation of cold air or perhaps ethanol-fog from the liebig into the pot consumes heating energy. I would try to avoid this, you spend more money for more energy.
Yes, at the end of the run huffing gets stronger, also in my expierience.

[skow69]

Does reducing the coolant flow fix it?

I'm asking the obvious questions because I've never had huffing.

[Yummyrum]

Incidentally I only experience huffing at the end of the run .That is when I find backing off water flow helps .

Hmmmmmmmm..... I'm thinking the end of the run is more water rich, and the latent heat of condensation for ethanol is about 850 and for water it is about 2250 so it takes more cooling capacity to collapse the vapor so maybe it can't condense all of it and it oscillates maybe. But why does reducing the cooling water fix it? Do you adjust the heat input also? The output should tale off a little too, but maybe not if you're running very high heat, which I think I remember you might be.

I don't know skow69 .....just something Salt bush bill suggested to me and it seems to work .....Yes the output tales off at the end compared to the start , no I don't reduce heat but might consider that , on a strip I do run hard but in reality not more than around 5-10 l/h ....less that 2 l/h on a spirit run ...but then huffin is never an issue

[Yummyrum]

Does reducing the coolant flow fix it?

I'm asking the obvious questions because I've never had huffing.

Yes it seems to reduce it significantly to almost stopping it

I believe its a shock cooling issue .

When you reduce cooling flow , you can feel the condenser length . it has a temp gradient up it from cold at the bottom to hot at the top ....whereas when its huffing with full cooling flow , it cool all the way up it until the top where its hot as

[sergiolis]

Excuse me guys, I'm a bit cofused about huffing and puffing. The symptom is my liebig as if it were a a submachine gun shooting air hits (puffs or huffs who knows)
My cooling system is just tap water. Usually there is no vapour escaping. I try to adjust the minimal and necessary water stream. The inlet of my Liebig is pretty hot (I can't touch it more than a second) and the heat is decreasing along the Liebig but usually I can feel the gradient until the middle of its lenght. I'm sure It's not a lack of cooling problem because even If I increase the water flow-rate the air hits located at the end of the output tube persist.
But the huffing or puffing is bigger at the begining of the run and appears if I push more than 1900W. At the end of the run I can increase the power a bit at about 2000W or a bit more. This part confused me because you are telling just the opposite..
As still_stirrin said I think is a problem of vapour collapsing somewhere. And as you pointed too, likely at the rising section when vapours hits the 15mm tube...

[der wo]

Yes, when you reduce the water flow, that at the outlet water is hot, there will be no collapsing shock and the huffing will stop. But for that you need enough lenght and/or diameter, so it does not escape vapour and the distillate is not too hot. If the condenser is too small, you have to take more water to condense all of the vapour, the temp of the water will be low at the outlet and the liebig will start to dance...

[der wo]

If you have to use much water, most of the vapour collapses at once at the beginning of the liebig. That causes a shock, the liebig gets a kick and starts to swing. The swinging is maintained by further shocks like a flagpole in the wind. Perhaps you have noticed, it's always the same frequency, only the amplitude of the huffing is different with the wattage you put in. Like a bell: you can hit it harder and you get a louder sound but not another frequency.

Edit: Yes I know, it's not something new, what I wrote here.

[still_stirrin]

Good summary der wo. That's what "huffing" is...vapor collapse.

Serg, when you reduce the water flow the still head gets hotter because you're not pulling the heat out as fast. But the product condenser must be sized to condense all of the vapor, or you'll get "puffing"... which is alcohol vapors exiting the product outlet.

So size matters...the heat removal capacity of your condenser and the water flow to balance the input heat. Too much heat and it will "puff". Too much cold water and it will "huff". What you're experiencing may be the limit to your production rate given your heat source and condenser size (and design).

Remember, shotguns have a lot more surface area for a given length. And they also have more vapor flow capacity because of the vapor tube diamater(s). As a result, they are more efficient...at knockdown power given the coolant flow rates.
ss

[sergiolis]

yes I understand the theory, but I can tell you my Liebig is enough efficient because it only needs a very small stream of water to condense all the vapour and it's a 13mm ID, 1 meter lenght... That's why I think the problem is not the Liebig... I'm running right now with a piece of scrubbie at the begining of the liebeg, but is not boiling yet.... let's see

[der wo]

it's a 13mm ID, 1 meter lenght... That's why I think the problem is not the Liebig

Thats long but thin.
According to the calc you need 1.16m length of the jacket with 13mm ID and 1900W. My prognosis is, the scrubbie will fix it. Who wants to bet?

[sergiolis]

Unfortunetly the scrubbie makes no difference. At 1900W the air hits are there again. Water is coming out at 58ºC. I will make some adjustments in the column first and I will report the results.
The huffing, puffing or whatever is called is not regular, it increases the sound and the frequency if i push more power...

[der wo]

Damn, I was wrong. No! Sorry, I hoped the scrubbie would help.
Your still seems to be a different beast than mine. I'm looking forward to your results.

[NZChris]

Insert the scrubbie at the top with a length of wire attached, so that you can pull it down the Liebig during the run to see if you can find a sweet spot for it.

[sergiolis]

NZChris that's a great idea !!! but I think tomorrow I will ask for a budget of the accesories to build a Samohon head type.
And maybe provisionally first I try to change the 15mm tube of the column for a 28mm....
I would like to have a nice head and I'm not too much worried about the price...
Thanks guys!!!!
If you have some new ideas to build a stripping head, please let me know...

[still_stirrin]

...If you have some new ideas to build a stripping head, please let me know...

This right here is a GREAT stripping head.
ss

[CR33G3R]

If the scrubbie didn't fix it then I think that you are having a vapor speed issue caused by the change in size. Hopefully making the change in direction the same size as your column diameter will fix the problem. Like still_stirrin or the PDF that you referenced earlier in the thread.
I have also been able to fix any huffing with a little scrubbie or even not running as much coolant to my condenser.
I hope you find the answer to your question.

[still_stirrin]

...I think that you are having a vapor speed issue caused by the change in size. Hopefully making the change in direction the same size as your column diameter will fix the problem...

+1. I totally agree here CR33G3R. The hot (rising) vapors accelerate significantly in that riser size reduction.

For pot stillheads that do reduce to 13mm, they do it AFTER a full size 90* elbow. And they do it gradually with multiple reducers.

My potstill is 2" (54mm) that reduces to 1" (25mm) after the first bend, not in the vertical run.
ss

[sergiolis]

Your explanations make sense !!
Ready to build a new one...

[Hound Dog]

If you have some new ideas to build a stripping head, please let me know...

The big Dimroth condenser on Lulu doesn't huff and knocks down everything both my elements can throw at her....
http://homedistiller.org/forum/viewtopi ... ilit=+Lulu
3 foot Condenser

Lulu

Pencil thin seam everyone talks about....

[sergiolis]

Ohhh Hound dog, I'd love to build one like yours but 3" is hard to find here...

still_stirrin, Whats the size of your jacket? How long?
How many watts do you through at her?
I like it

[Hound Dog]

All you see in stainless is 2".

[sergiolis]

It's also really difficult to find stainless steel. The only supplier I know only sells 3 meters tube lenght..

der wo, Would you mind to show me a picture of your pot still? The tube size you can get is the same as I can get here...
Thanks a lot !

[der wo]

I have a link in my signature, where you can see pictures. On the first two pictures you can see the interesting parts of my potstill. It doesn't have a rising section, so your potstill is much different than mine. I use it only for stripping. Perhaps I will replace the 22mm-pipe before the condenser with 28mm next year. Currently I only strip whiskey and cannot use full power for this because of foaming and scorching. But next year I will do some TPWs again and strip with 2.6kW.

[sergiolis]

Hi guys, you were absolutely right!!! wonderful! Widen to 28mm has solved sthe problem. I'm stripping at 2600W, No more huffing.

But is happening a weird and new situation to me.
The blue piece over the funnel is a mirror. Even the product is a bit warm but not hot and the condenser water is coming also warm but not too hot, I can see on the mirror vapour condensation. Is that normal?

I've always been distilling in a hotter situation but it is the first time I check with a mirror in that way. Anyway is only hot the first third of the liebeg lenght...

[NZChris]

"... a bit warm but not hot ..." etc. Quoting temperatures would be much better.

[NZChris]

The thermometer at the top of the 50mm is pretty much useless there. Remove it and use it to get some condenser temperatures.

[sergiolis]

The output condenser water is at 56ºC

[der wo]

The condensation on the mirror is not good. You loose a little bit of the distillate. What happens, if you use more water? Does it stop? But start to huff? What happens, if you use less power?
According to the calc your condenser is way too small for 2600W. If more water does not fix the problem, use less power or build a new liebig (I recommend 28/22mm).