Vapour Speed

[devotus]

I have tried to clear this up in my head but would like a bit of help from the more experienced and technical minded here if possible.

My common sense tells me one thing but due to trying to study from various resources the subject has become confusing.

The rule is vapour speed must be between 12 and 20 inches per sec and this is determined by diameter of column and watt input.

My question is;

Is this simply a difference in rapid boil and gentle rolling boil of wash?

As a wash will boil in that temp range between water boiling point and ethanol boiling point regardless of heat thrown at boiler. Is vapour speed then determined by how rapidly the wash boils?

In my mind I can't think of any other logical answer but my mind isn't that large and has holes in it that the Queen Mary could sail through, so perhaps there is something more to this than I see.

Cheers

[R-sole]

Sounds about right to me.

[cdbrown]

Is the vapour speed an important factor with pot stills?

Using the typical 2" column ontop of a keg boiler, the input power is a low 1200W to get between 12-20. I plan on using either the 3-ring burner with MP adj regulator or 3.6kw element (controlled by PID). Would take 30mins to get to boil with 3.6kw or 80mins woth 1.2kw.

I know that a fast, vigorous boil is good for a stripping run - going fast and hard - and then slowly for the spirit run, but its there a way to measure it? Would a temp gauge at the top of the column help at all or is it all based on the rate of product coming out.

Another thing - the vapour speed would affect the cooling ability of the leibig so do you try and make the leibig long enough to suit the strip run so that it's all liquid and no steam coming out the end?

[R-sole]

Yes, build the still so the condensor will cope with any heat you intend to throw at it.

Adjust your spirit run to suit yourself by trying from the worm at different takeoff rates.

I've found that a takeoff speed around 4l/h gives me a result that is slow enough to not be dragging tails through the run, but fast enough not to be introducing a hot bite to the spirit.

[cdbrown]

Yes, build the still so the condensor will cope with any heat you intend to throw at it.

Adjust your spirit run to suit yourself by trying from the worm at different takeoff rates.

I've found that a takeoff speed around 4l/h gives me a result that is slow enough to not be dragging tails through the run, but fast enough not to be introducing a hot bite to the spirit.

What is the worm? Is that to do with adjusting the angle of the leibig. more horizontal increases the hold up time allowing to cool more. Or is there a valve I should be placing in the pipework somewhere.

[SBB]

Would a temp gauge at the top of the column help

It would be of NO use at all for that purpose.......no matter how much heat you are pumping into the bottom of the still its not going to change the temp at the top. The vapour temp will do its own thing and change only as the % of ALC to water in the wash changes.

[R-sole]

Sorry, substitute the word 'worm' for the word 'outlet'.

[Sam.]

Would a temp gauge at the top of the column help

It would be of NO use at all for that purpose.......no matter how much heat you are pumping into the bottom of the still its not going to change the temp at the top. The vapour temp will do its own thing and change only as the % of ALC to water in the wash changes.

using a big burner will increase the temp at the top just did 5 minutes ago started running it real slow then cranked it up a bit because I am doing a stripping run and the temp definitely increases by a few degrees. I know I don't need a thermo on my pot still but I like it anyway

[Sam.]

I should elaborate. Vapour speed? This seems like a term more suited to reflux columns and not pot stills. As I understand it if you want to have the most efficient still ever known to man then you need to be able to calculate the volume of wash and percentage of alcohol in the wash and the heat input into the boiler and the number of theoretical plates in your boiler and then how the packing is in there if you need centering rings or if your running a plate set up .....ya da ya da yda...

I just run a LPG burner, I have no fucking idea how many watts I am putting out so every other equation doesnt mean shit to me :laughing-rolling:

CD I do know however that off a pot still you are not so worried about the vapour speed be more worried about the take off rate and how it tastes :handgestures-thumbupleft:

Not sure about the element set ups with the controllers but I still do like my temp gauge at the top with my burner to have a visual as to how far along it is.

Hope some of this makes sense....... :text-lol:

[Highlander]

Hi Guys,

New to the forums and your vapour speed thread has me interested. For me with most things the "rules" are not rules they are guidelines. Safety always but come to your own conclusions.
with regard to vapour speed look at the equipment that has been used in the past and is available now even for pot stills. Kentucky cap and Onions are good examples.
Look at your garden hose big hose little outlet water goes a long way.
Consider what you are doing and work through it.
Knowledge
Understanding
Application
Adaptation.

[Arismac]

:text-+1:

[woodduck]

Hi there Highlander,

Sounds like you have a bit of knowledge. How about popping into the welcome centre and tell us a bit about yourself.