Reflux return point

[reflux]

What happens if reflux in a VM still is returned half way down the column instead of at the usual top point?

[canadianmoonshiner]

Not certain, but I think the top half of your column would be wasted.

[Prairiepiss]

Take a look at this thread. His reflux point is below his take off on a VM. And he is not happy with his results. He has another thread too you mite go find it and read through it also.

[Manback]

What thread prairiepiss?

You want your return below your VM take-off ideally.. but not half-way down the packing o_o

On top, to be sure.

[Prairiepiss]

Sory forgot to add it.
http://homedistiller.org/forum/viewtopi ... 15&t=21614

[LWTCS]

Mr Nixon has a conceptual drawing circulating that shows reflux being re-introduced to a much lower elevation on the column.

Quote from the paper:
So what would be the consequences of introducing the reflux at the bottom of the column instead of
the top? In the "liquid reflux" case, the strength of the liquid coating most of the packing gets a boost at the top, but that tails off as you go down the column until it's lowest at the bottom. With a"perfect" column, the strength will have tailed off to the same strength as the vapour coming off the liquid mix in the boiler, but in a less than perfect world you can expect quite a lot of fairly high strength liquid to be dumped back into the boiler, where it will be diluted and reboiled to produce a vapour that's lower in strength.
In contrast, the vapour entering the bottom of the column with "vapour reflux" will have a higher strength than that produced in the boiler alone, and this increased vapour strength will boost the strength of everything higher up the column … and this will boost the strength of the liquid being refluxed, etc. etc. etc. The column will therefore have a much smaller gradient of strength to deal with, so it has an easier job than with "liquid reflux".

[Manback]

LW - could be way off base here but - that's at the bottom of the column based on the excerpt?

What about half way up? That leaves you half-way between the two methods.. seems like it would be problematic to me?

I'm probably wrong though.. I'm okay with it!

[LWTCS]

I can't speak for the design (of which I can't figger out how to post the diagram).

But there are similarities to my still behavior described and I know for fact to be quite true.

[Prairiepiss]

Forgive my ignorance! I'm still learning about VM stills. But how are you going to channel the reflux to the middle of the column on a VM still. I can see it on a LM but I am just not getting it for a VM. Are we talking like a LM head above the VM take off that feeds the reflux return back down to the middle of the column? Kinda like a VM with a boka slant plate LM on top and taking the boka take off and reintroducing it back to the column half way down? Would this not mess with the equilibrium introducing a cooled liquid to the middle of the column?

[Manback]

Lol.

Prairiepiss has a good point, hadn't even thought of that.

Some sort of catching condensate-catching device (ie slant-plate or bubble plate) will be required to direct the reflux. If you have that you may as well smash a valve on and have a LM/VM combo. Or at least a plugged take-off so you can add it later!

Prairiepiss theoretically the liquid shouldn't be too cooled. I agree though, I would say either the bottom or the top would be okay but the mddle sounds risque?

Could just build it though.. would be interesting

[LWTCS]

Mister Nixon shows a re-boiler on his diagram. And an external return line that is plumbed to the base of the re-boiler. No reflux at all is returned to the primary boiler.

Similarly, My larger in-line (Humper) thumper does not allow any returning liquid to drain back to the primary (unless it floods of course), thus insuring a relatively high abv vapor composition is feeding the column.

[Prairiepiss]

How is he collecting the reflux to return to the reboiler? Is there somewhere I can look at Nixions diagram?

[LWTCS]

Duh. Here:

http://www.artisan-distiller.net/phpBB3/viewtopic.php?f=3&t=3206

[LWTCS]

IMO, the re-boiler should be sized to hold a predetermined amount of total useable alcohol liberated from the primary boiler charge.

A site glass at the liquid line on the re-boiler would help the operator ensure that no distillate makes it back to the bulk amount of water in the primary prior to collecting.

I also feel that a small, high abv primer charge in the re-boiler will expedite the dynamic cycling process.

[rad14701]

We just had a member who in the last week, at my suggestion, moved his reflux return from mid column to the top on a Nixon Stone offset head valved reflux and gained a lot more control over the still for both temperatures and %ABV of collected spirits... So that makes for conflicting results from what Mike Nixon has discussed... I guess I like seeing the entire packed column equalize from top to bottom rather than from the middle, but that's just me...

[LWTCS]

I here you Rad and certainly can't really qualify any personal opinion about the design as such.

My interest is really the concept of cheating temp gradients.

[Prairiepiss]

Very good read. Thank you LWTS.

[LWTCS]

Also Mr. Nixon seems to use the diagram as a visual reference for discussion more than anything.
Doesn't seem like he is suggesting that the diagram is a working example.

[Prairiepiss]

I can read all day long and still not understand something. But you put a diagram in front of me and the light comes on. That's just how my brain works so I like pics diagrams schematics what ever I can get my hands on.

[LWTCS]

All though I do feel quite confident that my Humper is by far a better choice to use as a re-boiler for an outfit like the one Mr. Nixon has illustrated.
Establishing heat input is dictated by the abv composition and temps of the incoming vapor....and if I said that correctly,,,,that is a fact (proven).


Recon ceiling height would be the only potential down side.....

[olddog]

Recon ceiling height would be the only potential down side.

How about a twin column

OD

[reflux]

Imagine a column with a T in the top
There are two condensers that point downward from the top of the T
One is valved and is the takeoff condenser
The condensate from the other is reintroduced to the column

I'm just trying to keep maximum column height, but it sounds like I might be better off installing a horizontal reflux condenser.
At the moment I just have a tall column but no reflux condenser.

[airhill]

I have a couple of designs (I do them for fun and then think of something else ) I think this is what you are talking about, its untested and I don't think it it will behave as a normal VM at the end of a run ie slow down on tails.
Ok I give up trying to submit images

[rad14701]

reflux, have you researched the forums...??? There are plenty of tested and true designs for your perusal...

What Condenser Do I Need

Some Still Drawings

Diagrams and Plans Thread

Amongst others...

Don't spend too much time trying to reinvent the wheel... While there may be undiscovered designs to come up with they would have to be pretty outside the box to have been overlooked to date... It's not uncommon for newer members to think they have a new idea for a design when, in fact, it has already been conceptualized, discussed, and perhaps even built and tested...

[LWTCS]

How about a twin column

Been thinking all day about a type of concentric twin column design....But it is riddled with question marks.

Still trying to source materials for the new boiler build......feed my apparatus with 87-90

[reflux]

Yeah I've been reading the forums quite a lot.

I've been trying to make the still out of what I have lying around in the shed. I have parts to make another liebig so i thought that if it was OK to put the vapour back in part way down, it would be great.

My column is already up to the ceiling so sticking it on top won't work unless I reduce the height.

Looks like a horizontal shotgun might be the best way to go.

[rad14701]

reflux, have you seen any of the reflux columns with the angled reflux condensers...??? The Scandinavians and Europeans have been using them for years... But before you do a lot of research, what, exactly, do you primarily want to get out of your still...??? Flavored spirits or neutrals...??? Your still might already be taller than it needs to be... We would be better able to help you if we knew exactly what you are working with now... Let the heads of the membership work on this problem with you... Take advantage of the centuries of combined practical experience that is here for the taking...

[whiskymonster]

im the member rad was talking about.

i had the reflux introduced halfway down the column, and was having poroblems in that once i had acheived equilibrium, the temp would change as soon as i started to take off.

i moved it to the top, and the equilibrium actually dropped by 0.7c, and the immediate jumping of the thermometer stopped too.

from what i have read, this is a hell of a lot in regard to final abv for neutral, as much as 5%.

also told me my thermometer was out, but hey ho!

i havent actually measured it, but i actually think i am getting a faster takeoff rate to begin with, and the temperature doesnt fluctuate to begin with either.

it would seem that with the reflux in the middle, half of the column is pretty much wasted.

long and the short, im much happier now.

j

[LWTCS]

Your design is different from what Mr Nixon illustrates. He introduces the ruflux below the liquid line of the reboiler. This insures the equalibrium within the column can self regulate.

[rad14701]

Your design is different from what Mr Nixon illustrates. He introduces the ruflux below the liquid line of the reboiler. This insures the equalibrium within the column can self regulate.

True, but based on the initial question posed by the OP, which reads like a VM column on a standard boiler, the modification whiskymonster made is entirely relevant... I honestly don't know of any member here running anything as elaborate as what Mike Nixon describes in his various papers... Us country bumpkins gotta keep it simple...