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Dephlegmators

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I've been investigating commercial stills, and many incorporate dephlegmators. I understand they add extra rectification, but that's their advantage compared to just adding extra plates?

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I'm certainly no expert, but what I've been told when I asked a simlar question of someone a few years ago (I think it was Kris Berglund, but I honestly don't remember for sure), is that a dephlegmator (aka a tube-type reflux condensor) ads another level of rectification after the colomn, while the steam is cooling down and heading towards the condensor. It's vertical tubes allow charged steam to contact and strip alcohol molocules from the liquid on the side of the tubes while the steam is cooling, condensing water and other higher-boiling point stuff and returning it to the still prior to the steam getting to the final condensor. That is if I remember the converstion correctly.

I found a definition that seems to support that too ...

Dephlegmator - a device surmounting the rectifying column of a still whose function is to condense portions of the vapours rich in high boiling point constituents and return the condensate to the column as reflux.

I've also seen older stills with virticle tubes either in/on or attached to the still head that are structured like a tube-dephlegmator, but that fill the function of a colomn (I guess they would technically be a colomn ...).

I hope that helps.

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One more thought that I should have added above is that (I think) a significant difference between a rectification column and a dephlegmator is that the steam passing through a column is coming out of the distillation chamber (kettle) and is high in heat-energy making it rise, the steam passing through the dephegmator has far less heat energy as it is already starting to condense and is falling ...

Notice I said "I think" ... anyone with more knowledge want to comment?

S.

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You use a dephlegmator to control the reflux ratio. You could simply have an empty section of column up on top (I suppose it would be a helmet of sorts) that would provide some air/wall-driven reflux to fill your top plate. But then you have to take what you get - a certain amount of vapor falls into the lyne arm and a certain amount refluxes back. And that ratio would change over the course of the run as the composition of the liquid boiling in the top plate changed.

With an actively cooled internal condenser, you can vary the amount of condensation sent back down over the run so it's always the same fraction. Or near it.

The end effect is that the proof vs time curve is flatter - you get more out at higher proof. With no dephlegmator, the proof changes continuously during a run. It's a pretty linear decline.

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The proof coming off of your still with a dephlegmator is easily tuned because you can decrease the flow of distillate while only bringing over the highest alcohol possible. It is all about reflux ratio. The Compleat Distiller is a great reference on the subject.

I've built a 'helmet' with a double coil inside to control my reflux ratio.

Cheers,

Brad

Spirit of Texas

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hello all,

the dephlegmator is also a great tool for making clean cuts from heads to hearts. it helps to send them through in a surge. so I'm told anyhow..

Jester

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The end effect is that the proof vs time curve is flatter - you get more out at higher proof. With no dephlegmator, the proof changes continuously during a run. It's a pretty linear decline.

Thanks, that helps clear it up a bit. I'm a visual thinker. Anyone out there actually have such a graph? I'd also be curious to see how the two systems compare in energy consumption.

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Hello Max Action,

If you are really interested in moving forward I recommend, repeatedly,and if you have the time and money, to go and attend one of the workshops put on by any of the several still manufacturers. Rather than hunt and peck for bits of info you get a wealth of knowledge from the sections offered. A lot of handout material also such as the graph you requested.

Cheers, Bob

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A dephlegmator is basically like the second column of a Coffey Still. See Diagram. A Coffey still is continuous, but for our use we can put a boiler on the bottom of the first column. The coolant on the Coffey still is the beer getting preheated before entering the first column. For our purposes we will use water as coolant which will just be poured down the drain.

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The answer has been made previously that the dephlegmator helps to determine the rate of reflux and therefore the purity of the spirit. This concentrates the heads cut (low volume high concentration) and gives you great control over the amount of congeners in the hearts cut. You never really get full use out of your plates if you are not force filling them with controlled reflux from the dephlegmator. Think of each plate as another pot with liquid that is being vaporized by the vapor heat beneath it. It is difficult to keep liquid on the plates with only air cooling of the helmet/column from the outside, and you have no real control this way.

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