Vodka - Packed Section or not?

Glenndog · 1 June 2019 08:44PM

After many years of only making rum I am attempting making a vodka from mashed wheat and dextrose which is currently fermenting. My question is I am going to strip but then should I do the spirit run on six plates maybe twice or should I add a 500mm packed section. Any thoughts would be greatly appreciated.

Smaug · 1 June 2019 08:54PM

6 plates is gonna get you good and close ABV wise. But you'll need a bit more scrubbing action if you want to impress your vodka snob friends.

A packed section is a perfect way to keep costs down and knock that last bit of schmutz off of your ethanol molecules.

Mtr_Distiller · 1 June 2019 09:40PM

To a great extent this depends upon column size and design. From MY experience - I started at 6 plates and you cannot maintain 190P @ 60°F with 6 plates. To make clean and nice Vodka, you will need the EQUIVALENT of at least 15 plates. This can be a combination of plates and a packed section. I've tried with less using a number of column variations, both packed and plate combinations, and find 15 to be the magic number.

punkin · 1 June 2019 09:47PM

Could you just run it through 6 plates 3 times with cuts for an equivalent?

Mtr_Distiller · 1 June 2019 10:01PM

I haven't distilled anything more than twice, primarily for efficiency reasons. I normally strip followed by a spirit run. By TTB definition, Vodka is supposed to without character and taste. However, who wants that? Part of the trick with Vodka is to carry through some character from your base ferment to please the palate. I have found the more times you distill, the more you remove any character.

FloridaCracker · 2 June 2019 02:42AM

Agree that there needs to be some character. Just not too much

FC

Smaug · 2 June 2019 08:00PM

It's a weird thing? Kinda like competition BBQ vs BBQ for regular folks eating.

What meets the criteria for medal winning isn't always the fan favorite for drinking.

Glenndog · 3 June 2019 10:46PM

Thanks for the comments. One last question, can the packed section go in the middle of the bubble tees or does it have to go on top.

Smaug · 4 June 2019 03:33PM

You can probably make the apparatus perform in any configuration. But imo you'll get more optimal behavior with the packed section on top. By that I mean that plates (deeper liquid bed) will promote a sturdier temp gradient that will be less affected by what will ultimately become unneeded heat input to the kettle. Or in other words the amount of heat needed in the kettle ultimately becomes un needed heat in an optimally enriched column.

First a preface from the beginning:

See Distillation Temperature and concentration relationship chart / calculator for some background on the relationship of temperatures for liquid alcohol mixture / alcohol vapor temps.
It will require more heat to render alcohol from an 8% kettle charge than from a 15% or 20% charge. Therefore the kettle requires at least twice (notwithstanding heat losses) the heat to render alcohol compared to heat needed at any of the plate levels. But the heat generated at the kettle has to go somewhere? Usually straight up the column to impact the temp gradient.That's point one.
Actual plates generally have a more abundant accumulation of liquid in a more confined place. So one would say that plates maintain a liquid bed. The liquid that accumulates in packing (random or structured) is more or less in the form of accumulated droplets. So the plates have a more dense accumulation of liquid in a smaller amount of area.
The very first job or task of the liquid bed is to condense incoming vapor. And the deeper the liquid bed, the more capacity it has to absorb heat. So this liquid on the plate is a cooling medium. And since this cooling medium is made up of a mixture of alcohol and water, it will be the percentage of alcohol on the plate that determines at what temperature vapor will flash and how much heat at that point is permitted to rise up to the next plate level. So the % of alcohol on the plate determines (self regulates) the temp needed to allow further vaporization. To summarize, deeper liquid bed absorbs heat better, while the abv on the plate determines the forthcoming flash point. Liquid droplets in packing have less ability to absorb what will become unneeded heat. Unneeded heat allowed to migrate up the column shrinks the gradient,and permits more water infiltration further up the column. That makes for lower abv.
The deeper liquid bed helps create a sturdier temp gradient and relieve the burden off of the packing to manage unneeded heat. This will allow cooler temperatures (higher abv) to migrate farther down the column. This behavior acts to more completely enrich the packed column and allow it to otherwise run faster without compromising the abv.

I hope I put that together with some measure of clarity?

grim · 4 June 2019 06:13PM

That's the best explanation of it I've ever read.

Smaug · 4 June 2019 06:35PM

Thanks @grim

3 summary points really.

Shifting as much alcohol as possible from the kettle into the column will promote a more optimal temp gradient. Fixed (bubble cap) plates will literally hold up liquid with out regard to pressure. Packing must rely on pressure for liquid hold up. So even though packing facilitates more potential distillation cycles (good behavior), the lack of liquid mass allows for more heat intrusion closer to the top of the apparatus (bad behavior).
Minimize previously distilled alcohol from returning to the boiler too quickly.
Utilize the larger liquid bed as a heat exchanger / buffer zone to minimize heat intrusion into the top of the apparatus.

Glenndog · 4 June 2019 09:43PM

Thanks @Smaug, great explanation and great information. Makes not only my question but lots of other things I've wondered about so much clearer.

crozdog · 5 June 2019 02:41AM

Well put @Smaug

Welcome!

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Vodka - Packed Section or not?

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