double column vm still

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guerrila distilla
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double column vm still

Post by guerrila distilla »

hey guys and gals, just finished reading through the compleat distiller. on the very last page, it says a good method for speeding up your distillation - add another column (it even suggests three columns). i'd like to give this a try as i work in the hotel industry and the hours (and days) are not exactly sociable and i rarely get the 14-16 hours needed to run up a batch on a vm still. this is the idea i came up with :-
double column vm still 2 small.jpg
double column vm still 2 small.jpg (23.26 KiB) Viewed 3122 times
as you can see the 2x, 2" stainless steel columns send the vapour up to a crossroads (still haven't figured out that bit yet) north of the crossroads is the reflux condenser which also acts as a reflux liquid splitter. there is a plate above the vapour inlet to prevent reflux dripping back down the inlet. hopefully if all is cut and drilled accurately an even stream will flow back to each column. i have learn't from one of my posts that two short columns does not equal one long column. the plan is to use two 1.2m columns using 2" T316 stainless steel. i will also use this for both of the condensers as i can get hold of this lovely pre polished tube at trade price (thanks jay :D ). looking at the drawings above it'll look more like a nuclear device than a distillation apparatus lol:shock: .

south of the crossroads is the main vapour condenser. this will be made of the same 2" stainless steel with a copper coil for the vapour to flow through (kind of a reverse leibig condenser). i would like the still to be visually impressive as well as functional. i have used a single condenser with a free flow of vapour/air between the columns to prevent any imbalances caused by using 2 condensers and to keep adjustments simple.

i plan to use a 1500w hotplate to power it. hopefully this will be enough power, otherwise it's time to get the gas bottle out.

in theory, this should half the production time according to the compleat distiller. any suggestions/ideas/improvements guys?
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tracker0945
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Re: double column vm still

Post by tracker0945 »

From my limited knowledge, I would suggest that distilling times would possibly be faster but I doubt that quality would match that. Quality depends on length of column for appropriate reflux numbers to achieve a neutral spirit.
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HookLine
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Re: double column vm still

Post by HookLine »

Just use a single 3" diameter column, which will give you a bit more than twice the output rate of a single 2", and make it tall (at least 40" of packing). Much easier than trying to build and balance two identical 2" columns. Several folk here use a 3" column with great results.
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rad14701
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Re: double column vm still

Post by rad14701 »

Like Hookline stated, a 3 inch column will outperform two 2 inch columns - for several reasons... Distillate vapors will seek the path of least resistance, just like any other gaseous or liquid mixture... That being said, if one column is packed even the least bit looser than the other then it will be doing the majority of the work... There is no effective method of guaranteeing that the flow-rate/back-pressure of multiple columns starts out or remains matched... A possible result of this would be that one column would flood while the other is doing all the work, so you are essentially only running on a single column anyway... Think about it... The only time multiple columns can be effectively used, without these issues, would be if the columns did not contain packing...

Anyone who doesn't believe this theory can prove it to themselves by powering two columns of any type from a single boiler... Two virtually identical Bokakob columns fed by a single boiler will potentially have vastly different output rates due to even minor variations in packing density... Without the packing, for stripping runs, two Bokakob columns would only differ based on minor condenser performance variations...

Go with a single column... It'll save both money and aggravation...
billy_bob_95
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Re: double column vm still

Post by billy_bob_95 »

I'm new to this hobby so this is just a theory I have for running to identical columns on one boil. What if you tried using some type of pressure control valve between the boiler and the columns. Each column would have to have it's own pressure control valve in order for this to work. At the same time I would want a pressure gauge on the boil just to keep an eye on the pressure inside the boiler and a pressure relief device. The pressure control valves would of course have to work in sync. My theory is once the vapor pressure starts to build inside the boiler the pressure control valves would slowly begin to open venting the vapors into the columns equally until the desired preset pressure is reached inside the boiler. Like I said just a theory what do you guys think? The design we use at work with one column is the pressure control valve is on top of the column before the condenser, but with two columns I would think the pressure control valves would have to be before the columns in order for them to recieve equal amounts of vapors.
HookLine
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Re: double column vm still

Post by HookLine »

The problem is not uneven pressure at the base of the column, the columns are already getting equal pressure in the bottom end, because the boiler head space (and hence its pressure) is common to both columns. The problem is getting the packing exactly the same, and the amount of reflux return exactly the same, in each column, which is a lot harder than it might first seem.

It is way easier to just use a bigger diameter single column.

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eternalfrost
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Re: double column vm still

Post by eternalfrost »

id say go for a simple 3" inline slant plate bokakob style. make it into the 4 foot range and you will be pumping out some serious stuff.

i have a 2" X 40" bokakob and it will put out 92% at 1 liter/hour. look around here at the guys with the extra tall 3 inchers and they put out 95+% at twice that speed.

adding to the troubles people have pointed out is just the sheer cost and complexity of what you are proposing. finding and buying all those fittings and clamps etc will be very pricey out of food grade stainless. also messing with drilling out all the holes and connections for all those extra tubes etc. it may seem like alot of cash to go for a long 3" but that will be nearly the only cost.
theholymackerel
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Re: double column vm still

Post by theholymackerel »

Hook is dead-nuts on.

The problem with a multi-column still is that they are not fine-tuneable... you can only make gross adjustments, and the two, or more, columns will always give off different abv percentages.

Take a two column still, remove one column and run it and it'll be instantly more efficient.
manu de hanoi
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Re: double column vm still

Post by manu de hanoi »

why dont you ask directly travis, he posted a 4 column still just a few topics below:

http://homedistiller.org/forum/viewtopi ... =17&t=6922

He might give you valuable feedback.
grizzly1
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Re: double column vm still

Post by grizzly1 »

like my pappy said: "The more parts there are, the greater chance for problems".
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