Vacuum still

[pothead]

A buddy and I are considering one....we know the downfalls and saftey issues, but what would the upsides be?

ANyone have opinions on pros and cons?

[pothead]

40 views, and no responses yet?
ANyone here know anything about vacuum?

[Husker]

Probably beyond the skill set of most hobby home distillers here (with a couple notable exceptions).

H.

[pothead]

I was hoping those notable exceptions would chime in.
It's been a while since I've been here, and I miss all the info.

I see the site has made a few changes...looks good.

[stoker]

I don't know more then there's written on the wiki page
http://en.wikipedia.org/wiki/Vacuum_distillation" onclick="window.open(this.href);return false;" rel="nofollow

the main thing is you lower your boilingpoint by lowering the pressure and so have to add less (no) energy to let the compounds boil.

I can imagine your distillate will be different from the traditional. The heat of distillation lets some molecules react with each other (ex: esthers) and that's something you won't have with vacuum. If this is good or bad is up to you.

I've never worked with one. and never heard of one used for spirits

good luck, and lots of fun, keep us informed.

[pothead]

It is a shame there is such limited information on the subject.

Essentially, vacuum distillation should make just as pure spirits as a valved reflux, with less heat, and in much shorter run-times.

I would never recommend it to newbies because it can be potentially dangerous if extreme care isn't taken.

But the questions I have are if the unit is under vacuum pressure, how would the liquid be released? If you have to relieve the pressure to take off all the foreshots and heads, would you have to let it equilibrate again before taking off the hearts?

Has ANYONE seen any kind of vacuum still used for alcohol?
even in a large-scale ethanol fuel plant?

[pothead]

I did find a few links, and If a mod ok's it I will gladly post them.

[Rocketman]

I'm the new boy on the block and here is my 2 cents worth. Vacuum distillation is used by many laboratories every day all around the world to protect the integrity of the material that the distillate is being removed from,EG chlorophylls going from green to brown and changes in color due to high temperature. At the bottom end of the scale freeze drying is used to preserve live vaccines. Pharmaceutical freeze driers run at vacuums around 0.3 Mbar (1/3000 of an atmosphere) and water boils at -45 C.
From what I have read on the forum the main concern is conserving energy (low temperature evaporation).
OK , So assume we reduce the atmospheric pressure in the still so ethyl alcohol boils off at 40 C, the condensing temperature will be reduced proportionately to say 15 C to 20 C. Now if you take into account the thermal efficiency ( or inefficiency) of your condenser , tap water is not cold enough to condense the distillate , refrigeration will be required. Once refrigeration is used every Kw of heat used to evaporate must be removed by refrigeration to condense the distillate (expensive set up and running costs). There is also a considerable cost associated with a suitable vacuum pump and associated control equipment.
NOW think about this, The heat required to raise your boiler from say 15 C to 80 C (sensible heat) is small compared to the amount of energy required to evaporate your distillate (latent heat of evaporation).
I have never attempted vacuum distillation of ethanol, but i have been closely involved with Vacuum dried and freeze dried fruits / vegetables for a number of years. It would appear to me that vacuum stilling ethanol would introduce a lot of extra cost with little or no benefit , IE 1. Separation of volatiles (head) 2. Water vapor flashing off lower than water boiling point 3. Separation of higher alcohols (tails).
ON THE POSITIVE SIDE - At the end of you vacuum distillation process you would end up with a great looking left over wash.

[Pikluk]

Essentially, vacuum distillation should make just as pure spirits as a valved reflux, with less heat, and in much shorter run-times.

just as pure yes
less heat yes but it been pointed out gonna need more cooling
faster i dont think so, the speed is in direct relation with the size of the still

to make the cuts you either shut it off and change the collection vessel or have some valve and multiple collection vessel.theres also other means like a "cow" that use gravity instead of valves.

I can imagine your distillate will be different from the traditional. The heat of distillation lets some molecules react with each other (ex: esthers) and that's something you won't have with vacuum. If this is good or bad is up to you.

im very curious to see if its a good thing or not.

in a lab they use vacuum distillation not to save energy but to protect what they are distilling either from the heat it would normally take to evaporate or if the product cant be in contact with air, etc...

as for refrigeration equipment needed id say that you dont need to go that low of a vacuum to make a difference.

[manu de hanoi]

A buddy and I are considering one....we know the downfalls and saftey issues, but what would the upsides be?

ANyone have opinions on pros and cons?

do u have a link to the seller of vacuum stills ?

[Rocketman]

These guys spent a lot of time and money developing a vacuum still. They never made a still for sale. Check them out, they will have a lot of info on the pros and cons. http://www.cuddon.co.nz/projects.html" onclick="window.open(this.href);return false;" rel="nofollow

[snuffy]

There's a brief article in American Distiller a while ago about some guys in Oregon who've been fooling around with a vacuum still. They got theirs from Japan where they are used to make some sort of booze from rice. They reported almost no tails.

It doesn't take much of a pump to pull down to the vapor pressure of boiling alcohol. I've built and used water jet vacuum pumps (aka aspirator) to degass epoxy to pot electronic gear for deep underwater use. They can pull pretty hard and move a respectable amount of volume. Properly made, they will pull down to the vapor pressure of water.

You can boost their pull considerably by putting the outlet under water (liquid trap), but when the water pressure drops, all the water in the trap shoots back into your vessel. The first time I tried it, I was so pleased at the increased pressure drop. Then when I turned off the water -- oops. Ruined that batch of potted circuits. Taught me to drain the trap before turning off the water.

If the tube going down to the trap was more than 32 feet tall, the weight of the water would hold the vacuum.

Another time, I had to clean out a plugged fuel oil line buried under ground. I fixed a 55 gal drum as a vacuum receiver, built a water jet pump (all it takes is a tee and some hose fittings), hooked 'er up and let 'er rip. The line stayed plugged, but the drum imploded. No harm done, but it was unexpectedly exciting. The drum ended up pretty small - like 15 gallons.

Steam ejectors are used in commercial distilleries to lower the pressure in coffey stills.

http://en.wikipedia.org/wiki/Aspirator" onclick="window.open(this.href);return false;" rel="nofollow

[decoy]

another future experiment i intend to do.. one day...
i have already performed limited test and feel this is achivable on stills curently used by most memebrs.
i have made a number of difrent heat pipes, these operate on similar principle but return alcohol back to resivoir to maintain cycle.

i think it wouldnt be to hard to do a vacume still.
pre requisits are
the still should be able to withstand the vacume it is going to be subjected to..
the still must be air tight.
0 atm is not requierd.

vacume still.jpg (14.83 KiB) Viewed 8443 times

any level of presure below you current suronding presure will resul in a lower boiling point.
lower boiling point = less Energy req.
if the still is air tight, once desired vacume is achived, the still should maintain that vacume it self.
adequate cooling must be sustained
once the still under the desired vacume any vapour present in the system will look for lower presure areas in the system to travel to.
the condenser will create these low presure areas directly infront of its internal surfaces by condensing vapor it comes in contact with.
as the vapour condenses it will form a low presure sucking in more vapor again condensing it.
the liquid then trickles into the colection jar.
if vapor travels past the condensor, eg. into the jar it will ither condense or it will be drawn back to the cooler condenser surface.
this operation is very similar to the heat pipe except the liquid dose not return to the heated boiler.
the regulator wil prevent the still from imploading if there is a suden large cold surface or other reasons for sudden drop in air pressure.
the presure switch is there to turn of vacume pump once desired vacume is achived.

one day i will test it but if anyone else would like to try.. go for it...
be aware as snuffy posted with the 44 gal drum, if your still cant handle it it will suck it self int to a matchbox...

want to try and see what happens,
get a 5lt tin can with screw lid
take the lid of and put 500ml of water in it.
have a jug of cold water handy.
place it over a gas burner or on the stove and boil the water.
when you see the steam coming out vigourously take it of the fire and quickly screw the lid on.
put it in the sink or what ever and pour the cold water over it.
watch it suck it self into a flat tin can.

cheers

[manu de hanoi]

I could give it a try someday if before the following questions are answered:
- All of the following questions require to setup a value for the pressure inside the still, what would it be ?
- What should be the max temp of cooling water ?
- Are we sure that in the low pressure conditions the distillate wont re evaporate and be pumped out by the vacuum pump ?
- In an open system it's the boiler that drives the speed of distillation, here there is a bit of "pulling" the vapors by the condenser. The faster you condensate the more vapor you can pull. How does it affect distill speed ?
- If the water jet pump could handle it as Snuffy sugested that would be nice, if cooling water could be used for this purpose that would even be nicer. But what is the relation between water pressure/speed needed and the void to pull ?
- Could flour paste sealant handle much pressure ?

[decoy]

ok the way i work it out is if you create a vacume before you fire up the still, you should be able to maintain that vacume.
i would start with .5 atmosphears, it is extreamly imposible to get 0atm
when i use the word vacume i mean the safe operating pressure sustained by your still, any presure below 1atm is workable, 1atm being sea level.

once the vacume is established and you start the boiler, the air presure will increase, as teh vapor hits the condensor or other cold surfaces past the condensor it will condense maintaining vacume.

as it requiers a lower temp to evaporate the alcohol in the boiler you need less water flow in the condensor.
i belive water temp below 30c will be sufficient, but you may need colder water as alcohol should vapourise at about 50c, im sure there was a table on the parent site.

the idea behind the negative presure regulator is to protect your still from implosion, you would lower pressure as you feel your equipment will handle it.

as your condensor condenses the vapour it will create a negative presure untill the boiler can generate enough vapor to fill it again, so the boiler is still governing the speed of the distilation.
the vacume just affects at what temerature it occures.

again the moment you go below your ambiant air pressure you will create a vacume and it will pull any vapor present in the boiler.

cheers.

[Dnderhead]

I seen a interesting one on the net, it was a pot in a pot, inside pot held what they were distilling and was heated,the out side pot was closed and used as a condenser the hole thing was put under vacuum. not to good for our use as no way to take off foreshots/heads. but mite be for some one.

[eater]

There's a brief article in American Distiller a while ago about some guys in Oregon who've been fooling around with a vacuum still. They got theirs from Japan where they are used to make some sort of booze from rice.

Does anyone have a link or copy of this, or info about the guys? I'm very curious, and http://www.distilling.com/backissues.html" onclick="window.open(this.href);return false;" rel="nofollow seems to be broken.

Thanks!

[rhumbum]

I have been considering this idea for building a large stripping still. I have used vacuum pressing before in my work as a cabinet maker/finish carpenter, and I am currently building myself a vacuum press for my workshop, so I have most of the equipment for it. Maybe I can adapt my press for working with a still also. I may need a different vaccum switch as the one I have for the press works at around 18-25 inHg which is too much vacuum for stilling.

The idea I have been considering is to build a 60 litre stripping still that can operate under vacuum. I already have a 18 litre pot still, so rather than doing 3-4 stripping runs and then a spirit run all using the little still, I could put all the wash in the 60L still and strip it all in one go using the same propane burner I use for the little still because the vacuum will mean I don't need a huge burner and loads of propane to boil it in reasonable time. I would aim to boil the striping still at say 40-45 deg C instead of 80-90.

I don't think a vacuum still is a good idea for a spirit still because even if you have some sort of device to make cuts such as a valve that diverts flow into different collection vessels, you cannot smell or taste what is coming off so how would you know when to make cuts? I don't think going by temp alone is good enough, at least not on a pot still. It might work OK for a reflux still.