Construction of a etho still under vacuum

Ok here we go
I am working on a semi medium sized
Ethanol still
I want to make this still to work under vacuum so that i am able to boil of the ethanol at a max temp of 30C
The boiling “flask” and receiving "flask "
Are used stainless steel warm water boiler
Cilinders(damit can t find the right word)
They each have an internal stainless steel coil Wich i plan to use
In the boiling flask for warm water to get the cold boil at 30C
In the receiving flask to cool the ethanol to prevent evaporation deu to room temps being close to 30C
The head diameter pipe If used the hole that already exists is 42mm (1.65 inch)
Quiestion is this sufisiant for evaporation of the etho
The “flasks” have difrent diameters
The evaporation surface one one is 124 square inch
On the other is 194 square inche
Wich should be the boiling “flask”
With a head pipe diameter given
Ok then what is the avarage temperature of the condenser for this i have chillers in Many temparuture ranges but for the main condensor ?
I plan of putting a glass frederich condensor on the vacuum inlet port Wich is set at -40 C is that enough to protect the vacuum pump ?
A cage


A cage Will be weld around the flasks to make sure the don’t implode under vacuum
all input and advise is welcome


Each of the tanks has a volume of 80 liters about 21 us gallon
So hope to fill them with 15 gallons per run of etho /oil

seems like a solid plan to me. I wouldn’t worry about imploding either of those containers. pretty sure you could pull them down to 1micron without an issue.

understand that I’m a biologist, not an engineer, so I tend to guess & iterate rather than math when building prototypes (arguably the same strategy that gave us life as we know it :wink: ).

the appropriate math is lying around here somewhere, and it probably wouldn’t hurt to locate it and run through the numbers.

-40 might be enough to protect your pump. using a diaphragm pump that can handle ingestion of ethanol might make some sense. you can always dial the vac level or heat input down to where it does protect your pump.


Knew i Could count on your input :grin:
In My opinion head hight should not matter to much since material being used is at 3% moisture (i dry out)
And reproofing is probably done by molecular sieves
But i Will do the math anyway
What temp is your rotovap condenser set at When doing a cold boiloff of etho ?
I start to wonder If this method of evaporating etho of is not perfect for 3 world , parts impossible area s
I think iT is more time consuming and You Will Need a larger stock of etho to keep the weels turning if not misstaken very energie efficiënt very littel moving parts
Thx again :+1:

1 Like

when boiling off solvent for etoh shatters, I run my rotovap at 25-30C with the condenser set around -5C. I’ve got a -70C cold trap before my pump.

if going for a decarbed product, I’ve found using a still then finishing in a rotovap works well, but the ethanol recovered in the rotovap needs reproofing (while the bulk pulled off in the still does not). I’m using a very basic alembic style head & an air cooled stainless coil as a condenser. so I don’t have to throw water on the ground.


God damn. Love the ingenuity. I’m excited to see updates on this project. @cyclopath I saw your post about using a conical fermentation vessel as a boiler for a still rather than an expensive jacketed reactor. Was there any worry about implosion under vacuum with that setup?

I’m in the process of making a similar one of these for usage in our facility. Mostly for recovering waste solvent for re-use and for recovering ethanol from dewaxed solutions.

We were going to do a simple 12" diameter jacketed collection vessel, with a wide 12" lid so it’s easy to access the evaporation chamber and scape out residue when finished. We will have a continuous liquid feed fashioned out of a hose with a 14" dip tube on the end, which can be dunked into a container of solution.

It will recover into a standard (non-asme certified) extractor recovery tank, with a tube and shell heat exchanger to aid solvent condensation.

Pump will be a master vapor pump with PTFE diaphragms.

If it works right, the force of suction from the master vapor should easily suck liquid up through the straw into the evaporator, then recover the solvent straight into the tank. When completed, we can open up that 12" vessel and easily scrape it.

Solvent can be collected from the recovery tank easily, as it will have a liquid-out drain at the bottom which can be fashioned into a downspout / spigot / faucet for easy collection into a jug.


No, because I never pulled more than 10” Hg on that still.

They’re cheap enough that a little distructive testing won’t set you back much if you wanted a handful and wanted to suck as hard as you could on them.

Vac failure is way less scary with stainless than glass :nerd_face:


Well i got a little further and Yes
I am aware of copper :frowning_with_open_mouth:
But tri clamp is hard to find in europe so
I made this out of copper tubes
Reason beeing i don t think the head needs to be this high
So once opperarional i Will lower the head hight and see what that does to
The quality of etho
Second reason beeing that the tanks already had ttreaded holes for the head pipe in this diameter so lazy as i am i want to see If iT is large enough for the still
Once all is at Desierd size i Will change to triclamp
They are off to the welding shop for a extra bottom drain and a extra vacuum suction Port in Wich i Will gleu a glass frederich Condenser
Any how just a update :stuck_out_tongue_winking_eye:


sounds legit!

are you going to run the vapor through your pump or to your pump?

I tried “through” with a TR21, and wasn’t impressed with the recovered solvent. Towards rather than through seems like a better setup.

haven’t seen the master vapor in action, but I image it will work.

you might have bumping issues if you don’t add agitation or stirring of some sort.

Through the pump. May have fewer issues with the MVP than the TR21, as it has PTFE diaphragms and no grease wetted parts, so contamination risk is greatly lowered.

I’ll play around with some ideas as to how I can get some better stirring capabilities inside the vessel itself, but the MVP ripping on it with a well-heated jacket is going to work wonders on its own.

There are liquid pumps available I can use to convert it into a falling film evaporator if I really want to… But we’ll see how it works on its own first.

1 Like

I have now most of the hardwear
For the 2 tank distillation unit
A haake v15 chiller to keep the receiving tank and " liebig " cooler at -5C
A julabo sw23 To keep the boiling tank at 30 C
A Diafragm vacuumpump for vacuum
I yust still need to work on the coldtrap section
And the magnet mixer
Quistion how important is iT in this type of still to have Some sort of mixing gooing on in the boiling tank?
Bumps can bearly be a problem to get past the head since i wasn t planning on filling her up more than 2/3
Does mixing speed up things ?
Or make a more even evaporation traject ?
So in short is iT worth the effort to build
Since i would have to build iT around the bottom drain valve outlet ?
Thx for Any advise given

1 Like

I’ve had ethanol bump pretty fiercely in a flask that was less than half full because my stir bar wasn’t spinning fast enough (also was probably running the flask too hot for the level of vacuum in the system). I have no idea whether agitation will increase evaporation significantly, but I think adding a bump trap would probably be a good idea. Especially if you go with zero agitation. I can ask around in an ethanol distilling forum that I frequent as well to see if anyone has any ideas.

1 Like

this is pretty much what my still builder recommended for the 100gal vac still…although he spec’d 4HP, which imo only makes sense if you’ve got a thick mash in there. I rolled with it, because at the time there was no CUP in the plan, so I figured I would have a thick slurry that needed stirring (and figured I’d pick up something smaller for the still).


BUsy Busy so havent done much work one the still
Made a pretty detail today though
Gleu ed in with epoxy a lab glass piece Wich i was able to cut with a ss steel cutting Blade i now have a visual of My head in the still Wich was one of My concerns ( hate not beeing able to see what s happening )


Made the insulation sleave today the geurilla. Way but iT works so
Some carton used by painters and plaster men
Some good old duck tape
WD 40 and construction foam


I can’t wait to see this. I love seeing shit of this magnitude

I wonder if a sight glass would be good to have in the boiler head to make sure your distillate isn’t puking (bumping)? Or is that what the lab glass piece is for?

What is a bump?