THE EVAPANATOR

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Graywolf

Graywolf

THE EVAPANATOR
Rotary Thin Film Evaporator

What deep dark alchemist lair is complete without a rotary evaporator, but how many of us'n poor brothers or sisters can afford one?

How nice a Rotovape looks, but hard to clean, besides expensive. Hee, hee, hee, let's see what we can do better, cheaper?

Behold the Evapanator rotary thin film evaporator, in next years prototype build schedule.

The Mk I Vapenator uses twin drums constructed from 6" X 6" stainless steel sanitary couplings from Glacier Tank, with modified lids that include a hollow shaft, which turns the couplings into sealed drums and to be rotated on their sides in a hot water or oil bath, while a vacuum is being pulled on them, through a rotary vacuum union.

The hot water bath can handily be provided by a 1200W Wyott W-3Vi 12" X 20" counter top food warmer, and Deublin Co can provide a suitable 17-051-045 rotary vacuum union.

The shafts through the lids rest in a vee between two 1 1/2" roller bearings and a 2" X 15 tooth #35 sprocket rests on a moving roller chain, powered by a 2 rpm gear motor.

Still checking specs and prices for the gear motor and trying to decide on the incremental utility of a variable speed gear motor, vis a vis fixed ~2 rpm unit, giving the drum about 1.6 sq/ft of thin film evaporative surface per minute under vacuum, per drum.

The coolest thang, is that you just disconnect the vacuum hose, and the whole drum assemblies just lift out, and both ends of the drum come off via 6" Tri-clamps, which gives full access to the inside of the stainless drum, to clean out the viscous resins.

Here is my conceptual of the purdy thang! For those of ya'll who understand it at a glance and are off to do it one better, ah hope you will share. For those with patience enough to wait for it's schedule in the queue, watch this space for detailed drawings and our own prototype shake down.

The Evapanator Rotary Evaporator-1-1.jpg
 
pork

pork

that's sick....been using the food warmer over here and it's an epic hot water bath..sure beats kettles...i can already see it in action....the goal is to decrease purging time, yes?
 
Ohiofarmer

Ohiofarmer

haha dammmm GW you just hadda go and dun do it now! show some pics when your done fiddlin with it. :D .......You got too much time on your hands haha take it easy man, cool build
 
Graywolf

Graywolf

That is an impressive plan you have in the making Graywolf. Have you started building it yet?
Just collecting parts so far but it is giving me a wet leg thinking about it.

Alas, I have a full plate completing my project list for the remainder of this year, as well as funding constraints, especially with it also being the season to be jolly and spend loads of cash on wifemate, kids, grandkids, and great grandkids out of personal mad money allowance.

I also have a partially completed Enabler compound fractionating still to finish, as well as a Mk IV Terpenator in progress, which are all part of a family of enterchangeable components, so far comprising the Lil Terp passive extractor, Mk IIIA & IV extractors, Enabler fractionating still, and Vapenator rotary evaporator.
 
entropy99

entropy99

Just collecting parts so far but it is giving me a wet leg thinking about it.

Alas, I have a full plate completing my project list for the remainder of this year, as well as funding constraints, especially with it also being the season to be jolly and spend loads of cash on wifemate, kids, grandkids, and great grandkids out of personal mad money allowance.

I also have a partially completed Enabler compound fractionating still to finish, as well as a Mk IV Terpenator in progress, which are all part of a family of enterchangeable components, so far comprising the Lil Terp passive extractor, Mk IIIA & IV extractors, Enabler fractionating still, and Vapenator rotary evaporator.
Keep feeding that mad scientist within! :D
 
squiggly

squiggly

Where can I order one?

I'm being so fucking serious right now. Please let me know if you want to bounce any ideas off of me--I'm game to do some lit research over the holidays if it will help.

Where is your condenser? I'm assuming you don't want to pull solvent off through your pump.

Condenser design for this thing is going to be very important dude--you need a very very high capacity condenser for the job. It would be nice to have something that can accommodate dry ice as well. Just throwing some stuff out there u might want to think about before breaking ground.

I'm also really worried about bumping with this design--there is a
reason all of these things are angled just so.

Is there no way to commission a piece of lab glass for the chamber and design around that? I would really recommend it from an efficiency standpoint--as someone who sits in front of a rotovap a lot, it its helpful to be able to see the stuff. Also what does the conductance of heat look like for your design vs. heavy-walled lab glass? The more the better for this application. It really matters how fast heat can travel through the medium--as you'll be aware, when we start scaling things down to gain an efficiency benefit (such as getting a very thin film to remove the thermodynamic barrier to evaporation of solvent) the small details become quite important.

You're going to want fine control of the rotary motor speed as well for some applications. You get a "feel" for how fast you want to rotate it, and how long of a vaccum it needs, what temperature adjustments to make--how much material you should put in (so as to not shit up your lines).

Without these abilities (most of which require vision on the sample) I would venture a guess to say I'd never get a clean sample for the NMR (that is to say there would certainly be residual solvent).
 
Graywolf

Graywolf

Thanks for the good thoughts and input brother Squiggly!



You're right about condenser capacity, and I have yet to pull it off with vacuum distillation, using all three of our lab condensers and double cold traps in series, with cooling from pumped ice water.



I collect about 20% more solvent with my simple pot still, so it looks like I will have to build an adequate condenser. Any design thoughts that you have on that, would be appreciated. My current thoughts are an upper horizontal header, with "N" down tubes between it and a lower horizontal header.



I envision it sitting in a barrel of brine, with a single tube passing through the bottom of the barrel via a bulkhead fitting, and bleeding into a catch container, kept under vacuum.



How would you design your condenser, from a clean sheet of paper?



As for bumping, how much bumping are you seeing with a thin film under vacuum? I see it in our simple pot stills, without boiling chips, but haven't noticed it doing thin film vacuum purging in a Petri dish.



If it is an issue, a labyrinth intake inside the drum, should keep bursting bubbles out of the intake stream.



Good idea on the custom glass drum. I will check with our scientific glass shop for a price!



Borosilicate is a better conductor than 304 stainless, but it is a linear formula and we can always increase the delta T to get the same rates of heat transfer.



I suspected as much with motor speed, and the incremental cost for a variable speed motor isn't that much, so I probably ought to bite the bullet. It would certainly make process development and refinement easier. As noted, the test sled most certainly will have one.
 
squiggly

squiggly

Thanks for the good thoughts and input brother Squiggly!



You're right about condenser capacity, and I have yet to pull it off with vacuum distillation, using all three of our lab condensers and double cold traps in series, with cooling from pumped ice water.



I collect about 20% more solvent with my simple pot still, so it looks like I will have to build an adequate condenser. Any design thoughts that you have on that, would be appreciated. My current thoughts are an upper horizontal header, with "N" down tubes between it and a lower horizontal header.



I envision it sitting in a barrel of brine, with a single tube passing through the bottom of the barrel via a bulkhead fitting, and bleeding into a catch container, kept under vacuum.



How would you design your condenser, from a clean sheet of paper?
If I had the means--I'd design it as a coiled coil (tiny coil wrapped into a big coil) its ALLLL about surface area in terms of design shape. You can also pump through colder coolant as a way to increase capacity (much in the same way you can increase your heat conductance to hit the enthalpy of vaporization you're looking for--you can decrease the temp to hit it from the other direction). Sometimes it's as easy as using a salt/ice/water slurry to get the job done.

Alternatively I'd do some kind of a hybrid between an alihn and graham coil.

Generally a coil is going to be your best bet to increase capacity, just think surface area and your ingenuity will come up with something. Remember that equilibrium plays a large role here--two very important notes on that:

1. Condensation creates heat--so your thermal conductance is highly important. As each unit of heat is gained, the next molecule is that much less likely to condense--the faster we remove the heat, the higher the capacity will be. Keep in mind that molecules work at incredibly high speeds so every little increase in efficiency counts for SO MUCH in this respect.

2. As a result of 1 it becomes a concern how fast solvent drips from your condenser--you don't want it to have anywhere the liquid can settle (another reason a coil works very well).

As for bumping, how much bumping are you seeing with a thin film under vacuum? I see it in our simple pot stills, without boiling chips, but haven't noticed it doing thin film vacuum purging in a Petri dish.
Beware, bumping is an all too common occurrence in thin film evaporation. A good rule of thumb is to never fill the vessel more than half way--but it will all depend on the angle of inclination of the neck as I'm sure you might imagine, because in the end bumping is a liquid transfer that results from this sort of snowball effect.

Usually we think of it as superheating and lack of nucleation causing a boil over when nucleation begins and a chain reaction of nucleation results--boiling chips are thus the answer in stills (as they provide nucleation sites to prevent this).

When you're actually reducing the pressure (you're not talking about a vacuum still are you?)--boiling chips won't get you too far. In the case of boiling under atmospheric pressure you're spending essentially the entire heat up time trying to overcome 1atm of pressure.

With this process you are removing that impedance to boiling in a matter of seconds rather than minutes. Not only should you expect vigorous boiling--but it'd be weird if you didn't get any. Instead of seeking to control nucleation (because often rotovaps are meant to retrieve a pristine sample--unadulterated by anything else, including boil ezers) we just make sure the vessel is big enough to handle the size of bubbles we're going to make (BIG), and also to not overfill the vessel.

A final safety feature is the bump trap, and I highly recommend you install one. If you custom source a glass vessel--it should be no problem to simply purchase a bump trap (or have on custom made). The last thing you want to do is have a high surface area condenser shitted up with oil.

If it is an issue, a labyrinth intake inside the drum, should keep bursting bubbles out of the intake stream.
you'd know better than I on this one--but be aware that the shit is going to bubble--and if you don't plan accordingly you're going to have thin film on every inch of the vessel, rather than in the bottom quarter where you want it.

Good idea on the custom glass drum. I will check with our scientific glass shop for a price!



Borosilicate is a better conductor than 304 stainless, but it is a linear formula and we can always increase the delta T to get the same rates of heat transfer.



I suspected as much with motor speed, and the incremental cost for a variable speed motor isn't that much, so I probably ought to bite the bullet. It would certainly make process development and refinement easier. As noted, the test sled most certainly will have one.

Few final notes:

I'd really recommend making the vessel RBF shaped--this aids in the dispersion of the sample into a thin film. You will end up trapping solvent near the edge of your drum. The idea is for the film to be uniform--which pretty much means a round vessel. (Angle of inclination also plays a role--and this is why the more expensive models allow you to adjust this).

If you're able to source LN2 (I don't know how much it costs)--a cold trap might work, but you must be very careful as there is a chance for an explosion if you pass too much air too quickly over the cold trap when bleeding your manifold.

You might also try a cold finger condenser. As I said earlier you can greatly increase capacity by bringing temps way down. If you construct a cold finger apparatus that will accept a dry ice bath (ethanol -72C, acetone -78C, or LN2 baths can take you all the way to -192) it should be able to overcome whatever you throw at it (with a reasonable size, of course).
 
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