Ethanol recovery using Graham condenser under vacuum @ 40C

Hello,

Since I don’t have a Rotovap I’m wondering if using a Graham condenser under vacuum @ 40C will be harmless for the crude. The boiling flask is in a heating mantle with temp probe and magnetic stirring (the one from the SPD kit) . I also have a head with thermometer on the flask, then a 400mm Graham condenser.

What bad things do you see that could happen using this method?

Thanks!

It’ll be painfully slow but will work fine. I’ve done it before cobbling together my first eBay special buchi roto. I even had mine setup to preheat the feedstock and continuous feed the boiling flask drawing from a large 10L carboy. I used a simple bent elbow but you could use a 75 degree adapter as well. It would be faster than using an SPD head

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Thanks for your answer!
Actually I already built the system with a long (400mm) Graham condenser for a higher rate of condensation and it is working pretty good and fast in regard to ethanol recovery!
My question is if it’s safe for the crude…so the final result will be as good as the one resulted using a rotovap. In my opinion, since I’m using a low temp (max 40C under vacuum) it shouldn’t affect the quality of the final result. But since I’m no expert, I might not considered other factors that might alter the good stuff in the crude…

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No problem for your crude
At 40C
Any temp above 80C and time will have effects

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Ya 40c is fine

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Thanks for your answer!
There is one thing that I can’t explain…so, I’m distilling to recover the ethanol with the above system…I have like 4 liters of tincture and everything works fine @ 40C (40C mantle probe and 40C head temp). All good so far…
But as I come to less solvent in the flask the probe temp is still 40C but the head temp jumps to 75C!!! I can keep my hand on the mantle but the top of the flask is pretty hot!! Also some fine brown colored layer starts build on the head glass…
What could be the explanation of this?! How could the vapors of a 40C solution get to 75C?

Malfunction of the flask probe most likely

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Nope. I have tested the flask probe without the mantel ON. I have added in the flask water with different temperatures and the probe indicated the correct temps.
But I found the culprit! When heating using the mantel, the probe measures the temp in the liquid but my mantel heats a lot all around the flask! So the vapors that come out of the liquid get extra heated by the mantel’s heat in their way to the head thermometer. That is the reason that the head thermometer reads a much higher temp.
Here are the temps measured: flask probe temp 36C, head temp 65C and the interior mantel temp >100C!!
I have no idea why the mantel went so high!! Maybe I have missed some mantel’s settings (it has A LOT of settings and I have no user manual to figure them out…)
Basically, I’m expecting for the mantel, if I set it to 40C to stay at 40C at all time! Not to go to over 100C!

There are several treads of mantels gooing haywire maybe gives some info

If your removing solvent, it could be auto refrigerating it self and makin the mantle over shoot.

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That could be a good explanation…I will try to to see how it controls the temp without any flask…just the probe in the mantel @ 40C . Let’s see if it goes crazy in this situation too

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Mantle temp problem solved!
As I said, the mantle has some hidden settings (I need to press a button for 6 seconds to get there…) Obviously, I have no info on what these settings are…but I found one setting that has the value 30…I lowered the value to 3 and saved it.
Now if I set the mantel to 40C it will go gradually with 3 seconds heating steps and it will stop at 40C while the probe will go only 2-3 degrees over 40!!
So, having that initial setting of value 30, the mantel will go in 30 seconds of full heating steps!!! overshooting the needed value with a lot!!!
It looks like the mantel is very smart but dangerous without a proper user’s manual!
NOTE: The above tests were done with NO flask in the mantle…just the probe.
When adding the flask with liquid, there is another setting that has to be adjusted…like the waiting time before checking the temp. The mantle should have to wait an amount of time (for the liquid to get heated) before checking the current temp and applying heat again.

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Slow af

Have a pic of your mantle?


it is ZNCLTS series made in China

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Also here are the hidden settings that I have no idea what they are for…

Right now I have contacted the producer of this mantle and he will tell me ho to do the settings…

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O nice post them once known !!!

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Actually the producer just told me that he will send me a video on how it works.
Obviously I’ll post it here once received.

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Right on…I was hoping it was my mantle :joy:

I’m sure someone will find that info useful in the future.

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