Rotovap solvent recovery time?

I have a USA Labs 5L RE-10 and hoping to get some advice on water bath temperatures and an approximation on recovery time. Thanks!

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My water bath temp is 49c
Vac is -26.5hg
I use tap h20, run off goes to my plants
I get nearly 1gph

Im hoping if i upgrade to a big chiller, i can get better thoroughput.

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D, you got the 5L too?

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Yes @demontrich has the same 5L unit.

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Man I’m seriously considering ditching the 20L roto idea and building a vacuum pot still instead lol

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20 L gets about 3 gph when pimped out.

Anyone that claims more should prove it. Dont go breaking your glass trying to push extreme temperatures!

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I’m getting 5 liters per hour out of my 5l RE-501 China special. Probably a little less than that with draining the collection vessel, but I’m basing that off of timing it for 30 minutes and draining 2.5 liters from the collection flask. I’m running it at -22”hg and 70c rotating at 65rpm with ice water condensing everything and preheating material before it goes into the evaporation flask. I’m going to try using propylene glycol pre-chilled with frozen water bottles and pumping that through a copper coil submerged in a dry ice/acetone bath for -35c condensing with a 90c water bath and see if I can push that recovery rate a little higher. Anyone see any dangers of breaking glass running that cold?

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are you getting that depth with the water vac?

Oh, no. I’m using a Welch 2546b diaphragm pump. Just ice water for pumping through the condenser.

Wow 5L/hr is great!
I must be doing something wrong. I can only hit 4L/hr with that thing, how are u controlling your vac so it doesnt go too deep or fall behind?
Seems like babysitting it can get annoying, have u looked into a keg for a collection vessel?
I have -30C running thru my condenser coil right now, so -35C wont be a problem

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I have a tiny 3L buchi for r&d I run with dry ice and alcohol… gets a little over 3l per hour, and is prob -100ish when running lol… I think your be fine, THINK is the highlight, not sure about the Chinese glass…

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a used buchi vac controller is priceless in my opinion.

frees a lot of time.

I’ve bought 2 so far, and they dont hold the vac right, it always let’s it go down too far. Maybe I’m just having bad luck with em, I keep getting them for like 200 or 300

well dam, I only have picked up two but both seem to work great :man_shrugging:

note the offset and set the gauge accordingly?

That’s actually a really good idea! I could get a 1.5" tri-clamp to a 3/8th hose barb and connect the keg to the collection vessel output leaving the valve wide open. Afa vac level, I just max out my pump and let it ride. I was fiddling with vacuum control at first to run a lighter vacuum, but finally discovered that the max setting on that pump was perfect. One issue I’m having is etoh making it all the way to the pump (which can’t be good for it), but I’m hoping I can fix that issue by running my condenser at -35c. Or installing a cold trap.

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Even a cold trap doesnt fix the issue, but certinatly helps. I have one attached and always filled to the top with dry ice. It collects about 1 Liter per 20L recovered and that’s with the -30C condensing coils
I’m thinking about getting two of them, I’ll let u know if any makes it into the second one

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This is how your getting 5L/hr. Your ruining your pump ingesting etoh, unless your using a diaphram pump.

My vac is at -26hg, and my vapor line in the condenser hits just at the 2nd to last coil, and zero etoh in my vac lines.

48c water bath
98rpm

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It’s a diaphram pump, but it is the 25 Welch series and not the 20, so I know it’s not exactly rated for volatiles. What’s your recovery rate at such a low bath temp and high vac?

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I’m lucky to hit 4L/hr

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to get to over 3 l per hour on the 3l, I had to utilize a secondary cold trap.
I collected about 250ml per hour in said trap

also using a vac controller tho, so far less than high vacuum vac, and I run hot.

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