quantumcorespacealchemyst
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fluid pump and tubing capable of pumping low temperature 0C to -78C temp Acetone
what kind of fluid pump and tubing can handle pumping Acetone?
i am uncertain what kind of setup can run very cold temperatures in a short path distillation condenser, or any condenser.
i figure using a dry ice/Acetone bath and also pumping it through the condenser would work well for extreme situations.
i am unsure how to go about it. i am figuring on using the cooling pan/freezer thing from a mini fridge (the part in the freezer) and maybe make an
aerogel insulated reservoir. i don't know how cold that would get, i guess cold, but i don't know what can withstand Acetone, especially at regular
temperature.
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XeonTheMGPony
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PTFE tubing will do cryogenic temps, as for a pump that I am not sure, Naturaly it'd have to be possitive displacement
what are you trying to distill?
if you can precool the hx you could flood it with propane liquid, this will boil at -42c at sea level (14.5psi)
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BromicAcid
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Pumping acetone cooled directly with dry ice is generally a bad idea. The acetone becomes saturated with carbon dioxide and the slightest bit of
negative pressure (such as the low-pressure zones in a pump head) will cause that gas to escape killing your pump speed. So you'll need a separate
reservoir to hold your liquid and cool it externally.
I have seen magnetic drive centrifugal pumps used for these kinds of temperature situations. More useful for you I have seen peristaltic pumps using
PTFE tubing (check out Masterflex LS) work at these kinds of temperatures and they can be had on eBay for a good deal once in a while.
What I would see as the best option however would be to just use a cold finger. You can buy distillation heads that do not have a condenser as a part of them, instead they have a 24/40 neck or other joint where a
condenser can be attached, put a cold finger there instead and fill with dry ice / acetone. I have seen that setup used for fractional distillation
of low boilers before. I have also used fractional distillation heads with a cold finger built into them instead of a standard condenser but since I
cannot find a photo of one online I think they may be custom pieces. Still, evaluate using a cold finger instead, they also sell dry ice condensers that can be used in place of a regular vertical condenser and fed dry ice. Just remember if you're collecting that sort of
cryogenic distillate to bury your receiver in dry ice and you might want to put a cold finger on that as well.
One word of warning, although PTFE does not become brittle at these temperatures, it does shrink. I have had stopcocks that were tightened at room
temp leak absurdly bad at dry ice temps. Also remember to loosen them when you are done so they do not expand and crack the joint (I have forgotten
to loosen them before without them cracking anything but it stands to reason).
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Dr.Bob
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Gore sells some special tubing for peristalitic pumps that will handle cyrogenic temps, it costs a bundle. Some silicone tubing will also handle
that, but it is also costly. I would also try a cold finger or dewar condenser, they are ideal for that type of work.
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DJF90
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Quote: Originally posted by quantumcorespacealchemyst  |
i am unsure how to go about it. i am figuring on using the cooling pan/freezer thing from a mini fridge (the part in the freezer) and maybe make an
aerogel insulated reservoir. i don't know how cold that would get, i guess cold, but i don't know what can withstand Acetone, especially at regular
temperature.
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You certainly won't get to -78 *C like this, and even if you did the thermal capacity of the system would not be sufficient enough to cool anything
meaningful. A centrifugal pump is certainly the way to go as far as pumping low temperature coolants, but I'd follow the advice of the others and try
a dewar condenser filled with acetone-dry ice if that provides a suitable temperature.
[Edited on 7-3-2016 by DJF90]
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ave369
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Would a modified plastic hand-pumped garden sprayer work? It works on positive pressure, rather than negative one. Fill it with acetone/dry ice, close
the lid and pump air into it until the coolant comes squirting from the sprayer nozzle into a tube/whatever.
Smells like ammonia....
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Dr.Bob
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Most consumer plastics become brittle and low temps, and many dissolve in acetone, so not likely to work, and the chance of it over pressuring with
dry ice make it very dangerous. Stick to safe and simple things like a cold finger or dewar condenser.
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