Hilski - 16-2-2007 at 19:01
I need to come up with a way to heat the contents of a 3 or 5 gallon HDPE bucket to 50C - 60C. The heat will need to be external (no immersion type
heaters). The bucket will contain ~60% H2SO4 and Mn based oxidizers along with some organic compound to be oxidized. (Toluenes, ethanol, methanol,
maybe a couple other alcohols) There will be very good mechanical stirring, so the reactions should not take too long to complete once the the target
temp is reached. Some of the alcohols may react at room temp, but I'm pretty sure that toluene will not, so at least some heating is definitely
required.
Thanks in advance.
Ozone - 16-2-2007 at 19:47
Hilski,
This might work, but you are skating on thin ice at 60°C. Hot H2SO4 is one of the few things that can semi-solublize HPDE via sulfonation. It can
also, apparently, be nitrated
. In addition to this the 80°C marks solubility in
aromatic, viz. toluene and chlorinated solvents. At the very least, you might see softening sufficient to cause slumping and spillage...not good.
If you must persue this, I would hihgly suggest at least first testing with water to make sure that softening, even with water, at your temperature
does not cause your vessel to slump under the weight of the contents. If this occurs--even a little--I would be wary of filling it with H2SO4, toluene
and adding heat.
I've attached some reference material.
Cheers,
O3
Attachment: Polyethylene_01.pdf (240kB)
This file has been downloaded 1641 times
Rosco Bodine - 16-2-2007 at 20:08
A hot water bath should work okay .
Put the bucket in a poly washtub
half full of very hot water , or use a picnic cooler ,
and pour a few pots of boiling water around
the bucket . It shouldn't take much heat absorption
to heat it up to 50 or 60C ....which isn't very warm .
However .....
Several glass aquarium heaters would probably work ,
but I guess that is a sort of immersion heater .
You could wrap the outside of the black bucket
with fiberglass insulation and set it on a thick sheet
of styrofoam . You might have to tinker with the thermostats to increase their maximum cutout temperature , or pin 'em so they stay on
and use a variac or dimmer control to throttle them .
Alternately ....
You might be able to use AC from a variac ,
and use the resistance of the electrolyte as a heating element of sorts .....and heat it directly .
At 60% H2SO4 and 60C .....you probably will be alright with HDPE , good to 110C perhaps better with polypropylene good to 120C ....but of course the
toluene and H2SO4
derates that figure for water considerably . My guess
is you will be okay with HDPE for a few runs anyway .
If the poly bucket isn't tough enough , you might have to use
a PFA bucket liner
http://www.welchfluorocarbon.com/TeflonDrumLinerTeflonPailLi...
This scenario is really one where a large crock pot having
a removable corningware liner is something that would be
the simplest solution .
[Edited on 17-2-2007 by Rosco Bodine]
Hilski - 16-2-2007 at 21:58
Thanks for the warnings, and the document Ozone. I agree that I may have been walking a fine line at 60C with H2SO4, but I felt it would be safe
judging by the information I was able to gather from various chemical resistance information sources. For some reason though, it never occurred to me
to check the ratings for that material as it relates to toluene. As Roscoe suggested, it would probably be better to go with polypropylene instead.
I like the hell out of those PTFE can liners Roscoe. Thanks for the link. If one had some of those, the bucket material wouldn't matter. So a steel
bucket, or small steel garbage can could be lined with the can liners and heated in a conventional manner and one wouldn't have to worry about melting
plastic buckets, or breaking huge glass containers etc. It looks like I shall have to convince the *important people* at work that we just HAVE to
start stocking those can liners in the parts room - For safety reasons, of course. 
Ozone - 16-2-2007 at 22:10
Good Find Roscoe!
PTFE in a format like this is the shite! The "important people just love anything that has to do with *safety*; in fact, they are so governed by that
word that manipulation is enabled (shit-eating-grin emoticon required here).
Goodnight all,
O3
12AX7 - 16-2-2007 at 22:54
Point an electromagnetic radiation source at it. Probably you can put shielding around the sides and point a magnetron at the bottom...basically sit
its ass on top of a jerry-rigged microwave oven. If safety is an issue, you can move the safety interlock switches to around the pail. And maybe a
conductivity sensor in case it starts leaking.
Conduction warming isn't going to work very well, but if slowness is acceptable, a bath is definetly the most gentle method.
Tim
chemrox - 16-2-2007 at 23:52
I saw a heating tape at a beer makers' supply store. Pipettes, graduates, tubing, oil extractors, all kinds of goodies there. The heating tape was
made for the type of vessel you described .. 5 gals.