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Author: Subject: Homemade evaporation setup - is this plausible?
International Hazard

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[*] posted on 17-10-2015 at 03:09
Homemade evaporation setup - is this plausible?

As I'm a Newb to chem for the most part (read a lot, little hands on) I'm wondering how to build an evaporation setup which is faster than an evap dish and fan.

Here is the idea:

PVC tube (say 3" diam & 12" long) with end caps on both sides (in & out) & a vinyl hose barb on both ends. Fill tube with something like anhydrous MgSO4, Na/KOH (corn meal??) or whatever else would be good for for absorbing moisture from air.

Now the air can be heated before entering the desiccant tube, or not (depending upon what is being evaporated or the chem in the liquid to be evaporated).

An evaporation container will be devised , possible another 3" PVC tube coated with a chemical resistant epoxy of some type. An inlet valve with a check valve so the liquid can't flow back into the hose (and maybe an aerator screen on top of the valve. Some form of very fine mesh (Stainless??) will be immediately above the inlet valve (most likely the entire area of the tube so - Pi(((.5)Diameter)^2) - this should ensure as much surface area in the bubbles as possible. On the top of the me4dia evap tube is another vinyl hose barb which can be vented outside or run to a condenser.

What I am most concerned about is whether to use an air blower or a pump. The blower would be located before the desiccant while the pump would be located on the egress of the media evap container. The problem with the latter is that the pump will be exposed to the evaporated gases (solvents, water, etc) so that could eventually lead to complications (seizing) and possible failure unless expensive pumps were used that were non-corrosive. But, IDK if one method is significantly better than the other.

I plan on also creating something like a reverse condenser (bucket water @ specific temp with some metal piping) located prior to the desiccant input to heat (or cool I guess) the incoming air. This will be temp controlled in some method)

Another method for a more crude setup for evap'ing water would be a high CFM fan that sucks air over the top layer of the fluid and vent wherever needed. I would think a vacuum (shop vac) would probably work well for this. I kind of wish this was the only evap device I would need but this won't work for many projects.

Does anyone have any comments, suggestions, improvements or warnings about the first setup (especially the desiccant 0 would prefer a refreshable medium).
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International Hazard

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[*] posted on 17-10-2015 at 06:25

I am looking at improving my dessication equipment, sort of similar,
I am still at the beginning of learning chemistry, so wait for more informed suggestions from others ...

re. Pressure pump at intake or Vacuum pump at exit ?

Vacuum at the exit has several advantages;
. solvents (such as water, ethanol etc.) evaporate more easily with reduced pressure than with increased pressure
. a blockage in a pressurised system will build up pressure in the equipment,
although an explosion is possible, more likely is leakage of solvent(s), possibly as high speed jets in unexpected directions
. even if there are small leaks in your equipment with vacuum you can guarantee venting of any gas/vapour away from yourself and others

As you wrote, pump corrosion in vacuum mode is a concern, but from the (little) experience with my small pump,
the parts exposed to the pumped gas are mainly nylon and silicone

Small diaphragm pumps like this
are fairly corrosion resistant and can be used either a Pressure or Vacuum pump, also useful as a vacuum filtration pump.
I bought one of these
which can reduce the boiling point of water to about 60 C or pump a useful 20l/min.

of course if you can afford a rotary vane vacuum pump then you can boil off solvents at room temperature

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[*] posted on 17-10-2015 at 09:26

Use the power of radiation. My "drying oven" is a glass fish tank wrapped in aluminum foil. 2 65W incandescent bulbs are installed in the lid. Normally it doesn't seem like incandescent bulbs get warm enough for this, but it gets hotter than hell in there since very little of the radiation actually escapes (remember that incandescent bulbs output unholy amounts of infrared radiation). Vapors escape through small holes drilled in the lid so that drying can continue.

I had to make the lid out of plywood and covered the inside of it with aluminum foil, so it is vulnerable to chemical attack unlike the walls and floor. I covered it with plastic wrap to slow the process but it'll need replaced eventually - not a big deal.
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[*] posted on 17-10-2015 at 09:50

The use of heat in drying stuff can be as simple as putting it in a beaker on a hotplate.

Vacuum is used a lot as it lowers the boiling point.

It all depends what you're drying, and to what degree of dryness.

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[*] posted on 20-10-2015 at 21:50

I have bubbled air thru a hot liquid to help drive off the liquid.

But, just bubbling air thru it will let water in the air get into the liquid.

So I put the fish tank pump into the bottom of a 1/2 gallon coffee tin a filled it up with 'dryrid', you can use silica gell too.
And then pu the lid back on after gutting two chunks out of the lip to let the wires and hose thru.

It worked really well. The drier did make a difference to how long it took to.
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International Hazard

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[*] posted on 21-10-2015 at 01:07

just a tip for plant material, if you have alot to dry then hang it up in a shed or whatever and place a fan nearby pointing at it. Ant air flow over plant material dries it very quick.

Also fridges dry things really well, its good for thing that dont like heat! Fridges have extremely low humidity, leave cooked chicken uncovered in a fridge and it goes hard as rock in a couple of days.

In my desiccator I just use very dry table salt mixed with dry rice grains, this seems to work well as a desiccator and to regenerate just heat the salt and rice in a pan until all powdery again

Dont ask me, I only know enough to be dangerous
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[*] posted on 21-10-2015 at 06:19

Once I tried freeze drying whole (small) mushrooms to preserve their natural shape as much as possible. I intended to impregnate them with something inert (DCM dissolved polistyrene seemed to be a good choice at first) after drying.

Anyway my freeze-drier was very simple: I put a fair ammount of activated silica-gel drying agent into an ampty (and dry) pickle jar, around 800 ml, then put a layer of tissue paper over it, then the small mushrooms (about 3-4 cm length), one or two pieces at most. Then closed the lid and put the whole shebang into the freezer (-18 C or so) for a few weeks.

You know what? It did work! (To my surprise.)
The mushrooms remained mushrooms, though a bit wrinkled, but became powder dry!
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