Natures Natrium
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A Small, Simple Steam Distillation Device
A Small, Simple Steam Distillation Device
Foreword: I haven't been active on these forums for a long time. For reasons logical and necessary, I haven't been engaged at all in the hobby of
chemistry. For a time, exploration of electronics occupied a good bit of my free time. However, now that I am the proud owner of the property that
contains my hat rack, I feel compelled to explore once more, now that I can do so in an organized manner with a mind to the safety of myself and
others. To that point, I have begun construction of a small lab which will be detailed in a distant post. It is essentially a small 8'X 7' shed, but
will contain running water, electricity, and most importantly, a fume hood. No more learning to hold my breath like a japanese pearl diver while an
out of control reaction spews vapors of nitrogen dioxide into the immediate vicinity. I actually got up to around 2 minutes at one point, while
engaged in mild physical activity.
Digression aside, I really want to contribute more to this community. The volume of knowledge here is excellent, even if the noise to decibel ratio
is a bit high at times.
To that end, I decided to build a steam distillation device based on a few criteria, document the process, and share it with you all. I hope someone
finds it useful.
The criteria I started with are as follows:
-No Glass
While invaluable for most of our pursuits, its particular chemical
inertness and translucency aren't really valuable for this purpose.
Combined with it's expense and susceptibility to physical damage,
it doesn't make sense to use it in this application.
-Cheap
I don't have a lot of money, and I don't want to spend what I do
have where it really isn't needed. In addition, I don't have free
access to cnc machines or other modern metal carving devices.
-Big Enough (for me)
Steam distillation require significant volumes for small returns.
Balanced to that fact is the cost of the material to be distilled
and that I only need small volumes of extracts to experiment with.
-Must be easy to disassemble and reassemble
Difficulties in cleaning and loading material would make the device
more trouble than it was worth.
The Point:
Yes, two different sized pressure cookers, stored for years in our attic (like most of pressure cookers, I imagine). The seals on these were still in
good condition (pliable rubber, no tears). The pots were scrubbed thoroughly with dish soup and a plastic scrubbing pad. One handle was slightly
loose, easily remedied in a few seconds with a screw driver. These required some minimum of effort to adapt to my purpose though.
First step was to remove all the valves on top of the cooker. These two different models had a different mechanism for regulating pressure. One of
them simply unscrewed, the other appeared to be riveted. Once the smaller pot valve is removed, I drilled out the center hold on the smaller pot with
a 1/2" drill bit. This was just slightly too small for the 1/2" copper pipe to fit through, and had to be reamed out a bit with the drill bit on high
in steady circles with a relatively light pressure until the hole was big enough, but still round. Since the pot is aluminum, this did not take
terribly long.
The larger pot had the riveted pressure valve, but I didn't remove it for reasons that will become obvious. On the lid, up to the valve, the lid
swept upward. This part needed to be removed so that the flat bottom of the smaller pot would sit flush to the lid of the larger pot. Thus, a square
and a sharpie were employed:
Next, four holes were drilled at the corners with the 1/2" drill bit. Despite advertisements to the contrary, the bit tended to walk quite a bit at
first, so my holes ended up skewed, but not unworkable:
Originally, I had planned to use a jig with a metal blade, but I couldn't find any of the blades for it, so I resorted to a pneumatic saw, which got
the job done just fine.
This was as good a time as any to take an iron file to the holes and cuts and deburr. I figured I would make mention of this as it is so often
forgotten or overlooked, and can introduce unexpected problems down the road. Always deburr.
Next, I lined up the smaller pot on the big one. By chance, an excellent match. I also took some time with a standard claw hammer and some patience
to level the surface of both the smaller pot bottom and the big pot top. When I was done there was very little light in between the two. With
aluminum, lots of relatively gentle taps to change the profile of the metal without creating dents from the hammer head seemed to work best.
The next step involved drilling a small hole (I used 5/32", a good fit to the shaft of the self-tapping screws I use later on) in the small pot. It
had to be near the edge, but not so far it would interfere with the sealant I was going to use. After the smaller pot had its hole, I lined the two
pots up, and holding them in place as best I could, drilled through the hole into the lid of the big pot. Might be a better way to do this, but I
couldn't figure it out.
Finally, after deburring, the first self tapper was run in using a drill.
Next, the other three holes were drilled, and the first screw taken out.
Having recently completed some automobile work, I had a few tubes of silicone gasket kicking around. Maybe perhaps overkill, but I felt confident it
would stand up to repeated heating and cooling cycles, as well as any pressure or oils from the material to be extracted. If I did it again, I would
use the same.
Degreased the surfaces with a paper towel and some chlorinated brake cleaner.
Applied an extra thick bead all the way around the outside rim.
Put the pieces together, and ran in the self tappers the first half with a drill, and the second half by hand with a ratcheting socket wrench. Do not
tighten these all the way down, they should just barely be tight by hand operated wrench. A good indicator is the silicone itself:
You want the silicone to just begin to bulge out the sides. The seal must be left alone to cure for the time indicated on the packaging, which as I
recall was an hour or two. In the meantime:
Propane torch, copper pipe cutter, an elbow and a straight joint, a length of extra copper pipe kicking about, some solder and some flux. First, a
piece of copper pipe was cut that would almost allow the elbow and straight joint to touch each other when the (roughly 1 inch) piece of copper pipe
was inserted into both.
The straight joint was soldered on first, and then inserted into the lid thus:
Then, the elbow was soldered onto the other side. This proved to be an absolute pain in the ass. The aluminum lid wicked all the heat away like the
heat sink it is, and made it very difficult to get a good, sealed joint. In addition, I was concerned about excess heat damaging the rubber seal in
the inside of the pot lid. The seal couldn't be removed on its own. Finally, after several tries, I managed to get it done.
Next, I cut a piece of PVC pipe to use as the condenser. I had a real internal debate about the length of this, but finally settled on a shorter
condenser towards the end of the copper pipe that would allow as much heat to dissipate by air as possible.
I wanted to add some hose barbs to the pipe, for easy connect and disconnect of water source.
So, this was not a great way to do this. I opted to drill out holes in the pvc pipe with a wood paddle bit, just slightly smaller than the plastic
threads on the house barbs. Of course, those threads just got smashed when I tried to thread them in. So, I had to use the pneumatic saw to slightly
widen the holes until they thread in.
There was no way that was going to hold water, so I had to apply some more of the silicone sealant. This is not how this sealant should be used, it
is designed to be caught between 2 hard surfaces. Very suboptimal. When I did finally put water to it, they both leaked, and both were patched with
gorilla glue. I dont expect these to last very long, and will need to be replaced with a better solution.
Okay, so that took a few hours, and the silicone on the pot had set. Took the hand ratcheting socket wrench, and tightened all four bolts down nice
and tight. It took roughly another 1/2 to 3/4 of a turn each. I broke out the 1/8" and 1/4" drill bits, and drilled the following rough pattern in
the bottom of the small pot (and subsequently, through the lid of the big pot). The pattern I chose was the result of thinking that since all the
steam was exiting center top, and since most of the center holes had less depth the steam would be more apt to pass through the center. In
retrospect, not sure if it actually mattered.
Next, soldered the big pipe onto the elbow on the small pot lid. The aluminum heat sink effect wasn't as bad this time.
Put everything except the condenser together. Note the rubber grommet in between the copper pipe and the lid handle, and the pipe clamp tightening
them together. Decided some extra support was needed for the elbow joint given the crappy soldering, and this allowed me to give it while still being
able to take the lid of the smaller pot off.
Next, two rubber pvc pipe endcaps were purchased, and the 1/2" bit was used to drill a hole in the center of each. Steady pressure and medium drill
speed seemed best. One of these was slid onto the copper pipe, then the pvc condenser (whose silicone had set by this point), then the other endcap.
These three pieces were slid together, and the pipe clamps tightened.
After 24 hours to allow full cure of seals, the device was tested on a flat top stove with a full load of water and nothing in the small pot. Except
for the aforementioned minor leaks around the hose barbs of the condenser, it performed well.
One thing I had expected and was in fact verified is that the speed at which the coolant heated up was quite rapid when distilling steam. Ideally, I
would like to combine a 5-gallon bucket, a motorcycle or similarly sized radiator, and a suitable pump. I'm not much for just constantly running
water down the drain for hours.
Unfortunately, the first thing I had planned to steam distill was some basil from our garden, which has since perished. I may try something
relatively irrelevant but cheap and readily available (grass clippings or leaves from a local tree) just for fun.
I wont be able to try an analysis until I get my lab set up, and that is going to take quite some time.
The last thing I want to mention is that I recognize the failure of this document as a how-to, in that it is not readily reproducible. Even though it
is highly unlikely that anyone has these two exact pressure cookers kicking around, it is my hope that some the techniques and mistakes displayed here
will prove valuable to others pursuing a similar device.
\"The man who does not read good books has no advantage over the man who cannot read them.\" - Mark Twain (1835-1910)
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bbartlog
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Nice to see a project like this documented, even if (as you say) it is unlikely that someone else will want to reproduce it exactly.
| Quote: | | drilled at the corners with the 1/2" drill bit. Despite advertisements to the contrary, the bit tended to walk quite a bit at first...
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I always first drill a small pilot hole when working with a bit that large. Helps stop it from walking.
The other thing I would say concerning the choice of scavenged materials is that pressure cooker bodies are overkill for what is after all an
unpressurized setup. A large canning pot or stockpot would be a more sensible choice, if it were available (thinner walled, lighter, cheaper...). Of
course if pressure cookers is what you have then pressure cookers is what you'll use... and maybe you can make something that will be readily
adaptable to vacuum distillation with a few changes 
The less you bet, the more you lose when you win.
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chemrox
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I tried this with aluminum parts a few years ago and made soap. The main culprit was the gasket on the Al canning vessel I was steaming the oregano
in. Instead of coming over too much steam escaped and I had wilted herbs and soap when I opened it up. The stainless replacement was harder to drill
and tap but it worked a lot better and didn't cause saponification of the oils.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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Natures Natrium
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Thanks for the comments.
A pilot hole would have been a good idea. In fact, I did use pilot holes for the self tapper screws, as they tend to not so much walk as dance like
ballerinas across a flat surface. I suspect that the main reason I didn't for those particular holes is apathy by logic, though I don't remember for
sure.
I have been considering what other application I could put it to. Haven't really come up with much, to be honest. As for vacuum distillations, the
one thing I could not bear to part with those years ago was all that beautiful glass.  So, I have a 24/40 setup to deal with that.
As for the aluminum causing saponification, that is concerning. Until I get to the point of actually steam distilling a material, I wont be able to
confirm your statement.
So, was your stainless steel replacement leak free? Given the small yields from this procedure, I would imagine that any loss is to be avoided.
How did that go for you in the end? Were you able to produce food/experimentation/home remedy quantities of essential oils?
\"The man who does not read good books has no advantage over the man who cannot read them.\" - Mark Twain (1835-1910)
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Natures Natrium
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Just a quick note: Tested it for the first time, steam distilled .9 kg (2lb) of carrots, store bought, with slightly less than 3.7L (1 gal) of water.
The collected water was salted and cooled in the fridge. There was a rather thin layer of oil on top, which smelled as I thought the essential oil
of carrots should smell like, never having smelled it before.
As this was a trial run, and my separatory funnel is currently sequestered in a dusty box somewhere, I was unable to quantify or analyze the oil.
Originally, I had planned to steam distill some citrus fruit rinds (orange and lemon in particular), but considering their high acidity and the fact
that the distiller is made of aluminum, I decided against it.
Someday, when I have my lab set up, I will try again with something more classic and commercially available (for reference).
\"The man who does not read good books has no advantage over the man who cannot read them.\" - Mark Twain (1835-1910)
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bbartlog
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The rinds shouldn't be significantly acidic. I expect you could distill citrus rinds in an aluminum setup without trouble. They're a nice choice in
that they have a fairly good essential oil content.
The less you bet, the more you lose when you win.
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Natures Natrium
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Hmm, I may have a go of it someday. Right now I am in full on planning mode for my humble lab space. Next time I steam distill some oil I want to be
able to clean it up and keep it.
\"The man who does not read good books has no advantage over the man who cannot read them.\" - Mark Twain (1835-1910)
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Twospoons
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If you are worried about the aluminium doing nasty things to your oils you might consider getting the pots hard anodized. It shouldn't cost much to
do, and it puts a nice inert layer of hard oxide on the surface. If you have a suitable DC power supply you could do it yourself.
Helicopter: "helico" -> spiral, "pter" -> with wings
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chemrox
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The stainless setup was leak free after some hunting and tightening with Teflon tape and mechanics wrenches. I used a drill press for all the
drilling; using jigs and wedges to hold parts when needed. That was important when it came to time to cut the threads. A sloppy hole would have
allowed the tap to wander all over the place and it would have leaked no matter what I did. I also like the hard anodizing idea. Seems like one
would need a bath larger than the vessels...
[Edited on 6-8-2012 by chemrox]
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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