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Author: Subject: Birkeland-Eyde reactor for making nitric acid.
axehandle

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Birkeland-Eyde reactor for making nitric acid.

I'm constructing one, and have made a web page which documents my progress and is continously updated.

Comments, critizism, suggestions, questions etcetera are most welcome.

http://species8472.dyndns.org/no2/no2.html

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axehandle

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22 views, lots in the weblog, but no replies. I guess I'm the 1st one attempting this then. I'll let you all know how it goes.

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Turel
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Beating me to it, eh?

I'm constructing one as well, albeit a bit different than the one featured in that link.

I was not going to mention anything until it was done and successful, but you have beat me to it. So to answer your question, I suppose you are the first here to fabricate your own reactor, but not the first to consider and design one.

-T

[Edited on 12-2-2004 by Turel]
axehandle

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Heh. Are yours more sophisticated than mine (e.g. using magnetic fields and DC arcs to form an oval arc)? In that case let's call it a draw.

Seriously though, how's yours constructed?

Edit: I think we could both benefit from a mutual exchange of design information to optimize our yields. The patent has expired long since....

This is my 6th reactor, all the previous ones have been made of glass and failed due to thermal stress; the 5th one actually employed watercooled hollow electrodes(which failed because of the conductivity of condensed water). This is the first one that actually seems to work, albeit I'll probably have to run it in 15 minute cycles for cooling reasons (15 minutes NST on, 15 minutes NST off, etc).

Regards,
/A

[Edited on 2004-2-12 by axehandle]

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Turel
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No magnets.

I was surprised to see the Jacob's Ladder-like arc in your reactor. I thought I was the first to decide to employ a travelling arc.

Air is passed through a widening travelling arc much like yours, only larger. The air is introduced into a closed vessel that encompases the arc, in the shape of a hand fan. It is introduced at the narrow end, so that as it expands over the increasing width, it slows and repeated arc exposure is forced.

The outputted gas stream is combined with a small warm oxygen stream, which pass through a condenser to draw out any formed NO2 as N2O4 for collection. The gas stream is then recirculated back through the arc for a repeated pass.

I am thinking of including an oxygen sensor or two in the line, to monitor O2 content of the airstream at the start of the reaction, and also at the condenser. I have NO2 sensors post condenser to make sure that no NO2 escapes condensation and reenters the initial reacting chamber.

The reaction of NO2 and H2O is performed in a seperate apparatus, and utilizes a cupric nitrate catalyst in the water solution. NO2 and Oxygen are bubbled through a fine atomizer at the bottom of the solution bath, which is stirred gently.

I am still constructing my apparatus, and working out exactly what power specifications to use for the arc.

-T
axehandle

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Then you beat me. My setup is much simpler.

However, forget the oxygen stream. O3 is produced in the arc as well, giving an ample supply of O.

I've also been thinking about repeated passes, but concluded that the same can be achieved by a low air pass-through rate.

But I still considered myself beaten. Your design is much better, albeit it's only in the theoretical stage.

If you want some advice, I would say: The fewer parts, the better. That has been my experience during my experiments with the previous 5 failed rectors.

Who cares if the yield is e.g 50% or 100%? Electricity is cheap, I've plenty of both nuclear and water power available here...

But let's see who's design works best, shall we? What's your estimated time to completion of the apparatus?

Quote from you:
"I thought I was the first to decide to employ a travelling arc."

My reply: The more air exposed to the plasma, the larger the yield, and great minds think alike...

You wanted power requirements. I actually think that my NST it a bit too much. Dissipating 540W of power ain't easy. If I were you, I would stay at the same voltage as mine (9kV) but use an NST of lower power.

[Edited on 2004-2-12 by axehandle]

[Edited on 2004-2-12 by axehandle]

[Edited on 2004-2-12 by axehandle]

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Turel
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I Care! (kidding, kidding)

Agreed, 50% would actually be a fabulous yield in my opinion, since I don't pay for electricity at all. (grin)

But I do care that it works, and works reliably. The ideal construction would be a small size unit that can be used in continuous unmonitored operation for say 5 days or so. Throughput is not important, but reliability/stability and it working to begin with are.

This is more than a 'gee it would be cool' project; I originally started on this because of a need for relatively pure HNO3, and extended use of it; say 500mL/week reliably.

The reason for having the two reactions seperated is because when NO2 reacts with water it does not produce clean HNO3. Rather it begins to produce a mixture of HNO3 and HNO2. As the HNO3/H2O concentration increases, some of the HNO2 is oxidized, destroying both HNO3 and HNO2 in favor is solvated oxides, and other side reactions I am sure.

The cupric nitrate acts as an oxidation catalyst, mediating the oxidation of HNO2 with O2. Cu+2 ion oxidizes nitrite ion to nitrogen dioxide, which reacts with water in the way we are familiar. The oxygen oxidizes the formed cuprous ion, and lends itself to the creation of water, which quantitatively is consumed by the induced reaction of the formed NO2 with water. It all balances out to help HNO2 oxidize to HNO3.

For air, the oxygen content is only ~20% or so, and the arc favors NO production over O3, so I would assume that very little O3 is produced. O3 is favored by lower temperature arcs, and the arc you showed is quite plasmatic.

Have you tested your output gas for O3? Have you successfully produced NO2? I have not begun testing yet myself. If you need NO2 sensors let me know.
axehandle

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My reason for building it is that purchase of acids are restricted in my country.

No, heven't tested for O3 (apart from nasal examination =), but I constructed a prototype and made 20cc of nitric acid which I "tested" by tasting it. It was the most acidic, vicious thing I've ever tasted.

Edit: tested with litmus paper as well, turned bright red instantly

I would be very interested in NO2 sensors, provided they can detect concentration as well as presence.

[Edited on 2004-2-12 by axehandle]

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Turel
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Congratulations

Im happy to hear that you were successful.

How long did it take you to produce that 20cc?

And no, actually the sensors will only detect the presence of NO2, and to not show a concentration.
axehandle

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It took about 20 minutes. I have absolutely no idea what concentration i got though. But The spot on my tongue where I tasted a drop turned yellow, which is a good sign I suppose =)

Edit: I suppose this would be a sign of N2O4 produced in the arc, which is very good. I don't want to spend the money required for an oxygen tank.

Edit: Perhaps a REALLY hot arc, like mine, produces N2O4 in significant quantities? I don't know.

Edit: I'm running the reactor now, using a 15minute resolution timer (15min on, 15min to cool). Seems to work so far, no leaks anyway. I'll know when i taste the product =)

[Edited on 2004-2-12 by axehandle]

[Edited on 2004-2-12 by axehandle]

[Edited on 2004-2-12 by axehandle]

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Hermes_Trismegistus
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Wow, I am really impressed.

with everything except the "taste test"

perhaps you could just titrate (until neutral) a known concentration of either NaOH or even (ghetto prep) a known amount of a commercial antacid tablet/s to find out the HNO3 concentration.

Then extrapolate time v.s. production.

WoW!

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axehandle

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Thank you.

The taste test was due to naïvete...... I couldn't imagine that such a short run would work.

Pity I don't have a titration thingy, you know what I mean, the one with a lever and lines indicating volume. I don't even have a scale capable of more than +/- 1 g resolution. I'll have to buy lots of equipment, and right now I'm low on cash due to my recent platinum wire order.

But I _will_ measure the density and compare it to a chart I found here on the board. That will only take a large accurate
volume measurement thingy (what the hell are those called in English anyway?) + my scale.

Right now though, I'm going to construct a larger reactor (bigger clay pots...) to get rid of the heating problem that forces me to use a 50% duty cycle. Then I can run 24/7!

[Edited on 2004-2-13 by axehandle]

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Tacho
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Awesome!

This is the most impressive thing I have read in this forum lately. It could turn out to be a simple way to provide HNO3 to the amateur lab.

axehandle, your design is better than good: it's done! Just don't taste it anymore ok?

I have made an ozone gererator that used a flyback (tv) transformer and ONE pnp transistor, plus a couple of components. It is rather simple, the spark is long but not very strong due to low wattage. The advantage is that the only thing that really heats up is the transistor.

I would be glad to give you details if you think it could help.

Keep us informed.
axehandle

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Well thank you! That takes some of the frustration of building 5 non-working reactors before this one away.

But my design is NOT better than good. I'm going to do some improvements today:

1) Using larger pots to allow for continous running by eliminating the heat problem. This also allows for longer steel rods, exposing more air to the arc.

Edit: I got a pair directly from IKEA, very nice (and EXPENSIVE) pots..... 7 each sigh. 2) Connecting 2 small lengths of PVC hose to the glass pipe at the bottom of the bubblers, each with 40 1.5mm holes drilled along their lengths to increase gas mix to water exposure. Edit: Done, let's see the result. 3) Construct a new jacob's ladder, which starts with a small gap at the bottom, then expands, then contracts again to form a small gap at the top. This is cosmetic: Every time the arc breaks at the top of my current construction, it seems radio waves are generated, making these incredibly annoying clicking sounds in my loudspeakers. This doesn't happen as long as the arc is "on". Edit: Rethought. That model would require air to be injected from both ends with the reactor being aligned horizontally. I've decided to go for a more conventional approach, with a V shaped jacob's ladder. I procured a 1m long 8mm thick so-called silver-steel rod today. Cost me18 sigh.

4) Move the apparatus to the kitchen. The pumps are very loud. Or perhaps just moving the pumps to the kitchen and use a long hose.

5) Increase the length of the PVC hose connecting the reactor to the first bubbler, giving the NO longer time to become NO2. The air flow is a bit fast, but until my next reactor it has to be for cooling reasons.

6) Perhaps add a third bubbler. Those airtight food glass jars cost only about $3 each. About the ozone: I think my spark already generates some of it. And I will keep you all informed. I'll update the web page for every step. Tasting it? Never again. I just recently dipped a blue litmus paper into the first bubbler. It turned red. VICTORY! But as I said, I'm going to make improvements. As you said, it could turn out to be a way of supplying nitric acid to the amateur lab. The only caveat is that the NST was quite expensive (approx.$200). But it will probably outlive me...

Edit: I've been thinking about getting a second NST and make a device made up of 2 jacob's ladders aligned 90 degrees to each other, but since my cash flow is right now negative, that will have to wait...

I looked into flyback transformers when I started research for this project. As it turned out, they were impossible to buy, and I had/have no TV (don't watch TV) to dissect..... so I decided to go the whole way and buy a new NST with high power ratings.

[Edited on 2004-2-13 by axehandle]

[Edited on 2004-2-13 by axehandle]

[Edited on 2004-2-13 by axehandle]

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Turel
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Also

I totally forgot to ask. What color was your produced acid specimen?
axehandle

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Completely transparent.

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Saerynide
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I thought nitric acid was yellow

EDIT: WOW. What you did was amazing

[Edited on 14-2-2004 by Saerynide]
axehandle

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Actually the color was hard to tell when the amount produced consisted of some liquid on the bottom of a large vessel, the glass thereoff being not completelety colorless in itself, el cheapo as it is.

Nitric acid is only yellow if it has unreacted NO2 dissolved in it, btw.

It was definitely a very strong acid, though.

Edit: The magical nitric acid machine, which I've been left running overnight, has a color in the first bubbler. I just can't say which, since I'm colorblind. Not a serious handicap, but I need a multimeter to sort resistors....

Edit: Btw, I changed the duty cycle to 30mins on, 15mins off, etc. The silicone stands up to this remarkably well.

Edit: It's Casco brand, and called "glassilikon".

[Edited on 2004-2-14 by axehandle]

[Edited on 2004-2-14 by axehandle]

[Edited on 2004-2-14 by axehandle]

[Edited on 2004-2-14 by axehandle]

[Edited on 2004-2-14 by axehandle]

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axehandle

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Thank you Saerynide. But there's nothing really amazing about it. When researching different methods of producing nitric acid à la Google, I stumbled across the name of a Norwegian named Birkeland.

A quick search of the USPTO database listed several patents regarding a plasma arc device for making nitric acid out of air and electricity.

After reading them, I said to myself: "I can do this", and then I proceeded doing it. Nothing ingenious about it, just a lot of persistance really.

Edit: Although there was _some_ science involved....

[Edited on 2004-2-14 by axehandle]

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axehandle

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Comments so far: It seems that the NO needs some time to become NO2, which is proven by the fast that the liquid in the second bubbler is more acidic than that in the first bubbler.

Hence I'm going to insert an empty "delay" bottle before the first bubbler. Gas / NO mixture will enter at the bottom and exit at the top.

I've also aquired two clay pots with a height of approx. 30cm and a diameter of about 20cm.

I've also aquired two new electrodes, both 50cm long, both of which I intend to place in a more conventional jacob's ladder configuration, with a 2 degree separation. Apart from this, I see no reason to change the reactor design. I might install a small feedback loop from the delay bottle to the reactor to increase the NO2 formation though.

I also intend to place the reactor inside a Faraday cage to get rid of the radio emissions. I just have to find a steel net of a sufficiently largel mesh number.

Edit: Ah, yes, I also intend to "build in" the probe of a digital steak thermometer in the reactor, to monitor the temperature.

Edit: I wonder if it's things like this that make my friends (the few I have) call me "McGyver"..............

[Edited on 2004-2-14 by axehandle]

[Edited on 2004-2-14 by axehandle]

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axehandle

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Comments on the new design (no pictures yet, I want the silicone to harden before moving the damned thing) are available at http://species8472.dyndns.org/no2/no2_2.html

in case you're all interested.

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axehandle

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I wonder who it it that keeps visiting my site using "windows 98". Windows 98 is a complete dungheap...... even compared to the other MS "operating systems", bar one: Millenium edition. That one is actually worse, believe it or not.

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leopard
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Axehandle this subject is also discussed in another thread "Alternative Method for HNO3 Synthesis". In this thread I briefly describe my experience with this method of producing Nitric Acid. Though my apparatus was very crude I was impressed with the results. Within minutes of running my setup the second jar filled with brown/red NO2 and within 20 hours I had about 50ml of Nitric Acid which yielded a heaping tablespoon of Urea Nitrate. The nice thing was the fact that it could run unattended. I performed this test in my garage and there was always a strong smell of NO2. Be carefull !! Good luck.
axehandle

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Thank you, and I will.

Edit: I still think my lovely reactor deserves an own thread though........ =)

Edit: New reactor has concrete hardening in both top and bottom. Have to wait at least 24 hours b4 dehydrating the bottom sigh...............

[Edited on 2004-2-14 by axehandle]

[Edited on 2004-2-14 by axehandle]

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 Sciencemadness Discussion Board » Special topics » Technochemistry » Birkeland-Eyde reactor for making nitric acid. Select A Forum Fundamentals   » Chemistry in General   » Organic Chemistry   » Reagents and Apparatus Acquisition   » Beginnings   » Miscellaneous   » The Wiki Special topics   » Technochemistry   » Energetic Materials   » Biochemistry   » Radiochemistry   » Computational Models and Techniques   » Prepublication   » References Non-chemistry   » Forum Matters   » Legal and Societal Issues   » Whimsy   » Detritus   » The Moderators' Lounge