Sciencemadness Discussion Board

Birkeland-Eyde reactor for making nitric acid.

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chemoleo - 27-10-2008 at 17:48

Well the analytical proof for NO2- (nitrite ions, so you need to neutralise first) is with an H2SO4-acidified solution of FeSO4. Brown solution indicates nitrite.
Otherwise, couldn't you bubble the acid solution just with plain air for a while (with a condenser above), to oxidise all the nitrite to nitrate?

497 - 27-10-2008 at 20:47


Any ideas on why the absorption goes down so much? An industrial setup can achieve 40% acid before diminishing gains.

I would hazard a guess that this is happening because your N2O4 concentration is extremely low. Probably much lower than any commercially used process. The best concentration made (with any efficiency) by an electrical process was less than 2%, and on a very large scale. I bet you've got more like 0.6-0.2%... not surprising it is beginning to not be absorbed effectively, as the HNO3 conc goes up I think the equalibrium of

3HNO2 <-> HNO3 + 2NO + H2O

gets pushed to the left, and the resulting higher conc of HNO2 pushes

N2O3 + H2O <-> 2HNO2

to the left resulting in lower absorption, and when your partial pressure of N2O3 is so extremely low, it apparently doesn't take a very high conc of HNO3 to affect it. Plus when the NO fraction is so low, it takes so long for the NO to oxidize, I bet a fraction of it never even gets to N2O3 and results in an even lower partial pressure.

In my opinion, for this particular set up it would be more effective to simply absorb the gasses in a suspension of CaCO3. This will give you a mixture of Ca(NO3)2 and Ca(NO2)2 (if CaCO3 is excess) at high yield that will be relatively easy to decompose at into a concentrated N2O3 + N2O4 gas that can be easily absorbed, liquefied, etc. Either that or build a better arc system.. That is unless you're happy with 10 or 15% acid.

[Edited on 27-10-2008 by 497]

UncleJoe1985 - 29-10-2008 at 00:10


bubble the acid solution just with plain air for a while (with a condenser above), to oxidize all the nitrite to nitrate

I've let the solution sit for a day and the new concentration is 1.48 M = 8.9%, down from the original 1.61 M. I'm not sure about the exact decomposition path for HNO2, but a lower bound for [HNO2] when the reactor is running would be 0.127 M based on this drop.

kencbk - 16-6-2009 at 07:45

hi :)
This is a very interesting topic, I'm also planning to build my own reactor to make HNO3.
lately i was using a fly back to make NO2, well it did make a bit, but it take so long.

I'm wondering in a microwave transformer will do the job of making NO2 gas? i can't seem to find a neon sign transformer.

hissingnoise - 16-6-2009 at 08:10

I haven't read all posts but even with an NST the process is very inefficient and this is the reason the B-E process was discontinued in Norway all those years ago. . .
It's also an involved process with lethal voltages which makes HNO3 distillation from KNO3/H2SO4 look like a walk in the park by comparison!
I made a Jacob's Ladder many years ago using two NSTs in parallel; unfortunately I had to use a fridge compressor, the output of which contained oil droplets.
The absorbing solution became acidic over time and developed a yellow colour.
The colour was caused presumably by partly nitrated paraffins. . .
Distillation is easier and produces the strong acid I need!
Welcome to SciMad. . .

[Edited on 16-6-2009 by hissingnoise]

kencbk - 16-6-2009 at 17:23

thanks, yes but i can't obtain KNO3 or nitrate salts for such reaction to make nitric acid.

hissingnoise - 17-6-2009 at 03:55

KNO3 is a popular fertiliser---it's a matter of knowing where to look. . .
I got mine online because it works out cheaper than getting it locally.
It's 96% KNO3, so I have to crystallise to get usable purity.

kencbk - 23-11-2009 at 20:02

hi im back, ok i just want share what i came up with. a few months ago i was successful in building a birkeland eyde reactor (prototype reactor) here the video link BTW im building a better and more efficient version. thanks to this forum, helps alot thanks again. :)

hissingnoise - 24-11-2009 at 02:04

Nice work kencbk! It's vaguely similar to what I put together all those years ago!
I had the jar upside down (its lid was bakelite) and the electrodes were straight thin aluminium (welding) rods.
The arc had a longer travel and moved more slowly.
Airfeed was such that the amber colour was much darker (higher concentrations of NO2 dissolve and react more readily) and my delivery tube was much thinner than yours.
Also, I used a tall cylinder for absorption and had intended going on to a flint-packed PVC sink-waste tube down which water would have been sprayed for better absorption, but I lost interest around that point.

kencbk - 24-11-2009 at 04:07

thanks hissingnoise, well... i have to stick with this method of making nitric acid; i can't buy chemicals here because license is required. btw nice design, more NO2 gas. i appreciate your help. :D
i'll post the new video of the reactor when it works well and i'll try to titrate the solution to find the concentration.
thanks again.

hissingnoise - 24-11-2009 at 04:33

Don't expect great results initially, kencbk. . .

Contrabasso - 24-11-2009 at 11:55

Weighing or measuring the specific gravity of the product may assist in determining the product.

PolarSmokes - 29-11-2009 at 05:59

Has anyone thought of using a dessicator (otherwise there would be some vaporous nitric acid, which would eat away at the copper pipe), and using copper tubing, which is submersed in a superchilled ice bath, and out of the pre-cooler, have N2O4 solidify on a small peltier stack? The N2O4 could have a temperature regulated, dilute nitric acid drip on it, so that the N2O4 woudln't vaporize. I have never handled N2O4, but it may be one way of decreasing the time that it takes for the NO2 to disolve in water.

If this worked out good, even with the ice bath, and thermoelectric cooler, less NO2 would be wasted by the somewhat long periods that it takes for NO2 to disolve in water, which may result in a net increase in efficiency.

[Edited on 29-11-2009 by PolarSmokes]

hissingnoise - 29-11-2009 at 06:53

Dessicator? . .Peltier stack?
I don't know what you're talking about, PolarSmokes, and neither, I suspect, do you. . .
It should be obvious that copper tubing should never be used to carry substances that will readily attack it!
And NO2 dissolves in H2O to form HNO3 and HNO2.
Nitrous acid may oxidise by reaction with O, or it may be lost as NO.
If sufficient oxygen is present in the water and absorption-time is lengthy, all the NO may oxidise and react, forming HNO3.
But it's not as cut-and-dried as you seem to think.
Reading up on this subject might be useful. . .

PolarSmokes - 29-11-2009 at 07:45

I was under the impression that nitrogen dioxide did not react with copper, but nitric acid did. I know that nitrogen dioxide and water do disproportionate, so there will be some nitric oxide. However, it is a quite likely that nitric oxide would be more soluble in cooler water, versus warmer water, and may allow a larger portion of the nitric oxide to form nitrogen dioxide. However, without a peltier stack (stack of thermo-electric coolers), the nitrogen dioxide would not remain frozen.

My idea would not work with copper tubing if nitrogen dioxide DOES react with copper tubing. I am sure that over time, the copper will form a small, somewhat passivating layer of copper II oxide, however, this should be somewhat stable, as long as the pH remains above seven.

With the dessicator, functioning as a dehumidifier, there will only be very, very little [H+], so the copper should not be attacked by the nitrogen dioxide.

And FYI, I have used, and operated both dessicators, as well as peltier units. However, I have not stacked them, but I know people who have, and have achieved near dry-ice temperatures.

[Edited on 29-11-2009 by PolarSmokes]

[Edited on 29-11-2009 by PolarSmokes]

[Edited on 29-11-2009 by PolarSmokes]

watson.fawkes - 29-11-2009 at 13:54

Quote: Originally posted by PolarSmokes  
I know that nitrogen dioxide and water do disproportionate, so there will be some nitric oxide. However, it is a quite likely that nitric oxide would be more soluble in cooler water, versus warmer water, and may allow a larger portion of the nitric oxide to form nitrogen dioxide. However, without a peltier stack (stack of thermo-electric coolers), the nitrogen dioxide would not remain frozen.

My idea would not work with copper tubing if nitrogen dioxide DOES react with copper tubing.
Your thesis is that you can keep enough moisture out so that the lifetime of the copper is reasonable. I find this barely plausible, but with enough engineering effort it could be done. That's because with enough money you could attain the right states of matter, not because it would be easy to do so. So that's one question I've got about this idea, is whether or not it's feasible and/or economical (compared to other mechanisms). So if dissolution of the nitrogen oxides in water is the rate-limiting step, then you can assume that all the water present in the system is a catalyst for the reaction between nitrogen oxides and copper.

On the other hand, you're also making the assumption that the reaction in completely dry atmosphere has a low enough rate. This requires a whole separate kind of justification by experiment, be it yours or someone else's.

PolarSmokes - 29-11-2009 at 17:12

I might be confusing people by mixing my ideas up- the copper coil merely acts as a “near” “solidifier”, bringing the temperature within a few degrees of freezing for NO2/N2O4. After the exit, it will come into contact with a freezing unit, where N2O4 will solidify on the surface. After that, a solution of nitric acid (nitric acid to depress the freezing point, so the N2O4 may remain frozen within the HNO3), where it will disproportionate into NO + HNO3. The solution of nitric acid could be diluted after.

Thank you for pointing that out, even the smallest amount of moisture will increase the rate of corrosion, because 4 HNO3 + Cu → Cu(NO3)2 + 2NO2 + 2 H2O, so the rate of nitrate produced would accelerate as it proceeds down the tube. Longer sections of tubing could be used, though, even if they don't have the heat conductivity of copper. It would add up to quite a bit, though, as I had planned to use 100 ft. of copper tubing, which I thought was overkill, but using FEP would work for transferring the heat, just not as well, nor as cheap (as you have pointed out, watson). Other than that, there are really no problems. The Nitrogen Dioxide will still solidify, and the nitric acid will condense.

The main idea of this is to allow the NO2 and H2O to have sufficient time to react. Peltier units don't cost that much to buy, but I will admit that they do take a bit of money to operate, and to properly stack them. Actually, I hardly have enough power to use them all! A good stack would use about 1000 W, and I only have two power supplies good for that. All of the cooling would be about the same as the electric arc input! However, ALL of the NO2 will react with the water. But most of the NO will still be wasted.

tentacles - 30-11-2009 at 17:21

I've considered trying to make H2O4 in the winter (thermal decomp of nitrate salt) here, it can be -45C actual temp outside at night, no problem condensing the NO2. Alternative option would be to use the 12kV transformer I got this summer.

kclo4 - 30-11-2009 at 17:27

Quote: Originally posted by tentacles  
I've considered trying to make H2O4 in the winter (thermal decomp of nitrate salt) here, it can be -45C actual temp outside at night, no problem condensing the NO2. Alternative option would be to use the 12kV transformer I got this summer.

What is it you would do with the N2O4?

Also.. are you saying you are interested in making a reactor?

PolarSmokes - 30-11-2009 at 19:57

Because production of NO (which is the main stage) is thermally dependant, a Microwave Oven transformer would be much more likely to produce higher amounts of NO. A trigger would need to be used to ionize the air, so the microwave oven transformer would arc, and it would need to be initiated each cycle of the jacob's ladder.

A microwave oven transformer running unballasted will get hot, and require cooling. If it keeps flipping a breaker, it will need to be ballasted.

It will also be a lot more dangerous- a kilovolt or two, at about an amp. It is very dangerous.

PolarSmokes - 30-11-2009 at 20:02

and Kclo4, I'm guessing he would add it to water, to make nitric acid and nitric oxide, with the nitric acid being what he is after. I'm just taking clues from the context of the general idea of this thread! I could be wrong, though!

hissingnoise - 1-12-2009 at 02:03

Forget MOTs!
10kV NSTs are ideal for powering Jacob's Ladders. . .
And they don't run hot!

bbartlog - 1-12-2009 at 06:02

If you were going to use a microwave oven transformer, you'd be better off using it as part of the microwave it came with, and trying to generate a plasma within the microwave rather than electrical arcs directly.

Sedit - 1-12-2009 at 06:20

Do you know of any attempts at modifying a Microwave oven to make a Birkeland-Eyde reactor? This seems like it could be a pretty efficient means of producing given the large area of the plasma.

I have a question perhaps some can answer. When I use to play with HV alot one of the ways to tell the amount of power was to look at the spark. Its lenght gave alot of information of the Voltage present and its color gave info about its current. It was said that if the color was blue then that was from it fixing nitrogen in the air. Now I don't remember what exact numbers these where suppose to denote but wouldn't a blue spark instead of the hot yellow plasma yeild a higher concentration of NOx gas? I do know that I would encase the spark gap of my Tesla coil and only after a few seconds of running the who inside would be coated brown from Nitrogen oxides.

The Plasma can be increased in power by simply making a salt water capacitor from some old wine bottles.

PolarSmokes - 1-12-2009 at 10:42

the microwave oven plasma will burn through the glass in no time. I have used both a high current zvs flyback driver, as well as a 15 kv/60 mA transformer. None compare to the amount of Nitrogen Dioxide (estimated by rate of change of color) formation of a microwave oven transformer with it drawing about 3,000-4000 watts. This isn't fair, as the ZVS driver is pulling about 500 watts, and the NST, which is drawing 900 W.

Again, while using the microwave oven transformer, one of the main problems I have is a suitable container. The arc can get to over six inches long (unballasted), and actually longer than that, if you could "uncurl" it.

hissingnoise - 1-12-2009 at 12:41

In air, NO is formed at ~3000*C--- NO is fairly stable below 600*C but dissociates above this temperature.
Rapid cooling of the gasses is essential to minimise NO losses. . .
The area outside the arc plasma should be 'cool'!

kclo4 - 5-12-2009 at 12:23

Quote: Originally posted by PolarSmokes  
and Kclo4, I'm guessing he would add it to water, to make nitric acid and nitric oxide, with the nitric acid being what he is after. I'm just taking clues from the context of the general idea of this thread! I could be wrong, though!

But then there isn't any point in condensing it... is there?

12AX7 - 5-12-2009 at 12:31

Quote: Originally posted by Sedit  
Do you know of any attempts at modifying a Microwave oven to make a Birkeland-Eyde reactor? This seems like it could be a pretty efficient means of producing given the large area of the plasma.

Yes, a microwave horn would be ideal for powering the plasma. The downside is you might blow up a lot of magnetrons getting the SWR low enough.

I have a question perhaps some can answer. When I use to play with HV alot one of the ways to tell the amount of power was to look at the spark. Its lenght gave alot of information of the Voltage present and its color gave info about its current. It was said that if the color was blue then that was from it fixing nitrogen in the air. Now I don't remember what exact numbers these where suppose to denote but wouldn't a blue spark instead of the hot yellow plasma yeild a higher concentration of NOx gas?

No, blue is from oxygen. The oxidizing odor is from ozone, not NO2.

I do know that I would encase the spark gap of my Tesla coil and only after a few seconds of running the who inside would be coated brown from Nitrogen oxides.

Yes, the spark gap carries high current, so it has a heavy, thermal arc which burns the air, forming mixed products, NOx included. On the other hand, the blue to purple discharge from the secondary terminal mostly produces ozone (unless you draw arcs from it).


12332123 - 5-12-2009 at 17:57

If you powered such a reactor with microwaves, would you somehow need to 'seed' the plasma, to get it started, for example with a small electric arc? Isn't air fairly transparent to microwaves, after all you don't get spontaneous plasma formation in your microwave oven.

12AX7 - 5-12-2009 at 19:53

Yes. You need a special type of waveguide which concentrates the electric field, inducing breakdown. Otherwise, I'm sure you could, for instance, run plasma off a candle inside a regular oven.


PolarSmokes - 8-12-2009 at 05:02

Quote: Originally posted by kclo4  
Quote: Originally posted by PolarSmokes  
and Kclo4, I'm guessing he would add it to water, to make nitric acid and nitric oxide, with the nitric acid being what he is after. I'm just taking clues from the context of the general idea of this thread! I could be wrong, though!

But then there isn't any point in condensing it... is there?

Yes. The point is absorption from the water. When nitrogen dioxide is in the gas phase, it will leave the nitric acid by bubbling up because it is a gas. If it is condensed, it is allowed to react with water for a much longer time. it still dosn't help with H2O + 3NO2 --> NO + 2HNO3, but it will still allow the initial NO2 formed to be converted into NO2.

As the the microwave ideas, what are you guys planning to store them in? It will easily burn through the top of the glass. Or if you're using metal, the bulk of the power will be delivered to the container. As far as methods of ignition, if you want to be elaborate, you could probably get away with YAG induced blooming, as a "seed" for the plasma, without any wired contacts, however, a laser powerful enough to cause air to bloom will burn through glass.

I get my paycheck soon, and it's pretty cold outside, (which can be used to the advantage of my tec unit), so I might try to work out a setup that allows me to test MOT vs NST vs ZVS flyback driver, to see which one produces the most N2O, overall, and subsequently, nitric acid.

OR, I may get an oxygen compressor to hook up to my oxygen concentrator, simply because the concentrator costs too much to keep running for 1lpm, when I could fill a tank in a few hours, which would be able to provide 1 lpm for hours.... Are you guys using just air, or air and concentrated oxygen?

People working with the microwave induced plasmas, let me know how it is going!

tentacles - 9-12-2009 at 17:08

I'd also like to add - consider if you were to want 100% HNO3 - take 70% nitric (Easy to get) and put some N2O4 in it - not only will the 70% NOT be frozen at the appropriate temperatures, but production of (nearly) 100% nitric is almost trivial. White fuming 100% HNO3 it probably would not be, however.

Bikemaster - 29-3-2010 at 07:35

Just an other information, hope it help.

"Catalytic oxidation of NO to NO2 over activated carbons PAN-ACF, pitch-ACF and coconut-AC at room temperature (30°C) were studied to develop a method based on oxidative removal of NO from flue gases. For a dry gas, under the conditions of a gas space flow rate 1500 h−1 in the presence of oxygen of 2–20% in volume concentration, the activated coconut carbon with a surface area 1200 m2/g converted about 81–94% of NO with increasing oxygen concentration, the pitch based activated carbon fiber with a surface area 1000 m2/g about 44–75%, and the polyacrylonitriale-based activated carbon fiber with a surface area 1810 m2/g about 25–68%. The order of activity of the activated carbons was PAN-ACF<pitch-ACF<coconut-AC. However, NO conversion markedly decreased with the increases in temperature and humidity. For the dry gas, the apparent reaction rate was expressed by an equation: R=kcPNOPO2β (F/W), where β is 0.042, 0.16, 0.31 for the coconut-AC, the pitch-ACF and the PAN-ACF respectively, and kc is 0.94 at 30°C."

franklyn - 1-12-2010 at 05:22

related threads

The following is a source for papers on Plasma Chemistry some specific to the topic of
nitrogen dioxide , and others to ozone production. Many more applications are covered.

International Symposium on Plasma Chemistry - Digital Archive

When only abstract is given , Conference Full Papers are found here

Some excerpted papers are cited here , the later conferences have hundreds

Symposium 3

On Experimental Study of Nitric Oxides in Microwave Plasma


Symposium 4

See List of this Topic Heading - Specialized Session on Ozone Production


Symposium 5

Nitric Oxide Production in an Atmospheric Pressure Microwave Air Plasma

The Influence of Gas-Inlet & Quenching Systems on the Nitrogen Oxides
Production in Air Plasma

Also See - Session 6: OZONE SYNTHESIS


Symposium 6

Nitrogen Oxides Direct Synthesis in a Low Pressure Plasma Obtained From a
Microwave Discharge


Symposium 7

The Corona Discharge, Its Properties and Specific Uses

Symposium 9

High Power Glow Discharge for Chemical Synthesis


IrC - 8-12-2010 at 22:03

Do not know if anyone has read this page. Well worth a read. Nice work on both the pebble-bed plasma reactor system and the effort to determine concentration.

Mods, this thread deserves a sticky.

497 - 21-7-2011 at 07:27


Mods, this thread deserves a sticky.

So true!

I'm really impressed with how viable a microwave generated plasma system for synthesis of NO2/HNO3 looks.

Here's my dream design:

Use a standard air compressor to supply the reaction with ~100psi air. The energy cost of compressing the air is minimal, on the order of 20w/m^3/h of atmospheric pressure air compressed to 100psi. Of course the compressor itself is expensive, but many already have access to them for other purposes. And for small personal use amounts of HNO3, a very small cheap compressor would provide plenty of air.

The reactor would consist of one or more microwave oven magnetrons attached to the necessary waveguides which concentrate and focus the microwaves on a air inlet nozzle. The waveguide and reaction chamber design will no doubt require the most R&D for me. If anyone has references useful in the design of waveguides I'm sure many would appreciate them being posted.

Directly after the pressurized air stream has passed through the plasma it would be expanded through a simple converging-diverging venturi nozzle. Cooling water would be sucked into the nozzle to aid rapid cooling. Or it could be pumped in upstream of it, etc. According to various references, if the venturi is sized correctly cooling rates of over 10^7K/s are achievable. That means over 75% possibly up to 90% of the NO formed will remain undecomposed upon cooling. Hopefully the amount of cooling water added could be kept close to the amount needed to form your desired concentration of HNO3.

The freshly cooled expanded gasses would then be passed at a slow rate through a column of activated carbon to allow the reactions that form HNO3 to run to completion.

Based on the papers linked above and others, I calculated that one standard size magnetron should be able to yield at least 1kg of HNO3 per day. If cooling rates and wave guides can be optimized it could be even higher. At my power prices that comes to about $3.50/kg HNO3. The compressed air needed is minute, on the order of 0.1 CFM@100psi. Considering it should provide very high purity HNO3 and the system would require little attention and almost no materials would be consumed, I think it looks pretty damn good! Oh and it should be pretty easy to scale up :D

Besides making HNO3, I think the NO(2) produced could have many other interesting uses. Panclastites anyone? And oxidation to N2O5 looks extremely appealing too.
I can't begin to put into words how unhappy it makes me to realize I won't have a chance to try this out for quite a long time..

On a less related note, I found it interesting that running methane through a plasma then rapid quench process can achieve good yields of acetylene and hydrogen. I wonder what other fun things could be done with one?
Refs, refs, and more refs.

[Edited on 21-7-2011 by 497]

hissingnoise - 21-7-2011 at 07:46

I can't begin to put into words how unhappy it makes me to realize I won't have a chance to try this out for quite a long time..

The longer you wait, the better the appreciation you'll have of the dangers involved!

MrTechGuy1995 - 21-9-2011 at 15:51

My goal isn't to make views, but here is my terrible how to,
I will be updating this very soon as I get back more into chemistry.

497 - 5-8-2012 at 03:49

IMHO a critical problem with the Birkeland-Eyde is the low conversion of air, resulting in low concentrations of NO2 and problems with efficiently condensing/reacting the very dilute product.

This patent is a major step forward for small scale nitrogen fixation.

Silica gel in a ~1% NO2 atmosphere at 15C will hold 6.5% by weight NO2 at equilibrium. According to the patent, in practice ~4-5% is the concentration achieved with 5% loss of NO2 through the bed of 10-14 or 6-8 mesh silica gel. They say with a silica gel bed 3 feet high, and flow velocity of 100 ft/min, 100% of the NO2 is caught for 12min then efficiency drops off till it is catching 75% after 30min. They say at this point the silica gel is 75% saturated, which I assume means 4.8%NO2. Over the 30min a total of 5% of the NO2 is lost through the bed. If the granular fill factor is .4 (slightly fluidized) and the silica gel has 1ml/g pore volume, the silica gel loading would be 22kg/sq ft of bed, which corresponds well at 4.8% NO2 to the ~1kg of NO2 that would be carried by the corresponding 50 cubic meters of 1% NO2 (calculated as pure monomer) that flow over 30min. I think the patent was calculating the NO2 content based on the original NO% by volume.

In the process they use, three silica gel beds are alternated between, so that they have 30min to reach full capacity, 30min to extract the NO2, and 30min to cool down. 75% of the NO2 content as 98% pure gas is extracted at 165C, then 180C air is blown in to pull out the remaining 25% as a ~20% mix with air (which is made into HNO3). This way they would need 500-600kg of silica gel sorbent in the cycle to process their NO synthesis furnace output of 375mol/hr NO. Thus with 900 cubic meters of air, 27 kg hydrocarbon fuel (enough to use up 38% of the O2), they are able to get 12kg liquid N2O4, 6kg HNO3, and 250-300 kwh usable heat energy per hour. That comes to 68 kwh per kg of N fixed. This is better than the original Birkeland-Eyde process, and only about 2-3 times the current state of the art plasma 10^8K/s quench rate N fixation systems. When you take into account the efficiency of electrical generation/transmission, using fuel starts to look even more attractive.

For the very small scale experimental N fixing system, no doubt a plasma system would be simpler than a scaled down version of this patent. Not having to meter fuel/air, cool and dry exhaust gasses, etc would make the entire thing very simple. All you'd need is an air pump, an air drying tube, a plasma reactor run by TV or neon sign transformer, and a silica gel chamber. Once silica gel is near saturation, shut down the plasma reactor and use the NO2/silica gel as you please. It is safe convenient to store NO2 in silica gel. It can added directly to a reactant as a more mild nitrosating or oxidizing agent than liquid NO2. It can obviously be reclaimed as pure NO2 gas upon heating. I can't find any refs that mention NO2/silica gel + ozone, but interesting things may happen if you passed ozone through it (alone or submerged in solvent/reactant.) On a small scale cooling the gas lower is more convenient also, so using winter temps, salt+ice, or a freezer would allow slightly higher yields from the plasma reactor, and much higher NO2 capacity for the silica gel. At -10C the silica gel may well hold >30% NO2. When prepared by adding excess NO2 to silica gel in DCM at 0C can attain 45% NO2 content AFTER vacuuming off the solvent, and its stable at refrigerator temps for months. I'd try this as my plasma reactor:

I still think the combustion based system is exciting and worth exploring. If you wanted to make kg of NO2, where off grid, or had plentiful (possibly low grade) fuel and expensive electricity, it could be worthwhile. More experimentation required for sure. Personally, instead of using pebble bed heat exchangers to quench the >2000C flue gas, I'd try injecting water directly into a conventional high turbulence venturi burner. This is a known way to rapidly quench hot gasses, and may even improve the yield, while greatly simplifying everything. The NO in the flue gas reacts with O2 quite slowly at these concentrations, so only a <.5% of it is lost to the cooling water. Then dry the gas, run it over a small bed of NO2/silica gel to rapidly catalyze the reaction with O2, and then capture it in the main silica gel bed. Running batchwise would eliminate most of the complex automation in the patent. If you pre gasified your fuel in a crude updraft gasifier, any thing from waste plastic/paper to wood/coal could be used. Normally the vast tar production of updraft gasifiers makes them unusable, but if you directly burn the output before cooling that issue disappears.

In a cold climate you could easily be making >1 ton NO2/year while providing your household heat (and power?) for an extra 15-30% fuel consumption and 50-250kg silica gel. The colder it gets, the faster you produce NO2, but the colder you can cool the gas, and the more the silica gel will hold. Freezing brine tanks to "stock up" on cold during cold weather could allow the silica gel to be used at greater capacity for longer.

I'll gladly consult anyone looking to build one.

[Edited on 5-8-2012 by 497]

hissingnoise - 5-8-2012 at 15:24

An ozone generator with moisture-adjusted air feed producing NO<sub>2</sub> and enough O<sub>3</sub> to oxidise the NO<sub>3</sub> to the anhydride would do away with the need for absorbents and produce, in theory at least, any concentration of HNO<sub>3</sub>!

Natures Natrium - 24-9-2012 at 20:07

Just wanted to pop in here with a quick bit of info, as progress is slow. Recently spent some time thinking about and designing, and finally building my take on the concept of the Birkeland-Eyde reactor.

For reference, I used this thread, as well as numerous youtube videos and other websites. I also read "Absorption of Nitrous Gases" from the sci-mad library, front to back. Its actually quite a fascinating review, and I have found that I love texts from that period (1910s through 1930s). Other references of note are "The Electric Furnace" by John Norman Pring (starting at p.115); and "Industrial Nitrogen: the principles and methods of nitrogen fixation..." by Percival Henry Sydney Kempton (starting at p.13). Both are available on google books.

My first take was a failure, plan and simple. Insufficient volumes, inaccurate and unadjustable electrodes, etc. The second version appears to work, and has had two distinct runs.

First, a few brief descriptors of the device. I will go in to more detail should the device ever prove itself useful, but for now some generalizations should suffice.

I am utilizing a Jacob's Ladder style arrangement, with soft copper tubing 1/4" in diameter. The primary construction material is PVC pipe, which several references show as suitable for withstanding Nitric Acid in concentrations of less than 40% at STP. The material was useful due to the availability of a wide variety of sizes and shapes and the ease of construction, as well as its high resistance to electrical current.

The power supply for this was a 300W NST, which produces 10.5kV at 30mA. It is secondary ground fault protected. This power supply is probably quite underpowered for this purpose.

The device is operated under the low pressure and air current provided by a common aquarium air pump. The air is pumped directly into the arc from underneath to try and create a "flame-like" electric arc, which at 60hZ has visible break lines but still fills most of the space between the electrodes. This particular setup was decided upon after a failure to create a magnetically spread arc utilizing several large ferrous magnets, and the neodymium magnets more suited to the purpose were considered, for now at least, too expensive.

In the first trial, the device was run for 6 hours at 50% duty cycle with a frequency of one on/off cycle per ten minutes. Distilled water (500mL) was used as absorbent, followed by a container of 10% NaOH solution. Some nitrogen oxide smell was noted so the fume hood was used for this and all further tests.

The result is a solution which appeared, on titration with 1M NaOH solution, to contain 0.14% acid. I estimate the potential error in my measurements, based on titration of a known quantity of Acetic Acid (household 5%) to be as much as 10%. Thus I feel comfortable stating that the solution contained between 0.13 and 0.15% acid. Given these extremely low concentrations, I don't have any particular way of determining whether or not the acid is in fact HNO3.

For the second trail run, I changed several things. I used 500mL of commercial 3% H2O2 solution, the air flow was slightly reduced, the frequency of the on off cycle was changed to 30 minutes (after determining that the electrodes wouldn't get too hot to damage the pvc during a 15 minute run), and the air flow was allowed to continue during the off portion of the cycle, where previously it had been shut off concurrently with the arc.

This setup was ran for approx. 12 hours. Approximate because the digital timer used to run the first one died, probably from electrical feed back from the NST. A mechanical timer was used for the rest of this run.

Titration showed an acid concentration of 0.84%, which seems to be 2 to 3 times better than the previous run.

What I took away, given the continued prevalence of nitrogen oxide smell even post secondary hydroxide laden filtration, was the need for better absorption in the "main tower". While I would love to follow the authors advice in "Absorption of Nitrous Gases", I think I may have to stick with a loose packing such as broken glass or pumice. Pumping the absorbent to the top of the tower to counter-flow against the nitrogen oxides along even, symmetrical and high surface area packing proved to be a bit too much to construct.

If I had some serious glass working skills and an annealing oven, I have ideas and designs for a magnetically spread arc, pauling lift operated, positive pressure Birkeland-Eyde made out of all borosilicate. At least I can dream ambitiously. :P

hissingnoise - 25-9-2012 at 03:13


Natures Natrium - 25-9-2012 at 10:33

I am waiting until I have useable, practical results before posting a proper write up.

After the dismal failure of mk I, I was in a focused head space while constructing mk II and didn't think to document the process as I went. Nevertheless, I plan to take pictures of the current model should it prove useful, and I have several tips still in mind regarding its construction. If a total redesign is called for, then I will document the process of building the new one.

However, here is a picture of the current state of things.

proto.jpg - 112kB

hissingnoise - 25-9-2012 at 12:15

I used an old sweet jar (many, many moons ago); it was inverted so that aluminium electrodes and tubes could enter through the large bakelite screw cap.
Two NSTs in parallel drove the dischage and a 'fridgepressor the 'air' supply!
This, unfortunately introduced an oil-mist which coloured the acidic solution produced yellow!
The coloured impurity was a nitrated paraffin mixture . . .
Its presence indicated a loss of NO<sub>2</sub>!
A clean compressor would have given fairly pure acid.
The aluminium tubes were scavenged from an old freezer and they were used because pure Al is practically inert to dry NO<sub>2</sub>.
Aluminium electrodes were used for the same reason.
Epoxy glue was used as a sealant ─ it survived the harsh conditions for quite some time, but the seals needed renewing fairly regularly.
The effluent was led to continuously stirred water in a tall flask where absorption occurred . . .
Having the discharge occur behind glass is very convenient as the arc can be seen so that that electrodes may be adjusted to produce an optimum discharge.
Seeing the amber colouration intensify in the jar on start-up was interesting too.

Natures Natrium - 25-9-2012 at 13:15

I originally set up the electrodes inside an inverted glass tea jug (1 US gallon), to prove to myself that NO2 was in fact being created (it was). I also took some time to optimize the distance between the electrodes while under the influence of a flow of air. The electrode placement I am running with is set so that without the influence of air flow the arc will not climb the ladder (for consistently reliable arc formation), and under the influence of air flow the arc snaps at an average of 3/4 the way up the electrodes. I decided on this for two reasons, one being so that the plasma arc would be less likely to come into contact with the flammable PVC walls, and two so that the extra copper could act as a mass heat sink to slow the heating up of the electrodes.

I chose copper on the recommendation of "Absorption of Nitrous Gases", but also because it is easy to shape and is of course a good conductor of electricity and heat.

Just out of curiosity, what were the electrical ratings on your NSTs?

What I would like to do is run my set up 24/7 (15min on, 15min off) for the next two weeks. Unfortunately, due to the nature of the construction materials and my inability to constantly supervise it, I think that would be dangerously unwise.

[Edited on 25-9-2012 by Natures Natrium]

hissingnoise - 26-9-2012 at 05:02


I chose copper on the recommendation of "Absorption of Nitrous Gases", but also because it is easy to shape and is of course a good conductor of electricity and heat.

Just out of curiosity, what were the electrical ratings on your NSTs?

Hmmm. . . I'd worry that Cu would be attacked by NO<sub>2</sub>.
The NSTs, with centretaps at ~5kV had ~10kV outputs ─ current output long-forgotten . . .
Connecting in parallel increased arc temp and length!

Dave Angel - 28-9-2012 at 16:02

Quote: Originally posted by hissingnoise  
An ozone generator with moisture-adjusted air feed producing NO<sub>2</sub> and enough O<sub>3</sub> to oxidise the NO<sub>3</sub> to the anhydride would do away with the need for absorbents and produce, in theory at least, any concentration of HNO<sub>3</sub>!

I do not wish to derail this design exchange - hissingnoise's concept of producing anhydrous HNO3 got me thinking.

Regarding absorption of NO2, what if one were to run the output from a B-E reactor into a solution of hydrogen peroxide in a suitable organic solvent? Here's the envisioned reaction, does it seem reasonable?:

2NO2 + H2O2 -> 2HNO3

The following image shows the first page of an old JACS article (J. Am. Chem. Soc., 1916, 38 (3), pp 633-638) alluding to the solubilities of H2O2 in various organic solvents - work performed by mixing aqueous peroxide with the solvent:

Walton & Lewis.png - 251kB

Wikipedia suggests that mixing a suitable dry solvent with sodium percarbonate, would take the peroxide into solution, as others have noted in posts regarding sodium percarbonate. The reference wiki used (Tetrahedron Volume 51, Issue 22, 29 May 1995, Pages 6145–6166) would be handy and I'll track it down when I'm next at the library.

Now, of course we have the dreaded mix of organics and peroxide so selection of solvent would be critical, and not something within my experience, so this is very much an entertaining thought experiment rather than and experimental plan for me, but I felt it worth sharing.

The point is that the nitric acid formed is likely to be near anhydrous, and could be isolated by either evaporation of the solvent or freezing out with dry ice.

Any thoughts?

offset442 - 19-10-2012 at 13:35

I have been using one of these reactors to produce 40% HNO3 and nitrate salts for over a year now, works good have little problems with absorption, I have found absorption to be even efficient when no bubbler is employed,

My you tube video is here

I have produced about 10 liters of 40% and 2 kgm,s of salts, gave up on the ozone generator for lack of cheaply available materials that would stand up to it ie Teflon etc... (poly vinyl peroxide yuck) currently I have replaced the 2 neck flask with a 1 gallon glass wine jug and have about 1kg of lead reacting, conversion rate is good it will be completely converted in about 30 days pushing a 240 watt arc with no agitation.

I have to issue a warning, if making lead nitrate, pure lead is required, as any tin will make basic tin nitrate under these conditions, a sensitive high explosive' this material can be filtered away, but would be best not to deal with.

Would love to find ways of producing a better o zone source as it allows for direct nitrations and production of con hno3.

This setup goes a long way toward the production of anodes :-)

I find 40% acid to be a most convenient strength for general use, as well purity is at or above reagent grade dependant upon conditions

jimmyboy - 20-10-2012 at 00:14

At offset442: You should make a doc describing your setup - dimensions - air pump - power usage - time of reaction - yields etc - it looks very interesting and it would help others collaborate with you.

There was one more birkland generator using neodymium magnets for spreading the arc but looked a little slower at oxide production.

[Edited on 20-10-2012 by jimmyboy]

offset442 - 20-10-2012 at 07:43

That is the first attempt at a real B.E. reactor, as impressive as it appears this is not a very practical device, though is does appear to be producing fuming hno3, I have my doubts that this reactor is doing any better than mine as to acid concentration I think this setup is getting h2o from the air compressor as condensate. Also you notice the tungsten electrodes are coating the inside of the glass, likely with some sort of nitride, I get the same deposits from my iron electrodes in my Pauling arc chamber. This device represents an accomplishment however I would not trust it to run for almost 1 year straight with little supervision

Most notably the volume of acid it generates , it seems from the video that it could generate acid in the range of liters per day while my setup generates in liters per month, though I'm not saying that you couldn't use my rig, up scaled to an equal powered arc and get the same volume of production, Pauling had very good results with horn electrode furnaces made from bricks, with conversion effencies within a few % of birkeland

The main thing when designing a rig like mine is not to over power it without having a way to safely dissipate the heat of the arc, I feel my rig would fail if i went from 240 w to 450w the difference between 9kvac and 15 kvac even though my containment rig is made of Pyrex, asbestos, steel and cermanic tile. it uses automotive quark gasket and surgical vinyl tubing, in a wooden cabinet

For higher power levels, such as that of say a mot ,a steel cabinet is required, as well as stainless 316 ss tubing I would avoid using a organic materials for sealing, perhaps high temp fiber glass re enforced, silicone sheet often seen in automotive applications . I would also upscale the chamber siz. , perhaps getting rid of the pyres glass jar and going to a steel cylinder of some sort with a window installed.

That's it for not the wife calls :-)

hissingnoise - 20-10-2012 at 09:34

That's it for not the wife calls :-)

'Some nice stuff, o442 ─ you can, BTW, monitor operation of the arc on FM radio and your close neighbours probably can too . . .

And IMO, aluminium welding rods make ideal electrodes for a travelling arc!

offset442 - 21-10-2012 at 20:18

Actually I swear I can hear the arc manifest in the eddie current fluctuations in my ceiling fan, when up late at night unable to sleep. :-) I can clearly hear the arc starting, expanding and the small resonate kick from it breaking, this is where I feel some sort of soft switching supply with an uber dc line filter would be nice to have, I could not imagine the effect of a mot system on residential power, without such a device, perhaps soft switching microwave ovens will become more common in the near to not near future. I'm sure is would corrupt smart meter data points at the very least, which is agreeably a positive effect

My preference for1/4 inch steel round bar because the formations of ferrites actually have a small catalytic effect in breaking N2 (read harber) not to mention the electrodes can be easily welded to the heads of 1/2 inch bolts making for nice seal able lug connections. Also it is very advantageous for maintenance as the start gap can be adjusted with a few hits of the mig gun and then an carbide rotary bit.

My rig has been running for almost a year now, happily?? making me as much acid as I can use, mostly the lessons that I have learned, as most the concerns about absorption are impractical to consider on a lab scale , I simply vent the waste NO to the outside, and I can't even smell it where is comes out next to lab door unless it has reached 40% this is uasly the que I use to know when to change out the bottles.

Secondly over restricting the gas flow with bubblers has a negative effect allowing the n2o concentration to build to above 2% has resulted in delayed production, so gas flow should be such that the no2 concentration is maintained at about 50% of ultimate concentration judged colormetricaly against a bone white background as a practical means. As you have a setup running for a long time these little things become obvious.

Bubblers are made from cheap/poorly sintered/easily abraded, coarse grit alumna bench grinding wheel, with hole drilled with hss drill bit in the wet, very slow rpm high pressure, reshape bit as needed on bench grinder, use chisel then bench grinder to shape stone as well, stone is then glued to glass tube using clear PVC cement with 60 mesh screened crushed glass, apply cement, roll/sprinkle glass, air dry to tackey replete, cure at 50 C for 24 hours, coating shrinks, holds up well, untouched after 1 year.

STD 1 outlet aquarium air pump works good, one for deep aquariums might be better.

Final scavenger bottle needs to be twice the volume of 40% bottle.

To harvest empty 40% bottle, refill from scavenger bottle, then add di-water to scavenger bottle, scavenger bottle should not be allowed to proceed beyond 15%
Which is not a problem as long as its twice the volume of the absorption bottle.

I preference is to check concentration using a graduated cylinder calibrated with 200 grams of di-water, found graduation to be 7ml off off re marked 200 mil line:-) , weigh 200 ml acid divide weight by 200, then calculate density or just d/l a nitric acid density chart like I did print it out and post on cabinet door.

That's what I got enjoy :-) sorry form the typos my tablet is a pia to type on.

[Edited on 22-10-2012 by offset442]

[Edited on 22-10-2012 by offset442]

chucknorris - 15-11-2012 at 09:42


Im looking for a transformer for my reactor now. Im using two 500mm by 4mm tungsten electrodes, and looking for transformer that can deliver 10-20kV with 300-150mA (3kW max load). I will also look for smaller voltages with higher amperes.

[Edited on 15-11-2012 by chucknorris]

[Edited on 15-11-2012 by chucknorris]

up scaling

offset442 - 18-2-2013 at 22:03

"Im looking for a transformer for my reactor now. Im using two 500mm by 4mm tungsten electrodes, and looking for transformer that can deliver 10-20kV with 300-150mA (3kW max load). I will also look for smaller voltages with higher amperes."

IMO tungsten is a waste of time, its too small, and you cant weld it to anything, solid steel bar holds up for a long time and can dissipate more heat, as well when you use a minimum start gap, meaning the smallest gap you can set before the air pressure your using cant blow the arc to at least 80% of the total ladder height. you will indeed go very long periods of time between making gap adjustments

sounds like you have some problems to solve I highly recommend that you read this book before you proceed with such a large machine:

The Fixation Of Atmospheric Nitrogen (1914): Joseph Knox it is available in full freely on Google books

this book talks about most all of the methods used to produce nitric acid from arcs, at the turn on the 19th century this was very high tech, hard to do stuff, today with modern electronics, now days you can almost use 6-8 Mazilli ZVS flyback drivers running at 500 watts each from tv flabacks installed in a pool of heat sink cooled mineral oil to get 3kw and 10-20 kv. it merely comes down to the questions: how well can you weld and fabricate? Do you have all the required tools? can you do it without hurting yourself? all very important questions

for a mot scale design you will have to get very creative, you will need effectively get rid of 3kw of heat, you know thats how much the water heater in your house uses right? this means that you will need to use an old 50cuf oxygen cylinder to use as a nice bit large O.D. piping, a glass porthole of some sort to check the arc gap, sealed with red automotive silicone, and a nice pice of machinable ceramic or thick high temp thermo plastic such as kevlar or the like to use as a base, sealed with a high temperature silicone mat as a gasket with some sort of compression device using bolts to hold it closed. this covers your basic pauling furnace easy to build and efficient requires occasional tuning of the start gap (haven't had to re-tune mine yet) use 3/8 inch round bar and a ceramic base and you will have zero problems

the second option is to take an aluminum, titanium, molybdenum, niobium, zirconium (something nitric acid resistant, heat resistant, and NON-MAGNETIC sphere, ( probably have to gnd the sphere and wrap it in water fed copper tubing) and place an air cooled stainless ball in the center, on a ceramic isolator (cabinet knob) now surround the sphere with some intense electro magnets, use an arc starter to get the arc going over the relatively large gap, then blow air through the sphere until the arc quenches and dial it back a bit. You did remember to tangentially drill it right so it makes a vortex?

now vent air at a single port 90 degrees from the tangential plane, this no2 laden air needs to be vented through an all aluminum condenser such as the kind found in a freezer with a fan mounted to it such as that found on a car radiator, I know i keep saying aliuminum, i know its a bit crazy however can you afford a stainless heat exchanger? maybe alternatives to occasional scraping another refrigerator could be an Allan spiral condenser.

now onto your absorber i have found that calm surface area is almost as fast as bubbling so on this scale you are going to have 3 options really, trickle towers which require pumping and spraying the absorbent down a vertical section of pipe over perhaps some surface area generating medium say aquarium glass beads or marbles. another option bubble caps : see google or lastly horizontal pipes half full of water, your going to have to experiment with methods of absorption, just remember not to choke your air flow beyond the 50% mark.

I would say that 3 kw your going to be working with at least 4 liters of primary fluid and 15 liters of secondary fluid for god sake you need an air flow fail safe switch on this monster or at least put in its own steel traffic light NEC cabinet or shed away from your house and lab.

personally I would just build the Pauling horn electrode design its cheaper, faster, simpler and more reliable but not quite as cool

IrC - 6-4-2013 at 12:31

I think it is hard to beat a transformer from an oil furnace for long term reliability. On another note, did not have time to read all 11 pages to see if this patent has been mentioned. It seemed very interesting so I thought I should post it.

3081153 Automatic optimum air addition to nitric oxide absorption in nitric acid production

I include the link as it is often useful to study related patents.

Attachment: US3081153A.pdf (340kB)
This file has been downloaded 820 times

Skimming the thread I realize long ago neutrino asked me "why quartz", mentioning it's UV transparency. I never answered but it was merely a compromise since quartz would not melt so easily close to the arc. That was my reason, I knew UV would not be blocked but then again the chamber might survive longer with materials able to withstand high temperatures.

[Edited on 4-6-2013 by IrC]

hissingnoise - 7-4-2013 at 04:58

I think it is hard to beat a transformer from an oil furnace for long term reliability.

Not quite my experience, IrC ─ I lost one to overheating . . .
In a BE/Generator, the secondry is effectively shorted and a thermal cutout is essential for anyway long runs!

tinker Terry - 17-5-2013 at 22:21

Quote: Originally posted by axehandle  
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.

your website like doesn't work for me.

tinker Terry - 17-5-2013 at 22:26

Quote: Originally posted by axehandle  
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).


[Edited on 2004-2-12 by axehandle]

Maybe use a none conductive coolant oil? alchol?

Xenoid - 17-5-2013 at 23:18

Quote: Originally posted by tinker Terry  

your website like doesn't work for me.

Probably because that post is nearly 10 years old - :(

Blue Matter - 22-6-2013 at 12:33

Has anyone thought of using the magnets from a microwave magnetron to increase the size of the arc by creation a magnetic field. I think the magnets would be perfect if you put 2 on either side of a round container with the electrodes going threw the hole in the magnet. I am sure others have thought of more complex ways of creating the field but this seems like a simple solution. I am going to test this and get back to you on my results.

Pulverulescent - 23-6-2013 at 12:40

Has anyone thought of using the magnets from a microwave magnetron to increase the size of the arc by creation a magnetic field.

The travelling arc of a sealed-in Jacob's Ladder dissipates its heat (static arcs will cause overheating) throughout the reaction space ─ I used an old, tall glass sweet jar which became just hot to the touch on continuous working.

Blue Matter - 23-6-2013 at 15:08

Quote: Originally posted by Pulverulescent  
Has anyone thought of using the magnets from a microwave magnetron to increase the size of the arc by creation a magnetic field.

The travelling arc of a sealed-in Jacob's Ladder dissipates its heat (static arcs will cause overheating) throughout the reaction space ─ I used an old, tall glass sweet jar which became just hot to the touch on continuous working.

How is your reactor setup a cold water condenser or bubbling the gas through H202. What kind of concentration and production could I expect from a 12kv nst?

Marvin - 26-6-2013 at 04:27

Quote: Originally posted by Pulverulescent  

The travelling arc of a sealed-in Jacob's Ladder

The arc rises because the hot air rises. The arc is rising with the air rather than cutting through it.

scottjm - 1-7-2013 at 18:13

I looked through this thread, and I have a few questions. I saw on Wikipedia that the reactor run by Birkeland they were able to get a yield of 15 MWh/Ton of nitric acid. That may seem like a lot, but that is only 7.5 kwh per pound. 7.5 kwh at US national average that is $0.90. Have any of you been able to get this kind of efficiency?

What Kv would you recommend for this reaction? Some sources I read said as high as 31Kv, and some as low as 9Kv.
Would a platinum catalyst help with the second reaction (2 NO + O 2 → 2 NO)?

Blue Matter - 4-7-2013 at 13:19

Quote: Originally posted by scottjm  
I looked through this thread, and I have a few questions. I saw on Wikipedia that the reactor run by Birkeland they were able to get a yield of 15 MWh/Ton of nitric acid. That may seem like a lot, but that is only 7.5 kwh per pound. 7.5 kwh at US national average that is $0.90. Have any of you been able to get this kind of efficiency?

What Kv would you recommend for this reaction? Some sources I read said as high as 31Kv, and some as low as 9Kv.
Would a platinum catalyst help with the second reaction (2 NO + O 2 → 2 NO)?

I think best is like 12kv 300ma

scottjm - 4-7-2013 at 22:44

Quote: Originally posted by Blue Matter  
Quote: Originally posted by scottjm  
I looked through this thread, and I have a few questions. I saw on Wikipedia that the reactor run by Birkeland they were able to get a yield of 15 MWh/Ton of nitric acid. That may seem like a lot, but that is only 7.5 kwh per pound. 7.5 kwh at US national average that is $0.90. Have any of you been able to get this kind of efficiency?

What Kv would you recommend for this reaction? Some sources I read said as high as 31Kv, and some as low as 9Kv.
Would a platinum catalyst help with the second reaction (2 NO + O 2 → 2 NO)?

I think best is like 12kv 300ma

Thank you. Anybody else have any ideas, or know about using a catalyst for the NO to NO2 process?

Pulverulescent - 5-7-2013 at 01:36

NO is oxidised by O2 on contact ─ catalyst not required!

DetaDude - 13-9-2013 at 14:54

I know I'm a bit on the late side ........but has anyone tried OZONE, this stuff will oxidize just about anything.

Put ur 15KV transformer to work on a ozone generator and feed it pure oxygen.

Pulverulescent - 14-9-2013 at 01:41

Ozone has been used to oxidise NO2 in the gas-phase!
A cold trap (dry ice) was used to collect pure N2O5 product.
The oxidation in DCM solution was found to be more efficient, though!

langevin - 19-8-2014 at 09:44

Just some thoughts

Assuming an rotative tungsten electrode ( no need to drill or weld (hard to do) just clips or pinch it in the right angle). Speed must be determined.
Connection to the supply ( at this voltage) doesn't seems an issue
Assuming the other electrode could be the wall of the system. i e an outer cylinder (no need to be temperature resistant material due to the fact the sparks have low impact time (but repetitive).
Complete the system by two sealed sides ( may be glass) and flowing air through the apparatus. (could be two opposites holes in the outer cylinder).
Supply this system with an NST. 6 to 10 kV~
Sparks could be 1 inch long seeming an plasma ring.
Bubbling the exhaust gaz in water.
Concentrate the acid by distillation.

Note this trick (rotative electrode) is used in the Xray tubes ( at least for the high power ones) to reduce the temperature and increase the yield.

Does someone could comment theses thoughts?

Bert - 19-8-2014 at 11:05

Now THAT... Looks a PROPER bit of the old school mad science!

How large does such an installation have to be for good efficiency?

I have long thought that a rural photovoltaic or wind generator installation would be better used to make fixed Nitrogen than to generate electricity for network distribution, especially in light of transmission losses, infrastructure build out costs and the interupted production due to low wind or lack of sunlight.

If the process were reasonably efficient and interruption during periods of low wind/night time didn't destroy the equipment...

[Edited on 19-8-2014 by Bert]

Refinery - 5-9-2014 at 22:36

B-E is good that it needs only compressed air and electricity, but it has serious drawback on energy consumption. Do you guys think that converting ammonia to NO with Ostwald is that difficult? Technically it only needs to change the electric arc into a catalyst. Ammonia is freely available as long as urea is, so I see a winner in here.

haber-bosh + birkeland eyde

quantumcorespacealchemyst - 17-11-2014 at 17:59

langevin above mentions an interesting idea. i wonder about how that magnetic system in the video in the post by bert is set up also.

an idea i got from a forum poster on another thread,

using what jpsmith123 mentions (from thread linked below) about the arc being concentrated, the idea will involve

an air compressor into a quartz (very thick wall) vessel. this vessel is formed with pressure valves on the in and outlets and acts as the compression chamber (please tell me

where i may find find formulas for wall thickness pressure capacities of quartz and or borosilicate glass)

the gas/plasma is catalyzed by rhodium or rhodium/platinum which the electrodes are made of and/or powdered forms of those two metal/alloys as well (frit filters would be

needed i guess to keep them from exiting during purges)

while NO is oxidized by O2, the activations of pathways leading to NO may become lower, or it may do other unthought of stuff. the machine will probably need to be run in pulses

or with patterning run from a computer and is run with respect to pressure expansion, and has to take into account that/energy absorption. it will seemingly take good calculations

and tinkering. the catalyst when exited, also seems to add to the reactivity/pressure increase by further exiting the plasma. this gas when uncompressed

into water will seemingly cool it greatly and absorb well into it (perhaps to greatly, freezing it). the catalyst needs to be kept from depleting/contaminating the end product, although it may hopefully

be easily filtered. the electrodes themselves i guess are idealy the catalyst, arcing as jpsmith123 wrote. a plasmized catalyst may be interesting although it would mean

deteriorated electrodes and i that is why it is probably neccessary to run it in pulses. another possibilty but still probably idealy being run in pulses is to make the electrodes enter

the flask just at the edge of the microwave chamber so the liquid coolant may seep heat away from the electrodes fins which are on the outside of the shielding. the trouble here

may be that there is a waveguide effect that channels microwaves out of the faraday caging and along the electrodes. please tell me about the details of the radiation

behaviour here. i must mention that the electrodes will seemingly have to be tungsten with a thick coat of the catalyst so the uncoated part sticks [in/through]/[bonds to] the glass.

the post ideas come from from this thread

Quote: Originally posted by jpsmith123  
It seems that using microwaves to make nitric oxide may be the easiest and best way to go.

At first I wondered if there would be a problem with impedance matching, but based on information I've found, it looks like it may work quite well.

The following paper describes a plasma generator comprised of a 2.45 Ghz magnetron and a shorted waveguide with a triple stub tuner, that resulted in a reflected power of less than 1%; but even without the tuner, the reflected power was "typically less than 10%". That's good news.

More good news is that with an airflow rate of 28 lpm, plasma flame temperatures of over 6000 degrees kelvin were achieved...that should make lots of nitric oxide.

Finally, patent #6696662 describes a similar arrangement for creating a microwave plasma, only simpler in that it has neither a tuner nor the tapered waveguide section.

Quote: Originally posted by jpsmith123  
Actually it may be the other way around.

In the patent and the paper I cited, the microwave discharge is confined to a shorted waveguide; thus the electric field would be significantly higer and consequently the electron energy and temperature would be higher as well, theoretically resulting in more NO.

I would think you would want to flow the air through this hot zone.

Originally posted by Samosa
My friend stopped by today and we got to run a few more tests on the microwave. The big conclusion of the day is that reasonable yields will only be obtained from large reaction vessels--the higher the volume, the better. :P

attached is the pdf. from the internet archived site pdf. link

Attachment: 01JA005_full.pdf (307kB)
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while a catalyst is said to not be neccesary, i think it wil be fun to find out what it does anyway. also i wonder if a tesla coil arcing perpendicularly across the microwave gap arc

with an electrode pair of rhodium or rhodium/platinum will make it even more fun to mess with? i dont know if that will work as the arcs may go to the lower voltage potential and

fry the system unless it is designed to do funny things like that. i want to build this, please give me some ideas

i just realized that pressure will effect the equilibrium of the gases which makes this more interesting.

according to"

The most popular catalysts are based on iron promoted with K2O, CaO, SiO2, and Al2O3. The original Haber–Bosch reaction chambers used osmium as the catalyst. Haber

noted uranium was superior but harder to obtain."also "Some ammonia production utilizes ruthenium-based catalysts

(the KAAP process). Ruthenium forms more active catalysts that allows milder operating pressures."

essentially, this is combining haber-bosch and birkeland eyde

"Nitrogen (N2) is very unreactive because the molecules are held together by strong triple bonds. The Haber process relies on catalysts that accelerate the scission of this triple


[Edited on 18-11-2014 by quantumcorespacealchemyst]

[Edited on 18-11-2014 by quantumcorespacealchemyst]

WGTR - 17-11-2014 at 22:15

I think you might be mixing the Ostwald process with the Birkeland-Eyde process. :cool:

I'm currently working on this myself. For the Birkeland reactor, 5000V and 40A were common specifications for the reactor. About 200kW went into the arc. There was an inductor in series with the reactor, to provide current limiting once the arc initiated. The electrodes were 8-10mm apart. The 5000V was needed to help ensure that the arc re-struck every cycle. Once the air ionized in the gap, the voltage would drop very low, as the current would be limited by the inductor. The flame would get blown out into a disc by an electromagnet, since the arc current was AC. The arc would get blown to one side of the reactor, then when the polarity reversed, it would shift to the other side, forming a disc. When blown out to the outer edges of the reactor, the voltage in the arc would rise closer to the full 5000V, since the path was over 1m long. These furnaces were adjusted to allow the arc to extinguish itself precisely once it reached the outer edge of the reactor.

The impedance in the inductor in the original furnaces was relatively low. In the above example it would be no more than 125 ohms. With a 5000V NST rated at 0.5A (short circuit current), that figure is 10,000 ohms. Although the voltage in the NST is the same as the high power designs, the arc is much cooler because of the lower arc current. Because of this cooler arc, the arc voltage is higher. At the same time, I don't think that power is getting transferred very efficiently to the arc in these designs, and a lot of ozone gets produced.

High voltage is needed to initially strike the arc. Failing that, the electrodes can be briefly touched together. I experimented with sharpened 1/16" thoriated tungsten electrodes to see what it would take to get an arc going. Anything over 2A at 50 DCV worked. I could draw an arc to about 0.5cm, with 30V DC across the electrodes. I was getting about 60W in the arc. The tungsten was rapidly consumed under these conditions. The appearance of radioactive smoke wisping away from them bothered me somewhat, so I decided to try 1/8" copper bus wire instead. The results were about the same, although the flame was "greener". The positive electrode got hot enough to melt, the negative one just oxidized.

The Birkeland-Eyde reactor used water-cooled copper electrodes that were said to last for 300 hours before needing service. The long life must be related to the cooling that they received. I have some copper capillary tubing that I'll try with water cooling, and see how that works.

Based on the figures used in industry, the voltage should be scaled to ≈250V open circuit when using a ≈2A current limit. A high voltage (1,000-5,000) supply can be placed in parallel with the low voltage supply to maintain arc stability. At least these figures are a starting point.

[Edited on 11-18-2014 by WGTR]

j_sum1 - 17-11-2014 at 22:31

I have heard it said that hafnium is very resistant to damage in sparking situations.
You might want to look at the list of materials that are used in spark plugs for inspiration.

WGTR - 20-11-2014 at 21:28

Thanks for the pointers. I'm trying water-cooled copper capillary tubing right now, to see how that holds up. After all, that's how it worked in industry. The electrodes are holding up somewhat, but there are a few things that I need to adjust in the arc. I'm not spreading the arc far enough yet, and the current is being concentrated too much in certain areas of the electrodes. Aside from that, the water is keeping them cool. I'm using a DI water supply right now, with no recirculation (just runs down the sink). Water runs through the positive electrode, and exits through rubber tubing to the negative electrode. The water is not even warm as it exits.

As I ponder my previous post, I realized that I completely missed something obvious. In the original Birkeland-Eyde reactor design, the supply voltage was 5000VAC, at something like 40A. This is, of course, for a full sized reactor. The current limiting was provided by inductive ballast.

This inductive ballast causes the arc voltage to swing not only below, but above the supply voltage. Think of the arc as if it were a MOSFET in a flyback converter. When the FET is on (low arc voltage), the inductor charges up. When the FET turns off (arc blown out to the edge of the reactor), the inductor dumps its energy through the load resistance. If the load resistance is very high, then the voltage across the FET (arc voltage) can rise to very high levels, at least until the FET avalanches (arc voltage in this case may rise to 10's of thousand of volts). This is a weak analogy, and what is happening in the arc is more complicated than this, but it's the general idea.

Up until now I have been using a 150VDC supply that is current limited to 3A, and with 30 ohms of ballast resistance. Since there is a large output capacitor on the power supply, the voltage does not rise fast enough when the supply goes into current limit. Using the ballast resistor gives a much more stable arc for this reason. Arc spreading is accomplished with an electromagnet that is driven from 10-60Hz AC. The electromagnet core is ground to a point, like in the original reactors. Since I am using a ballast resistor, not an inductor, the arc voltage can never rise above 150V. Resistors don't store energy like inductors do.

The next order of business is to calculate what kind of ballast inductor that I need. It will be determined by load current, electromagnet frequency, and efficiency, among other things. Hopefully my 1cm diameter arc will spread to a 10cm arc with this modification.

Once I get certain issues ironed out, I'll probably start posting pictures.

sclarenonz - 27-12-2015 at 18:46

Will it work?

the titanium dioxide on carbon will take the hydrogen from the water ?

and the flyback can be placed in the magnetron ?

I saw that the magnetron has an input of 4000 volts, the flyback has in its output 30 000 volts, as there is no coil or electronic part within the magnetron believe he can mutiplicar this value?

please help me

g4719.png - 393kB

Diablo - 19-1-2016 at 07:05

I'm going to attempt to make nitric acid in a few months with a zvs driven flyback transformer.

Hawkguy - 2-2-2016 at 20:12

Made it. Two minutes will let it redden litmus paper.

[Edited on 3-2-2016 by Hawkguy]

12647868_656834514454939_446259719_n.jpg - 45kB

j_sum1 - 2-2-2016 at 21:15

Woot Hawkguy! That is some accomplishment!
Well done.

articles on dielectric barrier discharge

physics inclination - 8-8-2017 at 10:49

Hi I've found two neat articles that may be of interest to those designing plasma generators for both nitric acid and sulfuric acid. The articles focus on dielectric barrier discharge plasmas as they are supposedly more efficient and less hot than open-arc typical Birkeland-Eyde reactors.

edit: and the arc being less hot allows more generation of NOx without it dissociating and being destroyed from excessive heat.

Attachment: experimental.pdf (1.1MB)
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Attachment: SO2 removal from air with dielectric barrier discharges.pdf (1MB)
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[Edited on 8-8-2017 by physics inclination]

UkAmateur - 8-8-2017 at 13:03

Quote: Originally posted by axehandle  

"Besides, human lungs can take a lot more than one would think"

axehandle you are without doubt a fucking idiot.

Can you spell "humor" and "irony"?


Its very easy to get blase about NO2. Familiarity breeds complacency, particually when you havnt read the safety data.

You can breathe in NO2 and feel as if youve got away with it, normal, undamaged. Then 8 hours later, up to a day or two, you can drop dead of pulmonary edema. At lesser doses NO2 does largely unnoticed but long term damage to the rather fragile lung tissue. This is not simply caused by the acid NO2 forms as it dissolves with water, its a very reactive free radical - also why its paramagnetic and dark brown.

Well, I've read up on it now, after a very nice person warned me without calling me "a fucking idiot". Apparently it is much more dangerous than I previously thought. I know that now. I'm not senile yet.

You might want to save on you "fucking idiot"s's. People tend to stop reading what you write after you start the childish name-calling.



The thing about people that taste chemicals or test for high voltages with their fingers or hang around neer lit fuses, when everything goes fine people say 'hes, crazy' 'he must be insane' and then grin, and when things go wrong they say 'Oh shit, that was unlucky' or 'he shouldnt have done that' when what they really mean in both cases is 'what a fucking idiot'.

I don't test for high voltages with my fingers, nor do I use fuses at all. I always (fior my rocket engine tests) use electrical ignition with a very long cable hooked up to an apparatus with TWO safety switches.

Nor will I ever "taste test" nitric acid again. Have you heard about learning from one's mistakes?


While in the long run it makes no difference if you kill yourself or when, there will be a lot of other people reading this thread that will assume you know what you are talking about. If you adopt a lax attitude to NO2, they will assume this is acceptable. It isnt.

It's not my responsibility what other people think. And my "lax" attitude is part of my humor, which you obviously don't get. You must be a very boring person, OR there's something wrong with my humor.



Aparently high school physics is letting you down. An arc is a low conductivity path through the air, its low conductivity becuase its hot and (partially) ionised which the current maintains. Hot air rises becuase its less dense than the surrounding air and when it rises it pulls the arc with it since this is the path of least resistance. The arc is rising with the air, not through it. Trimming the ladder until the arc does not break solves a lot of problems, and combined with a static vertical magnetic field should increase yeild substantially (particually concentration in air making it easier to produce better nitric).

That's why the air is pumped in TANGENTIALLY, so that the arc will contact more (turbulent) air than if it where intruduced AXIALLY (w.r.t. the ladder).

I have already discarded, dumped, ditched a static arc, since it would require electrode cooling.


"I AM going to "recycle" some of the NO2 by feedback. "
No, dont do this, it would be bad.

Air passing into the arc comes out with a concentration of nitrogen oxides that does not depend on the amount going in. Its wasted NO2. Aditionally people seem to get better results if the air going into the arc chamber is dry.

Fine. Won't do it then. No problem. Actually, one less problem.


You might want to take heed from the death of a NST in jacobs ladder config particually.
"The company manufacturing this particular NST gave me their word that it would work in a jocob's ladder config."

Read the thread on roguesci. While it will certainly work, how long it will live is more the question. I came to the conclusion that the constant sparking might well be generating fast voltage spikes (eg from inductive kick) that degraded the insulation over time. Its also possible it simply overheated from the neer short current.

Time will tell.


"I'm not intending to make explosives. I'm very afraid of explosives. I AM, however, very interested in rocket fuels."

There is not so much of a difference. What fuel/oxidiser are you planning to make with the nitric acid?

There is a very large difference. Rocket fuels deflagrate, explosives detonate. I was planning on trying out NC to start with.


For the record, I do not have a 'problem' with your project. I hope it succeeds. You are quite entitled to tread your own path, make your own mistakes and we will learn from it either way. I will try to help, you can listen to my suggestions or not, if something is covered well elsewhere I do reserve the right to simply point you to it rather than type it all in myself. If you state as facts things I know to be wrong I do reserve the right to correct them and last but by no means least, if you tell people things are safe when they arnt, if you tell people something is doing less damage to them than they think - when you havnt read the information and very particually when it relates to NO2 - then I do reserve the right to call you a fucking idiot.

Everyone states as fact things that are wrong. It's the listeners responsibility to determine the truth of the statements. I could state that it's safe to jump out a window --- that does not make my fault if someone tries it.

And if you care to point out exactly <i>where</i> I've stated that NO2 is absolutely harmless, I'll accept the ad hominem title "fucking idiot". Mostly because sometimes I'm an idiot, everyone are, but also because I have a girlfriend, which means I'm occasionally fucking.

Does you hardware not support the concept of irony? And why are you so fond of the expression "fucking idiot"? Is there something Mr. Freud would find interesting here?

[Edited on 2004-2-24 by axehandle]

[Edited on 2004-2-24 by axehandle]

[Edited on 2004-2-24 by axehandle]

It's posts like this ^^^^ that really make a 'like' or 'rep' button a necessary addition to the forum soft ware in my most humble of opinion..

I don't want to waste bandwidth (and thus the site owners money)

So rather than quote a whole post.. Just to say I strongly agree with the posters opinion/sentiments..

A simple thumps up could suffice...

A constructive critism is all. Hope it doesn't over step the mark with me being new n all..


E2a I'm sorry but the quote in my box and the one appearing here are different?

If a mod can help? Or just delete? Many thanx.

[Edited on 8-8-2017 by UkAmateur]

clearly_not_atara - 8-8-2017 at 22:10

NO2 is a toxic gas. However, it is less toxic than chlorine or ozone, which are frequently recommended on this forum. According to this paper:

The odor threshold for NO2 is 0.12 ppm, and the PEL is 5 ppm with an IDLH of 20 ppm. Obviously you don't want to be pushing up against the IDLH and you need to use a respirator but it's not exactly nickel carbonyl, and the smell is an available warning that something is wrong. NO2 is infamous because it's easy to produce it inadvertently from common materials or when trying to do anything with nitric acid (particularly dissolving precious metals).

peculiar salt in residue

experimenter_ - 27-7-2019 at 13:48

Has anyone noticed a white salt left behind after evaporating all the nitric acid produced by the Birkeland-Eyde method?

This salt is white but it turns ammonium thiocyanate solution red! Seems like iron impurities but also other properties show it is not. If anyone is interested in further investigation what it could be, tell me to share more info.

FranzAnton - 23-4-2020 at 07:02

Dear Colleges, this is my first post and so pls. forgive me to "bore" you with a short introduction of myself. Come from central Europe and work in technical area in automotiv and chem is my hobby. I was behind this Birkland process for several years an so found your board with very interesting designs and approaches to that topic. So I decided to register and learn more from you.
With the high voltage jacobs ladder designs I ended up with too little success (too less hno3 production) per time so I stopped investigating. But recently I found some article about nox production in an cold plasma (dbd) discharge with some kind of dielectric that is also catalytic (tungsten oxides mixed with aluminium oxides)
Has anybody of you heared about that? This kind of design does not have electrode degradation and for the hv supply a flyback from an old b&w television ore something like this will do and the high frequency of some 10khz will also be helpful to increase the yield.

Loking forward to your comments
(and sorry for my English :D)

Attachment: TUe-Plasma.pdf (1.9MB)
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[Edited on 23-4-2020 by FranzAnton]

Alkoholvergiftung - 23-4-2020 at 13:43

Theoretical with under pressur sparkling you would have the gratest yield. Haber wrote abaut it around 1907. I ve read they had the same idea with the electicity from the wind mills in North Germany. Lower pressur sparkling should double the yield.

[Edited on 23-4-2020 by Alkoholvergiftung]

FranzAnton - 23-4-2020 at 23:37

I also read that, but at that time they had no idea about cold plasma physics.
Anyway I woud give the "old style" design another (last) chance, but with a different design regarding the arc unit.

High volatage unit DC which is charging a powerful capacitor which can reach 15kv. Replace Jcobs ladder to a normal 2 electrodes with fixed length spark gap which fires at 15kv. After each arc the cap can recharge until the next discharge. Powersupply an capacity I would design in that way that 10 arcs a second will be possible.
The electrodes placed in a narrow quarz tube (approx. 5--8mm inner diameter)
tig-Tungsten electrodes. The air will stream coaxial to the electrodes an will cool them and transport the reaction gases fast into cooler areas. Also the quarz tube has to be cooled outside with water (isolated double mantle)
The power supply is in that case more expensive (door nob capacitor) which can stand the high discharge currents.
I think this desing helps in faster cooling of the reaction gases which directly corresponds to higher NO yields.
With a given capacita, discharge voltage an frequency you can calculate the average power the high voltage system das to deliver, but a system below 500 watts limits the fun a lot :cool:

[Edited on 24-4-2020 by FranzAnton]

Alkoholvergiftung - 24-4-2020 at 01:53

It s only good when you have cheap electricity. I think an Transformer with 6kv max would be better. There is no Need for so much voltage. For the stove i think an mix of sand and gypsum would be an good Isolator and heat recistent. Cooling the gases obove the stove should Highend the yield too.

FranzAnton - 24-4-2020 at 03:37

lets forget the costs for electrizity for private project for a while. I need to have a better production rate and the NO production correlates with the volume of the discharge and this becomes grater with 15KV. But you are right several 6kV arks will do the same.
I will not stick to the 15kV. Depends on the material (transformer, caps. e.t.c) what I can utilize. But I consider the 15kV as a kind of max. voltage which I can handle without too much restrictions. Waht I also had in mind is, that the stored energy in a cap. rises with the square of the voltage. Further it's important to have a very short time of the arc (and that's depends of the capacity) so if you need extrme hot and short and energetic arcs you have to optimize that 3 parameter. Do you agree?

I forgot to mention an interesting detail that an extreme ultraviolett radiation generated by very hot arcs contributes also to the NO production.

So my opinion is that the jacobs ladder has a lot of limitations for higher production rates, but the advantage of it is the simple design. The original industrial scale Birkland-Eyde ofen generates 1% NO in the exhaust gas. The question is, if it is possible to reace 1-2% also in an donwscaled experiment like it can be done at home? I think for a much smaller apparatus a completely different arc design is necessary.
Do you speak german too (cause of your nickname) ;)

[Edited on 24-4-2020 by FranzAnton]

Alkoholvergiftung - 24-4-2020 at 12:41

Yes i speak german too. Is there not an Energy loss with 15kv because of radioaktivity? I ve read high voltages like in Thunder storms produce radioaktive reaktions.
They wrote that the Schönherr Stove had an eveciency of 5,5%.
They blew air from the Bottom of an pipe like stove i think one Elektrode was on the Bottom the other on the top with an arch lenght of over 1m. But you Need an lot of Compressed air.
You want to use Capicators like the Marx circuit?

[Edited on 24-4-2020 by Alkoholvergiftung]

FranzAnton - 24-4-2020 at 14:45

Radioactivity in that case is new for me. For 15kv I would not use a cascade. I would use a kind of flyback transformer loading that cap. But I am not clear now what exactly my next attempt will be. I found an interesting work about a GlidingArc reactor. Which basically is a kind of jacobs ladder in a flat surface design which looks very promising to me and which is driven by a normal 60Hz transformer with 5kV. The flat design helps a lot with cooling fast. I think the arc reactor itself is the cheap part, but the following oxidation part is the tricky thing where NO --> will becom NO2 if money is not so relevant (hehe) my idea would be to buils a "reactor not as a vessel as usual. I would use (pls. don't laugh) 200m PTFE tubing as a coil with 12 inc diameter where the exhaust NO gas and extra oxgen (or clean air) have time to react while constantly flowing in that 10mm inner diameter ptfe hose. 200m of that kind of tubing costs here 600$ ..thats a lot and have to be considered very carefully. The reactor design I have "stolen" in the web :D

GlideArc.PNG - 82kB

Alkoholvergiftung - 24-4-2020 at 22:52

The Ozone Generators from Amazon are an good source 6kv 100W.
If you work on small skale.
I would fill the bottle with claypott or brik pieces and moisten them.Pumic Stone should work too.You have an much higher survace erea.

For the Radioaktivity part.

15kv i think is the starting range for that Reaktion.

FranzAnton - 25-4-2020 at 00:50

Thank you for those interesting links. I did not know that and so learned something new. The 100W HV supply is too small for my needs. I am looking for a transformer in the range of 500 to 1000W. What do you think of the idea of the PTFE hose as a gas reactor?

Alkoholvergiftung - 25-4-2020 at 01:28

You have an lots of heat. I think it will melt. I would use the gyps sand mass in an Copper pipe as an chamber.Or Schamott.

MarkRob - 25-4-2020 at 06:32

Has anyone tried microwave plasma? It looks a bit tricky to do well - needs low pressure around 50millibar, which would make NO oxidation take many hours, so the NO product would need to be passed through the vacuum pump to an oxidation/absorption chamber at 1bar.
Also it looks like efficiency is quite a lot higher if the O2 content is around 35% or higher, but this could be achieved using an oxygen concentrator (but they have all be bought up due to coronavirus...)
One of the advantages of Birkeland-Eyde or microwave equivalent is lack of H2O contamination of the product, so it would be possible to freeze out pure N2O4 without contamination.
Interesting paper attached, they get 2.5 times the energy efficiency of Birkeland-Eyde without using any catalyst.
Of course, magnetron efficiencies are down around 60% or lower, so the actual efficiency gain is small, but the yield is quite high and there are no electrodes to wear out or contaminate the product.

Attachment: ajp-rphysap_1984_19_6_461_0-microwave-plasma.pdf (682kB)
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FranzAnton - 25-4-2020 at 10:37

hm that’s right, after the arc I have to put a glass tube with extra cooling to come down to 200 C which is good for PTFE.

For the concentrating the HNO3 I will test the following way:
HNO3 of round 50 to 60% is needed first this can solve a lot of NO2 gas. While solving it became deep dark green. If it’s saturated, I put the glass bottle in an pressure vessel and press pure oxigen 20 bar on that solution. So long until no more Oxigen is absorbed. It is possible to convert a diluted HNO3 saturated with NO2 in that way into a concentrated one.
A bit an effort it is to make that pressure vessel from stainless steel which can stand 30 to 40 bar (some extra for savety)

FranzAnton - 25-4-2020 at 10:55

to deal with magnetron for continuous max power is much more sophisticated and the yield can also be high with a normal arc design if you can manage to cool down the gases fast enough.
With the GlideArc design I will manage a fast cool down by a turbulent flow design. On the smallest point of the arc gap I will feed in the air with high pressure 18 bar from a fridge pump. To limit the air flow I use a glass capillary. So I get a very fast Air stream in the sparc gap. Because the arc gap is flat, I also can cool the quarz glass sides, so the faster the gases can be cooled down, the higher is the NO content.

Alkoholvergiftung - 25-4-2020 at 11:23

30 to 40 bar is an very high pressure. Somewhere here wrote someone Silicagel can absorb 70% NO gas. May be it s usefull you can heat it later and the Temperature is lower so ist more stabel.

FranzAnton - 26-4-2020 at 03:01

silicagel will only help in concentrating NO2. I described to solve. NO2 in HNO3 then with the oxygen pressure you can convert the NO2 with the rest of water in the HNO3 into HNO3 so it will be concentrated by this way.

Belowzero - 4-6-2021 at 13:19

I made a video about my birkeland eyde reactor, or Pauling reactor.
It's a work in progress, intended as more than just a POC.

The primary part of it seems to work well at this point, I am still playing with some ideas inspired by long forgotten patents but for now this is not where the focus lies.
The next challenge is to build an efficient scrubber, perhaps using a spraying device of sorts as is used by several industrial processes.
If I can get something that is capable of running for days on end I might buy a few second hand solar panels to see if I can run it on those, nitric acid from air,water and sunlight is the final goal here.

Any feedback is appreciated :)

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